This is very interesting. There was an issue about ultra slow Cairo
output on Mac OS which was due to a bug in cairo. So I thought this
slowness thing is yet another instance of this. The fact that it has
to do with Double to CDouble conversation via GMP Integers is
something we should definitely avoid.
Even if this is fixed in GHC, I'd be more than happy to use a
specialized function in our cairo binding.
Axel.
On 02.11.2011, at 13:00, wagne...@seas.upenn.edu wrote:
> If the problem really is that cFloatConv is using the generic
> fromRational . toRational implementation, then the correct solution is
> to simply _not define cFloatConv_ and use realToFrac everywhere. GHC
> already has tons of specialization rules for realToFrac. However,
> rewrite rules (which are what is generated by a specialization) are
> only syntactic. This, combined with the NOINLINE pragma you have on
> cFloatConv, means that they are never allowed to fire.
>
> ~d
>
> Quoting Eugene Kirpichov <ekirpic...@gmail.com>:
>
>> Sorry for re-sending, my previous attempt got ignored by gtk2hs-devel
>> mailing list as I wasn't subscribed. Now I am.
>>
>> On Wed, Nov 2, 2011 at 3:14 PM, Eugene Kirpichov <ekirpic...@gmail.com
>> >wrote:
>>
>>> Yay!!!
>>>
>>> I made a small change in Types.chs and got my original cairo-
>>> binding-based
>>> program to be just as blazing fast. The only problem I have with
>>> this is
>>> that I used multiparameter type classes.
>>>
>>> Dear gtk2hs team! Is it possible to incorporate my changes? I'm
>>> pretty
>>> sure people will be happy by an order-of-magnitude speedup.
>>> Probably the
>>> stuff could be wrapped in #define's for those who aren't using GHC
>>> and
>>> can't use multiparameter type classes?
>>>
>>> I am pretty sure I could have done the same with rewrite rules,
>>> but I
>>> tried for a while and to no avail.
>>>
>>> FAILED SOLUTION: rewrite rules
>>> cFloatConv :: (RealFloat a, RealFloat b) => a -> b
>>> cFloatConv = realToFrac
>>> {-# NOINLINE cFloatConv #-}
>>> {-# RULES "cFloatConv/float2Double" cFloatConv = float2Double #-}
>>> {-# RULES "cFloatConv/double2Float" cFloatConv = double2Float #-}
>>> {-# RULES "cFloatConv/self" cFloatConv = id #-}
>>>
>>> For some reason, the rules don't fire. Anyone got an idea why?
>>>
>>> SUCCEEDED SOLUTION: multiparameter type classes
>>>
>>> I rewrote cFloatConv like this:
>>>
>>> import GHC.Float
>>> class (RealFloat a, RealFloat b) => CFloatConv a b where
>>> cFloatConv :: a -> b
>>> cFloatConv = realToFrac
>>>
>>> instance CFloatConv Double Double where cFloatConv = id
>>> instance CFloatConv Double CDouble
>>> instance CFloatConv CDouble Double
>>> instance CFloatConv Float Float where cFloatConv = id
>>> instance CFloatConv Float Double where cFloatConv = float2Double
>>> instance CFloatConv Double Float where cFloatConv = double2Float
>>>
>>> and replaced a couple of constraints in functions below by usage of
>>> CFloatConv.
>>>
>>>
>>> On Wed, Nov 2, 2011 at 2:25 PM, Felipe Almeida Lessa <
>>> felipe.le...@gmail.com> wrote:
>>>
>>>> +gtk2hs-devel
>>>>
>>>> On Wed, Nov 2, 2011 at 8:15 AM, Eugene Kirpichov <ekirpic...@gmail.com
>>>> >
>>>> wrote:
>>>>> Any idea how to debug why all the GMP calls?
>>>>> I'm looking at even the auto-generated source for cairo
>>>>> bindings, but I
>>>>> don't see anything at all that could lead to *thousands* of them.
