Fixed small issue with arh reader.

AMDiS/src/io/ArhReader.cc

@@ -107,6 +107,8 @@ namespace AMDiS {
 
     ifstream file;
     file.open(filename.c_str(), ios::in | ios::binary);
+    TEST_EXIT(file.is_open())
+      ("Cannot open file %s\n", filename.c_str());
 
     string typeId = "";
     uint32_t nMacroElements = 0;
@@ -119,8 +121,8 @@ namespace AMDiS {
     file.read(reinterpret_cast<char*>(&nAllValues), 4);
 
     TEST_EXIT(nValueVectors == vecs.size())
-      ("File has %d vectors, but %d DOFVectors are provided!\n", 
-       nValueVectors, vecs.size());
+      ("File %s has %d vectors, but %d DOFVectors are provided!\n", 
+       filename.c_str(), nValueVectors, vecs.size());
 
     for (unsigned int i = 0; i < nMacroElements; i++) {
       uint32_t elIndex = 0;