Move ulp increment/decrement functions into rmath utils.

src/fp_utils.rs

@@ -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)]
+// #[cfg(test)]
-mod tests {
+// mod tests {
-    use super::*;
+//     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);
-    }
-}

sub_crates/rmath/src/utils.rs

@@ -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);
+    }
 }