Abstract : A very simple test, introduced by Ziv, allows one to determine if an approximation to the value f (x) of an elementary function at a given point x suffices to return the floating-point number nearest f(x). The same test may be used when implementing floating-point operations with input and output operands of different formats, using arithmetic operators tailored for manipulating operands of the same format. That test depends on a "magic constant" e. We show how to choose that constant e to make the test reliable and efficient. Various cases are considered, depending on the availability of an fma instruction, and on the range of f (x).
https://hal-ens-lyon.archives-ouvertes.fr/ensl-00693317
Contributor : Jean-Michel Muller
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Submitted on : Monday, July 8, 2013 - 10:56:40 AM
Last modification on : Thursday, December 13, 2018 - 1:29:03 AM
Document(s) archivé(s) le : Wednesday, October 9, 2013 - 4:20:52 AM
Florent de Dinechin, Christoph Lauter, Jean-Michel Muller, Serge Torres. On Ziv's rounding test. ACM Transactions on Mathematical Software, Association for Computing Machinery, 2013, 39 (4), pp.26. ⟨ensl-00693317v2⟩
