Improving Workload Balance of a Marine CSEM Inversion Application

The marine Controlled-Source Electromagnetic Method (mCSEM) complements traditional seismic surveys for oil and gas exploration. A ship with a robust electromagnetic transmitter close to the seabed moves over an area previously equipped with fixed electromagnetic receivers on the seafloor. The collected data is then subject to data inversion techniques to compute the subsurface resistivity volume under the seabed. We characterize the workload imbalance as it originates from the scheduling policy and the mapping between measurement data and the resistivity model. We then propose a workload balancing improvement by applying the Sorted-Greedy scheduling policy in this data inversion application. Using realistic datasets, we demonstrate that the policy reduces the execution time from 32.1% up to 40.3% without affecting the results' numerical accuracy. Our changes also improved the application scalability, enabling the execution with a larger number of processes achieving additional gains from 53.1% up to 60.9%.