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Design Languages >> Verilog-AMS >> $random, $arandom and repeatability across simulators
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Message started by Ari on Dec 16^th, 2009, 2:01pm

Title: $random, $arandom and repeatability across simulators
Post by Ari on Dec 16^th, 2009, 2:01pm

Hi,

I have two questions regarding $random and $arandom

1. Except for the fact that $arandom supports global/local randomization, and that its seed can be a parameter, are there any further differences between it and $random?
I don't see why both $random and $arandom are supported, as it seems one will always want to use $arandom.

2. Often I build a Verilog-A view which is simulated in several simulators (SPICE, fast SPICE, etc..)
It is not clear from the LRM if results of $random/$arandom should be repeatable across simulators.
i.e., when running in simulator (A), I am getting certain random output (and it is repeatable across different runs)
Once I switch to simulator (B), is there a built-it random function which is guaranteed to give the same results like in simulator (A) ?

Regards,

Ari

Title: Re: $random, $arandom and repeatability across simulators
Post by Geoffrey_Coram on Dec 18^th, 2009, 7:17am

1) I believe $random is part of 1364 Verilog and/or 1800 SystemVerilog, and Verilog-AMS needed a new function name to add the additional arguments

2) I doubt the results would be repeatable across simulators, not even two versions of the same simulator; I think the LRM only says that the same simulator, running the same netlist with the same seed, should give the same answer.