[Haskell-beginners] Integer performance of GHC

Sebastián E. Peyrott pseus7 at gmail.com
Sat Aug 7 13:52:38 EDT 2010

Thanks for the links. I had already seen Don's post, but I have yet to
try the LLVM backend. I'll do so as soon as a stable GHC version with
it is out.

The Haskell math performance link is interesting. If I'm not mistaken,
the OP achieved C levels of performance by switching to Data.Vector
and keeping data structures as close to C as possible. That seems
reasonable. However, for the example I gave earlier (an MD5
implementation), I don't see a way to use Data.Vector. The algorithm
performs repeated operations on 4 32-bit integers and that's it. The
implementation in Happstack is as close to C as possible, yet it's
still slower. My own too.

I've been trying to read the generated Core and assembly but I don't
really have any experience doing that. I can see most fields are
unboxed and inlining appears to be working. I see repeated calls to
GHC.Prim.narrow32Word# too. In the generated assembly I see many
operations with literal '$4294967295'. Could that be the culprit?

I have uploaded the generated Core for the main MD5 computation
(RFC1321, section 3.4) here: http://pastebin.com/e51njdcS
The actual computation starts at line 1507. Please note this is not
from the version in Happstack but rather from my own. You can find
RFC1321 here: http://tools.ietf.org/html/rfc1321

If you feel talking about Core and assembly is perhaps not suitable
for Haskell-beginners, I'll move this discussion to Haskell-cafe.


2010/8/7 David Virebayre <dav.vire+haskell at gmail.com>:
> 2010/8/7 Sebastián E. Peyrott <pseus7 at gmail.com>:
>> Hi, I'm looking for information on Haskell's viability for heavy
>> integer math. My (very) naive tests show Haskell lagging behind C even
> Relevant links :
> Benefits of the LLVM code generator (lots of other relevant posts on Dons' blog)
> http://donsbot.wordpress.com/2010/02/21/smoking-fast-haskell-code-using-ghcs-new-llvm-codegen/
> Archive of threads about loop unrolling :
> http://www.haskell.org/pipermail/glasgow-haskell-users/2009-March/thread.html#16741
> (Also check some of the links in "You might also be interested in:")
> http://efreedom.com/Question/1-2978979/Haskell-math-performance
> David.

More information about the Beginners mailing list