Function CheckSampledRows

tests/cpp/tree/test_sampler.h:17–35

Check that multi-target rows are consistently sampled and return count.

namespace xgboost::tree {
// Check that multi-target rows are consistently sampled and return count.
inline bst_idx_t CheckSampledRows(linalg::MatrixView<GradientPair const> gpair_0,
                                  linalg::MatrixView<GradientPair const> gpair_1) {
  CHECK_EQ(gpair_0.Shape(0), gpair_1.Shape(0));
  CHECK_GE(gpair_1.Shape(1), gpair_1.Shape(1));
  auto n_samples = gpair_0.Shape(0);
  auto n_targets = gpair_1.Shape(1);
  bst_idx_t sampled_count = 0;
  for (std::size_t i = 0; i < n_samples; ++i) {
    bool first_is_zero = gpair_0(i, 0).GetHess() == 0.0f;
    for (bst_target_t t = 0; t < n_targets; ++t) {
      bool is_zero = (gpair_1(i, t).GetGrad() == 0.0f && gpair_1(i, t).GetHess() == 0.0f);
      EXPECT_EQ(first_is_zero, is_zero);
    }
    if (!first_is_zero) {
      ++sampled_count;
    }
  }
  return sampled_count;
}

// Check that sampling mask was correctly applied from split gradient to value gradient.
inline void CheckSamplingMask(linalg::MatrixView<GradientPair> h_split,