Help on using DistValInt

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    I was trying to use DistValInt in my code but I keep getting one output value.

    I’ve decraled the variable inside the PROCESS as:

    variable rndx  : RandomPType;

    variable tmp_val : integer;

    then I’ve used it as:


    tmp_val := rndx.DistValInt(((1,1),(2,5),(3,3),(4,1)));

    I changed the value of SEED a couple of times (e.g. 1234, 555, 5567) but I was always getting 1 as result for tmp_val. Did I miss something in my equations?

    Thank you in advance for help and suggestions.

    Jim Lewis

    Hi Alvin,
    You need to show more code. I can’t tell how many times you call DistValInt. What I would expect to see is:

      variable rndx  : RandomPType;
      variable tmp_val : integer;
    rndx.InitSeed(SEED);  -- do one time.
      tmp_val := rndx.DistValInt(((1,1),(2,5),(3,3),(4,1)));
      -- do something
    end loop ;

    One key point is that the seed is a state variable and is only set one time at the beginning. A given seed will always produce the same sequence – this is important for test stability. WRT trying different seeds and always getting a 1 first – this is possible since you have a 25% chance of it happening. Although several generate the same initial value, it is likely that they will generate a different sequence.

    Have you looked at RandomPkg_user_guide.pdf?



    Hi Jim,

    I’ve tried something similar to your example code and now it produced the results that I was expecting. 

    counts := (0,0,0,0);
    for i in 0 to 100 loop
      tmp_val := rndx.DistValInt(((1,1),(2,5),(3,3),(4,1)));
      case (tmp_val) is
        when 1      => counts(0) := counts(0)+1; 
        when 2      => counts(1) := counts(1)+1; 
        when 3      => counts(2) := counts(2)+1; 
        when 4      => counts(3) := counts(3)+1; 
        when others => counts    := counts;
      end case;    
    end loop;

    report "counts: " & to_string(counts(0)) & ","
                      & to_string(counts(1)) & ","
                      & to_string(counts(2)) & ","
                      & to_string(counts(3));

    I got "Note: counts: 8,54,27,12" in my simulation run.

    Yesterday I did not execute the rndx.DistValInt() multiple times and I only tested a few SEED values to initialize my random variable and I think that was the reason why I did not observe the generation of tmp_val properly.

    Thanks a lot for your help,


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