Merge pull request #566 from peastman/master

Fix crash with empty interaction groups

platforms/cuda/src/CudaKernels.cpp

@@ -2072,6 +2072,8 @@ void CudaCalcCustomNonbondedForceKernel::initInteractionGroups(const CustomNonbo
         // Find how many tiles we will create for this group.
         
         int tileWidth = min(min(32, (int) atoms1.size()), (int) atoms2.size());
+        if (tileWidth == 0)
+            continue;
         int numBlocks1 = (atoms1.size()+tileWidth-1)/tileWidth;
         int numBlocks2 = (atoms2.size()+tileWidth-1)/tileWidth;
         

platforms/opencl/src/OpenCLKernels.cpp

@@ -2082,6 +2082,8 @@ void OpenCLCalcCustomNonbondedForceKernel::initInteractionGroups(const CustomNon
         // Find how many tiles we will create for this group.
         
         int tileWidth = min(min(32, (int) atoms1.size()), (int) atoms2.size());
+        if (tileWidth == 0)
+            continue;
         int numBlocks1 = (atoms1.size()+tileWidth-1)/tileWidth;
         int numBlocks2 = (atoms2.size()+tileWidth-1)/tileWidth;