RNG seed mods for LangevinIntegrator

platforms/cuda/src/CudaKernels.cpp

@@ -414,6 +414,15 @@ CudaIntegrateLangevinStepKernel::~CudaIntegrateLangevinStepKernel() {
 
 void CudaIntegrateLangevinStepKernel::initialize(const System& system, const LangevinIntegrator& integrator) {
     initializeIntegration(system, data, integrator);
+
+    // if LangevinIntegrator seed does not equal default value or is less than/equal to 0, then 
+    // set gpu seed and redo random values
+
+    if( integrator.getRandomNumberSeed() < 1 ){
+       _gpuContext* gpu = data.gpu;
+       gpu->seed        = static_cast<unsigned long>( integrator.getRandomNumberSeed() );
+       gpuInitializeRandoms( gpu );
+    }
     prevStepSize = -1.0;
 }