RAMDISK - Run Control
The RAMDISK command is used to specify area in RAM allocated to store information which otherwise would be stored in scratch files on the hard drive.
RAMDISK = n
Argument |
Description |
|
N |
Size of virtual disk in MB. N=0 to disable RAMDISK |
Use of a virtual disk instead of physical files may speed up solutions by reducing wait time to access physical disk drives. Note that use of RAMDISK will reduce the amount of memory available for OptiStruct and for file buffering performed by the operating system (e.g. by Linux or Windows), and because of that it may not always reduce the wall clock time for the solution. The most impact can be observed on machines with very large physical memory (20GB or more) or when used to speed-up main solver scratch file access (see the SCRFMODE I/O Option).
RAMDISK is automatically protected for overflow, so it is fine to specify 200MB for RAMDISK when the total amount of scratch files will be larger than that.
OptiStruct automatically specifies RAMDISK for very small jobs, (less than 10,000 GRIDS). This can be disabled by specifying RAMDISK=0. Automatic RAMDISK is not allocated for fixed RAM jobs (the -fixlen command line option is used, see Options for Running OptiStruct.)
On 32-bit platforms, RAMDISK is allocated in the same area as the rest of the internal memory. Specifically, for 32-bit Windows it is allocated within about the 1.8GB available for OptiStruct. Therefore, use of this capability is only recommended for small jobs. There are two situations when it may be useful for 32-bit Windows OptiStruct (which is always limited to about 1.8GB RAM for the solver):
· When 32-bit Windows can be started with /3GB switch; then RAMDISK of up to about 850MB can be allocated in this area without limiting the size of memory available for the solver.
· When 32-bit version of OptiStruct can be started on 64-bit Windows; in this case, RAMDISK up to 1900MB can be allocated. Note that 32-bit computers (Linux or Windows) can have more than 4GB installed, but this extra memory is not available to a single run of OptiStruct.
Go To
Alphabetical List of I/O Options