Data Locality Aware Strategy for Two-Phase Collective I/O

This paper presents Locality-Aware Two-Phase (LATP) I/O, an optimization of the Two-Phase collective I/O technique from ROMIO, the most popular MPI-IO implementation. In order to increase the locality of the file accesses, LATP employs the Linear Assignment Problem (LAP) for finding an optimal dis- tribution of data to processes, an aspect that is not considered in the original tech- nique. This assignment is based on the local data that each process stores and has as main purpose the reduction of the number of communication involved in the I/O collective operation and, therefore, the improvement of the global execution time. Compared with Two-Phase I/O, LATP I/O obtains important improvements in most of the considered scenarios.