>>>>
>>>> Found them. Look at the Types module and you'll see
>>>>
>>>> cFloatConv :: (RealFloat a, RealFloat b) => a -> b
>>>> cFloatConv = realToFrac
>>>>
>>>> This function (or its cousins peekFloatConv, withFloatConv...) are
>>>> used *everywhere*.
>>>>
>>>> Looking at this module with ghc-core we see that GHC compiled a
>>>> generic version of cFloatConv:
>>>>
>>>> Graphics.Rendering.Cairo.Types.$wcFloatConv
>>>> :: forall a_a3TN b_a3TO.
>>>> (RealFloat a_a3TN, RealFrac b_a3TO) =>
>>>> a_a3TN -> b_a3TO
>>>> [GblId,
>>>> Arity=3,
>>>>
>>>> Unf=Unf{Src=<vanilla>, TopLvl=True, Arity=3, Value=True,
>>>> ConLike=True, Cheap=True, Expandable=True,
>>>> Guidance=IF_ARGS [3 3 0] 12 0}]
>>>> Graphics.Rendering.Cairo.Types.$wcFloatConv =
>>>> \ (@ a_a3TN)
>>>> (@ b_a3TO)
>>>> (w_s5zg :: RealFloat a_a3TN)
>>>> (ww_s5zj :: RealFrac b_a3TO)
>>>> (w1_s5zA :: a_a3TN) ->
>>>> fromRational
>>>> @ b_a3TO
>>>> ($p2RealFrac @ b_a3TO ww_s5zj)
>>>> (toRational
>>>> @ a_a3TN
>>>> ($p1RealFrac
>>>> @ a_a3TN ($p1RealFloat @ a_a3TN w_s5zg))
>>>> w1_s5zA)
>>>>
>>>> Note that this is basically cFloatConv = fromRational . toRational.
>>>>
>>>> *However*, GHC also compiled a Double -> Double specialization:
>>>>
>>>> Graphics.Rendering.Cairo.Types.cFloatConv1
>>>> :: Double -> Double
>>>> [GblId,
>>>> Arity=1,
>>>>
>>>> Unf=Unf{Src=InlineStable, TopLvl=True, Arity=1, Value=True,
>>>> ConLike=True, Cheap=True, Expandable=True,
>>>> Guidance=ALWAYS_IF(unsat_ok=True,boring_ok=False)
>>>> Tmpl= \ (eta_B1 [Occ=Once!] :: Double) ->
>>>> case eta_B1 of _ { D# ww_a5v3 [Occ=Once] ->
>>>> case $w$ctoRational ww_a5v3
>>>> of _ { (# ww2_a5v8 [Occ=Once], ww3_a5v9 [Occ=Once]
>>>> #) ->
>>>> $wfromRat ww2_a5v8 ww3_a5v9
>>>> }
>>>> }}]
>>>> Graphics.Rendering.Cairo.Types.cFloatConv1 =
>>>> \ (eta_B1 :: Double) ->
>>>> case eta_B1 of _ { D# ww_a5v3 ->
>>>> case $w$ctoRational ww_a5v3
>>>> of _ { (# ww2_a5v8, ww3_a5v9 #) ->
>>>> $wfromRat ww2_a5v8 ww3_a5v9
>>>> }
>>>> }
>>>>
>>>> ...which is also equivalent to fromRational . toRational however
>>>> with
>>>> the type class inlined! Oh, god...
>>>>
>>>> Cheers,
>>>>
>>>> --
>>>> Felipe.
>>>>
>>>> _______________________________________________
>>>> Haskell-Cafe mailing list
>>>> haskell-c...@haskell.org
>>>> http://www.haskell.org/mailman/listinfo/haskell-cafe
>>>>
>>>
>>>
>>>
>>> --
>>> Eugene Kirpichov
>>> Principal Engineer, Mirantis Inc. http://www.mirantis.com/
>>> Editor, http://fprog.ru/
>>>
>>
>>
>>
>> --
>> Eugene Kirpichov
>> Principal Engineer, Mirantis Inc. http://www.mirantis.com/
>> Editor, http://fprog.ru/
>>
>
>
>
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