From: "Thompson, David" <dthompson2@worcester.edu>
To: Taylan Kammer <taylan.kammer@gmail.com>
Cc: Guile User <guile-user@gnu.org>
Subject: Re: [EXT] Re: Question about data structures
Date: Mon, 23 Nov 2020 09:54:35 -0500 [thread overview]
Message-ID: <CAJ=Rwfas4F7zsTLLjU50=o3n9h1C=6S46aC-dLvZg3BWX7xLYQ@mail.gmail.com> (raw)
In-Reply-To: <a5317e0c-9fe0-1fb9-c6b5-d3065d179285@gmail.com>
On Sun, Nov 22, 2020 at 10:43 PM Taylan Kammer <taylan.kammer@gmail.com> wrote:
>
> Python lists, JDK's ArrayList, and .NET ArrayList, among probably many
> other "list" or "array" data structures in popular languages nowadays
> use a relatively straightforward data structure that is backed by an
> actual array which can have empty slots (e.g. your Python list with 3
> elements might be backed by an array of size 10), and is reallocated
> whenever there's no space left. This means that appending an element at
> the end is usually dirt cheap, until there's no space left, at which
> point the append operation is much heavier for one call, then the
> following calls are dirt cheap again, until it's full again...
>
> Inserting an element at the beginning or middle is also relatively
> expensive with those implementations, since all elements need to be
> shifted forward to make space for the new element. (Although this might
> be done with an operation like C's memcpy which is still actually very
> fast.)
>
> It's called a "dynamic array" by Wikipedia:
>
> https://en.wikipedia.org/wiki/Dynamic_array
>
> If you want to go on an adventure, you could implement a Scheme data
> structure called DVector that implements this strategy, using plain
> Scheme vectors for the backing array.
If anyone is interested in such a data structure, I have an
implementation available here:
https://git.dthompson.us/chickadee.git/tree/chickadee/array-list.scm
I typically use them as object pools to reduce allocation and thus GC
pressure in the context of video games. The array-list-push! and
array-list-pop! procedures make it easy to use as a dynamically
expanding stack.
- Dave
next prev parent reply other threads:[~2020-11-23 14:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-22 18:48 Question about data structures Zelphir Kaltstahl
2020-11-22 19:45 ` divoplade
2020-11-22 20:24 ` Zelphir Kaltstahl
2020-11-22 21:00 ` divoplade
2020-11-28 2:47 ` Zelphir Kaltstahl
2020-11-22 20:58 ` kwright
2020-11-22 22:50 ` Tim Van den Langenbergh
2020-11-23 3:42 ` Taylan Kammer
2020-11-23 4:42 ` John Cowan
2020-11-23 14:54 ` Thompson, David [this message]
2020-11-23 9:52 ` Neil Jerram
2020-11-23 12:24 ` Dr. Arne Babenhauserheide
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