Asynchrony is not concurrency

https://lamport.azurewebsites.net/pubs/time-clocks.pdf

Example: python allows concurrency but not parallelism. Well not really though, because there are lots of examples of parallelism in python. Numpy both releases the GIL and internally uses open-mp and other strategies to parallelize work. There are a thousand other examples, far too many nuances and examples to cover here, which is my point.

Example: gambit/mit-scheme allows parallelism via parallel execution. Well, kindof, but really it's more like python's multiprocess library pooling where it forks and then marshals the results back.

Besides this, often parallel execution is just a way to manage concurrent calls. Using threads to do http requests is a simple example, while the threads are able to execute in parallel (depending on a lot of details) they don't, they spend almost 100% of their time blocking on some socket.read() call. So is this parallelism or concurrency? It's what it is, it's threads mostly blocking on system calls, parallelism vs concurrency gives literally no insights or information here because it's a pointless distinction in practice.

What about using async calls to execute processes? Is that concurrency or parallelism? It's using concurrency to allow parallel work to be done. Again, it's both but not really and you just need to talk about it directly and not try to simplify it via some broken dichotomy that isn't even a dichotomy.

You really have to get into more details here, concurrency vs parallelism is the wrong way to think about it, doesn't cover the things that are actually important in an implementation, and is generally quoted by people who are trying to avoid details or seem smart in some online debate rather than genuinely problem solving.

I can do a lot of things asynchronously. Like, I'm running the dishwasher AND the washing machine for laundry at the same time. I consider those things not occurring at "the same time" as they're independent of one another. If I stood and watched one finish before starting the other, they'd be a kind of synchronous situation.

But, I also "don't care". I think of things being organized concurrently by the fact that I've got an outermost orchestration of asynchronous tasks. There's a kind of governance of independent processes, and my outermost thread is what turns the asynchronous into the concurrent.

Put another way. I don't give a hoot what's going on with your appliances in your house. In a sense they're not synchronized with my schedule, so they're asynchronous, but not so much "concurrent".

So I think of "concurrency" as "organized asynchronous processes".

Does that make sense?

Ah, also neither asynchronous nor concurrent mean they're happening at the same time... That's parallelism, and not the same thing as either one.

Ok, now I'll read the article lol