- cctbxbb - phenix-online.org

compiler warning in dxtbx
by Oleg Dolomanov 04 Nov '13

04 Nov '13

Hi guys, there was big change in dxtbx/model/panel.h on the 30th of October (r18499) and apparently the != operator became recursive by calling itself rather than the == operator (line 378) - whoever is responsible - please check/fix, Cheers, Oleg.

3 8

Request for a fix in CC1/2 calculation in phenix.merging_statistics
by Keitaro Yamashita 28 Oct '13

28 Oct '13

Dear CCTBX developers, I found a big difference in CC1/2 value (say, 77.3 vs 68.3) between phenix.merging_statistics and XSCALE when more than one *anomalous* dataset was merged in XSCALE. phenix.merging_statistics seems to assume that equivalent (in case of anomalous, here I do not consider Friedel pairs as equivalent) reflections are sorted (equivalent reflections are not separeted) in the input file. Usually, this assumption should be correct. However, if multiple anomalous datasets were merged in XSCALE, this assumption is not correct. Because Friedel pairs are not necessarily separated. This is a real example (in P43212). These lines are extracted from .HKL file by XSCALE: > 1 -41 1 1.749E+04 1.657E+05 2052.0 2467.7 78.8 -113.23 1 > 41 -1 -1 4.569E+03 6.014E+03 454.1 1112.8 132.2 116.90 1 > 41 1 -1 8.721E+03 2.637E+03 473.0 1064.4 130.4 116.11 2 > 41 1 1 7.634E+03 2.417E+03 498.2 1010.8 135.3 115.65 2 > -1 -41 -1 4.847E+03 1.997E+03 1892.9 2543.0 85.9 -122.78 2 The last number indicates the dataset the reflection belongs to. Here, (1 -41 1), (41 -1 -1), (41, 1, 1), and (-1, -41, -1) are equivalent reflections, but (41, 1, -1) in the middle is not when anomalous data! Therefore, in phenix.merging_statistics, subsets calculation for (41,1,1) is performed twice (for first two and last two). When I changed the cctbx code to sort reflections after mapping to a.s.u., CC1/2 values by phenix.merging_statistics became closer to XSCALE. In merging_stats.__init__() in iotbx/merging_statistics.py, I inserted a line > array = array.sort("packed_indices") after > array = array.customized_copy(anomalous_flag=anomalous).map_to_asu() but I think there would be more correct way to fix this unexpected behavior. Best regards, Keitaro

2 3

correlation function for cctbx.miller.array
by Gabor Bunkoczi 24 Oct '13

24 Oct '13

Hi, I need to calculate the correlation function between two maps, both of them are stored as miller.array objects. There is a map_correlation method, which does something similar to what I want, but this calculates the total correlation coefficient, while what I need is another miller.array with amplitudes = f1*f2 and phases = p2-p1 (where f1, f2 are amplitudes and p1, p2 are phases of map1 and map2, respectively), i.e. not just the sum of these. Is this available somewhere? There is the additional complication that the hkl-list for map1 and map2 may not be fully identical, but the intersect of the two maps could be taken. Thanks, Gabor

2 5

Scipy / cctbx core dump
by Graeme.Winter＠diamond.ac.uk 15 Oct '13

15 Oct '13

Hi Folks, Just trying to use something here which depends on scipy but it seems scipy is not playing nice with flex: from scitbx.array_family import flex import scipy.linalg A tiny and inoffensive script however... cctbx.python boom.py show_stack(1): /home/gw56/svn/cctbx_base_15oct13/cctbx_plus_build/base/lib/python2.7/site-packages/scipy/linalg/blas.py(113) <module> show_stack(2): /home/gw56/svn/cctbx_base_15oct13/cctbx_plus_build/base/lib/python2.7/site-packages/scipy/linalg/misc.py(5) <module> show_stack(3): /home/gw56/svn/cctbx_base_15oct13/cctbx_plus_build/base/lib/python2.7/site-packages/scipy/linalg/__init__.py(147) <module> show_stack(4): /scratch/gw56/2013/OCT/15/multi-lattice/boom/boom.py(2) <module> libc backtrace (2 frames, most recent call last): /home/gw56/svn/cctbx_base_15oct13/cctbx_plus_build/base/lib/python2.7/site-packages/numpy/core/multiarray.so(PyArray_API+0) [0x7fb2064c9940] /lib64/libc.so.6() [0x37b3232920] Segmentation fault (Python and libc call stacks above) This crash may be due to a problem in any imported Python module, including modules which are not part of the cctbx project. To disable the traps leading to this message, define these environment variables (e.g. assign the value 1): BOOST_ADAPTBX_FPE_DEFAULT BOOST_ADAPTBX_SIGNALS_DEFAULT This will NOT solve the problem, just mask it, but may allow you to proceed in case it is not critical. I did a fresh nightly build install just to be sure :o( if I export those naughty env vars I get a core dump: cctbx.python boom.py Segmentation fault (core dumped) RHEL6.4 / scipy 0.12.0 and 0.12.1 any ideas? Thanks, Graeme Dr. Graeme Winter Senior Software Scientist Diamond Light Source +44 1235 778091 (work) +44 7786 662784 (work mobile) -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

2 1

Model based outlier calculation in mmtbx.scaling.outlier_rejection
by Keitaro Yamashita 08 Sep '13

08 Sep '13

Dear cctbx developers, I am interested in the implementation of model-based reflection outlier rejection. As I read the code mmtbx/scaling/outlier_rejection.py (lines 244-351), I noticed that maybe there was a discrepancy between what log_message explained and the actual code. The log_message in the code says: > Outliers are rejected on the basis of the assumption that a scaled > log likelihood differnce 2(log[P(Fobs)]-log[P(Fmode)])/Q\" is distributed > according to a Chi-square distribution (Q\" is equal to the second > derivative of the log likelihood function of the mode of the > distribution). > The outlier threshold of the p-value relates to the p-value of the > extreme value distribution of the chi-square distribution. while actual p_value is calculated for each hkl as p_value = 1 - erf(sqrt(LLG))**N, where LLG = log p(F=Fbar | Fmodel) - log p(F=Fobs | Fmodel), and N is the number of reflections. Here, Fbar is F which gives the maximum value of p(F | Fmodel). At least, Q (the second derivative of p(F=Fbar | Fmodel)) is not used in the actual calculation. Could someone please explain the meaning of the actual calculation? Why taking square-root and raising erf() result to the power of N? Thank you very much, Keitaro

4 4

map_to_asu - get the symop used to perform mapping
by Graeme.Winter＠diamond.ac.uk 24 Jun '13

24 Jun '13

Hi All, In the progress of trying to (for reasons of my own) reproduce scale pack unmerged format files from flex arrays of Miller indices. map_to_asu is great, but it would be great to get the symop # used to perform the mapping as a result of this (it is computed somewhere in asu.h but not easily pushed out…) Has anyone done this already? I mean the getting-of-symop-which-maps bit... Thanks, Graeme -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

2 3

build problem on ubuntu 12.04
by Alastair Fyfe 11 Jun '13

11 Jun '13

Hello, is the current cctbx build (2013_02_27_0005) known to be buildable on Ubuntu ? I tried "perl cctbx_bundle.selfx" without success. After some poking about I found an exception raised in the platform.architecture() call in env_config.py/is_64bit_architecture(). Modifying the function to simply return False allowed the build to complete (log attached).This is on 12.04 with stock python 2.7.3 and the "platform.architecture()" call works as expected in a simple test. thanks, Alastair

4 8

updated project docs
by Nathaniel Echols 05 Jun '13

05 Jun '13

FYI, I finally updated the online documentation for the first time since switching the project backend. Included in this is the corrected link for the SVN browser, which for the record is now: http://sourceforge.net/p/cctbx/code/HEAD/tree/trunk/ (I find this somewhat over-engineered, but the old URL only shows the frozen repository as of early March, so we don't have a choice.) If anyone notices broken stuff, please let me know. -Nat

2 1

Re: [cctbxbb] building sphinx documentation
by Jan Marten Simons 19 Apr '13

19 Apr '13

Am Donnerstag 18 April 2013 19:16:00 schrieben Sie: > Hi Jan, Hi Richard, > I have attempted to build the sphinx documentation using > dox.sphinx/build_docs.sh, and this appears to have run successfully and > produced some html which shows the table of contents etc. However, I can't > seem to find the documentation for any of the significant modules, e.g. > cctbx/xray/structure.py. When I navigate to the link for the structure > module within the xray package > (dox.sphinx/_build/html/cctbx/cctbx.xray.html#structure-module), I see > nothing other than a list of all the modules within the xray package. Am I > missing something here? Have you followed the instructions given in the comments at the top of dox.sphinx/build_docs.sh? Which version of Sphinx do you use? I'm using 1.1.3 regularly and get useful documentation (I've attached the "makescript" I use to build cctbx and the sphinx documentation. If you are interested in it I can also put the output of the sphinx run on my system with current svn on webserver over here.). Has your sphinx build completed successfully or did it abort (e.g. due to out of memory* or due to other problems)? Could you also check if build/dox.sphinx/cctbx/cctbx.xray.rst has all modules listed? > As a novice to using sphinx, I don't like to add significant documentation > in sphinx style without being able to check via generating the > documentation that what I have written is correct sphinx-speak. I can totally understand this ;). Cheers and hopefully we can get this working for you as well, Jan *) For me running sphinx with all those modules selected needs about 3.3 GiB of virtual memory (RAM) and takes a few minutes to actually finish. p.s.: Sorry didn't hit "reply all".

