Abstract: Marine controlled-source electromagnetics (MCSEM) is widely applied in fields such as electromagnetic detection of underwater targets, marine electromagnetic communication, and exploration of marine oil and gas resources. However, current MCSEM numerical simulations face challenges such as insufficient computational accuracy, low parallel communication efficiency, and limited scalability, making it difficult to meet the computational demands of large-scale, three-dimensional complex models. To address these issues, a multi-level parallel numerical simulation algorithm based on the fourth-order finite-difference time-domain (FDTD) method is designed and implemented in this paper. This algorithm employs parallel computation across transmitter sources and parallel solution strategies for sub-regions, fully exploiting parallel granularity. Additionally, it effectively reduces communication overhead through remote memory access technology, significantly enhancing parallel efficiency. The correctness and efficiency of the algorithm are then validated through multiple typical case studies. The results demonstrate that, for a deep-sea model without considering the air layer, with 8 transmitter sources, a regional scale of 20 km × 20 km × 12 km, and a grid size of 245 × 245 × 512, the computational time is reduced from 57.05 hours in serial computation to 72.96 seconds when using 8 process groups with a total of 2 048 processes, achieving a super-linear speedup of 2 815.04 and a parallel efficiency of 137.45%. For a shallow-sea model considering the air layer, with 8 process groups and a total of 256 processes, the computational time is reduced from 64.78 hours in serial computation to 59.75 minutes, achieving a speedup of 65.05 and a parallel efficiency of 25.41%. This algorithm exhibits good scalability and computational accuracy, providing an efficient solution for marine electromagnetic numerical simulations.

Key words: marine controlled-source electromagnetics;high-order time-domain finite-difference method;high performance computing;remote memory access, parallel algorithm;one-sided communication