08-15-2020, 07:02 PM
(08-15-2020, 02:11 PM)ceanwang Wrote: NASTRAN-95 may not has open core more than 14m, but it was designed to solve big case with small machine. It solves, but not in high performance. Especially not fully use today hardware's capacity.
Well, as long as NASTRAN-95 can load the model (such as by setting low values for DBMEM, hurting performance), it'll sure solve it. But that was not my point.
I was talking about how the 14 Mword (56 MB) OCMEM limit creates an upper limit for loadable model size (as in nº of elements).
There are several "model checking" subroutines (e.g. CIDCK) that that are run before other pre-solve steps (e.g. BANDIT) and they do operations which require allocating memory (e.g. some kinds of sorting). Since for some of these subroutines the amount of required memory grows monotonically with respect to how many of a card you have in the bulk data block, there is an upper limit to how many of that card you can have. And since that happens for rather common cards (e.g. GRID), the memory upper bound creates a model scale upper limit.
In practice, this means there are models used today that cannot, by any means, be run by NASTRAN-95, because the memory required for running basic pre-solving subroutines on them exceeds the upper bound on open core memory. In order to run them, you must either edit the model (make it coarser?) or change NASTRAN's code so either the involved subroutines use up less memory or there's more memory to begin with.