论文标题
大气断层扫描的增强小波重建器
An augmented wavelet reconstructor for atmospheric tomography
论文作者
论文摘要
大气断层扫描,即大气中的湍流轮廓的重建,是下一代极大望远镜的自适应光学(AO)系统的挑战性任务。在AO的社区中,首选求解器是所谓的矩阵矢量乘法(MVM),该求解器直接将系统运算符的(正规化)广义倒数应用于数据。对于小型望远镜而言,这种方法是可行的,但是对于诸如欧洲极大的望远镜(ELT)之类的较大系统,大气层层析成像问题更为复杂,并且计算效率成为一个问题。迭代方法,例如有限元小波混合算法(FEWHA),是一种有前途的选择。 FEWHA是一种基于小波的重建器,它使用众所周知的迭代预处理共轭梯度(PCG)方法作为求解器。通过使用前向操作员的矩阵表示,浮点操作和内存使用量的数量大大减少。实时性能的关键指标是PCG迭代的数量。在本文中,我们提出了FEWHA的增强版本,其中使用Krylov子空间回收技术减少了$ 50 \%$。我们证明,增强FEWHA的并行实施允许满足ELT的实时要求。
Atmospheric tomography, i.e. the reconstruction of the turbulence profile in the atmosphere, is a challenging task for adaptive optics (AO) systems of the next generation of extremely large telescopes. Within the community of AO the first choice solver is the so called Matrix Vector Multiplication (MVM), which directly applies the (regularized) generalized inverse of the system operator to the data. For small telescopes this approach is feasible, however, for larger systems such as the European Extremely Large Telescope (ELT), the atmospheric tomography problem is considerably more complex and the computational efficiency becomes an issue. Iterative methods, such as the Finite Element Wavelet Hybrid Algorithm (FEWHA), are a promising alternative. FEWHA is a wavelet based reconstructor that uses the well-known iterative preconditioned conjugate gradient (PCG) method as a solver. The number of floating point operations and memory usage are decreased significantly by using a matrix-free representation of the forward operator. A crucial indicator for the real-time performance are the number of PCG iterations. In this paper, we propose an augmented version of FEWHA, where the number of iterations is decreased by $50\%$ using a Krylov subspace recycling technique. We demonstrate that a parallel implementation of augmented FEWHA allows the fulfilment of the real-time requirements of the ELT.