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Refactor gpu_hist split evaluation (#5610)

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* Refactor

* Rewrite evaluate splits

* Add more tests
This commit is contained in:
Rory Mitchell
2020-04-30 08:58:12 +12:00
committed by GitHub
parent dfcdfabf1f
commit b9649e7b8e
9 changed files with 678 additions and 355 deletions
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222
tests/cpp/tree/gpu_hist/test_evaluate_splits.cu Normal file
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@@ -0,0 +1,222 @@
#include <gtest/gtest.h>
#include "../../../../src/tree/gpu_hist/evaluate_splits.cuh"
#include "../../helpers.h"
#include "../../histogram_helpers.h"
namespace xgboost {
namespace tree {
TEST(GpuHist, EvaluateSingleSplit) {
thrust::device_vector<DeviceSplitCandidate> out_splits(1);
GradientPair parent_sum(0.0, 1.0);
GPUTrainingParam param{};
thrust::device_vector<bst_feature_t> feature_set =
std::vector<bst_feature_t>{0, 1};
thrust::device_vector<uint32_t> feature_segments =
std::vector<bst_row_t>{0, 2, 4};
thrust::device_vector<float> feature_values =
std::vector<float>{1.0, 2.0, 11.0, 12.0};
thrust::device_vector<float> feature_min_values =
std::vector<float>{0.0, 0.0};
// Setup gradients so that second feature gets higher gain
thrust::device_vector<GradientPair> feature_histogram =
std::vector<GradientPair>{
{-0.5, 0.5}, {0.5, 0.5}, {-1.0, 0.5}, {1.0, 0.5}};
thrust::device_vector<int> monotonic_constraints(feature_set.size(), 0);
EvaluateSplitInputs<GradientPair> input{1,
parent_sum,
param,
dh::ToSpan(feature_set),
dh::ToSpan(feature_segments),
dh::ToSpan(feature_values),
dh::ToSpan(feature_min_values),
dh::ToSpan(feature_histogram),
ValueConstraint(),
dh::ToSpan(monotonic_constraints)};
EvaluateSingleSplit(dh::ToSpan(out_splits), input);
DeviceSplitCandidate result = out_splits[0];
EXPECT_EQ(result.findex, 1);
EXPECT_EQ(result.fvalue, 11.0);
EXPECT_FLOAT_EQ(result.left_sum.GetGrad() + result.right_sum.GetGrad(),
parent_sum.GetGrad());
EXPECT_FLOAT_EQ(result.left_sum.GetHess() + result.right_sum.GetHess(),
parent_sum.GetHess());
}
TEST(GpuHist, EvaluateSingleSplitMissing) {
thrust::device_vector<DeviceSplitCandidate> out_splits(1);
GradientPair parent_sum(1.0, 1.5);
GPUTrainingParam param{};
thrust::device_vector<bst_feature_t> feature_set =
std::vector<bst_feature_t>{0};
thrust::device_vector<uint32_t> feature_segments =
std::vector<bst_row_t>{0, 2};
thrust::device_vector<float> feature_values = std::vector<float>{1.0, 2.0};
thrust::device_vector<float> feature_min_values = std::vector<float>{0.0};
thrust::device_vector<GradientPair> feature_histogram =
std::vector<GradientPair>{{-0.5, 0.5}, {0.5, 0.5}};
thrust::device_vector<int> monotonic_constraints(feature_set.size(), 0);
EvaluateSplitInputs<GradientPair> input{1,
parent_sum,
param,
dh::ToSpan(feature_set),
dh::ToSpan(feature_segments),
dh::ToSpan(feature_values),
dh::ToSpan(feature_min_values),
dh::ToSpan(feature_histogram),
ValueConstraint(),
dh::ToSpan(monotonic_constraints)};
EvaluateSingleSplit(dh::ToSpan(out_splits), input);
DeviceSplitCandidate result = out_splits[0];
EXPECT_EQ(result.findex, 0);
EXPECT_EQ(result.fvalue, 1.0);
EXPECT_EQ(result.dir, kRightDir);
EXPECT_EQ(result.left_sum, GradientPair(-0.5, 0.5));
EXPECT_EQ(result.right_sum, GradientPair(1.5, 1.0));
}
TEST(GpuHist, EvaluateSingleSplitEmpty) {
DeviceSplitCandidate nonzeroed;
nonzeroed.findex = 1;
nonzeroed.loss_chg = 1.0;
thrust::device_vector<DeviceSplitCandidate> out_split(1);
out_split[0] = nonzeroed;
EvaluateSingleSplit(dh::ToSpan(out_split),
EvaluateSplitInputs<GradientPair>{});
DeviceSplitCandidate result = out_split[0];
EXPECT_EQ(result.findex, -1);
EXPECT_LT(result.loss_chg, 0.0f);
}
// Feature 0 has a better split, but the algorithm must select feature 1
TEST(GpuHist, EvaluateSingleSplitFeatureSampling) {
thrust::device_vector<DeviceSplitCandidate> out_splits(1);
GradientPair parent_sum(0.0, 1.0);
GPUTrainingParam param{};
thrust::device_vector<bst_feature_t> feature_set =
std::vector<bst_feature_t>{1};
thrust::device_vector<uint32_t> feature_segments =
std::vector<bst_row_t>{0, 2, 4};
thrust::device_vector<float> feature_values =
std::vector<float>{1.0, 2.0, 11.0, 12.0};
thrust::device_vector<float> feature_min_values =
std::vector<float>{0.0, 10.0};
