Random Numbers? - Script Writing - CHDK Forum supplierdeeply

Random Numbers?

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Offline ab

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Random Numbers?
« on: 28 / April / 2008, 18:15:36 »
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Is there a way to have Ubasic generate random numbers?  If so that would be great!

Could I call out to the system clock at least and multiply through that to generate quasi-random numbers?


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Offline fbonomi

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Re: Random Numbers?
« Reply #1 on: 28 / April / 2008, 18:30:39 »
yes, you could... how accurate must this random generator be?

How often must you get those random numbers?

What range of nymbers do you need (how many different vakues yiu need)?




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Offline ab

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Re: Random Numbers?
« Reply #2 on: 28 / April / 2008, 18:37:39 »

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Offline waldo

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Re: Random Numbers?
« Reply #3 on: 28 / April / 2008, 19:40:14 »
From your description, I would think a pseudo-random sequence of 8 bit numbers that repeats every 256 values would suffice.  If so, consider using a Linear Feedback Shift Register (LFSR).  It's a very simple way of creating an arbitrarily long sequence.  Here's code for a CHDK script that does an 8-bit LFSR:

Code: [Select]
@title LFSR Test

rem 8 bit lfsr test
rem c contains pseudo-random number

c = 1

for g=0 to 1000
gosub "lfsr8"
print c
sleep 100
next g

end


:lfsr8
if (c & 1) = 1 then
c = (c/2) ^ 142
else
c = c / 2
endif

return

Have fun !
« Last Edit: 28 / April / 2008, 19:42:17 by waldo »


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Offline ab

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Re: Random Numbers?
« Reply #4 on: 28 / April / 2008, 19:46:56 »
How big are those numbers going to be???

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Offline waldo

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Re: Random Numbers?
« Reply #5 on: 28 / April / 2008, 22:39:48 »
0 to 255.  You can scale them down with division or use more bits in the sequence for a larger range.

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Offline PhyrePhoX

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Re: Random Numbers?
« Reply #6 on: 29 / April / 2008, 00:53:45 »
you can also use my build from http://chdk.setepontos.com/index.php/topic,978.0.html, it has (among other stuff) a random function for ubasic. someday in the future i guess it will be incorporated in the official build :)

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Offline ab

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Re: Random Numbers?
« Reply #7 on: 29 / April / 2008, 01:13:38 »
I posted some preliminary results over on my blog ---

 … timelapse focus wobble script … @ Arman Bohn

PhyrePhox - I'll look into your random function next.


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Offline PhyrePhoX

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Re: Random Numbers?
« Reply #8 on: 29 / April / 2008, 01:27:43 »
well, i guess waldo's script does it for you already :)
my build could help though when you need to write a smaller script (also it should be like 50 ms faster each time random is executed, to the least), also i guess it is "more random", as it uses the tickcount as seed.
looking forward to seeing your video, looks very promising. i also might add that i quite like your music :)

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Offline ab

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Re: Random Numbers?
« Reply #9 on: 29 / April / 2008, 01:44:37 »
Thanks!

I've been working on my first full length in 10 years.  Having a blast with an A640 and the scripts.

How can I get your firmware into my cam?

I'm downloading it now.....

Is it any different than loading the other firmwares?

 

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