Tests.

src/common/quantile.cc

@@ -359,6 +359,7 @@ void AddCutPoint(typename SketchType::SummaryContainer const &summary, int max_b
                  HistogramCuts *cuts) {
   size_t required_cuts = std::min(summary.size, static_cast<size_t>(max_bin));
   auto &cut_values = cuts->cut_values_.HostVector();
+  // we use the min_value as the first (0th) element, hence starting from 1.
   for (size_t i = 1; i < required_cuts; ++i) {
     bst_float cpt = summary.data[i].value;
     if (i == 1 || cpt > cut_values.back()) {
@@ -419,8 +420,8 @@ void SketchContainerImpl<WQSketch>::MakeCuts(HistogramCuts* cuts) {
     } else {
       AddCutPoint<WQSketch>(a, max_num_bins, cuts);
       // push a value that is greater than anything
-      const bst_float cpt = (a.size > 0) ? a.data[a.size - 1].value
-                                         : cuts->min_vals_.HostVector()[fid];
+      const bst_float cpt =
+          (a.size > 0) ? a.data[a.size - 1].value : cuts->min_vals_.HostVector()[fid];
       // this must be bigger than last value in a scale
       const bst_float last = cpt + (fabs(cpt) + 1e-5f);
       cuts->cut_values_.HostVector().push_back(last);

tests/cpp/helpers.cc

@@ -224,19 +224,18 @@ std::string RandomDataGenerator::GenerateArrayInterface(
   return out;
 }
 
-std::pair<std::vector<std::string>, std::string>
-RandomDataGenerator::GenerateArrayInterfaceBatch(
-    HostDeviceVector<float> *storage, size_t batches) const {
-  this->GenerateDense(storage);
+std::pair<std::vector<std::string>, std::string> MakeArrayInterfaceBatch(
+    HostDeviceVector<float> const* storage, std::size_t n_samples, bst_feature_t n_features,
+    std::size_t batches, std::int32_t device) {
   std::vector<std::string> result(batches);
   std::vector<Json> objects;
 
-  size_t const rows_per_batch = rows_ / batches;
+  size_t const rows_per_batch = n_samples / batches;
 
-  auto make_interface = [storage, this](size_t offset, size_t rows) {
+  auto make_interface = [storage, device, n_features](std::size_t offset, std::size_t rows) {
     Json array_interface{Object()};
     array_interface["data"] = std::vector<Json>(2);
-    if (device_ >= 0) {
+    if (device >= 0) {
       array_interface["data"][0] =
           Integer(reinterpret_cast<int64_t>(storage->DevicePointer() + offset));
       array_interface["stream"] = Null{};
@@ -249,22 +248,22 @@ RandomDataGenerator::GenerateArrayInterfaceBatch(
 
     array_interface["shape"] = std::vector<Json>(2);
     array_interface["shape"][0] = rows;
-    array_interface["shape"][1] = cols_;
+    array_interface["shape"][1] = n_features;
 
     array_interface["typestr"] = String("<f4");
     array_interface["version"] = 3;
     return array_interface;
   };
 
-  auto j_interface = make_interface(0, rows_);
+  auto j_interface = make_interface(0, n_samples);
   size_t offset = 0;
   for (size_t i = 0; i < batches - 1; ++i) {
     objects.emplace_back(make_interface(offset, rows_per_batch));
-    offset += rows_per_batch * cols_;
+    offset += rows_per_batch * n_features;
   }
 
-  size_t const remaining = rows_ - offset / cols_;
-  CHECK_LE(offset, rows_ * cols_);
+  size_t const remaining = n_samples - offset / n_features;
+  CHECK_LE(offset, n_samples * n_features);
   objects.emplace_back(make_interface(offset, remaining));
 
   for (size_t i = 0; i < batches; ++i) {
@@ -276,6 +275,12 @@ RandomDataGenerator::GenerateArrayInterfaceBatch(
   return {result, interface_str};
 }
 
