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Move ulp increment/decrement functions into rmath utils.

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This commit is contained in:
Nathan Vegdahl 2023-08-04 00:45:44 +02:00
parent 911542c534
commit f4b7767198
2 changed files with 107 additions and 80 deletions
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83
src/fp_utils.rs
View File

@ -4,6 +4,7 @@
//! From Theory to Implementation" 3rd edition by Pharr et al.
use crate::math::{dot, Normal, Point, Vector};
pub use rmath::utils::{decrement_ulp, increment_ulp};
#[inline(always)]
pub fn fp_gamma(n: u32) -> f32 {
@ -12,36 +13,6 @@ pub fn fp_gamma(n: u32) -> f32 {
(e * n as f32) / (1.0 - (e * n as f32))
}
pub fn increment_ulp(v: f32) -> f32 {
if v.is_finite() {
if v > 0.0 {
f32::from_bits(v.to_bits() + 1)
} else if v < -0.0 {
f32::from_bits(v.to_bits() - 1)
} else {
f32::from_bits(0x00_00_00_01)
}
} else {
// Infinity or NaN.
v
}
}
pub fn decrement_ulp(v: f32) -> f32 {
if v.is_finite() {
if v > 0.0 {
f32::from_bits(v.to_bits() - 1)
} else if v < -0.0 {
f32::from_bits(v.to_bits() + 1)
} else {
f32::from_bits(0x80_00_00_01)
}
} else {
// Infinity or NaN.
v
}
}
pub fn robust_ray_origin(pos: Point, pos_err: f32, nor: Normal, ray_dir: Vector) -> Point {
// Get surface normal pointing in the same
// direction as ray_dir.
@ -81,51 +52,7 @@ pub fn robust_ray_origin(pos: Point, pos_err: f32, nor: Normal, ray_dir: Vector)
Point::new(x, y, z)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn inc_ulp() {
assert!(increment_ulp(1.0) > 1.0);
assert!(increment_ulp(-1.0) > -1.0);
}
#[test]
fn dec_ulp() {
assert!(decrement_ulp(1.0) < 1.0);
assert!(decrement_ulp(-1.0) < -1.0);
}
#[test]
fn inc_ulp_zero() {
assert!(increment_ulp(0.0) > 0.0);
assert!(increment_ulp(0.0) > -0.0);
assert!(increment_ulp(-0.0) > 0.0);
assert!(increment_ulp(-0.0) > -0.0);
}
#[test]
fn dec_ulp_zero() {
assert!(decrement_ulp(0.0) < 0.0);
assert!(decrement_ulp(0.0) < -0.0);
assert!(decrement_ulp(-0.0) < 0.0);
assert!(decrement_ulp(-0.0) < -0.0);
}
#[test]
fn inc_dec_ulp() {
assert_eq!(decrement_ulp(increment_ulp(1.0)), 1.0);
assert_eq!(decrement_ulp(increment_ulp(-1.0)), -1.0);
assert_eq!(decrement_ulp(increment_ulp(1.2)), 1.2);
assert_eq!(decrement_ulp(increment_ulp(-1.2)), -1.2);
}
#[test]
fn dec_inc_ulp() {
assert_eq!(increment_ulp(decrement_ulp(1.0)), 1.0);
assert_eq!(increment_ulp(decrement_ulp(-1.0)), -1.0);
assert_eq!(increment_ulp(decrement_ulp(1.2)), 1.2);
assert_eq!(increment_ulp(decrement_ulp(-1.2)), -1.2);
}
}
// #[cfg(test)]
// mod tests {
// use super::*;
// }

