Visualization Tool for Development of Communication Algorithms and a Case Study Using the K Computer
Syunji Yazaki, Ryohei H. Suzuki, Fumiyoshi Shoji, Kenichi Miura, Hiroaki Ishihata · 2015
In this paper, we introduce our visualization tool, the Communication Log Viewer (CLV), that assists the development of collective communication algorithms. We also present visualization results as a case study. CLV visualizes information regarding node events and network statistics in linked multiple views. CLV also has a function for analyzing the results obtained from network simulators and actual machines in the same framework, which is useful when developers repeatedly test their algorithms on a simulator and an actual system. For a case study, we visually evaluated two all-to-all algorithms on the full system of the K computer that has 82,944 nodes. As a result, we confirmed that an optimized all-to-all algorithm implemented for the K computer performed better than an all-to-all implemented in Open MPI. We also confirmed that the barrier operation used in the K computer’s Message Passing Interface (MPI) functions keep link utilization high. However, there is also a trade-off between the number of barriers and link utilization. Keywords–Visualization; Mesh/Torus network; All-to-all