Merge pull request #787 from peastman/step

Variable step size integrators were scaling the step size incorrectly

platforms/cuda/src/kernels/langevin.cu

@@ -90,7 +90,7 @@ extern "C" __global__ void selectLangevinStepSize(int numAtoms, int paddedNumAto
     while (index < numAtoms) {
         mixed3 f = make_mixed3(scale*force[index], scale*force[index+paddedNumAtoms], scale*force[index+paddedNumAtoms*2]);
         mixed invMass = velm[index].w;
-        err += (f.x*f.x + f.y*f.y + f.z*f.z)*invMass;
+        err += (f.x*f.x + f.y*f.y + f.z*f.z)*invMass*invMass;
         index += blockDim.x*gridDim.x;
     }
     error[threadIdx.x] = err;

platforms/cuda/src/kernels/verlet.cu

@@ -89,7 +89,7 @@ extern "C" __global__ void selectVerletStepSize(int numAtoms, int paddedNumAtoms
     for (int index = threadIdx.x; index < numAtoms; index += blockDim.x*gridDim.x) {
         mixed3 f = make_mixed3(scale*force[index], scale*force[index+paddedNumAtoms], scale*force[index+paddedNumAtoms*2]);
         mixed invMass = velm[index].w;
-        err += (f.x*f.x + f.y*f.y + f.z*f.z)*invMass;
+        err += (f.x*f.x + f.y*f.y + f.z*f.z)*invMass*invMass;
     }
     error[threadIdx.x] = err;
     __syncthreads();

platforms/opencl/src/kernels/langevin.cl

@@ -81,7 +81,7 @@ __kernel void selectLangevinStepSize(mixed maxStepSize, mixed errorTol, mixed ta
     while (index < NUM_ATOMS) {
         real4 f = force[index];
         mixed invMass = velm[index].w;
-        err += (f.x*f.x + f.y*f.y + f.z*f.z)*invMass;
+        err += (f.x*f.x + f.y*f.y + f.z*f.z)*invMass*invMass;
         index += get_global_size(0);
     }
     error[get_local_id(0)] = err;

platforms/opencl/src/kernels/verlet.cl

@@ -85,7 +85,7 @@ __kernel void selectVerletStepSize(int numAtoms, mixed maxStepSize, mixed errorT
     while (index < numAtoms) {
         real4 f = force[index];
         mixed invMass = velm[index].w;
-        err += (f.x*f.x + f.y*f.y + f.z*f.z)*invMass;
+        err += (f.x*f.x + f.y*f.y + f.z*f.z)*invMass*invMass;
         index += get_global_size(0);
     }
     error[get_local_id(0)] = err;