Performance difference for multi-thread and multi-process

It depends on how much the various threads or processes (I'll be using the collective term "tasks" for both of them) need to communicate, especially by sharing memory: that's easy, cheap and fast for threads, but not at all for processes, so, if a lot of it is going on, I bet processes' performance is not going to beat threads'.

Also, processes (esp. on Windows) are "heavier" to get started, so if a lot of "task starts" occur, again threads can easily beat processes in terms of performance.

Next, you can have CPUs with "hyperthreading", which can run (at least) two threads on a core very rapidly -- but, not processes (since the "hyperthreaded" threads cannot be using distinct address spaces) -- yet another case in which threads can win performance-wise.

If none of these considerations apply, then the race should be no better than a tie, anyway.

I'm not sure what the quote even means. It's very close to nonsense.

The primary thing that in-proc threads share is virtual memory address space.

I found this is true as well. but I think it has something to do with the scheduling. because if you run it long enough, the multi-processes is just as fast as multi-threads. that number is about 10 seconds. if the algorithm needs to be run for 10 seconds. the multi-processes is as fast as multi-thread. but if it only needs to be run for less than 1 second. multi-processes is much,much faster than multi-thread.