Use bst_float consistently throughout (#1824)

* Fix various typos

* Add override to functions that are overridden

gcc gives warnings about functions that are being overridden by not
being marked as oveirridden. This fixes it.

* Use bst_float consistently

Use bst_float for all the variables that involve weight,
leaf value, gradient, hessian, gain, loss_chg, predictions,
base_margin, feature values.

In some cases, when due to additions and so on the value can
take a larger value, double is used.

This ensures that type conversions are minimal and reduces loss of
precision.

src/data/data.cc

@@ -77,12 +77,12 @@ inline bool MetaTryLoadGroup(const std::string& fname,
 
 // try to load weight information from file, if exists
 inline bool MetaTryLoadFloatInfo(const std::string& fname,
-                                 std::vector<float>* data) {
+                                 std::vector<bst_float>* data) {
   std::unique_ptr<dmlc::Stream> fi(dmlc::Stream::Create(fname.c_str(), "r", true));
   if (fi.get() == nullptr) return false;
   dmlc::istream is(fi.get());
   data->clear();
-  float value;
+  bst_float value;
   while (is >> value) {
     data->push_back(value);
   }

src/data/simple_dmatrix.h

@@ -44,7 +44,7 @@ class SimpleDMatrix : public DMatrix {
     return buffered_rowset_;
   }
 
-  size_t GetColSize(size_t cidx) const {
+  size_t GetColSize(size_t cidx) const override {
     return col_size_[cidx];
   }
 

src/data/sparse_batch_page.h

@@ -205,7 +205,7 @@ class SparsePage::Writer {
    * \brief Push a write job to the writer.
    * This function won't block,
    * writing is done by another thread inside writer.
-   * \param page The page to be wriiten
+   * \param page The page to be written
    */
   void PushWrite(std::unique_ptr<SparsePage>&& page);
   /*!

src/data/sparse_page_dmatrix.h

@@ -48,7 +48,7 @@ class SparsePageDMatrix : public DMatrix {
     return buffered_rowset_;
   }
 
-  size_t GetColSize(size_t cidx) const {
+  size_t GetColSize(size_t cidx) const override {
     return col_size_[cidx];
   }
 
@@ -111,7 +111,7 @@ class SparsePageDMatrix : public DMatrix {
     std::vector<SparseBatch::Inst> col_data_;
   };
   /*!
-   * \brief Try to intitialize column data.
+   * \brief Try to initialize column data.
    * \return true if data already exists, false if they do not.
    */
   bool TryInitColData();