Scaling test of RASCAS based on an idealised galactic disc simulation: total elapsed time for a realistic MCRT experiment as a function of the number of CPUs used for the run. Red symbols show the results for the series where the computational domain is decomposed into one single data domain, whereas the blue crosses (respectively green crosses) are for the case where the computational domain is decomposed into 10 (resp. 1000) data domains. These three simulations were run with N_bundle = 10. Orange crosses again show the case where the computational domain is decomposed into 1000 data domains, but this time using N_bundle = 100. To guide the eye, the dashed line shows the ideal case of relation .