quick fix

src/io/dmlc_simple.cpp

@@ -10,7 +10,8 @@ namespace xgboost {
 namespace utils {
 class SingleFileSplit : public dmlc::InputSplit {
  public:
-  explicit SingleFileSplit(const char *fname) {
+  explicit SingleFileSplit(const char *fname) 
+      : use_stdin_(false) {
     if (!std::strcmp(fname, "stdin")) {
 #ifndef XGBOOST_STRICT_CXX98_
       use_stdin_ = true; fp_ = stdin;

src/io/simple_fmatrix-inl.hpp

@@ -192,8 +192,10 @@ class FMatrixS : public IFMatrix{
     bst_omp_uint ncol = static_cast<bst_omp_uint>(this->NumCol());
     #pragma omp parallel for schedule(static)
     for (bst_omp_uint i = 0; i < ncol; ++i) {
-      std::sort(&col_data_[0] + col_ptr_[i],
-                &col_data_[0] + col_ptr_[i + 1], Entry::CmpValue);
+      if (col_ptr_[i] < col_ptr_[i + 1]) {
+        std::sort(BeginPtr(col_data_) + col_ptr_[i],
+                  BeginPtr(col_data_) + col_ptr_[i + 1], Entry::CmpValue);
+      }
     }
   }