From: Szilard Pall Date: Thu, 26 Apr 2012 11:54:37 +0000 (+0200) Subject: Corrected fourierspacing description X-Git-Url: http://biod.pnpi.spb.ru/gitweb/?a=commitdiff_plain;h=0b2d41f18a24f02ff07843f41376defec74a7aa9;p=alexxy%2Fgromacs.git Corrected fourierspacing description Change-Id: I5cb577f0750cea3481f766330096d5b2bca7eb6f --- diff --git a/share/html/online/mdp_opt.html b/share/html/online/mdp_opt.html index caf9cc6631..170cf9478d 100644 --- a/share/html/online/mdp_opt.html +++ b/share/html/online/mdp_opt.html @@ -727,13 +727,14 @@ energy group pairs.

Ewald

fourierspacing: (0.12) [nm]
-
The maximum grid spacing for the FFT grid when using PPPM or PME. -For ordinary Ewald the spacing times the box dimensions determines the -highest magnitude to use in each direction. In all cases -each direction can be overridden by entering a non-zero value for -fourier_n[xyz]. +
For ordinary Ewald, the ratio of the box dimensions and the spacing +determines a lower bound for the number of wave vectors to use in each +(signed) direction. For PME and PPPM, that ratio determines a lower bound +for the number of Fourier-space grid points that will be used along that +axis. In all cases, the number for each direction can be overridden by +entering a non-zero value for fourier_n[xyz]. For optimizing the relative load of the particle-particle interactions -and the mesh part of PME it is useful to know that +and the mesh part of PME, it is useful to know that the accuracy of the electrostatics remains nearly constant when the Coulomb cut-off and the PME grid spacing are scaled by the same factor.