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How to Think about Parallel Programming: Not! [video] (2021)

21 points| caned | 8 months ago |infoq.com

23 comments

order

fifilura|8 months ago

Disclaimer: at work so I didn't watch the video.

For loops are the "goto":s of the parallel programming era.

Ditch them and the rest can be handled by the programming language abstraction.

Why? Because they 1. Enforce order of execution and 2. Allow breaking computation after a certain number of iterations.

bee_rider|8 months ago

I’ve always been surprised that we don’t have a really widely supported construct in programming that is like a for loop, but with no dependency allowed between iterations. It would be convenient for stuff like multi-core parallelism… and also for stuff like out of order execution!

Not sure how “break” would be interpreted in this context. Maybe it should make the program crash, or it could be equivalent to “continue” (in the programming model, all of the iterations would be happening in parallel anyway).

I vaguely feel like “for” would actually have been the best English word for this construct, if we stripped out the existing programming context. I mean, if somebody post gives you instructions like:

For each postcard, sign your name and put it in an envelope

You don’t expect there to be any non-trivial dependencies between iterations, right? Although, we don’t often give each other complex programs in English, so maybe the opportunity for non-trivial dependencies just doesn’t really arise anyway…

In math, usually when you encounter “for,” it is being applied to a whole set of things without any loop dependency implied (for all x in X, x has some property). But maybe that’s just an artifact of there being less of a procedural bias in math…