# Environment Variables

OptiStruct typically tries to avoid the use of environment variables, and instead uses either the defaults file or command line arguments, if possible.

• Parallel OptiStruct runs may require control parameters using environment variables. These are not listed in the OptiStruct documentation (refer to the corresponding MPI package documentation for further information).
• Typical system environment variables are used by OptiStruct when necessary: PATH, LD_LIBRARY_PATH, LDPATH.
• The OptiStruct Licensing system requires ALTAIR_LICENSE_PATH, RADFLEX_PATH.
• The use of third-party solvers requires specific environment variables: AMLS_EXE.
• Compute Console (ACC) uses and expects the following variables to be set: ALTAIR_HOME, ALTAIR_LICENSE_PATH, HW_MSG_HELP, ALTAIR_WISH_EXEC, and so on. These typically are automatically set at the installation and do not require modification.
• Compute Console (ACC) (and OptiStruct run script) provides automatic licensing and system related environment variables: PATH, LD_LIBRARY_PATH, LDPATH, RADFLEX_PATH, PYTHONHOME, and so on. It will also try to provide suitable default values for MPI related variables, if nothing is specified. However, it will not override values existing when it is invoked. Additionally, when changing various PATH environment variables, it will add to the end of existing values, so your preferences will not be overwritten.

## Environment Variables and Descriptions

The following environment variable is optional and may be set on either Unix or PC platforms; however, the preferred way is to define them using the Configuration File.
OS_TMP_DIR = path
path
Path name to directory for scratch file storage.
(Default = directory where the solver is started - can be overwritten by the definition in the script or input deck).
The following environment variable is optional and may only be set on Unix platforms; however, the preferred way is to define this using the Configuration File.
DOS_DRIVE_$= path This environment variable allows drive letters to be assigned to Unix paths. This facilitates copying files which contain INCLUDE, TMPDIR, INFILE or OUTFILE definitions containing drive letters from PC to Unix on hybrid networks. $
Drive letter to be defined (case sensitive).
path
Unix path with which you want to replace the drive letter.
Note: After such expansion, the paths are always interpreted as if there were a '\' immediately after the drive letter in the original PC path.

## Optional Environment Variable

OS_SCRATCH_EXT = <3-character-string>
The 3-character-string that specifies the new extension of the scratch file.

## SPMD Environment Variables

When environment variables not specific for the MPI environment are detected, Compute Console (ACC) or the OptiStruct script will provide default values, which are adequate in typical situations. For better performance tuning, you may try different values dependent on the hardware and MPI software used. For Intel MPI runs, the following defaults are applied, if none of the four environment variables are set by you:
I_MPI_PIN_DOMAIN = auto
KMP_AFFINITY is not set
I_MPI_AUTH_METHOD = delegate