MonteCarlo_reduction.cuh

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#ifndef MONTECARLO_REDUCTION_CUH
#define MONTECARLO_REDUCTION_CUH

#include <cooperative_groups.h>

namespace cg = cooperative_groups;

////////////////////////////////////////////////////////////////////////////////
// This function calculates total sum for each of the two input arrays.
// SUM_N must be power of two
// Unrolling provides a bit of a performance improvement for small
// to medium path counts.
////////////////////////////////////////////////////////////////////////////////

template <class T, int SUM_N, int blockSize>
__device__ void sumReduce(T *sum, T *sum2, cg::thread_block &cta,
                          cg::thread_block_tile<32> &tile32,
                          __TOptionValue *d_CallValue) {
  const int VEC = 32;
  const int tid = cta.thread_rank();

  T beta = sum[tid];
  T beta2 = sum2[tid];
  T temp, temp2;

  for (int i = VEC / 2; i > 0; i >>= 1) {
    if (tile32.thread_rank() < i) {
      temp = sum[tid + i];
      temp2 = sum2[tid + i];
      beta += temp;
      beta2 += temp2;
      sum[tid] = beta;
      sum2[tid] = beta2;
    }
    cg::sync(tile32);
  }
  cg::sync(cta);

  if (tid == 0) {
    beta = 0;
    beta2 = 0;
    for (int i = 0; i < blockDim.x; i += VEC) {
      beta += sum[i];
      beta2 += sum2[i];
    }
    __TOptionValue t = {beta, beta2};
    *d_CallValue = t;
  }
  cg::sync(cta);
}

#endif