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113 lines
4.0 KiB
C++
113 lines
4.0 KiB
C++
// Copyright (c) 2014-2021, The Monero Project
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//
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without modification, are
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// permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice, this list of
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// conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice, this list
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// of conditions and the following disclaimer in the documentation and/or other
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// materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its contributors may be
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// used to endorse or promote products derived from this software without specific
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// prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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const char * descr =
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"This program prints the time (ms) needed to calculate a mathematical challenge. It's purpose \n\
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is to be able to use the result to compare the CPU power available on the machine it's being executed \n\
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and under the given circumstances, which can differ for the same machine. For example: \n\
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The printed value will be different when using 2 of 2 cores, when there an another process \n\
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running on one of the cores core, and when no other intense process running. \n\
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\n\
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The program expects a one argument: a numerical value of the threads to start the calculations on. \n\
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\n\
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Prints: \n\
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Time to calculate a mathematical challenge in MILLISECONDS. \n\
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\n\
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Returns: \n\
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0 on success, \n\
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1 on a missing argument, \n\
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2 on an incorrect format of the argument.\n";
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#include <iostream>
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#include <future>
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#include <vector>
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#include <sstream>
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#include <chrono>
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using namespace std;
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/**
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Uses Leibniz Formula for Pi.
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https://en.wikipedia.org/wiki/Leibniz_formula_for_%CF%80
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*/
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static double calcPi(const size_t max_iter)
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{
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const double n = 4;
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double pi = 0;
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double d = 1;
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for (size_t i = 1; i < max_iter; ++i)
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{
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const double a = 2.0 * (i % 2) - 1.0;
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pi += a * n / d;
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d += 2;
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}
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return pi;
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}
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int main(int argc, const char ** argv)
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{
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const size_t max_iter = 1e9;
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if (argc < 2)
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{
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cout << "Please pass the number of threads to run.\n";
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cout << '\n' << descr << '\n';
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return 1;
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}
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// Convert argument to an integer.
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int numThreads = 1;
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const char * numThreadsStr = argv[1];
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std::istringstream iss(numThreadsStr);
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if (! (iss >> numThreads) )
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{
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cout << "Incorrect format of number of threads = '" << numThreadsStr << "'\n";
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return 2;
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}
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// Run the calculation in parallel.
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std::vector<std::future<double>> futures;
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for(int i = 0; i < numThreads; ++i)
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{
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futures.push_back(std::async(calcPi, max_iter));
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}
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// Start measuring the time.
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const std::chrono::steady_clock::time_point tbegin = std::chrono::steady_clock::now();
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for(auto & e : futures)
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{
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e.get();
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}
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// Stop measuring the time.
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const std::chrono::steady_clock::time_point tend = std::chrono::steady_clock::now();
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// Print the measured duration.
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cout << std::chrono::duration_cast<std::chrono::milliseconds>(tend - tbegin).count() << std::endl;
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return 0;
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}
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