Posits: the good, the bad and the ugly

Florent de Dinechin 1 Luc Forget 1 Jean-Michel Muller 2 Yohann Uguen 1
1 SOCRATE - Software and Cognitive radio for telecommunications
CITI - CITI Centre of Innovation in Telecommunications and Integration of services, Inria Grenoble - Rhône-Alpes
2 ARIC - Arithmetic and Computing
Inria Grenoble - Rhône-Alpes, LIP - Laboratoire de l'Informatique du Parallélisme
Abstract : Many properties of the IEEE-754 floating-point number system are taken for granted in modern computers and are deeply embedded in compilers and low-level softare routines such as elementary functions or BLAS. This article reviews such properties on the Posit number system. Some are still true. Some are no longer true, but sensible work-arounds are possible, and even represent exciting challenge for the community. Some, in particular the loss of scale invariance for accuracy, are extremely dangerous if Posits are to replace floating point completely. This study helps framing where Posits are better than floating-point, where they are worse, and what tools are missing in the Posit landscape. For general-purpose computing, using Posits as a storage format only could be a way to reap their benefits without loosing those of classical floating-point.
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Florent de Dinechin, Luc Forget, Jean-Michel Muller, Yohann Uguen. Posits: the good, the bad and the ugly. CoNGA 2019 - Conference on Next-Generation Arithmetic, Mar 2019, Singapore, Singapore. pp.1-10, ⟨10.1145/3316279.3316285⟩. ⟨hal-01959581v4⟩

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