d87691ec60
git-subtree-dir: subtree/rabit git-subtree-split: c7282acb2a92e1d6a32614889ff466fec58937f3
30 lines
875 B
C++
30 lines
875 B
C++
/*!
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* Copyright (c) 2014 by Contributors
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* \file basic.cc
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* \brief This is an example demonstrating what is Allreduce
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*
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* \author Tianqi Chen
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*/
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#include <rabit.h>
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using namespace rabit;
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const int N = 3;
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int main(int argc, char *argv[]) {
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int a[N];
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rabit::Init(argc, argv);
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for (int i = 0; i < N; ++i) {
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a[i] = rabit::GetRank() + i;
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}
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printf("@node[%d] before-allreduce: a={%d, %d, %d}\n",
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rabit::GetRank(), a[0], a[1], a[2]);
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// allreduce take max of each elements in all processes
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Allreduce<op::Max>(&a[0], N);
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printf("@node[%d] after-allreduce-max: a={%d, %d, %d}\n",
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rabit::GetRank(), a[0], a[1], a[2]);
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// second allreduce that sums everything up
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Allreduce<op::Sum>(&a[0], N);
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printf("@node[%d] after-allreduce-sum: a={%d, %d, %d}\n",
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rabit::GetRank(), a[0], a[1], a[2]);
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rabit::Finalize();
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return 0;
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}
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