Performance of MC2 and the ECMWF IFS forecast model on the Fujitsu VPP700 and NEC SX-4M

The NEC SX-4M cluster and Fujitsu VPP700 supercomputers are both based on custom vector processors using low-power CMOS technology. Their basic architec-tures and programming models are however somewhat diierent. A multi-node SX-4M cluster contains up to 32 processors per shared memory node, with a maximum of 16 nodes connected via the proprietary NEC IXS bre channel crossbar network. A hybrid combination of inter-node MPI message-passing with intra-node multi-tasking or threads is possible. The Fujitsu VPP700 is a fully distributed-memory vector machine with a scalable crossbar interconnect which also supports MPI. The parallel performance of the MC2 model for high-resolution mesoscale forecasting over large domains and of the IFS RAPS 4.0 benchmark are presented for several diierent machine conngurations. These include an SX-4/32 with 8 GB main memory unit (MMU), an SX-4/32M cluster (SX-4/16, 8 GB MMU + SX-4/16, 4 GB MMU) and up to 80 PE's of the VPP700.