1. A method of operating a computer, the computer comprising a plurality of processors and a plurality of devices adapted to issue interrupts, each interrupt to be serviced by a processor of the plurality of processors, the processors being configured in a plurality of groups based on proximity, and the method establishing messages for each of the plurality of devices, each message for use in interrupting a processor of the plurality of processors, the method comprising: creating a plurality of messages for each of the plurality of devices, the creating comprising selecting as a target processor in each of the plurality of messages a target processor so as to maximize a number of groups within the plurality of groups targeted by messages created for each device of the plurality of devices and to minimize a number of messages targeting each group of the plurality of groups.