摘要
Occam反演以其稳定收敛和不依赖于初始模型的特性被广泛应用于大地电磁数据的处理,但偏导数矩阵的计算和拉格朗日乘子的求取导致大量的模型正演,使得反演速度较低。为此,研究了用基于PC机群的并行计算来解决这一问题的方法。首先对Occam反演方法进行了阐述;然后,分析了反演方法中各计算耗费的时间,提出对约占计算量90％的偏导数和拉格朗日乘子进行并行计算的思想,即偏导数计算采用频点计算一级的大粒度并行,拉格朗日乘子扫描和一维搜索分别采用μ值计算一级的大粒度并行和频点计算一级的小粒度并行;给出了并行计算的实现方法,即在PC机群上,利用主一从编程模式实现Occam反演的整体并行计算。在计算中,采用任务组合方式,减少了通信量,较好地实现了负载均衡。在4节点PC机群上,对应于拉格朗日乘子的扫描和一维搜索方式,整体加速比分别达到3．36和2．83。
Occam's inversion is widely used in magnetotelluric data processing for its stability of convergence and independence on initial model. But the calculations of Jacobian Matrix and Lagrange multiplier need some forward calculations, which would result in a low inversion speed. Based on parallel PC cluster computing, this article presents a solution to this problem. Firstly, it gives a general description of the Occam inversion; then it analyzes the calculation time on different part of the inversion, putting forward a thought of parallel computation for derivative matrix and Lagrange multiplier accounting for about 90% of the total inversion time. The performing procedures is as following: Implementing the parallelism for derivative matrix with frequency based coarse granularity; Lagrange multiplier scanning with coarse granularity based on μ calculation; La-grange multiplier one dimensional searching with frequency based fine granularity. The implementation method is given: Master-Slave programming on a PC cluster completes the whole computation. Task combination methods are a-dopted to reduce the message passing and balance the computation loads. On a 4 nodes PC cluster, the whole speedup of Occam inversion have reached 3. 36 and 2. 83 corresponding to Lagrange multiplier scanning and 1-D searching mode.
出处
《石油物探》
EI
CSCD
2006年第3期311-315,共5页
Geophysical Prospecting For Petroleum
基金
广西自然科学基金项目(桂科基0339070)
广西教育厅科研项目(桂教科研2003-22)资助
