1. A method in a multiprocessor system, the system comprising a plurality of processing elements, memory to which each of the processing elements has access, and a sequencer adapted to generate a sequence of code to be executed by the plurality of processing elements, the method comprising: receiving a plurality of signals during execution of the sequence of code, the signals indicating a plurality of memory access rules to be applied at instances during further execution of the sequence of code: at said instances, applying said memory access rules for memory accesses by the plurality of processing elements; and in the event of a memory access by a processing element violating one or more of said rules, generating a warning, signal.