How to Randomize parameter by using another random parameter? - system-verilog

Question

I trying to write a random parameter to my program, but my program some parameter will use other parameter for range. I try to get from online but cannot get it. Then, i decide come here ask about it.
Hope anyone can help.
rand bit COMMON_CLK;
rand int DEPTH;
rand int DATA_WIDTH
rand int PROG_FULL_ASSERT;
rand int PROG_FULL_NEGATE;
rand int PROG_EMPTY_ASSERT;
rand int PROG_EMPTY_NEGATE;
constraint DEPTH {
DEPTH inside {[16:100000]};
DATA_WIDTH inside {[1:1024]};
}
constraint ASSERT {
PROG_FULL_ASSERT inside {[1:DEPTH.size]};
}
constraint NEGATE {
PROG_FULL_NEGAT inside {(1:PROG_FULL_ASSERT.size]};
}
constraint ASSERT {
PROG_EMPTY_ASSERT inside {[1:((DEPTH.size) - 1)]};
}
constraint NEGATE {
PROG_EMPTY_NEGATE inside {[(PROG_EMPTY_ASSERT.size) : ((DEPTH.size) - 1)]};
}

Answer 1

First, like Dave_59 pointed out DEPTH.size is not good code even if it does do something legal.
Secondly, if you wanted something like PROG_FULL_ASSERT inside {[1:DEPTH]}; you may want to add solve DEPTH before PROG_FULL_ASSERT to avoid distribution issues.
Lastly, in my experience sometimes it's better or at least easier to randomize some things in post.randomize(). This is assuming that nothing else is depending on them. For example:
int array;
rand int array_size;
constraint {array_size inside [100000:200000];}
void function post_randomize();
array = new[array_size];
array_data_randomization_function();
endfunction
This is not always a good idea because it adds the risk of later adding rand variables that depend on the post randomized one (array), BUT it does break the randomization to two independent actions, making the code easier to understand, and in case of heavy randomizations also makes it calculate faster.