47 lines
1.4 KiB
C++
47 lines
1.4 KiB
C++
// Copyright (C) 2006 Douglas Gregor <doug.gregor@gmail.com>
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// Use, modification and distribution is subject to the Boost Software
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// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// An example using Boost.MPI's reduce() to concatenate strings.
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#include <boost/mpi.hpp>
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#include <iostream>
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#include <string>
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#include <boost/serialization/string.hpp> // Important for sending strings!
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namespace mpi = boost::mpi;
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/* Defining STRING_CONCAT_COMMUTATIVE lies to Boost.MPI by forcing it
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* to assume that string concatenation is commutative, which it is
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* not. However, doing so illustrates how the results of a reduction
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* can change when a non-commutative operator is assumed to be
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* commutative.
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*/
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#ifdef STRING_CONCAT_COMMUTATIVE
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namespace boost { namespace mpi {
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template<>
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struct is_commutative<std::plus<std::string>, std::string> : mpl::true_ { };
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} } // end namespace boost::mpi
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#endif
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int main(int argc, char* argv[])
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{
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mpi::environment env(argc, argv);
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mpi::communicator world;
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std::string names[10] = { "zero ", "one ", "two ", "three ", "four ",
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"five ", "six ", "seven ", "eight ", "nine " };
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std::string result;
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reduce(world,
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world.rank() < 10? names[world.rank()] : std::string("many "),
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result, std::plus<std::string>(), 0);
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if (world.rank() == 0)
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std::cout << "The result is " << result << std::endl;
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return 0;
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}
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