3 6

Finding neighbouring atoms using pair_asu_table
by Lukas Reck 19 Apr '13

19 Apr '13

Dear all, please forgive me if the following is trivial or if I've overlooked something simple, I'm new to cctbx. I'm trying to use the cctbx python libraries to read in a large number of crystal structures and extract some geometric information on the coordination environment of certain atom types in them. I've been following the instructions from the 8/2004 CompComm Newsletter No. 4 at <http://www.iucr.org/__data/assets/pdf_file/0003/6384/iucrcompcomm_aug2004.p…>, pages 22-28 (is that still up to date?) but I cannot seem to get at the correct symmetry elements for each neighbouring atom in the coordination environment of some atom of interest. As far as I understand, the following should be correct: assert(isinstance(structure, cctbx.xray.structure)) # yes, it is a structure asu_mappings = structure.asu_mappings(buffer_thickness = 3) # create the ASU mappings pair_asu_table = cctbx.crystal.pair_asu_table(asu_mappings = asu_mappings) pair_asu_table.add_all_pairs(distance_cutoff = 3) # create the pair ASU table raw_mappings = asu_mappings.mappings() raw_pair_table = pair_asu_table.table() # access to the raw structures for scatterer_index, scatterer in enumerate(structure.scatterers()): # iterate over all atoms in the structure label = scatterer.element_symbol() if label == atom_of_interest: # we are only interested in one atom type for j_seq, j_syms in raw_pair_table[scatterer_index].items(): # j_seq is the neighbouring scatterer's index, j_sym is a list of lists of symmetry indices for sym_group in j_syms: for j_sym in sym_group: # j_sym is an index into raw_mappings[j_seq] print "j_seq:", j_seq, "j_sym:", j_sym print "i_sym_op:", raw_mappings[j_seq][j_sym].i_sym_op() symmetry = asu_mappings.get_rt_mx(j_seq, j_sym) print "%s at %s" % (scatterer.element_symbol(), scatterer.site) print "Neighbour: %s at %s" % (structure.scatterers()[j_seq].element_symbol(), structure.scatterers()[j_seq].site) print "To be transformed by %s (symmetry #%s)" % (symmetry, j_sym) print "into %s" % (symmetry(structure.scatterers()[j_seq].site),) Here's a sample output for one pair of neighbouring atoms: j_seq: 10 j_sym: 1 i_sym_op: 10 V at (0.30204, 0.52919, 0.5) Neighbour: O at (0.36242, 0.49166, 0.5) To be transformed by y-1/2,-x+1/2,z-1/2 (symmetry #1) into (-0.00834, 0.13758, 0.0) As you can see from the coordinates, the neighbouring atom was correctly identified, but the corresponding symmetry as returned by get_rt_mx transforms it into a symmetry equivalent that is very far away. Clearly I misunderstand the function of one or more of the various indices here, but I am not quite clear on where my error lies... Thanks for any pointers! Best regards Lukas Reck -- School of Chemistry Faculty of Engineering, Mathematics and Science Trinity College Dublin Dublin 2 Tel: (+353) 1 896 3452

2 3

building sphinx documentation
by Richard Gildea 19 Apr '13

19 Apr '13

Hi Jan, I have attempted to build the sphinx documentation using dox.sphinx/build_docs.sh, and this appears to have run successfully and produced some html which shows the table of contents etc. However, I can't seem to find the documentation for any of the significant modules, e.g. cctbx/xray/structure.py. When I navigate to the link for the structure module within the xray package (dox.sphinx/_build/html/cctbx/cctbx.xray.html#structure-module), I see nothing other than a list of all the modules within the xray package. Am I missing something here? As a novice to using sphinx, I don't like to add significant documentation in sphinx style without being able to check via generating the documentation that what I have written is correct sphinx-speak. Cheers, Richard

3 2

First svn commit
by James Stroud 18 Apr '13

18 Apr '13

Hello All, Since this is my first commit, I just want to make sure that I have done these things in the appropriate way. Here's what I did: 1. Added a wiki page: https://sourceforge.net/p/cctbx/wiki/Subversion%20set%20up/ 2. Added the method as_miller_arrays_map() to iotbx_mtz_ext.object, which is declared in iotbx/mtz/__init__.py. 3. Added a test for this functionality in the file iotbx/mtz/tst_miller_map.py Please let me know if the manner in which I did anything could use improvement. James

6 6

Euro SciPy
by Graeme.Winter＠diamond.ac.uk 17 Apr '13

17 Apr '13

Hi Folks, Anyone going to this meeting? https://www.euroscipy.org/ Some of the scientific software team here at Diamond have a habit of going to this meeting and remarked that a contribution on CCTBX may be appropriate... (see below for meeting topics) Best wishes, Graeme Topics * Presentations of scientific tools and libraries using the Python language, including but not limited to: * Vector and array manipulation * Parallel computing * Scientific visualization * Scientific data flow and persistence * Algorithms implemented or exposed in Python * Web applications and portals for science and engineering- * Reports on the use of Python in scientific achievements or ongoing projects. * General-purpose Python tools that can be of special interest to the scientific community. -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

1 0

structure.replace_sites_... vs. structure.set_sites_...
by Jan Marten Simons 16 Apr '13

16 Apr '13

Hi, while working on a really fast way to calculate the structure factors of a few millions of different modifications of a structure with only the selected scatterers contributing to f_calc I came across this: Why are there two methods for changing the sites_(cart/frac) of the scatterers doing quite different things? set_sites_... seems to simply update the corresponding site information of the scatterer, while replace_sites_... seems to create a copy of the structure. Is this the only difference there is? Also If anybody got a nice idea for my original problem, I'm also very much interested. (I think building a larger structure and working with selections might be faster than creating lots of different structures containing only the desired scatterers, but I might be wrong on this.) Cheers, Jan

