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#include <thrust/binary_search.h>
#include <thrust/copy.h>
#include <thrust/device_vector.h>
#include <thrust/gather.h>
#include <thrust/iterator/counting_iterator.h>
#include <thrust/scan.h>
#include <iostream>
#include <iterator>
// This example decodes a run-length code [1] for an array of characters.
//
// [1] http://en.wikipedia.org/wiki/Run-length_encoding
int main()
{
// allocate storage for compressed input and run lengths
thrust::device_vector<char> input(6);
thrust::device_vector<int> lengths(6);
// clang-format off
input[0] = 'a'; lengths[0] = 3;
input[1] = 'b'; lengths[1] = 5;
input[2] = 'c'; lengths[2] = 1;
input[3] = 'd'; lengths[3] = 2;
input[4] = 'e'; lengths[4] = 9;
input[5] = 'f'; lengths[5] = 2;
// clang-format on
// print the initial data
std::cout << "run-length encoded input:" << std::endl;
for (size_t i = 0; i < 6; i++)
{
std::cout << "(" << input[i] << "," << lengths[i] << ")";
}
std::cout << std::endl << std::endl;
// scan the lengths
thrust::inclusive_scan(lengths.begin(), lengths.end(), lengths.begin());
// output size is sum of the run lengths
int N = lengths.back();
// compute input index for each output element
thrust::device_vector<int> indices(N);
thrust::lower_bound(
lengths.begin(),
lengths.end(),
thrust::counting_iterator<int>(1),
thrust::counting_iterator<int>(N + 1),
indices.begin());
// gather input elements
thrust::device_vector<char> output(N);
thrust::gather(indices.begin(), indices.end(), input.begin(), output.begin());
// print the initial data
std::cout << "decoded output:" << std::endl;
thrust::copy(output.begin(), output.end(), std::ostream_iterator<char>(std::cout, ""));
std::cout << std::endl;
return 0;
}
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