RE: [sv-ec] Vector bin in a cross cover point

This is going back over two years, but I was looking over some old mail.

Looking at this again, I still don't see that it can't be done.

According to my understanding of the LRM, if you would write

A: coverpoint a_var { bins yy[] = { [0:9] }; }  //creates 10 bins yy[0] - yy[9]
B: coverpoint b_var { bins bb[] = { [0:5] }; }  //creates 6 bins bb[0] - bb[5]  (I need only first 6 values of b_var to be present the cross)
CC: cross A,B;

you would in fact get those 60 bins.

Regards,
Shalom

> -----Original Message-----
> From: Raghavender Reddy Paltammagari [mailto:reddyrag@cadence.com]
> Sent: Monday, February 14, 2011 16:36
> To: Bresticker, Shalom; SV_EC List
> Subject: RE: [sv-ec] Vector bin in a cross cover point
> 
> Hi Shalom,
> 
>    I agree that if you don't specify any user-defined bins in the cross
> coverage then it will create one bin for each and every combination.
> 
> But how can I specify user-defined bins in cross such that one bin is
> created for each and every combination?
> 
> Also, if I don't need all combinations of b_var to be crossed with
> coverpoint labeled as A, I can modify your example as below:
> 
> bit [31:0] a_var;
> bit [3:0] b_var;
> 
> covergroup cov3 @(posedge clk);
>   A: coverpoint a_var { bins yy[] = { [0:9] }; }  //creates 10 bins
> yy[0] - yy[9]
>   B: coverpoint b_var { bins bb[] = { [0:5] }; }  //creates 6 bins
> bb[0] - bb[5]  (I need only first 6 values of b_var to be present the
> cross)
>   CC: cross b_var, A  { bins bbyy = binsof(A.yy) && binsof(B.bb);
> //creates single bin for 60 combinations
> endgroup
> 
> The cross here generates a single bin for bbyy and will be shown as hit
> if atleast one of the 60 (10x6) combinations is hit.
> 
> How do I create separate bins for each of these 60 combinations?
> 
> If I can declare bbyy as a dynamic array then we can have separate bins
> created for the 60 combinations.
> 
> Pls let me know if something is not clear.
> 
> Thanks,
> Raghu.
> 
> -----Original Message-----
> From: Bresticker, Shalom [mailto:shalom.bresticker@intel.com]
> Sent: Monday, February 14, 2011 11:26 AM
> To: Raghavender Reddy Paltammagari; SV_EC List
> Subject: RE: [sv-ec] Vector bin in a cross cover point
> 
> Hi,
> 
> I am not sure this is correct.
> 
> In 19.6, you have, for example:
> 
> "bit [3:0] a, b;
> 
> covergroup cov @(posedge clk);
>   aXb : cross a, b;
> endgroup
> 
> The coverage group cov in the example above specifies the cross
> coverage of two 4-bit variables, a and b.
> SystemVerilog implicitly creates a coverage point for each variable.
> Each coverage point has 16 bins, namely auto[0]...auto[15].
> The cross of a and b (labeled aXb), therefore, has 256 cross products,
> and *EACH CROSS PRODUCT IS A BIN OF AXB*."
> 
> Similarly afterwards,
> 
> bit [31:0] a_var;
> bit [3:0] b_var;
> 
> covergroup cov3 @(posedge clk);
>   A: coverpoint a_var { bins yy[] = { [0:9] }; }
>   CC: cross b_var, A;
> endgroup
> 
> The coverage group cov3 crosses variable b_var with coverage point A
> (labeled CC). Variable b_var automatically creates 16 bins
> (auto[0]...auto[15]). Coverage point A explicitly creates 10 bins
> (yy[0]...yy[9]).
> 
> THE CROSS OF TWO COVERAGE POINTS CREATES 16 × 10 = 160 CROSS PRODUCT
> BINS, NAMELY THE FOLLOWING PAIRS:
> 
> <auto[0], yy[0]>
> <auto[0], yy[1]>
> ...
> <auto[0], yy[9]>
> <auto[1], yy[0]>
> ...
> <auto[15], yy[9]>"
> 
> So it does seem that every combination creates a separate bin by
> default.
> What is not clear is how these bins are named and how they can be
> accessed.
> This was discussed recently.
> 
> Regards,
> Shalom
> 
> 
> > -----Original Message-----
> > From: Raghavender Reddy Paltammagari [mailto:reddyrag@cadence.com]
> > Sent: Sunday, February 13, 2011 8:56 PM
> > To: Bresticker, Shalom; neil.korpusik@oracle.com; SV_EC List
> > Cc: Raghavender Reddy Paltammagari
> > Subject: RE: [sv-ec] Vector bin in a cross cover point
> >
> > Hi Shalom,
> >
> >    Let's consider below example:
> >
> > class c3;
> >     rand bit [1:0] one;
> >     rand bit [3:0] two;
> >
> >     covergroup cg;
> >       cp1: coverpoint one {
> > 		bins A[] = {[0:3]};
> > 		    }
> >
> >       cp2: coverpoint two{
> > 		bins low[]  = {[0:5]};
> > 		bins mid[]  = {[6:10]};
> > 		bins high[] = {[11:15]};
> >                    }
> >
> >       onetwo: cross cp1, cp2 {
> >             bins x2 = binsof(cp1) && binsof(cp2.mid);
> > 	}
> >       endgroup:cg
> >
> >     function new();
> >       cg = new();
> >       //cg.set_inst_name("akhil");
> >     endfunction
> > enclass
> >
> > In this example, 	the number of bins created for coverpoint one is 4
> > (A[0], A[1], A[2] and A[3])
> >
> > - The number of bins created for cross coverpoint cp1, cp2(labeled as
> > onetwo) is 1.
> >
> > - The number of possible values for the cross "binsof(cp1) &&
> > binsof(cp2.mid)" is 20 (4 for cp1 multiplied with 5 for cp2.mid)
> >
> > - A single bin is created for all these 20 values. If atleast one of
> > these 20 values is hit then this covergroup will be shown as hit.
> >
> > - I want to see different bins for each of these 20 values.
> >
> > - If I can use a vector bin in a cross i.e. a dynamic array when
> > specifying bins construct in a cross coverpoint then I can create 20
> > different bins for these 20 values.
> >
> > - Unfortunately vector bin (or) a dynamic array in bins construct is
> > not specified in IEEE Std 1800-2009 Page: 498, Syntax 19-4.
> >
> > - As a result tools doesn't support this and I can't use a dynamic
> > array when specifying bins x2 as below:
> > onetwo: cross cp1, cp2 {
> >             bins x2[] = binsof(cp1) && binsof(cp2.mid);    //note the
> > dynamic array for x2 (We can't use this as of today)
> > 	}
> >
> > Note the usage of dynamic array in bins construct for normal
> coverpoint
> > cp1. Syntax 19-2 for normal coverpoint allows this.
> >
> >
> > Here is the difference between two syntaxes:
> > Syntax 19-4 for cross coverpoints:-
> > bins_selection ::= bins_keyword bin_identifier = select_expression [
> > iff ( expression ) ]  //note there is no dynamic array after the
> > bin_identifier
> >
> > Syntax 19-2 for normal coverpoints:-
> > bins_or_options ::=
> > coverage_option
> > | [ wildcard ] bins_keyword bin_identifier [ [ [ expression ] ] ] = {
> > open_range_list } [ iff ( expression) ]  //note the dynamic array
> after
> > bin_identifier
> >
> > Pls let me know if something is not clear.
> >
> >
> > Thanks,
> > Raghu.
> 
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