Refactor fast-hist, add tests for some updaters. (#3836)

Add unittest for prune.

Add unittest for refresh.

Refactor fast_hist.

* Remove fast_hist_param.
* Rename to quantile_hist.

Add unittests for QuantileHist.

* Refactor QuantileHist into .h and .cc file.
* Remove sync.h.
* Remove MGPU_mock test.

Rename fast hist method to quantile hist.

src/common/hist_util.cc

@@ -4,10 +4,11 @@
  * \brief Utilities to store histograms
  * \author Philip Cho, Tianqi Chen
  */
+#include <rabit/rabit.h>
 #include <dmlc/omp.h>
 #include <numeric>
 #include <vector>
-#include "./sync.h"
+
 #include "./random.h"
 #include "./column_matrix.h"
 #include "./hist_util.h"
@@ -216,7 +217,7 @@ FindGroups(const std::vector<unsigned>& feature_list,
            const std::vector<size_t>& feature_nnz,
            const ColumnMatrix& colmat,
            size_t nrow,
-           const FastHistParam& param) {
+           const tree::TrainParam& param) {
   /* Goal: Bundle features together that has little or no "overlap", i.e.
            only a few data points should have nonzero values for
            member features.
@@ -278,7 +279,7 @@ FindGroups(const std::vector<unsigned>& feature_list,
 inline std::vector<std::vector<unsigned>>
 FastFeatureGrouping(const GHistIndexMatrix& gmat,
                     const ColumnMatrix& colmat,
-                    const FastHistParam& param) {
+                    const tree::TrainParam& param) {
   const size_t nrow = gmat.row_ptr.size() - 1;
   const size_t nfeature = gmat.cut.row_ptr.size() - 1;
 
@@ -332,7 +333,7 @@ FastFeatureGrouping(const GHistIndexMatrix& gmat,
 
 void GHistIndexBlockMatrix::Init(const GHistIndexMatrix& gmat,
                                  const ColumnMatrix& colmat,
-                                 const FastHistParam& param) {
+                                 const tree::TrainParam& param) {
   cut_ = &gmat.cut;
 
   const size_t nrow = gmat.row_ptr.size() - 1;

src/common/hist_util.h

@@ -11,7 +11,6 @@
 #include <limits>
 #include <vector>
 #include "row_set.h"
-#include "../tree/fast_hist_param.h"
 #include "../tree/param.h"
 #include "./quantile.h"
 
@@ -19,8 +18,6 @@ namespace xgboost {
 
 namespace common {
 
-using tree::FastHistParam;
-
 /*! \brief sums of gradient statistics corresponding to a histogram bin */
 struct GHistEntry {
   /*! \brief sum of first-order gradient statistics */
@@ -145,7 +142,7 @@ class GHistIndexBlockMatrix {
  public:
   void Init(const GHistIndexMatrix& gmat,
             const ColumnMatrix& colmat,
-            const FastHistParam& param);
+            const tree::TrainParam& param);
 
   inline GHistIndexBlock operator[](size_t i) const {
     return {blocks_[i].row_ptr_begin, blocks_[i].index_begin};

src/common/io.h

@@ -9,9 +9,9 @@
 #define XGBOOST_COMMON_IO_H_
 
 #include <dmlc/io.h>
+#include <rabit/rabit.h>
 #include <string>
 #include <cstring>
-#include "./sync.h"
 
 namespace xgboost {
 namespace common {

src/common/sync.h

@@ -1,13 +0,0 @@
-/*!
- * Copyright 2014 by Contributors
- * \file sync.h
- * \brief the synchronization module of rabit
- *        redirects to rabit header
- * \author Tianqi Chen
- */
-#ifndef XGBOOST_COMMON_SYNC_H_
-#define XGBOOST_COMMON_SYNC_H_
-
-#include <rabit/rabit.h>
-
-#endif  // XGBOOST_COMMON_SYNC_H_