3 4

pyyaml - iotbx.pdb incompatibility
by James Stroud 16 Apr '13

16 Apr '13

Hello All, There is a strange incompatibility between pyyaml and iotbx.pdb that depends on the order of import. If yaml is imported first, there is no problem. If iotbx.pdb is imported first, then importing yaml crashes. This is the yaml that comes with enthought python, but I don't think it's using libyaml, which is the C implementation. So the yaml, from what I can tell, is pure python. I'm wondering if anyone else can reproduce this error. James chernev 185% cctbx.python Enthought Python Distribution -- www.enthought.com Version: 7.3-2 (64-bit) Python 2.7.3 |EPD 7.3-2 (64-bit)| (default, Apr 12 2012, 11:14:05) [GCC 4.0.1 (Apple Inc. build 5493)] on darwin Type "credits", "demo" or "enthought" for more information. py> import yaml py> from iotbx import pdb py> raise SystemExit() chernev 186% cctbx.python Enthought Python Distribution -- www.enthought.com Version: 7.3-2 (64-bit) Python 2.7.3 |EPD 7.3-2 (64-bit)| (default, Apr 12 2012, 11:14:05) [GCC 4.0.1 (Apple Inc. build 5493)] on darwin Type "credits", "demo" or "enthought" for more information. py> from iotbx import pdb py> import yaml show_stack(1): /Library/Frameworks/EPD64.framework/Versions/7.3/lib/python2.7/site-packages/yaml/constructor.py(256) SafeConstructor show_stack(2): /Library/Frameworks/EPD64.framework/Versions/7.3/lib/python2.7/site-packages/yaml/constructor.py(161) <module> show_stack(3): /Library/Frameworks/EPD64.framework/Versions/7.3/lib/python2.7/site-packages/yaml/loader.py(8) <module> show_stack(4): /Library/Frameworks/EPD64.framework/Versions/7.3/lib/python2.7/site-packages/yaml/__init__.py(8) <module> show_stack(5): <stdin>(1) <module> libc backtrace (49 frames, most recent call last): 50 python2.7 0x0000000100000f54 start + 52 49 Python 0x0000000100108576 Py_Main + 3318 48 Python 0x00000001000f2c6e PyRun_AnyFileExFlags + 126 47 Python 0x00000001000f2b2e PyRun_InteractiveLoopFlags + 78 46 Python 0x00000001000f28eb PyRun_InteractiveOneFlags + 379 45 Python 0x00000001000cd2c6 PyEval_EvalCode + 54 44 Python 0x00000001000ccfc5 PyEval_EvalCodeEx + 1733 43 Python 0x00000001000c77fe PyEval_EvalFrameEx + 9502 42 Python 0x00000001000c4267 PyEval_CallObjectWithKeywords + 87 41 Python 0x000000010000d052 PyObject_Call + 98 40 Python 0x00000001000be823 builtin___import__ + 131 39 Python 0x00000001000e5cf8 PyImport_ImportModuleLevel + 344 38 Python 0x00000001000e536a load_next + 234 37 Python 0x00000001000e511a import_submodule + 314 36 Python 0x00000001000e4f59 load_package + 409 35 Python 0x00000001000e4632 load_source_module + 466 34 Python 0x00000001000e3981 PyImport_ExecCodeModuleEx + 209 33 Python 0x00000001000cd2c6 PyEval_EvalCode + 54 32 Python 0x00000001000ccfc5 PyEval_EvalCodeEx + 1733 31 Python 0x00000001000c77fe PyEval_EvalFrameEx + 9502 30 Python 0x00000001000c4267 PyEval_CallObjectWithKeywords + 87 29 Python 0x000000010000d052 PyObject_Call + 98 28 Python 0x00000001000be823 builtin___import__ + 131 27 Python 0x00000001000e5cf8 PyImport_ImportModuleLevel + 344 26 Python 0x00000001000e536a load_next + 234 25 Python 0x00000001000e511a import_submodule + 314 24 Python 0x00000001000e4632 load_source_module + 466 23 Python 0x00000001000e3981 PyImport_ExecCodeModuleEx + 209 22 Python 0x00000001000cd2c6 PyEval_EvalCode + 54 21 Python 0x00000001000ccfc5 PyEval_EvalCodeEx + 1733 20 Python 0x00000001000c77fe PyEval_EvalFrameEx + 9502 19 Python 0x00000001000c4267 PyEval_CallObjectWithKeywords + 87 18 Python 0x000000010000d052 PyObject_Call + 98 17 Python 0x00000001000be823 builtin___import__ + 131 16 Python 0x00000001000e5cf8 PyImport_ImportModuleLevel + 344 15 Python 0x00000001000e536a load_next + 234 14 Python 0x00000001000e511a import_submodule + 314 13 Python 0x00000001000e4632 load_source_module + 466 12 Python 0x00000001000e3981 PyImport_ExecCodeModuleEx + 209 11 Python 0x00000001000cd2c6 PyEval_EvalCode + 54 10 Python 0x00000001000ccfc5 PyEval_EvalCodeEx + 1733 9 Python 0x00000001000cb0e6 PyEval_EvalFrameEx + 24070 8 Python 0x00000001000ccfc5 PyEval_EvalCodeEx + 1733 7 Python 0x00000001000c7ea0 PyEval_EvalFrameEx + 11200 6 Python 0x0000000100010af8 PyNumber_Multiply + 40 5 Python 0x000000010000c569 binary_op1 + 137 4 ??? 0x0000000000000aa9 0x0 + 2729 3 libsystem_c.dylib 0x00007fff84b0ccfa _sigtramp + 26 2 boost_python_meta_ext.so 0x00000001007013c0 initboost_python_meta_ext + 0 Floating-point error (Python and libc call stacks above) This crash may be due to a problem in any imported Python module, including modules which are not part of the cctbx project. To disable the traps leading to this message, define these environment variables (e.g. assign the value 1): BOOST_ADAPTBX_FPE_DEFAULT BOOST_ADAPTBX_SIGNALS_DEFAULT This will NOT solve the problem, just mask it, but may allow you to proceed in case it is not critical. -- James Stroud Affiliate Howard Hughes Medical Institute UCLA-DOE Institute for Genomics and Proteomics

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Flex array slice assignment work-alike
by James Stroud 15 Apr '13

15 Apr '13

Hello All, It seems that flex arrays do not support slice assignment: py> from scitbx.array_family import flex py> ary = flex.float(range(5)) py> list(ary) [0.0, 1.0, 2.0, 3.0, 4.0] py> ary[:3] = flex.float([41, 42, 43]) --------------------------------------------------------------------------- ArgumentError Traceback (most recent call last) /usr/local/cctbx/cctbx_sources/mmtbx/dynamics/<ipython-input-13-5ce3d648bc6f> in <module>() ----> 1 ary[:3] = flex.float([41, 42, 43]) ArgumentError: Python argument types in float.__setitem__(float, slice, float) did not match C++ signature: __setitem__(scitbx::af::versa<float, scitbx::af::flex_grid<scitbx::af::small<long, 10ul> > > {lvalue}, scitbx::af::small<long, 10ul>, float) __setitem__(scitbx::af::versa<float, scitbx::af::flex_grid<scitbx::af::small<long, 10ul> > > {lvalue}, long, float) Slice assignment is common in python: py> alist = range(5) py> alist[:3] = [41, 42, 43] py> alist [41, 42, 43, 3, 4] Is there a flex array work-alike for this operation? I've found set_selected(): py> sel_ary = flex.bool([True, True, True, False, False]) py> ary.set_selected(sel_ary, flex.float([41, 42, 43])) <scitbx_array_family_flex_ext.float at 0x101df1158> py> list(ary) [41.0, 42.0, 43.0, 3.0, 4.0] But set_selected() is cumbersome for slice assignment because (1) you have to build a flex selection array somehow and (2) you have to put the new values into a flex array of the appropriate type. Is set_selected() the best way? If so, is there something in the cctbx libraries that makes building "slicing" selection arrays more efficient than say a list comprehension? sel_ary = flex.bool([True if i < 3 else False for i in xrange(5)]) James

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cif parser & ccp4 mon_lib incompatibility
by James Stroud 15 Apr '13

15 Apr '13

Hi All, It's a fresh install of the latest-greatest cctbx and of ccp4. Any ideas? % cctbx.python ./tst_sa.py CifParserError: /Applications/ccp4-6.3.0/lib/data/monomers/list/mon_lib_list.cif(line 1) : error 4 : Unexpected token, at offset -1 near global : unexpected input... expected one of : Actually dude, we didn't seem to be expecting anything here, or at least I could not work out what I was expecting, like so many of us these days! Here's the top of the cif file: global _lib_name mon_lib _lib_version 5.36 _lib_update 03/05/12 --------------------------------- # # --- LIST OF MONOMERS --- # data_comp_list loop_ _chem_comp.id _chem_comp.three_letter_code _chem_comp.name _chem_comp.group James

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Re: [cctbxbb] [ccp4bb] CCP4 Update victim of own success
by James Stroud 11 Apr '13

11 Apr '13

On Apr 11, 2013, at 6:17 AM, <eugene.krissinel(a)stfc.ac.uk> <eugene.krissinel(a)stfc.ac.uk> wrote: > Sorry that this was unclear. We assume that updater is used primarily from ccp4i, where nothing changed (and why it should be used from command line at all ?:)). Scriptability. On Apr 11, 2013, at 10:34 AM, Jim Pflugrath wrote: > I think James gets to 'fight' like in the old game of rogue by pressing the h, j, k, l keys on his keyboard (not a detachable one either). While Eugene gets to use a modern game controller or a Wii. > > Ooops, game is already over and James [Holton] has lost. But he wrote the game. James

1 1

bin_centers() and d_star_sq
by James Stroud 09 Apr '13

09 Apr '13

Hello All, I'm genuinely perplexed about what factors should go into choosing an appropriate d_star_sq to calculate bin_centers() in cctbx.miller.binner. This decision may be a nuance because it doesn't seem change the output significantly (except for low resolution bins). But if it doesn't matter significantly, then why have the parameter in the first place? James py> binner = miller.setup_binner(n_bins=10) py> binner.show_summary() unused: - 81.7405 [ 0/0 ] bin 1: 81.7405 - 6.1396 [2341/2341] bin 2: 6.1396 - 4.8734 [2213/2213] bin 3: 4.8734 - 4.2574 [2185/2185] bin 4: 4.2574 - 3.8681 [2168/2168] bin 5: 3.8681 - 3.5909 [2177/2177] bin 6: 3.5909 - 3.3792 [2156/2156] bin 7: 3.3792 - 3.2099 [2137/2137] bin 8: 3.2099 - 3.0702 [2144/2144] bin 9: 3.0702 - 2.9520 [2133/2133] bin 10: 2.9520 - 2.8501 [2135/2135] unused: 2.8501 - [ 0/0 ] py> centers = binner.bin_centers(1) py> list(1 / centers) [11.421375552155686, 5.4336997182888345, 4.544594791289144, 4.053431451445772, 3.7243527058119903, 3.481806175995981, 3.292371389128289, 3.138504394416836, 3.0099330507138475, 2.9001646196929975] py> centers = binner.bin_centers(4) py> list(1 / centers**(1 / 4)) [7.301226942489155, 5.330776416864701, 4.514065417212759, 4.039592121777967, 3.716672320747147, 3.4770032890247498, 3.28912114749567, 3.13617782414047, 3.0081962210988116, 2.8988250671976883]

