> my range tree is just a slightly modified b-tree. But usually when people talk about b-trees they mean a BTreeMap. Thats not what I'm doing here. Instead of storing keys, each internal node of the b-tree stores the total number of characters (recursively) in that item's children. So we can look up any item in the document by character position, or insert or delete anywhere in the document in log(n) time.
Ever since I made it, I've been looking for a good application for it. I guess this is it! I mean, I knew A-List was a good data structure for text editing, but most applications can use a Gap Buffer which is much simpler. But when it comes to concurrent editing, you've got multiple editing points so a Gap Buffer is suddenly much less attractive.
> Honestly I'm shocked and a little suspicious of how little ram Yjs uses in this test.
It's good, but still it uses ~30x as much RAM as plain string edits. Not surprisingly, you got 3x better memory usage by using A-List and a more efficient language (Rust in this case, but C# and C/C++ can also do well.)
There is a great article about a CRDT concept called "Causal Trees[1]. I wonder how it compares to flat-list-based CRDTs (it's been too long since I researched this).
By the way, Microsoft has a new set of libraries for concurrent editing called Fluid Framework[2]. I'm told it's a "generalized data structure" that was inspired by Causal Trees but with a unique and intention-preserving editing scheme. I found out about it after they decided to use my fast-cloning-copy-on-write B+Tree for TypeScript[3]... they sent me a pull request for diffing versions of B+ trees, but I haven't yet looked into the architecture of their concurrent data type.
The key argument seems to be "type checking and red squiggly underlines save you time" - I would also attest to that, but isn't there a way to do this in Python now? I would also suggest C#, with its Code Completion, as great at helping you write quick scripts, especially now that it has a REPL with full Code Completion, red-squiggly underlines and syntax highlighting in Visual Studio, plus language features like pattern matching, tuples and LINQ.
Cool! This is essentially the same idea I implemented in 2012; I call it the AList or A-List data structure: http://core.loyc.net/collections/alists-part1
Ever since I made it, I've been looking for a good application for it. I guess this is it! I mean, I knew A-List was a good data structure for text editing, but most applications can use a Gap Buffer which is much simpler. But when it comes to concurrent editing, you've got multiple editing points so a Gap Buffer is suddenly much less attractive.
> Honestly I'm shocked and a little suspicious of how little ram Yjs uses in this test.
It's good, but still it uses ~30x as much RAM as plain string edits. Not surprisingly, you got 3x better memory usage by using A-List and a more efficient language (Rust in this case, but C# and C/C++ can also do well.)
There is a great article about a CRDT concept called "Causal Trees[1]. I wonder how it compares to flat-list-based CRDTs (it's been too long since I researched this).
By the way, Microsoft has a new set of libraries for concurrent editing called Fluid Framework[2]. I'm told it's a "generalized data structure" that was inspired by Causal Trees but with a unique and intention-preserving editing scheme. I found out about it after they decided to use my fast-cloning-copy-on-write B+Tree for TypeScript[3]... they sent me a pull request for diffing versions of B+ trees, but I haven't yet looked into the architecture of their concurrent data type.
[1] http://archagon.net/blog/2018/03/24/data-laced-with-history/
[2] https://fluidframework.com/
[3] https://www.npmjs.com/package/sorted-btree