From 1bb9bf1e629070325e761efe926d69e6e1ca087d Mon Sep 17 00:00:00 2001 From: sjplimp Date: Wed, 20 Aug 2008 22:23:13 +0000 Subject: [PATCH] git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@2086 f3b2605a-c512-4ea7-a41b-209d697bcdaa --- doc/kspace_modify.html | 15 ++++++++++++++- doc/kspace_modify.txt | 15 ++++++++++++++- doc/kspace_style.html | 3 +++ doc/kspace_style.txt | 3 +++ 4 files changed, 34 insertions(+), 2 deletions(-) diff --git a/doc/kspace_modify.html b/doc/kspace_modify.html index 71d2c54176..942174cf05 100644 --- a/doc/kspace_modify.html +++ b/doc/kspace_modify.html @@ -51,7 +51,20 @@ Values for x,y,z of 0,0,0 unset the option.

The order keyword determines how many grid spacings an atom's charge extends when it is mapped to the FFT grid in kspace style pppm. The default for this parameter is 5, which means each charge spans 5 grid -cells in each dimension. +cells in each dimension. The larger the value of this parameter, the +smaller the FFT grid will need to be to achieve the requested +precision. Conversely, the smaller the order value, the larger the +grid will be. Note that there is an inherent trade-off involved: a +small grid will lower the cost of FFTs, but a large order parameter +will increase the cost of intepolating charge/fields to/from the grid. +And vice versa. +

+

The order parameter may be reset by LAMMPS when it sets up the PPPM +FFT grid if the implied grid stencil extends beyond the grid cells +owned by neighboring processors. Typically this will only occur when +small problems are run on large numbers of processors. A warning will +be generated indicating the order parameter is being reduced to allow +LAMMPS to run the problem.

The gewald keyword sets the value of the PPPM G-ewald parameter. Without this setting, LAMMPS chooses the parameter automatically as a diff --git a/doc/kspace_modify.txt b/doc/kspace_modify.txt index e5a29cc5af..4e141827a0 100644 --- a/doc/kspace_modify.txt +++ b/doc/kspace_modify.txt @@ -45,7 +45,20 @@ Values for x,y,z of 0,0,0 unset the option. The {order} keyword determines how many grid spacings an atom's charge extends when it is mapped to the FFT grid in kspace style pppm. The default for this parameter is 5, which means each charge spans 5 grid -cells in each dimension. +cells in each dimension. The larger the value of this parameter, the +smaller the FFT grid will need to be to achieve the requested +precision. Conversely, the smaller the order value, the larger the +grid will be. Note that there is an inherent trade-off involved: a +small grid will lower the cost of FFTs, but a large order parameter +will increase the cost of intepolating charge/fields to/from the grid. +And vice versa. + +The order parameter may be reset by LAMMPS when it sets up the PPPM +FFT grid if the implied grid stencil extends beyond the grid cells +owned by neighboring processors. Typically this will only occur when +small problems are run on large numbers of processors. A warning will +be generated indicating the order parameter is being reduced to allow +LAMMPS to run the problem. The {gewald} keyword sets the value of the PPPM G-ewald parameter. Without this setting, LAMMPS chooses the parameter automatically as a diff --git a/doc/kspace_style.html b/doc/kspace_style.html index ec9ae95fa4..992205e792 100644 --- a/doc/kspace_style.html +++ b/doc/kspace_style.html @@ -85,6 +85,9 @@ used in conjunction with the pairwise cutoff to determine the number of K-space vectors for style ewald or the FFT grid size for style pppm.

+

See the kspace_modify command for additional +options of the K-space solvers that can be set. +

Restrictions:

A simulation must be 3d and periodic in all dimensions to use an Ewald diff --git a/doc/kspace_style.txt b/doc/kspace_style.txt index 575f33c1e9..a4c45269dc 100644 --- a/doc/kspace_style.txt +++ b/doc/kspace_style.txt @@ -80,6 +80,9 @@ used in conjunction with the pairwise cutoff to determine the number of K-space vectors for style {ewald} or the FFT grid size for style {pppm}. +See the "kspace_modify"_kspace_modify.html command for additional +options of the K-space solvers that can be set. + [Restrictions:] A simulation must be 3d and periodic in all dimensions to use an Ewald