I think matju wrote the [list-drip] algorithm partly to show the difficultyof using recursion in Pd. That the actual author of Pd's messagingsystem refrains from using recursion to solve the same problem addsweight to that point. -Jonathan
On Sunday, October 4, 2015 3:45 PM, Matt Barber <brbrofsvl@gmail.com> wrote:
It takes almost a full second to output a list of n=1,000,000 with a 100-cycle until on my computer. On Sun, Oct 4, 2015 at 3:38 PM, Matt Barber brbrofsvl@gmail.com wrote:
This is still much slower than [list-drip], and it freezes Pd for me when I get up to lists of n=100,000 or so. I think it's because Pd has to copy the list to an output every cycle of [until], so when n=10, you're only outputting something of size 10 10 times, but that grows by n^2 so when it's n=10,000 times 10,000 outputs, it's a lot. 1,000,000 seems impossible unless the list decreases in size each cycle, which it does in [list-drip], recursively. On Sun, Oct 4, 2015 at 2:48 PM, Miller Puckette msp@ucsd.edu wrote:
Here's a way to serialize a list in (I believe) linear time:
#N canvas 881 291 450 300 10; #X msg 136 14 list 3 . 1 4 1 5 9; #X obj 83 97 list length; #X obj 77 211 list split; #X obj 101 186 list; #X obj 139 55 t l b l; #X obj 83 119 until; #X obj 83 141 f; #X obj 114 142 + 1; #X msg 166 117 0; #X obj 83 163 t b f; #X obj 117 278 print; #X obj 116 250 list split 1; #X connect 0 0 4 0; #X connect 1 0 5 0; #X connect 2 1 11 0; #X connect 3 0 2 0; #X connect 4 0 1 0; #X connect 4 1 8 0; #X connect 4 2 3 1; #X connect 5 0 6 0; #X connect 6 0 7 0; #X connect 6 0 9 0; #X connect 7 0 6 1; #X connect 8 0 6 1; #X connect 9 0 3 0; #X connect 9 1 2 1; #X connect 11 0 10 0;
cheers Miller
On Sun, Oct 04, 2015 at 02:27:37PM -0400, Matt Barber wrote:
Your [pd drip] does a lot of extra work. It's go basically linear stack performance, and you're recopying the list every loop (an until loop would solve this for a little extra cpu time). The secret of [list-drip] is that it doesn't recopy the list using the [list] object, and it avoids stack overflows by doing the recursion split at the midpoint of the list and only outputting when it's done the binary split down to lists of size 1, which are the elements, or size zero, which are bangs (and which are filtered out).
Since it's binary recursion on the list, the stack only grows proportionally to log_2(n), which is about 20 for n=1,000,000. It's still going to be slower than an object written in C that can just iterate over the contents in a single loop, and lists in Pd are slower in general than arrays, so an until loop and tabread over an array is going to be quicker. It is much slower for copying though -- an until loop with tabread and tabwrite has way more overhead than an [array get]-[array set] pair.
On Sun, Oct 4, 2015 at 1:06 PM, Christof Ressi christof.ressi@gmx.at wrote:
Please don't use the previous version of the multi-dimensional arrays!!! First, I forget to get rid of one [drip] object. Second, I discovered that [pd drip] will create a stack overflow if there are more than ca. 300 elements! (Why???) So I replaced it with [list-drip] which works fine.
So here's the corrected pure vanilla version + a zexy version using [drip]. I prefer to use the latter one because it's waaaaay faster than all the drip abstractions based on [list split].
Vanilla: https://www.dropbox.com/s/wd0avxtaneqgdic/carray_vanilla.zip?dl=0 Zexy: https://www.dropbox.com/s/ea8kihwbdqhcajr/carray_zexy.zip?dl=0
Christof
PS: I did a benchmark test of iterating through an array of 1 million elements, using [realtime], and here's what I found on my system:
[array get] + [drip] --> ca. 6.5-9ms [until] + [tabread] --> ca. 120-200ms [array get] + [list-drip] --> ca. 340-400ms
To me this result was a bit surprising...
You can test yourself with the attached patch. *Gesendet:* Sonntag, 04. Oktober 2015 um 17:32 Uhr *Von:* "Christof Ressi" christof.ressi@gmx.at *An:* "Matt Barber" brbrofsvl@gmail.com
*Cc:* Pd-List pd-list@lists.iem.at *Betreff:* Re: [PD] array-abs Wow, looks cool!
Just a few days ago I reworked some of my personal table abstractions, which also make use of the [array] object. However, some of them depend on zexy externals (I hope I didn't miss any other dependencies). I haven't shared them yet so the documentation is quite poor (no help files, docs inside the abstraction) and they look a bit messy. But maybe you can get some inspiration for your library... https://www.dropbox.com/s/xvj031korqw8guf/ctab-abs.zip?dl=0
Additionally I've been working on three basic abstractions for creating, setting and reading multi-dimensional arrays of any number of dimensions. They are pure vanilla style and even come with a help file :-D. (a object for array resizing is yet to be done...) https://www.dropbox.com/s/6xfgdyt697138e6/carray.zip?dl=0
Would be cool to hear your opinion on the multi-dimensional array stuff!
Christof
*Gesendet:* Samstag, 03. Oktober 2015 um 22:32 Uhr *Von:* "Matt Barber" brbrofsvl@gmail.com *An:* "IOhannes m zmölnig" zmoelnig@iem.at *Cc:* Pd-List pd-list@lists.iem.at *Betreff:* Re: [PD] array-abs Thanks.
Yes. Right now I'm just looking to see if these would be useful, if there's anything awful about the syntax, if they try to do too much or are too fussy, if anyone would want to contribute, etc. When I get them polished a bit I'll do a regular release on the normal channels (I can't remember if I have access to anything officially Pd related).
Matt
On Sat, Oct 3, 2015 at 4:22 PM, IOhannes m zmölnig zmoelnig@iem.at wrote:
hi,
great!
On 10/03/2015 07:36 PM, Matt Barber wrote:
https://www.dropbox.com/s/45tk62dpz0z2mqo/array-abs.zip?dl=0
db?
would you like to put those on a version control system of sorts, e.g. the puredata svn or some publicly available git repository (e.g. github)?
(read as: please let us not go back to the dark ages, where code was shared by sending files around by on floppy disks and you never new which version was the current one)
fgmards IOhannes
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