Benchmarking GHC

Simon Marlow simonmar at
Fri Oct 20 07:12:29 EDT 2006

Bulat Ziganshin wrote:
> Hello Simon,
> Friday, October 20, 2006, 1:38:39 PM, you wrote:
>>> -O2 -funbox-strict-fields
>> I'm not sure that -funbox-strict-fields always improves performance,
> we search for solution that improves performance ON AVERAGE

Not really: would you turn on an optimisation that makes 100 programs 1%
better, and 1 program 200% worse?  I'm being slightly hypocritical
because we already do that kind of thing with full laziness.  But the
rule of thumb should be that -O/-O2 never takes risks that might
seriously hurt performance.  I'd say -funbox-strict-fields is too much
of a risk to have on by default, but it's a difficult call to make.
Measurements over lots of programs would help us decide - the nofib
suite isn't much good here because most of the programs are from a time
before strict fields were invented.


More information about the Glasgow-haskell-users mailing list