Comsol multiphysics

[hoangpd]

Hello everyone,
Does anybody use Comsol multiphysics here?
I am trying to model the electric double layer. If you have experience, please share with me.

[PerennialII]

yep, one of the foremost FE software packages our group is using nowadays (or well, the last 5-6 years think). What you've in mind?

[hoangpd]

Hi PerennialII and everyone in the forum,
Sorry for not getting back for so long 'cause I got the answer that I wanted. Now here's my new question. In Comsol, at the bottom corner on the right, there's a memory indicator. For example 145/172. What I know is that this is the virtual memory number. 145 is the current virtual memory usage, and 172 is the peak virtual memory usage.
The situation is that I often run out of memory, which I think is this kind of memory i.e. virtual memory. Is there anyway to tell Comsol to increase the allowed maximum memory?. My PC has 4MB of memory.
Thanks for your time.
Hoangpd

[PerennialII]

Hi hoangpd,

are you sure about those system specs ... 4 Mb? Increasing virtual memory otherwise (assuming you're running win) is something done by adjusting the settings & workings of the operating system (in win control panel -> system and from thereon). Comsol otherwise should just swallow everything available.

[hoangpd]

HI Perennial,
My RAM is 4GB instead of 4MB. It was a bad typo. Sorry!. Anyway, why is virtual memory being used when Comsol still has the physical memory to use? Or is Comsol that memory intensive that it uses all the physical memory the moment it runs?
Also, my operating system is 32bit if that helps you answer my question.
Hoangpd

[PerennialII]

If you're running windows it's probably easiest 1st to check the amount of virtual memory and increase it a somewhat if feasible (control panel -> system props -> advanced and virtual memory in there). If you're running linux or some related unix system you probably wouldn't have these issues at all :wink: (or well .... :biggrin: ). If that doesn't help, then the next thing could do is to start decreasing the amount of memory comsol is using to solve your model & problem (which means primarily solver parameters, and choosing as memory efficient solver as possible for the problem you're studying). Naturally, can try to modify the model trying to decrease the number of dofs and so on, but surely would be nice to find an another solution which would enable solving the model as is.

The memory "spill" to virtual memory likely has to do with the memory management of your OS (when talking win this is fairly common although have physical memory remaining). Also, could check if your system can allocate the whole 4 Gb (i.e. does it "show" at the OS, in win for example under system properties). In principle would think so, but sometimes other limitations come into play (like weird BIOS behavior).

[Link-]

I had solve this problem increasing the mesh size on the areas that are not of significance on the model. Also, maybe is due to the time step you are using, if it is a transient analysis.