dear Nick, thank you for your answer. modifying LINKFC with mpif77 (build by mpi from xlf_r) works. is it necessary to modify CC, FC and F90 in the CONFIG file? . today I have : CC="cc -q64 -qmaxmem=-1" FC="/usr/bin/xlf_r ...... F90="/usr/bin/xlf_r ...... thank you, Best Wishes, Jean-Pierre Dognon