The adaptive cross approximation (ACA) algorithm, when used to accelerate the numerical solution of integral equations for radiation and scattering problems, sometimes suffers from inaccuracies. These inaccuracies occur when the ACA convergence criterion, which is based on an approximation of the residual relative error, is prematurely satisfied. This paper identifies the two sources of this problem and proposes adaptations of the algorithm that remedy them.
Heldring, A.; Ubeda, E.; Rius, J. On the convergence of the ACA algorithm for radiation and scattering problems. "IEEE transactions on antennas and propagation", 01 Juliol 2014, vol. 62, núm. 7, p. 3806-3809.