| Note on the parallelization of transfer.f |
| ----------------------------------------- |
| |
| The file contains three major loops that update sparsely overlapped |
| mortar points. Parallelization of these loops requires atomic update |
| of memory references by mortar points. The first implementation |
| uses the ATOMIC directive to perform the job. However, in some systems |
| where atomic update of memory references is not available, the ATOMIC |
| directive could be implemented as a critical section, which would be |
| very expensive. An alternative approach is to use locks to guard |
| atomic updates. The second implementation scales reasonably well. |
| However, the overhead associated with calling lock routines deep |
| inside loop nests could be large. |
| |
| Two implementations: |
| - transfer_au.f: use ATOMIC directive for atomic updates |
| - transfer.f: use locks for atomic updates, as the default |
| |
| To use the first approach, one can either rename 'transfer_au.f' |
| to 'transfer.f' before compilation or use the suboption "UPDATE" |
| in make: |
| |
| % make CLASS=<class> UPDATE=au |
| |
| where <class> is one of [S,W,A,B,C,D]. |
