Thread

1. criddell · 1790278663 · focus · HN ↗

   This review seems to equate parallelism and concurrency as the same thing and they are not.

   As I understand it, the parallelism is about task execution and concurrency is about task structure. Or, as Rob Pike said:

   "Concurrency is about dealing with lots of things at once. Parallelism is about doing lots of things at once."

   He said that in his Concurrency is not Parallelism talk.

   1. afdbcreid · 1790313148 · focus · HN ↗

      Parallelism without concurrency is useless, and concurrency without parallelism is usually cooperative and does not have the same challenges. So in essence, the title is correct.

      1. gpderetta · 1790325826 · focus · HN ↗

         > concurrency without parallelism is usually cooperative

         preemptive concurrency is almost as old as interactive computers. Until fairly recently, most computers were single core, but you wouldn't have wanted to use a cooperatively scheduled OS [1], especially on a multiuser machine.

         [1] yes, in the '80s some popular microcomputer OSs were single threaded (DOS) or cooperatively scheduled (classic macos and 16bit windows), but even then preemptive OSs were available (amigados).

         1. afdbcreid · 1790328422 · focus · HN ↗

            Right, I forgot about multithreading on one core.

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