---
title: "MPFR — paper by Fousse et al. (2007) · ACM TOMS 33(2), art. 13"
description: "The authors present MPFR, an ISO C library built on the GNU MP (GMP) mpn layer and released… 42 references, cited by 18 papers here."
authors: ["Laurent Fousse", "Guillaume Hanrot", "Vincent Lefèvre", "Patrick Pélissier", "Paul Zimmermann"]
year: 2007
venue: "ACM TOMS 33(2), art. 13"
source: "https://memsic.ccsd.cnrs.fr/INPL/inria-00070266v1"
licence: "author's copy — read only"
summary_licence: "Elamur Cosmic License"
canonical: "https://research.elamur.ai/free/en/papers/fousse-2007-mpfr-multiple-precision-binary-floating/"
---
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# MPFR: a multiple-precision binary floating-point library with correct rounding

**Authors:** Laurent Fousse, Guillaume Hanrot, Vincent Lefèvre, Patrick Pélissier and Paul Zimmermann · **Year:** 2007 · **Venue:** ACM TOMS 33(2), art. 13 · **Licence:** author's copy — read only

**Links:** [Publisher's page](https://memsic.ccsd.cnrs.fr/INPL/inria-00070266v1) · [PDF](https://perso.ens-lyon.fr/guillaume.hanrot/Papers/toms.pdf)

**Citations:** [18](https://md.research.elamur.ai/free/en/papers/fousse-2007-mpfr-multiple-precision-binary-floating/cited-by/) in our library, of the 149,439 papers whose bibliographies we read

## Summary
Arbitrary-precision floating-point packages such as GMP's MPF, CLN and PARI typically lack precise semantics. Their outputs can shift whenever an internal algorithm changes, which undermines portability and makes correctness proofs impossible. The authors present MPFR, an ISO C library built on the GNU MP (GMP) mpn layer and released under the LGPL. It carries the guarantees of IEEE 754 over to arbitrary precision. Every variable carries its own binary precision, and each operation or mathematical function returns the exact result rounded correctly to the target variable's precision in the requested direction. Exceptions are also supported. The library uses radix 2 so that results are identical on 32- and 64-bit machines and so that the IEEE single, double and quadruple formats can be emulated. Benchmarks show that this rigor comes with little or no speed penalty relative to competing libraries, and MPFR is often faster. The authors also document misrounded results from other packages. MPFR matters because programs built on it inherit well-defined, reproducible arithmetic, and it already supports compilers, computer algebra systems and rigorous mathematical computations.

## Key points
- Each MPFR call returns a ternary "inexact flag" whose sign shows whether the stored result lies below, above or exactly at the true value. Precision can range from 2 bits up to whatever memory allows.
- Mantissas are stored as arrays of GMP limbs with a leading bit always set. The format has no subnormals and no implicit bit, and unused low-order bits are zero, so a p-bit number uses exactly p bits.
- Table II reports incorrectly rounded 53-bit results from NTL 5.4, PARI 2.2.12.beta and CLN 1.1.11. One example is a PARI tan x value that is off by about 8.245 ulp.
- Companion tools include MPFI (interval arithmetic), MPFR++ (a C++ interface), MPC (complex numbers with 16 rounding modes) and MPCHECK (a tester for fixed-precision math libraries).
- Users include gfortran in GCC-4.0 (for constant folding), Magma, CGAL, a guaranteed LLL implementation, the Fluctuat static analyzer, and rigorous computations of Maass cusp forms and checks of Artin's conjecture.

*Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.*

📚 Shelves (1): [➗ Mathematics](https://md.research.elamur.ai/free/en/shelves/mathematics/) · 233 works

## Cite

Cite as: Laurent Fousse, Guillaume Hanrot, Vincent Lefèvre, Patrick Pélissier and Paul Zimmermann. 2007. MPFR: a multiple-precision binary floating-point library with correct rounding. ACM TOMS 33(2), art. 13.

The paper itself, not this page. BibTeX from the library's record of the work.

```bibtex
@inproceedings{fousse2007mpfr,
  title = {{MPFR: a multiple-precision binary floating-point library with correct rounding}},
  author = {Laurent Fousse, Guillaume Hanrot, Vincent Lefèvre, Patrick Pélissier and Paul Zimmermann},
  booktitle = {ACM TOMS 33(2), art. 13},
  year = {2007},
  url = {https://memsic.ccsd.cnrs.fr/INPL/inria-00070266v1}
}
```

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## References

42 references, 0 of them with a card of ours. ↗ leads to the work, «find» searches for one we have no id for yet.

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*Updated 3 November 2026*