In reply to ajeetha:
Hi Ajeetha,
I like your solution, even if it only runs on Questa at the moment!
However, using an inside constraint will give a value with 2 bits set to 1, most of the time (presumably because the constraint solver has to pick a value for vec_1 before calling $countones and there are many more combinations of vec_1 with 2 bits set than just one).
An alternative constraint to overcome that problem would be to use dist instead:
constraint cdist {$countones(vec_1) dist{1:=90, 2:=10};}
to give a value with only 1 bit set to 1 approximately 90% of the time.
Regards,
Dave