On Tue, Apr 14, 2009 at 10:38:44PM -0400 or thereabouts, Vishvajit Singh wrote:
Is that actually what's going on in the Ants simulation? Clojureagents are something I haven't yet studied. I actually think agents run on a thread pool which has a number of threads equal to the number of processors.
Let's find out. Before I ran anything:
doug@eclipse:~$ ps -C java -L PID LWP TTY TIME CMD doug@eclipse:~$
So no java running. Let's fire up Clojure:
doug@eclipse:~/tp12/clojure$ ls .. clojure clojure_20090320.zip doug@eclipse:~/tp12/clojure$ /home/doug/java/jre1.6.0_13/bin/java -jar clojure.jar Clojure user=>
Let's see how many threads:
doug@eclipse:~$ ps -C java -L PID LWP TTY TIME CMD 31212 31212 pts/12 00:00:00 java 31212 31213 pts/12 00:00:01 java 31212 31214 pts/12 00:00:00 java 31212 31215 pts/12 00:00:00 java 31212 31216 pts/12 00:00:00 java 31212 31217 pts/12 00:00:00 java 31212 31218 pts/12 00:00:00 java 31212 31219 pts/12 00:00:00 java 31212 31220 pts/12 00:00:00 java doug@eclipse:~$ ps -C java -L|grep -v PID|wc -l 9
So 9 OS threads. Next I loaded the ants.clj file:
user=> (load-file "ants.clj") nil
Window pops up. Blank except for blue square in middle. CPU idle. Now we have 13 threads:
doug@eclipse:~$ ps -C java -L|grep -v PID|wc -l 13
Next I pasted in the following to the clojure REPL (it's from the bottom of the ants.clj file):
(def ants (setup)) (send-off animator animation) (dorun (map #(send-off % behave) ants)) (send-off evaporator evaporation)
Simulation starts. CPU pegged at 100%.
doug@eclipse:~$ ps -C java -L|grep -v PID|wc -l 89
89 OS threads. Wow that is even more than I figured.
Oh and I get it now... The ants crawl around searching for food and bring it back to the nest. ;)
If the objective is to simulate ant movement (as opposed to testing/benchmarking a thread implementation) you will have a more efficient and correct program if each ant is not implemented as its own thread. See The System described in my previous message for a solution.
So we might be criticising Clojure incorrectly here.
Actually I was never criticising Clojure (I don't know enough about it to do that). I was only discussing the trade-offs of different concurrency strategies.
Doug