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Fix external memory race in colmaker. (#4980)

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* Move `GetColDensity` out of omp parallel block.
This commit is contained in:
Jiaming Yuan
2019-10-25 04:11:13 -04:00
committed by GitHub
parent 96cd7ec2bb
commit 6ec7e300bd
9 changed files with 29 additions and 18 deletions
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18
src/tree/updater_colmaker.cc
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@@ -339,7 +339,7 @@ class ColMaker: public TreeUpdater {
}
}
// rescan, generate candidate split
#pragma omp parallel
#pragma omp parallel
{
GradStats c, cright;
const int tid = omp_get_thread_num();
@@ -608,17 +608,25 @@ class ColMaker: public TreeUpdater {
poption = static_cast<int>(num_features) * 2 < this->nthread_ ? 1 : 0;
}
if (poption == 0) {
std::vector<float> densities(num_features);
CHECK_EQ(feat_set.size(), num_features);
for (bst_omp_uint i = 0; i < num_features; ++i) {
int32_t const fid = feat_set[i];
densities.at(i) = p_fmat->GetColDensity(fid);
}
#pragma omp parallel for schedule(dynamic, batch_size)
for (bst_omp_uint i = 0; i < num_features; ++i) {
int fid = feat_set[i];
const int tid = omp_get_thread_num();
int32_t const fid = feat_set[i];
int32_t const tid = omp_get_thread_num();
auto c = batch[fid];
const bool ind = c.size() != 0 && c[0].fvalue == c[c.size() - 1].fvalue;
if (param_.NeedForwardSearch(p_fmat->GetColDensity(fid), ind)) {
auto const density = densities[i];
if (param_.NeedForwardSearch(density, ind)) {
this->EnumerateSplit(c.data(), c.data() + c.size(), +1,
fid, gpair, info, stemp_[tid]);
}
if (param_.NeedBackwardSearch(p_fmat->GetColDensity(fid), ind)) {
if (param_.NeedBackwardSearch(density, ind)) {
this->EnumerateSplit(c.data() + c.size() - 1, c.data() - 1, -1,
fid, gpair, info, stemp_[tid]);
}