Electrical computers: arithmetic processing and calculating – Electrical digital calculating computer – Particular function performed
Patent
1998-02-02
2000-12-19
Mai, Tan V.
Electrical computers: arithmetic processing and calculating
Electrical digital calculating computer
Particular function performed
708605, G06F 738
Patent
active
061637912
ABSTRACT:
An improved method of estimating the square root, reciprocal square root, and reciprocal of an input value in a computer system. The input value, after being normalized, is used to select a pair of constants from a table. The constants are based on a linear approximation of the function for each interval of the input value, offset to reduce a maximum error value for a given interval. The estimated function is calculated by adding or subtracting the product of a part of the normalized input value and the first constant from the second constant. In one implementation, the input value is normalized within the range 1.ltoreq.x<2, and one lookup table is used, having an interval size of 1/32. In a further preferred embodiment, only a lower order part of the mantissa is used in the multiply-add operation, to reduce the number of bits required (the high order part of the mantissa is used to select the constants from the table). In another implementation, the input value is normalized within the range 0.5.ltoreq.x<2, and two lookup tables are used, a first table having an interval size of 1/32 for the range 0.5.ltoreq.x<1, and a second table having an interval size of 1/16 for the range 1.ltoreq.x<2.
REFERENCES:
patent: 4477879 (1984-10-01), Wong
patent: 4503549 (1985-03-01), Slabinski
patent: 4823301 (1989-04-01), Knierim
patent: 5220524 (1993-06-01), Hesson
patent: 5245564 (1993-09-01), Quek et al.
patent: 5305248 (1994-04-01), Ammann
patent: 5386375 (1995-01-01), Smith
patent: 5563818 (1996-10-01), Agarwal et al.
patent: 5650953 (1997-07-01), Kaku et al.
Schmookler Martin Stanley
Senziq Donald Norman
England Anthony V. S.
International Business Machines - Corporation
Mai Tan V.
LandOfFree
High accuracy estimates of elementary functions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High accuracy estimates of elementary functions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High accuracy estimates of elementary functions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-277766