Patent ID: 7080112

Claim:
A computer-implemented method of computing a computing machine representation of an approximation to the reciprocal of a floating point number x comprising the steps of: generating a computing machine representation of a floating point number {circumflex over (x)} by leaving a sign bit of x, which is loaded into a first fixed point register, unchanged, complementing exponent bits of x, leaving a first k fraction bits of x unchanged, and complementing remaining fraction bits of x; generating another computing machine representation of a floating point number t found by using the first k bits of the fraction of x, which is loaded into said first fixed point register, as an index into a table with 2 k entries; and computing the product {circumflex over (x)}×t computed with floating point arithmetic as an estimate of the reciprocal of x with 2×k+3 good bits which is loaded into a floating point register; and outputting said estimate of the reciprocal of x to be used by a high speed digital computer.