1 1

match_indices.paired_miller_indices() ungraceful overshoot
by James Stroud 08 Apr '13

08 Apr '13

Hello all, I accidentally gave paired_miller_indices() a value > 1 for i_array, and got a segfault. The problem looks to be in match_indices.cpp, line 94: result.push_back(miller_indices_[i_array][pairs_[i][i_array]]); Maybe there should be a test that raises an exception on the python side, if possible. James

3 3

flex and numpy caveats
by James Stroud 05 Apr '13

05 Apr '13

Hello All, I've noticed some incompatibilities between numpy and cctbx, which is understandable. However, the incompatibilities manifest either as nonsense errors or, worse, not at all. Following are a couple of examples I have found. 1. The first example should really throw an exception, because silent failures like this can be catastrophic: py> from numpy import random py> r = random.randint(2, size=10) py> r array([1, 0, 1, 1, 0, 1, 0, 1, 1, 1]) py> list(flex.bool(r)) [True, False, False, False, False, False, False, False, False, False] This example is clearly due to incorrect assumptions about the internal representations of numpy ndarrays. Much better behavior can be seen when using a sequence of python `int` objects: py> list(flex.bool(range(10))) --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /Users/jstroud/Unison/Code/radialx/testdata/<ipython-input-754-dce96b02979e> in <module>() ----> 1 list(flex.bool(range(10))) TypeError: No registered converter was able to produce a C++ rvalue of type bool from this Python object of type int 2. Although not as potentially catastrophic as the first, the second example should (in a perfect world) either work or throw a more meaningful exception: py> flex.int(range(10))[r[0]] --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /Users/jstroud/Unison/Code/radialx/testdata/<ipython-input-753-f14587f0ceeb> in <module>() ----> 1 flex.int(range(10))[r[0]] TypeError: 'numpy.int64' object is not iterable This example is obviously a result of type checking for a python `int`. The usual python approach of duck-type checking would avoid this problem: def __getitem__(self, i): try: i = int(i) except: pass return do_whatever_with_i(i) James

2 9

Wilson Plot
by James Stroud 01 Apr '13

01 Apr '13

Hello All, The docsting for cctbx.miller.array.wilson_plot() does not seem to agree with its function (see below). Am I misinterpreting something? James py> miller.wilson_plot.__doc__ '<data^2>' py> miller.wilson_plot() (0.6109909654097065+4.386371170677923j) py> flex.mean(miller.data()) (0.6109909654097065+4.386371170677923j) py> flex.mean(miller.data() * flex.conj(miller.data())) (366421.87112270086+0j) py> flex.mean(miller.data() * miller.data()) (70775.39818541733-1856.4852414296488j)

2 1

Miller array by index
by James Stroud 28 Mar '13

28 Mar '13

Hello All, I ask this question mostly out of curiosity, but what is the most direct way to access the value for a Miller index? The best I can do is the method below, but it seems rather indirect. James py> miller <cctbx.miller.array at 0x107bfa290> py> idx = (0, 0, 2) py> miller.select_indices([idx]).data()[0] (-26338.974329482127+0j)

2 1

Re: [cctbxbb] [ccp4bb] refinement protein structure
by James Stroud 27 Mar '13

27 Mar '13

On Mar 27, 2013, at 12:32 PM, Anastassis Perrakis wrote: > These said, I am rather easily irritated these days, so I will not comment on the irritable character of the email. ... > we will soon start calling disordered loops > positionally challenged polypeptide segments (*). You might want to embrace the power of positive thinking. Where you see "positionally challenged", an optimist would see "entropically gifted". James

1 0

Rotate & translate a structure
by James Stroud 26 Mar '13

26 Mar '13

Hello all, I have a rotation + translation matrix. Let's say py> mtx array([[ 0.88302225, 0.11697778, 0.45451948, 5. ], [ 0.11697778, 0.88302225, -0.45451948, 10. ], [ -0.45451948, 0.45451948, 0.76604444, 20. ], [ 0. , 0. , 0. , 1. ]]) My usual way of transforming a set of coordinates with a 4x4 matrix is to use numpy: py> xyz_1 array([[ 5., 10., 15., 1.], [ 20., 15., 10., 1.]]) py> numpy.inner(xyz_1, mtx) array([[ 17.40268126, 12.59731919, 33.76326397, 1. ], [ 28.9603065 , 21.03969455, 25.38784698, 1. ]]) What is the equivalent in cctbx? Is there a way to avoid converting coordinates back and fourth between numpy arrays with atoms().extract_xyz() & .set_xyz() (as might be used from a iotbx_pdb_hierarchy_ext.root). Thank you for any help. James

3 2

Left to dry by iotbx_pdb_ext.input.construct_hierarchy()
by James Stroud 25 Mar '13

25 Mar '13

Hello all, This seems like it should qualify as a bug. If I have an instance of iotbx_pdb_ext.input and I create a hierarchy with construct_hierarchy(), then I must retain the reference to that hierarchy or apparently I can never get it back: >>> hierarchy = my_pdb.construct_hierarchy() >>> def some_local_scope_function(a_pdb): local_hierarchy = a_pdb.construct_hierarchy() >>> some_local_scope_function(my_pdb) […] RuntimeError: atom has another parent atom_group already. Wouldn't better behavior just return the previously constructed hierarchy given that multiple hierarchies can't be made? If each atom apparently remembers to which atom_group it belongs (and presumably on up), then shouldn't it make sense that an iotbx_pdb_ext.input be able to remember it's own hierarchy and produce it upon demand? Looking at a iotbx_pdb_hierarchy_ext.root, I don't find a reference to the iotbx_pdb_ext.input from which it was created. So, although passing around a hierarchy might be the obvious work-around, the end-user still needs to do some accounting if said user wants to track which roots belong to which inputs, and vice versa. James

