Hi deve …
Yes . all codes are in single module(inside fork join)
$display("start1 = %0t end1 = %0t duration = %0t “,start1,end1,duration);
$display(” total bits = %0d bandwidth = %f ",total_bits,bandwidth);
Without seeing all of your code, it is hard to give you a good answer, but using %t is probably obscuring the issue. Without using $timeformat %t assumes the argument’s value is in the current time unit and then scales it to the global time precision (smallest precision of all designs).
I suggest you normalize the start and end values to *1ps. Also display your normalised values using %f.