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Message from discussion Global array operations: a performance hit?
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Dennis Wassel  
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 More options Jun 18 2008, 9:47 am
Newsgroups: comp.lang.fortran
From: Dennis Wassel <dennis.was...@googlemail.com>
Date: Wed, 18 Jun 2008 06:47:36 -0700 (PDT)
Local: Wed, Jun 18 2008 9:47 am
Subject: Re: Global array operations: a performance hit?
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On 18 Jun., 14:18, deltaquattro <deltaquat...@gmail.com> wrote:

> On 18 Giu, 11:41, Dennis Wassel <dennis.was...@googlemail.com> wrote:

> I'm not flaming and I don't think you are a novice: on the contrary,
> since you talked about the possibility of you being involved in gcc
> development, I think you know Fortran way better than me.
> Anyway, I would never say "STFU n00b" to anyone under any
> circumstances, if I understand what that means (I'm not sure since
> because English is not my mother tongue, and I don't live in an
> English speaking country).
> The point is that when I posted a genuine doubt about speed of whole
> array operations, you replied asking me if I have been clever enough
> in doing my timings. When Richard confirmed my doubts, you were ready
> to accept his words. To me, it seemed as if you were dismissing my
> doubts just because I'm not an expert as Richard, robin, glenn, Paul,
> Steve and all the many other guys on this newsgroup.

*sigh* I'm afraid it sounded exactly like that.

Sorry if I sounded as if I just dismissed your doubts as pointless, I
am in no position to do that; I wanted to point out that proper timing
is nontrivial, and whether you're aware of that. Apparently you are!
With Richard, his post (and google, I admit!) gives me some idea about
his background, so I'll tend to trust in what this guy says.

Besides, the fact that array operations may indeed be slower than
explicit loops was (and still is) hard for me to believe. Learned
something today!

> If this isn't so, then I apologize to you and to the rest of the
> newsgroup: I have misinterpreted your words, maybe also because of my
> imperfect knowledge of English.

> Best Regards,

> deltaquattro

No offence meant, and none taken (I hope)!

BTT:
Is (compiler) optimisation of array operations that much of a
nontrivial task or just something that nobody has come around to
doing, yet? Judging from their mailing list, gfortran seems to have
many construction sites and a number of them apparently with higher
priorities.

But deltaquattro reported this against Compaq, and I also remember
someone from the gfortran mailing list mentioning that ifort shines on
DO-loop optimisation. Alas, I really feel like digging into this, but
got to get my current project done first.

Cheers,
Dennis


 
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