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From: mitchalsup@aol.com (MitchAlsup1)
Newsgroups: comp.arch
Subject: Re: Is Parallel Programming Hard, And, If So, What Can You Do About
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Date: Wed, 21 May 2025 14:08:37 +0000
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On Wed, 21 May 2025 12:23:49 +0000, Stefan Monnier wrote:

>>>> Personally, I rarely use multi-threading, and when I do, it is usually
>>>> in
>>>> the form of using mutex locks over shared buffers.
>>>> You lock the mutex if needed to copy data from one thread to another; or
>>>> when doing a task that depends on the data being consistent.
>>>
>>> FWIW, I think these kinds of things usually fall in the scope of
>>> concurrency rather than parallelism.
>>
>> When I run 20-copies of a FEM CFD application, each uni-process::
>> am I running concurrently ?? or in parallel ?? or both ??
>
> Both: AFAIK the choice of how to divide&spread the data and the work is
> in the parallelism camp, while the choice of how to synchronize them is
> in the concurrency camp.

I think of it as Both--especially when affinity is not used and the
processes contend for CPUs randomly. Then process[a] and process[b]
are running simultaneously (different cores) they are parallel,
when running back-to-back on the same core they are concurrent.

>
>         Stefan