rust/library/coretests/tests/floats/f16.rs

// FIXME(f16_f128): only tested on platforms that have symbols and aren't buggy
#![cfg(target_has_reliable_f16)]

use std::f16::consts;

use super::{assert_approx_eq, assert_biteq};

/// Tolerance for results on the order of 10.0e-2
#[allow(unused)]
const TOL_N2: f16 = 0.0001;

/// Tolerance for results on the order of 10.0e+0
#[allow(unused)]
const TOL_0: f16 = 0.01;

/// Tolerance for results on the order of 10.0e+2
#[allow(unused)]
const TOL_P2: f16 = 0.5;

/// Tolerance for results on the order of 10.0e+4
#[allow(unused)]
const TOL_P4: f16 = 10.0;

/// First pattern over the mantissa
const NAN_MASK1: u16 = 0x02aa;

/// Second pattern over the mantissa
const NAN_MASK2: u16 = 0x0155;

// FIXME(f16_f128,miri): many of these have to be disabled since miri does not yet support
// the intrinsics.

#[test]
#[cfg(not(miri))]
#[cfg(target_has_reliable_f16_math)]
fn test_mul_add() {
    let nan: f16 = f16::NAN;
    let inf: f16 = f16::INFINITY;
    let neg_inf: f16 = f16::NEG_INFINITY;
    assert_biteq!(12.3f16.mul_add(4.5, 6.7), 62.031);
    assert_biteq!((-12.3f16).mul_add(-4.5, -6.7), 48.625);
    assert_biteq!(0.0f16.mul_add(8.9, 1.2), 1.2);
    assert_biteq!(3.4f16.mul_add(-0.0, 5.6), 5.6);
    assert!(nan.mul_add(7.8, 9.0).is_nan());
    assert_biteq!(inf.mul_add(7.8, 9.0), inf);
    assert_biteq!(neg_inf.mul_add(7.8, 9.0), neg_inf);
    assert_biteq!(8.9f16.mul_add(inf, 3.2), inf);
    assert_biteq!((-3.2f16).mul_add(2.4, neg_inf), neg_inf);
}

#[test]
#[cfg(any(miri, target_has_reliable_f16_math))]
fn test_recip() {
    let nan: f16 = f16::NAN;
    let inf: f16 = f16::INFINITY;
    let neg_inf: f16 = f16::NEG_INFINITY;
    assert_biteq!(1.0f16.recip(), 1.0);
    assert_biteq!(2.0f16.recip(), 0.5);
    assert_biteq!((-0.4f16).recip(), -2.5);
    assert_biteq!(0.0f16.recip(), inf);
    assert_approx_eq!(f16::MAX.recip(), 1.526624e-5f16, 1e-4);
    assert!(nan.recip().is_nan());
    assert_biteq!(inf.recip(), 0.0);
    assert_biteq!(neg_inf.recip(), -0.0);
}

#[test]
#[cfg(not(miri))]
#[cfg(target_has_reliable_f16_math)]
fn test_powi() {
    let nan: f16 = f16::NAN;
    let inf: f16 = f16::INFINITY;
    let neg_inf: f16 = f16::NEG_INFINITY;
    assert_biteq!(1.0f16.powi(1), 1.0);
    assert_approx_eq!((-3.1f16).powi(2), 9.61, TOL_0);
    assert_approx_eq!(5.9f16.powi(-2), 0.028727, TOL_N2);
    assert_biteq!(8.3f16.powi(0), 1.0);
    assert!(nan.powi(2).is_nan());
    assert_biteq!(inf.powi(3), inf);
    assert_biteq!(neg_inf.powi(2), inf);
}

