Re: Duration vs. Ada.Real_Time

[Robert Dewar <robert_dewar@my-deja.com>]

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In article <3A71814B.7E8CCF60@acm.org>,
  Marin David Condic <mcondic.auntie.spam@acm.org> wrote:
> So if you are concerned about portability, you'd use Duration
> only in applications where 20mSec of accuracy is sufficient.

This may be confusing, the question was not about precision
of Duration, it was about resolution of the timer

The value of Duration'Small is only an upper bound for
resolution, there is nothing in the RM that forbids an
implementation where clock only updates every second (and
indeed do not be surprised if some Unix implementations
are like this).


For portability, your use
> of Real_Time should never assume accuracy greater that
20uSec. If you don't
> need portability, then you can rely on whatever the
implementation gives you
> for Duration'Small etc.
>
> MDC
>
> Atle R�stad wrote:
>
> > Hi
> >
> > I have some code that has a max of 30 milliseconds to
process, and need to
> > measure if this is possible. But the requirement for
Duration is that
> > Duration'Small must be less then 20 milliseconds, and
> > Ada.Real_Time.Time_Unit must be less then 20 microseconds.
> >
> > I figured that using Duration could give imprecise result.
So I wrote a
> > small program to print out Duration'Small.
> >
> > I'm using gnat 3.12 and printed out both Duration'Small and
> > Real_Time.Time_Unit and they were both 1.0E-09. I thought
Duration'Small
> > would be larger then Real_Time.Time_Unit but they were the
same.
> >
> > Why should I use Real_Time when duration has the same
resolution?
> >
> > I will run the program on an Solaris 8. How will this
affect my time
> > measuring? What resolution can I expect?
> >
> > Thanks,
> > Atle
>
> --
>
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> Marin David Condic - Quadrus Corporation -
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>
>     "I'd trade it all for just a little more"
>         --  Charles Montgomery Burns, [4F10]
>
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