7.10.1.20150612
It's very sensitive, I see today. Sometimes it fails with
Simplifier ticks exhausted
other times it works. Bizarre
I think the latter is the more common case and I think the former case has
something to do with existing .o file or order of args and -fforce-recomp
may mean it always works but that is very speculative.
The two casesor
$ time ghc -fno-specialise -O2 Slice.hs
[1 of 1] Compiling Data.Array.Accelerate.CUDA.Array.Slice ( Slice.hs,
Slice.o )
ghc: panic! (the 'impossible' happened)
(GHC version 7.10.1.20150612 for x86_64-apple-darwin):
Simplifier ticks exhausted
When trying UnfoldingDone $j_s1FS5
To increase the limit, use -fsimpl-tick-factor=N (default 100)
If you need to do this, let GHC HQ know, and what factor you needed
To see detailed counts use -ddump-simpl-stats
Total ticks: 1668604
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
real 0m19.714s
user 0m18.264s
sys 0m0.875s
$ time ghc -O2 -fno-specialise Slice.hs
[1 of 1] Compiling Data.Array.Accelerate.CUDA.Array.Slice ( Slice.hs,
Slice.o )
real 0m3.228s
user 0m3.040s
sys 0m0.155s
On Sat, Jun 20, 2015 at 2:03 PM, GHC <ghc-devs@haskell.org> wrote:
> #10491: Regression, simplifier explosion with Accelerate, cannot compile,
> increasing tick factor is not a workaround
> -------------------------------------+-------------------------------------
> Reporter: robertce | Owner:
> Type: bug | Status: new
> Priority: highest | Milestone: 7.10.2
> Component: Compiler | Version: 7.10.1
> 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:
> -------------------------------------+-------------------------------------
>
> Comment (by bgamari):
>
> George, what GHC version did you test `-fno-specialise` on? While
> yesterday I was able to confirm that `-fno-specialise` seemed to make no
> difference on a test machine running what should have been 7.10.1 I am now
> having trouble replicating this on my laptop. Unfortunately I no longer
> have access to the test environment on which I tested this yesterday but
> clearly something was inconsistent.
>
> I am now seeing on multiple machines that `-fno-specialise` indeed allows
> things to compile,
> {{{
> $ ghc -V
> The Glorious Glasgow Haskell Compilation System, version 7.10.1
> $$ time ghc Slice.hs -fforce-recomp -O2 -fno-specialise
> [1 of 1] Compiling Slice ( Slice.hs, Slice.o )
>
> real 0m3.759s
> user 0m1.688s
> sys 0m0.044s
> $ time ghc Slice.hs -fforce-recomp -O2
> [1 of 1] Compiling Slice ( Slice.hs, Slice.o )
> ^C
>
> real 0m51.103s
> user 0m44.336s
> sys 0m0.948s
> }}}
>
> I am now looking at whether disabling only cross-module specialisation is
> enough to eliminate the blow-up.
>
> --
> Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10491#comment:27>
> GHC <http://www.haskell.org/ghc/>
> The Glasgow Haskell Compiler
>
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