2 1

Build Notes for cctbx on OS X 10.7.5
by James Stroud 22 Mar '13

22 Mar '13

Hello All, I spent some time to build cctbx on an OS X 10.7 box for a non-system interpreter. I ran into some kinks along the way, so I thought I'd share my notes in case anyone wants to do the same. These notes are in reStructuredText, so it was no extra work to turn them into the attached HTML file, which might make reading a little easier. James ==================================== Build Notes for cctbx on OS X 10.7.5 ==================================== These notes describe a successful build of cctbx against a specific python interpreter, namely `Enthought python`_ 7.3-2 for x86_64. Although working, versions of cctbx are available for both the system python or with a dedicated python, these canned solutions are not optimal. First, it's not advisable to modify system utilities. Although cctbx seems well-behaved in this regard, other packages may not be so well behaved. Second, the canned approach requires building many of the numerous packages that come with bundeld python distributions like the Enthought distribution (some such packages exceed even cctbx in their difficulty to build). Third, if every package required its own python, every script would need to fire-up dozens of separate interpreters just to do its job, resulting in significant computational overhead with consummately slower execution times. .. _`Enthought python`: http://www.enthought.com/products/epd.php 1. The default c++ compiler for OS X 10.7 is actually clang (``/usr/bin/c++``). Using clang exposes invalid template code. The first of many errors is:: In file included from /opt/cctbx/cctbx_sources/mmtbx/bulk_solvent/bulk_solvent_ext.cpp:7: /opt/cctbx/cctbx_sources/mmtbx/bulk_solvent/bulk_solvent.h:496:21: error: call to function 'r_factor' that is neither visible in the template definition nor found by argument-dependent lookup r.push_back(r_factor(f_obs, f_model.const_ref())); These types of errors are documented at the page http://clang.llvm.org/compatibility.html#dep_lookup .. note:: The installation directory is ``/opt/cctbx``. 2. I tried to use the HPC compilers at http://hpc.sourceforge.net/, but they do not recognize the ``-no-cpp-precomp`` flag. The web page https://svn.boost.org/trac/boost/ticket/6697 suggests the problem is with boost. However, according to the comments therein, this should have been fixed in boost 1.50. I am building against boost 1.52. Perplexed about the source of this compiler flag, I tracked it down to the file ``cctbx_sources/libtbx/SConscript``, after spending much of a day learning how scons goes about its business. There are two possible fixes: - Comment the following line in ``cctbx_sources/libtbx/SConscript``:: # env_etc.ccflags_base.extend(["-no-cpp-precomp"]) - Link ``/usr/bin/g++`` to ``c++`` in a way that it will be found first in the path. For example:: % ln -s /usr/bin/g++ ${HOME}/bin/c++ 3. I first fixed the ``-no-cpp-precomp`` error by the former, commenting the offending line in ``cctbx_sources/libtbx/SConscript`` but this failed with the error:: /opt/cctbx/cctbx_sources/scitbx/array_family/memory.h:35:47: error: operator '&&' has no right operand #elif defined(_XOPEN_SOURCE) && _XOPEN_SOURCE >= 600 && defined(_POSIX_ADVISORY_INFO) ^ The page http://forums.fedoraforum.org/archive/index.php/t-52929.html suggests that the naked ``_XOPEN_SOURCE`` wrecks the conditional when ``_XOPEN_SOURCE`` is not defined. One possible way to overcome this problem is to change the offending line into a nested if/then, hoping that the comparison never gets evaluated under circumstances when ``_XOPEN_SOURCE`` is not defined:: #elif defined(_XOPEN_SOURCE) #if _XOPEN_SOURCE >= 600 && defined(_POSIX_ADVISORY_INFO) #define SCITBX_AF_HAS_ALIGNED_MALLOC 1 #define SCITBX_AF_USE_POSIX_FOR_ALIGNED_MALLOC 1 #endif #endif However, this was unnecessary because the second fix to the ``-no-cpp-precomp`` error (linking ``/usr/bin/g++`` to ``c++``) worked and avoided changing the preprocessor source. 4. Left to its own devices, scons could not find my ``fftw3.h``, which I have installed (via fink) to ``/sw/include/fftw3.h``. To fix this problem, I inserted the second of the following two lines into the file ``cctbx_sources/libtbx/SConscript``:: env_etc.ccflags_base.extend(["-no-cpp-precomp"]) env_etc.ccflags_base.extend(["-I/sw/include"]) Although this allowed scons to find the header, it could not find the actual library, requiring the insertion of the second of the following lines into the file ``cctbx_sources/libtbx/SConscript``:: env_etc.shlinkflags_bpl = [ "-L/sw/lib", "-w", # suppress "source/lib does not exist" warning "-bundle", "-undefined", "dynamic_lookup"]

4 5

structure_factors() "d_max" equivalent
by James Stroud 21 Mar '13

21 Mar '13

Hello All, I'm new to cctbx and trying to get the most rudimentary understanding. I would like to select all of the reflections within a particular resolution shell. This line from the tutorial: f_calc = quartz_structure.structure_factors(d_min=2).f_calc_array() gets all structure factors through the highest resolution of d_min=2 Å (excluding 0 0 0). My question: is there an equivalent to a d_max argument for this function (i.e. a low resolution limit)? James

4 3

cctbx and symmetry: source code
by prasun kumar 21 Mar '13

21 Mar '13

Dear all I am developing a software for which I needed to use the unit cell generation module of the cctbx. The software will be working for small molecule as well as macromolecule. It will be a great help, if some body can suggest me the part of the program to be used as I am getting confused while selecting the .cpp and .h files. Thanx alot in advance Prasun Kumar PRASUN (ASHOKA) Desire + stability = Resolution Resolution + Hard work = Success

4 10

changes to SourceForge project
by Nathaniel Echols 19 Mar '13

19 Mar '13

As promised, the CCTBX SourceForge site has been migrated to their new backend. I am still not sure exactly what this means, but there are two practical changes: 1) The SVN URL has changed - it used to be http://cctbx.svn.sourceforge.net/svnroot/cctbx. Now we have several options. svn checkout --username=natechols svn+ssh://[email protected]/p/cctbx/code/trunk cctbx_project svn checkout --username=natechols https://svn.code.sf.net/p/cctbx/code/trunk cctbx_project svn checkout svn://svn.code.sf.net/p/cctbx/code/trunk cctbx_project The last one is read-only; for the others, replace "natechols" with your SourceForge ID. The old repository is now read-only, so you will need to do a completely new checkout before you can commit any changes you make. Hopefully this will cause minimal disruption; I will change the nightly builds ASAP. 2) As requested, we now have a wiki (completely empty right now): https://sourceforge.net/p/cctbx/wiki/Home/ Feel free to start populating this - if you would like to contribute and don't have access, sign up for a SourceForge account and email me your user ID. -Nat

2 1

Best way to compare two structures using cctbx?
by Jan Marten Simons 12 Mar '13

12 Mar '13

Hi, I think I've seen some code in cctbx which tries to put the similarity of two crystal structures into a number. Am I right on this? I want to have something similar: I'm interested in comparing the direct space atomic distances of two structures sharing the same unit cell parameters and space group and scatterers but different atomic coordinates for those. Now I'd like to have a mapping where I could compare the bond lengths between all scatterers which should eliminate any movements which might also be due to a shift in the origin of a P 1 cell. Also I'd like to have a value for mean, minimal and maximal displacements. The purpose of this is to check how good a structure approximation matches a reference structure. How would you suggest to take on this task? Or is there even some code related to this? Thanks in advance, Jan

5 8

upcoming SourceForge changes
by Nathaniel Echols 27 Feb '13

27 Feb '13

FYI for anyone using CCTBX SVN checkouts: on or about March 9th or 10th, I plan to upgrade our SourceForge project to their new platform, which they claim to want everyone to do in the first quarter of 2013. (I had hoped to do this a month ago but it would have created problems for other projects.) This should give us access to new features including a project wiki, requested by several of you. I am hoping any disruption to SVN access will be minimal and/or quickly resolved (the timing coincides with our Phenix developer workshop so those of us who are attending will be able to fix problems interactively). I'll send out another email after the switch summarizing any changes. -Nat

1 0

pdb shake - dihedral angles
by Dmytro Guzenko 20 Feb '13

20 Feb '13

Hi everyone, I wonder what would it take to write an equivalent to pdb_shake script from iotbx/examples with randomization of the backbone dihedral angles phi and psi, instead of all coordinates perturbation? I want to be able to randomize models in a more "realistic" way. Are there data structures/procedures that can be useful for this in cctbx, or should I extract the coordinates and take it from there? Thanks! Kind regards, Dmytro.

3 2

Re: [cctbxbb] unexpected behaviour of unit_cell.fractionalize
by Jan Marten Simons 14 Feb '13

14 Feb '13

Am Mittwoch 13 Februar 2013 17:01:37 you wrote: > Hi Jan, > > can this method work for you: sites_mod_positive ? I don't remember what > exactly it does but I think it either what you need or at least very close. Hi Pavel, hm, it goes in the right direction, but is not exactly what I'm looking for, as it is bound to scatterers and not to sites in general. And adding a scatterer for each site I want to convert to the structure first, then converting, and than extracting the converted sites from the scatterers afterwards seems quite inefficient to me. Also I think it would be clearer to add the functionality for this to the "fractionalize" function as people trying to convert from direct space coordinates to fractional coordinates will most likely find this functionality first. Cheers, Jan > On 2/13/13 7:17 AM, Jan Marten Simons wrote: > > Hi, > > > > When I try to convert a list of direct space coordinates into fractional > > coordinates like this: > > > > from cctbx import xray > > from cctbx import crystal > > from cctbx.array_family import flex > > > > structure = xray.structure( > > > > special_position_settings=crystal.special_position_settings( > > > > crystal_symmetry=crystal.symmetry( > > > > unit_cell=(3.14098, 4.08327, 5.33966, 83, 109, 129), > > space_group_symbol="P1"))) > > > > sites = flex.vec3_double( ((0.0, 0.1, 0.2), (1.3, 3.0, 2.3), (5.3, 0.1, > > 7.3)) ) sites_frac = structure.unit_cell().fractionalize(sites) > > print(list(sites_frac)) > > > > Now this returns a list of coordinates where x,y,z may be outside ot the > > interval [0,1[. ... quite unexpected. > > > > It would be very nice to have at least an option like "restrict_to_asu" > > in unit_cell.fractionalize which would enforce (x,y,z) to be inside the > > asymmetric unit and/or "restrict_to_cell" which would enforce (x,y,z) to > > be inside the unit cell. > > > > Could any of you more into the inner workings of the cctbx add this > > functionality, please? > > > > Thanks in advance, > > > > Jan

