October 2015 - ghc-tickets

Re: [GHC] #6166: Performance regression in mwc-random since 7.0.x
by GHC 14 Oct '15

14 Oct '15

#6166: Performance regression in mwc-random since 7.0.x -------------------------------------+------------------------------------- Reporter: bos | Owner: Type: bug | Status: new Priority: high | Milestone: 8.0.1 Component: Compiler | Version: 7.4.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: x86_64 Type of failure: Runtime | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Khudyakov): Does same regression present in latest version of mwc-random? AFAIR performance regression appears because GHC sometimes chose to inline lookup table in where block. It's marked as NOINLINE. It thus was recalculated on each call and caused slowdown. I moved it at top level and problem disapeared. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6166#comment:18> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6166: Performance regression in mwc-random since 7.0.x
by GHC 14 Oct '15

14 Oct '15

#6166: Performance regression in mwc-random since 7.0.x -------------------------------------+------------------------------------- Reporter: bos | Owner: Type: bug | Status: new Priority: high | Milestone: 8.0.1 Component: Compiler | Version: 7.4.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: x86_64 Type of failure: Runtime | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * priority: normal => high Comment: This looks like a pretty serious performance regression, bumping priority. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6166#comment:17> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6166: Performance regression in mwc-random since 7.0.x
by GHC 14 Oct '15

14 Oct '15

#6166: Performance regression in mwc-random since 7.0.x -------------------------------------+------------------------------------- Reporter: bos | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.4.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: x86_64 Type of failure: Runtime | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Description changed by bgamari: Old description: > I've had a report that the performance of the mwc-random package has > regressed seriously after upgrading from GHC 7.0 to 7.4. It turns out > that 7.2 also has the regression. > > Here's a sample program. > > {{{ > import qualified Data.Vector.Unboxed as U > > import qualified System.Random.MWC as R > import System.Random.MWC.Distributions (standard) > > count = 1000 * 1000 > > fast gen = standard gen > > slow gen = standard gen >>= return > > -- Edit this to choose fast or slow. > which gen = slow gen > > main = do > gen <- R.create > v <- U.replicateM count (which gen) > print (U.last v) > }}} > > With GHC 7.0.3 -O2, this runs in 0.294 sec, regardless of whether `fast` > or `slow` is used. > > Under 7.4, `fast` runs in 0.062 sec (a nice speedup!), but `slow` now > takes 9.2 sec (yikes!). > > Roman suggested compiling the `slow` version with `-fno-state-hack`, > which brings performance back up to 0.062 sec. New description: I've had a report that the performance of the mwc-random package has regressed seriously after upgrading from GHC 7.0 to 7.4. It turns out that 7.2 also has the regression. Here's a sample program. {{{#!hs import qualified Data.Vector.Unboxed as U import qualified System.Random.MWC as R import System.Random.MWC.Distributions (standard) count = 1000 * 1000 fast gen = standard gen slow gen = standard gen >>= return -- Edit this to choose fast or slow. which gen = slow gen main = do gen <- R.create v <- U.replicateM count (which gen) print (U.last v) }}} With GHC 7.0.3 -O2, this runs in 0.294 sec, regardless of whether `fast` or `slow` is used. Under 7.4, `fast` runs in 0.062 sec (a nice speedup!), but `slow` now takes 9.2 sec (yikes!). Roman suggested compiling the `slow` version with `-fno-state-hack`, which brings performance back up to 0.062 sec. -- -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6166#comment:16> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5654: Profiling semantics bug
by GHC 14 Oct '15

14 Oct '15

#5654: Profiling semantics bug -------------------------------------+------------------------------------- Reporter: simonmar | Owner: simonmar Type: bug | Status: new Priority: low | Milestone: 8.0.1 Component: Profiling | Version: 7.2.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | profiling/should_run/scc004 Blocked By: | Blocking: Related Tickets: #10007 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * related: => #10007 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5654#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10953: Switch to LLVM 3.7
by GHC 13 Oct '15

