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[Bug fortran/34533] DTIME returns total process time and not since last invocation
- From: "sgk at troutmask dot apl dot washington dot edu" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 20 Dec 2007 22:27:58 -0000
- Subject: [Bug fortran/34533] DTIME returns total process time and not since last invocation
- References: <bug-34533-13404@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #9 from sgk at troutmask dot apl dot washington dot edu 2007-12-20 22:27 -------
Subject: Re: DTIME returns total process time and not since last invocation
On Thu, Dec 20, 2007 at 09:39:29PM -0000, dfranke at gcc dot gnu dot org wrote:
>
> > Daniel, are you working on this PR?
>
> Sort of. Finished the library part.
>
> Btw, CPU_TIME has a fallback implementation using times(2). As "times()
> returns the number of clock ticks that have elapsed since an arbitrary
> point in the past", it is IMO unsuitable to be used with CPU_TIME.
> CPU_TIME is supposed to return a "value representing the elapsed CPU
> time in seconds [since start of the program]". Thus, I ditched this
> fallback for the common implementation.
>
Actually, you don't need to remove the fallback because Niote 13.8
in the F95 standard makes it clear that the initialize time does not
need to be referenced to zero.
>From Note 13.8:
The start time is left imprecise because the purpose is to time
sections of code, as in the example.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34533