Re: [Algorithms] General purpose task parallel threading approach

[Matteo F. <ma...@ci...>]

Jon Watte <jw...@gm...> writes:

> Storing stacks for each task, and allowing arbitrary synchronous waits
> between tasks is simply not going to scale to many-core machines IMO,
> so wanting to do that is like wanting to not scale.

It may be true that allowing arbitrary synchronous waits between tasks
does not scale.  However, you can allow arbitrary fork-join Cilk-style
waits in a way that does indeed scale.  (I have used Cilk on up to 256
processors in shared-memory configuration, and up to 1824 processors in
a distributed-memory configuration without any particular problems.)

For this to work, however, you must implement the stack as a ``cactus
stack'' rather than as a collection of standard linear (contiguous)
stacks.  This is hard to do in a library---you really need compiler
support.

Regards,
Matteo Frigo