# [PD] array-abs

Matt Barber brbrofsvl at gmail.com
Sun Oct 4 21:38:50 CEST 2015

```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 at 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 at 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 at gmx.at>
> > > *An:* "Matt Barber" <brbrofsvl at gmail.com>
> > >
> > > *Cc:* Pd-List <pd-list at 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 at gmail.com>
> > > *An:* "IOhannes m zmölnig" <zmoelnig at iem.at>
> > > *Cc:* Pd-List <pd-list at 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 at 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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