FT-GCR: a fault-tolerant generalized conjugate residual elliptic solver

19/2021

FT-GCR: a fault-tolerant generalized conjugate residual elliptic solver

Wednesday 31st March 2021

Gillard, M.; Benacchio, T.

With the steady advance of high performance computing systems featuring smaller and smaller hardware components, the systems and algorithms used for numerical simulations increasingly contend with disruptions caused by hardware failures and bit-levels misrepresenta- tions of computing data. In numerical frameworks exploiting massive processing power, the solution of linear systems often represents the most computationally intensive component. Given the large amount of repeated operations involved, iterative solvers are particularly vulnerable to bit-flips. A new method named FT-GCR is proposed here that supplies the preconditioned Generalized Conjugate Residual Krylov solver with detection of, and recovery from, soft faults. The algorithm tests on the monotonic decrease of the residual norm and, upon failure, restarts the iteration within the local Krylov space. Numerical experiments on the solution of an elliptic problem arising from a stationary flow over an isolated hill on the sphere show the skill of the method in addressing bit-flips on a range of grid sizes and data loss scenarios, with best returns and detection rates obtained for larger corruption events. The simplicity of the method makes it easily extendable to other solvers and an ideal candidate for algorithmic fault tolerance within integrated model resilience strategies.