104
sub_crates/rmath/src/utils.rs
View File

@ -9,7 +9,7 @@
#[inline(always)]
pub fn ulp_diff(a: f32, b: f32) -> u32 {
const TOP_BIT: u32 = 1 << 31;
const NAN_THRESHOLD: u32 = 0x7f800000;
const INFINITY: u32 = 0x7f800000;
let a = a.to_bits();
let b = b.to_bits();
@ -19,7 +19,7 @@ pub fn ulp_diff(a: f32, b: f32) -> u32 {
let a_abs = a & !TOP_BIT;
let b_abs = b & !TOP_BIT;
if a_abs > NAN_THRESHOLD || b_abs > NAN_THRESHOLD {
if a_abs > INFINITY || b_abs > INFINITY {
// NaNs always return maximum ulps apart.
u32::MAX
} else if a_sign == b_sign {
@ -36,6 +36,56 @@ pub fn ulps_eq(a: f32, b: f32, max_ulps: u32) -> bool {
ulp_diff(a, b) <= max_ulps.min(u32::MAX - 1)
}
/// Increments to the next representable floating point number.
///
/// Notes:
/// - 0.0 and -0.0 are treated as the same value. E.g. starting from the
/// number just before -0.0, it only takes two increments to get to the
/// number just after 0.0.
/// - Infinity, NaN, and their negative counterparts are returned
/// unchanged.
/// - Incrementing `f32::MAX` results in infinity.
#[inline(always)]
pub fn increment_ulp(v: f32) -> f32 {
if v.is_finite() {
if v > 0.0 {
f32::from_bits(v.to_bits() + 1)
} else if v < -0.0 {
f32::from_bits(v.to_bits() - 1)
} else {
f32::from_bits(1)
}
} else {
// Infinity or NaN.
v
}
}
/// Decrements to the previous representable floating point number.
///
/// Notes:
/// - 0.0 and -0.0 are treated as the same value. E.g. starting from the
/// number just after 0.0, it only takes two decrements to get to the
/// number just before -0.0.
/// - Infinity, NaN, and their negative counterparts are returned
/// unchanged.
/// - Decrementing `-f32::MAX` results in -infinity.
#[inline(always)]
pub fn decrement_ulp(v: f32) -> f32 {
if v.is_finite() {
if v > 0.0 {
f32::from_bits(v.to_bits() - 1)
} else if v < -0.0 {
f32::from_bits(v.to_bits() + 1)
} else {
f32::from_bits(0x80000001)
}
} else {
// Infinity or NaN.
v
}
}
#[cfg(test)]
mod tests {
use super::*;
@ -93,4 +143,54 @@ mod tests {
assert!(!ulps_eq(std::f32::NAN, std::f32::INFINITY, 1 << 31));
assert!(!ulps_eq(std::f32::INFINITY, std::f32::NAN, 1 << 31));
}
#[test]
fn inc_ulp() {
assert!(increment_ulp(1.0) > 1.0);
assert!(increment_ulp(-1.0) > -1.0);
assert!(increment_ulp(0.0) > 0.0);
assert!(increment_ulp(0.0) > -0.0);
assert!(increment_ulp(-0.0) > 0.0);
assert!(increment_ulp(-0.0) > -0.0);
assert!(increment_ulp(f32::MAX) == f32::INFINITY);
assert!(increment_ulp(f32::INFINITY) == f32::INFINITY);
assert!(increment_ulp(-f32::INFINITY) == -f32::INFINITY);
assert!(increment_ulp(f32::NAN).is_nan());
assert!(increment_ulp(-f32::NAN).is_nan());
}
#[test]
fn dec_ulp() {
assert!(decrement_ulp(1.0) < 1.0);
assert!(decrement_ulp(-1.0) < -1.0);
assert!(decrement_ulp(0.0) < 0.0);
assert!(decrement_ulp(0.0) < -0.0);
assert!(decrement_ulp(-0.0) < 0.0);
assert!(decrement_ulp(-0.0) < -0.0);
assert!(decrement_ulp(f32::MIN) == -f32::INFINITY);
assert!(decrement_ulp(f32::INFINITY) == f32::INFINITY);
assert!(decrement_ulp(-f32::INFINITY) == -f32::INFINITY);
assert!(decrement_ulp(f32::NAN).is_nan());
assert!(decrement_ulp(-f32::NAN).is_nan());
}
#[test]
fn inc_dec_ulp() {
assert_eq!(decrement_ulp(increment_ulp(0.0)), 0.0);
assert_eq!(decrement_ulp(increment_ulp(-0.0)), 0.0);
assert_eq!(decrement_ulp(increment_ulp(1.0)), 1.0);
assert_eq!(decrement_ulp(increment_ulp(-1.0)), -1.0);
assert_eq!(decrement_ulp(increment_ulp(1.2)), 1.2);
assert_eq!(decrement_ulp(increment_ulp(-1.2)), -1.2);
}
#[test]
fn dec_inc_ulp() {
assert_eq!(increment_ulp(decrement_ulp(0.0)), 0.0);
assert_eq!(increment_ulp(decrement_ulp(-0.0)), 0.0);
assert_eq!(increment_ulp(decrement_ulp(1.0)), 1.0);
assert_eq!(increment_ulp(decrement_ulp(-1.0)), -1.0);
assert_eq!(increment_ulp(decrement_ulp(1.2)), 1.2);
assert_eq!(increment_ulp(decrement_ulp(-1.2)), -1.2);
}
}