Crate twofloat

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twofloat

This library provides an implementation of double-double arithmetic for the Rust language. Note that this is not the same as the IEEE quadruple-precision floating-point format. Instead, higher precision is obtained by representing the value as the sum of two non-overlapping f64 values.

Usage

The basic type is TwoFloat which represents the sum of two non-overlapping f64 values, which may be initialized from a single f64 or by calling a constructor that performs an arithmetic operation on a pair of f64 values.

extern crate twofloat;
use twofloat::TwoFloat;

let a = TwoFloat::from(3.4);
let b = TwoFloat::new_add(1.0, 1.0e-300);
let c = TwoFloat::new_sub(1.0, 1.0e-300);
let d = TwoFloat::new_mul(5.0, 0.7);
let e = TwoFloat::new_div(1.0, 7.0);

Basic arithmetic operators and comparisons are available, together with the utility functions abs(), is_positive_sign() and is_negative_sign(). Mathematical functions are provided if the math_funcs feature is enabled (this is enabled by default), though the implementations should be regarded as preliminary.

Operations on non-finite values are not supported. At the moment this is not automatically checked. The is_valid() method is provided for this purpose.

If the serde feature is enabled, serialization and deserialization is possible through the Serde library.

Known issues

This library depends on the std implementations of the floating point mathematical functions, which in turn depend on the C standard library implementation, which may have variations between platforms.

References

  • Mioara Joldes, Jean-Michel Muller, Valentina Popescu. Tight and rigourous error bounds for basic building blocks of double-word arithmetic. ACM Transactions on Mathematical Software, Association for Computing Machinery, 2017, 44 (2), pp.1 - 27. 10.1145/3121432. hal-01351529v3

  • Alan H. Karp, Peter Markstein. High Precision Division and Square Root. ACM Transactions on Mathematical Software, Association for Computing Machinery, 1997, 23 (4), pp. 561-589. 10.1145/279232.279237.

  • S. Chevillard, M. Joldeș and C. Lauter. Sollya: an environment for the development of numerical codes. Mathematical Software - ICMS 2010, pp. 28–31.

Modules

consts
Basic mathematical constants.

Structs

TwoFloat
Represents a two-word floating point type, represented as the sum of two non-overlapping f64 values.

Enums

TwoFloatError
The error type for TwoFloat operations.

Functions

no_overlap
Checks if two f64 values do not overlap, with the first value being the more significant. This matches definition 1.4 in Joldes et al. (2017).