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Support column-split in row partitioner (#8828)

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This commit is contained in:
Rong Ou
2023-02-25 12:43:35 -08:00
committed by GitHub
parent 90c0633a28
commit d9688f93c7
8 changed files with 283 additions and 58 deletions
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100
src/common/partition_builder.h
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@@ -31,6 +31,8 @@ namespace common {
// BlockSize is template to enable memory alignment easily with C++11 'alignas()' feature
template<size_t BlockSize>
class PartitionBuilder {
using BitVector = RBitField8;
public:
template<typename Func>
void Init(const size_t n_tasks, size_t n_nodes, Func funcNTask) {
@@ -121,27 +123,11 @@ class PartitionBuilder {
bool default_left = tree[nid].DefaultLeft();
bool is_cat = tree.GetSplitTypes()[nid] == FeatureType::kCategorical;
auto node_cats = tree.NodeCats(nid);
auto const& index = gmat.index;
auto const& cut_values = gmat.cut.Values();
auto const& cut_ptrs = gmat.cut.Ptrs();
auto gidx_calc = [&](auto ridx) {
auto begin = gmat.RowIdx(ridx);
if (gmat.IsDense()) {
return static_cast<bst_bin_t>(index[begin + fid]);
}
auto end = gmat.RowIdx(ridx + 1);
auto f_begin = cut_ptrs[fid];
auto f_end = cut_ptrs[fid + 1];
// bypassing the column matrix as we need the cut value instead of bin idx for categorical
// features.
return BinarySearchBin(begin, end, index, f_begin, f_end);
};
auto pred_hist = [&](auto ridx, auto bin_id) {
if (any_cat && is_cat) {
auto gidx = gidx_calc(ridx);
auto gidx = gmat.GetGindex(ridx, fid);
bool go_left = default_left;
if (gidx > -1) {
go_left = Decision(node_cats, cut_values[gidx]);
@@ -153,7 +139,7 @@ class PartitionBuilder {
};
auto pred_approx = [&](auto ridx) {
auto gidx = gidx_calc(ridx);
auto gidx = gmat.GetGindex(ridx, fid);
bool go_left = default_left;
if (gidx > -1) {
if (is_cat) {
@@ -199,6 +185,84 @@ class PartitionBuilder {
SetNRightElems(node_in_set, range.begin(), n_right);
}
/**
* @brief When data is split by column, we don't have all the features locally on the current
* worker, so we go through all the rows and mark the bit vectors on whether the decision is made
* to go right, or if the feature value used for the split is missing.
*/
void MaskRows(const size_t node_in_set, std::vector<xgboost::tree::CPUExpandEntry> const &nodes,
const common::Range1d range, GHistIndexMatrix const& gmat,
const common::ColumnMatrix& column_matrix,
const RegTree& tree, const size_t* rid,
BitVector* decision_bits, BitVector* missing_bits) {
common::Span<const size_t> rid_span(rid + range.begin(), rid + range.end());
std::size_t nid = nodes[node_in_set].nid;
bst_feature_t fid = tree[nid].SplitIndex();
bool is_cat = tree.GetSplitTypes()[nid] == FeatureType::kCategorical;
auto node_cats = tree.NodeCats(nid);
auto const& cut_values = gmat.cut.Values();
if (!column_matrix.IsInitialized()) {
for (auto row_id : rid_span) {
auto gidx = gmat.GetGindex(row_id, fid);
if (gidx > -1) {
bool go_left = false;
if (is_cat) {
go_left = Decision(node_cats, cut_values[gidx]);
} else {
go_left = cut_values[gidx] <= nodes[node_in_set].split.split_value;
}
if (go_left) {
decision_bits->Set(row_id - gmat.base_rowid);
}
} else {
missing_bits->Set(row_id - gmat.base_rowid);
}
}
} else {
LOG(FATAL) << "Column data split is only supported for the `approx` tree method";
}
}
/**
* @brief Once we've aggregated the decision and missing bits from all the workers, we can then
* use them to partition the rows accordingly.
*/
void PartitionByMask(const size_t node_in_set,
std::vector<xgboost::tree::CPUExpandEntry> const& nodes,
const common::Range1d range, GHistIndexMatrix const& gmat,
const common::ColumnMatrix& column_matrix, const RegTree& tree,
const size_t* rid, BitVector const& decision_bits,
BitVector const& missing_bits) {
common::Span<const size_t> rid_span(rid + range.begin(), rid + range.end());
common::Span<size_t> left = GetLeftBuffer(node_in_set, range.begin(), range.end());
common::Span<size_t> right = GetRightBuffer(node_in_set, range.begin(), range.end());
std::size_t nid = nodes[node_in_set].nid;
bool default_left = tree[nid].DefaultLeft();
auto pred_approx = [&](auto ridx) {
bool go_left = default_left;
bool is_missing = missing_bits.Check(ridx - gmat.base_rowid);
if (!is_missing) {
go_left = decision_bits.Check(ridx - gmat.base_rowid);
}
return go_left;
};
std::pair<size_t, size_t> child_nodes_sizes;
if (!column_matrix.IsInitialized()) {
child_nodes_sizes = PartitionRangeKernel(rid_span, left, right, pred_approx);
} else {
LOG(FATAL) << "Column data split is only supported for the `approx` tree method";
}
const size_t n_left = child_nodes_sizes.first;
const size_t n_right = child_nodes_sizes.second;
SetNLeftElems(node_in_set, range.begin(), n_left);
SetNRightElems(node_in_set, range.begin(), n_right);
}
// allocate thread local memory, should be called for each specific task
void AllocateForTask(size_t id) {
if (mem_blocks_[id].get() == nullptr) {