13 Oct '15

#10953: Switch to LLVM 3.7 -------------------------------------+------------------------------------- Reporter: erikd | Owner: erikd Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.11 (LLVM) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | -------------------------------------+------------------------------------- LLVM 3.6 is broken on AArch64/Arm64 and LLVM 3.7 was released in August. I already have git master building with LLVM-3.7 on x86_64/linux and can test on numerous others. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10953> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10216: Allow arr ∧ (first ∨ (***)) as minimal definition of Arrow instance
by GHC 13 Oct '15

13 Oct '15

#10216: Allow arr ∧ (first ∨ (***)) as minimal definition of Arrow instance -------------------------------------+------------------------------------- Reporter: strake888 | Owner: ekmett Type: bug | Status: new Priority: normal | Milestone: Component: Core | Version: 7.10.1 Libraries | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10216> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10960: Closed type families don't reduce on data family instances
by GHC 13 Oct '15

13 Oct '15

#10960: Closed type families don't reduce on data family instances -------------------------------------+------------------------------------- Reporter: exFalso | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: closed type | Operating System: Linux family data | Architecture: x86_64 | Type of failure: GHC rejects (amd64) | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following code doesn't compile: {{{#!hs {-# LANGUAGE TypeFamilies #-} module Tmp where data family D a data instance D () = D type family T a where T () = () T a = Char try :: T (D ()) ~ Char => () try = () main :: IO () main = return try }}} giving {{{ Tmp.hs:15:15: Couldn't match expected type ‘Char’ with actual type ‘T (D ())’ In the first argument of ‘return’, namely ‘try’ In the expression: return try In an equation for ‘main’: main = return try }}} Is this a known limitation of closed type families? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10960> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #8010: Add forkOSUnmasked (patch)
by GHC 13 Oct '15

13 Oct '15

#8010: Add forkOSUnmasked (patch) -------------------------------------+------------------------------------- Reporter: joeyadams | Owner: Type: feature request | Status: closed Priority: normal | Milestone: 8.0.1 Component: Core Libraries | Version: 7.7 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by thoughtpolice): * status: patch => closed * resolution: => fixed Comment: Merged, thanks Joey, and sorry this took a ridiculously long time... -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8010#comment:12> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #8010: Add forkOSUnmasked (patch)
by GHC 13 Oct '15

13 Oct '15

#8010: Add forkOSUnmasked (patch) -------------------------------------+------------------------------------- Reporter: joeyadams | Owner: Type: feature request | Status: patch Priority: normal | Milestone: 8.0.1 Component: Core Libraries | Version: 7.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): -------------------------------------+------------------------------------- Comment (by Austin Seipp <austin@…>): In [changeset:"dec5cd4085488686b5ed50bb26ccbc0ba7b645ec/ghc" dec5cd4/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="dec5cd4085488686b5ed50bb26ccbc0ba7b645ec" base: Add forkOSWithUnmask Fixes #8010, according to the specified libraries proposal. [1] Also, some minor wordsmithing. [1] http://thread.gmane.org/gmane.comp.lang.haskell.libraries/22709 Signed-off-by: Austin Seipp <austin(a)well-typed.com> }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8010#comment:11> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10831: DeriveFunctor not capable of deriving when wrapping Either
by GHC 13 Oct '15

13 Oct '15

#10831: DeriveFunctor not capable of deriving when wrapping Either -------------------------------------+------------------------------------- Reporter: htebalaka | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: MacOS X Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- GHC can derive Functor for Okay, but rejects the equivalent Bad. {{{#!hs {-# LANGUAGE DeriveFunctor #-} data Okay f g a b = Inl (f a b) | Inr (g a b) deriving (Functor) newtype Bad f g a b = Bad (Either (f a b) (g a b)) deriving (Functor) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10831> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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