Output of memory needed and available 1

[meshparts]

Hi,

I would like to know, if my model needs more then the available RAM. When I look at the output text of a modal analysis, i see a lot of information about memory available or needed:

EST. OF MEMORY NEEDED            =  104 (MB)
MEMORY AVAILABLE FOR EIGENSOLVER =  179 (MB)

MEMORY TO PERFORM EIGENEXTRACTION: using opt Min core
 MIN. TO COMPLETE VALUE INPUT = 37 (MB)
 MIN. FOR PART IN-CORE AND OUT-OF-CORE = 58 (MB)
 MIN. FOR IN-CORE = 0.0 (MB)
 RECOM. FOR PART IN-CORE AND OUT-OF-CORE = 86 (MB)
 RECOM. FOR IN-CORE = 0.0 (MB)

My question is: what is the meaning of all these informations and how important they are?

Thanks!

Alex

 

[cbrn]

Hi,

as per the information you provide, this model would fit into memory entirely (=entirely "in-core"): 179>104.

If the avail RAM memory was less than the in-core required, then the program would have to use disk mem as a surrogate (="out-of-core"). However, even like this, some RAM memory is still required: in the example given by your file, 37 MB are needed only to pre-process the matrices, 58 MB are the minimum RAM needed in order to allow out-of-core operation, and 86 MB are the RAM needed to ensure "decent" performance in "out-of-core". The min and recommended RAM for in-core are both showing zero because the model already fits into RAM entirely.

Regards

 

[meshparts]

Thank you very much for your detailed answer cbrn!

Just one more question:

Why ist the MEMORY AVAILABLE FOR EIGENSOLVER so small?? My computer should have more to offer, sice it has 2 gig of RAM.

Regards,
Alex

 

[cbrn]

Hi,
eh eh, this is the mystery of Windows !...
Seriously, probably the mem setting is unbalanced in favour of the database space, so that there is no more room (or very few) for the solver. This happens if your "solid" model is complex and if you've performed a lot of database operations (modeling, booleans, etc) in the session. In fact, there are several keys you can set in order to "govern" how the memory will be allocated. The main is the "-m" switch in the launch command line (or the Ansys Launcher), but it is not recommended any more since normally Ansys does a good job by automatically expanding the mem up to what the operating system can give. If you run very huge models in a 32 bits environment, you may know that Windows allocates max 2GB to the applications, unless the "3GB" key is set in the boot.ini file. There are also some strange limitations with the "-m" key. It happened to me to be able to run a 2.1 GB solver job only by setting
BCSOPTION,,INCORE,2200,,,
before launching the solution (a bit more than 2200 was the amount of MB that the Task Manager showed as free).
Also note that Workbench is smarter in allocating the memory: I ran a 2.2 GB solver job without difficulties and without setting anything particular (in certain phases, the available RAM dropped to something like 1200 kB, so I'm sure all my 3 GB were in use !!!)

Regards