Acceleration of the sources reconstruction method via the fast multipole method

From the results it can be concluded that the CGNR-FMM allows a significant computational time reduction with respect to the previous CGNR-MST, completing the SRM algorithm optimization both in memory and time requirements. One of the key points of this work is the fact that the improvement on time requirements can be achieved at the expense of a slightly increase on memory consumption. Further improvements of the CGNR-FMM performance will lie on the optimization of the source and observation groups size, and on the reduction of the number of multipoles.