There are many interesting methods of generating random numbers. Chaotic 
differential equations are sometimes used as could be the mersenne 
twister algorithm or the linear congruential generator.
You probably don't require such a thing, but there are many novel 
techniques involving hardware generation such as heat patterns, 
radiation, human interaction intervals, etc.
--
MK

Phil Keller wrote:

>All,
>
>  I have an application that I need to generate a random number sequence 
>for.  Not just a random number, I know how to do that, but an entire 
>pseudo random sequence.  The sledge-hammer approach would be to generate 
>a random number, see if it is already in the sequence and store it if it 
>is new, then generate a new random number.  Early in the process this 
>would work OK, but when I need the last four numbers the time required 
>to generate the numbers could be excessive to say the least.
>
>The details:
>-    The user will have a random number of sound files (2 to 127) on a 
>memory card.
>-    The PIC will count the number of available files and create a 
>random number sequence that is non-repeating and inclusive of all file 
>numbers.  (Each file is assigned a number so that I don't need to 
>'shuffle' the file names, just the numbers.)  I can skip files numbers 
>that are greater than the number available but a sequence that stops at 
>the maximum would be nice.
>-    The PIC will select the first file number and send the file to a 
>player.
>-    Once that file is played the PIC will select the next file number 
>in the sequence and send it to the player.
>-    Once all songs have been played once, the PIC will generate a new 
>random sequence and start over.
>
>  Suggestions or pointers are greatly appreciated.
>
>Phil
>
>
>  
>
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist