a) Strong scaling results for the multigroup diffusion test (circles) and the ideal MHD Orszag-Tang vortex calculation (diamonds). The ideal theoretical speedup is at the boundary between the grey and white areas. The Occigen machine has 12-core processors; the 12-core region is marked by the green hatched area. b) Weak scaling efficiency for the RHD and MHD runs. c) CPU time per BiCGSTAB iteration for a 1D diffusion problem (circles) and a 1D non-stationary radiative shock (squares) as a function of the number of frequency groups N_g used. The curve for a time proportional to is shown as a dotted line.