Repeated value with $dist_exponential

SystemVerilog
,
2

In reply to Phill_Ferg:
All of the functions in section 20.15 of the 1800-2012 LRM are manually seeded to be backward compatible with Verilog. The first argument to each routine is supposed to be a variable whose initial value is used as an initial seed, and is updated with the a new seed after returning from the function. If you supply the same seed value each time you call the function, you will generate the same random number returned.

To get the localized and thread-stable seeding behavior of SystemVerilog, I suggest you use $urandom to generate a seed for $dist_exponential()

begin 
  bit[7:0] [3:0] dist_value;
  int seed;
  seed = $urandom;
         foreach (dist_value[j]) begin
             mem_data = $dist_exponential(seed,60);
            dist_value[j] = mem_data;
            preload_cov.sample(mem_data);
         end
end