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Today's Topics:
1. Re: the flag -N2 requires the program to be built with
-threaded (Jung Kim)
2. Re: let x = x in x (GHC.Prim) (Takenobu Tani)
3. Re: let x = x in x (GHC.Prim) (John Ky)
----------------------------------------------------------------------
Message: 1
Date: Wed, 23 Mar 2016 20:34:41 +0800
From: Jung Kim <jung...@gmail.com>
To: sumit.sahrawat.ap...@iitbhu.ac.in, The Haskell-Beginners Mailing
List - Discussion of primarily beginner-level topics related to
Haskell <beginners@haskell.org>
Subject: Re: [Haskell-beginners] the flag -N2 requires the program to
be built with -threaded
Message-ID:
<cabmbna2fatagpo6cfzrfg9wqvtfudym0r+ptd78jajcvm7u...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
I changed to the suggested solution and that fixes the problem. Thank
you very much!
On 23 March 2016 at 14:25, Sumit Sahrawat, Maths & Computing, IIT
(BHU) <sumit.sahrawat.ap...@iitbhu.ac.in> wrote:
> As there are a lot of options, ghc has a `--show-options` flag which shows
> them all. The `-threaded` flag is to be passed to ghc.
> I think the second command in the `all` block is redundant, as `ghc -O
> mvar.hs` should produce a binary named mvar.
>
> This should work:
>
> all:
> ghc -O -threaded mvar.hs
>
> Regards,
> Sumit
>
> On 23 March 2016 at 10:49, Jung Kim <jung...@gmail.com> wrote:
>>
>> I am currently reading an article[1] where the author uses Haskell to
>> explain her idea. The problem is I don't understand Haskell and am not
>> familiar with Haskell concept like MVar, IVar, etc. (I can get the
>> code compile, and have several years programming experiences.)
>>
>> When testing the code, it throws the error messages "the flag -N2
>> requires the program to be built with -threaded"; however I can't find
>> thread related flag with ghc command by `ghc --help`. How can I fix
>> this problem?
>>
>> Environment I use: Debian stretch/sid, kernel 4.0.0-2-rt-686-pae, GHC
>> version 7.10.3.
>>
>> The code is exactly the same as described in the section
>> 'Nondeterminism with MVars' of article; and the makefile content is
>>
>> all:
>> ghc -O mvar.hs
>> ghc -o mvar mvar.o
>> run:
>> ./execute # while true; do ./mvar +RTS -N2; done
>> clean:
>> rm mvar
>>
>> Thanks
>>
>> [1].
>> http://composition.al/blog/2013/09/22/some-example-mvar-ivar-and-lvar-programs-in-haskell/
>> _______________________________________________
>> Beginners mailing list
>> Beginners@haskell.org
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
>
>
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------------------------------
Message: 2
Date: Wed, 23 Mar 2016 23:20:09 +0900
From: Takenobu Tani <takenobu...@gmail.com>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <beginners@haskell.org>
Subject: Re: [Haskell-beginners] let x = x in x (GHC.Prim)
Message-ID:
<CAPB_Nvy+bh71Z_nGvdWGtEwZLwZpwPQzdpy2w8iMe_G=ftt...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hi John,
> popCnt64# = let x = x in x
It represents "bottom, or undefined, or infinite loop" [1].
(Almost primitives can't be represented with Haskell language.)
In your case, It's good to use FFI call [2] like as Sylvain's nice code.
If you dig GHC compiler's primitives, followings [3][4] may be useful.
[1] https://www.fpcomplete.com/blog/2015/02/primitive-haskell
[2]
https://downloads.haskell.org/~ghc/master/users-guide/ffi-chap.html#primitive-imports
[3] https://ghc.haskell.org/trac/ghc/wiki/Commentary/PrimOps
[4] http://www.well-typed.com/blog/2014/06/understanding-the-realworld/
Cheers,
Takenobu
2016-03-23 10:10 GMT+09:00 Sylvain Henry <sylv...@haskus.fr>:
> Hi,
>
> You can also test your primop with a foreign primop.
