A short side note.
I looked into "The Joy of Clojure" and there is a nice diagram on page
251 about the difference if you use send and send-off to send actions to
an agent.
The intersting on send is, that the agent queues the send actions if you
use send. If you use send-off the agent does not stores the action into
a queue.
Could be, that in the case of pmap a similiar effect takes place and the
agent has less actions which does not need to be stored in his queue.
This can be the reason for the lesser memory consuption.
And yes on page 248 in "The Joy of Clojure" there is written:
"Agents are integrated with STM transactions, <...>".
If I understand this correct, then Agents are under the "control" of the
STM or at least are influenced by the STM.
Am 03.04.2012 18:48, schrieb Jim - FooBar();:
Hmmm....interesting thoughts...
I was under the impression that that agents are asynchronous and thus
do not depend on the STM , which is only for co-ordinated change!
There is a dedicated Thread pool where agents are assigned separate
threads for their work.You seem to suggest otherwise...I guess i 'll
have to resort to my Clojure books...perhaps we could post a new
question with different title here on the group...I'm sure more
experienced people can answer that with not much time spent...
Bottom line is that unless i use pmap i run the risk of running out of
memory...presumably it's the same for you.
Jim
On 03/04/12 17:16, Marcus Lindner wrote:
Maybe the reason is the STM.
If I rmember it correctly, then agents and refs are controlled by
Clojures STM mechanic. Eventuelly the us of map increase the work for
the STM and so it needs more time to schedule all the agent calls and
this result in a higher memory usage.
When you use pmap the calls are working in parallel and the STM might
have less agents calls to schedule and this might reduce the stress.
On the otherside, the work the agents have do to is not so hard and
the STM might shine in comparison to pmap or other parallel calls if
there is much more work to do.
But these are only guesses...
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