fix.

src/c_api/c_api_utils.h

@@ -167,6 +167,7 @@ inline float GetMissing(Json const &config) {
 class XGBoostAPIGuard {
 #if defined(XGBOOST_USE_CUDA)
   int32_t device_id_ {0};
+
   void SetGPUAttribute();
   void RestoreGPUAttribute();
 #else

src/common/column_matrix.h

@@ -1,5 +1,5 @@
 /*!
- * Copyright 2017 by Contributors
+ * Copyright 2017-2022 by Contributors
  * \file column_matrix.h
  * \brief Utility for fast column-wise access
  * \author Philip Cho

src/common/partition_builder.h

@@ -1,5 +1,5 @@
 /*!
- * Copyright 2021 by Contributors
+ * Copyright 2021-2022 by Contributors
  * \file row_set.h
  * \brief Quick Utility to compute subset of rows
  * \author Philip Cho, Tianqi Chen

src/data/ellpack_page_source.cu

@@ -1,5 +1,5 @@
 /*!
- * Copyright 2019-2021 XGBoost contributors
+ * Copyright 2019-2022 XGBoost contributors
  */
 #include <memory>
 #include <utility>
@@ -12,6 +12,13 @@ namespace data {
 void EllpackPageSource::Fetch() {
   dh::safe_cuda(cudaSetDevice(param_.gpu_id));
   if (!this->ReadCache()) {
+    if (count_ != 0 && !sync_) {
+      // source is initialized to be the 0th page during construction, so when count_ is 0
+      // there's no need to increment the source.
+      ++(*source_);
+    }
+    // This is not read from cache so we still need it to be synced with sparse page source.
+    CHECK_EQ(count_, source_->Iter());
     auto const &csr = source_->Page();
     this->page_.reset(new EllpackPage{});
     auto *impl = this->page_->Impl();

src/data/ellpack_page_source.h

@@ -1,5 +1,5 @@
 /*!
- * Copyright 2019-2021 by XGBoost Contributors
+ * Copyright 2019-2022 by XGBoost Contributors
  */
 
 #ifndef XGBOOST_DATA_ELLPACK_PAGE_SOURCE_H_
@@ -25,15 +25,17 @@ class EllpackPageSource : public PageSourceIncMixIn<EllpackPage> {
   std::unique_ptr<common::HistogramCuts> cuts_;
 
  public:
-  EllpackPageSource(
-      float missing, int nthreads, bst_feature_t n_features, size_t n_batches,
-      std::shared_ptr<Cache> cache, BatchParam param,
-      std::unique_ptr<common::HistogramCuts> cuts, bool is_dense,
-      size_t row_stride, common::Span<FeatureType const> feature_types,
-      std::shared_ptr<SparsePageSource> source)
-      : PageSourceIncMixIn(missing, nthreads, n_features, n_batches, cache),
-        is_dense_{is_dense}, row_stride_{row_stride}, param_{std::move(param)},
-        feature_types_{feature_types}, cuts_{std::move(cuts)} {
+  EllpackPageSource(float missing, int nthreads, bst_feature_t n_features, size_t n_batches,
+                    std::shared_ptr<Cache> cache, BatchParam param,
+                    std::unique_ptr<common::HistogramCuts> cuts, bool is_dense, size_t row_stride,
+                    common::Span<FeatureType const> feature_types,
+                    std::shared_ptr<SparsePageSource> source)
+      : PageSourceIncMixIn(missing, nthreads, n_features, n_batches, cache, false),
+        is_dense_{is_dense},
+        row_stride_{row_stride},
+        param_{std::move(param)},
+        feature_types_{feature_types},
+        cuts_{std::move(cuts)} {
     this->source_ = source;
     this->Fetch();
   }

src/data/gradient_index_format.cc

@@ -1,5 +1,5 @@
 /*!
- * Copyright 2021 XGBoost contributors
+ * Copyright 2021-2022 XGBoost contributors
  */
 #include "sparse_page_writer.h"
 #include "gradient_index.h"

src/data/gradient_index_page_source.cc

@@ -1,13 +1,15 @@
 /*!
- * Copyright 2021 by XGBoost Contributors
+ * Copyright 2021-2022 by XGBoost Contributors
  */
 #include "gradient_index_page_source.h"
 
 namespace xgboost {
 namespace data {
 void GradientIndexPageSource::Fetch() {
   if (!this->ReadCache()) {
-    if (count_ != 0) {
+    if (count_ != 0 && !sync_) {
+      // source is initialized to be the 0th page during construction, so when count_ is 0
+      // there's no need to increment the source.
       ++(*source_);
     }
     // This is not read from cache so we still need it to be synced with sparse page source.

src/data/gradient_index_page_source.h

@@ -1,5 +1,5 @@
 /*!
- * Copyright 2021 by XGBoost Contributors
+ * Copyright 2021-2022 by XGBoost Contributors
  */
 #ifndef XGBOOST_DATA_GRADIENT_INDEX_PAGE_SOURCE_H_
 #define XGBOOST_DATA_GRADIENT_INDEX_PAGE_SOURCE_H_
@@ -26,7 +26,7 @@ class GradientIndexPageSource : public PageSourceIncMixIn<GHistIndexMatrix> {
                           common::Span<FeatureType const> feature_types, float sparse_thresh,
                           std::shared_ptr<SparsePageSource> source)
       : PageSourceIncMixIn(missing, nthreads, n_features, n_batches, cache,
-                           !std::isnan(sparse_thresh)),
+                           std::isnan(sparse_thresh)),
         cuts_{std::move(cuts)},
         is_dense_{is_dense},
         max_bin_per_feat_{max_bin_per_feat},

src/data/sparse_page_dmatrix.cc

@@ -169,7 +169,6 @@ BatchSet<GHistIndexMatrix> SparsePageDMatrix::GetGradientIndex(const BatchParam
     auto sorted_sketch = param.regen;
     auto cuts =
         common::SketchOnDMatrix(this, param.max_bin, ctx_.Threads(), sorted_sketch, param.hess);
-    this->InitializeSparsePage();  // reset after use.
 
     batch_param_ = param;
     ghist_index_source_.reset();

src/data/sparse_page_source.h

@@ -292,7 +292,9 @@ class PageSourceIncMixIn : public SparsePageSourceImpl<S> {
  protected:
   std::shared_ptr<SparsePageSource> source_;
   using Super = SparsePageSourceImpl<S>;
-  bool sync_{true};  // synchronize the row page.
+  // synchronize the row page, `hist` and `gpu_hist` don't need the original sparse page
+  // so we avoid fetching it.
+  bool sync_{true};
 
  public:
   PageSourceIncMixIn(float missing, int nthreads, bst_feature_t n_features, uint32_t n_batches,
@@ -307,11 +309,6 @@ class PageSourceIncMixIn : public SparsePageSourceImpl<S> {
 
     ++this->count_;
     this->at_end_ = this->count_ == this->n_batches_;
-    if (this->at_end_) {
-      CHECK_EQ(this->count_, this->n_batches_);
-    } else {
-      CHECK_LT(this->count_, this->n_batches_);
-    }
 
     if (this->at_end_) {
       this->cache_info_->Commit();

src/tree/hist/histogram.h

@@ -1,5 +1,5 @@
 /*!
- * Copyright 2021 by XGBoost Contributors
+ * Copyright 2021-2022 by XGBoost Contributors
  */
 #ifndef XGBOOST_TREE_HIST_HISTOGRAM_H_
 #define XGBOOST_TREE_HIST_HISTOGRAM_H_