I think the shootout is not a good data source. There are definitely
some very poor Ocaml results there, so I'd guess the shootout got
recently more attention by enthusiasts of other languages, and the
current Ocaml programs there are not very good. (I remember Ocaml was #1
at the shootout a few years ago, faster than C.) So maybe a good
opportunity to post better Ocaml solutions there?
As Sylvain noticed, some (in not most) of the OCaml poor performances in the shootout are actually not due to bad OCaml programs, but to arbitrary restrictions in the shootout rules. For example, one of the bad-performing benchmark for OCaml is the binary-tree benchmark, where it is nearly four times slower than C, but on closer inspection you discover that this is due to the arbitrary choice to forbid any change of the GC parameters. With appropriate GC parameters, the very same OCaml program is exactly as fast as C.
« Note: these programs are being measured with the default initial heap size - the measurements may be very different with a larger initial heap size or GC tuning. »
C version : 12.11 secs
OCaml version : 47.22 secs
OCaml version with GC parameters tuned ("interesting alternative" section) : 12.67 secs
Therefore, there is nothing that can be changed to the OCaml submission for this benchmark to improve performances, except changing the default GC parameters; while this might be a good idea in general, changing it only for the sake of shootout-obsessed people is ridiculous.