Performance evaluations of communication-avoiding Krylov subspace methods in multi-phase thermal-hydraulic problem

Mayumi, Akie ; Idomura, Yasuhiro   ; Yamada, Susumu  ; Ina, Takuya; Yamashita, Susumu   

In this work, we implemented the Communication-Avoiding CG (CA-CG) method to the Poisson solver in the JUPITER code, which analyzes a multi-phase thermal-hydraulic problem, and evaluated its convergence property and computational performance. We analyzed the degradation of the convergence property due to accumulation of numerical errors associated with CA procedures, and applied quad-precision computation to a part of the CA-CG method to improve the convergence property.