+std::pair<std::vector<std::string>, std::string> RandomDataGenerator::GenerateArrayInterfaceBatch(
+    HostDeviceVector<float>* storage, size_t batches) const {
+  this->GenerateDense(storage);
+  return MakeArrayInterfaceBatch(storage, rows_, cols_, batches, device_);
+}
+
 std::string RandomDataGenerator::GenerateColumnarArrayInterface(
     std::vector<HostDeviceVector<float>> *data) const {
   CHECK(data);
@@ -400,11 +405,14 @@ int NumpyArrayIterForTest::Next() {
   return 1;
 }
 
-std::shared_ptr<DMatrix>
-GetDMatrixFromData(const std::vector<float> &x, int num_rows, int num_columns){
+std::shared_ptr<DMatrix> GetDMatrixFromData(const std::vector<float>& x, std::size_t num_rows,
+                                            bst_feature_t num_columns) {
   data::DenseAdapter adapter(x.data(), num_rows, num_columns);
-  return std::shared_ptr<DMatrix>(new data::SimpleDMatrix(
-      &adapter, std::numeric_limits<float>::quiet_NaN(), 1));
+  auto p_fmat = std::shared_ptr<DMatrix>(
+      new data::SimpleDMatrix(&adapter, std::numeric_limits<float>::quiet_NaN(), 1));
+  CHECK_EQ(p_fmat->Info().num_row_, num_rows);
+  CHECK_EQ(p_fmat->Info().num_col_, num_columns);
+  return p_fmat;
 }
 
 std::unique_ptr<DMatrix> CreateSparsePageDMatrix(bst_row_t n_samples, bst_feature_t n_features,
@@ -572,12 +580,23 @@ std::unique_ptr<GradientBooster> CreateTrainedGBM(std::string name, Args kwargs,
   return gbm;
 }
 
-ArrayIterForTest::ArrayIterForTest(float sparsity, size_t rows, size_t cols,
-                                   size_t batches) : rows_{rows}, cols_{cols}, n_batches_{batches} {
+ArrayIterForTest::ArrayIterForTest(float sparsity, size_t rows, size_t cols, size_t batches)
+    : rows_{rows}, cols_{cols}, n_batches_{batches} {
   XGProxyDMatrixCreate(&proxy_);
   rng_.reset(new RandomDataGenerator{rows_, cols_, sparsity});
+  std::tie(batches_, interface_) = rng_->GenerateArrayInterfaceBatch(&data_, n_batches_);
+}
+
+ArrayIterForTest::ArrayIterForTest(Context const* ctx, HostDeviceVector<float> const& data,
+                                   std::size_t n_samples, bst_feature_t n_features,
+                                   std::size_t n_batches)
+    : rows_{n_samples}, cols_{n_features}, n_batches_{n_batches} {
+  XGProxyDMatrixCreate(&proxy_);
+  this->data_.Resize(data.Size());
+  CHECK_EQ(this->data_.Size(), rows_ * cols_ * n_batches);
+  this->data_.Copy(data);
   std::tie(batches_, interface_) =
-      rng_->GenerateArrayInterfaceBatch(&data_, n_batches_);
+      MakeArrayInterfaceBatch(&data_, rows_, cols_, n_batches_, ctx->gpu_id);
 }
 
 ArrayIterForTest::~ArrayIterForTest() { XGDMatrixFree(proxy_); }

tests/cpp/helpers.h

@@ -188,7 +188,7 @@ class SimpleRealUniformDistribution {
 };
 
 template <typename T>
-Json GetArrayInterface(HostDeviceVector<T> *storage, size_t rows, size_t cols) {
+Json GetArrayInterface(HostDeviceVector<T> const* storage, size_t rows, size_t cols) {
   Json array_interface{Object()};
   array_interface["data"] = std::vector<Json>(2);
   if (storage->DeviceCanRead()) {
@@ -318,8 +318,8 @@ GenerateRandomCategoricalSingleColumn(int n, size_t num_categories) {
   return x;
 }
 
