1. In a computer system, a parallel task engine for performing tasks on data, the parallel task engine comprising: an input for receiving tasks; a scheduler for decomposing the tasks into one or more new tasks, the decomposing being dependent on at least one policy selected from a given set of policies; a run-time dynamic code generator for generating or locating, for the new tasks, operation routines; a set of job loops, at least one of the job loops for performing the new tasks on at least part of the data by executing the operation routines; the scheduler for distributing and assigning the new tasks to the at least one of the job loops; and the scheduler for making the selection of the at least one policy as a function of characteristics of the operation routines generated' or located by the run-time dynamic code generator.