Re: [sv-ec] Covergroup fixed-size vector bin creation

Hi Scott,

This topic was discussed in the January 23, 2006 conference call.
Mantis 1237 added text to section 19.5.4 of the LRM (back then it was
section 18.4.4).

During the conference call it was pointed out that doing the distribution
first, tends to be easier for humans to comprehend. It was also mentioned
that "ignore_bins specifies values to ignore (not bins to ignore)" and "If
ignoring creates a bin with no values it is ignored for coverage".

Neil

On 03/15/11 06:02, Little Scott-B11206 wrote:
> Hi all:
>
> In the meeting yesterday we discussed the order in which the bin distribution and with
expression application should be done when creating fixed-size vector bins. Below is an
example of where this would matter.
>
> bit [3:0] coverpoint b {
> bins onehot[4] = b with $onehot(item);
> }
>
> If we apply the with function and then distribute to the bins we get what is probably the
intended result of one item/bin. If we distribute then apply the with function we end up
with three bins, <0001,0010>,<0100>,<1000>. The fourth bin is emptied by the application
of the with expression and is excluded from coverage.
>
> In the meeting, I had stated that I thought the application of the with expression should
apply after the distribution of bins. This would be in line with how ignore bins are
handled (see 19.5.4). Based on the above example it seems like that is the wrong thing to
do. Do folks recall how the decision was made regarding ordering between applying ignore
bins and distribution? Is there another example that shows why distribution before
application of the with expression is desirable?
>
> Thanks,
> Scott
>
>

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