>
> See here for an example of assembly code (calling cpuid):
>
> https://github.com/hsyl20/ViperVM/blob/master/src/lib/ViperVM/Arch/X86_64/cpuid.c
>
> And here for the Haskell part with the foreign primop that calls the
> assembly code:
>
> https://github.com/hsyl20/ViperVM/blob/master/src/lib/ViperVM/Arch/X86_64/Cpuid.hs#L56
>
> Cheers,
> Sylvain
>
>
> On 23/03/2016 02:07, rahulm...@gmail.com wrote:
>
> Hi John,
>
> ghc-prim is just a stub package generated for the purpose of
> documentation. All primops are defined in a low level language called Cmm
> in GHC. If you want to make it even faster, you'll need to learn Cmm and
> update the definition in GHC. If you want to a specialized implementation
> for x86 systems, you may need to modify the NCG (Native Code Generator)
> which requires a knowledge of assembly language.
>
> Hope that helps!
> Rahul Muttineni
>
> Sent from my BlackBerry 10 smartphone.
> *From: *John Ky
> *Sent: *Wednesday 23 March 2016 4:40 AM
> *To: *The Haskell-Beginners Mailing List - Discussion of primarily
> beginner-level topics related to Haskell
> *Reply To: *The Haskell-Beginners Mailing List - Discussion of primarily
> beginner-level topics related to Haskell
> *Subject: *[Haskell-beginners] let x = x in x (GHC.Prim)
>
> Hello Haskellers,
>
> I'm trying to write a faster popCount function for x86 systems.
>
> I tried cloning the ghc-prim package and repurposing it for my own needs,
> but it isn't working as hoped.
>
> In particular, popCnt64# was implemented in GHC.Prim as:
>
> popCnt64# = let x = x in x
>
> Which shouldn't terminate. Yet when I call it, it magically finds the C
> implementation in hs_popcnt64 and returns the correct value.
>
> My cloned project doesn't behave that way. Instead it doesn't terminate
> as I would expect.
>
> Anyone know what's happening here, if there is a way to make this work or
> tell me if I'm going about this completely the wrong way?
>
> Cheers,
>
> -John
>
>
>
>
> _______________________________________________
> Beginners mailing
> listBeginners@haskell.orghttp://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
>
>
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>
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Message: 3
Date: Wed, 23 Mar 2016 21:28:23 +0000
From: John Ky <newho...@gmail.com>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <beginners@haskell.org>
Subject: Re: [Haskell-beginners] let x = x in x (GHC.Prim)
Message-ID:
<camb4o-d4bpz881yx02aqvtou0ourdofpe47vltzvhtyvw_w...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hi Rahul,
I see mention of the popcount instruction in nativeGen/X86/CodeGen.hs. In
particular it looks like it only activates if sse4_2 is activated? Maybe
all I need to do is activate this somehow?
Cheers,
-John
On Wed, 23 Mar 2016 at 12:07 <rahulm...@gmail.com> wrote:
> Hi John,
>
> ghc-prim is just a stub package generated for the purpose of
> documentation. All primops are defined in a low level language called Cmm
> in GHC. If you want to make it even faster, you'll need to learn Cmm and
> update the definition in GHC. If you want to a specialized implementation
> for x86 systems, you may need to modify the NCG (Native Code Generator)
> which requires a knowledge of assembly language.
>
> Hope that helps!
> Rahul Muttineni
>
> Sent from my BlackBerry 10 smartphone.
> *From: *John Ky
> *Sent: *Wednesday 23 March 2016 4:40 AM
> *To: *The Haskell-Beginners Mailing List - Discussion of primarily
> beginner-level topics related to Haskell
> *Reply To: *The Haskell-Beginners Mailing List - Discussion of primarily
> beginner-level topics related to Haskell
> *Subject: *[Haskell-beginners] let x = x in x (GHC.Prim)
>
> Hello Haskellers,
>
> I'm trying to write a faster popCount function for x86 systems.
>
> I tried cloning the ghc-prim package and repurposing it for my own needs,
> but it isn't working as hoped.
>
> In particular, popCnt64# was implemented in GHC.Prim as:
>
> popCnt64# = let x = x in x
>
> Which shouldn't terminate. Yet when I call it, it magically finds the C
> implementation in hs_popcnt64 and returns the correct value.
>
> My cloned project doesn't behave that way. Instead it doesn't terminate
> as I would expect.
>
> Anyone know what's happening here, if there is a way to make this work or
> tell me if I'm going about this completely the wrong way?
>
> Cheers,
>
> -John
>
>
> _______________________________________________
> Beginners mailing list
> Beginners@haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
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