1. In a SIMD architecture having a two dimensional array of processing elements, where a controller broadcasts at least one broadcast instruction to all processing elements in the array, a dynamically reconfigurable switching means useful to connect four of the processing elements in the array into a group in accordance with either the broadcast instruction of the controller or a special communication instruction held in one selected processing element of the group, the switch comprising: at least one dataline connected to each of the processing elements in the group; a multiplexer means connected to each data line and to the controller and to a configuration register external to any processing element of the group, said configuration register controllable by any of the processing elements in the group, for loading the special communication instruction from the one selected processing element in the group into the configuration register and to operate in accord with either the broadcast instruction from the controller or the contents of the configuration register to select one of the data lines as a source of data and applying the data therefrom to a source output port; and a demultiplexer means connected to each data line and to the controller and to said configuration register, and directly connected to a source output port of the multiplexer means, to operate in accord with either the broadcast instruction from the controller or the contents of the configuration register to select one of the data lines and applying the data received directly from the source output port of the multiplexer means thereto.