<div dir="ltr"><div dir="ltr">Possibly because the "Fast" aspect of the "FFT" requires the map size to have a prime factorization of small factors, generally combinations of powers of 2, 3, 5, 7, and 11, in order for the algorithm to work. Here's some basic documentation from the web: <a href="http://www.fftw.org/fftw2_doc/fftw_3.html">http://www.fftw.org/fftw2_doc/fftw_3.html</a></div><div dir="ltr"><br></div><div dir="ltr">Nick<br><div><br clear="all"><div><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div>Nicholas K. Sauter, Ph. D.<br>Senior Scientist, Molecular Biophysics & Integrated Bioimaging Division<div>Lawrence Berkeley National Laboratory<br>1 Cyclotron Rd., Bldg. 33R0345<br>Berkeley, CA 94720<br>(510) 486-5713<br></div></div></div></div></div></div></div></div></div><br></div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Feb 18, 2020 at 9:43 AM GEORGE N PHILLIPS <<a href="mailto:george.phillips@wisc.edu">george.phillips@wisc.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">I am confused about grid sizes of maps.<br>
<br>
When i specify a grid size for an fft_map but then pull the numpy array out for direct manimpulation, it's always 2 larger in the last dimension.<br>
<br>
Why is it not the same size? Any help appreciated.<br>
<br>
George<br>
<br>
<br>
y# Now make initial (smoothed) map using random phases with Fobs<br>
f_obs_B = f_obs1.apply_debye_waller_factors( b_iso=biso_init)<br>
phases = f_obs_B.random_phases_compatible_with_phase_restrictions(deg=False)<br>
phases_data = phases.data()<br>
e_map_coeff = f_obs_B.phase_transfer(phase_source = phases_data)<br>
e_map = e_map_coeff.fft_map(crystal_gridding = crystal_gridding, symmetry_flags = maptbx.use_space_group_symmetry)<br>
print("cgridding", crystal_gridding.n_real())<br>
# pick initial envelope<br>
e_map_array = e_map.real_map().as_numpy_array()<br>
print("e_map", e_map_array.shape)<br>
<br>
<br>
cgridding (90, 90, 80)<br>
e_map (90, 90, 82)<br>
<br>
George N. Phillips, Jr., Ph.D.<br>
Professor Emeritus<br>
University of Wisconsin-Madison<br>
433 Babcock Dr. Madison, Wi 53706<br>
Phone 713 348 6951 (Houston)<br>
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</blockquote></div>