Ask HN: Some examples of parallel but not concurrent processing

2 points by zhirzh 8 years ago | 1 comment

Lately I've been studying the different async workflows and the most confusing bit (so far) is the difference between concurrent execution and parallel execution.

I have examples for concurrent-not-parallel, like single threaded processes or a multi-threaded program on a single thread processor.

What I cannot find are examples of scenarios where the execution is parallel, but not concurrent. TBH, it seems impossible (so far).

Wikipedia did give me one - Bit-level parallelism[1]. But that topic is a bit out of reach for me (again, so far).

Can anyone give me a more simple parallel-not-concurrent execution scenario?

[1]: https://en.wikipedia.org/wiki/Bit-level_parallelism

jjaredsimpson 8 years ago |

Vector addition in floating point registers is parallel but not concurrent.

Parallel means division of a task into separate parts which execute at the same instant in time.

Concurrent means separate task with overlapping lifetimes.

Parallel is contrasted with single threads of execution. And concurrent should be contrasted with serialization of task lifetimes.