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revise logic and documentation of communication cutoff selection one more time

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This commit is contained in:
Axel Kohlmeyer
2019-07-25 16:00:01 -04:00
parent 183d92cad7
commit fe83e4de2e
2 changed files with 50 additions and 30 deletions
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59
src/comm.cpp
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@ -588,30 +588,42 @@ void Comm::set_proc_grid(int outflag)
/* ----------------------------------------------------------------------
determine suitable communication cutoff.
use the larger of the user specified value and the cutoff required
by the neighborlist build for pair styles.
if bonded interactions exist, apply a heuristic based on the equilibrium
bond length (use 1.5x r_bond if no dihedral or improper style exists
otherwise 2x r_bond) plus neighbor list skin.
if no user specified communication cutoff is given include this
heuristic, otherwise ignore it.
this uses three inputs: 1) maximum neighborlist cutoff, 2) an estimate
based on bond lengths and bonded interaction styles present, and 3) a
user supplied communication cutoff.
the neighbor list cutoff (1) is *always* used, since it is a requirement
for neighborlists working correctly. the bond length based cutoff is
*only* used, if no pair style is defined and no user cutoff is provided.
otherwise, a warning is printed. if the bond length based estimate is
larger than what is used.
print a warning, if a user specified communication cutoff is overridden.
------------------------------------------------------------------------- */
double Comm::get_comm_cutoff()
{
double maxcommcutoff = 0.0;
double maxbondcutoff = 0.0;
double maxcommcutoff, maxbondcutoff = 0.0;
if (force->bond) {
int n = atom->nbondtypes;
for (int i = 1; i <= n; ++i)
maxbondcutoff = MAX(maxbondcutoff,force->bond->equilibrium_distance(i));
if (force->dihedral || force->improper) {
maxbondcutoff *= 2.0;
// apply bond length based heuristics.
if (force->newton_bond) {
if (force->dihedral || force->improper) {
maxbondcutoff *= 2.25;
} else {
maxbondcutoff *=1.5;
}
} else {
maxbondcutoff *=1.5;
if (force->dihedral || force->improper) {
maxbondcutoff *= 3.125;
} else if (force->angle) {
maxbondcutoff *= 2.25;
} else {
maxbondcutoff *=1.5;
}
}
maxbondcutoff += neighbor->skin;
}
@ -620,16 +632,27 @@ double Comm::get_comm_cutoff()
maxcommcutoff = MAX(cutghostuser,neighbor->cutneighmax);
// consider cutoff estimate from bond length only if no user specified cutoff
// use cutoff estimate from bond length only if no user specified
// cutoff was given and no pair style present. Otherwise print a
// warning, if the estimated bond based cutoff is larger than what
// is currently used.
if (cutghostuser == 0.0) maxcommcutoff = MAX(maxcommcutoff,maxbondcutoff);
if (!force->pair && (cutghostuser == 0.0)) {
maxcommcutoff = MAX(maxcommcutoff,maxbondcutoff);
} else {
if ((me == 0) && (maxbondcutoff > maxcommcutoff)) {
char mesg[256];
snprintf(mesg,256,"Communication cutoff %g is shorter than a bond "
"length based estimate of %g. This may lead to errors.",
maxcommcutoff,maxbondcutoff);
error->warning(FLERR,mesg);
}
}
// print warning if neighborlist cutoff overrides user cutoff or
// applied bond based cutoff is larger than neighbor cutoff.
// print warning if neighborlist cutoff overrides user cutoff
if (me == 0) {
if ( ((cutghostuser > 0.0) && (maxcommcutoff > cutghostuser))
|| ((cutghostuser == 0.0) && (maxcommcutoff == maxbondcutoff)) ) {
if ((cutghostuser > 0.0) && (maxcommcutoff > cutghostuser)) {
char mesg[128];
snprintf(mesg,128,"Communication cutoff adjusted to %g",maxcommcutoff);
error->warning(FLERR,mesg);