A method comprises compiling, by a compiler, a received program to provide a compiler output for configuring hardware to implement the received program. The received program relate to packets of data in a memory. The compiling comprising defining by the compiler output a plurality of computational units in the hardware, each of the computational units being configured to receive a packet of data as a stream of words and between a first and a second of the computational units, a first buffer for storing words of a packet and a second buffer for storing data output by the first computational unit.