User Area > Advice
How LUSAS uses PC memory
For V15.0 onwards the memory allocation settings
for Solver are much more automated and it is suggested to keep the default
settings.
Memory allocated to Solver array (NLPZ) sets aside memory for LUSAS to perform calculations in. It is set automatically ("dynamically"); the only time when it cannot be adjusted dynamically is during the reading of input data from a LUSAS
datafile. Therefore a large value of NLPZ
is required to use Solver on large problems.
The remaining space in physical memory can then be
allocated to Solver cache (NPGS) to help reduce the disk read/
write processes still further.
It may be that all the physical memory is allocated to the
Solver array (i.e. NLPZ*8 is greater than the physical
memory available) - in this case LUSAS will use
the PC virtual memory,
with a corresponding increase in solution time. A memory upgrade would make a
significant difference.
Memory allocated to Solver cache (NPGS) sets aside another area of memory
for LUSAS to store the answers to calculations which it may need to retrieve in
the short term. When the physical memory (RAM) available on your machine exceeds the memory
allocated to the Solver array (NLPZ), allocating RAM to a Solver cache avoids time wasted by writing and reading data to disk
unnecessarily.
However, when solving a large problem, the cache starts to take up space which NLPZ should be allowed to grab
dynamically and so it should be reduced.
Elements in group (MXELGP). In order to avoid unnecessary reading from the
disk, LUSAS gathers data for processing a number of elements in a group, rather
than one-by-one. MXELGP controls how many elements are in that
group. Increasing MXELGP would generally speed up solution, having the
most effect in dynamic and nonlinear analyses and the least effect in linear,
eigenvalue, harmonic response or spectral response analyses.
Advice on choosing memory
allocation values
More on how LUSAS
uses PC resources
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