What precision should the output verification be carried to - 10 instead of 20 maybe? The GCC C version (the current 'gold standard') gives 1.27422415222861729056 The Ocaml native version gives 1.27422415222861706852 The Ocaml version is currently listed as being in error. http://shootout.alioth.debian.org/sandbox/benchmark.php?test=matrixnorm&lang=all&sort=fullcpu Thanks, - Dave