3 4

unexpected behaviour of unit_cell.fractionalize
by Jan Marten Simons 13 Feb '13

13 Feb '13

Hi, When I try to convert a list of direct space coordinates into fractional coordinates like this: from cctbx import xray from cctbx import crystal from cctbx.array_family import flex structure = xray.structure( special_position_settings=crystal.special_position_settings( crystal_symmetry=crystal.symmetry( unit_cell=(3.14098, 4.08327, 5.33966, 83, 109, 129), space_group_symbol="P1"))) sites = flex.vec3_double( ((0.0, 0.1, 0.2), (1.3, 3.0, 2.3), (5.3, 0.1, 7.3)) ) sites_frac = structure.unit_cell().fractionalize(sites) print(list(sites_frac)) Now this returns a list of coordinates where x,y,z may be outside ot the interval [0,1[. ... quite unexpected. It would be very nice to have at least an option like "restrict_to_asu" in unit_cell.fractionalize which would enforce (x,y,z) to be inside the asymmetric unit and/or "restrict_to_cell" which would enforce (x,y,z) to be inside the unit cell. Could any of you more into the inner workings of the cctbx add this functionality, please? Thanks in advance, Jan

2 1

Strange behaviour of resolution filter
by Jan Marten Simons 08 Feb '13

08 Feb '13

Hi, I discovered a rather strange behaviour of the miller.index_generator. Sample code showing the weirdness: -----8<--------------------------- from __future__ import division from cctbx import xray from cctbx import crystal from cctbx.array_family import flex structure = xray.structure( special_position_settings=crystal.special_position_settings( crystal_symmetry=crystal.symmetry( unit_cell=(3.14098, 4.08327, 5.33966, 83, 109, 129), space_group_symbol="P 1")), scatterers=flex.xray_scatterer([ xray.scatterer( label="Si", site=(0.,0.,0.), u=0.0)])) fc1 = structure.structure_factors(d_min=1.0).f_calc().sort() d_max, d_min = fc1.resolution_range() fc2 = structure.structure_factors(d_min=d_min).f_calc().sort() print(fc1.size(), fc2.size()) #fc1.show_array() fc1.show_comprehensive_summary() print("\nd_min: {}\n".format(d_min)) fc2.show_comprehensive_summary() #fc2.show_array() -----8<--------------------------- fc1 has 105 indices, while fc2 only has 104. Also fc2 has a higher d_min than fc1 although I'd expect both to have the same. To me it seems like the index with d==d_min is not included and only indices with d>d_min are calculated. I wonder if this behaviour is the desired one or rather a bug, as I was quite surprised when I discovered this. With regards, Dipl. Phys. Jan M. Simons Institute of Crystallography RWTH Aachen University

2 1

Using cctbx::uctbx::unit_cell in c++ code / boosted to Python
by Graeme.Winter＠diamond.ac.uk 25 Jan '13

25 Jan '13

Hi Folks, Been working on some c++ coding using boost etc (which I have to say is great) however I found one bit of weirdness. If I want to generate a cctbx::uctbx::unit_cell in c++ code then access this from Python I get Traceback (most recent call last): File "tst_x2tbx.py", line 67, in <module> tst_x2tbx(sys.argv[1]) File "tst_x2tbx.py", line 6, in tst_x2tbx import x2tbx File "/Users/graeme/svn/cctbx/sources/x2tbx/__init__.py", line 7, in <module> ext = boost.python.import_ext("x2tbx_ext", optional = False) File "/Users/graeme/svn/cctbx/sources/cctbx_project/boost_adaptbx/boost/python.py", line 36, in import_ext + [" "+p for p in sys.path])) ImportError: __import__("x2tbx_ext"): dlopen(/Users/graeme/svn/cctbx/prebuild/lib/x2tbx_ext.so, 2): Symbol not found: cctbx::uctbx::unit_cell::unit_cell(scitbx::af::tiny<double, 6ul> const&) Referenced from: /Users/graeme/svn/cctbx/prebuild/lib/x2tbx_ext.so Expected in: flat namespace in /Users/graeme/svn/cctbx/prebuild/lib/x2tbx_ext.so sys.path: …. unless I have import cctbx.uctbx # explicit import at the top of the Python code - have I done something wrong with the SConscript? I found something similar with import scitbx.array_family.flex # explicit import which libtbx.clean_clutter complains about as I don't reference it (hence the additional comment) Equally I could just leave the additional clutter there but it feels like I should not need it... Thanks, Graeme -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

4 8

Sphinx documentation
by Graeme.Winter＠diamond.ac.uk 21 Jan '13

21 Jan '13

Hi Folks, I installed sphinx and tried building the documentation but I got an error: File ./xfel/xfel.cxi.gfx.rst already exists, skipping. File ./xfel/xfel.cxi.merging.rst already exists, skipping. File ./xfel/xfel.cxi.rst already exists, skipping. File ./xfel/xfel.metrology.rst already exists, skipping. File ./xfel/xfel.rst already exists, skipping. File ./xfel/modules.rst already exists, skipping. sphinx-build -b coverage -d _build/doctrees -D latex_paper_size=a4 . _build/coverage Making output directory... Running Sphinx v1.2pre loading pickled environment... not yet created building [coverage]: coverage overview updating environment: 206 added, 0 changed, 0 removed reading sources... [ 0%] cctbx/cctbx Exception occurred: File "/Users/graeme/svn/cctbx/phenix/phenix-dev-1241/build/mac-intel-osx-x86_64/base/Python.framework/Versions/Current/lib/python2.7/site-packages/Sphinx-1.2predev_20130121-py2.7.egg/sphinx/ext/autodoc.py", line 595, in filter_members membername in self.options.special_members: TypeError: argument of type 'object' is not iterable The full traceback has been saved in /var/folders/j1/cgsqy8fs1lxdyjggcsb3twsw0000gn/T/sphinx-err-jjM5C8.log, if you want to report the issue to the developers. Please also report this if it was a user error, so that a better error message can be provided next time. Either send bugs to the mailing list at <http://groups.google.com/group/sphinx-users/>, or report them in the tracker at <http://bitbucket.org/birkenfeld/sphinx/issues/>. Thanks! make: *** [coverage] Error 1 cp: ./_build/coverage/python.txt: No such file or directory cp: ./_build/coverage/c.txt: No such file or directory sphinx-build -b html -d _build/doctrees -D latex_paper_size=a4 . _build/html Making output directory... Running Sphinx v1.2pre loading pickled environment... not yet created building [html]: targets for 206 source files that are out of date updating environment: 206 added, 0 changed, 0 removed reading sources... [ 0%] cctbx/cctbx Exception occurred: File "/Users/graeme/svn/cctbx/phenix/phenix-dev-1241/build/mac-intel-osx-x86_64/base/Python.framework/Versions/Current/lib/python2.7/site-packages/Sphinx-1.2predev_20130121-py2.7.egg/sphinx/ext/autodoc.py", line 595, in filter_members membername in self.options.special_members: TypeError: argument of type 'object' is not iterable The full traceback has been saved in /var/folders/j1/cgsqy8fs1lxdyjggcsb3twsw0000gn/T/sphinx-err-lONSky.log, if you want to report the issue to the developers. Please also report this if it was a user error, so that a better error message can be provided next time. Either send bugs to the mailing list at <http://groups.google.com/group/sphinx-users/>, or report them in the tracker at <http://bitbucket.org/birkenfeld/sphinx/issues/>. Thanks! make: *** [html] Error 1 Did I do something wrong? I just grabbed sphinx from the internet. Should I have got it from someplace else? OS X Lion / svn cctbx. Thanks, Graeme -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

2 1

Phil (dumb) question
by Graeme.Winter＠diamond.ac.uk 14 Jan '13

14 Jan '13

Hi Folks, I have a toy example where I should be overriding Phil defaults: phil_defaults = ''' resolutionizer { rmerge = 0.0 .type = float completeness = 0.0 .type = float isigma = 1.0 .type = float misigma = 2.0 .type = float bins = 100 .type = int } ''' more = ''' resolutionizer { isigma = 2.0 misigma = 4.0 } ''' from libtbx.phil import parse working_phil = parse(phil_defaults) working_phil.fetch(parse(more)) working_phil.show() but it seems I am not: Graemes-MacBook-Pro:scale graeme$ cctbx.python toy.py resolutionizer { rmerge = 0.0 completeness = 0.0 isigma = 1.0 misigma = 2.0 bins = 100 } Am I doing something dumb? I hope so as I really cannot find my error. Thanks, Graeme -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

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Simple cctbx / boost c++ extension example
by Graeme.Winter＠diamond.ac.uk 11 Jan '13

