Specifying the Desired RAM Limit

The Desired RAM Limit setting requests a restriction on the amount of physical random access memory (RAM) the MPS solver used in Maxwell may use before it must stop solving on-core - solving processes entirely in RAM - and start solving off-core. In off-core mode, Maxwell creates temporary solution files to which it spills, or shifts, data from RAM, 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 > Directories). 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.

Note: The Iterative solver doesn't go off-core for efficiency reasons. Because the Desired RAM Limit (the soft memory limit) is used for off-core run, it is not appropriate for the iterative solver. Instead, the iterative solver uses the Maximum RAM Limit (the hard memory limit). Once the limit is exceeded, the iterative solver will issue an "Out of memory" error message.

Regardless of this setting, processes are limited to 4TB of address space on 64 bit operating systems - no matter how much physical memory is installed.

Note: Regardless of the Desired RAM Limit setting, if allocation fails, the Maxwell solver automatically switches to off-core mode.

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 Maxwell is installed, select Tools > Options > HPC and Analysis Options, then click Edit.

Refer to the HPC and Analysis Options section for more details.