[Haskell-cafe] Re: speed: ghc vs gcc

Sebastian Sylvan sylvan at student.chalmers.se
Fri Feb 20 19:48:37 EST 2009

I was intending to send this privately but clicked the wrong button.
Apologies for adding even more noise to this discussion.

On Sat, Feb 21, 2009 at 12:47 AM, Sebastian Sylvan <
sylvan at student.chalmers.se> wrote:

> On Sat, Feb 21, 2009 at 12:16 AM, Bulat Ziganshin <
> bulat.ziganshin at gmail.com> wrote:
>> Hello Sebastian,
>> Saturday, February 21, 2009, 2:42:33 AM, you wrote:
>> > Bulat, please, you're missing the point.
>> actually you are missing the point. i mirror Don's
>> "non-attacking" style of comments on my person. are you mentioned
>> those Don letter? sure - no
>> > Nobody is saying that the
>> > template-haskell trick was somehow a viable general strategy right
>> > now that everyone should use by default. It was used as a
>> > proof-of-concept that a simple technique can lead to massive
>> > performance improvements - and we get numbers for how massive it
>> > would be (beating gcc for this benchmark).
>> sorry, but you was fooled too. the situation was the following: i
>> wrote non-optimal code for 64-bit platforms (using 32-bit int) and Don
>> don't corrected it. then he compiled TH-generated code via *gcc* that
>> used "fusion" technique - the same that was used by 32-bit C++ code
>> are you wondered why -D64 version is 8 times faster than -D8 one? it's
>> exactly because *gcc* reduced 64 additions to just one operation. so
>> this "fair" comparison used TH+gcc to generate faster code than gcc
>> with improper data type definitions. if Don will fix C++ program, he
>> will find that it's speed reduced in the same proportion - without TH
>> tricks
>> >
>> > This isn't about "faking" a benchmark, it's about investigating the
>> > reasons for why the benchmark looks they way it does, doing testing
>> > to verify the assumptions (in this case using TH), and making
>> > constructive suggestions (add loop-unrolling to the compiler). This
>> > investigation tells us that in this case a compiler could beat gcc,
>> > if only it were to do loop unrolling in the way the TH code does. That's
>> a result!
>> yes, in the cases when *gcc* "fuse" loops and you don't allow it do it
>> for C++ code but allows for Haskell - you will win
>> > I would ask you to note the simple fact that every single
>> > constructive message in this thread has come from people other than
>> > you.
>> you are ignore, though, the fact that every destructive message in
>> this thread comes against me. it seems that it's a crime here to write
>> about ghc speed anything but praise. in best case people will said
>> that these tests are destructive :lol:
>> > I hope this leads you reconsider your tone and general approach
>> > in the future. Haskell people in general are always pretty good at
>> > accepting criticism IME (they tend to want to fix the problem),
>> that criticism??? cows can't fly, and ghc cannot beat gcc in 2
>> months. that bothers me is people that attack me just for comparing
>> compilers head-to-head
> I'm not going to debate all these points with you because I don't think you
> actually responded to mine, but let me just say that MY impression of this
> thread is that people attack you not because you compare compilers
> head-to-head, but because you do it in an incredibly abrasive and hostile
> manner (your messages read much more like "Haha! I told you so, look how
> stupid/dishonest you are!", than "Here's a case where GHC produces bad code,
> here's some analysis, and here's a ticket/patch for it").
> Just because you put a smiley at the end of a thinly veiled ad hominem
> doesn't mean you get to pretend that you're  just a victim when people get
> understandably ticked off at your tone and respond in kind.
> Search the archives, performance discussions come up all the time, often
> with quite vigorous criticism of GHC's current results, but somehow those
> threads manage to stay civil and on point. Please, do a little introspection
> and see if you can stick to a more constructive and friendly tone in the
> future - I would be willing to bet that if you did, you wouldn't get
> "attacked".
> --
> Sebastian Sylvan
> +44(0)7857-300802
> UIN: 44640862

Sebastian Sylvan
UIN: 44640862
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