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It’s used by frameworks Vue, SolidJS, Svelte, Ember, Angular, and there’s a few different implementations for React like Mobx and Jotai. There’s a few different algorithms for how to propagate changes and evaluate the DAG, I believe SolidJS2 uses a height-based algorithm similar to Incremental.
I’ve been fooling around with an implementation that uses an Int32Array arena to allocate nodes and link them together with linked lists without paying O(dependency edges) GC load: https://github.com/justjake/dalien-signals/tree/dalien-signa...
There are a few of these for Rust as well, Leptos is an example in UI frameworks, and Salsa is an example in general incremental computing, used in rust-analyzer.
Another way to look at this sort of thing is as a build system with automatically tracked dependencies. One such build system is tup, which instruments build jobs to detect what files they read to establish dependency relationships. Interesting reading from the author: https://gittup.org/tup/build_system_rules_and_algorithms.pdf, see also the classic Build Systems à la Carte https://www.microsoft.com/en-us/research/wp-content/uploads/...
But incremental computation isn’t exactly functional reactive programming. They are different domains in practice that often get thrown together because the problem they address can overlap. Incremental computation explicitly derives a function that can operate on deltas, FRP might just use damage and repair instead.
As the authors highlight: "Noria is not a UI framework at its core. Instead, it’s a platform for incremental computations.". But currently they happen to use it to optimize gui rendering in JetBrains Air IDE.
As far as I can tell, incremental the library aims to solve the problem of partially hydrating a computation graph when source data is altered. This approach is similar to the one pursued by (well designed) build systems and is common in the FP world. [2] This has many use cases and is very cool.
In addition, in the sphere of incremental computation, there exists Differential Dataflow, Timely Dataflow (adjacent), and DBSP. Systems like Feldera are built on DBSP. Materialize is lead by some DD guys.
Personally, I am pursuing an orthogonal approach specifically for the problem of financial data and financial workloads, There exists huge, very important problems to solve! [1]
[1] https://modolap.com
[2] Signals And Threads episode on the subject https://signalsandthreads.com/build-systems/
Redirect to a 2k USD stripe payment with no explanation when clicking on the main callout button is a pretty baller move.
Email me for details, pricing & installations, or your target use case, would love to talk. In addition, if you have any feedback.
ron at modolap dot com
Computer Science has evolved, and AFAICT this is not a graph approach, but things like differentiation are computationally expensive, and therefore you want to minimize the number of times you do it to as close to the theoretical minimum.
Edit: Related HN discussion https://news.ycombinator.com/item?id=36006737
https://calpaterson.com/bank-python.html
The best description about how it became a problem is one of the paragraphs.
"New starters take an exceptionally long time to get up to speed - and that's if they don't resign in fit of pique as soon as they see the special, mandatory, in-house IDE (as I nearly did). Even months in, new starters are still learning quite fundamental new things: there is a lot that is different."
I think it took me til I was there around two and a half years to fully comprehend it when I was working on it. Not much modern training til they figured out they had to teach it again that was better. The worst part is to make an UI around it coding it and it wasn't approved for new projects.
Libraries like React are pretty efficient with skipping work by using Virtual Dom, but constructing this vdom still takes time. Bonsai makes the vdom incremental and it is pretty fun to work with.
I built a desktop UI library with it by targeting (now unmaintained) Revery. It is using a much older version of Bonsai however: https://github.com/ozanvos/bonsai_revery
[0]: https://github.com/hoplon/javelin
I guess there's probably optimizations around change detection and stopping the propagation if there's no change (though observables can do that as well). The stabilize command also makes things interesting as a way to batch changes together before recomputing (but again, doable with observables too).
Is the delta primarily coming from introspection and automatically building the compute graph? Or is there something more fundamental that I'm missing?
The fundamental components here are laziness and weak connections between graph nodes. Node values are getting materialized only when you observe them, and the system is flexible for live structural changes.
Usually, you don't need to materialize the entire graph when you need to observe just some nodes. Additionally, you can halt computations at any point in time leaving the graph in semi-actualized state, make extra changes to the inputs, and continue materialization of the nodes of interest. The algorithm will sort out all changes for you.
Essentially, incremental computations is just a term covering these features. You can organize the same system in terms of observers and subscribers.
Perhaps, classical Excel spreadsheets is the best illustration of the idea. Also, see my article on the topic: https://medium.com/@eliah.lakhin/salsa-algorithm-explained-c...
However I'm not sure Excel is such a great illustration in that case, as it's neither lazy nor weakly connected; at least at the surface.
I distinctly remember being amazed that it would just iterate until it reached equilibrium (maybe we had to change some setting somewhere first though, I never really used Excel before or after that). I think you could change a value mid-iteration, and the grid would just continue on with the previously calculated cell values, instead of start over from scratch. That's basically "weakly connected", isn't it?
(anyway, the real challenge is to find a practical use for Excel's hidden fractal powers https://www.youtube.com/watch?v=b-Fa6HtvGtQ)
There's a really good talk from Ron Minsky here: https://www.janestreet.com/tech-talks/seven-implementations-...
Can help map out the landscape.
A naive observer approach will 1) compute that potentially exponential blow-up very inefficiently and 2) probably have "concurrency" issues. This library will be close to optimal and correct, even if you start dynamically changing the graph structure.
But yes, you can achieve the same thing with observers and other kinds of approaches. Most of them just a lot harder to get right while avoiding performance cliffs.
The closest thing to Electric (IMO) is SolidJS, but frontend only: https://www.solidjs.com/
You tag each computation nodes with a hash of its dependencies and some constant salt, that gives you an ID which identifies the results that the computation node would produce; before running it.
You can then use those IDs to index the computations results in a cache; whenever you query a computation results, as long as you update the IDs of each leaf of the computation graph, you will only re-compute the nodes that need to be updated
https://hn.algolia.com/?q=flow+based+programming+
Usually these kinds of systems either don't scale dynamically or have caching issues. The first example, a spreadsheet, is "easy" because there are a fixed amount of cells to track. A GUI can be a lot harder (imagine sub windows and sub-sub windows dynamically popping up and tracking some redundant and some unique "computations". Entities can appear and then be removed at random). Though the wording carefully says "constructing views" so maybe it doesn't handle dynamism
After they got caught most of their online posts/videos either got deleted, or locked so you could not comment on them.
I had hoped their front guy for ocaml, Ron Minsky had atleast made some sort of statement. Currently no ones know how deep that fraud went, but what we know ocaml was used in the fraud, damagine ocaml ecosystem too.
I do not understand what is the big deal with Increment. Is it more efficient because it is written in OCaml rather than C#?
Very satisfying to use when you manage to find a problem that is suited to this type of approach.