-std::shared_ptr<DMatrix> GetDMatrixFromData(const std::vector<float> &x,
-                                            int num_rows, int num_columns);
+std::shared_ptr<DMatrix> GetDMatrixFromData(const std::vector<float>& x, std::size_t num_rows,
+                                            bst_feature_t num_columns);
 
 /**
  * \brief Create Sparse Page using data iterator.
@@ -394,7 +394,7 @@ typedef void *DMatrixHandle;  // NOLINT(*);
 class ArrayIterForTest {
  protected:
   HostDeviceVector<float> data_;
-  size_t iter_ {0};
+  size_t iter_{0};
   DMatrixHandle proxy_;
   std::unique_ptr<RandomDataGenerator> rng_;
 
@@ -418,6 +418,11 @@ class ArrayIterForTest {
   auto Proxy() -> decltype(proxy_) { return proxy_; }
 
   explicit ArrayIterForTest(float sparsity, size_t rows, size_t cols, size_t batches);
+  /**
+   * \brief Create iterator with user provided data.
+   */
+  explicit ArrayIterForTest(Context const* ctx, HostDeviceVector<float> const& data,
+                            std::size_t n_samples, bst_feature_t n_features, std::size_t n_batches);
   virtual ~ArrayIterForTest();
 };
 
@@ -433,6 +438,10 @@ class NumpyArrayIterForTest : public ArrayIterForTest {
  public:
   explicit NumpyArrayIterForTest(float sparsity, size_t rows = Rows(), size_t cols = Cols(),
                                  size_t batches = Batches());
+  explicit NumpyArrayIterForTest(Context const* ctx, HostDeviceVector<float> const& data,
+                                 std::size_t n_samples, bst_feature_t n_features,
+                                 std::size_t n_batches)
+      : ArrayIterForTest{ctx, data, n_samples, n_features, n_batches} {}
   int Next() override;
   ~NumpyArrayIterForTest() override = default;
 };

tests/cpp/predictor/test_cpu_predictor.cc

@@ -305,4 +305,10 @@ TEST(CpuPredictor, Sparse) {
   TestSparsePrediction(0.2, "cpu_predictor");
   TestSparsePrediction(0.8, "cpu_predictor");
 }
+
+TEST(CpuPredictor, Multi) {
+  Context ctx;
+  ctx.nthread = 1;
+  TestVectorLeafPrediction(&ctx);
+}
 }  // namespace xgboost

tests/cpp/predictor/test_predictor.cc

@@ -1,28 +1,34 @@
-/*!
- * Copyright 2020-2021 by Contributors
+/**
+ * Copyright 2020-2023 by XGBoost Contributors
  */
-
 #include "test_predictor.h"
 
 #include <gtest/gtest.h>
-#include <xgboost/context.h>
-#include <xgboost/data.h>
-#include <xgboost/host_device_vector.h>
-#include <xgboost/predictor.h>
-
-#include "../../../src/common/bitfield.h"
-#include "../../../src/common/categorical.h"
-#include "../../../src/common/io.h"
-#include "../../../src/data/adapter.h"
-#include "../../../src/data/proxy_dmatrix.h"
-#include "../helpers.h"
+#include <xgboost/context.h>                      // for Context
+#include <xgboost/data.h>                         // for DMatrix, BatchIterator, BatchSet, MetaInfo
+#include <xgboost/host_device_vector.h>           // for HostDeviceVector
+#include <xgboost/predictor.h>                    // for PredictionCacheEntry, Predictor, Predic...
+
+#include <algorithm>                              // for max
+#include <limits>                                 // for numeric_limits
+#include <unordered_map>                          // for unordered_map
+
+#include "../../../src/common/bitfield.h"         // for LBitField32
+#include "../../../src/data/iterative_dmatrix.h"  // for IterativeDMatrix
+#include "../../../src/data/proxy_dmatrix.h"      // for DMatrixProxy
+#include "../helpers.h"                           // for GetDMatrixFromData, RandomDataGenerator
+#include "xgboost/json.h"                         // for Json, Object, get, String
+#include "xgboost/linalg.h"                       // for MakeVec, Tensor, TensorView, Vector
+#include "xgboost/logging.h"                      // for CHECK
+#include "xgboost/span.h"                         // for operator!=, SpanIterator, Span
+#include "xgboost/tree_model.h"                   // for RegTree
 
