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Fraction Addition or Subtraction or Comparison Overlap With Characteristic Comparison

IP.com Disclosure Number: IPCOM000078280D
Original Publication Date: 1972-Dec-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Levine, SR: AUTHOR

Abstract

This technique increases the speed of execution of floating-point addition, subtraction, and comparison when the characteristics (exponents) of the two operands are equal.

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Fraction Addition or Subtraction or Comparison Overlap With Characteristic Comparison

This technique increases the speed of execution of floating-point addition, subtraction, and comparison when the characteristics (exponents) of the two operands are equal.

Addition, subtraction, or comparison of two floating-point numbers consists of a characteristic comparison and a fraction addition, subtraction, or comparison. Before the fraction arithmetic, the characteristic of the two operands must be made equal which implies a shifting of one of the fractions before the fraction addition, subtraction or comparison. By performing the arithmetic operation on the fractions in parallel with the characteristic comparison, time can be saved when the characteristics are the same. Addition, subtraction and comparison operations frequently have as their operands, floating-point numbers with the same characteristics.

Normally, the first step of a floating-point operation is an exponent or characteristic compare, to determine which operand's exponent is smaller and by how much. The fraction with the smaller characteristic is right-shifted, and its characteristic is increased by one for each hexadecimal digit of shift until the two operand's characteristics agree. The fractions are then added if the operation is addition, subtracted if the operation is subtraction, or compared if the operation is a comparison. Then normalization can occur if required or the next operation can occur....