July 2015 - ghc-tickets

Re: [GHC] #5113: Huge performance regression of 7.0.2, 7.0.3 and HEAD over 7.0.1 and 6.12 (MonoLocalBinds)
by GHC 07 Jul '15

07 Jul '15

#5113: Huge performance regression of 7.0.2, 7.0.3 and HEAD over 7.0.1 and 6.12 (MonoLocalBinds) -------------------------------------+------------------------------------- Reporter: | Owner: daniel.is.fischer | Status: closed Type: bug | Milestone: Priority: normal | Version: 7.0.3 Component: Compiler | Keywords: Resolution: fixed | performance, MonoLocalBinds Operating System: Linux | Architecture: x86 Type of failure: Runtime | Test Case: performance bug | perf/should_run/T5113 Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by bgamari): This is odd as the good and bad cases have identical output from `-ddump- rules` and I can clearly see the rule in the Core output in both cases. For some reason it just never fires in the bad case. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5113#comment:10> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5113: Huge performance regression of 7.0.2, 7.0.3 and HEAD over 7.0.1 and 6.12 (MonoLocalBinds)
by GHC 07 Jul '15

07 Jul '15

#5113: Huge performance regression of 7.0.2, 7.0.3 and HEAD over 7.0.1 and 6.12 (MonoLocalBinds) -------------------------------------+------------------------------------- Reporter: | Owner: daniel.is.fischer | Status: closed Type: bug | Milestone: Priority: normal | Version: 7.0.3 Component: Compiler | Keywords: Resolution: fixed | performance, MonoLocalBinds Operating System: Linux | Architecture: x86 Type of failure: Runtime | Test Case: performance bug | perf/should_run/T5113 Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by bgamari): It seems that this all comes down to a specialisation rule not firing. Namely this one: `Rule fired: SPEC note @ (ST s) ` which happens twice in the good case and never in the bad case. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5113#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5113: Huge performance regression of 7.0.2, 7.0.3 and HEAD over 7.0.1 and 6.12 (MonoLocalBinds)
by GHC 07 Jul '15

07 Jul '15

#5113: Huge performance regression of 7.0.2, 7.0.3 and HEAD over 7.0.1 and 6.12 (MonoLocalBinds) -------------------------------------+------------------------------------- Reporter: | Owner: daniel.is.fischer | Status: closed Type: bug | Milestone: Priority: normal | Version: 7.0.3 Component: Compiler | Keywords: Resolution: fixed | performance, MonoLocalBinds Operating System: Linux | Architecture: x86 Type of failure: Runtime | Test Case: performance bug | perf/should_run/T5113 Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by bgamari): The above bindings are introduced during FloatOut in both the good and bad cases, as expected. The cases diverge in the very next pass (`SimplMode {Phase = 2 [main], inline, rules, eta-expand, case-of-case}`) where they are inlined in the good case but not in the bad. This of course isn't terribly surprising but I thought I'd write it down anyways. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5113#comment:8> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5113: Huge performance regression of 7.0.2, 7.0.3 and HEAD over 7.0.1 and 6.12 (MonoLocalBinds)
by GHC 07 Jul '15

07 Jul '15

#5113: Huge performance regression of 7.0.2, 7.0.3 and HEAD over 7.0.1 and 6.12 (MonoLocalBinds) -------------------------------------+------------------------------------- Reporter: | Owner: daniel.is.fischer | Status: closed Type: bug | Milestone: Priority: normal | Version: 7.0.3 Component: Compiler | Keywords: Resolution: fixed | performance, MonoLocalBinds Operating System: Linux | Architecture: x86 Type of failure: Runtime | Test Case: performance bug | perf/should_run/T5113 Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by bgamari): Unfortunately it seems that simonpj's fix for #10527, 07a1f32e8bacecd450112607df3fdf39e553c91e, again breaks this testcase. The `dump-simpl` output for the testcase both before and after the patch can be found [[https://gist.github.com/bgamari/25785a88152fc174cd4f|here]] -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5113#comment:7> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4945: Another SpecConstr infelicity
by GHC 07 Jul '15

07 Jul '15

#4945: Another SpecConstr infelicity -------------------------------------+------------------------------------- Reporter: batterseapower | Owner: Type: bug | Status: closed Priority: high | Milestone: 7.12.1 Component: Compiler | Version: 7.0.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | simplCore/should_compile/T4945 Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by bgamari): * status: new => closed * resolution: => fixed Comment: Actually, it turns out that thomie's fix to the testcase, 506522c95f5d43db4d469135878c56fe20eb81f6, never made it to the ghc-7.10 branch. This resolves this issue. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4945#comment:13> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4945: Another SpecConstr infelicity
by GHC 07 Jul '15

