Experiences Porting the Unified Model to the Ksr-1

There has been a convergence in computer architecture toward a distributed memory implementation of a shared memory user model. This has brought about the possibility of using a very large number of processors, on NWP applications, from the realm of research into reality. The simplicity of the shared memory model has meant that porting the very large Unified Model can be approached. However, although the shared memory model allows freedom of movement, the ability to achieve high performance can require very detailed analysis of many of the same issues faced by practicioners of distributed memory programming. This paper chronicles the process of porting the sequential version of the Unified Model to the KSR virtual shared memory supercomputer and outlines some of the issues which must be faced in obtaining a high performance implementation on the KSR.