Fixed error in barostats (#4049)

openmmapi/src/MonteCarloAnisotropicBarostatImpl.cpp

@@ -120,8 +120,8 @@ void MonteCarloAnisotropicBarostatImpl::updateContextState(ContextImpl& context)
     if (w > 0 && SimTKOpenMMUtilities::getUniformlyDistributedRandomNumber() > exp(-w/kT)) {
         // Reject the step.
         
-        kernel.getAs<ApplyMonteCarloBarostatKernel>().restoreCoordinates(context);
         context.getOwner().setPeriodicBoxVectors(box[0], box[1], box[2]);
+        kernel.getAs<ApplyMonteCarloBarostatKernel>().restoreCoordinates(context);
     }
     else
         numAccepted[axis]++;

openmmapi/src/MonteCarloBarostatImpl.cpp

@@ -90,8 +90,8 @@ void MonteCarloBarostatImpl::updateContextState(ContextImpl& context, bool& forc
     if (w > 0 && SimTKOpenMMUtilities::getUniformlyDistributedRandomNumber() > exp(-w/kT)) {
         // Reject the step.
 
-        kernel.getAs<ApplyMonteCarloBarostatKernel>().restoreCoordinates(context);
         context.getOwner().setPeriodicBoxVectors(box[0], box[1], box[2]);
+        kernel.getAs<ApplyMonteCarloBarostatKernel>().restoreCoordinates(context);
     }
     else {
         numAccepted++;

openmmapi/src/MonteCarloFlexibleBarostatImpl.cpp

@@ -115,8 +115,8 @@ void MonteCarloFlexibleBarostatImpl::updateContextState(ContextImpl& context, bo
     if (w > 0 && SimTKOpenMMUtilities::getUniformlyDistributedRandomNumber() > exp(-w/kT)) {
         // Reject the step.
 
-        kernel.getAs<ApplyMonteCarloBarostatKernel>().restoreCoordinates(context);
         context.getOwner().setPeriodicBoxVectors(box[0], box[1], box[2]);
+        kernel.getAs<ApplyMonteCarloBarostatKernel>().restoreCoordinates(context);
     }
     else {
         numAccepted++;

openmmapi/src/MonteCarloMembraneBarostatImpl.cpp

@@ -121,8 +121,8 @@ void MonteCarloMembraneBarostatImpl::updateContextState(ContextImpl& context) {
     if (w > 0 && SimTKOpenMMUtilities::getUniformlyDistributedRandomNumber() > exp(-w/kT)) {
         // Reject the step.
         
-        kernel.getAs<ApplyMonteCarloBarostatKernel>().restoreCoordinates(context);
         context.getOwner().setPeriodicBoxVectors(box[0], box[1], box[2]);
+        kernel.getAs<ApplyMonteCarloBarostatKernel>().restoreCoordinates(context);
     }
     else
         numAccepted[axis]++;

platforms/common/src/CommonKernels.cpp

@@ -7781,13 +7781,13 @@ void CommonApplyMonteCarloBarostatKernel::scaleCoordinates(ContextImpl& context,
     cc.getLongForceBuffer().copyTo(savedLongForces);
     if (savedFloatForces.isInitialized())
         cc.getFloatForceBuffer().copyTo(savedFloatForces);
+    lastPosCellOffsets = cc.getPosCellOffsets();
     kernel->setArg(0, (float) scaleX);
     kernel->setArg(1, (float) scaleY);
     kernel->setArg(2, (float) scaleZ);
     setPeriodicBoxArgs(cc, kernel, 4);
     kernel->execute(cc.getNumAtoms());
     lastAtomOrder = cc.getAtomIndex();
-    lastPosCellOffsets = cc.getPosCellOffsets();
 }
 
 void CommonApplyMonteCarloBarostatKernel::restoreCoordinates(ContextImpl& context) {