 namespace xgboost {
 TEST(Predictor, PredictionCache) {
   size_t constexpr kRows = 16, kCols = 4;
 
   PredictionContainer container;
-  DMatrix* m;
+  DMatrix *m;
   // Add a cache that is immediately expired.
   auto add_cache = [&]() {
     auto p_dmat = RandomDataGenerator(kRows, kCols, 0).GenerateDMatrix();
@@ -412,4 +418,101 @@ void TestSparsePrediction(float sparsity, std::string predictor) {
     }
   }
 }
+
+void TestVectorLeafPrediction(Context const *ctx) {
+  std::unique_ptr<Predictor> cpu_predictor =
+      std::unique_ptr<Predictor>(Predictor::Create("cpu_predictor", ctx));
+
+  size_t constexpr kRows = 5;
+  size_t constexpr kCols = 5;
+
+  LearnerModelParam mparam{static_cast<bst_feature_t>(kCols),
+                           linalg::Vector<float>{{0.5}, {1}, Context::kCpuId}, 1, 3,
+                           MultiStrategy::kMonolithic};
+
+  std::vector<std::unique_ptr<RegTree>> trees;
+  trees.emplace_back(new RegTree{mparam.LeafLength(), mparam.num_feature});
+
+  std::vector<float> p_w(mparam.LeafLength(), 0.0f);
+  std::vector<float> l_w(mparam.LeafLength(), 1.0f);
+  std::vector<float> r_w(mparam.LeafLength(), 2.0f);
+
+  auto &tree = trees.front();
+  tree->ExpandNode(0, static_cast<bst_feature_t>(1), 2.0, true,
+                   linalg::MakeVec(p_w.data(), p_w.size()), linalg::MakeVec(l_w.data(), l_w.size()),
+                   linalg::MakeVec(r_w.data(), r_w.size()));
+  ASSERT_TRUE(tree->IsMultiTarget());
+  ASSERT_TRUE(mparam.IsVectorLeaf());
+
+  gbm::GBTreeModel model{&mparam, ctx};
+  model.CommitModel(std::move(trees), 0);
+
+  auto run_test = [&](float expected, HostDeviceVector<float> *p_data) {
+    {
+      auto p_fmat = GetDMatrixFromData(p_data->ConstHostVector(), kRows, kCols);
+      PredictionCacheEntry predt_cache;
+      cpu_predictor->InitOutPredictions(p_fmat->Info(), &predt_cache.predictions, model);
+      ASSERT_EQ(predt_cache.predictions.Size(), kRows * mparam.LeafLength());
+      cpu_predictor->PredictBatch(p_fmat.get(), &predt_cache, model, 0, 1);
+      auto const &h_predt = predt_cache.predictions.HostVector();
+      for (auto v : h_predt) {
+        ASSERT_EQ(v, expected);
+      }
+    }
+
+    {
+      // inplace
+      PredictionCacheEntry predt_cache;
+      auto p_fmat = GetDMatrixFromData(p_data->ConstHostVector(), kRows, kCols);
+      cpu_predictor->InitOutPredictions(p_fmat->Info(), &predt_cache.predictions, model);
+      auto arr = GetArrayInterface(p_data, kRows, kCols);
+      std::string str;
+      Json::Dump(arr, &str);
+      auto proxy = std::shared_ptr<DMatrix>(new data::DMatrixProxy{});
+      dynamic_cast<data::DMatrixProxy *>(proxy.get())->SetArrayData(str.data());
+      cpu_predictor->InplacePredict(proxy, model, std::numeric_limits<float>::quiet_NaN(),
+                                    &predt_cache, 0, 1);
+      auto const &h_predt = predt_cache.predictions.HostVector();
+      for (auto v : h_predt) {
+        ASSERT_EQ(v, expected);
+      }
+    }
+
+    {
+      // ghist
+      PredictionCacheEntry predt_cache;
+      auto &h_data = p_data->HostVector();
+      // give it at least two bins, otherwise the histogram cuts only have min and max values.
+      for (std::size_t i = 0; i < 5; ++i) {
+        h_data[i] = 1.0;
+      }
+      auto p_fmat = GetDMatrixFromData(p_data->ConstHostVector(), kRows, kCols);
+
+      cpu_predictor->InitOutPredictions(p_fmat->Info(), &predt_cache.predictions, model);
+
+      auto iter = NumpyArrayIterForTest{ctx, *p_data, kRows, static_cast<bst_feature_t>(kCols),
+                                        static_cast<std::size_t>(1)};
+      p_fmat =
+          std::make_shared<data::IterativeDMatrix>(&iter, iter.Proxy(), nullptr, Reset, Next,
+                                                   std::numeric_limits<float>::quiet_NaN(), 0, 256);
+
+      cpu_predictor->InitOutPredictions(p_fmat->Info(), &predt_cache.predictions, model);
+      cpu_predictor->PredictBatch(p_fmat.get(), &predt_cache, model, 0, 1);
+      auto const &h_predt = predt_cache.predictions.HostVector();
+      // the smallest v uses the min_value from histogram cuts, which leads to a left leaf
+      // during prediction.
+      for (std::size_t i = 5; i < h_predt.size(); ++i) {
+        ASSERT_EQ(h_predt[i], expected) << i;
+      }
+    }
+  };
+
+  // go to right
+  HostDeviceVector<float> data(kRows * kCols, model.trees.front()->SplitCond(RegTree::kRoot) + 1.0);
+  run_test(2.5, &data);
+
+  // go to left
+  data.HostVector().assign(data.Size(), model.trees.front()->SplitCond(RegTree::kRoot) - 1.0);
+  run_test(1.5, &data);
+}
 }  // namespace xgboost

