Before revision:  Only a serial implementation of the algorithm is considered in this paper, however, whose efficiency in terms of memory and speed is illustrated by means of a variety of numerical results, for a problem of acoustic size of 512\lambda} .
After revision:  Only a serial implementation of the algorithm is considered in this paper, however, whose efficiency in terms of memory and speed is illustrated by means of a variety of numerical experiments -- including a 43 min., single-core operator evaluation (on 10 GB of peak memory), with a relative error of 1.5\times 10^{-2, for a problem of acoustic size of 512\lambda} .