HFSS15: Specifying the Desired RAM Limit

The Desired RAM Limit setting requests a restriction on the amount of memory the MPS solver used in HFSS may allocate before it must stop solving on-core—solving processes entirely in memory—and start solving off-core. In off-core mode, the solver creates temporary solution files to which it spills, or shifts, data from memory, instead of relying on the operating system to start disk swapping. The location of these temporary files is specified in the General Options (Tools>Options>General Options, Project Options tab). The MPS solver is finely tuned at handling its own memory, and can optimize loading only those blocks of memory required for its immediate needs.

Using this option may help to keep the entire solver from being swapped out in the normal course of process management on your computer. This kind of control may be especially important when multiple solvers are running on the same machine. Of course, if the total memory requirement of all processes grows large enough, the operating system will be forced into disk swapping.

Regardless of this setting, processes are limited to 2GB of address space (3GB with appropriate operating system and boot settings) on 32 bit operating systems and 4TB of address space on 64 bit operating systems - no matter how much physical memory is installed. See Increasing PC RAM.

In case you receive an error message regarding insufficient memory on a 64-bit operating system, you may have reached a point where the sum of physical RAM plus available swap space exceeds the minimum amount of RAM needed by the off-core solver. Even for the off-core solver, the RAM usage cannot be made arbitrarily small. In that case you can consider increasing the swap space (the virtual memory) in the settings of your system.

To specify the Desired RAM Limit of the machine on which HFSS is installed:

1. Click Tools>Options HFSS Options.

2. Click the Solver tab.

3. Select Desired RAM Limit (MB).

4. Type a value for the amount of available memory, in megabytes, in the text box. This setting affects all HFSS projects for the current user and machine.