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amar712

Unique array elements without rand or randc

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I have a variable logic [31:0] id which is not declared as rand or randc. I need different id's each time into an array logic [31:0] id_array [16].

logic [31:0] id;
logic [31:0] id_array [16];
foreach(id_array) begin
std::randomize(id);
id_array = id;
end

In the above code, there is a possibility of getting duplicate ids in the array. How do I change the code to get unique ids in the array ?

 

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Write a constraint for that. The idea is, for each element in the array, you iterate through all the elements of the array. If the index don't match, the make sure the values are not equal.

This is O(n^2) complexity, there could be a better way of accomplishing the same as well.  

constraint c_unique_array_value {

  foreach(id_array) { 

      foreach(id_array[j]) {

          if(i != j) id_array != id_array[j];

      }

  }

}

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I think UNIQUE KEYWORD does well , I have used it with Synopsys VCS, a quick example ::-> http://www.edaplayground.com/x/6AHE

 

Not sure about cadence incisive, sometime back raised CCR for enhancement for this feature , not sure whether it is available.

 

But yes, this unique keyword does much beautification to my code. ;)

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