In this paper, SIMD and MIMD solutions for the real-time database management problem of air traffic control are compared. A real-time database system is highly constrained in a multiprocessor and access to the common database must be made to a limited number of data elements at a time. This MIMD database access is contrasted with the comparable SIMD common database access, which can be several hundred times greater. This is true because the SIMD can simultaneously access thousands of pertinent records instead of the limited number in the MIMD. A relatively simple example is given of a problem that has a polynomial time solution using a SIMD but for which a polynomial time solution using a MIMD is normally impossible. The fact that SIMD can support a polynomial time solution for the air traffic control problem but this problem is normally considered to be intractable for multiprocessors argues against the common belief that MIMD have greater power than SIMD. SIMD are more efficient and powerful for some critically important application areas.
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