How do I check the optimisation level of the built-in splitAt? Is something other than -O2 giving me my speed increase?

Ian Lynagh igloo at
Thu May 15 10:05:15 EDT 2008

On Thu, May 15, 2008 at 02:13:32PM +0100, Richard Kelsall wrote:
> Bulat Ziganshin wrote:
> >Hello Simon,
> >
> >>It's hard to tell what optimisation level your libraries were compiled
> >>with.  The default setting is -O, but when building binary distributions 
> >>we
> >>usually set it explicitly to -O2.  If you got your binary from another
> >>source, they might have only used -O.
> >
> >not surprising that noone answered this question in cafe :)
> >
> >actually, main Windows builds goes from Sigbjorn Finne afair. may be
> >from Neil too

The builds were always done on MSR machines, although Sigbjorn used to
bundle them up into installers. These days the MSR machines make the
installers too, with a script from Neil.

> For the record I'm using the Windows version of GHC 6.8.2 downloaded
> from here

I'm pretty sure that's got the libraries built with -O, although I
haven't looked for the log of that actual build.

We only use -O2 on the Linux builds as far as I can see, but I'm not
sure there's a good reason for that. I also don't know why we don't just
make our preferred settings the default in the build system; Simon?


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