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#include <thrust/device_vector.h>
#include <thrust/copy.h>
#include <thrust/iterator/constant_iterator.h>
#include <thrust/reduce.h>
#include <iostream>
#include <iterator>
// This example computes a run-length code [1] for an array of characters.
//
// [1] http://en.wikipedia.org/wiki/Run-length_encoding
int main(void)
{
// input data on the host
const char data[] = "aaabbbbbcddeeeeeeeeeff";
const size_t N = (sizeof(data) / sizeof(char)) - 1;
// copy input data to the device
thrust::device_vector<char> input(data, data + N);
// allocate storage for output data and run lengths
thrust::device_vector<char> output(N);
thrust::device_vector<int> lengths(N);
// print the initial data
std::cout << "input data:" << std::endl;
thrust::copy(input.begin(), input.end(), std::ostream_iterator<char>(std::cout, ""));
std::cout << std::endl << std::endl;
// compute run lengths
size_t num_runs = thrust::reduce_by_key
(input.begin(), input.end(), // input key sequence
thrust::constant_iterator<int>(1), // input value sequence
output.begin(), // output key sequence
lengths.begin() // output value sequence
).first - output.begin(); // compute the output size
// print the output
std::cout << "run-length encoded output:" << std::endl;
for(size_t i = 0; i < num_runs; i++)
std::cout << "(" << output[i] << "," << lengths[i] << ")";
std::cout << std::endl;
return 0;
}
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