Re: [PD] Shuffling arrays
Yeah, urn looks like the simplest way to achieve what I want to do. Cheers, guys Date: Tue, 5 Oct 2010 08:58:51 +0200 From: f...@footils.org To: pd-list@iem.at Subject: Re: [PD] Shuffling arrays Hi, On Mon, Oct 04, 2010 at 03:07:52PM +0200, Lorenzo wrote: I guess if you only need to *read* elements of the array you could also use the [urn] object from cyclone feeding a [tabread]. Or the [urn] from Zexy or urne.pd from purepd or the identical c_urn.pd from the rj library, the abstractions being pure vanilla implementations. Ciao -- Frank ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Shuffling arrays
On 04/10/10 16:06, martin.pe...@sympatico.ca wrote: That's a bad way to shuffle, The same way that it's a really bad way to sort - maybe it could be classed as a bogobubblesort. I chose to do it that way for aesthetic purposes (a jumbled sequence gradually returns to order) rather than efficiency... This might be relevant if you value correctness: http://okmij.org/ftp/Haskell/perfect-shuffle.txt as it can swap things back again and generally reduce the randomness, the way someone who is good at shufflng cards can put them all back the way they started while appearing to mix them up. A better way is to start at the beginning of the array, swap the first item with one of the remaining items, then swap the second item, up to the end. Martin Claude wrote: On 03/10/10 23:21, Andrew Faraday wrote: Hey Guys I've recently come across the .shuffle method in Ruby which randomly re-orders the content of an array. Does anyone know of a way to do this in Pd, that is, either change the order of notes within an array or output them in a random order (without repeating any part of it)? Help would be appreciated Andrew You can pick pairs of indices at random and swap them with tabread/tabwrite; repeat to shuffle more. I used a similar technique to gradually sort an array (swap random elements only if they are out of order): https://code.goto10.org/svn/maximus/2007/clouds-are-made-of-water/ http://www.archive.org/details/ClaudiusMaximus_-_Clouds_Are_Made_Of_Water (track 5) Claude -- http://claudiusmaximus.goto10.org ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Shuffling arrays
On Tue, 5 Oct 2010, Claude Heiland-Allen wrote: The same way that it's a really bad way to sort - maybe it could be classed as a bogobubblesort. That sort is still just O(n²) in time, isn't it ? And it can finish faster than the bubble sort. Does it often do ? If you want a really slow sort, the bumblesort is rated O(n²*2^n)... This might be relevant if you value correctness: http://okmij.org/ftp/Haskell/perfect-shuffle.txt It makes a strawman example about sorting with a random key bit being attached to each element. No-one would use a random key. The rest of the argument is good, but the reader should consider what happens with 32-bit ints, and if that's not enough, 64-bit ints... In any case, if I were to code something in C++ for shuffling, I wouldn't pick this and would pick a fair shuffling instead, but it might be more because this is O(n*log(n)) and fair shufflings are doable in O(n). Btw, when you use [random n], did you wonder about the fairness of the result ? note that n is usually not a divisor of 2^32. I think that the fairness-error it introduces is bigger than the one in sorting on random 32-bit keys (but it shows more when n is high). A better way is to start at the beginning of the array, swap the first item with one of the remaining items, then swap the second item, up to the end. Yes, that's O(n), and that's what I'd use for a C++ version. ___ | Mathieu Bouchard -- Villeray, Montréal, QC___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Shuffling arrays
On Tue, 5 Oct 2010, Mathieu Bouchard wrote: It makes a strawman example about sorting with a random key bit being attached to each element. No-one would use a random key. erratum: no-one would use a single bit as a random key. ___ | Mathieu Bouchard -- Villeray, Montréal, QC___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Shuffling arrays
tim vets wrote: William Brent's tabletool ? http://williambrent.conflations.com/pages/research.html gr, Tim 2010/10/4 Andrew Faraday jbtur...@hotmail.com mailto:jbtur...@hotmail.com Hey Guys I've recently come across the .shuffle method in Ruby which randomly re-orders the content of an array. Does anyone know of a way to do this in Pd, that is, either change the order of notes within an array or output them in a random order (without repeating any part of it)? I guess if you only need to *read* elements of the array you could also use the [urn] object from cyclone feeding a [tabread]. Lorenzo Help would be appreciated Andrew ___ Pd-list@iem.at mailto:Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Shuffling arrays
