Communication time models on fat-tree networks

With the growth of supercomputer´s scale, the communication time during executing is increasing. This phenomenon arouses the architecture researchers´ interests. In this paper, based on the fat-tree topology, which is widely used in Infiniband, we present an one-to-all broadcast communication time model. After classifying applications into two kinds, we establish the ideal model and the bandwidth-limited model on the exponential-capacity binary fat-trees for the two kinds of applications. Through analyzing the models, we get the curves which describe the relationship between the communication time and the processor number. The conclusions we get in this paper can help system designers make better system design.