63 lines
1.7 KiB
C++
63 lines
1.7 KiB
C++
// This program demonstrates how to perform parallel exclusive scan.
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#include <taskflow/taskflow.hpp>
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#include <taskflow/algorithm/scan.hpp>
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int main(int argc, char* argv[]) {
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if(argc != 3) {
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std::cerr << "usage: ./exclusive_scan num_workers num_elements\n";
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std::exit(EXIT_FAILURE);
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}
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size_t W = std::atoi(argv[1]);
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size_t N = std::atoi(argv[2]);
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tf::Executor executor(W);
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tf::Taskflow taskflow;
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std::vector<int> elements(N), scan_seq(N), scan_par(N);
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for(size_t i=0; i<N; i++) {
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elements[i] = static_cast<int>(i);
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}
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// sequential exclusive scan
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{
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std::cout << "sequential exclusive scan ... ";
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auto beg = std::chrono::steady_clock::now();
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std::exclusive_scan(
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elements.begin(), elements.end(), scan_seq.begin(), -1, std::plus<int>{}
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);
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auto end = std::chrono::steady_clock::now();
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std::cout << std::chrono::duration_cast<std::chrono::nanoseconds>(end-beg).count()
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<< "ns\n";
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}
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// create a parallel exclusive scan task
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{
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std::cout << "parallel exclusive scan ... ";
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auto beg = std::chrono::steady_clock::now();
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taskflow.exclusive_scan(
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elements.begin(), elements.end(), scan_par.begin(), -1, std::plus<int>{}
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);
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executor.run(taskflow).wait();
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auto end = std::chrono::steady_clock::now();
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std::cout << std::chrono::duration_cast<std::chrono::nanoseconds>(end-beg).count()
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<< "ns\n";
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}
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// verify the result
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for(size_t i=0; i<N; i++) {
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if(scan_seq[i] != scan_par[i]) {
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printf(
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"scan_seq[%zu]=%d..., scan_par[%zu]=%d...\n",
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i, scan_seq[i], i, scan_par[i]
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);
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throw std::runtime_error("incorrect result");
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}
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}
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printf("correct result\n");
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return 0;
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}
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