Development of preconditioned communication avoiding CG solver for multiphase CFD code JUPITER

Mayumi, Akie ; Idomura, Yasuhiro   ; Ina, Takuya; Yamada, Susumu  ; Imamura, Toshiyuki*

The left-preconditioned communication avoiding conjugate gradient (LP-CA-CG) method is applied to the pressure Poisson equation in the multiphase CFD code JUPITER. The arithmetic intensity of the LP-CA-CG method is analyzed, and is dramatically improved by loop splitting for inner product operations and for three term recurrence operations. The LP-CA-CG solver shows good strong scaling up to 30,000 nodes on the K computer.