As of revision:6120, Larceny's implementation of random-integer from SRFI 27 is considerably faster than before. If that has been holding you back, you might want to replace the old versions of lib/SRFI/srfi-27.sch and lib/SRFI/srfi/%3a27.sls with the new ones relative to https://trac.ccs.neu.edu/trac/larceny/browser/trunk/larceny_src/ Will