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Semicolony ELI5 · comic

Concurrency vs parallelism.

One barista juggling many orders by switching between them, versus several baristas making drinks at the same instant.

  1. Three orders, one of me.
    3 orders
    1

    Concurrency is one barista with many orders — dealing with all of them at once.

  2. Brew that, froth this, back again.
    brew froth
    2

    She starts one, steams milk for another while the first brews, switches between them fast.

  3. one worker, taking turns
    3

    Nothing happens at the same instant, yet everything keeps moving. That’s structure, not speed.

  4. On three — both pour!
    same instant!
    4

    Parallelism is two baristas each pouring a drink at the very same moment.

  5. four cores, four at once
    5

    That needs more hands. Add cores and CPU-heavy work genuinely finishes faster.

  6. You structure it; I’ll parallelise it.
    tasks core core runtime spreads
    6

    They combine: write concurrent tasks, and the runtime spreads them across cores for you.

One barista juggling many orders by switching, versus several baristas pouring at the same instant.
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