Update based on code review

platforms/cuda/src/CudaExpressionUtilities.cpp

@@ -124,17 +124,17 @@ void CudaExpressionUtilities::processExpression(stringstream& out, const Express
                     if (argIndex == -1)
                         out << nodeNames[j] << " = RECIP(periodicDistance_rinv);\n";
                     else if (argIndex == 0)
-                        out << nodeNames[j] << " = periodicDistance_delta.x*periodicDistance_rinv*(periodicDistance_r2>0);\n";
+                        out << nodeNames[j] << " = (periodicDistance_r2 > 0 ? periodicDistance_delta.x*periodicDistance_rinv : 0);\n";
                     else if (argIndex == 1)
-                        out << nodeNames[j] << " = periodicDistance_delta.y*periodicDistance_rinv*(periodicDistance_r2>0);\n";
+                        out << nodeNames[j] << " = (periodicDistance_r2 > 0 ? periodicDistance_delta.y*periodicDistance_rinv : 0);\n";
                     else if (argIndex == 2)
-                        out << nodeNames[j] << " = periodicDistance_delta.z*periodicDistance_rinv*(periodicDistance_r2>0);\n";
+                        out << nodeNames[j] << " = (periodicDistance_r2 > 0 ? periodicDistance_delta.z*periodicDistance_rinv : 0);\n";
                     else if (argIndex == 3)
-                        out << nodeNames[j] << " = -periodicDistance_delta.x*periodicDistance_rinv*(periodicDistance_r2>0);\n";
+                        out << nodeNames[j] << " = (periodicDistance_r2 > 0 ? -periodicDistance_delta.x*periodicDistance_rinv : 0);\n";
                     else if (argIndex == 4)
-                        out << nodeNames[j] << " = -periodicDistance_delta.y*periodicDistance_rinv*(periodicDistance_r2>0);\n";
+                        out << nodeNames[j] << " = (periodicDistance_r2 > 0 ? -periodicDistance_delta.y*periodicDistance_rinv : 0);\n";
                     else if (argIndex == 5)
-                        out << nodeNames[j] << " = -periodicDistance_delta.z*periodicDistance_rinv*(periodicDistance_r2>0);\n";
+                        out << nodeNames[j] << " = (periodicDistance_r2 > 0 ? -periodicDistance_delta.z*periodicDistance_rinv : 0);\n";
                 }
             }
             else {

platforms/opencl/src/OpenCLExpressionUtilities.cpp

@@ -124,17 +124,17 @@ void OpenCLExpressionUtilities::processExpression(stringstream& out, const Expre
                     if (argIndex == -1)
                         out << nodeNames[j] << " = RECIP(periodicDistance_rinv);\n";
                     else if (argIndex == 0)
-                        out << nodeNames[j] << " = periodicDistance_delta.x*periodicDistance_rinv*(periodicDistance_r2>0);\n";
+                        out << nodeNames[j] << " = (periodicDistance_r2 > 0 ? periodicDistance_delta.x*periodicDistance_rinv : 0);\n";
                     else if (argIndex == 1)
-                        out << nodeNames[j] << " = periodicDistance_delta.y*periodicDistance_rinv*(periodicDistance_r2>0);\n";
+                        out << nodeNames[j] << " = (periodicDistance_r2 > 0 ? periodicDistance_delta.y*periodicDistance_rinv : 0);\n";
                     else if (argIndex == 2)
-                        out << nodeNames[j] << " = periodicDistance_delta.z*periodicDistance_rinv*(periodicDistance_r2>0);\n";
+                        out << nodeNames[j] << " = (periodicDistance_r2 > 0 ? periodicDistance_delta.z*periodicDistance_rinv : 0);\n";
                     else if (argIndex == 3)
-                        out << nodeNames[j] << " = -periodicDistance_delta.x*periodicDistance_rinv*(periodicDistance_r2>0);\n";
+                        out << nodeNames[j] << " = (periodicDistance_r2 > 0 ? -periodicDistance_delta.x*periodicDistance_rinv : 0);\n";
                     else if (argIndex == 4)
-                        out << nodeNames[j] << " = -periodicDistance_delta.y*periodicDistance_rinv*(periodicDistance_r2>0);\n";
+                        out << nodeNames[j] << " = (periodicDistance_r2 > 0 ? -periodicDistance_delta.y*periodicDistance_rinv : 0);\n";
                     else if (argIndex == 5)
-                        out << nodeNames[j] << " = -periodicDistance_delta.z*periodicDistance_rinv*(periodicDistance_r2>0);\n";
+                        out << nodeNames[j] << " = (periodicDistance_r2 > 0 ? -periodicDistance_delta.z*periodicDistance_rinv : 0);\n";
                 }
             }
             else {

tests/TestCustomExternalForce.h

@@ -167,7 +167,7 @@ void testPeriodic() {
     }
 }
 
-void testGithub1191() {
+void testZeroPeriodicDistance() {
     Vec3 vx(5, 0, 0);
     Vec3 vy(0, 6, 0);
     Vec3 vz(1, 2, 7);
@@ -224,7 +224,7 @@ int main(int argc, char* argv[]) {
         testForce();
         testManyParameters();
         testPeriodic();
-        testGithub1191();
+        testZeroPeriodicDistance();
         testIllegalVariable();
         runPlatformTests();
     }