Constraint for a rand variable to behave like a randc.

In order to achieve the requested constraint, we first need to understand the difference between rand and randc variables.

Rand: By defining a variable as rand, it becomes an active variable when you randomize the object created for the class where the variable is defined. While randomizing, it will take possible values that obey the constraints written for that variable. If no constraints are specified, it can generate any value in its range and may repeat the same value multiple times without producing all possible values.

Randc: randc behaves similarly to rand, but with an additional feature denoted by the “c” for cyclic. This cyclic behavior allows the variable to generate all possible values, but without repeating any value until it has generated all possible values at least once.

For example, consider a 3-bit variable a. If a is declared as rand, it can take any value from 0 to 7 while randomizing. It may repeat values before generating all values from 0 to 7. On the other hand, if a is declared as randc, it won’t repeat any generated value until it has generated all values from 0 to 7.

To make a rand variable behave like a randc variable, we can use a queue to store generated values. This queue ensures that the upcoming value is not already present in the queue, effectively preventing value repetition until all possible values have been generated. The size of the queue should be 2^x for an x-bit variable.

Here is an example code for the constraint:

https://www.edaplayground.com/x/MAqm

I appreciate your understanding of the methodology we’ve utilized to handle constraints and their real-world applications. Your support, through likes and reposts, will indeed encourage further exploration. I’m eagerly looking forward to engaging in meaningful discussions with you.

Thank you! 😊🌟

Decoding of the Above Code:

In Class

• Class Declaration: Declares a class named “sample” containing a random variable “rand_a” and a dynamic array “rand_q” to store the last 7 values of “rand_a”.
• Random Variable Declaration:Declares a random 3-bit variable named “rand_a” within the “sample” class. The variable is declared as a random variable (rand), which means it will be randomized during object creation.Declares a dynamic array named “rand_q” to store the last 7 values of “rand_a”.
• Constraint: Defines a constraint named “rand_a_c” which imposes the following condition on the “rand_a” variable and “rand_q” array:The combination of “rand_a” and the values in “rand_q” must be unique.

In Module Top

• Instantiation of Class: Instantiates an object of the “sample” class named “s”.
• Initial Block: Executes the following actions:Displays a header indicating the beginning of the output.Repeats 10 times:Randomizes the data members of the object “s” according to the constraints specified in the class definition.Displays the value of “rand_a”.Displays the values of “rand_q” which represent the last 7 values of “rand_a”.Displays a message explaining that there is no repetition in the generated values of “rand_a” and “rand_q” despite “rand_a” being a random variable.

This program generates random values for the variable “rand_a” and ensures that the combination of “rand_a” and the last 7 values of “rand_a” stored in “rand_q” are unique. The output displays the generated values of “rand_a” and “rand_q”.