Constraint #26

write a constraint to generate a unique no. ,and the size of the array is 10

"Formulate a constraint to generate a unique set of numbers within an array of size 10. To address this constraint, let's break it down into two key elements:

1. The array should be of fixed size, specifically 10 elements.This can be achieved by either using a fixed-size array directly with a size of 10, or by creating a dynamic array and constraining its size to be 10.
2. All elements within the array must be unique.This uniqueness condition can be satisfied by using the 'unique' keyword or implementing two foreach loops to ensure the generation of distinct values for the array.

class sample;
  rand bit [3:0] array1[];

  constraint array_c {
    array1.size() == 10;
    unique { array1 };
  }
endclass

module top;
  sample s = new();

  initial begin
    repeat (5) begin
      assert(s.randomize());
      $display("s=%p", s);
    end
  end
endmodule        

This code ensures that the array 'array1' has a fixed size of 10 and that all its elements are unique. The 'unique' keyword enforces the uniqueness constraint, providing a systematic way to generate distinct values within the array."

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Program Decoding

This SystemVerilog program defines a class sample and a top-level module top. The class sample has a random array named array1 of 4-bit elements. The constraints within the class ensure that the size of array1 is fixed at 10, and all elements in the array are unique.

The top module creates an instance s of the sample class and attempts to randomize it in a loop executed five times. After each randomization attempt, the program displays the values of the s object using the $display statement.

Let's break down the key elements:

1. Class Definition (sample):rand bit [3:0] array1[];: Declares a random array named array1 consisting of 4-bit elements.constraint array_c { array1.size() == 10; unique { array1 }; }: Defines a constraint named array_c within the class. This constraint ensures that the size of array1 is fixed at 10 (array1.size() == 10) and all elements are unique (unique { array1 }).
2. Module Definition (top):sample s = new();: Creates an instance s of the sample class.repeat (5) begin ... end: Executes the block of code inside the begin and end five times.assert(s.randomize());: Attempts to randomize the s object using the constraints defined in the sample class. The assert statement checks whether the randomization is successful.$display("s=%p", s);: Displays the values of the s object after each randomization attempt.

In summary, this program aims to generate instances of the sample class (s) with a unique array of size 10. The loop attempts randomization five times, and the results are displayed. The constraints within the class ensure that the generated arrays meet the specified criteria.