[web-devel] problem with yesod, persist and enumerations

[Michael Snoyman]

I think you've got very little to fear about here. The GHC team is amazingly
responsive, and addresses issues quickly. For the three that you're bringing
up:

1. It's debatable whether GHC is doing the wrong thing here, and I *think*
there's work going on now to "fix" this problem. (I would also like to see
the current behavior changed.)
2. Well, I just wrote the bug report, so we can't expect much from them
here. But if you think there are no other compilers in wide usage today that
suffer from bugs, you're in for a rude awakening.
3. I'm bad at analogies, so I'll just put it this way: have you seen the
Perl/Python/Ruby multi-threading model? We've got nothing to complain about
here. Plus, there's active work to make it even better.
<prediction>Basically, if you write code today in Haskell versus
Perl/Python/Ruby for multithreading, you'll scale to four cores much better
than they will. And six months from now, you'll scale to eight cores as
well, without changing a line of code.</prediction>

That's not to say you shouldn't bring up your concerns, but I think that
from this perspective Haskell and GHC are in good shape.

Michael

On Sat, Apr 16, 2011 at 8:35 PM, Anton Cheshkov <acheshkov at gmail.com> wrote:

> I worry about the future of haskell (ghc). I know at least three problems
>
> - not memory releasing
> - optimization issues
> - multi-core execution issue  (works bad with more than 4 core)
>
> sadly ... (
>
> 2011/4/16 Michael Snoyman <michael at snoyman.com>
>
>>
>>
>> On Sat, Apr 16, 2011 at 5:54 PM, Chris Casinghino <
>> chris.casinghino at gmail.com> wrote:
>>
>>> On Sat, Apr 16, 2011 at 10:45 AM, Greg Weber <greg at gregweber.info>
>>> wrote:
>>> >  Are you compiling with the development server or doing a cabal build/
>>>
>>> I'm doing a cabal build.  To reproduce this, I run (cabal configure &&
>>> cabal build) from the command line in the project directory.
>>>
>>>
>> I can confirm that this happens. However, it *only* happens when building
>> with cabal. When building with "ghc --make", using runghc or
>> wai-handler-devel, everything works fine. So I tried compiling with "ghc
>> --make -O", and sure enough the same bug appeared.
>>
>> I don't think there's anything we can do in the libraries to avoid this,
>> it looks like a bug in GHC. You can modify your ghc-options line in the
>> cabal file to pass in "-O0" to disable optimizations, though this is
>> obviously not optimal (bad pun intended). I think we need to report this to
>> the GHC team.
>>
>> I know virtually nothing about GHC internals, but in case this means
>> something to someone else, here's some of the output from "ghc --make -O -v
>> test.hs":
>>
>> *** Simplify:
>> *** CorePrep:
>> *** ByteCodeGen:
>> *** Desugar:
>>     Result size = 8699
>> *** Simplifier SimplMode {Phase = InitialPhase [Gentle],
>>                       no inline,
>>                       rules,
>>                       eta-expand,
>>                       no case-of-case} max-iterations=4:
>>     Result size = 9841
>>     Result size = 9797
>>     Result size = 9797
>> *** Specialise:
>>     Result size = 9797
>> *** Float out(FOS {Lam = Just 0, Consts = True, PAPs = False}):
>>     Result size = 13259
>> *** Float inwards:
>>     Result size = 13259
>> *** Simplifier SimplMode {Phase = 2 [main],
>>                       inline,
>>                       rules,
>>                       eta-expand,
>>                       case-of-case} max-iterations=4:
>>     Result size = 677741
>>     Result size = 850762
>>     Result size = 1028928
>>     Result size = 1028928
>> *** Simplifier SimplMode {Phase = 1 [main],
>>                       inline,
>>                       rules,
>>                       eta-expand,
>>                       case-of-case} max-iterations=4:
>>     Result size = 1026905
>>     Result size = 1026876
>>     Result size = 1026876
>> *** Simplifier SimplMode {Phase = 0 [main],
>>                       inline,
>>                       rules,
>>                       eta-expand,
>>                       case-of-case} max-iterations=4:
>>
>> Michael
>>
>> _______________________________________________
>> web-devel mailing list
>> web-devel at haskell.org
>> http://www.haskell.org/mailman/listinfo/web-devel
>>
>>
>
>
> --
> Best regards,
> Cheshkov Anton
> Phone: +7 909 005 18 82
> Skype: cheshkov_anton
>
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