REKENAFDEL
I
NG
T.J.
DEKKER
stichting
mathematisch
centrum
MR
118/70
.f>.
FLOATING-POINT
TECHNIQUE
FOR
EXTENDING
THE
AVAILABLE
PRECISION
~
MC
JULI
2e
boerhaavestraat
49
amsterdam
31Dl..101Hllttl. MATHEMATISCH CE~TRIUM
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A
FLOATING-POINT
TECHNIQUE
FOR
EXTENDING
THE
AVAILABLE
PRECISION
Abstract
by
*)
T.J.
Dekker
A
technique
is
described
for
expressing
multilength
floating-point
arith-
metic
in
terms
of
singlelength
floating-point
arithmetic,
i.e.
the
arith-
metic
for
an
available
(say:
single
or
double
precision)
floating-point
number
system.
The
basic
algorithms
are
exact
addition
and
multiplication
of
two
singlelength
floating-point
numbers,
delivering
the
result
as
a
doublelength
floating-point
number. A
straightforward
application
of
the
technique
yields
a
set
of
algorithms
for
doublelength
arithmetic
which
are
given
as
ALGOL
60
procedures.
*)
Part
. . . • .
of
this
research
was done
while
the
author
was
visiting
Bell
Telephone
Laboratories,
Murray
Hill,
New
Jersey.
Contents
1
Introduction
2
Floating-point
number systems
3
Floating-point
operations
4 Exact
addition
5
Exact
multiplication
6
Splitting
into
halflength
numbers
7
Doublelength
arithmetic
8 Appendix.
ALGOL
60
procedures
9 Acknowledgements
10
References
page 1
4
6
8
16
21
24
32
36
36