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104 lines
2.7 KiB
104 lines
2.7 KiB
#include <iostream> // cout
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#include <vector>
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#include <algorithm> // min_element
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#include <cstdlib> // srand, rand, atoi
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#include <ctime> // time, timespec, clock_gettime
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#include <cmath> // pow, sqrt, log
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#include <cfloat> // FLX_MAX
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#include <QtCore/QtCore>
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#include <QtCore/QThreadPool>
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#include <QtCore/QtConcurrentRun>
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#include <QtCore/QFutureSynchronizer>
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const int RANDOM_MAX = 1000;
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const int RANDOM_MIN = 1;
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timespec diff(timespec start, timespec end)
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{
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timespec temp;
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if ((end.tv_nsec-start.tv_nsec)<0) {
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temp.tv_sec = end.tv_sec-start.tv_sec-1;
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temp.tv_nsec = 1000000000+end.tv_nsec-start.tv_nsec;
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} else {
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temp.tv_sec = end.tv_sec-start.tv_sec;
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temp.tv_nsec = end.tv_nsec-start.tv_nsec;
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}
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return temp;
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}
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void findLocalMinimum(const std::vector<float>::const_iterator begin,
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const std::vector<float>::const_iterator end,
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float *result)
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{
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float min(FLT_MAX);
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for(std::vector<float>::const_iterator it = begin; it != end; ++it)
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if (*it < min)
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min = *it;
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*result = min;
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}
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float QtReduce(std::vector<float>& data,
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const int numberOfThreads,
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const int chunkSize)
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{
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std::vector<float> separate_results(numberOfThreads, FLT_MAX);
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QFutureSynchronizer<void> synchronizer;
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for(int i = 0; i < numberOfThreads; i++)
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synchronizer.addFuture(QtConcurrent::run(findLocalMinimum,
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data.begin()+i*chunkSize,
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data.begin()+(i+1)*chunkSize,
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separate_results.data()+i));
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synchronizer.waitForFinished();
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// serial reduce
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float min(FLT_MAX);
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for (int i = 0; i < numberOfThreads; i++)
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if (separate_results[i] < min)
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min = separate_results[i];
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return min;
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}
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int main(int argc, char* argv[])
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{
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if (argc != 3) {
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std::cout << "Usage: " << argv[0] << " <NUMBER_OF_THREADS> <DATA_SIZE>" << std::endl;
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exit(1);
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}
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const int NUMBER_OF_THREADS = atoi(argv[1]);
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const int DATA_SIZE = atoi(argv[2]);
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const int CHUNK_SIZE = DATA_SIZE / NUMBER_OF_THREADS;
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srand(time(NULL));
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QCoreApplication app(argc, argv);
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QThreadPool::globalInstance()->setMaxThreadCount(NUMBER_OF_THREADS);
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std::vector<float> data(DATA_SIZE);
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for (int i = 0; i < DATA_SIZE; i++)
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data[i] = rand() % RANDOM_MAX + RANDOM_MIN;
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timespec startTime;
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clock_gettime(CLOCK_MONOTONIC, &startTime);
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float min = QtReduce(data, NUMBER_OF_THREADS, CHUNK_SIZE);
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timespec endTime;
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clock_gettime(CLOCK_MONOTONIC, &endTime);
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timespec timeDiff = diff(startTime, endTime);
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std::cout << timeDiff.tv_sec << "." << timeDiff.tv_nsec << std::endl;
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return 0;
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}
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