The time domain finite element algorithm has been widely used in airborne electromagnetic three-dimensional forward modeling. However, due to the large airborne electromagnetic measurement area and dense sampling, the forward calculation is huge, and the traditional serial algorithm cannot meet the calculation efficiency requirements. In view of such a situation, the authors carried out parallel acceleration algorithm research to solve the problem of insufficient computational efficiency. Based on the limited range of influence of aviation electromagnetic system, the local grid technology is used to divide the computing task into multiple sub-grids, that is, a set of grids for each source, and the forward calculations of each grid are independent of each other, and hence no data dependency is existent and there is good parallelism. In this paper, MPI technology is used to allocate multiple sub-grid forward tasks, and parallel computing is performed on each process. For each forward subgrid, in the forward modeling of the time domain finite element algorithm, the parallel matrix is calculated by OpenMP technology. The numerical simulation results of the typical electrical model show that the MPI+OpenMP parallel forward algorithm developed in this paper can effectively improve the forward speed, and the maximum acceleration ratio can reach 10 times.
Yin C C, Zhang B, Liu Y H , et al. Simulation of time domain aeromagnetic forward modeling under 2.5-dimensional undulating surface conditions[J]. Chinese Journal of Geophysics, 2015,58(4):1411-1424.
Um E S, Harris J M, Alumbaugh D L . 3D time-domain simulation of electromagnetic diffusion phenomena: A finite-element electric-field approach[J]. Geophysics, 2010,75(4):F115-F126, doi: 10.1190/1.3473694.
李贺 . 直接时间域矢量有限元瞬变电磁三维正演模拟[D]. 西安:长安大学, 2016.
Li H . Direct time domain vector finite element transient electromagnetic three-dimensional forward modeling [D]. Xi'an: Chang’an University, 2016.
Qi Y F, Yin C C, Liu Y H , et al. A three-dimensional time domain aeromagnetic electromagnetic full waveform forward modeling based on instantaneous current pulse[J]. Chinese Journal of Geophysics, 2017,60(1):369-382.
齐彦福 . 复杂介质中时间域航空电磁数据仿真技术研究[D]. 长春:吉林大学, 2017.
Qi Y F . Research on time domain aeronautical electromagnetic data simulation technology in complex media[D]. Changchun:Jilin University, 2017.
Newman G A, Alumbaugh D L . Three-dimensional massively parallel electromagnetic inversion[J]. Geophysics, 1997,128:345-354.
Li X K . Research on finite element two-dimensional forward modeling parallel computing based on MPI in frequency domain aeromagnetic method[D]. Beijing: China University of Geosciences, 2011.
陈辉 . 基于MPI的航空瞬变电磁一维正反演[D]. 成都:成都理工大学, 2015.
Chen H . MPI-based aeronautical transient electromagnetic one-dimensional forward and inversion[D]. Changdu:Chengdu University of Technology, 2015.
Yang D, Oldenburg D W, Haber E . 3-D inversion of airborne electromagnetic data parallelized and accelerated by local mesh and adaptive soundings[J]. Geophysical Journal International, 2014,196(3):1492-1507.
Ward S H, Hohmann G W. Electromagnetic theory for geophysical applications [C]//Electromagnetic Methods in Applied Geophysics, 1988,1(3):131-311.
Nédélec J C . Mixed finite elements in 3[J]. Numerische Mathematik, 1980,35(3):315-341.
Jin J M . The finite element method in electromagnetics, 2nd edn[M]. John Wiler and Sons, 2002.
Jahandari H, Farquharson C G . A finite-volume solution to the geophysical electromagnetic forward problem using unstructured grids[J]. Geophysics, 2014,79(6):E287-E302.