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Simulators >> Circuit Simulators >> generate two different random integers on HSPICE
https://designers-guide.org/forum/YaBB.pl?num=1479588462

Message started by AA on Nov 19^th, 2016, 12:47pm

Title: generate two different random integers on HSPICE
Post by AA on Nov 19^th, 2016, 12:47pm

Is there a way to generate two distinct random integers on HSPICE?

For example, I can generate two random integers, a and b, from 0 to 9 as follows:

Code:

.param rng = aunif(5, 5)
.param a = int(rng)
.param b = int(rng)

However, I want a and b to be two different numbers, with some sort of randomness.
The code above may generate the same value for a and b. How to make sure a and b are always different and within the range?

Title: Re: generate two different random integers on HSPICE
Post by Geoffrey_Coram on Nov 21^st, 2016, 12:12pm

Why not do

Code:

.param a = aunif(5, 5)
.param b = aunif(5, 5)

Title: Re: generate two different random integers on HSPICE
Post by AA on Nov 22^nd, 2016, 3:32pm

Two reasons:
(1) I need a and b to be integers
(2) I need a and b to be different numbers on every Monte Carlo iteration ,i.e., when performing MONTE sweep. For example, if a=4, then b cannot be 4. In other words, the random number generator should reject the value of b when it equals to a, and keeps regenerating b until b!=a.

The code you provided may generate the same value for a and b (especially when converted to integers) in the subsequent Monte Carlo iterations.

I hope there is a way to do this in HSPICE. Otherwise, I will probably need to write a Verilog-A module. Also, if this is not possible in HSPICE, please provide a hint on the best way to implement this functionality on Verilog-A. I especially need to know how to consume the Verilog-A module's outputs (a and b) as HSPICE parameters.

Title: Re: generate two different random integers on HSPICE
Post by Geoffrey_Coram on Nov 28^th, 2016, 10:48am

I missed the point that you want to enforce a != b, sorry.

What about something like

Code:

.param a = int(aunif(5,5))
.param temp = int(aunif(5,4.5)-0.5)
.param b = (a == temp) ? 9 : temp

'temp' should be from 0 to 8, and when it's the same as a, b is set to 9.