Hi Martin,

Based on

iotbx.lattice_symmetry --unit_cell="4.630811 4.630811 4.630811 90 90 90"

and

iotbx.lattice_symmetry --unit_cell="3.27448 5.67156 5.67156 99.5941 106.779 90"

the first unit cell is (obviously) cubic, the second is only monoclinic. Even with

iotbx.lattice_symmetry --unit_cell="3.27448 5.67156 5.67156 99.5941 106.779 90" --delta=20

it only comes back as orthorhombic.

Is this what you expect?

Ralf



On Tue, Apr 24, 2012 at 10:57 AM, Martin Uhrin <martin.uhrin.10@ucl.ac.uk> wrote:
Dear cctbxers,

I've finally found the time to play around with a C++ version of the KG algorithm and I've come across a result I don't understand.  I've tried both David's C++ and the cctbx python niggli_cell() implementations and they both give the roughly the same answer.

I'm reducing the following cell with two, equivalent, representations (a, b, c, alpha, beta, gamma):

Before:

1: 4.630811   4.630811   4.630811         90         90         90
2: 3.27448     5.67156    5.67156           99.5941 106.779 90

After:

1: 4.63081    4.63081    4.63081    90          90  90
2: 3.27448    5.67154    5.67156    99.5941  90   106.778

Looking at the trace, cell 1 undergoes step 3 and finishes while cell 2 undergoes steps 2, 3, 7 and 4.

Does anyone know why these haven't converged to the same cell?

Many thanks,
-Martin

On 23 March 2012 17:12, Ralf Grosse-Kunstleve <rwgrosse-kunstleve@lbl.gov> wrote:
Hi Martin,
Let me know if you need svn write access to check in your changes. All I need is your sourceforge user id.
Ralf


On Fri, Mar 23, 2012 at 3:35 AM, Martin Uhrin <martin.uhrin.10@ucl.ac.uk> wrote:
Dear David and Rolf,

thank you for your encouragement.

David: I'm more than happy to port your implementation to cctbx if you're happy with this.  Of course I don't want to step on your toes so if you'd rather do it yourself (or not at all) that's cool.

There may be some licensing issues to sort out as it looks like cctbx has a custom (non viral) license but the BSD license is likely compatible.

On first impression I think a new class would be the way to go but I'd have to look at the two algorithms in greater detail to be sure.

All the best,
-Martin


On 22 March 2012 22:00, Ralf Grosse-Kunstleve <rwgrosse-kunstleve@lbl.gov> wrote:
Hi Martin,
You're very welcome to add a C++ version of the Krivy-Gruber algorithm to cctbx if that's what you had in mind.
I'm not sure what's better, generalizing the fast-minimum-reduction code, or just having an independent implementation.
Ralf

On Thu, Mar 22, 2012 at 2:24 PM, Martin Uhrin <martin.uhrin.10@ucl.ac.uk> wrote:
Dear Cctbx community,

Firstly I'd like to say thank you to Rolf, Nicholas and Paul for their expertly thought through implementation of the reduced cell algorithm.  I've found it to be extremely useful for my work.

My code is all in C++ and I'd like to be able to use the Krivy-Gruber algorithm.  My understanding is that only the reduced (Buerger) unit cell algorithm is implemented in C++ [1] which guarantees shortest lengths but not unique angles.  From my understanding the Krivy-Gruber would also guarantee me uniqueness of unit cell angles, however this is only implemented in Python [2].  Sorry to be so verbose, I just wanted to check that I was on the right page.

Would it be possible for me to implement the Krivy-Gruber in C++ by adding in the epsilon_relative to the parameter and following the procedure found in the python version?

Many thanks,
-Martin




--
Martin Uhrin                                                  Tel: +44 207 679 3466
Department of Physics & Astronomy               Fax:+44 207 679 0595
University College London                         martin.uhrin.10@ucl.ac.uk
Gower St, London, WC1E 6BT, U.K.         http://www.cmmp.ucl.ac.uk

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--
Martin Uhrin                                                  Tel: +44 207 679 3466
Department of Physics & Astronomy               Fax:+44 207 679 0595
University College London                         martin.uhrin.10@ucl.ac.uk
Gower St, London, WC1E 6BT, U.K.         http://www.cmmp.ucl.ac.uk

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_______________________________________________
cctbxbb mailing list
cctbxbb@phenix-online.org
http://phenix-online.org/mailman/listinfo/cctbxbb




--
Martin Uhrin                                                  Tel: +44 207 679 3466
Department of Physics & Astronomy               Fax:+44 207 679 0595
University College London                         martin.uhrin.10@ucl.ac.uk
Gower St, London, WC1E 6BT, U.K.         http://www.cmmp.ucl.ac.uk

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