thrust_test.cu

#include <thrust/version.h>
#include <thrust/device_vector.h>
#include <thrust/host_vector.h>
#include <thrust/binary_search.h>
#include <thrust/copy.h>

#define STENCIL_SIZE 8000000
#define STENCIL_TRUE_LOCATIONS 32

struct is_true
  {
    __host__ __device__
    bool operator()(const bool x)
    {
      return x;
    }
  };

int main()
{
  //allocate stencil
  thrust::host_vector<bool> hv(STENCIL_SIZE,false);

  size_t stencil_locations[STENCIL_TRUE_LOCATIONS] = {467508,
						  1326441,
						  1541662,
						  1679866,
						  2234773,
						  2387355,
						  2653762,
						  3159732,
						  3226888,
						  3828014,
						  3887644,
						  3909417,
						  3924245,
						  4042273,
						  4150580,
						  4233776,
						  4425058,
						  4446033,
						  4484984,
						  4565655,
						  4629464,
						  4703190,
						  4836990,
						  4903165,
						  4910365,
						  5328271,
						  5483482,
						  5755194,
						  5781566,
						  5966710,
						  5987753,
						  7870669};

  for (size_t i=0;i<STENCIL_TRUE_LOCATIONS;i++)
  	hv[stencil_locations[i]] = true;

  //copy stencil to GPU
  thrust::device_vector<bool> dv = hv;

  //FIRST METHOD: inclusive_scan / upper_bound
  thrust::device_vector<size_t> dscanned(STENCIL_SIZE);

  thrust::inclusive_scan(dv.begin(), dv.end(), dscanned.begin());
                
  thrust::counting_iterator<size_t> count_it(0);

  //dindices will have the locations of the 'true' values of the stencil
  thrust::device_vector<size_t> dindices1(STENCIL_TRUE_LOCATIONS);

  thrust::upper_bound(dscanned.begin(),dscanned.end(),count_it,count_it+STENCIL_TRUE_LOCATIONS,dindices1.begin());

  //copy back to host
  thrust::host_vector<size_t> hindices1 = dindices1;

  //SECOND METHOD: copy_if
  thrust::device_vector<size_t> dindices2(STENCIL_TRUE_LOCATIONS);
  thrust::copy_if(count_it, count_it+STENCIL_SIZE, dv.begin(), dindices2.begin(), is_true());

  //copy back to host
  thrust::host_vector<size_t> hindices2 = dindices2;

  for (size_t i=0;i<STENCIL_TRUE_LOCATIONS;i++)
  {
  	printf("i: %2u stencil_location: %8u hindices1: %8u hindices2: %8u\n",i,stencil_locations[i],hindices1[i],hindices2[i]);
  }

  printf("done\n");

  return 0;
}