Get rid of the parameters array. Rather we generate parameters on-on-fly. This is done using a new class ParameterHandlers, which handles the generation of parameters from a given 1D index. While at it, also do away with global variables. This allows to spawn processes rather than fork them. Even if it takes a little time to do the spawn, this allows to solves some deadlocks with libraries which do not support being used on both sides of a forked process. Overall these modifications makes startup faster (no need to compute the cache cleaning parameters beforehand) and the generation speed is also a few percent faster when the number of models is large enough to compensate for the relatively slow spaning time.