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The unum is a floating point format proposed by ], proposed as an alternative to the now ubiquitous ]. The proposal and justification are explained in his somewhat ambitiously-titled book The end of error. The '''unum''' is a floating point format proposed by ], proposed as an alternative to the now ubiquitous ]. The proposal and justification are explained in his somewhat ambitiously-titled book The end of error.


The two defining features of the unum format are: The two defining features of the unum format are:
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For performing computation with the format, Gustafson proposes using interval arithmetic with a pair of unums, what he calls an ubound, providing the guarantee that the resulting interval contains the exact solution. For performing computation with the format, Gustafson proposes using interval arithmetic with a pair of unums, what he calls an ubound, providing the guarantee that the resulting interval contains the exact solution.


Unum implementations have been explored in ].<ref>http://juliacomputing.com/blog/2016/03/29/unums.html</ref><ref>https://github.com/JuliaComputing/Unums.jl</ref><ref>https://github.com/REX-Computing/unumjl</ref><ref>https://github.com/tbreloff/Unums.jl</ref> Unum implementations have been explored in ].<ref>http://juliacomputing.com/blog/2016/03/29/unums.html</ref><ref>https://github.com/JuliaComputing/Unums.jl</ref><ref>https://github.com/REX-Computing/unumjl</ref><ref>https://github.com/tbreloff/Unums.jl</ref>


A "Great Debate" between ] and ] is planned for the Arith23 conference<ref>http://arith23.gforge.inria.fr/program.html</ref> on July 12, 2016. A "Great Debate" between ] and ] is planned for the Arith23 conference<ref>http://arith23.gforge.inria.fr/program.html</ref> on July 12, 2016.


==References== ==References==
{{Reflist}}

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The unum is a floating point format proposed by John Gustafson, proposed as an alternative to the now ubiquitous IEEE 754 formats. The proposal and justification are explained in his somewhat ambitiously-titled book The end of error.

The two defining features of the unum format are:

  • a variable-width storage format for both the significand and exponent, and
  • an “u-bit”, which determines whether the unum corresponds to an exact number (u=0), or an interval between consecutive exact unums (u=1). In this way, the unums cover the entire extended real number line .

For performing computation with the format, Gustafson proposes using interval arithmetic with a pair of unums, what he calls an ubound, providing the guarantee that the resulting interval contains the exact solution.

Unum implementations have been explored in Julia.

A "Great Debate" between William Kahan and John Gustafson is planned for the Arith23 conference on July 12, 2016.

References

  1. http://juliacomputing.com/blog/2016/03/29/unums.html
  2. https://github.com/JuliaComputing/Unums.jl
  3. https://github.com/REX-Computing/unumjl
  4. https://github.com/tbreloff/Unums.jl
  5. http://arith23.gforge.inria.fr/program.html