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:
http://www.fftw.org/fftw2_doc/fftw_3.html
Nick
Nicholas K. Sauter, Ph. D.
Senior Scientist, Molecular Biophysics & Integrated Bioimaging Division
Lawrence Berkeley National Laboratory
1 Cyclotron Rd., Bldg. 33R0345
Berkeley, CA 94720
(510) 486-5713
On Tue, Feb 18, 2020 at 9:43 AM GEORGE N PHILLIPS
I am confused about grid sizes of maps.
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.
Why is it not the same size? Any help appreciated.
George
y# Now make initial (smoothed) map using random phases with Fobs f_obs_B = f_obs1.apply_debye_waller_factors( b_iso=biso_init) phases = f_obs_B.random_phases_compatible_with_phase_restrictions(deg=False) phases_data = phases.data() e_map_coeff = f_obs_B.phase_transfer(phase_source = phases_data) e_map = e_map_coeff.fft_map(crystal_gridding = crystal_gridding, symmetry_flags = maptbx.use_space_group_symmetry) print("cgridding", crystal_gridding.n_real()) # pick initial envelope e_map_array = e_map.real_map().as_numpy_array() print("e_map", e_map_array.shape)
cgridding (90, 90, 80) e_map (90, 90, 82)
George N. Phillips, Jr., Ph.D. Professor Emeritus University of Wisconsin-Madison 433 Babcock Dr. Madison, Wi 53706 Phone 713 348 6951 (Houston)
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