#[test]
fn test_to_degrees() {
    let pi: f16 = consts::PI;
    let nan: f16 = f16::NAN;
    let inf: f16 = f16::INFINITY;
    let neg_inf: f16 = f16::NEG_INFINITY;
    assert_biteq!(0.0f16.to_degrees(), 0.0);
    assert_approx_eq!((-5.8f16).to_degrees(), -332.315521, TOL_P2);
    assert_approx_eq!(pi.to_degrees(), 180.0, TOL_P2);
    assert!(nan.to_degrees().is_nan());
    assert_biteq!(inf.to_degrees(), inf);
    assert_biteq!(neg_inf.to_degrees(), neg_inf);
    assert_biteq!(1_f16.to_degrees(), 57.2957795130823208767981548141051703);
}

#[test]
fn test_to_radians() {
    let pi: f16 = consts::PI;
    let nan: f16 = f16::NAN;
    let inf: f16 = f16::INFINITY;
    let neg_inf: f16 = f16::NEG_INFINITY;
    assert_biteq!(0.0f16.to_radians(), 0.0);
    assert_approx_eq!(154.6f16.to_radians(), 2.698279, TOL_0);
    assert_approx_eq!((-332.31f16).to_radians(), -5.799903, TOL_0);
    assert_approx_eq!(180.0f16.to_radians(), pi, TOL_0);
    assert!(nan.to_radians().is_nan());
    assert_biteq!(inf.to_radians(), inf);
    assert_biteq!(neg_inf.to_radians(), neg_inf);
}

#[test]
fn test_float_bits_conv() {
    assert_eq!((1f16).to_bits(), 0x3c00);
    assert_eq!((12.5f16).to_bits(), 0x4a40);
    assert_eq!((1337f16).to_bits(), 0x6539);
    assert_eq!((-14.25f16).to_bits(), 0xcb20);
    assert_biteq!(f16::from_bits(0x3c00), 1.0);
    assert_biteq!(f16::from_bits(0x4a40), 12.5);
    assert_biteq!(f16::from_bits(0x6539), 1337.0);
    assert_biteq!(f16::from_bits(0xcb20), -14.25);

    // Check that NaNs roundtrip their bits regardless of signaling-ness
    let masked_nan1 = f16::NAN.to_bits() ^ NAN_MASK1;
    let masked_nan2 = f16::NAN.to_bits() ^ NAN_MASK2;
    assert!(f16::from_bits(masked_nan1).is_nan());
    assert!(f16::from_bits(masked_nan2).is_nan());

    assert_eq!(f16::from_bits(masked_nan1).to_bits(), masked_nan1);
    assert_eq!(f16::from_bits(masked_nan2).to_bits(), masked_nan2);
}

#[test]
fn test_algebraic() {
    let a: f16 = 123.0;
    let b: f16 = 456.0;

    // Check that individual operations match their primitive counterparts.
    //
    // This is a check of current implementations and does NOT imply any form of
    // guarantee about future behavior. The compiler reserves the right to make
    // these operations inexact matches in the future.
    let eps_add = if cfg!(miri) { 1e1 } else { 0.0 };
    let eps_mul = if cfg!(miri) { 1e3 } else { 0.0 };
    let eps_div = if cfg!(miri) { 1e0 } else { 0.0 };

    assert_approx_eq!(a.algebraic_add(b), a + b, eps_add);
    assert_approx_eq!(a.algebraic_sub(b), a - b, eps_add);
    assert_approx_eq!(a.algebraic_mul(b), a * b, eps_mul);
    assert_approx_eq!(a.algebraic_div(b), a / b, eps_div);
    assert_approx_eq!(a.algebraic_rem(b), a % b, eps_div);
}

#[test]
fn test_from() {
    assert_biteq!(f16::from(false), 0.0);
    assert_biteq!(f16::from(true), 1.0);
    assert_biteq!(f16::from(u8::MIN), 0.0);
    assert_biteq!(f16::from(42_u8), 42.0);
    assert_biteq!(f16::from(u8::MAX), 255.0);
    assert_biteq!(f16::from(i8::MIN), -128.0);
    assert_biteq!(f16::from(42_i8), 42.0);
    assert_biteq!(f16::from(i8::MAX), 127.0);
}