Asher

Recently one of my friends asked me to help them implement the 'vose alias' algorithm as described at the end of this article: https://www.keithschwarz.com/darts-dice-coins/

the problem is fairly simple in formulation:

"You are given an n-sided die where side i has probability p(i) of being rolled. What is the most efficient data structure for simulating rolls of the die?"

...but was quite difficult in gen, as arrays in max 'dont exist'

I thought it would be an interesting challenge to attempt writing the entire thing in genExpr, which required creating some pseudo 'array functions' that work on buffers- (a buffer push/pop function, finding the bounds of a buffer, and checking if the buffer is empty). My solution was to set the buffer length in samples, and then to 'resize' the array by the way of using -1. sample values to signify the indices to ignore (if you use them, these functions wont work with negative values!).

Attached is the algorithm and a little groove~ jam that you can use with it. Pretty niche but maybe someone will find it interesting :)

diceCoin.gendsp

vose_alias_gen.maxpat

vose_array.gendsp

I thought it would be an interesting challenge to attempt writing the entire thing in genExpr, which required creating some pseudo 'array functions' that work on buffers-  (a buffer push/pop  function, finding the bounds of a buffer, and checking if the buffer is empty). My solution was to set the buffer length in samples, and then to 'resize' the array by the way of using -1. sample values to signify the indices to ignore (if you use them, these functions wont work with negative values!). 

Attached is the algorithm and a little groove~ jam that you can use with it. Pretty niche but maybe someone will find it interesting :) 

Recently one of my friends asked me to help them implement the 'vose alias' algorithm as described at the end of this article: https://www.k

sharing-vose-alias-algorithm-in-gen

tried this twice and couldn't get it working... finally realize: i think your "dice+coin.gendsp" file somehow got corrupted on the upload(if you open the other two in a new web-browser page, you'll see they read like regular max-file text, but open dice+coin.gendsp in a web-browser and you get this XML error:

https://cycling74-web-uploads.s3.amazonaws.com/54648c2c06e117ca5ee4200c/2020-11-27T13:48:25Z/dice+coin.gendsp

maybe you can try uploading just that one file again? 

(without it, the patch just loads an empty gen~ patcher in its place and plays the first beat of the loop over and over)

tried this twice and couldn't get it working... finally realize: i think your "dice+coin.gendsp" file somehow got corrupted on the upload(if you open the other two in a new web-browser page, you'll see they read like regular max-file text, but open dice+coin.gendsp in a web-browser and you get this XML error:
https://cycling74-web-uploads.s3.amazonaws.com/54648c2c06e117ca5ee4200c/2020-11-27T13:48:25Z/dice+coin.gendsp )

maybe you can try uploading just that one file again? 
(without it, the patch just loads an empty gen~ patcher in its place and plays the first beat of the loop over and over)

very weird, i saw this happen on another persons post - perhaps due to nonallowed characters?

I've updated the files in the original above

ah, cool, thank you for sharing this. it's working nicely now(can see having good sequencing fun with this). 

ah, cool, thank you for sharing this. it's working nicely now(can see having good sequencing fun with this). 
that's a funky drummer!  :D

also, playing around with this, i see it can be more efficient using the 'diceCoin' gen~ without the tilde for just generating events with metro instead of phasor~:

Screen Shot 2020-11-29 at 6.53.34 PM.png

i think i might use this quite a bit actually, thanks again!

also, playing around with this, i see it can be more efficient using the 'diceCoin' gen~ without the tilde for just generating events with metro instead of phasor~:


thanks raja, i wanted to test that you could run the 'coinflip' subroutine at sample rate, but good to know it works fine at event rate too!

Sharing: Vose Alias algorithm in Gen