Advice using PROXY_TO_PTHREAD

[Brian Gavin]

Hi,

I am looking at using PROXY_TO_PTHREAD to thread.  I was hoping for some advice using it.   I use webgl so it looks like I need to use -s OFFSCREENCANVAS_SUPPORT=1?

How should I convert EM_ASM(...) code?   How I use Emind functions?   Is there a way to find the webworker that holds the wasm thread?

Thanks

Brian Gavin

[Jukka Jylänki]

You will either need to use OFFSCREENCANVAS_SUPPORT (preferred), or
OFFSCREEN_FRAMEBUFFER, which is a fallback mode that can be used that
does not require OffscreenCanvas support. Both can be used at the same
time, which enables targeting OffscreenCanvas when available, and
falling back to the emulated offscreen framebuffer mode when not
available.

For EM_ASM(), you need to analyze each and decide whether you want to
call those EM_ASM()s in the calling thread, or on the main thread. If
on the calling thread, then keep using EM_ASM().

If the block should be executed on the main thread, then you have two
choices: either execute it synchronously with MAIN_THREAD_EM_ASM(), or
with MAIN_THREAD_EM_ASM_INT() or MAIN_THREAD_EM_ASM_DOUBLE() if you
need a return value back. This can be slow and cause a perf impact. If
you do not need a synchronous result back, and you have taken care of
thread synchronization via other means (or synchronization does not
particularly matter), you can instead execute with
MAIN_THREAD_ASYNC_EM_ASM(), which will asynchronously queue the call
to the main thread, letting the calling thread immediately proceed
with resuming code execution.

I have not looked at Embind in a while to know if there are issues
there. Most likely all the function calls are done in the calling
thread, so if you need to route calls to main thread, you'll need to
implement that yourself.

To get the JS Worker object, get the pthread pointer (e.g. via
pthread_self()), then loop through the global JS variable
"PThread.runningWorkers", and find the worker object with a matching
"worker.pthread" value. The worker that matches will be the Web Worker
object corresponding to that pthread.

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[Brian Gavin]

Thanks jj for the advice.

Brian Gavin