===== Java Issues =====

====Memory====

Java likes to allocate and/or reserve a **lot** of memory. Often (always?) it will allocate or reserve as much RAM as it sees available on the system. Why? Who knows, but it seems ridiculous.

To reign it in, specify a memory allocation as a command-line option when you compile java or run a java script/command.

=== Compiling with Memory Limits ===

To compile things with java on the cluster, one needs

javac -J-Xmx123M

=== Running with Memory Limits ===

To run,

java -Xmx123M

where mx123M is specifies a maximum heap size of 123 Mb. This needs to be less than the available RAM, so for a qlogin job default vmem=3G, you can probably go up to around 2800M at run time.

Compilation should require less RAM, we haven't found a lower limit but think 100M will suffice for many applications. You just have to give it something so it doesn't try to allocate a crazy high number by default.