[sync]. Add partition builder. (#10011)

---------

Co-authored-by: Dmitry Razdoburdin <>

tests/cpp/plugin/test_sycl_partition_builder.cc

@@ -0,0 +1,91 @@
+/**
+ * Copyright 2020-2024 by XGBoost contributors
+ */
+#include <gtest/gtest.h>
+
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "../../../plugin/sycl/common/partition_builder.h"
+#include "../../../plugin/sycl/device_manager.h"
+#include "../helpers.h"
+
+namespace xgboost::sycl::common {
+
+TEST(SyclPartitionBuilder, BasicTest) {
+  constexpr size_t kNodes = 5;
+  // Number of rows for each node
+  std::vector<size_t> rows = { 5, 5, 10, 1, 2 };
+
+  DeviceManager device_manager;
+  auto qu = device_manager.GetQueue(DeviceOrd::SyclDefault());
+  PartitionBuilder builder;
+  builder.Init(&qu, kNodes, [&](size_t i) {
+    return rows[i];
+  });
+
+  // We test here only the basics, thus syntetic partition builder is adopted
+  // Number of rows to go left for each node.
+  std::vector<size_t> rows_for_left_node = { 2, 0, 7, 1, 2 };
+
+  size_t first_row_id = 0;
+  for(size_t nid = 0; nid < kNodes; ++nid) {
+    size_t n_rows_nodes = rows[nid];
+
+    auto rid_buff = builder.GetData(nid);
+    size_t rid_buff_size = rid_buff.size();
+    auto* rid_buff_ptr = rid_buff.data();
+
+    size_t n_left  = rows_for_left_node[nid];
+    size_t n_right = rows[nid] - n_left;
+
+    qu.submit([&](::sycl::handler& cgh) {
+      cgh.parallel_for<>(::sycl::range<1>(n_left), [=](::sycl::id<1> pid) {
+        int row_id = first_row_id + pid[0];
+        rid_buff_ptr[pid[0]] = row_id;
+      });
+    });
+    qu.wait();
+    first_row_id += n_left;
+
+    // We are storing indexes for the right side in the tail of the array to save some memory
+    qu.submit([&](::sycl::handler& cgh) {
+      cgh.parallel_for<>(::sycl::range<1>(n_right), [=](::sycl::id<1> pid) {
+        int row_id = first_row_id + pid[0];
+        rid_buff_ptr[rid_buff_size - pid[0] - 1] = row_id;
+      });
+    });
+    qu.wait();
+    first_row_id += n_right;
+
+    builder.SetNLeftElems(nid, n_left);
+    builder.SetNRightElems(nid, n_right);
+  }
+
+  ::sycl::event event;
+  std::vector<size_t> v(*std::max_element(rows.begin(), rows.end()));
+  size_t row_id = 0;
+  for(size_t nid = 0; nid < kNodes; ++nid) {
+    builder.MergeToArray(nid, v.data(), event);
+    qu.wait();
+
+    // Check that row_id for left side are correct
+    for(size_t j = 0; j < rows_for_left_node[nid]; ++j) {
+       ASSERT_EQ(v[j], row_id++);
+    }
+
+    // Check that row_id for right side are correct
+    for(size_t j = 0; j < rows[nid] - rows_for_left_node[nid]; ++j) {
+      ASSERT_EQ(v[rows[nid] - j - 1], row_id++);
+    }
+
+    // Check that number of left/right rows are correct
+    size_t n_left  = builder.GetNLeftElems(nid);
+    size_t n_right = builder.GetNRightElems(nid);
+    ASSERT_EQ(n_left, rows_for_left_node[nid]);
+    ASSERT_EQ(n_right, (rows[nid] - rows_for_left_node[nid]));
+  }
+}
+
+}  // namespace xgboost::common