Expand description
ARPFloat is an implementation of arbitrary precision
floating point data
structures and utilities. The library can be used to emulate existing
floating point types, such as FP16, and create new floating point types.
Floating point types can scale to hundreds of digits, and perform very
accurate calculations. In ARPFloat the rounding mode is a part of the
type-system, and this defines away a number of problem that show up when
using fenv.h.
Example
use arpfloat::Float;
use arpfloat::FP128;
// Create the number '5' in FP128 format.
let n = Float::from_f64(5.).cast(FP128);
// Use Newton-Raphson to find the square root of 5.
let mut x = n.clone();
for _ in 0..20 {
x += (&n / &x)/2;
}
println!("fp128: {}", x);
println!("fp64: {}", x.as_f64());The program above will print this output:
fp128: 2.2360679774997896964091736687312763
fp64: 2.23606797749979
The library also provides API that exposes rounding modes, and low-level operations.
use arpfloat::FP128;
use arpfloat::RoundingMode::NearestTiesToEven;
use arpfloat::Float;
let x = Float::from_u64(FP128, 1<<53);
let y = Float::from_f64(1000.0).cast(FP128);
let val = Float::mul_with_rm(&x, &y, NearestTiesToEven);View the internal representation of floating point numbers:
use arpfloat::Float;
use arpfloat::FP16;
let fp = Float::from_i64(FP16, 15);
fp.dump(); // Prints FP[+ E=+3 M=11110000000]
let m = fp.get_mantissa();
m.dump(); // Prints 11110000000Control the rounding mode for type conversion:
use arpfloat::{FP16, FP32, RoundingMode, Float};
let x = Float::from_u64(FP32, 2649); // Load an FP32 Value.
let b = x.cast_with_rm(FP16, RoundingMode::Zero); // Convert to FP16.
println!("{}", b); // Prints 2648!Define new float formats and use high-precision transcendental functions:
use arpfloat::{Float, Semantics, RoundingMode};
// Define a new float format with 120 bits of accuracy, and dynamic range
// of 2^10.
let sem = Semantics::new(10, 120, RoundingMode::NearestTiesToEven);
let pi = Float::pi(sem);
let x = Float::exp(&pi);
println!("e^pi = {}", x); // Prints 23.1406926327792....Floating point numbers can be converted to Continued Fractions that approximate the value.
use arpfloat::{Float, FP256, RoundingMode};
let ln = Float::ln2(FP256);
println!("ln(2) = {}", ln);
for i in 1..20 {
let (p,q) = ln.as_fraction(i);
println!("{}/{}", p.as_decimal(), q.as_decimal());
}The program above will print this output:
ln(2) = .6931471805599453094172321214581765680755001343602552.....
0/1
1/1
2/3
7/10
9/13
61/88
192/277
253/365
445/642
1143/1649
1588/2291
2731/3940
....