From: John Perry <john.perry@usm.edu>
Subject: Re: Performance of records with variant parts
Date: Mon, 22 Mar 2021 14:54:13 -0700 (PDT) [thread overview]
Message-ID: <b8037068-5da7-4c2a-ac74-7cc7790e11a3n@googlegroups.com> (raw)
In-Reply-To: <ibs7okF5i52U1@mid.individual.net>
On Monday, March 22, 2021 at 1:59:34 PM UTC-5, Niklas Holsti wrote:
> What is your optimization level? -O2?
I've tried several. The one with the best performance is -O3 -funroll-loops -gnatn.
> Moreover, in your case the compiler should
> statically know the offset of each discriminant-dependent component, so
> accessing such a component should not require any overhead compared to a
> record without discriminants.
Precisely this perplexes me. Nothing in this section of the code would be unknown after the discriminant check. -- Nothing that seems obvious to me, anyway. I'll copy some code in a reply to someone else in a moment.
> However, in the past I've seen unexpectedly slow code for copying
> records with discriminants. ...
> [very interesting material excised for brevity]
> If the compiler is stupidly checking the discriminant of obj for each
> obj-component access, you may be able to speed up the code by creating
> separate sub-procedures
I liked this idea and thought it might be the problem, but that also didn't help out. I may have to look at the assembly, which I am loath to do. :-/
john perry
prev parent reply other threads:[~2021-03-22 21:54 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-22 17:02 Performance of records with variant parts John Perry
2021-03-22 17:32 ` Jeffrey R. Carter
2021-03-22 17:49 ` John Perry
2021-03-22 17:54 ` John Perry
2021-03-22 19:31 ` Jeffrey R. Carter
2021-03-22 22:11 ` John Perry
2021-03-23 9:31 ` Jeffrey R. Carter
2021-03-23 14:27 ` Simon Wright
2021-03-23 23:00 ` John Perry
2021-03-23 23:27 ` Jeffrey R. Carter
2021-03-26 15:38 ` Stephen Leake
2021-03-26 15:44 ` John Perry
2021-03-30 7:12 ` Emmanuel Briot
2021-04-01 0:03 ` John Perry
2021-04-01 6:45 ` Emmanuel Briot
2021-04-01 13:38 ` Niklas Holsti
2021-04-02 16:07 ` John Perry
2021-03-22 17:39 ` Dmitry A. Kazakov
2021-03-22 17:45 ` John Perry
2021-03-22 18:07 ` Dmitry A. Kazakov
2021-03-22 18:23 ` John Perry
2021-03-22 20:30 ` Dmitry A. Kazakov
2021-03-22 18:59 ` Niklas Holsti
2021-03-22 21:54 ` John Perry [this message]
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