18
src/data/gradient_index.cc
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@@ -150,16 +150,24 @@ common::ColumnMatrix const &GHistIndexMatrix::Transpose() const {
return *columns_;
}
bst_bin_t GHistIndexMatrix::GetGindex(size_t ridx, size_t fidx) const {
auto begin = RowIdx(ridx);
if (IsDense()) {
return static_cast<bst_bin_t>(index[begin + fidx]);
}
auto end = RowIdx(ridx + 1);
auto const& cut_ptrs = cut.Ptrs();
auto f_begin = cut_ptrs[fidx];
auto f_end = cut_ptrs[fidx + 1];
return BinarySearchBin(begin, end, index, f_begin, f_end);
}
float GHistIndexMatrix::GetFvalue(size_t ridx, size_t fidx, bool is_cat) const {
auto const &values = cut.Values();
auto const &mins = cut.MinValues();
auto const &ptrs = cut.Ptrs();
if (is_cat) {
auto f_begin = ptrs[fidx];
auto f_end = ptrs[fidx + 1];
auto begin = RowIdx(ridx);
auto end = RowIdx(ridx + 1);
auto gidx = BinarySearchBin(begin, end, index, f_begin, f_end);
auto gidx = GetGindex(ridx, fidx);
if (gidx == -1) {
return std::numeric_limits<float>::quiet_NaN();
}

2
src/data/gradient_index.h
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@@ -228,6 +228,8 @@ class GHistIndexMatrix {
common::ColumnMatrix const& Transpose() const;
bst_bin_t GetGindex(size_t ridx, size_t fidx) const;
float GetFvalue(size_t ridx, size_t fidx, bool is_cat) const;
private:

