Partitioner for multi-target tree. (#8922)

tests/cpp/tree/test_approx.cc

@@ -148,78 +148,5 @@ TEST(Approx, PartitionerColSplit) {
   RunWithInMemoryCommunicator(kWorkers, TestColumnSplitPartitioner, n_samples, base_rowid, Xy,
                               &hess, min_value, mid_value, mid_partitioner);
 }
-
-namespace {
-void TestLeafPartition(size_t n_samples) {
-  size_t const n_features = 2, base_rowid = 0;
-  Context ctx;
-  common::RowSetCollection row_set;
-  CommonRowPartitioner partitioner{&ctx, n_samples, base_rowid, false};
-
-  auto Xy = RandomDataGenerator{n_samples, n_features, 0}.GenerateDMatrix(true);
-  std::vector<CPUExpandEntry> candidates{{0, 0}};
-  candidates.front().split.loss_chg = 0.4;
-  RegTree tree;
-  std::vector<float> hess(n_samples, 0);
-  // emulate sampling
-  auto not_sampled = [](size_t i) {
-    size_t const kSampleFactor{3};
-    return i % kSampleFactor != 0;
-  };
-  for (size_t i = 0; i < hess.size(); ++i) {
-    if (not_sampled(i)) {
-      hess[i] = 1.0f;
-    }
-  }
-
-  std::vector<size_t> h_nptr;
-  float split_value{0};
-  for (auto const& page : Xy->GetBatches<GHistIndexMatrix>({Context::kCpuId, 64})) {
-    bst_feature_t const split_ind = 0;
-    auto ptr = page.cut.Ptrs()[split_ind + 1];
-    split_value = page.cut.Values().at(ptr / 2);
-    GetSplit(&tree, split_value, &candidates);
-    partitioner.UpdatePosition(&ctx, page, candidates, &tree);
-    std::vector<bst_node_t> position;
-    partitioner.LeafPartition(&ctx, tree, hess, &position);
-    std::sort(position.begin(), position.end());
-    size_t beg = std::distance(
-        position.begin(),
-        std::find_if(position.begin(), position.end(), [&](bst_node_t nidx) { return nidx >= 0; }));
-    std::vector<size_t> nptr;
-    common::RunLengthEncode(position.cbegin() + beg, position.cend(), &nptr);
-    std::transform(nptr.begin(), nptr.end(), nptr.begin(), [&](size_t x) { return x + beg; });
-    auto n_uniques = std::unique(position.begin() + beg, position.end()) - (position.begin() + beg);
-    ASSERT_EQ(nptr.size(), n_uniques + 1);
-    ASSERT_EQ(nptr[0], beg);
-    ASSERT_EQ(nptr.back(), n_samples);
-
-    h_nptr = nptr;
-  }
-
-  if (h_nptr.front() == n_samples) {
-    return;
-  }
-
-  ASSERT_GE(h_nptr.size(), 2);
-
-  for (auto const& page : Xy->GetBatches<SparsePage>()) {
-    auto batch = page.GetView();
-    size_t left{0};
-    for (size_t i = 0; i < batch.Size(); ++i) {
-      if (not_sampled(i) && batch[i].front().fvalue < split_value) {
-        left++;
-      }
-    }
-    ASSERT_EQ(left, h_nptr[1] - h_nptr[0]);  // equal to number of sampled assigned to left
-  }
-}
-}  // anonymous namespace
-
-TEST(Approx, LeafPartition) {
-  for (auto n_samples : {0ul, 1ul, 128ul, 256ul}) {
-    TestLeafPartition(n_samples);
-  }
-}
 }  // namespace tree
 }  // namespace xgboost