Merge pull request #244 from peastman/master

Reference implementation of AndersenThermostat did not handle massless particles correctly

Merge pull request #244 from peastman/master
Reference implementation of AndersenThermostat did not handle massless particles correctly
306d1bb0 · peastman · 0865043e · 8d062ebb · 306d1bb0
Commit 306d1bb0 authored Dec 12, 2013 by peastman
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platforms/reference/src/SimTKReference/ReferenceAndersenThermostat.cpp ...erence/src/SimTKReference/ReferenceAndersenThermostat.cpp +6 -4

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--- a/platforms/reference/src/SimTKReference/ReferenceAndersenThermostat.cpp
+++ b/platforms/reference/src/SimTKReference/ReferenceAndersenThermostat.cpp
@@ -72,10 +72,12 @@ using OpenMM::RealVec;

                  for (int j = 0; j < (int) atomGroups[i].size(); j++) {
                      int atom = atomGroups[i][j];
-                      const RealOpenMM velocityScale = static_cast<RealOpenMM>(sqrt(BOLTZ*temperature/atomMasses[atom]));
-                      atomVelocities[atom][0] = velocityScale*SimTKOpenMMUtilities::getNormallyDistributedRandomNumber();
-                      atomVelocities[atom][1] = velocityScale*SimTKOpenMMUtilities::getNormallyDistributedRandomNumber();
-                      atomVelocities[atom][2] = velocityScale*SimTKOpenMMUtilities::getNormallyDistributedRandomNumber();
+                      if (atomMasses[atom] != 0) {
+                          const RealOpenMM velocityScale = static_cast<RealOpenMM>(sqrt(BOLTZ*temperature/atomMasses[atom]));
+                          atomVelocities[atom][0] = velocityScale*SimTKOpenMMUtilities::getNormallyDistributedRandomNumber();
+                          atomVelocities[atom][1] = velocityScale*SimTKOpenMMUtilities::getNormallyDistributedRandomNumber();
+                          atomVelocities[atom][2] = velocityScale*SimTKOpenMMUtilities::getNormallyDistributedRandomNumber();
+                      }
                  }
              }
          }