`burn-train` in the browser

[AlexErrant]

Feature description

I'd like to run burn-train in the browser. ndarray and the train-minimal feature is sufficient.

Feature motivation

I'm building https://github.com/AlexErrant/fsrs-wasm/ which is basically https://github.com/open-spaced-repetition/fsrs-rs/ ported to the browser. In particular, I'm interested in training FSRS.

For now, performance is not a goal. I may revisit this later if it proves to be an issue. Right now my dataset is on the order of ~100k FSRSReviews, which is two u32s. (We'll see if ndarray is enough to train on that in a reasonable amount of time - if not I may have a second go at wgpu.)

Suggest a Solution

To be clear, I am interested in implementing this. However, this would be my first non-trivial contribution to this project, and I'm seeking feedback on architecting this feature.

Would burn accept a PR adding browser support to burn-train? I'm currently interested in augmenting burn-train, not creating a new crate. I'll be adding a new feature, browser, that will switch between different implementations of invokers of std::thread::spawn, std::fs, and possibly others. These may include (but are not limited to) FileCheckpointer, EventStoreClient, AsyncCheckpointer, AsyncLogger, and Worker.

Where possible, I will continue using std; targeting no_std is not a goal. My understanding is that for targeting the browser, no_std is sufficient, but not necessary. For example, this blog states that std::sync::mpsc may be used for communicating between web workers.

Preventing the code from becoming virally async is a goal. Asyncify may be used as a last resort.

As a first step, I plan on converting EventStoreClient to conditionally use a web worker, upon which I'll open a draft PR. I plan on trying out the above blog's spawn implementation. I'm not 100% on it since... well frankly the example code doesn't compile... but I thought I should open the issue and ensure that my goals align with this project's before I go too deep.

[nathanielsimard]

I believe it's a valuable feature if we aim to minimize the use of 'async' wherever possible, even in the browser. So, if you believe a solution can be developed without relying on async calls, then please pursue it, starting with a reasonably small pull request.