If s is based on the current value of the system clock, the generator output will be different each time. Intrinsic Subroutine Generic: Changes or queries the seed starting point for the pseudorandom number generator used by intrinsic subroutine RANDOM_NUMBER. Intrinsic subroutines cannot be passed as actual arguments. Fortran random seed initialization 30 September, 2019. Fortran 2018 specifies a new subroutine random_init. Gfortran 9 brought initial support for random_init. random_init alternative. To accommodate older compilers without random_init, consider the subroutine below for Linux and MacOS. >In Intel Fortran Compiler for Linux, version 6.0, the call to >random_seed gives the same seed and hence the same random_number >sequence on repeated calls. This is unwelcome behaviour -- contrary >to the spirit of the standard, surely? I'll report it as a bug to >Intel.