A method for computation is described, the method including configuring a processor to expand input seed values into respective output data values using an approximated expansion process such that the output data values are not guaranteed to satisfy a required output data criterion, selecting a seed value so that an output data value generated by the processor by application of the approximated expansion process to the selected seed value will yield an output data value that satisfies the required output data criterion, and storing the selected seed value in a non-volatile memory to be accessed by the processor. Related apparatus and systems are also described.