CUDA platform would fail if you had a GBSAOBCForce but no NonbondedForce.

platforms/cuda/src/CudaKernels.cpp

@@ -343,17 +343,17 @@ void CudaCalcGBSAOBCForceKernel::initialize(const System& system, const GBSAOBCF
 
     int numParticles = system.getNumParticles();
     _gpuContext* gpu = data.gpu;
-    vector<int> particle(numParticles);
     vector<float> radius(numParticles);
     vector<float> scale(numParticles);
+    vector<float> charge(numParticles);
     for (int i = 0; i < numParticles; i++) {
-        double charge, particleRadius, scalingFactor;
-        force.getParticleParameters(i, charge, particleRadius, scalingFactor);
-        particle[i] = i;
+        double particleCharge, particleRadius, scalingFactor;
+        force.getParticleParameters(i, particleCharge, particleRadius, scalingFactor);
         radius[i] = (float) particleRadius;
         scale[i] = (float) scalingFactor;
+        charge[i] = (float) particleCharge;
     }
-    gpuSetObcParameters(gpu, (float) force.getSoluteDielectric(), (float) force.getSolventDielectric(), particle, radius, scale);
+    gpuSetObcParameters(gpu, (float) force.getSoluteDielectric(), (float) force.getSolventDielectric(), radius, scale, charge);
 }
 
 void CudaCalcGBSAOBCForceKernel::executeForces(OpenMMContextImpl& context) {

platforms/cuda/src/kernels/gpu.cpp

@@ -425,15 +425,16 @@ void gpuSetPeriodicBoxSize(gpuContext gpu, float xsize, float ysize, float zsize
 }
 
 extern "C"
-void gpuSetObcParameters(gpuContext gpu, float innerDielectric, float solventDielectric, const vector<int>& atom, const vector<float>& radius, const vector<float>& scale)
+void gpuSetObcParameters(gpuContext gpu, float innerDielectric, float solventDielectric, const vector<float>& radius, const vector<float>& scale, const vector<float>& charge)
 {
-    unsigned int atoms = atom.size();
+    unsigned int atoms = radius.size();
 
     gpu->bIncludeGBSA = true;
     for (unsigned int i = 0; i < atoms; i++)
     {
             (*gpu->psObcData)[i].x = radius[i] - dielectricOffset;
             (*gpu->psObcData)[i].y = scale[i] * (*gpu->psObcData)[i].x;
+            (*gpu->psPosq4)[i].w = charge[i];
 
 #if (DUMP_PARAMETERS == 1)
         cout << 
@@ -453,6 +454,7 @@ void gpuSetObcParameters(gpuContext gpu, float innerDielectric, float solventDie
 
     gpu->psBornRadii->Upload();
     gpu->psObcData->Upload();
+    gpu->psPosq4->Upload();
     gpu->sim.preFactor = 2.0f*electricConstant*((1.0f/innerDielectric)-(1.0f/solventDielectric))*gpu->sim.forceConversionFactor;
 }
 

platforms/cuda/src/kernels/gputypes.h

@@ -180,7 +180,7 @@ extern "C"
 void gpuSetPeriodicBoxSize(gpuContext gpu, float xsize, float ysize, float zsize);
 
 extern "C"
-void gpuSetObcParameters(gpuContext gpu, float innerDielectric, float solventDielectric, const std::vector<int>& atom, const std::vector<float>& radius, const std::vector<float>& scale);
+void gpuSetObcParameters(gpuContext gpu, float innerDielectric, float solventDielectric, const std::vector<float>& radius, const std::vector<float>& scale, const std::vector<float>& charge);
 
 extern "C"
 void gpuSetConstraintParameters(gpuContext gpu, const std::vector<int>& atom1, const std::vector<int>& atom2, const std::vector<float>& distance,