Thanks Mark & David. Issue opened here: https://caml.inria.fr/mantis/view.php?id=7396 On Mon, Oct 31, 2016 at 12:37 AM, Mark Shinwell wrote: > Thanks for the report and bisection. We're looking at this. Please > file a Mantis report in any case. > > Mark > > On 30 October 2016 at 16:49, David Allsopp wrote: > > Berke Durak wrote: > >> I compiled and ran a simple matrix-multiplication-style benchmark > >> program written in imperative style with Bigarrays (see below) > >> using versions 4.01.0, 4.03.0, 4.03.0+flambda, 4.04.0+trunk+flambda > >> (with -version 4.04.0+dev9-2015-09-05), 4.04.0+beta2+flambda > >> (4.04.0+beta2) and 4.05+trunk+flambda (4.05.0+dev0-2016-08-01). > >> > >> Execution time increased by a factor of 2.3 from 4.03+flambda to > >> 4.04+trunk+flambda. I tried a few of the newer optimization > >> switches (-rounds X, -unboxed-types, -unbox-closures, etc.) but > >> that didn't make a significant difference. > >> > >> Execution times, repeatable within ~5%: > >> > >> 4.01.0 5.45s > >> 4.03.0 4.28s > >> 4.03.0+flambda 4.44s > >> 4.04.0+trunk+flambda 10.45s > >> 4.04.0+beta2+flambda 10.72s > >> 4.05.0+trunk+flambda 10.36s > > > > Note that this is specifically an flambda problem - neither 4.04 nor > trunk exhibit the slowdown with flambda disabled. > > > > I've bisected and identified commit f7dcb as the problem (it was added > to trunk after 4.03 was branched). The specific issue is the change in > https://github.com/ocaml/ocaml/blob/trunk/bytecomp/simplif.ml#L473 > disabling conversion of refs to mutable variables when flambda is enabled. > If you remove the `&& Config.flambda = false` and rebuild ocamlopt, you > should find your benchmark speed restored. flambda is supposed to be > performing that optimisation itself, so something is clearly (very) wrong! > > > > Could you open a Mantis PR for this, please? > > > > > > David > > > > -- > > Caml-list mailing list. Subscription management and archives: > > https://sympa.inria.fr/sympa/arc/caml-list > > Beginner's list: http://groups.yahoo.com/group/ocaml_beginners > > Bug reports: http://caml.inria.fr/bin/caml-bugs > -- Berke Durak, VA7OBD (CN88)