public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "anlauf at gmx dot de" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug fortran/64432] [5 Regression] SYSTEM_CLOCK(COUNT_RATE=rate) wrong result for integer(4)::rate Date: Mon, 29 Dec 2014 15:04:00 -0000 [thread overview] Message-ID: <bug-64432-4-AdiHieHC1w@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-64432-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64432 --- Comment #5 from Harald Anlauf <anlauf at gmx dot de> --- (In reply to Francois-Xavier Coudert from comment #4) > I'm not sure this is a bug, but this was definitely by design (as the > comment indicates). I think this is allowed by the successive standards > (which are, in any case, very weakly worded). Well, let's see: the standard says: COUNT RATE (optional) shall be an integer or real scalar. It is an INTENT (OUT) argument. It is assigned a processor-dependent approximation to the number of processor clock counts per second, or zero if there is no clock. You're right, it does not say anything about consistency. Nevertheless, I would prefer if a program that always uses e.g. default integer == integer(4), the low-resolution (msec) version continues to be used consistently. That's what other compilers do and what gfortran <= 4.9 did. Also, the presence of a second argument (see comment #1) should not change the behavior. OTOH, it is the responsibility of a user to consistently use arguments of the same type and kind to get consistent behavior. (I.e. not mixing integer and real or integer(4) and integer(8)). I do take care of that. > The root of the problem is that we want to allow for SYSTEM_CLOCK to return > high-precision values for large integer kinds, and fall back to > lower-precision results that fit in fewer bytes for smaller integer kinds. How is this fallback done? Do you truncate the resolution? E.g. high res. -> low res.: divide count_rate and count by 1000? > Thus, one should call SYSTEM_CLOCK once with all the necessary arguments, > and not multiple times with varying argument types. Note that I did *not* call SYSTEM_CLOCK with varying argument types. You're probably not aware of existing (f95) code that deals with the problem of wrapping, which is always present (count does not necessarily start with 0 at start of the program), although not very likely with integer(8)... ;-) > The only other consistent option I can see would be to simply go for > high-resolution results in all cases, but that would mean that SYSTEM_CLOCK > with 32-bit integers would wrap around in less than an hour. No, that doesn't make sense. > If you have another idea, please post a list of what you think should happen > in all various cases (all possible combinations of arguments have to be > allowed). Let's see: - For any number of arguments present (1, 2 or 3) - always integer(4): msec resolution (as before) - always integer(>=8): usec resolution (or whatever is possible) - always real: I don't care, but I think it might be a good idea to use the same as for integer of a compatible kind. - different types and/or kinds: I don't care, since one should expect problems (wrapping or truncation) anyway. But presence of non-presence should never make a difference if consistent types and kinds are used.
next prev parent reply other threads:[~2014-12-29 15:04 UTC|newest] Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-12-29 10:44 [Bug fortran/64432] New: " anlauf at gmx dot de 2014-12-29 11:14 ` [Bug fortran/64432] " anlauf at gmx dot de 2014-12-29 11:18 ` anlauf at gmx dot de 2014-12-29 11:20 ` janus at gcc dot gnu.org 2014-12-29 11:21 ` janus at gcc dot gnu.org 2014-12-29 14:13 ` fxcoudert at gcc dot gnu.org 2014-12-29 15:04 ` anlauf at gmx dot de [this message] 2014-12-29 15:23 ` anlauf at gmx dot de 2014-12-30 9:48 ` Joost.VandeVondele at mat dot ethz.ch 2014-12-30 10:05 ` Joost.VandeVondele at mat dot ethz.ch 2015-01-04 21:47 ` anlauf at gmx dot de 2015-01-04 21:56 ` anlauf at gmx dot de 2015-01-04 22:04 ` fxcoudert at gcc dot gnu.org 2015-01-04 22:53 ` anlauf at gmx dot de 2015-01-09 11:20 ` rguenth at gcc dot gnu.org 2015-01-09 14:12 ` jakub at gcc dot gnu.org 2015-01-19 20:49 ` anlauf at gmx dot de 2015-02-11 21:20 ` jvdelisle at gcc dot gnu.org 2015-02-13 22:31 ` anlauf at gmx dot de 2015-02-15 4:59 ` jvdelisle at gcc dot gnu.org 2015-02-16 3:14 ` jvdelisle at gcc dot gnu.org 2015-02-16 12:04 ` anlauf at gmx dot de 2015-02-16 20:04 ` jvdelisle at gcc dot gnu.org 2015-02-18 4:21 ` jvdelisle at gcc dot gnu.org 2015-02-18 20:04 ` anlauf at gmx dot de 2015-02-18 20:12 ` anlauf at gmx dot de 2015-02-19 16:32 ` jvdelisle at gcc dot gnu.org 2015-02-20 17:11 ` jvdelisle at gcc dot gnu.org 2015-02-20 22:14 ` anlauf at gmx dot de 2015-02-22 12:06 ` dominiq at lps dot ens.fr 2015-02-22 12:56 ` dominiq at lps dot ens.fr 2015-02-22 17:11 ` jvdelisle at gcc dot gnu.org 2015-02-26 17:44 ` jvdelisle at gcc dot gnu.org 2015-03-15 21:29 ` anlauf at gmx dot de 2015-03-17 1:02 ` jvdelisle at gcc dot gnu.org 2015-03-17 1:05 ` jvdelisle at gcc dot gnu.org 2015-03-17 1:22 ` jvdelisle at gcc dot gnu.org 2015-03-17 21:16 ` anlauf at gmx dot de 2015-03-17 22:33 ` jvdelisle at gcc dot gnu.org 2015-03-18 1:47 ` jvdelisle at gcc dot gnu.org 2015-03-20 7:38 ` jvdelisle at gcc dot gnu.org
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=bug-64432-4-AdiHieHC1w@http.gcc.gnu.org/bugzilla/ \ --to=gcc-bugzilla@gcc.gnu.org \ --cc=gcc-bugs@gcc.gnu.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).