73 lines
2.6 KiB
C++
73 lines
2.6 KiB
C++
#pragma once
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#include <cstring> //memset
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#include <vector>
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//using namespace std;
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/** \brief Determines all prime numbers in interval [2, @p max].
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*
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* The sieve of Eratosthenes is used.
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*
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* The implementation originates from <a href="http://code.activestate.com/recipes/576559-fast-prime-generator/">Florian Mayer</a>.
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*
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* \param[in] max end of interval for the prime number search.
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* \return vector of prime numbers @f$2,3,5, ..., p<=max @f$.
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*
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* \copyright
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* Copyright (c) 2008 Florian Mayer (adapted by Gundolf Haase 2018)
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
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* INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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*/
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template <class T>
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std::vector<T> get_primes(T max)
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{
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std::vector<T> primes;
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char *sieve;
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sieve = new char[max / 8 + 1];
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// Fill sieve with 1
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memset(sieve, 0xFF, (max / 8 + 1) * sizeof(char));
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for (T x = 2; x <= max; x++)
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{
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if (sieve[x / 8] & (0x01 << (x % 8))) {
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primes.push_back(x);
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// Is prime. Mark multiplicates.
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for (T j = 2 * x; j <= max; j += x)
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{
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sieve[j / 8] &= ~(0x01 << (j % 8));
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}
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}
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}
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delete[] sieve;
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return primes;
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}
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//---------------------------------------------------------------
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//int main() // by Florian Mayer
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//{g++ -O3 -std=c++14 -fopenmp main.cpp && ./a.out
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// vector<unsigned long> primes;
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// primes = get_primes(10000000);
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// // return 0;
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// // Print out result.
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// vector<unsigned long>::iterator it;
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// for(it=primes.begin(); it < primes.end(); it++)
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// cout << *it << " ";
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//
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// cout << endl;
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// return 0;
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//}
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