Processor cores using packet identifiers for routing and computation are disclosed. One method includes executing a complex computation using a set of processing cores. The method includes routing a set of packets using a set of packet identifiers and executing a set of instructions. The set of instructions are defined using a set of operand identifiers. The operand identifiers represent packet identifiers in the set of packet identifiers. In specific implementations the set of the operand identifiers represent packet identifiers in the set of packet identifiers in that a set of memories on the set of processing cores stores data values in common association with both the set of packets, and a set of operands identified by the set of operand identifiers. In specific implementations the set of operand identifiers and packet identifiers are unambiguously mapped to an underlying set of application datums of the complex computation.