From: John Perry <john.perry@usm.edu>
Subject: Re: Performance of records with variant parts
Date: Tue, 23 Mar 2021 16:00:39 -0700 (PDT) [thread overview]
Message-ID: <b962cd83-c15a-4285-9754-48008e685c49n@googlegroups.com> (raw)
In-Reply-To: <s3ccgm$4j7$1@dont-email.me>
On Tuesday, March 23, 2021 at 4:31:05 AM UTC-5, Jeffrey R. Carter wrote:
> On 3/22/21 11:11 PM, John Perry wrote:
> Interesting. With that optimization I would not expect this to differ noticeably
> from a record without discriminants.
>
> I note that all your nested declarations could be declared constant.
>
> Use of Long_Float is completely non-portable.
Thank you for these tips.
> If you want to look into this further, IIRC, there is an option that will output
> a low-level, Ada-like description of the IR that the front end produces. You'll
> have to look in the top-secret GNAT documentation to find it.
Yep, that shows the problem. For the declaration that immediately follows "when Sphere =>" we get
| B_2 : declare
| [constraint_error when
| objects__thing_typeD2 (obj.kind)
| "discriminant check failed"]
| eo : vectors__vector := vectors__Osubtract (obj.center,
and that function translates as
| function objects__thing_typeD2 (kind : objects__object_type)
| return boolean is
| begin
| if kind = objects__sphere then
| return false;
| else
| return true;
| end if;
| end objects__thing_typeD2;
So I'm getting a completely useless warning.
It's even worse for "case Plane =>"; it checks the same thing twice!
| if denom <= 0.0 then
| [constraint_error when
| objects__thing_typeD3 (obj.kind)
| "discriminant check failed"]
| [constraint_error when
| objects__thing_typeD3 (obj.kind)
| "discriminant check failed"]
| return (vectors__vector_dot (obj.norm, ray.start) +
| obj.offset) / (-denom);
Am I right in thinking this is a bug? It shouldn't even check it, let alone check it twice.
regards
john perry
next prev parent reply other threads:[~2021-03-23 23:00 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 [this message]
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
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