Randomize Unique Elements

Generate Unique Random Values SystemVerilog

In SystemVerilog below is one of the method,

  • to generate unique values to set of variables or
  • unique elements to an array

This can be achieved using Unique constraint.

Unique constraint can be used to generate unique values across the variables, generate unique elements in an array (Fixed Size Array, Dynamic Array, Associative array and Queue) .

In below example the variables (var_1, var_2 and var_3) are constrained using keyword unique, On randomization which leads to generation of unique values to the variables.
Same way to an array (array), random unique elements can be generated by constraining array with unique keyword.

class unique_elements;
  rand bit [3:0] var_1,var_2,var_3;
  rand bit [7:0] array[6];
  constraint array_c {unique {array};}
  function void display();
    $display("var_1 = %p",var_1);
    $display("var_2 = %p",var_2);
    $display("var_3 = %p",var_3);
    $display("array = %p",array);

program unique_elements_randomization;
  unique_elements pkt;

  initial begin
    pkt = new();

Simulator Output

var_1 =  8
var_2 = 14
var_3 = 11
array = '{'h81, 'h7b, 'h4, 'h47, 'he1, 'h17}

Click to execute on