A computer (30) has parallel elementary processors (P1, . . . , PK) interconnected by an optical crossbar switch (32). Multiple groups of processors, each having a separate crossbar switch, are connected by exchange switches. Optical fibers (34) are used to provide high speed communication between the processors and the switch (32). The optical crossbar switch (32) is reconfigurable dynamically. The computer is reconfigurable to provide efficient implementations of signal processing and logical inference computations, including a systolic filter, a fast Fourier transform, a correlator and a matrix-vector multiplier, forward and backward chaining inference machine, and speech recognizer.