2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/83561The discrete-dipole approximation (DDA) is a flexible technique for computing scattering and absorption by targets of arbitrary geometry. In this paper we perform systematic study of various non-stationary iterative (conjugate gradient) methods in search for the most efficient one in order to solve the system of equations arising in DDA. We document implementation of these methods in our public domain code DDSCAT.5aAtmospheric and Oceanic Physicstext