On Sun, 3 Oct 2010, Andrew Faraday wrote: I've recently come across the .shuffle method in Ruby which randomly re-orders the content of an array. Does anyone know of a way to do this in Pd, that is, either change the order of notes within an array or output them in a random order (without repeating any part of it)? there's an example of shuffling at the top of [#sort]'s help file : http://gridflow.ca/help/%23sort-help.html ___ | Mathieu Bouchard -- Villeray, Montréal, QC___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Shuffling arrays
On 03/10/10 23:21, Andrew Faraday wrote: Hey Guys I've recently come across the .shuffle method in Ruby which randomly re-orders the content of an array. Does anyone know of a way to do this in Pd, that is, either change the order of notes within an array or output them in a random order (without repeating any part of it)? Help would be appreciated Andrew You can pick pairs of indices at random and swap them with tabread/tabwrite; repeat to shuffle more. I used a similar technique to gradually sort an array (swap random elements only if they are out of order): https://code.goto10.org/svn/maximus/2007/clouds-are-made-of-water/ http://www.archive.org/details/ClaudiusMaximus_-_Clouds_Are_Made_Of_Water (track 5) Claude -- http://claudiusmaximus.goto10.org ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Shuffling arrays
That's a bad way to shuffle, as it can swap things back again and generally reduce the randomness, the way someone who is good at shufflng cards can put them all back the way they started while appearing to mix them up. A better way is to start at the beginning of the array, swap the first item with one of the remaining items, then swap the second item, up to the end. Martin Claude wrote: On 03/10/10 23:21, Andrew Faraday wrote: Hey Guys I've recently come across the .shuffle method in Ruby which randomly re-orders the content of an array. Does anyone know of a way to do this in Pd, that is, either change the order of notes within an array or output them in a random order (without repeating any part of it)? Help would be appreciated Andrew You can pick pairs of indices at random and swap them with tabread/tabwrite; repeat to shuffle more. I used a similar technique to gradually sort an array (swap random elements only if they are out of order): https://code.goto10.org/svn/maximus/2007/clouds-are-made-of-water/ http://www.archive.org/details/ClaudiusMaximus_-_Clouds_Are_Made_Of_Water (track 5) Claude -- http://claudiusmaximus.goto10.org ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Shuffling arrays
On Mon, 4 Oct 2010, martin.pe...@sympatico.ca wrote: That's a bad way to shuffle, as it can swap things back again and generally reduce the randomness, the way someone who is good at shufflng cards can put them all back the way they started while appearing to mix them up. But the programme is not meaning to swap things back. If things are swapped back in a random fashion, where the probability of swapping back follows from a sequence of independent uniform random-variables, what's the problem with that ? It's like the probability of getting twice the same dice number in a row, there's a certain amount of random repetition that is considered normal. How would you write a formal proof of what you say ? But I also believe that the quickest perfectly fair shuffle is done a lot more like [urn] than like swapping random elements. The latter converges towards being fair eventually, whereas [urn] is fair in N steps if random() is fair. The former doesn't take so many steps, but one has to decide where to stop swapping, and that's not a decision I'd like to be making, so I prefer [urn]-like processes (or similarly, [#grade]-like processes). ___ | Mathieu Bouchard -- Villeray, Montréal, QC___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
[PD] Shuffling arrays
Hey Guys I've recently come across the .shuffle method in Ruby which randomly re-orders the content of an array. Does anyone know of a way to do this in Pd, that is, either change the order of notes within an array or output them in a random order (without repeating any part of it)? Help would be appreciated Andrew___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Shuffling arrays
William Brent's tabletool ? http://williambrent.conflations.com/pages/research.html http://williambrent.conflations.com/pages/research.htmlgr, Tim 2010/10/4 Andrew Faraday jbtur...@hotmail.com Hey Guys I've recently come across the .shuffle method in Ruby which randomly re-orders the content of an array. Does anyone know of a way to do this in Pd, that is, either change the order of notes within an array or output them in a random order (without repeating any part of it)? Help would be appreciated Andrew ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
