Average Error: 0.1 → 0.1
Time: 5.4s
Precision: binary32
\[\left(0 \leq s \land s \leq 256\right) \land \left(10^{-6} < r \land r < 1000000\right)\]
\[\frac{0.25 \cdot e^{\frac{-r}{s}}}{\left(\left(2 \cdot \pi\right) \cdot s\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-r}{3 \cdot s}}}{\left(\left(6 \cdot \pi\right) \cdot s\right) \cdot r} \]
↓
\[\frac{0.25 \cdot e^{\frac{-r}{s}}}{\mathsf{expm1}\left(\mathsf{log1p}\left(s \cdot \left(r \cdot \left(2 \cdot \pi\right)\right)\right)\right)} + \frac{0.75 \cdot e^{\frac{-1}{s} \cdot \left(r \cdot 0.3333333333333333\right)}}{r \cdot \left(s \cdot \left(\pi \cdot 6\right)\right)} \]
(FPCore (s r)
 :precision binary32
 (+
  (/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 PI) s) r))
  (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* (* 6.0 PI) s) r))))
↓
(FPCore (s r)
 :precision binary32
 (+
  (/ (* 0.25 (exp (/ (- r) s))) (expm1 (log1p (* s (* r (* 2.0 PI))))))
  (/
   (* 0.75 (exp (* (/ -1.0 s) (* r 0.3333333333333333))))
   (* r (* s (* PI 6.0))))))
float code(float s, float r) {
	return ((0.25f * expf((-r / s))) / (((2.0f * ((float) M_PI)) * s) * r)) + ((0.75f * expf((-r / (3.0f * s)))) / (((6.0f * ((float) M_PI)) * s) * r));
}
↓
float code(float s, float r) {
	return ((0.25f * expf((-r / s))) / expm1f(log1pf((s * (r * (2.0f * ((float) M_PI))))))) + ((0.75f * expf(((-1.0f / s) * (r * 0.3333333333333333f)))) / (r * (s * (((float) M_PI) * 6.0f))));
}

function code(s, r)
	return Float32(Float32(Float32(Float32(0.25) * exp(Float32(Float32(-r) / s))) / Float32(Float32(Float32(Float32(2.0) * Float32(pi)) * s) * r)) + Float32(Float32(Float32(0.75) * exp(Float32(Float32(-r) / Float32(Float32(3.0) * s)))) / Float32(Float32(Float32(Float32(6.0) * Float32(pi)) * s) * r)))
end
↓
function code(s, r)
	return Float32(Float32(Float32(Float32(0.25) * exp(Float32(Float32(-r) / s))) / expm1(log1p(Float32(s * Float32(r * Float32(Float32(2.0) * Float32(pi))))))) + Float32(Float32(Float32(0.75) * exp(Float32(Float32(Float32(-1.0) / s) * Float32(r * Float32(0.3333333333333333))))) / Float32(r * Float32(s * Float32(Float32(pi) * Float32(6.0))))))
end

\frac{0.25 \cdot e^{\frac{-r}{s}}}{\left(\left(2 \cdot \pi\right) \cdot s\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-r}{3 \cdot s}}}{\left(\left(6 \cdot \pi\right) \cdot s\right) \cdot r}
↓
\frac{0.25 \cdot e^{\frac{-r}{s}}}{\mathsf{expm1}\left(\mathsf{log1p}\left(s \cdot \left(r \cdot \left(2 \cdot \pi\right)\right)\right)\right)} + \frac{0.75 \cdot e^{\frac{-1}{s} \cdot \left(r \cdot 0.3333333333333333\right)}}{r \cdot \left(s \cdot \left(\pi \cdot 6\right)\right)}

Error

Bits error versus s

Bits error versus r

Try it out

Your Program's Arguments

Results

Enter valid numbers for all inputs

Derivation

  1. Initial program 0.1

    \[\frac{0.25 \cdot e^{\frac{-r}{s}}}{\left(\left(2 \cdot \pi\right) \cdot s\right) \cdot r} + \frac{0.75 \cdot e^{\frac{-r}{3 \cdot s}}}{\left(\left(6 \cdot \pi\right) \cdot s\right) \cdot r} \]

  2. Applied egg-rr0.1

    \[\leadsto \frac{0.25 \cdot e^{\frac{-r}{s}}}{\left(\left(2 \cdot \pi\right) \cdot s\right) \cdot r} + \frac{0.75 \cdot e^{\color{blue}{\frac{-1}{s} \cdot \left(r \cdot 0.3333333333333333\right)}}}{\left(\left(6 \cdot \pi\right) \cdot s\right) \cdot r} \]

  3. Applied egg-rr0.1

    \[\leadsto \frac{0.25 \cdot e^{\frac{-r}{s}}}{\color{blue}{\mathsf{expm1}\left(\mathsf{log1p}\left(s \cdot \left(\left(2 \cdot \pi\right) \cdot r\right)\right)\right)}} + \frac{0.75 \cdot e^{\frac{-1}{s} \cdot \left(r \cdot 0.3333333333333333\right)}}{\left(\left(6 \cdot \pi\right) \cdot s\right) \cdot r} \]

  4. Final simplification0.1

    \[\leadsto \frac{0.25 \cdot e^{\frac{-r}{s}}}{\mathsf{expm1}\left(\mathsf{log1p}\left(s \cdot \left(r \cdot \left(2 \cdot \pi\right)\right)\right)\right)} + \frac{0.75 \cdot e^{\frac{-1}{s} \cdot \left(r \cdot 0.3333333333333333\right)}}{r \cdot \left(s \cdot \left(\pi \cdot 6\right)\right)} \]

Reproduce

herbie shell --seed 2022148 
(FPCore (s r)
  :name "Disney BSSRDF, PDF of scattering profile"
  :precision binary32
  :pre (and (and (<= 0.0 s) (<= s 256.0)) (and (< 1e-6 r) (< r 1000000.0)))
  (+ (/ (* 0.25 (exp (/ (- r) s))) (* (* (* 2.0 PI) s) r)) (/ (* 0.75 (exp (/ (- r) (* 3.0 s)))) (* (* (* 6.0 PI) s) r))))