103
src/tree/common_row_partitioner.h
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@@ -9,6 +9,7 @@
#include <limits> // std::numeric_limits
#include <vector>
#include "../collective/communicator-inl.h"
#include "../common/numeric.h" // Iota
#include "../common/partition_builder.h"
#include "hist/expand_entry.h" // CPUExpandEntry
@@ -16,17 +17,73 @@
namespace xgboost {
namespace tree {
class CommonRowPartitioner {
static constexpr size_t kPartitionBlockSize = 2048;
common::PartitionBuilder<kPartitionBlockSize> partition_builder_;
common::RowSetCollection row_set_collection_;
static constexpr size_t kPartitionBlockSize = 2048;
class ColumnSplitHelper {
public:
ColumnSplitHelper() = default;
ColumnSplitHelper(bst_row_t num_row,
common::PartitionBuilder<kPartitionBlockSize>* partition_builder,
common::RowSetCollection* row_set_collection)
: partition_builder_{partition_builder}, row_set_collection_{row_set_collection} {
decision_storage_.resize(num_row);
decision_bits_ = BitVector(common::Span<BitVector::value_type>(decision_storage_));
missing_storage_.resize(num_row);
missing_bits_ = BitVector(common::Span<BitVector::value_type>(missing_storage_));
}
void Partition(common::BlockedSpace2d const& space, std::int32_t n_threads,
GHistIndexMatrix const& gmat, common::ColumnMatrix const& column_matrix,
std::vector<CPUExpandEntry> const& nodes, RegTree const* p_tree) {
// When data is split by column, we don't have all the feature values in the local worker, so
// we first collect all the decisions and whether the feature is missing into bit vectors.
std::fill(decision_storage_.begin(), decision_storage_.end(), 0);
std::fill(missing_storage_.begin(), missing_storage_.end(), 0);
common::ParallelFor2d(space, n_threads, [&](size_t node_in_set, common::Range1d r) {
const int32_t nid = nodes[node_in_set].nid;
partition_builder_->MaskRows(node_in_set, nodes, r, gmat, column_matrix, *p_tree,
(*row_set_collection_)[nid].begin, &decision_bits_,
&missing_bits_);
});
// Then aggregate the bit vectors across all the workers.
collective::Allreduce<collective::Operation::kBitwiseOR>(decision_storage_.data(),
decision_storage_.size());
collective::Allreduce<collective::Operation::kBitwiseAND>(missing_storage_.data(),
missing_storage_.size());
// Finally use the bit vectors to partition the rows.
common::ParallelFor2d(space, n_threads, [&](size_t node_in_set, common::Range1d r) {
size_t begin = r.begin();
const int32_t nid = nodes[node_in_set].nid;
const size_t task_id = partition_builder_->GetTaskIdx(node_in_set, begin);
partition_builder_->AllocateForTask(task_id);
partition_builder_->PartitionByMask(node_in_set, nodes, r, gmat, column_matrix, *p_tree,
(*row_set_collection_)[nid].begin, decision_bits_,
missing_bits_);
});
}
private:
using BitVector = RBitField8;
std::vector<BitVector::value_type> decision_storage_{};
BitVector decision_bits_{};
std::vector<BitVector::value_type> missing_storage_{};
BitVector missing_bits_{};
common::PartitionBuilder<kPartitionBlockSize>* partition_builder_;
common::RowSetCollection* row_set_collection_;
};
class CommonRowPartitioner {
public:
bst_row_t base_rowid = 0;
CommonRowPartitioner() = default;
CommonRowPartitioner(Context const* ctx, bst_row_t num_row, bst_row_t _base_rowid)
: base_rowid{_base_rowid} {
CommonRowPartitioner(Context const* ctx, bst_row_t num_row, bst_row_t _base_rowid,
bool is_col_split)
: base_rowid{_base_rowid}, is_col_split_{is_col_split} {
row_set_collection_.Clear();
std::vector<size_t>& row_indices = *row_set_collection_.Data();
row_indices.resize(num_row);
@@ -34,6 +91,10 @@ class CommonRowPartitioner {
std::size_t* p_row_indices = row_indices.data();
common::Iota(ctx, p_row_indices, p_row_indices + row_indices.size(), base_rowid);
row_set_collection_.Init();
if (is_col_split_) {
column_split_helper_ = ColumnSplitHelper{num_row, &partition_builder_, &row_set_collection_};
}
}
void FindSplitConditions(const std::vector<CPUExpandEntry>& nodes, const RegTree& tree,
@@ -156,16 +217,20 @@ class CommonRowPartitioner {
// 2.3 Split elements of row_set_collection_ to left and right child-nodes for each node
// Store results in intermediate buffers from partition_builder_
common::ParallelFor2d(space, ctx->Threads(), [&](size_t node_in_set, common::Range1d r) {
size_t begin = r.begin();
const int32_t nid = nodes[node_in_set].nid;
const size_t task_id = partition_builder_.GetTaskIdx(node_in_set, begin);
partition_builder_.AllocateForTask(task_id);
bst_bin_t split_cond = column_matrix.IsInitialized() ? split_conditions[node_in_set] : 0;
partition_builder_.template Partition<BinIdxType, any_missing, any_cat>(
node_in_set, nodes, r, split_cond, gmat, column_matrix, *p_tree,
row_set_collection_[nid].begin);
});
if (is_col_split_) {
column_split_helper_.Partition(space, ctx->Threads(), gmat, column_matrix, nodes, p_tree);
} else {
common::ParallelFor2d(space, ctx->Threads(), [&](size_t node_in_set, common::Range1d r) {
size_t begin = r.begin();
const int32_t nid = nodes[node_in_set].nid;
const size_t task_id = partition_builder_.GetTaskIdx(node_in_set, begin);
partition_builder_.AllocateForTask(task_id);
bst_bin_t split_cond = column_matrix.IsInitialized() ? split_conditions[node_in_set] : 0;
partition_builder_.template Partition<BinIdxType, any_missing, any_cat>(
node_in_set, nodes, r, split_cond, gmat, column_matrix, *p_tree,
row_set_collection_[nid].begin);
});
}
// 3. Compute offsets to copy blocks of row-indexes
// from partition_builder_ to row_set_collection_
@@ -205,6 +270,12 @@ class CommonRowPartitioner {
ctx, tree, this->Partitions(), p_out_position,
[&](size_t idx) -> bool { return gpair[idx].GetHess() - .0f == .0f; });
}
private:
common::PartitionBuilder<kPartitionBlockSize> partition_builder_;
common::RowSetCollection row_set_collection_;
bool is_col_split_;
ColumnSplitHelper column_split_helper_;
};
} // namespace tree

2
src/tree/updater_approx.cc
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@@ -71,7 +71,7 @@ class GloablApproxBuilder {
} else {
CHECK_EQ(n_total_bins, page.cut.TotalBins());
}
partitioner_.emplace_back(this->ctx_, page.Size(), page.base_rowid);
partitioner_.emplace_back(this->ctx_, page.Size(), page.base_rowid, p_fmat->IsColumnSplit());
n_batches_++;
}

2
src/tree/updater_quantile_hist.cc
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@@ -277,7 +277,7 @@ void QuantileHistMaker::Builder::InitData(DMatrix *fmat, const RegTree &tree,
} else {
CHECK_EQ(n_total_bins, page.cut.TotalBins());
}
partitioner_.emplace_back(this->ctx_, page.Size(), page.base_rowid);
partitioner_.emplace_back(this->ctx_, page.Size(), page.base_rowid, fmat->IsColumnSplit());
++page_id;
}
histogram_builder_->Reset(n_total_bins, HistBatch(param_), ctx_->Threads(), page_id,