1. A computing method, comprising: accepting a definition of a computing task, which comprises multiple atomic Processing Elements (PEs) having execution dependencies, each execution dependency specifying that a respective first PE is to be executed before a respective second PE; compiling the computing task for concurrent execution on a multiprocessor device, which comprises multiple processors that are capable of executing a first number of the PEs simultaneously, by arranging the PEs, without violating the execution dependencies, in an invocation data structure comprising a second number of execution sequences that is greater than one but does not exceed the first number; and invoking the multiprocessor device to run software code that executes the execution sequences in parallel responsively to the invocation data structure, so as to produce a result of the computing task.