A number of computational techniques are described that reduce the effort related to the continuous fast multipole method,used for the evaluation of Coulomb matrix elements as needed in Hartree-Fock and density functional theories.A new extent definition for Gaussian charge distributions is proposed,as well as a new way of dividing distributions into branches.Also,a new approach for estimating the error caused by truncation of multipole expansions is presented.It is found that the use of dynamically truncated multipole expansions gives a speedup of a factor of 10 in the work required for multipole interactions,compared to the case when all interactions are computed using a fixed multipole expansion order.Results of benchmark calculations on three-dimensional systems are reported,demonstrating the usefulness of our present implementation of the fast multipole method.
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