Unique Constraint - using Dynamic Arrays

SystemVerilog
, ,
1

Hi all,

Just a quick question on using Dynamic Arrays on Unique Constraints.

// `timescale 1ms / 1ns

module example_unique (

);
/*-----CLASSES-----*/
class the_inputs; 
    rand bit [2:0]  inputA;
    rand bit [2:0]  inputB;

    rand int the_array[8];    
    rand int that_array[8];

    constraint limit {
                        unique {inputB, inputA};
                        inputB inside {[0:7]};
                        inputA inside {[0:7]};
                     }

    constraint limit_array {    unique {the_array};

                                foreach(the_array[i]) 
                                    {the_array[i] inside {[0:7]};}   
                            }

    constraint lim_arrver2 {    unique{that_array};

                                foreach(that_array[i]) 
                                    {that_array[i] inside {[0:7]};}                            
                            }

endclass :  the_inputs


initial begin
    the_inputs test1; 
    test1 = new();

    for (int i = 0; i < 8; i++)
    begin
        test1.randomize(); 
        $display("inputA: %0d   inputB: %0d   arrayA: %0d   arrayB: %0d ", test1.inputA, test1.inputB, test1.the_array[i], test1.that_array[i]);

    end

    $finish; 
    end

endmodule

I was just wondering for my declaration/instantiation of the two arrays within the class the_inputs, how would the following code be different if I were to use dynamic arrays of undefined size? For example, what if it were to be:

class the_inputs; 
    rand bit [2:0]  inputA;
    rand bit [2:0]  inputB;

    rand int the_array[];    
    rand int that_array[];

    constraint limit {
                        unique {inputB, inputA};
                        inputB inside {[0:7]};
                        inputA inside {[0:7]};
                     }

    constraint limit_array {    unique {the_array};

                                foreach(the_array[i]) 
                                    {the_array[i] inside {[0:7]};}   
                            }

    constraint lim_arrver2 {    unique{that_array};

                                foreach(that_array[i]) 
                                    {that_array[i] inside {[0:7]};}                            
                            }

endclass :  the_inputs

Would anything be different, or is it something I have to make changes in the rest of my code?

Thank you!

Sangwoo

2

You should new the dynamic array before you use foreach.

3

The SystemVerilog solver will not change the size of a dynamic array without a constraint on the size of the array. Before randomization starts, you either need to construct with new[], initialize it from another array, or have a constraint on its size.

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