The SUN workstation on which is running ALADIN-BG came to the solid age of 5 years during this summer. It is engaged not only with running the operational suite of ALADIN-BG, but also running the wind-wave model and some special applications which create files in accordance with end-users requirements and so on. In fact we reached the limit of workstation capacity with respect of running time of the operational applications. That was the main reason to start experiments to run ALADIN on another platform.
The target machine was a Linux PC with two processors INTEL XEON, of 2.4 GHz clock-rate each, 1GB memory and 100 GB disk storage. The software packages used were:
The corresponding data for the workstation are : SUN Ultra-60, with processor clock-rate at 360 MHz, 256 MB memory and 60 GB disk storage, FUJITSU FORTRAN and C compilers, Operating System SOLARIS 9.
There were no significant problems to port the code of the model, apart from the appropriate modifications to the timing routines and the inclusion of some "ifdef"-s in C routines from the auxiliary library. There were no significant differences in spectral norms running the model on a single processor on PC and on workstation, which shows that the porting was done correctly.
MPICH was configured and built with shared-memory device and romio, using the FORTRAN90 compiler for F90 and F77, and pgCC (Portland Group C compiler) for C. The compilation of the code was done using the name of compilers used by MPICH. The values of FORTRAN, C and pre-processor flags in the makefiles are given below :
The tests contained several runs of the model on a single processor and on two processors, using different initial conditions. In general on single processor the execution time on PC was from 2.54 to 2.9 times better than on the SUN workstation. During the runs using two processors the scalability was from 1.78 to 1.93 related to single-processor runs. It should be outlined, that the scalability is growing with the percentage of work of the physics package. Some wall clock timing is given below :
Finally one can say that the Linux PC runs the model up to five times faster than the workstation. The conclusion might look like that : the multiprocessor Linux PCs may be a cheap solution for running the ALADIN model and related applications, and might be able to ensure the possibility for running of the up-to-date cycles of the model as well as to increase the number of levels and the size of the integration domain.