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I'm trying to run a NetLogo (a java simulation framework) simulation on a cluster as part of a large experiment. I was surprised at the seemingly massive memory requirement of a (relatively) simple simulation. On the cluster it throws "java.lang.OutOfMemoryError: Java heap space" exceptions for anything less than "-Xmx2500M" heapsizes. A single execution takes 5 hours to run. I ran the same experiment on both my Macs (iMac and MacBook Pro), and they executed in less than one hour, with "-Xmx1024" giving no errors. The cluster jobs require "-XX:MaxPermSize=250M" whereas on my Macs no increase above default is required. I ran the same code, the same inputs, using the exact same jars in all cases. 64 bit JVMs are used in each case (and as far as I know these are pretty similar): <on the cluster> $ java -version java version "1.6.0_26" Java(TM) SE Runtime Environment (build 1.6.0_26-b03) Java HotSpot(TM) 64-Bit Server VM (build 20.1-b02, mixed mode) <on my macs> $ java -version java version "1.6.0_31" Java(TM) SE Runtime Environment (build 1.6.0_31-b04-415-10M3646) Java HotSpot(TM) 64-Bit Server VM (build 20.6-b01-415, mixed mode) And I am running Client JVM in all cases (was initially using Server on cluster, switching to client made no difference). I have tried executing on the cluster with java 7, same huge memory and execution time issues. I am completely perplexed, no one I have spoken to can explain this. Has anyone out there come across this before? Any help greatly appreciated!

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