Re: [GHC] #9630: compile-time performance regression (probably due to Generics)

23 Mar 2015

      #9630: compile-time performance regression (probably due to Generics)
-------------------------------------+-------------------------------------
        Reporter:  hvr               |                   Owner:  simonpj
            Type:  bug               |                  Status:  new
        Priority:  high              |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.9
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:  #9583             |  Differential Revisions:
-------------------------------------+-------------------------------------

Comment (by darchon):

 I have another data-point for this performance bug:
 http://hackage.haskell.org/package/unbound-generics. Compiling the
 following example: https://github.com/lambdageek/unbound-
 generics/blob/master/examples/F.hs

 {{{
 $ uname -a
 Darwin wlan022084.mobiel.utwente.nl 14.1.0 Darwin Kernel Version 14.1.0:
 Thu Feb 26 19:26:47 PST 2015;
 root:xnu-2782.10.73~1/RELEASE_X86_64 x86_64

 #############################################################################

 $ ghc --version
 The Glorious Glasgow Haskell Compilation System, version 7.8.4

 $ ghc -O -c -Rghc-timing -fforce-recomp -Wnot F.hs
 <>

 #############################################################################

 $ ghc --version
 The Glorious Glasgow Haskell Compilation System, version 7.10.0.20150323

 $ ghc -O -c -Rghc-timing -fforce-recomp -Wnot F.hs
 <>
 }}}

 The interesting parts of running with -v2 are:

 {{{
 $ ghc --version
 The Glorious Glasgow Haskell Compilation System, version 7.8.4

 $ ghc -O -c -Rghc-timing -fforce-recomp -Wnot -v2 F.hs
 [...]
 Result size of Simplifier
   = {terms: 2,583, types: 8,513, coercions: 1,371}
 *** Specialise:
 Result size of Specialise
   = {terms: 2,583, types: 8,513, coercions: 1,371}
 *** Float out(FOS {Lam = Just 0, Consts = True, PAPs = False}):
 Result size of Float out(FOS {Lam = Just 0,
                               Consts = True,
                               PAPs = False})
   = {terms: 2,923, types: 9,081, coercions: 1,371}
 *** Float inwards:
 Result size of Float inwards
   = {terms: 2,923, types: 9,081, coercions: 1,371}
 *** Simplifier:
 Result size of Simplifier iteration=1
   = {terms: 6,490, types: 31,862, coercions: 17,447}
 [...]

 #############################################################################
 $ ghc --version
 The Glorious Glasgow Haskell Compilation System, version 7.10.0.20150323

 $ ghc -O -c -Rghc-timing -fforce-recomp -Wnot -v2 F.hs
 [...]
 Result size of Simplifier
   = {terms: 2,028, types: 5,759, coercions: 1,207}
 *** Specialise:
 Result size of Specialise
   = {terms: 11,945, types: 48,810, coercions: 9,282}
 *** Float out(FOS {Lam = Just 0, Consts = True, OverSatApps = False}):
 Result size of Float out(FOS {Lam = Just 0,
                               Consts = True,
                               OverSatApps = False})
   = {terms: 14,293, types: 68,412, coercions: 9,282}
 *** Simplifier:
 Result size of Simplifier iteration=1
   = {terms: 22,244, types: 103,329, coercions: 35,450}
 [...]
 }}}

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9630#comment:10
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