   {
     // Run fa2 spring embedding kernel.
     startCudaTimer(&timerIteration);
-
-    cudaMemset(graphSwing, 0, sizeof(float));
-    cudaMemset(graphTract, 0, sizeof(float));
-
-    // Run reductions on vertex swing and traction.
-    startCudaTimer(&timer);
-    fa2GraphSwingTract<<<numblocks_reduction, BLOCK_SIZE>>>(
-        g->numvertices,
-        swg, tra, numNeighbours,
-        graphSwing, graphTract);
-    stopCudaTimer(&timer);
-    printf("time: graph swing and traction.\n");
-    printCudaTimer(&timer);
-    resetCudaTimer(&timer);
-
-    cudaError_t code = cudaGetLastError();
-    if (code != cudaSuccess)
-    {
-      printf("Error in kernel 1.\n%s\n", cudaGetErrorString(code));
-      exit(EXIT_FAILURE);
-    }
 
     // Compute graph speed, vertex forces, speed and displacement.
     startCudaTimer(&timer);

    unsigned int numedges,
    unsigned int* numNeighbours,
    float* tra, float* swg, 
    float* oldForceX, float* oldForceY,
    float* graphSwing,
    float* graphTract,

    printf("time: all forces and moving vertices.\n");
    printCudaTimer(&timer);
    resetCudaTimer(&timer);
    cudaError_t code = cudaGetLastError();
    if (code != cudaSuccess)
    {
      printf("Error in kernel 2.\n%s\n", cudaGetErrorString(code));
