Building and utilizing fault tolerance support tools for the GASPI applications

Today’s High Performance Computing (HPC) systems are made possible by multiple increase in hardware parallelity. This results in the decrease of mean time to failures (MTTF) of the systems with every newer generation, which is an alarming trend. Therefore, it is not surprising that a lot of research is going on in the area of fault tolerance and fault mitigation. Applications should survive a failure and/or be able to recover with minimal cost. We have used GASPI, which is a relatively new communication library based on the PGAS model. It fulfills the basic requirement of a fault tolerant communication library , i.e., failure of a process do not cause the remaining processes to fail. This work is focused to extend the fault tolerance features of GASPI in form of a supporting health-check (HC) library that applications can benefit from. These features include failure detection, its information propagation, recovery management, communication recovery, etc. To reinforce its utility, we have also developed a fault tolerant neighbor node-level checkpoint/restart (CR) library. Instead of introducing algorithm-based fault tolerance in its true sense, we demonstrate how (using these supplementary fault tolerance functions) one can build applications to allow integrate a low cost fault detection/recovery mechanism and, if necessary, recover the application on the fly. We showcase the usage of these tools by implementing them in three different applications. Two of the applications fall in the category of linear sparse solvers, whereas the third application is based on a fluid flow solver. We also analyze the overheads involved in failure-free cases as well as various failure cases. Our fault detection mechanism causes no overhead in failure-free cases, whereas in case of failure(s), the failure detection and recovery cost is of reasonably acceptable order and shows good scalability.