11 Jan '13

Hi Folks, Just say I wanted to write a new from the ground up module for cctbx which wanted to include some C++ code, and a SConscript etc. so I can run libtbx.configure toytbx (say) And then find from toytbx import cplusplus_functions would work.... Is there an example I could follow? (I have not looked through the newsletters, I suppose I should have... but I could not seen anything obvious in the documents) Thanks, Graeme Dr. Graeme Winter Senior Software Scientist Diamond Light Source +44 1235 778091 (work) +44 7786 662784 (work mobile) -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

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Computing E^4 from an mtz file
by Graeme.Winter＠diamond.ac.uk 14 Dec '12

14 Dec '12

Hi Folks, Trying to write some code to return the average E^4 across (some) bins for an mtz file, I got to def main(): import sys from iotbx import reflection_file_reader for argv in sys.argv[1:]: reflection_file = reflection_file_reader.any_reflection_file( file_name = argv) if reflection_file.file_type() is None: continue miller_arrays = reflection_file.as_miller_arrays() for ma in miller_arrays: E4(ma) def E4(ma): f = ma.as_intensity_array() f = f.array(data=f.data()/f.epsilons().data().as_double()) f.set_observation_type_xray_intensity() f.setup_binner(auto_binning = True) sm = f.second_moment(use_binning = True) sm.show() if __name__ == '__main__': main() but I have no idea how to actually extract the information I want from sm as this only has show() which gives Graemes-MacBook-Pro:PlayPen graeme$ cctbx.python E4.py /Users/graeme/projects/sci-397/DEFAULT/scale/AUTOMATIC_DEFAULT_scaled.mtz unused: - 20.8668 [ 0/7 ] bin 1: 20.8668 - 5.8873 [221/235] 2.3863 bin 2: 5.8873 - 4.6904 [216/221] 1.9823 bin 3: 4.6904 - 4.1026 [221/222] 1.9925 <snip> bin 47: 1.6553 - 1.6435 [153/209] 2.2051 bin 48: 1.6435 - 1.6320 [143/198] 2.2021 bin 49: 1.6320 - 1.6208 [141/204] 2.7085 unused: 1.6208 - [ 0/0 ] unused: - 20.8668 [ 0/9 ] bin 1: 20.8668 - 7.1654 [201/225] 2.2405 bin 2: 7.1654 - 5.7261 [202/213] 1.9109 bin 3: 5.7261 - 5.0137 [216/223] 2.0162 bin 4: 5.0137 - 4.5605 [207/212] 2.0043 <snip> bin 87: 1.6456 - 1.6393 [126/192] 2.5521 bin 88: 1.6393 - 1.6330 [122/210] 2.0195 bin 89: 1.6330 - 1.6269 [131/224] 2.6251 bin 90: 1.6269 - 1.6208 [120/212] 3.0912 unused: 1.6208 - [ 0/0 ] Really I would like the value programatically or at least a way of getting back an array of the binned values so I can average them myself (which is obviously trivial) Any suggestions? Thanks, Graeme ps - most of this code is ripped from iotbx.reflection_statistics :o) -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

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Writing a pdb file from an xray_structure object
by Claudia Millán Nebot 12 Dec '12

12 Dec '12

Hi everyone, i have been using the xray_structure_simple() method to get an xray.structure object from a pdb object and use it to perform some calculations on it, one of them being expand it to P1. After, i tried to write a new pdb out of this xray_structure in P1. For that purpose, i used the following method: cctbx.xray.structure.as_pdb_file(self, remark=None, remarks=[], fractional_coordinates=False, resname=None, connect=None) but using it both with the original xray structure and with the one on P1 I get very bad lookings pdbs, with incorrect formating, like that for the case of the one in P1: ATOM 1 PDB= PDB 1 12.330 -6.948 -40.820 1.00 19.26 N ATOM 2 PDB= PDB 2 49.988 55.370 3.948 1.00 19.26 N ATOM 3 PDB= PDB 3 36.092 30.710 93.483 1.00 19.26 N ATOM 4 PDB= PDB 4 55.370 49.988 175.123 1.00 19.26 N ATOM 5 PDB= PDB 5 30.710 36.092 85.587 1.00 19.26 N so i guessed that something must be wrong with the residues.... and went to check the code. That as_pdb_file method calls to iotbx.pdb.xray_structure.as_pdb_file(), and on that code i realised that as i was calling it whithout any resname, it was retrieving it from some information on the scatterers that could be wrong. Putting the value of resname to ALA, as a trial, produced almost the same output except for the name: ATOM 1 PDB= ALA 1 12.330 -6.948 -40.820 1.00 19.26 N ATOM 2 PDB= ALA 2 49.988 55.370 3.948 1.00 19.26 N ATOM 3 PDB= ALA 3 36.092 30.710 93.483 1.00 19.26 N ATOM 4 PDB= ALA 4 55.370 49.988 175.123 1.00 19.26 N ATOM 5 PDB= ALA 5 30.710 36.092 85.587 1.00 19.26 N Up to this point, i don't get what is wrong. It may be that i'm using a too simple method and without the correct parameters (xray_structure_simple()), as i guess part of the error is that the assignation of the types of atoms and residues is going crazy. There are other ways of performing this step from a pdb to an xray_structure and viceversa? Thanks in advance! Best regards, Claudia Millán (cmncri(a)ibmb.csic.es) Institut de Biologia Molecular de Barcelona (IBMB-CSIC) Barcelona, Spain

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Documentation .... again
by Graeme.Winter＠diamond.ac.uk 12 Dec '12

12 Dec '12

Hi Folks, Been thinking some more about the old chestnut of documentation. The lack thereof is a well understood issue, and to be honest one which is not going to change any time soon as no one has the time to maintain a manual - this is fine and well understood. As a kind of "patch" for this I was wondering if it would be possible to have a forum where someone could ask for e.g. documentation for a currently undocumented function, which could then be added to the subversion in the code itself. For example: cctbx_project/cctbx/xray/structure.py ... def structure_factors(self, anomalous_flag=None, d_min=None, algorithm=None, cos_sin_table=False, quality_factor=None, u_base=None, b_base=None, wing_cutoff=None): what is cos_sin_table for? with things like this there is the attitude that it is safe to ignore, however if we're writing code to guide people's experiments it would be good to be sure of this. Some simple documentation explaining this would be very useful. I'm definitely not suggesting (i) that anyone writes a manual or (ii) that all undocumented functions are suddenly documented, only that there is a mechanism set up that someone could ask about this and that someone who knows the answer could commit the changes to cctbx and then reply with the diffs - perhaps the way that stackoverflow works, or an email, or something really lightweight. Even this mailing list could be used I guess? I would be happy to help with this, though the above example is not one where I know the answer! Thoughts? Best wishes, Graeme Dr. Graeme Winter Senior Software Scientist Diamond Light Source +44 1235 778091 (work) +44 7786 662784 (work mobile) -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

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Structure factor calculation weirdness
by Graeme.Winter＠diamond.ac.uk 10 Dec '12

10 Dec '12

Hi Folks, Some confusion here at diamond - it seems that the amplitude of F(hkl) depends on dmin ---------------- from cctbx import xray from cctbx import crystal from cctbx.array_family import flex # 14keV wavelength = 12.3984 / 14.0 spgroup = 'Fd-3m' latt = (5.4309, 5.4309, 5.4309, 90, 90, 90) atoms = [('Si', 0.125, 0.125, 0.125)] allscatterers=[] for atom in atoms: allscatterers.append(xray.scatterer( label = atom[0], site = (atom[1], atom[2], atom[3]), u = 0)) structure = xray.structure( special_position_settings = crystal.special_position_settings( crystal_symmetry = crystal.symmetry( unit_cell = latt, space_group_symbol = spgroup)), scatterers = flex.xray_scatterer(allscatterers)).expand_to_p1() for dmin in 5.0, 2.5, 1.7: print dmin f_calculations = structure.structure_factors( d_min = dmin).f_calc().amplitudes().show_array() --------------- Chopped out only 001, 010, 100 from this... 5.0 (0, 0, 1) 0.290277589693 (0, 1, 0) 0.290277589693 (1, 0, 0) 0.290277589693 2.5 (0, 0, 1) 0.0 (0, 1, 0) 0.0 (1, 0, 0) 0.0 <snip> 1.7 (0, 0, 1) 0.278378587828 (0, 1, 0) 0.278378587828 (1, 0, 0) 0.278378587828 <snip> Have we misunderstood something? Thanks, Graeme Dr. Graeme Winter Senior Software Scientist Diamond Light Source +44 1235 778091 (work) +44 7786 662784 (work mobile) -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

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UB matrix in cbf files
by Carlo.Vecchini＠diamond.ac.uk 04 Dec '12

