8.2.5 Incorrect tools/flags are utilized

You might find that although you specified a particular tool or flag at configuration time (e.g., with ‘MPICC=mympicompiler’; see configure), the ncptl compiler seems to ignore it. A likely culprit is that an environment variable with the same name as the configuration parameter is set (e.g., the MPICC environment variable may be set to ‘othermpicompiler’) and therefore overrides all prior settings. This situation sometimes arises when a compiler or MPI library is made available using the Environment Modules system (e.g., with the module load command).

The solution is simply to undefine or properly redefine the offending environment variable. In most Unix environments the env command can be used to redefine an environment variable for the duration of a single command:

env MPICC=mympicompiler ncptl --backend=c_mpi myprogram.ncptl