[SYCL] Add sampling initialization (#10216)

---------

Co-authored-by: Dmitry Razdoburdin <>

plugin/sycl/tree/hist_updater.cc

@@ -0,0 +1,58 @@
+/*!
+ * Copyright 2017-2024 by Contributors
+ * \file hist_updater.cc
+ */
+
+#include "hist_updater.h"
+
+#include <oneapi/dpl/random>
+
+namespace xgboost {
+namespace sycl {
+namespace tree {
+
+template<typename GradientSumT>
+void HistUpdater<GradientSumT>::InitSampling(
+      const USMVector<GradientPair, MemoryType::on_device> &gpair,
+      USMVector<size_t, MemoryType::on_device>* row_indices) {
+  const size_t num_rows = row_indices->Size();
+  auto* row_idx = row_indices->Data();
+  const auto* gpair_ptr = gpair.DataConst();
+  uint64_t num_samples = 0;
+  const auto subsample = param_.subsample;
+  ::sycl::event event;
+
+  {
+    ::sycl::buffer<uint64_t, 1> flag_buf(&num_samples, 1);
+    uint64_t seed = seed_;
+    seed_ += num_rows;
+    event = qu_.submit([&](::sycl::handler& cgh) {
+      auto flag_buf_acc  = flag_buf.get_access<::sycl::access::mode::read_write>(cgh);
+      cgh.parallel_for<>(::sycl::range<1>(::sycl::range<1>(num_rows)),
+                                          [=](::sycl::item<1> pid) {
+        uint64_t i = pid.get_id(0);
+
+        // Create minstd_rand engine
+        oneapi::dpl::minstd_rand engine(seed, i);
+        oneapi::dpl::bernoulli_distribution coin_flip(subsample);
+
+        auto rnd = coin_flip(engine);
+        if (gpair_ptr[i].GetHess() >= 0.0f && rnd) {
+          AtomicRef<uint64_t> num_samples_ref(flag_buf_acc[0]);
+          row_idx[num_samples_ref++] = i;
+        }
+      });
+    });
+    /* After calling a destructor for flag_buf,  content will be copyed to num_samples */
+  }
+
+  row_indices->Resize(&qu_, num_samples, 0, &event);
+  qu_.wait();
+}
+
+template class HistUpdater<float>;
+template class HistUpdater<double>;
+
+}  // namespace tree
+}  // namespace sycl
+}  // namespace xgboost

plugin/sycl/tree/hist_updater.h

@@ -0,0 +1,72 @@
+/*!
+ * Copyright 2017-2024 by Contributors
+ * \file hist_updater.h
+ */
+#ifndef PLUGIN_SYCL_TREE_HIST_UPDATER_H_
+#define PLUGIN_SYCL_TREE_HIST_UPDATER_H_
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wtautological-constant-compare"
+#pragma GCC diagnostic ignored "-W#pragma-messages"
+#include <xgboost/tree_updater.h>
+#pragma GCC diagnostic pop
+
+#include <utility>
+#include <memory>
+
+#include "../common/partition_builder.h"
+#include "split_evaluator.h"
+
+#include "../data.h"
+
+namespace xgboost {
+namespace sycl {
+namespace tree {
+
+template<typename GradientSumT>
+class HistUpdater {
+ public:
+  explicit HistUpdater(::sycl::queue qu,
+                    const xgboost::tree::TrainParam& param,
+                    std::unique_ptr<TreeUpdater> pruner,
+                    FeatureInteractionConstraintHost int_constraints_,
+                    DMatrix const* fmat)
+    : qu_(qu), param_(param),
+      tree_evaluator_(qu, param, fmat->Info().num_col_),
+      pruner_(std::move(pruner)),
+      interaction_constraints_{std::move(int_constraints_)},
+      p_last_tree_(nullptr), p_last_fmat_(fmat) {
+    builder_monitor_.Init("SYCL::Quantile::HistUpdater");
+    kernel_monitor_.Init("SYCL::Quantile::HistUpdater");
+    const auto sub_group_sizes =
+      qu_.get_device().get_info<::sycl::info::device::sub_group_sizes>();
+    sub_group_size_ = sub_group_sizes.back();
+  }
+
+ protected:
+  void InitSampling(const USMVector<GradientPair, MemoryType::on_device> &gpair,
+                    USMVector<size_t, MemoryType::on_device>* row_indices);
+
+  size_t sub_group_size_;
+  const xgboost::tree::TrainParam& param_;
+  TreeEvaluator<GradientSumT> tree_evaluator_;
+  std::unique_ptr<TreeUpdater> pruner_;
+  FeatureInteractionConstraintHost interaction_constraints_;
+
+  // back pointers to tree and data matrix
+  const RegTree* p_last_tree_;
+  DMatrix const* const p_last_fmat_;
+
+  xgboost::common::Monitor builder_monitor_;
+  xgboost::common::Monitor kernel_monitor_;
+
+  uint64_t seed_ = 0;
+
+  ::sycl::queue qu_;
+};
+
+}  // namespace tree
+}  // namespace sycl
+}  // namespace xgboost
+
+#endif  // PLUGIN_SYCL_TREE_HIST_UPDATER_H_