When I say "left-side" I'm talking about the left side of the list itself, which is sent for processing by the [>> 1]-[list split] on the right side of the patch. Depth-first ensures that all of the left parts of the list chunks will all be processed before the corresponding right chunks.
Again, it may be easier to look at [list-rdrip]. On Mon, Oct 5, 2015 at 11:08 AM, Jonathan Wilkes <[email protected]> wrote: > > Depth-first ensures that all of the left-side processing will happen > before any of the right side. > > Not sure I understand that. > The right-side [>> 1]--[list split] will recurse and end up sending the > first element to the outlet before [trigger] ever sends anything > to the left side. "Depth-first" applies equally to recursive depth. You > keep doing somersaults until you have no more somersaults > to do. > > As for C, recursion is still difficult but it's also equally powerful. > However, if everything except the first argument got borked when > you tried to do recursive functions I doubt anyone would be using it. :) > > -Jonathan > > > > > > On Monday, October 5, 2015 9:57 AM, Matt Barber <[email protected]> > wrote: > > > Recursion can be difficult to understand even in c or a functional > programming language. Sticking a [print] in various stages should help > visualization. > Here's how I'd describe it: > Input list. Split it in half – [>> 1]-[list split] – and send the left > side for processing first and the right side last. Depth-first ensures that > all of the left-side processing will happen before any of the right side. > Keep splitting and sending left sides until a list arrives whose length is > less than 2 – [list split 2] at the top. If it is, it's either an empty > list or a singleton, so it doesn't need to be processed further – [spigot] > – and we can send it out (filtering out any empty lists). Then the right > side of the most recent list to be sent in for processing (let's name that > list Greg) is sent for processing, and when Greg's right side has all been > split and output, then the right side of Greg's parent list can be sent. > As with most binary procedures you could graph the process as a simple > binary tree where the root node represents the initial list and daughter > nodes are the left and right halves of lists that have been split. > Traversing the tree means that when you get to a node you haven't visited > yet, always take the left side of the fork first to get to the next level > down. When you return to that node you can then take the right side of the > fork. Once you've taken both paths all the way to the branches you can go > back up a level. Continue this until you've taken both branches of the root > node. > > The [>> 1] isn't just to avoid a stack overflow – splitting the lists as > close as possible to half also happens to be the fastest way of going about > the recursion. It's one of the reasons quick sort is still one of the > fastest available sorts. > > On Oct 5, 2015 3:16 AM, "Jonathan Wilkes" <[email protected]> wrote: > > Yes that's true about iterative approaches and dataflow in general. > > What gets me about [list-drip] is the necessity of the [>> 1] to prevent > stack overflow. So even if you can follow the order of operations with > recursion through that object chain, you have to also keep track of > the order in which those two branches interact during the recursion. > > I can visualize that using a small set of data to the inlet, and taking my > time. > But at that point the diagram itself isn't elucidating anything useful > about > the flow of data. For that you'd need some way to animate the flow through > the wires in greater than zero logical time. And even then you'd want to > show > the actual data associated with each cycle of animation. > > -Jonathan > > > > > On Monday, October 5, 2015 1:59 AM, Matt Barber <[email protected]> > wrote: > > > Not supporting recursion in a dataflow environment is not a huge problem > IMO, especially since so many classically recursive problems (binary > search, quick sort, etc.) can be solved iteratively. The iterative solution > is almost always going to be clearer in an environment like Pd. > > [list-drip] is a decent model for how recursion would have to work -- > [list-rdrip] even more, since it can take advantage of the native > right-to-left output to reduce the number of objects. Anything solved using > a divide-and-conquer strategy could even be a bit faster using the stack > vs. an until loop. A while back I made a kind of clunky iterative quick > sort; I wonder if it would be possible to throw ranges to partition onto > Pd's stack without it overflowing ... probably not since there's nothing to > guarantee that quick sort doesn't run at O(n^2) in the worst case. Binary > search almost certainly could; I'll do that in the next few days and post > benchmarks comparing an [until] loop solution with recursion. > > On Sun, Oct 4, 2015 at 4:12 PM, Jonathan Wilkes <[email protected]> > wrote: > > I think matju wrote the [list-drip] algorithm partly to show the difficulty > of using recursion in Pd. That the actual author of Pd's messaging > system refrains from using recursion to solve the same problem adds > weight to that point. > > -Jonathan > > > > > > On Sunday, October 4, 2015 3:45 PM, Matt Barber <[email protected]> > 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> > > 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" <[email protected]> > > > *An:* "Matt Barber" <[email protected]> > > > > > > *Cc:* Pd-List <[email protected]> > > > *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" <[email protected]> > > > *An:* "IOhannes m zmölnig" <[email protected]> > > > *Cc:* Pd-List <[email protected]> > > > *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 <[email protected]> > > > 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 > > >> > > >> > > >> > > >> _______________________________________________ > > >> [email protected] mailing list > > >> UNSUBSCRIBE and account-management -> > > >> http://lists.puredata.info/listinfo/pd-list > > >> > > > > > > _______________________________________________ [email protected] > > > mailing list UNSUBSCRIBE and account-management -> > > > http://lists.puredata.info/listinfo/pd-list > > > _______________________________________________ [email protected] > > > mailing list UNSUBSCRIBE and account-management -> > > > http://lists.puredata.info/listinfo/pd-list > > > > > > _______________________________________________ > > [email protected] mailing list > > UNSUBSCRIBE and account-management -> > http://lists.puredata.info/listinfo/pd-list > > > > > _______________________________________________ > [email protected] mailing list > UNSUBSCRIBE and account-management -> > http://lists.puredata.info/listinfo/pd-list > > > > > > > >
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