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Extract partial sum into an independent function. (#7889)

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This commit is contained in:
Jiaming Yuan
2022-05-13 14:30:35 +08:00
committed by GitHub
parent db80671d6b
commit 11d65fcb21
7 changed files with 138 additions and 68 deletions
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56
src/data/gradient_index.cc
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@@ -10,6 +10,7 @@
#include "../common/column_matrix.h"
#include "../common/hist_util.h"
#include "../common/numeric.h"
#include "../common/threading_utils.h"
namespace xgboost {
@@ -28,58 +29,13 @@ void GHistIndexMatrix::PushBatch(SparsePage const &batch,
common::Span<FeatureType const> ft,
size_t rbegin, size_t prev_sum, uint32_t nbins,
int32_t n_threads) {
// The number of threads is pegged to the batch size. If the OMP
// block is parallelized on anything other than the batch/block size,
// it should be reassigned
auto page = batch.GetView();
auto it = common::MakeIndexTransformIter([&](size_t ridx) { return page[ridx].size(); });
common::PartialSum(n_threads, it, it + page.Size(), prev_sum, row_ptr.begin() + rbegin);
// The number of threads is pegged to the batch size. If the OMP block is parallelized
// on anything other than the batch/block size, it should be reassigned
const size_t batch_threads =
std::max(static_cast<size_t>(1), std::min(batch.Size(), static_cast<size_t>(n_threads)));
auto page = batch.GetView();
common::MemStackAllocator<size_t, 128> partial_sums(batch_threads);
size_t block_size = batch.Size() / batch_threads;
dmlc::OMPException exc;
#pragma omp parallel num_threads(batch_threads)
{
#pragma omp for
for (omp_ulong tid = 0; tid < batch_threads; ++tid) {
exc.Run([&]() {
size_t ibegin = block_size * tid;
size_t iend = (tid == (batch_threads - 1) ? batch.Size()
: (block_size * (tid + 1)));
size_t running_sum = 0;
for (size_t ridx = ibegin; ridx < iend; ++ridx) {
running_sum += page[ridx].size();
row_ptr[rbegin + 1 + ridx] = running_sum;
}
});
}
#pragma omp single
{
exc.Run([&]() {
partial_sums[0] = prev_sum;
for (size_t i = 1; i < batch_threads; ++i) {
partial_sums[i] = partial_sums[i - 1] + row_ptr[rbegin + i * block_size];
}
});
}
#pragma omp for
for (omp_ulong tid = 0; tid < batch_threads; ++tid) {
exc.Run([&]() {
size_t ibegin = block_size * tid;
size_t iend = (tid == (batch_threads - 1) ? batch.Size()
: (block_size * (tid + 1)));
for (size_t i = ibegin; i < iend; ++i) {
row_ptr[rbegin + 1 + i] += partial_sums[tid];
}
});
}
}
exc.Rethrow();
const size_t n_index = row_ptr[rbegin + batch.Size()]; // number of entries in this page
ResizeIndex(n_index, isDense_);