Intel® Software Development tools provide scripts to set the appropriate environment variables for proper execution. In earlier versions of the Intel® Compilers and the Intel® MPI Library, it was best to set the compiler environment variables first, followed by the MPI variables. This was due to the compiler shipping the runtime of the Intel® MPI Library in support of Co-Array Fortran. If the MPI variables were set first, the MPI version sent with the compilers would be found instead of the full MPI SDK.
In the Composer XE 2013 version, the compiler environment variable script now checks to see if the MPI environment variable script has been run and acts accordingly. Now, the order is no longer a factor.