Add CMake option to specify hostfile explicitly or not.

CMakeLists.txt

@@ -139,6 +139,8 @@ OPTION(NEKTAR_BUILD_PACKAGES   "Build Nektar++ binary packages" OFF)
 MARK_AS_ADVANCED(NEKTAR_BUILD_PACKAGES)
 
 OPTION(NEKTAR_TEST_ALL "Include full set of regression tests to this build." OFF)
+OPTION(NEKTAR_TEST_USE_HOSTFILE "Use a hostfile to explicitly specify number of
+slots." OFF)
 
 # Meshing utilities and library
 IF (NOT WIN32)

tests/Tester.cpp.in

@@ -215,10 +215,14 @@ int main(int argc, char *argv[])
 	    if (file.GetNProcesses() > 1)
 #endif
         {
-            system("echo 'localhost slots=12' > hostfile");
             command += "@MPIEXEC@ @MPIEXEC_NUMPROC_FLAG@ "
                     + boost::lexical_cast<string>(file.GetNProcesses())
-                    + " -hostfile hostfile ";
+                    + " ";
+            if ("@NEKTAR_TEST_USE_HOSTFILE@" == "ON")
+            {
+                command += " -hostfile hostfile ";
+                system("echo 'localhost slots=12' > hostfile");
+            }
         }
 
         fs::path execPath = startDir / file.GetExecutable();