RE: [sv-ec] $random(), $urandom()

Hi, 

> -----Original Message-----
> From: owner-sv-ec@server.eda.org 
> [mailto:owner-sv-ec@server.eda.org] On Behalf Of Clifford E. Cummings
> Sent: Thursday, June 11, 2009 8:09 PM
> To: sv-ec@server.eda.org
> Subject: [sv-ec] $random(), $urandom()
> 
> Thanks, Shalom -
> 
> I have run into issues with empty parentheses in the past with one 
> implementation, but not with the two implementations that I 
> tested yesterday.
> 
> I am not as certain about the integral number -vs- integral 
> variable issue.
> 
> I did find text supporting your position in the third paragraph of 
> clause 20.15.1 (ballot draft):
> The seed argument shall be an integral variable. The seed value 
> should be assigned to this variable prior to calling $random.
> But I wonder if that is a mistake. Do you have access to any tools 
> that do not support integral numbers inside of the parentheses? 

Yup. We have also discussed this before.

> Seems 
> like if one uses $random(integral_number), one would always get the 
> same value returned, which is what I observed. Adding the integral 
> variable allows $random to change the seed between calls.
> 
> Regarding $urandom(integral_number), from the second paragraph of 
> 18.13.1 (ballot draft):
> The seed is an optional argument that determines the sequence of 
> random numbers generated. The seed can be any integral expression. 
> The random number generator (RNG) shall generate the same sequence of 
> random numbers every time the same seed is used.
> And the subsequent example shows: addr[32:1] = $urandom(254);

$urandom is different than $random.

Regards,
Shalom
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Intel Israel (74) Limited

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