Loop control mechanism for scientific processor

Abstract

A loop control mechanism is described for use in a vector-oriented scientific data processing system. Because of the vector-oriented nature of scientific programs used on digital data processing systems the efficient control of program loops is of major importance. It can be shown that a procedure coded as N nested DO loops in FORTRAN will generally require 2N-1 nested loops of scientific processor object code, given a vector register architecture. Except for the innermost level, it is necessary at each level to iterate by strips up to the vector length and within that vector length strip to iterate by elements. For the innermost loop, iteration by element is not needed, but is implicit in vector operations. The present mechanism accomplishes this loop control optimization by maintaining the parameters for loop control in separate loop control registers. The use of this special facility for these parameters provides for their efficient management. The novelty of this invention centers around having special registers and unique instructions dedicated to the handling of the loop parameters. The use of these special registers and instructions for the controlling of these loops make it possible to efficiently precompute loop-counts, thereby enhancing the speed of the scientific processor.