RE: [sv-ac] sequence as clocking event to covergroup

Hi John,

I agree with you that the covergroup should trigger on multiple matches
of a seuqnce, but I think that with first_match it should give only one
match even if there are possible multiple matches (by choosing
non-deterministically one of them). 

Regards,
ed


> -----Original Message-----
> From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On 
> Behalf Of John Havlicek
> Sent: Monday, January 08, 2007 9:31 AM
> To: tej_singh@mentor.com
> Cc: sv-ac@eda.org
> Subject: Re: [sv-ac] sequence as clocking event to covergroup
> 
> Hi Tej:
> 
> I have a few comments.
> 
> It is true that the LRM does not give a complete definition of
> multiplicity of matching and of when matching occurs.  On the other
> hand, the LRM also does not leave these things completely undefined.
> 
> I think that if a covergroup has a sequence instance as its clocking
> event, then multiple matches of the sequence instance in the same
> timestep should result in multiple triggerings of the covergroup.
> 
> I think we should avoid allowing the rules for multiplicity 
> of covergroup
> triggering on sequences to differ from the rules for multiplicity of
> matching that apply in other scenarios, e.g.
> 
>    cover property (
>       @(posedge clk)
>       sequence_instance ##0 (1, task_call);
>    );
> 
> I don't like the idea of trying to incorporate first_match into the
> semantics of covergroups with sequence clocking event.  I think the 
> user can use first_match in defining a sequence, but then the general
> rules for multiplicity of sequence matching should apply.
> 
> In particular, a first_match can have multiplicity, e.g. if both
> a ##1 b and c ##1 d match over a two-cycle interval, then 
> 
>    first_match((a ##1 b) or (c ##1 d))
> 
> should match with multiplicity two over that interval.
> 
> Best regards,
> 
> John H.
> 
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> > From: "Singh, Tej" <tej_singh@mentor.com>
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> > But as Doron pointed out, the LRM does not define the 
> number of threads.
> > 
> > How about defining it so that the number of events at a 
> clock is same as
> > number of sequence attempts that matched at that clock. 
> This is what I =
> > was trying
> > to do with first_match but first_match will kill any future matches.
> > 
> > So for a sequence expr that looks like
> > 
> > a ##[1:$](b ##1 c) or (d ##1 e)
> > 
> > it will not matter whether 'or' results in two matches or 
> one match =
> > since
> > both correspond to the same attempt.=20
> > 
> > Tej
> > 
> > 
> 
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