Memory Question

[Dan K]

Hi All,

I have two quick questions about memory allocation.

1. Is there harm in allocating more memory per processor core than the core contains? Will that slow down the program?
2. If my computer has multiple cores, will NWChem automatically use all of them? Or can it only use a single core? 

Much obliged,
Dan

[jeff.science]

From the perspective of "memory stack X heap Y global Z", you should limit X+Y to the ~half the memory per core.  You can set Z to anything, because it will be allocated on demand from the heap (at least in all of the GA back-ends I have inspected).  In contrast, the stack+heap is allocated at initialization.  If you request more than is feasible, NWChem is likely to crash.

Jeff

[Dan K]

Thanks very much, it's been running much more smoothly.