Macro-parallelisation for controlled source electromagnetic applications

• We create an easy to implement electromagnetic parallelisation framework.
• The framework is applied to speed up computation for marine CSEM EM field simulation.
• The framework is applied to speed up computation for airborne EM inversion.
• Provided increasing number of CPU cores, computation time is highly reduced

Many geophysical computational problems can be referred to as “embarrassingly parallel”. Parallel computing utilises linked CPU cores to solve computational problems. We create a “macro” parallelisation method that rapidly recovers solutions to large scale electromagnetic forward and inverse modelling problems. The method involves software operating above a generic electromagnetic data structure. Two examples are provided.The first example quantifies the reduction in computational time where macro-parallelisation is applied to forward modelling of data generated during synthetic marine controlled source electromagnetic surveys. In the second numerical experiment we apply macro-parallelisation to recover the subsurface conductivity distribution from a large airborne transient electromagnetic survey spanning more than 2000 km2. The computation time for inverting 98 thousand soundings with a serial batch approach on an i7 with a single thread was 65 h. Computational time from inverting 98 thousand soundings on a single thread of a standard i7 processor was 65 h. A 1700 times improvement in computation time was achieved through macro-parallelisation across just 350 cores of a Cray XC30 Supercomputer. Inversion of data for the full AEM survey took just 135 s.Parallel computing is rapidly becoming an essential for geophysicists. We provide description, sequence diagrams, pseudo-code and examples to illustrate its implementation. In summary we present applied parallelisation for the masses.