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You have just repeated the nonsense I was talking about. The claim you repeat is meaningless. A program is either parallel / concurrent or not. The situation

You have just repeated the nonsense I was talking about. The claim you repeat is meaningless. A program is either parallel / concurrent or not. The situation you describe (when there's a single processor core) isn't parallel or concurrent. In some sense, it emulates concurrent / parallel execution because it imitates the unpredictable ordering of code execution, which sure has its uses... but the whole point of dealing with this unpredictable ordering is that we actually want parallelism / concurrency. The emulation on its own is worthless.

vore 3y ago
No it's not? How do you characterize running two programs on a single core without calling it concurrent but not parallel? There is a clear distinction between logical multitasking and physical multitasking that I think is useful to taxonomize.
stoniejohnson 3y ago
bruh your OS scheduler wants a word with you
preseinger 3y ago
a program (as written) is either concurrent or not, a program (as executed) is either parallel or not a program which is not written as concurrent can never be executed as parallel a program which is written as concurrent can be executed as parallel, or not > The situation you describe (when there's a single processor core) isn't parallel or concurrent. a program running on a single core can never be parallel, but it can be concurrent concurrent is a logical property, parallel is a physical property
- wizofaus 3y ago
  "a program which is not written as concurrent can never be executed as parallel" Unless of course you're running multiple independent instances of it, each with different parameters, which I gather is a pretty common way of running long running CPU- intensive operations on large data sets. Presumably there's often some final separate step that may be needed to combine the results once they're all finished, which if run manually obviates any concurrency concerns at the software level.
  - preseinger 3y ago
    in which case that program is being executed N times, so none of this applies ("a program [as executed]" is a single instance (process) of a binary)
chlorion 3y ago
Yes, concurrency on a single core CPU is simply not possible. That's why multitasking OS's didn't exist until multicore CPUs became a thing. If only these "Gophers" knew anything about computing history!
- ascar 3y ago
  So before 2001 your OS didn't have a scheduler and was incapable of handling more than one process at the same time? The user interface was simply hanging when you told your CPU to do something?
  - chlorion 3y ago
    That was the point I was attempting to get across. Single core computers multitask fine, which proves that concurrency is not the same thing as parallelism. Even in modern times, we have something like the first generation raspberry pi zero, it has a single ARM core, and it multitasks fine.
astrange 3y ago
Your "single core" computer contains a lot of other concurrently operating hardware like storage and network cards.

vore 3y ago

No it's not? How do you characterize running two programs on a single core without calling it concurrent but not parallel? There is a clear distinction between logical multitasking and physical multitasking that I think is useful to taxonomize.

stoniejohnson 3y ago

bruh your OS scheduler wants a word with you

preseinger 3y ago

a program (as written) is either concurrent or not, a program (as executed) is either parallel or not a program which is not written as concurrent can never be executed as parallel a program which is written as concurrent can be executed as parallel, or not > The situation you describe (when there's a single processor core) isn't parallel or concurrent. a program running on a single core can never be parallel, but it can be concurrent concurrent is a logical property, parallel is a physical property

wizofaus 3y ago
"a program which is not written as concurrent can never be executed as parallel" Unless of course you're running multiple independent instances of it, each with different parameters, which I gather is a pretty common way of running long running CPU- intensive operations on large data sets. Presumably there's often some final separate step that may be needed to combine the results once they're all finished, which if run manually obviates any concurrency concerns at the software level.
- preseinger 3y ago
  in which case that program is being executed N times, so none of this applies ("a program [as executed]" is a single instance (process) of a binary)

chlorion 3y ago

Yes, concurrency on a single core CPU is simply not possible. That's why multitasking OS's didn't exist until multicore CPUs became a thing. If only these "Gophers" knew anything about computing history!

ascar 3y ago
So before 2001 your OS didn't have a scheduler and was incapable of handling more than one process at the same time? The user interface was simply hanging when you told your CPU to do something?
- chlorion 3y ago
  That was the point I was attempting to get across. Single core computers multitask fine, which proves that concurrency is not the same thing as parallelism. Even in modern times, we have something like the first generation raspberry pi zero, it has a single ARM core, and it multitasks fine.

astrange 3y ago

Your "single core" computer contains a lot of other concurrently operating hardware like storage and network cards.