Re: FW: SDL-News: Timers


Subject: Re: FW: SDL-News: Timers
From: Andreas Metzger (metzger#informatik.uni-kl.de)
Date: Tue Mar 02 2004 - 09:49:29 GMT


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Hi everyone,

just a little remark concerning the proposed solution to the dynamic
setting of a timer from Anthony.

When generating any real-time code (e.g. Real-Time Simulation or
Application in Telelogic Tau SDL Suite), the proposed solution might
introduce a timer creep, i.e. the durations between the timer events
will get bigger than the desired 1.0. This is caused by the fact that
when the NOW-expression is evaluated, time has already expired (and also
because the timer-event does not necessarily occur at the specified
point in time, most probably a little later).

A more "robust" solution that will produce more precise durations is to
not use the NOW-expression for resetting the timer but rather remember
the recent time-out value, as in the attached example.

Greetings

~ Andreas Metzger

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Dipl.-Inform. Andreas Metzger
Department of Computer Science, University of Kaiserslautern, Germany

Website: http://wwwagz.informatik.uni-kl.de/staff/metzger
PGP Key: http://wwwagz.informatik.uni-kl.de/staff/metzger/pgp.txt
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