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(19) United States (12) Patent Application Publication (10) Pub. No.: US 2012/0259903 A1 (43) Pub. Date:
KAN et al. (54) ARITHMETIC CIRCUIT, ARITHMETIC
(52)
Oct. 11, 2012
US. Cl. ...................................................... .. 708/497
PROCESSING APPARATUS AND METHOD OF CONTROLLING ARITHMETIC CIRCUIT
(75) Inventors:
Ryuji KAN, Yokohama (JP); Hideyuki Unno, Kawasaki (JP);
(57)
ABSTRACT
Kenichi Kitamura, Kawasaki (JP)
An arithmetic circuit for rounding pre-rounded data includes
FUJITSU LIMITED, KaWasaki-shi (JP)
includes a mantissa of a ?xed-precision ?oating-point num
a ?rst register to store ?rst-format pre-rounded data that
(73) Assignee: (21) Appl. No.: (22) Filed:
(30)
13/439,932
precision data indicative of precision for rounding the pre
Apr. 5, 2012
rounded data, a leading Zero counting unit to count consecu tive Zeros starting from a most signi?cant bit of the mantissa
Foreign Application Priority Data Apr. 8, 2011
(JP) ............................... .. 2011-085881
Publication Classi?cation
(51)
Int. Cl. G06F 7/38
ber using a base-N numbering system, and includes an expo nent for the mantissa, a second register to store rounding
stored in the ?rst register, an exponent generating unit to generate a post-round exponent indicative of an exponent for a rounded signi?cant by subtracting the number of Zeros
counted by the leading Zero counting unit and the rounding precision data from a sum of one and the exponent stored in
the ?rst register, and an output register to store the post-round exponent and a rounding-add value that is to be added to a
(2006.01)
digit at Which rounding is performed.
Number
Positive
-
128
~10E+122 '
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1
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Patent Application Publication
Oct. 11, 2012 Sheet 1 0f 42
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Patent Application Publication
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US 2012/0259903 A1
FIGS
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Patent Application Publication
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US 2012/0259903 A1
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Patent Application Publication
Oct. 11, 2012 Sheet 6 0f 42
US 2012/0259903 A1
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Oct. 11, 2012 Sheet 12 0f 42
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