Re: [sv-ac] New version of 3213 uploaded

Hi Dmitry,

I read through the proposal for 3213, and I really don't think this is
the way we want to go. This proposal resurrects the sampling semantics
that we rejected at the face-to-face, but calls them concurrent
semantics rather than sampled semantics.

I especially don't like the fact that the $sampled function is
completely deleted from the standard. The changes to 20.13 delete the
$sampled function from the BNF. This would be a huge backward
compatibility headache for us. This would require that we touch every
single assert file we have ever written.

The current definition of sampling works for just about everything.
    - Design variables are sampled.
    - Checker variables (non-random) don't really need to be sampled,
      because they change after the Observed region, but sampling them
      doesn't hurt.
      Simulators could do optimization internally to skip the sampling
      of these variables if that helped performance.

The only thing that doesn't work are random checker variables, because
they are assigned in Observed, and used in Observed.

I am OK with defining a $concurrent function, for the special cases
where it might be needed, but I don't want to re-write the whole LRM to
remove all references to sampling. Also it seems like you are asking
the compiler writers for magic, if you expect to pass an expression and
have the function use the sampled value of the first variable in that
expression, the current value of the second variable, and the sampled
value of the third.

Keep in mind that most assertions are written for simulation. These
assertions will probably not use any random checker variables. Any
changes we make will need to be transparent to these users.

Tom

On 04/12/11 02:19, Korchemny, Dmitry wrote:
> Hi all,
>
>
>
> I uploaded a new version of 3213 incorporating the reviewers’ comments:
> http://www.eda-stds.org/mantis/file_download.php?file_id=4909&type=bug
> <http://www.eda-stds.org/mantis/file_download.php?file_id=4909&type=bug>.
>
>
>
> Thanks,
>
> Dmitry
>
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