IPC Command RAND_CMD ($14)

[spkr]

Hi there guys,

Im looking to generate random numbers on demand, and I suppose the IPC Link is able to do this, by issuing the RAND_CMD (http://sinclairql.net/downloads/1984-00 ... d-SQPP.pdf, page 142); but I find no documentation as how to form the IPC command.

Is anyone able to point me into the right direction?

Regards,
Wietze

[janbredenbeek]

Hi there guys,

Im looking to generate random numbers on demand, and I suppose the IPC Link is able to do this, by issuing the RAND_CMD (http://sinclairql.net/downloads/1984-00 ... d-SQPP.pdf, page 142); but I find no documentation as how to form the IPC command.

From Andrew Pennell's QDOS Companion:

"This command is $E 0 ? ? ? ? 2 which returns a pseudo-random number. It is best to use only the lowest four bits though, as the highest bits tend to be zero most of the time. This is not a very good way of generating random numbers, and it's better either to read the system variable SV.RAND, or to generate your own with the floating point maths routines."

Regards, Jan.

[spkr]

Thanks for the reply, yeah it seems that getting 4 bits of randomness is a bit meh. Thanks, Ill read the system variable once to use as a seed and implement some pseudorandom number generation based on that.

[stevepoole]

Hi,

Yes Jan, we can write our own 9-digit integer random number routines.

But the main problem is how to SEED the generator : Quite easy on a QL emulator, but very hard on a non-multitasking QL !
(I have used a few methods, but none are fully satisfying).

Randomness is a subject of continued research by specialists...

Steve.

PS: if you want BIG random integers, the easiest solution is to concatenate QL ones yourself.

[XorA]

Randomness is a subject of continued research by specialists...

Not really, anything made in last decade has hardware randomness, PN junction noise and other such simple techniques.

[janbredenbeek]

I believe SV.RAND uses a better random generator algorithm on SMSQ/E than on QDOS/Minerva, which just increments it on every scheduler loop.

[NormanDunbar]

I did some randomisation stuff in the somewhat irregular ePeriodical on assembly language, Issue 8. Available at https://github.com/NormanDunbar/QLAssem ... ag/Issue_8, it all kicks off on page 47.

If it's of any use? Basically it is pretty much a blatant rip off of the SMSQ code!

Cheers,
Norm.