Extract histogram builder from CPU Hist. (#7152)

* Extract the CPU histogram builder. * Fix tests. * Reduce number of histograms being built.
2021-08-09 21:15:21 +08:00
parent 336af4f974
commit 149f209af6
6 changed files with 647 additions and 676 deletions
--- a/src/common/hist_util.h
+++ b/src/common/hist_util.h
@@ -301,7 +301,7 @@ class HistCollection {
  // access histogram for i-th node
  GHistRowT operator[](bst_uint nid) const {
    constexpr uint32_t kMax = std::numeric_limits<uint32_t>::max();
-    const size_t id = row_ptr_[nid];
+    const size_t id = row_ptr_.at(nid);
    CHECK_NE(id, kMax);
    GradientPairT* ptr = nullptr;
    if (contiguous_allocation_) {