more movement to beginptr

src/io/simple_dmatrix-inl.hpp

@@ -54,8 +54,10 @@ class DMatrixSimple : public DataMatrix {
       for (size_t i = 0; i < batch.size; ++i) {
         RowBatch::Inst inst = batch[i];
         row_data_.resize(row_data_.size() + inst.length);
-        memcpy(&row_data_[row_ptr_.back()], inst.data,
-               sizeof(RowBatch::Entry) * inst.length);
+        if (inst.length != 0) {
+          memcpy(&row_data_[row_ptr_.back()], inst.data,
+                 sizeof(RowBatch::Entry) * inst.length);
+        }
         row_ptr_.push_back(row_ptr_.back() + inst.length);
       }
     }
@@ -244,8 +246,8 @@ class DMatrixSimple : public DataMatrix {
       at_first_ = false;
       batch_.size = parent_->row_ptr_.size() - 1;
       batch_.base_rowid = 0;
-      batch_.ind_ptr = &parent_->row_ptr_[0];
-      batch_.data_ptr = &parent_->row_data_[0];
+      batch_.ind_ptr = BeginPtr(parent_->row_ptr_);
+      batch_.data_ptr = BeginPtr(parent_->row_data_);
       return true;
     }
     virtual const RowBatch &Value(void) const {

src/io/simple_fmatrix-inl.hpp

@@ -110,9 +110,9 @@ class FMatrixS : public IFMatrix{
                                 const std::vector<RowBatch::Entry> &data) {
     size_t nrow = ptr.size() - 1;
     fo.Write(&nrow, sizeof(size_t));
-    fo.Write(&ptr[0], ptr.size() * sizeof(size_t));
+    fo.Write(BeginPtr(ptr), ptr.size() * sizeof(size_t));
     if (data.size() != 0) {
-      fo.Write(&data[0], data.size() * sizeof(RowBatch::Entry));
+      fo.Write(BeginPtr(data), data.size() * sizeof(RowBatch::Entry));
     }
   }
   /*!
@@ -127,11 +127,11 @@ class FMatrixS : public IFMatrix{
     size_t nrow;
     utils::Check(fi.Read(&nrow, sizeof(size_t)) != 0, "invalid input file format");
     out_ptr->resize(nrow + 1);
-    utils::Check(fi.Read(&(*out_ptr)[0], out_ptr->size() * sizeof(size_t)) != 0,
+    utils::Check(fi.Read(BeginPtr(*out_ptr), out_ptr->size() * sizeof(size_t)) != 0,
                   "invalid input file format");
     out_data->resize(out_ptr->back());
     if (out_data->size() != 0) {
-      utils::Assert(fi.Read(&(*out_data)[0], out_data->size() * sizeof(RowBatch::Entry)) != 0,
+      utils::Assert(fi.Read(BeginPtr(*out_data), out_data->size() * sizeof(RowBatch::Entry)) != 0,
                     "invalid input file format");
     }
   }
@@ -213,8 +213,8 @@ class FMatrixS : public IFMatrix{
         col_data_[i] = SparseBatch::Inst(&data[0] + ptr[ridx],
                                          static_cast<bst_uint>(ptr[ridx+1] - ptr[ridx]));
       }
-      batch_.col_index = &col_index_[0];
-      batch_.col_data = &col_data_[0];
+      batch_.col_index = BeginPtr(col_index_);
+      batch_.col_data = BeginPtr(col_data_);
       this->BeforeFirst();
     }
     // data content

src/utils/utils.h

@@ -154,6 +154,8 @@ inline FILE *FopenCheck(const char *fname, const char *flag) {
   Check(fp != NULL, "can not open file \"%s\"\n", fname);
   return fp;
 }
+} // namespace utils
+// easy utils that can be directly acessed in xgboost
 /*! \brief get the beginning address of a vector */
 template<typename T>
 inline T *BeginPtr(std::vector<T> &vec) {
@@ -163,6 +165,14 @@ inline T *BeginPtr(std::vector<T> &vec) {
     return &vec[0];
   }
 }
-}  // namespace utils
+/*! \brief get the beginning address of a vector */
+template<typename T>
+inline const T *BeginPtr(const std::vector<T> &vec) {
+  if (vec.size() == 0) {
+    return NULL;
+  } else {
+    return &vec[0];
+  }
+}
 }  // namespace xgboost
 #endif  // XGBOOST_UTILS_UTILS_H_