An overview of the BlueGene/L Supercomputer
Proceedings of the 2002 ACM/IEEE conference on Supercomputing
Architecture of the Component Collective Messaging Interface
Proceedings of the 15th European PVM/MPI Users' Group Meeting on Recent Advances in Parallel Virtual Machine and Message Passing Interface
Efficient high performance collective communication for the cell blade
Proceedings of the 23rd international conference on Supercomputing
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BlueGene/L is currently in the pole position on the Top500 list[4]. In its full configuration the system will leverage 65,536 compute nodes. Application scalability is a crucial issue for a system of such size. On BlueGene/L scalability is made possible through the efficient exploitation of special communication. The BlueGene/L system software provides its own optimized version for collective communication routines in addition to the general purpose MPICH2 implementation. The collective network is a natural platform for reduction operations due to its built-in arithmetic units. Unfortunately ALUs of the collective network can handle only fixed point operands. Therefore efficient exploitation of that network for the purpose of floating point reductions is a challenging task. In this paper we present our experiences with implementing an efficient collective network algorithm for Allreduce sums of floating point numbers.