Probabilities of a number while using a dist operator

SystemVerilog
, ,
1

I am trying to understand the difference between := and :/

class packet 
  rand bit[7:0] b;
  rand bit[7:0] a;

    constraint adist {a dist {0:=9, [1:255]:=1};}
    constraint bdist {b dist {0:/9, [1:255]:/1};}
endclass

What would be the probability of a being 0 and b being 0?
Is the probability of a being 0 = 9/264 and b being 0 = 9/10 ?

2

In reply to sfenil1804:

The difference is whether the weight gets applied to each value in the range (:=), or divided by the number of elements in the range(/:).

You answered your own question.

3

In reply to dave_59:


  rand bit [1:0] ab;
 
  constraint c1 { ab dist {0:= 25, 1:= 75}; }
  constraint c2 { ab dist {0:= 50, 1:= 2}; }

Since Values are overlapping ab would still be either 0 OR 1 .
How would the weight be allocated ? Would weights be average ?

4

In reply to TC_2017:

This is not defined in the LRM. See issue 0003758