Can't set GSL_RNG_SEED and GSL_RNG_TYPE within an AMPL session about gsl HOT 3 CLOSED

Hi Bob,

GSL looks for the values of the environment variables GSL_RNG_TYPE and GSL_RNG_SEED in https://github.com/ampl/gsl/blob/master/rng/default.c. In case there were values set for these environment variables, it display the values when the dll is loaded:

ampl: option GSL_RNG_TYPE 'taus'; # use the "taus" generator
ampl: option GSL_RNG_SEED 123;    # initialize the seed to 123
ampl: load amplgsl.dll;
GSL_RNG_TYPE=taus
GSL_RNG_SEED=123

On Linux, option GSL_RNG_TYPE 'taus'; and option GSL_RNG_SEED 123; set the environment variable correctly. However, on Windows this does not happen, and the only workaround appears to be the one you suggested using set GSL_RNG_SEED to set the environment variable manually before starting AMPL. The problem may be in the implementation of the function that sets the options.

Regarding the standard randseed option, it does not appear to have any effect on GSL (even on Linux), and in the implementation I do not see anything that would set the environment variable GSL_RNG_SEED when randseed is set. Since that note refers to AMPL version 20120830, this behavior may have been meanwhile discarded, or at the time GSL loaded these values from some place other than environment variables.

from gsl.

Comment left at https://groups.google.com/d/msg/ampl/xWjhox8FfeQ/guOyWCIbBgAJ:

The gsl libraray has a function called gsl_rng_set which is not included in ampl/gsl. Probably including that function and related files (not sure about the dependency), and rebuild the gsl library can be a way to go.

from gsl.

Added functionality in e4454c1, see https://amplgsl.readthedocs.io/en/latest/amplgsl/rng.html.

from gsl.