Spaces:
Runtime error
Runtime error
File size: 2,979 Bytes
28958dc |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 |
#include <thrust/host_vector.h>
#include <thrust/device_vector.h>
#include <thrust/functional.h>
#include <thrust/gather.h>
#include <thrust/scan.h>
#include <thrust/iterator/counting_iterator.h>
#include <thrust/iterator/transform_iterator.h>
#include <iostream>
#include <iomanip>
// This example computes a summed area table using segmented scan
// http://en.wikipedia.org/wiki/Summed_area_table
// convert a linear index to a linear index in the transpose
struct transpose_index : public thrust::unary_function<size_t,size_t>
{
size_t m, n;
__host__ __device__
transpose_index(size_t _m, size_t _n) : m(_m), n(_n) {}
__host__ __device__
size_t operator()(size_t linear_index)
{
size_t i = linear_index / n;
size_t j = linear_index % n;
return m * j + i;
}
};
// convert a linear index to a row index
struct row_index : public thrust::unary_function<size_t,size_t>
{
size_t n;
__host__ __device__
row_index(size_t _n) : n(_n) {}
__host__ __device__
size_t operator()(size_t i)
{
return i / n;
}
};
// transpose an M-by-N array
template <typename T>
void transpose(size_t m, size_t n, thrust::device_vector<T>& src, thrust::device_vector<T>& dst)
{
thrust::counting_iterator<size_t> indices(0);
thrust::gather
(thrust::make_transform_iterator(indices, transpose_index(n, m)),
thrust::make_transform_iterator(indices, transpose_index(n, m)) + dst.size(),
src.begin(),
dst.begin());
}
// scan the rows of an M-by-N array
template <typename T>
void scan_horizontally(size_t n, thrust::device_vector<T>& d_data)
{
thrust::counting_iterator<size_t> indices(0);
thrust::inclusive_scan_by_key
(thrust::make_transform_iterator(indices, row_index(n)),
thrust::make_transform_iterator(indices, row_index(n)) + d_data.size(),
d_data.begin(),
d_data.begin());
}
// print an M-by-N array
template <typename T>
void print(size_t m, size_t n, thrust::device_vector<T>& d_data)
{
thrust::host_vector<T> h_data = d_data;
for(size_t i = 0; i < m; i++)
{
for(size_t j = 0; j < n; j++)
std::cout << std::setw(8) << h_data[i * n + j] << " ";
std::cout << "\n";
}
}
int main(void)
{
size_t m = 3; // number of rows
size_t n = 4; // number of columns
// 2d array stored in row-major order [(0,0), (0,1), (0,2) ... ]
thrust::device_vector<int> data(m * n, 1);
std::cout << "[step 0] initial array" << std::endl;
print(m, n, data);
std::cout << "[step 1] scan horizontally" << std::endl;
scan_horizontally(n, data);
print(m, n, data);
std::cout << "[step 2] transpose array" << std::endl;
thrust::device_vector<int> temp(m * n);
transpose(m, n, data, temp);
print(n, m, temp);
std::cout << "[step 3] scan transpose horizontally" << std::endl;
scan_horizontally(m, temp);
print(n, m, temp);
std::cout << "[step 4] transpose the transpose" << std::endl;
transpose(n, m, temp, data);
print(m, n, data);
return 0;
}
|