The MPFR library is a C library for multiple-precision floating-point
computations with exact rounding (also called correct rounding).  It is
based on the GMP multiple-precision library and should replace the MPF
class in further releases of GMP.

  The main goal of MPFR is to provide a library for multiple-precision
floating-point computation which is both efficient and has a well-defined
semantics.  It copies the good ideas from the ANSI/IEEE-754 standard for
double-precision floating-point arithmetic (53-bit mantissa).

Homepage:
https://www.mpfr.org/
