69 lines
2.9 KiB
C++
69 lines
2.9 KiB
C++
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// fig17_01.cpp
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// Profiling sequential and parallel sorting with the std::sort algorithm.
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#include <algorithm>
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#include <chrono> // for timing operations
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#include <execution> // for execution policies
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#include <iostream>
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#include <iterator>
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#include <random>
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#include <vector>
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int main() {
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// set up random-number generation
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std::random_device rd;
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std::default_random_engine engine{rd()};
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std::uniform_int_distribution ints{};
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std::cout << "Creating a vector v1 to hold 100,000,000 ints\n";
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std::vector<int> v1(100'000'000); // 100,000,000 element vector
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std::cout << "Filling vector v1 with random ints\n";
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std::generate(v1.begin(), v1.end(), [&](){return ints(engine);});
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// copy v1 to create identical data sets for each sort demonstration
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std::cout << "Copying v1 to vector v2 to create identical data sets\n";
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std::vector v2{v1};
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// <chrono> library features we'll use for timing
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using std::chrono::steady_clock;
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using std::chrono::duration_cast;
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using std::chrono::milliseconds;
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// sequentially sort v1
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std::cout << "\nSorting 100,000,000 ints sequentially\n";
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auto start1{steady_clock::now()}; // get current time
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std::sort(v1.begin(), v1.end()); // sequential sort
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auto end1{steady_clock::now()}; // get current time
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// calculate and display time in milliseconds
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auto time1{duration_cast<milliseconds>(end1 - start1)};
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std::cout << "Time: " << (time1.count() / 1000.0) << " seconds\n";
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// parallel sort v2
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std::cout << "\nSorting the same 100,000,000 ints in parallel\n";
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auto start2{steady_clock::now()}; // get current time
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std::sort(std::execution::par, v2.begin(), v2.end()); // parallel sort
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auto end2{steady_clock::now()}; // get current time
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// calculate and display time in milliseconds
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auto time2{duration_cast<milliseconds>(end2 - start2)};
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std::cout << "Time: " << (time2.count() / 1000.0) << " seconds\n";
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}
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/**************************************************************************
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* (C) Copyright 1992-2021 by Deitel & Associates, Inc. and *
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* Pearson Education, Inc. All Rights Reserved. *
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* *
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* DISCLAIMER: The authors and publisher of this book have used their *
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* best efforts in preparing the book. These efforts include the *
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* development, research, and testing of the theories and programs *
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* to determine their effectiveness. The authors and publisher make *
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* no warranty of any kind, expressed or implied, with regard to these *
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* programs or to the documentation contained in these books. The authors *
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* and publisher shall not be liable in any event for incidental or *
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* consequential damages in connection with, or arising out of, the *
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* furnishing, performance, or use of these programs. *
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**************************************************************************/
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