04 Dec '12

Hello, I would like to add the orientation matrix information in the cbf file. Following the description in sections 3.2.2.2.3 of IUCr (G), I added the following lines in the cbf header: _diffrn_orient_matrix_type ub_matrix_test _diffrn_orient_matrix_UB_11 0.083424 _diffrn_orient_matrix_UB_12 -0.076007 _diffrn_orient_matrix_UB_13 -0.078787 _diffrn_orient_matrix_UB_21 -0.103374 _diffrn_orient_matrix_UB_22 -0.075939 _diffrn_orient_matrix_UB_23 -0.01146 _diffrn_orient_matrix_UB_31 -0.034434 _diffrn_orient_matrix_UB_32 0.043832 _diffrn_orient_matrix_UB_33 -0.156476 When I try to read back the values with: get_orientation_matrix() I get the following error: UBm = cbf_handle.get_orientation_matrix() File "~/CCTBX/cctbx_plus_build/lib/pycbf.py", line 3915, in get_orientation_matrix return _pycbf.cbf_handle_struct_get_orientation_matrix(self) Exception: CBFlib Error(s): CBF_NOTFOUND If I use set_orientation_matrix() to write the cbf file, I get a similar error. Does anyone have any suggestion on how to solve this? Thanks in advance, Carlo Vecchini -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

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CBF compositing
by Frank Murphy 03 Dec '12

03 Dec '12

Hello, Does anyone have a CCTBX-based method for compositing multiple CBFs to a single image a la merge2cbf? Thanks in advance, Frank Murphy

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OS X Lion + CCTBX + scipy
by Graeme.Winter＠diamond.ac.uk 01 Dec '12

01 Dec '12

Hi Folks, Has anyone got scipy to build against the cctbx python binary distribution on OS X Lion? I am finding that it keeps on compiling some bits of the library for PPC architecture which does not work... Thanks, Graeme Dr. Graeme Winter Senior Software Scientist Diamond Light Source +44 1235 778091 (work) +44 7786 662784 (work mobile) -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

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SVN broken?
by Jan Marten Simons 24 Oct '12

24 Oct '12

Hi, while trying to update to the latest svn revision or when trying a fresh checkout I encounter this error: svn co https://cctbx.svn.sourceforge.net/svnroot/cctbx/trunk cctbx_project svn: Can't find a temporary directory: Internal error According to a quick web search the problem is most likely on the svn server (either no disk space or corrupted .svn dir). Hopefully either sourceforge or any of you can fix this. Cheers, Jan

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Re: [cctbxbb] Question about sigma(I) calculation in merge_equivalents
by Kay Diederichs 21 Oct '12

21 Oct '12

Dear Keitaro, Phil, Luc, after looking into the question of how to merge equivalent reflections (in the context of XDS data processing), I am now convinced that cctbx should _not_ use max(internal sigma, external sigma) by default. Why? - it is not obvious to the "end user" of the data that come out of cctbx that this formula was applied (I am not aware that the above formula is clearly documented) - the data processing programs that I know of do not use this formula, but rather use the "external sigma" . I don't imply that the "external sigma" is better, but it violates the principle of least surprise to deviate from a proven procedure. - if the observations (that are merged in cctbx) come from one of these data processing programs then there is a chance that the error model was already adjusted such that the reduced chi**2 is near 1 (at least this is the case for XDS and SCALA). If the sigmas of the merged data then are adjusted upwards again (by the formula above), I have a strong feeling that this leads to an inconsistency. - using max() seems like an ad-hoc way and it lacks a clear rationale. I would like to see examples of comparison of downstream crystallographic calculations (most importantly, experimental phasing) using different ways of calculating the sigma of the merged data. Until this proves the superiority of the above formula, I believe it should be an option, not a default. thanks, Kay > Keitaro Yamashita yamashita at castor.sci.hokudai.ac.jp > Thu Sep 6 09:20:34 PDT 2012 > > Previous message: [cctbxbb] Question about sigma(I) calculation in > merge_equivalents > Next message: [cctbxbb] Question about sigma(I) calculation in > merge_equivalents > Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] > > Dear Luc, > > Thank you for your explanation! I understand better than before. > > Usually, sigmas given by data processing programs are already > corrected based on their error model. > Sigmas are adjusted to match the actual scatter. > I think using internal variance is re-correction of sigmas. > Is it valid way? If internal variance is bigger, it suggests error > model is not perfect? > > I calculated external/internal variances using lysozyme (standard > sample in protein crystallography) data. > Intensities and sigmas are determined by XDS. > > I attached two plots, where "Imean", "wsigma", "sigma" are averaged > intensity, internal sigma, external sigma, respectively. > One plot is histogram of wsigma/sigma by multiplicity. For lower > multiplicity, we can see extreme discrepancies. (Note that each > vertical axis is not on the same scale.) > The other plot is wsigma/sigma vs intensity. Extreme discrepancies can > be seen in lower intensities. > I hope it could be interesting for you. > > > > Crystals use only the external variance by default, the reasoning > being that the internal variance being based on sample statistics is > almost always too unreliable because groups of equivalent reflections > are too small. > > Then, I think it would be nice if we can choose the way in cctbx. > I mean, option to choose "use bigger one" or "always use > external/internal variance" would be nice to have. > > I am looking forward to your comment. > > Best regards, > Keitaro > > 2012/9/6 Luc Bourhis <luc_j_bourhis at mac.com>: > > Dear Keitaro, > > > >> But it is still unclear to me why it takes the greatest of the > >> "internal" variance and "external" variance. > >> Is it based on some tests using real data? or is it theoretically > >> superior to using always external variance? > > > > Those are good questions and to be honest I do not know for sure the > answer to them. As it seems common in applied statistics, the treatment > starts with by-the-book methods relying on a well defined theory but at > the end there is always a completely heuristic twist. Particularly true > in crystallography I would argue. But let me try to give some rationales. > > > > It seems to me that the internal and external variance should not > differ too much. Let's consider the two ways this may not be true. > > > > 1. The quoted intensities of a group of equivalent reflections have a > small spread, leading to a small internal variance, but the quoted > sigma's are comparatively big, resulting in an external variance > significantly bigger than the internal one. This is a possible event but > an unlikely one: the statistical intuition in that case is to say that > the small internal variance is a fluke and to use the external one instead. > > > > 2. An external variance significantly smaller than the internal one, > should ring an alarm bell. Indeed a small external variance means that > the small quoted sigma's strongly suggests the intensities cannot spread > too much from their assumed common true value whereas the comparatively > bigger internal variance blatantly contradicts that. Thus either the > intensities or the sigma's have not been correctly determined. > Crystallographers seem to err on the side of trusting data here, i.e. to > disregard the sigma's, and therefore to choose the internal variance. > > > >> I would like to know how this method affects further > crystallographic process. > > > > I am afraid I do not have experience with your domain, protein > crystallography. I know that the small molecule program Crystals use > only the external variance by default, the reasoning being that the > internal variance being based on sample statistics is almost always too > unreliable because groups of equivalent reflections are too small. Since > Crystals is as well accepted as ShelXL to produce publishable > structures, it answer your question in at least in one corner of > crystallography, unfortunately not yours. > > > > I think it could be a simple and interesting exercise to take a > representative protein dataset of yours, then to print the redundancy, > the internal, and the external variance. Actually I would be surprised > if such a study has not already been done and published. Perhaps some of > the gurus on this forum can shed more lights onto that subject. > > > > Best wishes, > > > > Luc -- Kay Diederichs http://strucbio.biologie.uni-konstanz.de email: Kay.Diederichs(a)uni-konstanz.de Tel +49 7531 88 4049 Fax 3183 Fachbereich Biologie, Universität Konstanz, Box M647, D-78457 Konstanz This e-mail is digitally signed. If your e-mail client does not have the necessary capabilities, just ignore the attached signature "smime.p7s".

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FYI: The Quaternion Characteristic Polynomial method
by Jeffrey Van Voorst 19 Oct '12

19 Oct '12

Greetings, If you already know about the quaternion characteristic polynomial method for a fast closed-form solution of the least squares superposition problem, this note is mostly noise. While in the process of updating links to my project, I noticed the note at the bottom of the cctbx sourceforge page (http://cctbx.sourceforge.net/). I like the historical nature presented, and I used the historical method to numerically solve quartic polynomials in a previous project at Michigan State University that ranks relatively large datasets of protein small-molecule binding sites (with respect to a given query site). The superposition method I used has a closed form and is due to BKP Horn. Later on (after writing my dissertation), I found that using the historical method to numerically solve quartic polynomials is not numerically stable or robust. Fortunately, there is an easy solution, and if you are interested in a fast closed-form solution for the least squares superposition problem you would do well (in my opinion) to visit http://theobald.brandeis.edu/qcp/. Best regards, Jeff Van Voorst

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