Fix precision issue in MTSIntegrator

283b1acd · John Chodera (MSKCC) · 69d5e8b8 · 283b1acd
Commit 283b1acd authored Oct 06, 2016 by John Chodera (MSKCC)
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Showing with 3 additions and 2 deletions

wrappers/python/simtk/openmm/mtsintegrator.py wrappers/python/simtk/openmm/mtsintegrator.py +3 -2

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--- a/wrappers/python/simtk/openmm/mtsintegrator.py
+++ b/wrappers/python/simtk/openmm/mtsintegrator.py
@@ -98,10 +98,11 @@ class MTSIntegrator(CustomIntegrator):
        for i in range(stepsPerParentStep):
            self.addComputePerDof("v", "v+0.5*(dt/"+str(substeps)+")*f"+str(group)+"/m")
            if len(groups) == 1:
-                self.addComputePerDof("x1", "x")
                self.addComputePerDof("x", "x+(dt/"+str(substeps)+")*v")
+                self.addComputePerDof("x1", "x")
                self.addConstrainPositions();
-                self.addComputePerDof("v", "(x-x1)/(dt/"+str(substeps)+")");
+                self.addComputePerDof("v", "v+(x-x1)/(dt/"+str(substeps)+")");
+                self.addConstrainVelocities()
            else:
                self._createSubsteps(substeps, groups[1:])
            self.addComputePerDof("v", "v+0.5*(dt/"+str(substeps)+")*f"+str(group)+"/m")