Development of a High-speed Eigenvalue-solver for Constant Plasma Monitoring on a Cell Cluster System

We developed a high speed eigenvalue solver that is an essential part of a plasma stability analysis system for fusion reactors on a Cell cluster system. In order to achieve continuous operation of fusion reactors, we must evaluate the state of plasma within the characteristic confinement time of the plasma density and temperature in fusion reactors. This is because we can prevent plasma from being disrupted by controlling the confining magnetic field, if we can determine the state of the plasma within the characteristic confinement time. Therefore, we introduced a Cell processor that has high computational power and high performance/cost, in order to achieve constant monitoring of fusion reactors. Furthermore, we developed a novel eigenvalue solver, which usually consumes most of the plasma evaluation time, to achieve high performance of our Cell cluster system. The eigensolver is based on the conjugate gradient (CG) method and was designed by considering three levels of parallelism, which we refer to as Intra-processor, Inner-processor, and SIMD parallel. In addition, we developed a new CG acceleration method, called locally complete LU. This method has the same acceleration performance as complete LU, which is one of the best acceleration methods, without any reduction in parallel performance. Finally, we succeeded in obtaining our target performance: we were able to solve a block tri-diagonal Hermitian matrix containing 1024 diagonal blocks, where the size of each block was 128 × 128, within a second. Therefore, we have found a suitable candidate for achieving a satisfactory monitoring system.