Thanks for clarifying that, Hans, and for pointing out the issue with
threads, IOhannes. One shouldn't be profligate with [pd~]s, strewing
them all about and expecting performance gains -- therefore, one [pd~]
per voice instance in a [polypoly] patch is probably not a good idea
until we have 64-core CPUs as a regular thing! :-).
However, with judicious use, [pd~] seems like it will allow Pd to scale
to future processor design, and that's a good thing.
Thanks again,
Phil
Hans-Christoph Steiner wrote:
[snip] As for manually managing pd~, I mean just manually creating as
many pd~ instances as you have cores.
.hc
IOhannes m zmoelnig wrote:
Phil Stone wrote:
Hi Hans,
Thanks for replying. I don't quite understand what you mean by
"manually manage". As far as I know, without something like [pd~],
there's no way to divide up and assign the Pd audio process to more
than one core. Half of the cores on a quad-core are therefore
useless to Pd (accounting for the fact that the graphical process
gets its own core).
the problem is, that poly-class objects are usually meant for _many_
objects (10+; i'm only repeating here what hans has already said).
[pd~] will fork a new thread for each of it's instances.
when doing multi-core processing (and this is really the only thing
pd~ is good for; e.g .it's not good if you want to have different
priorities / asynchronous processing), you usually don't want to
create more threads than you have cores.
why? performance reasons! if you create e.g. 1000 threads for 1000
instances of [doodle~] on a quad-core machine, your computer will
spend more time handling context-switches and the like (that is: the
overhead for managing the threads) than doing the actual job.
as a rule of thumb, the optimum number of threads is about the
number of cores you want to use.
since what is sold to customers as "multi-core" processors usually
does not involve more than 4 cores, the "best" (though probably not
the most comfortable) way to assign work to the cores from within Pd
is doing it "manually"
fmgasdr.#
IOhannes
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