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Optimized BuildHist function (#5156)

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This commit is contained in:
Egor Smirnov
2020-01-30 10:32:57 +03:00
committed by GitHub
parent 4240daed4e
commit c67163250e
8 changed files with 610 additions and 184 deletions
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17
src/common/threading_utils.h
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@@ -108,12 +108,19 @@ class BlockedSpace2d {
// Wrapper to implement nested parallelism with simple omp parallel for
template<typename Func>
void ParallelFor2d(const BlockedSpace2d& space, Func func) {
const int num_blocks_in_space = static_cast<int>(space.Size());
void ParallelFor2d(const BlockedSpace2d& space, const int nthreads, Func func) {
const size_t num_blocks_in_space = space.Size();
#pragma omp parallel for
for (auto i = 0; i < num_blocks_in_space; i++) {
func(space.GetFirstDimension(i), space.GetRange(i));
#pragma omp parallel num_threads(nthreads)
{
size_t tid = omp_get_thread_num();
size_t chunck_size = num_blocks_in_space / nthreads + !!(num_blocks_in_space % nthreads);
size_t begin = chunck_size * tid;
size_t end = std::min(begin + chunck_size, num_blocks_in_space);
for (auto i = begin; i < end; i++) {
func(space.GetFirstDimension(i), space.GetRange(i));
}
}
}