RE: [sv-ec] A question about mixing rand and non-rand handles to the same object

OK, Thanks
Should there be a new mantis issue for this?
Bill 

-----Original Message-----
From: Ryan, Ray [mailto:Ray_Ryan@mentor.com] 
Sent: Friday, September 29, 2006 6:45 PM
To: Ryan, Ray; William Paulsen; sv-ec@eda-stds.org
Subject: RE: [sv-ec] A question about mixing rand and non-rand handles
to the same object

A had a couple people point out that I missed that
ch2.ch1 and ch2.rch1 both refer the same class instance.

In this case, since the variable (refered to by either "ch2.rch1.rint1"
or "ch2.ch1.rint1") is included in the set of active random variables it
should be treated as such (and not treated as a reference to a state
variable).

This is an important part of constraint composition with classes.
Possibly we need to add something like:

If an object is include in the set of active random variables, then in a
constraint any variable reference that resolves to that object
constrains the generated random value for the object.


That is, the final set of random variables and constraints looks like:
    Random variables:
 	<randVar1>   "ch2.rint2"
 	<randVar2>   "ch2.rch1.rint1"
    Constraints:
 	ch2.rch1.con1 { <randVar2> == 10; }
 	ch2.con2 {<randVar2> == <randVar1>;}

So there is only 1 solution. IE. both random variables must be 10.

Ray

> -----Original Message-----
> From: owner-sv-ec@server.eda.org
> [mailto:owner-sv-ec@server.eda.org] On Behalf Of Ryan, Ray
> Sent: Friday, September 29, 2006 2:34 PM
> To: William Paulsen; sv-ec@server.eda-stds.org
> Subject: RE: [sv-ec] A question about mixing rand and non-rand handles

> to the same object
> 
>  When ch2.randomize() is called, the set of random objects and 
> constraints initially consists of all the random members and 
> constraints of ch2. These are:
>    Random variables:
>   	ch2.rint2
> 	ch2.rch1
>    Constraints:
> 	ch2.con2 {ch2.rint2 == ch2.ch1.rint1;}
> 
> Because ch2.rch1 is random and is a class handle, its random members 
> and constraints are added to the randomization.
> So the random variable and constraints become:
>    Random variables:
> 	ch2.rint2
> 	ch2.rch1.rint1
>    Constraints:
> 	ch2.rch1.con1 { ch2.rch1.rint1 == 10; }
> 	ch2.con2 {ch2.rint2 == ch2.ch1.rint1;)
> 
> A reference to a variable in a constaint does not make it 'rand'. So 
> yes, for this randomization, ch2.ch1.rint1 is a state value.
> 
> Ray
> 
> > -----Original Message-----
> > From: owner-sv-ec@server.eda.org
> > [mailto:owner-sv-ec@server.eda.org] On Behalf Of William Paulsen
> > Sent: Friday, September 29, 2006 1:29 PM
> > To: sv-ec@server.eda-stds.org
> > Subject: [sv-ec] A question about mixing rand and non-rand
> handles to
> > the same object
> > 
> > 
> > Section 13.4.8 of the LRM is not clear (to me) about the following 
> > scenario.
> > Does there need to be an explanation or clarification added
> to the LRM
> > for this?
> > 
> > Thanks,
> > Bill
> > 
> > 
> > In the example below, two constraint expressions contain
> references to
> > the same property (rint1) of the same class
> > (class1) object instance.
> > 
> >   In class2, constraint "con2" has the reference "ch1.rint1", where 
> > "ch1"
> >   is not a rand handle.
> > 
> >   In class1, constraint "con1" has the reference "rint1", where 
> > "rint1"
> > is rand.
> > 
> > Is "ch1.rint1" in constraint "con2" considered a state
> variable, or is
> > it one of the "active random objects?"
> > 
> > One possibility is that in constraint "con2", "rint1" is a state 
> > variable, whose value is not subject to generation, since
> "ch1" is not
> > rand.
> > 
> > The other possibility is that since "ch2.ch1.rint1" is the same 
> > property as "ch2.rch1.rint1", then it should be considered
> rand even
> > in the context of constraint "con2".
> > 
> > module top;
> > 
> > class class1;
> >   rand int rint1;
> >   constraint con1 { rint1 == 10;}
> > endclass
> > 
> > class class2;
> >   rand int rint2;
> >   class1 ch1;
> >   rand class1 rch1;
> >   constraint con2 { rint2 == ch1.rint1; } // What value is
> > rint2 set to?
> > endclass
> > 
> > class2 ch2 = new;
> > int res;
> > 
> > initial begin
> >   ch2.ch1 = new;
> >   ch2.rch1 = ch2.ch1;  // The same object
> > 
> >   ch2.ch1.rint1 = 20;
> > 
> >   res = ch2.randomize();
> > 
> >   if (ch2.rint2 == 20) $display("ch2.ch1 is considered non-rand");
> >   if (ch2.rint2 == 10) $display("ch2.ch1 is considered rand"); end 
> > endmodule
> > 
> > 
> > 
> 
>