6.8.3 against DoCon

[Serge D. Mechveliani]

On Wed, Jun 18, 2008 at 02:38:40PM +0100, Ian Lynagh wrote:
> 
> Hi Serge,
> 
> On Wed, Jun 18, 2008 at 04:39:57PM +0400, Serge D. Mechveliani wrote:
> > 
> > But as  ghc-6.8.2  handles DoCon all right, why do not you 
> > investigate this difference in  6.8.3 ?
> 
> We did investigate it - the details are in this trac ticket:
>     http://hackage.haskell.org/trac/ghc/ticket/2328
> but the conclusion was that overall it was best to leave things as they
> are. Unfortunately, this means that performance with GHC 6.8.3 is worse
> for DoCon; hopefully things will be better with 6.10.1!


Yes, I see. Thank you for paying attention to this problem.

I would like to add the following notes about comparison of ghc-6.8.2
and ghc-6.8.3.

1. As you already knew, abot 3 times slow down is visible in making 
   a certain part of DoCon-2.11  -- due to the module  RsePol_.

2. RsePol_.hs  is only about 400 lines, together with comments.
   ghc-6.8.2  suffices          -M80m  to compile  RsePol_.hs.
   ghc-6.8.3  needs more than  -M600m  for this.
   > 7 times loss in space.

There are many computers which have not 600 Mb RAM.

So, DoCon remains with  ghc-6.8.2  -- untill GHC fixes the problem.

Hm ... a small module needs > 600 Mb instead of 80 Mb to compile,
and the release is considered as a progress.
All right, this may occur correct -- if the developers know what 
namely must be fixed, and also know how to fix it. If so, then I could 
believe. 

By the way, not only 6.8.3 looks strange:
even  80 Mb  looks like an un-naturally large minimum for compiling 
this small  RsePol_.hs.
In symbolic computation, in the DoCon test running, in my Dumatel 
prover test, most examples take less than 40 Mb to perform, while I 
write all this in Haskell and do not care much for the code 
optimization. 

Regards,

-----------------
Serge Mechveliani
mechvel at botik.ru