NOTE: Most users will not need to go through these steps as these settings will be configured when using the packaged installation script as described on this page: Building the Flow Solver
Other Compile Time Options
The ARCH compile variable in the make file is used to specify conditional compilation for various machine architectures.
In general, ARCH can be set to several machine types (i.e. INTEL, SGI, IBM, T3E, SV1 etc..) with the default being ARCH = OTHER, which is used for any types other than those listed explicitly.
On CRAY machines, the appropriate ARCH setting also results in the input/output routines reading and writing IEEE standard unformatted fortran files which are compatible with other UNIX workstations and PCs.
The VEC variable enables (VEC=VEC_ON) or disables (VEC=VEC_OFF) vectorization. Performance will suffer if the appropriate setting is not used for the target machine architecture.
For most machines, VEC=VEC_OFF is employed, except for CRAY vector machines which requires VEC=VEC_ON
Two discretizations, one employing scalar artificial dissipation, the other matrix artificial dissipation (i.e. an upwind scheme) can be selected at compilation time. This is achieved through the use of the dflux_loop.h include file.
Scalar artificial dissipation is chosen by copying the dflux_scalar_loop.h file to dflux_loop.h and recompiling the entire source code.
Matrix artificial dissipation is chosen by copying the dflux_matrix_loop.h file to dflux_loop.h and recompiling the entire source code.
Matrix dissipation, which is equivalent to an upwind scheme, requires slightly more cpu time per iteration, but produces more accurate results on an equivalent grid. This is the preferred option. In cases where robustness is problematic, reverting to the scalar dissipation case may prove beneficial.
The values of the dissipation coefficients (VIS1, VIS2) should remain unaffected by the above choice of discretizations.