Separate Depthwidth and Lossguide growing policy in fast histogram (#4102)

* add back train method but mark as deprecated

* add back train method but mark as deprecated

* add back train method but mark as deprecated

* fix scalastyle error

* fix scalastyle error

* fix scalastyle error

* fix scalastyle error

* init

* more changes

* temp

* update

* udpate rabit

* change the histogram

* update kfactor

* sync per node stats

* temp

* update

* final

* code clean

* update rabit

* more cleanup

* fix errors

* fix failed tests

* enforce c++11

* broadcast subsampled feature correctly

* init col

* temp

* col sampling

* fix histmastrix init

* fix col sampling

* remove cout

* fix out of bound access

* fix core dump

remove core dump file

* disbale test temporarily

* update

* add fid

* print perf data

* update

* revert some changes

* temp

* temp

* pass all tests

* bring back some tests

* recover some changes

* fix lint issue

* enable monotone and interaction constraints

* don't specify default for monotone and interactions

* recover column init part

* more recovery

* fix core dumps

* code clean

* revert some changes

* fix test compilation issue

* fix lint issue

* resolve compilation issue

* fix issues of lint caused by rebase

* fix stylistic changes and change variable names

* use regtree internal function

* modularize depth width

* address the comments

* fix failed tests

* wrap perf timers with class

* fix lint

* fix num_leaves count

* fix indention

* Update src/tree/updater_quantile_hist.cc

Co-Authored-By: CodingCat <CodingCat@users.noreply.github.com>

* Update src/tree/updater_quantile_hist.h

Co-Authored-By: CodingCat <CodingCat@users.noreply.github.com>

* Update src/tree/updater_quantile_hist.cc

Co-Authored-By: CodingCat <CodingCat@users.noreply.github.com>

* Update src/tree/updater_quantile_hist.cc

Co-Authored-By: CodingCat <CodingCat@users.noreply.github.com>

* Update src/tree/updater_quantile_hist.cc

Co-Authored-By: CodingCat <CodingCat@users.noreply.github.com>

* Update src/tree/updater_quantile_hist.h

Co-Authored-By: CodingCat <CodingCat@users.noreply.github.com>

* merge

* fix compilation

src/common/hist_util.cc

@@ -1,8 +1,6 @@
 /*!
- * Copyright 2017-2018 by Contributors
+ * Copyright 2017-2019 by Contributors
  * \file hist_util.h
- * \brief Utilities to store histograms
- * \author Philip Cho, Tianqi Chen
  */
 #include <rabit/rabit.h>
 #include <dmlc/omp.h>
@@ -161,6 +159,7 @@ void GHistIndexMatrix::Init(DMatrix* p_fmat, int max_num_bins) {
       SparsePage::Inst inst = batch[i];
 
       CHECK_EQ(ibegin + inst.size(), iend);
+
       for (bst_uint j = 0; j < inst.size(); ++j) {
         uint32_t idx = cut.GetBinIdx(inst[j]);