Basic HTML version of Foils prepared 2 October 1995
| In MPI, this is a single call |
| CALL MPI_ALLREDUCE (TEST,TEST,1,MPI_REAL,MPI_MAX,comm) |
| Flag MPI_MAX specifies global maximum |
| The implementation is quite subtle and usually involves a logarithmic tree |
| There is a clever extension to get maximum in all processors in "same" time as that on one processor on hypercube and other architectures |