07 Jul '15

#4945: Another SpecConstr infelicity -------------------------------------+------------------------------------- Reporter: batterseapower | Owner: Type: bug | Status: new Priority: high | Milestone: 7.12.1 Component: Compiler | Version: 7.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | simplCore/should_compile/T4945 Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by bgamari): * status: closed => new * resolution: fixed => Comment: It seems that the patch that caused #10527 is likely responsible for this test suddenly starting to work again. Unfortunately, when we fixed #10527 the test broke again. I'm going to again mark it as `expect_broken` and reopen this ticket. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4945#comment:12> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10414: Buggy behavior with threaded runtime (-N1 working, -N2 getting into <<loop>>)
by GHC 07 Jul '15

07 Jul '15

#10414: Buggy behavior with threaded runtime (-N1 working, -N2 getting into <<loop>>) -------------------------------------+------------------------------------- Reporter: exio4 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Compiling the test case with: ghc -O2 -threaded -eventlog -rtsopts ghc-bug.hs Now, trying with some inputs and -N2 $ ./ghc-bug 7 +RTS -N2 => ghc-bug: <<loop>> $ ./ghc-bug 6 +RTS -N2 => ghc-bug: <<loop>> $ ./ghc-bug 5 +RTS -N2 => 3125 $ ./ghc-bug 5 +RTS -N2 ghc-bug: <<loop>> Reducing the number of capabilities to 1, it works for those inputs $ ./ghc-bug 7 +RTS -N1 As a side-note, the problem only happens randomly with small inputs (on my hardware), and it seems to go away with bigger inputs (the [http://lpaste.net/132564/ original testcase] felt a bit more deterministic, but I think the testcase in the ticket is good enough) I only tested this with GHC 7.8.4 (on Debian), but people on IRC reported the same behavior with GHC 7.10.1 on OS X and Debian Similar bug: [10218] (-fno-cse and -flate-dmd-anal didn't help with this) {{{#!hs import Control.Applicative import Control.Monad import Control.Parallel.Strategies import System.Environment newtype ParList a = ParList { unParList :: [a] } nil :: ParList a nil = ParList [] cons :: a -> ParList a -> ParList a cons x (ParList xs) = ParList (x:xs) instance Functor ParList where fmap = liftM instance Applicative ParList where pure = return (<*>) = ap instance Monad ParList where return = ParList . return {- v code that doesn't work -} (ParList xs) >>= f = ParList (withStrategy (parListChunk 8 rseq) (xs >>= unParList . f)) --(ParList xs) >>= f = ParList (concat (parMap rseq (unParList . f) xs)) {- ^ code that works -} type Pair = (Int, [Int]) loop' :: Pair -> ParList Pair loop' (size,qns) = go 1 where go n | n > size = nil | otherwise = cons (size, n:qns) (go (n+1)) worker :: Int -> Pair -> [Pair] worker n = unParList . go n where go 1 = loop' go n = loop' >=> go (n-1) main :: IO () main = do [n] <- (read <$>) <$> getArgs print $ length (worker n (n,[])) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10414> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4012: Compilation results are not deterministic
by GHC 06 Jul '15

06 Jul '15

#4012: Compilation results are not deterministic -------------------------------------+------------------------------------- Reporter: kili | Owner: niteria Type: bug | Status: new Priority: high | Milestone: 7.12.1 Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Other | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by jb55): * cc: bill@… (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:108> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7450: Regression in optimisation time of functions with many patterns (6.12 to 7.4)?
by GHC 06 Jul '15

06 Jul '15

#7450: Regression in optimisation time of functions with many patterns (6.12 to 7.4)? -------------------------------------+------------------------------------- Reporter: iustin | Owner: bgamari Type: bug | Status: patch Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.6.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: Phab:D1012 -------------------------------------+------------------------------------- Comment (by bgamari): Indeed the implementation of `intsToBitmap` had non-linear behavior due to the accumulation of nested `map` thunks. I've opened Phab:D1041 to resolve this. With this fix the profile for the 4096 constructor testcase looks like this, {{{ total time = 245.76 secs (245764 ticks @ 1000 us, 1 processor) total alloc = 255,033,667,528 bytes (excludes profiling overheads) COST CENTRE MODULE %time %alloc lintAnnots CoreLint 19.8 34.1 FloatOutwards SimplCore 9.7 2.1 flatten.lookup CmmBuildInfoTables 4.8 5.2 simplLetUnfolding Simplify 4.1 2.2 completeBind Simplify 3.9 1.6 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7450#comment:24> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7450: Regression in optimisation time of functions with many patterns (6.12 to 7.4)?
by GHC 06 Jul '15

06 Jul '15

#7450: Regression in optimisation time of functions with many patterns (6.12 to 7.4)? -------------------------------------+------------------------------------- Reporter: iustin | Owner: bgamari Type: bug | Status: patch Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.6.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: Phab:D1012 -------------------------------------+------------------------------------- Comment (by bgamari): In particular most of this appears to be coming from `CmmBuildInfoTables.procpointSRT.bitmap`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7450#comment:23> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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