thrust::device_vector<GradientPair> feature_histogram =
std::vector<GradientPair>{
{-10.0, 0.5}, {10.0, 0.5}, {-0.5, 0.5}, {0.5, 0.5}};
thrust::device_vector<int> monotonic_constraints(2, 0);
EvaluateSplitInputs<GradientPair> input{1,
parent_sum,
param,
dh::ToSpan(feature_set),
dh::ToSpan(feature_segments),
dh::ToSpan(feature_values),
dh::ToSpan(feature_min_values),
dh::ToSpan(feature_histogram),
ValueConstraint(),
dh::ToSpan(monotonic_constraints)};
EvaluateSingleSplit(dh::ToSpan(out_splits), input);
DeviceSplitCandidate result = out_splits[0];
EXPECT_EQ(result.findex, 1);
EXPECT_EQ(result.fvalue, 11.0);
EXPECT_EQ(result.left_sum, GradientPair(-0.5, 0.5));
EXPECT_EQ(result.right_sum, GradientPair(0.5, 0.5));
}
// Features 0 and 1 have identical gain, the algorithm must select 0
TEST(GpuHist, EvaluateSingleSplitBreakTies) {
thrust::device_vector<DeviceSplitCandidate> out_splits(1);
GradientPair parent_sum(0.0, 1.0);
GPUTrainingParam param{};
thrust::device_vector<bst_feature_t> feature_set =
std::vector<bst_feature_t>{0, 1};
thrust::device_vector<uint32_t> feature_segments =
std::vector<bst_row_t>{0, 2, 4};
thrust::device_vector<float> feature_values =
std::vector<float>{1.0, 2.0, 11.0, 12.0};
thrust::device_vector<float> feature_min_values =
std::vector<float>{0.0, 10.0};
thrust::device_vector<GradientPair> feature_histogram =
std::vector<GradientPair>{
{-0.5, 0.5}, {0.5, 0.5}, {-0.5, 0.5}, {0.5, 0.5}};
thrust::device_vector<int> monotonic_constraints(2, 0);
EvaluateSplitInputs<GradientPair> input{1,
parent_sum,
param,
dh::ToSpan(feature_set),
dh::ToSpan(feature_segments),
dh::ToSpan(feature_values),
dh::ToSpan(feature_min_values),
dh::ToSpan(feature_histogram),
ValueConstraint(),
dh::ToSpan(monotonic_constraints)};
EvaluateSingleSplit(dh::ToSpan(out_splits), input);
DeviceSplitCandidate result = out_splits[0];
EXPECT_EQ(result.findex, 0);
EXPECT_EQ(result.fvalue, 1.0);
}
TEST(GpuHist, EvaluateSplits) {
thrust::device_vector<DeviceSplitCandidate> out_splits(2);
GradientPair parent_sum(0.0, 1.0);
GPUTrainingParam param{};
thrust::device_vector<bst_feature_t> feature_set =
std::vector<bst_feature_t>{0, 1};
thrust::device_vector<uint32_t> feature_segments =
std::vector<bst_row_t>{0, 2, 4};
thrust::device_vector<float> feature_values =
std::vector<float>{1.0, 2.0, 11.0, 12.0};
thrust::device_vector<float> feature_min_values =
std::vector<float>{0.0, 0.0};
thrust::device_vector<GradientPair> feature_histogram_left =
std::vector<GradientPair>{
{-0.5, 0.5}, {0.5, 0.5}, {-1.0, 0.5}, {1.0, 0.5}};
thrust::device_vector<GradientPair> feature_histogram_right =
std::vector<GradientPair>{
{-1.0, 0.5}, {1.0, 0.5}, {-0.5, 0.5}, {0.5, 0.5}};
thrust::device_vector<int> monotonic_constraints(feature_set.size(), 0);
EvaluateSplitInputs<GradientPair> input_left{
1,
parent_sum,
param,
dh::ToSpan(feature_set),
dh::ToSpan(feature_segments),
dh::ToSpan(feature_values),
dh::ToSpan(feature_min_values),
dh::ToSpan(feature_histogram_left),
ValueConstraint(),
dh::ToSpan(monotonic_constraints)};
EvaluateSplitInputs<GradientPair> input_right{
2,
parent_sum,
param,
dh::ToSpan(feature_set),
dh::ToSpan(feature_segments),
dh::ToSpan(feature_values),
dh::ToSpan(feature_min_values),
dh::ToSpan(feature_histogram_right),
ValueConstraint(),
dh::ToSpan(monotonic_constraints)};
EvaluateSplits(dh::ToSpan(out_splits), input_left, input_right);
DeviceSplitCandidate result_left = out_splits[0];
EXPECT_EQ(result_left.findex, 1);
EXPECT_EQ(result_left.fvalue, 11.0);
DeviceSplitCandidate result_right = out_splits[1];
EXPECT_EQ(result_right.findex, 0);
EXPECT_EQ(result_right.fvalue, 1.0);
}
} // namespace tree
} // namespace xgboost

6
tests/cpp/tree/gpu_hist/test_gradient_based_sampler.cu
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@@ -41,9 +41,9 @@ void VerifySampling(size_t page_size,
EXPECT_EQ(sample.page->n_rows, kRows);
EXPECT_EQ(sample.gpair.size(), kRows);
} else {
EXPECT_NEAR(sample.sample_rows, sample_rows, kRows * 0.016);
EXPECT_NEAR(sample.page->n_rows, sample_rows, kRows * 0.016f);
EXPECT_NEAR(sample.gpair.size(), sample_rows, kRows * 0.016f);
EXPECT_NEAR(sample.sample_rows, sample_rows, kRows * 0.03);
EXPECT_NEAR(sample.page->n_rows, sample_rows, kRows * 0.03f);
EXPECT_NEAR(sample.gpair.size(), sample_rows, kRows * 0.03f);
}
GradientPair sum_sampled_gpair{};