[Haskell-cafe] Fwd: Ridiculously slow FFI, or cairo binding?

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.lessa at gmail.com > wrote: > +gtk2hs-devel > > On Wed, Nov 2, 2011 at 8:15 AM, Eugene Kirpichov <ekirpichov at 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-Cafe at haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > -- Eugene Kirpichov Principal Engineer, Mirantis Inc. http://www.mirantis.com/ Editor, http://fprog.ru/ -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/haskell-cafe/attachments/20111102/cee58eba/attachment.htm>