I'm experimenting with the -parallel flag and finding that using 2 parallel threads is slower than a single thread, and using 3 is slower still. I have 4 cores on my machine, FYI.
$ time java -jar HeatBugs.jar -for 10000 -repeat 4 -parallel 1 -quiet
real 0m4.514s
user 0m6.098s
sys 0m0.749s
$ time java -jar HeatBugs.jar -for 10000 -repeat 4 -parallel 2 -quiet
real 0m4.799s
user 0m12.019s
sys 0m1.437s
$ time java -jar HeatBugs.jar -for 10000 -repeat 4 -parallel 3 -quiet
real 0m5.972s
user 0m21.190s
sys 0m2.933s
What's the deal here?
Joey