From 91993b236d52dbc9e75c9f7c45cf1438d14c51cc Mon Sep 17 00:00:00 2001
From: Axel Kohlmeyer <akohlmey@gmail.com>
Date: Fri, 5 Jan 2018 19:52:51 -0500
Subject: [PATCH] avoid division by zero in PPPM for empty and uncharged
systems. require kspace_modify gewald
---
src/KOKKOS/pppm_kokkos.cpp | 3 +++
src/KSPACE/pppm.cpp | 3 +++
2 files changed, 6 insertions(+)
diff --git a/src/KOKKOS/pppm_kokkos.cpp b/src/KOKKOS/pppm_kokkos.cpp
index cf6e2814c0..03de42c68c 100644
--- a/src/KOKKOS/pppm_kokkos.cpp
+++ b/src/KOKKOS/pppm_kokkos.cpp
@@ -969,6 +969,8 @@ void PPPMKokkos<DeviceType>::set_grid_global()
if (!gewaldflag) {
if (accuracy <= 0.0)
error->all(FLERR,"KSpace accuracy must be > 0");
+ if (q2 == 0.0)
+ error->all(FLERR,"Must use 'kspace_modify gewald' for uncharged system");
g_ewald = accuracy*sqrt(natoms*cutoff*xprd*yprd*zprd) / (2.0*q2);
if (g_ewald >= 1.0) g_ewald = (1.35 - 0.15*log(accuracy))/cutoff;
else g_ewald = sqrt(-log(g_ewald)) / cutoff;
@@ -1179,6 +1181,7 @@ double PPPMKokkos<DeviceType>::final_accuracy()
double yprd = domain->yprd;
double zprd = domain->zprd;
bigint natoms = atomKK->natoms;
+ if (natoms == 0) natoms = 1; // avoid division by zero
double df_kspace = compute_df_kspace();
double q2_over_sqrt = q2 / sqrt(natoms*cutoff*xprd*yprd*zprd);
diff --git a/src/KSPACE/pppm.cpp b/src/KSPACE/pppm.cpp
index 28dda4abfc..53ab2e5a9d 100644
--- a/src/KSPACE/pppm.cpp
+++ b/src/KSPACE/pppm.cpp
@@ -1004,6 +1004,8 @@ void PPPM::set_grid_global()
if (!gewaldflag) {
if (accuracy <= 0.0)
error->all(FLERR,"KSpace accuracy must be > 0");
+ if (q2 == 0.0)
+ error->all(FLERR,"Must use kspace_modify gewald for uncharged system");
g_ewald = accuracy*sqrt(natoms*cutoff*xprd*yprd*zprd) / (2.0*q2);
if (g_ewald >= 1.0) g_ewald = (1.35 - 0.15*log(accuracy))/cutoff;
else g_ewald = sqrt(-log(g_ewald)) / cutoff;
@@ -1346,6 +1348,7 @@ double PPPM::final_accuracy()
double yprd = domain->yprd;
double zprd = domain->zprd;
bigint natoms = atom->natoms;
+ if (natoms == 0) natoms = 1; // avoid division by zero
double df_kspace = compute_df_kspace();
double q2_over_sqrt = q2 / sqrt(natoms*cutoff*xprd*yprd*zprd);
--
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