Filed, now that I understand shared a little better and you reminded
me about this.
On 9/5/2010 3:08 AM, Andrei Alexandrescu wrote:
I think both are wrong for different reasons. Did you file them to
Bugzilla already?
Andrei
On 07/31/2010 11:45 PM, David Simcha wrote:
Also, the following doesn't compile:
class Foo {
shared void bar() {}
}
void main() {
shared(void delegate()) d;
auto foo = new Foo;
d = &foo.bar;
}
Error: cannot implicitly convert expression (&foo.bar) of type void
delegate() to shared(void delegate())
But the following does:
class Foo {
void bar() {}
}
void main() {
shared(void delegate()) d;
auto foo = new Foo;
d = &foo.bar;
}
If these are just plain bugs, let me know and I'll file them in
Bugzilla, but right now I feel like they're more likely my lack of
understanding of shared.
On 7/31/2010 7:31 AM, Andrei Alexandrescu wrote:
Hello,
Here's a belated answer to your question (hectic times prevented me
from tending to non-urgent email).
I think a parallel library would be great to have as indeed phobos is
geared at general concurrency. Such a lib would also expose bugs and
weaknesses in our model and its implementation.
Andrei
Sent by shouting through my showerhead.
On May 30, 2010, at 12:54 PM, David Simcha <[email protected]
<mailto:[email protected]>> wrote:
I have a few questions/comments about the possible inclusion of a
library for parallelism in Phobos:
1. What is the status of std.concurrency? It's in the source tree,
but it's not in the documentation or the changelogs. It appears to
have been checked in quietly ~3 months ago, and I just noticed now.
2. From reading the description of std.concurrency in TDPL it seemed
more geared toward concurrency (i.e. making stuff appear to be
happening simultaneously, useful for things like GUIs and servers)
rather than parallelism (i.e. the use of multiple CPU cores to
increase throughput, useful for things like scientific computing and
video encoding). It seems fairly difficult (though I haven't tried
yet) to write code that's designed for pull-out-all-stops maximal
performance on a multicore machine, especially since immutability is
somewhat of a straight jacket. I find implicit sharing and the use
of small synchronized blocks or atomic ops to be very useful in
writing parallel programs.
3. Most code where parallelism, as opposed to concurrency, is the
goal (at least most that I write) is parallelized in one or two
small, performance critical sections, and the rest is written
serially. Therefore, it's easy to reason about things and safety
isn't as important as the case of concurrency-oriented multithreading
over large sections of code.
4. I've been eating my own dogfood for awhile on my ParallelFuture
library. (http://cis.jhu.edu/~dsimcha/parallelFuture.html
<http://cis.jhu.edu/%7Edsimcha/parallelFuture.html>;
http://dsource.org/projects/scrapple/browser/trunk/parallelFuture/parallelFuture.d)
It's geared toward throughput-oriented parallelism on multicore
machines, not concurrency for GUIs, servers, etc. and is higher level
than std.concurrency. Is there any interest in including something
like this in Phobos? If so, would we try to make it fit into the
explicit-sharing-only model, or treat it as an alternative method of
multithreading geared towards pull-out-all-stops parallelism on
multicore computers?
One last note: Walter claimed a while back on the NG that
Parallelfuture doesn't compile. I use it regularly and it compiles
for me. Walter, can you please point out what the issue was?
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