tests/cpp/predictor/test_predictor.h

@@ -1,9 +1,16 @@
+/**
+ * Copyright 2020-2023 by XGBoost Contributors
+ */
 #ifndef XGBOOST_TEST_PREDICTOR_H_
 #define XGBOOST_TEST_PREDICTOR_H_
 
+#include <xgboost/context.h>  // for Context
 #include <xgboost/predictor.h>
-#include <string>
+
 #include <cstddef>
+#include <string>
+
+#include "../../../src/gbm/gbtree_model.h"  // for GBTreeModel
 #include "../helpers.h"
 
 namespace xgboost {
@@ -48,7 +55,7 @@ void TestPredictionFromGradientIndex(std::string name, size_t rows, size_t cols,
     PredictionCacheEntry precise_out_predictions;
     predictor->InitOutPredictions(p_dmat->Info(), &precise_out_predictions.predictions, model);
     predictor->PredictBatch(p_dmat.get(), &precise_out_predictions, model, 0);
-    ASSERT_FALSE(p_dmat->PageExists<Page>());
+    CHECK(!p_dmat->PageExists<Page>());
   }
 }
 
@@ -69,6 +76,8 @@ void TestCategoricalPredictLeaf(StringView name);
 void TestIterationRange(std::string name);
 
 void TestSparsePrediction(float sparsity, std::string predictor);
+
+void TestVectorLeafPrediction(Context const* ctx);
 }  // namespace xgboost
 
 #endif  // XGBOOST_TEST_PREDICTOR_H_