73ef4ff3
 Hu Chunming
提交三方库
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// Copyright Alain Miniussi 2014.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
// Authors: Alain Miniussi
#include <boost/mpi/detail/offsets.hpp>
#include <boost/mpi/detail/antiques.hpp>
namespace boost { namespace mpi {
namespace detail {
// Convert a sequence of sizes [S0..Sn] to a sequence displacement
// [O0..On] where O[0] = 0 and O[k+1] = O[k]+S[k].
void
sizes2offsets(int const* sizes, int* offsets, int n)
{
offsets[0] = 0;
for(int i = 1; i < n; ++i) {
offsets[i] = offsets[i-1] + sizes[i-1];
}
}
// Convert a sequence of sizes [S0..Sn] to a sequence displacement
// [O0..On] where O[0] = 0 and O[k+1] = O[k]+S[k].
void
sizes2offsets(std::vector<int> const& sizes, std::vector<int>& offsets)
{
int sz = sizes.size();
offsets.resize(sz);
sizes2offsets(c_data(sizes), c_data(offsets), sz);
}
// Given a sequence of sizes (typically the number of records dispatched
// to each process in a scater) and a sequence of displacements (typically the
// slot index at with those record starts), convert the later to a number
// of skipped slots.
void
offsets2skipped(int const* sizes, int const* offsets, int* skipped, int n)
{
skipped[0] = 0;
for(int i = 1; i < n; ++i) {
skipped[i] -= offsets[i-1] + sizes[i-1];
}
}
// Reconstruct offsets from sizes assuming no padding.
// Only takes place if on the root process and if
// displs are not already provided.
// If memory was allocated, returns a pointer to it
// otherwise null.
int*
make_offsets(communicator const& comm, int const* sizes, int const* displs, int root)
{
if (root == -1 || root == comm.rank()) {
assert(sizes);
if (!displs) {
int nproc = comm.size();
int* offsets = new int[nproc];
displs = offsets;
sizes2offsets(sizes, offsets, nproc);
return offsets;
} else {
return 0;
}
} else {
return 0;
}
}
// Reconstruct skip slots from sizes and offsets.
// Only takes place if on the root process and if
// displs are provided.
// If memory was allocated, returns a pointer to it
// otherwise null.
int*
make_skipped_slots(communicator const& comm, int const* sizes, int const* displs, int root)
{
if (root == -1 || root == comm.rank()) {
assert(sizes);
if (displs) {
int nproc = comm.size();
int* skipped = new int[nproc];
std::copy(displs, displs+nproc, skipped);
offsets2skipped(sizes, displs, skipped, nproc);
return skipped;
} else {
return 0;
}
} else {
return 0;
}
}
}
}}
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