Marc Lehmann is in fact spot on and Chip is incorrect. There's no "politics" involved here. At least not on Marc's side.

Perl's "threads" are not threads in the generally accepted term, yes wikipedia does say "In computer science, a thread of execution is the smallest unit of processing that can be scheduled by an operating system."

But it also goes on to say

", but in most cases, a thread is contained inside a process."

Perl's implementation of "threads" is actually done using forking and there is *no* shared memory space. You're getting confused as what actually happens is *ALL* the data from the main process is copied across to the memory space of the "threads". They are processes and have their own memory space. Real threads execute inside the 1 process and share memory.

For interpreted languages there is what's called a GIL(Global Interpreter Lock) which is there to prevent non-thread safe code being shared with other kernel threads. Ruby and Python have a GIL and their threads are known as 'green threads' which are not kernel level but are after the GIL, but still share memory. They of course will not take advantage of multi-cores. On a side note you can get real kernel level threads with both Ruby and Python through jRuby and jPython, but nothing like that exists for Perl.

Perl's psuedo-threads will take advantage of multiple-cores because they are processes and they do NOT share memory. Marc knows his stuff. He wouldn't have been able to write Ev, AnyEvent, Coro to be as stable and fast as they are if he was lacking in such basic knowledge that even *I* know and I consider myself intermediate at best.

But, please don't take my word for it. Check perlthrtut. First paragraph.

"This tutorial describes the use of Perl interpreter threads (sometimes referred to as ithreads) that was first introduced in Perl 5.6.0. In this model, each thread runs in its own Perl interpreter, and any data sharing between threads must be explicit. The user-level interface for ithreads uses the threads class."

Notice the word 'explicit'. That means you have to, yourself share any data between 'threads'. This is the very purpose of threads::shared. Why would that module exist if Perl 'threads' shared memory as Chip Salzenberg and yourself claim?

In reply to Re^4: Why Coro? by binary
in thread Why Coro? by xiaoyafeng

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