On Wed, Nov 2, 2011 at 8:15 AM, Eugene Kirpichov
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.