RE: [sv-ec] interface classes and pre_randomize post_randomize

1. I believe that you are referring to this in the LRM:
The pre_randomize() and post_randomize() methods are not virtual. However, because they are
automatically called by the randomize() method, which is virtual, they appear to behave as virtual
methods.
Since randomize() is virtual, if you call randomize() on a parent class you will invoke randomize() of the child class which in turn will call pre_randomize() and post_randomize() of the child class, which means that pre_randomize() and post_randomize() act like they are virtual anyway. You could try to build an example where the virtual/non-virtual definition of pre_randomize() and post_randomize() would matter; but in order to do that you would have to call pre_randomize() and/or post_randomize() directly.

It was convenient to define the built-in pre_randomize() and post_randomize() methods of interface classes as being virtual.  This makes it possible to call pre_randomize() or post_randomize() directly on an interface class handle, which would not be possible if it were not defined to be built-into interface classes.  Also, calls to pre_randomize() or post_randomize on an interface class handle would explicitly do nothing if it were not defined to be virtual.  The implication of this is that if a class implements any interface class, then pre_randomize() and post_randomize() would be virtual methods in that class and all children of that class, where otherwise they merely act like virtual methods when you call randomize().

2) The code that you wrote below is illegal.  An interface class may only contain type declarations,  pure virtual method prototypes, paramters and local parameters.  The code in your example code contains method definitions.

-Brandon

From: owner-sv-ec@eda.org [mailto:owner-sv-ec@eda.org] On Behalf Of Daniel Mlynek
Sent: Tuesday, April 22, 2014 4:11 AM
To: sv-ec@eda.org
Cc: Piotr Rozkoszek
Subject: [sv-ec] interface classes and pre_randomize post_randomize

LRM says:
"Interface classes contain two built-in empty virtual methods pre_randomize()and post_randomize() that are automatically called before and after randomization. These methods can be overridden. As a special case, pre_randomize()and post_randomize()shall not cause method name conflicts."

1. Later on LRM says that pre/post randomize are not virtual so using virtual in above sentense seem to be an error (LRM: "The pre_randomize()and post_randomize()methods are not virtual.")

2. I assume that above quotation allows to define A and B like this:
interface class A;
    parameter p=0;
    function void pre_randomize();
        $display("A");
    endfunction
endclass

interface class B;
    parameter p=0;
    function void pre_randomize();
        $display("B");
    endfunction
endclass

But what should happened when class C implements both A and B  and randomize on C object is called via A,B or C handle?
class C implements A, implements B;
endclass
C c=new;
A a=c;
B b=c;
a.randomize; //A::pre_randomze is called?
b.randomize;//B::pre_randomze is called?
c.randomize;//A::pre_randomze and B::pre_randomze is called?

I cannot see where LRM defines this behaviour.



DANiel


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