> My algorithms work perfectly fine for small inputs, > but when I go for amazon machine and want to compute larger inputs, my code > hangs on forever
There is one more thing that I'd check (that I already told [1]). You reported a HPPC bug once but that involved a load factor of 1 on maps. This was a bug and I fixed it but a load factor of 1 is *purely theoretical* on hash maps using open (or linear) addressing. A full map effectively means the number of collisions and empty-slot searches goes sky-high so the effect you're observing (works on small inputs, "hangs" on large inputs) is exactly what this may be -- searching for empty slots on nearly full maps will take a long time with large inputs. In practice "long" here means endless if you have loops that try to get or put something in a nearly-full map. Dawid [1] https://groups.google.com/d/msg/java-high-performance-primitive-collections/bsTqQRi9nCQ/kqKUiIBFrFYJ
