Disney BSSRDF, sample scattering profile, upper

Percentage Accurate: 95.8% → 98.2%

Time: 10.2s

Alternatives: 5

Speedup: 1.0×

Specification

\[\left(0 \leq s \land s \leq 256\right) \land \left(0.25 \leq u \land u \leq 1\right)\]

Math

\[\begin{array}{l} \\ \left(3 \cdot s\right) \cdot \log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right) \end{array} \]

FPCore

(FPCore (s u)
 :precision binary32
 (* (* 3.0 s) (log (/ 1.0 (- 1.0 (/ (- u 0.25) 0.75))))))

C

float code(float s, float u) {
	return (3.0f * s) * logf((1.0f / (1.0f - ((u - 0.25f) / 0.75f))));
}

Fortran

real(4) function code(s, u)
    real(4), intent (in) :: s
    real(4), intent (in) :: u
    code = (3.0e0 * s) * log((1.0e0 / (1.0e0 - ((u - 0.25e0) / 0.75e0))))
end function

Julia

function code(s, u)
	return Float32(Float32(Float32(3.0) * s) * log(Float32(Float32(1.0) / Float32(Float32(1.0) - Float32(Float32(u - Float32(0.25)) / Float32(0.75))))))
end

MATLAB

function tmp = code(s, u)
	tmp = (single(3.0) * s) * log((single(1.0) / (single(1.0) - ((u - single(0.25)) / single(0.75)))));
end

Initial Program: 95.8% accurate, 1.0× speedup

Math

\[\begin{array}{l} \\ \left(3 \cdot s\right) \cdot \log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right) \end{array} \]

FPCore

(FPCore (s u)
 :precision binary32
 (* (* 3.0 s) (log (/ 1.0 (- 1.0 (/ (- u 0.25) 0.75))))))

C

float code(float s, float u) {
	return (3.0f * s) * logf((1.0f / (1.0f - ((u - 0.25f) / 0.75f))));
}

Fortran

real(4) function code(s, u)
    real(4), intent (in) :: s
    real(4), intent (in) :: u
    code = (3.0e0 * s) * log((1.0e0 / (1.0e0 - ((u - 0.25e0) / 0.75e0))))
end function

Julia

function code(s, u)
	return Float32(Float32(Float32(3.0) * s) * log(Float32(Float32(1.0) / Float32(Float32(1.0) - Float32(Float32(u - Float32(0.25)) / Float32(0.75))))))
end

MATLAB

function tmp = code(s, u)
	tmp = (single(3.0) * s) * log((single(1.0) / (single(1.0) - ((u - single(0.25)) / single(0.75)))));
end

Alternative 1: 98.2% accurate, 0.3× speedup

Math

\[\begin{array}{l} \\ \left(3 \cdot s\right) \cdot \left(\mathsf{log1p}\left(\mathsf{fma}\left(1.3333333333333333, u, -0.3333333333333333\right)\right) - \mathsf{log1p}\left(-1.7777777777777777 \cdot {\left(u + -0.25\right)}^{2}\right)\right) \end{array} \]

FPCore

(FPCore (s u)
 :precision binary32
 (*
  (* 3.0 s)
  (-
   (log1p (fma 1.3333333333333333 u -0.3333333333333333))
   (log1p (* -1.7777777777777777 (pow (+ u -0.25) 2.0))))))

C

float code(float s, float u) {
	return (3.0f * s) * (log1pf(fmaf(1.3333333333333333f, u, -0.3333333333333333f)) - log1pf((-1.7777777777777777f * powf((u + -0.25f), 2.0f))));
}

Julia

function code(s, u)
	return Float32(Float32(Float32(3.0) * s) * Float32(log1p(fma(Float32(1.3333333333333333), u, Float32(-0.3333333333333333))) - log1p(Float32(Float32(-1.7777777777777777) * (Float32(u + Float32(-0.25)) ^ Float32(2.0))))))
end

Derivation

1. Initial program 95.8%

   \[\left(3 \cdot s\right) \cdot \log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right) \]
2. Step-by-step derivation

   1. log-rec 96.4%

      \[\leadsto \left(3 \cdot s\right) \cdot \color{blue}{\left(-\log \left(1 - \frac{u - 0.25}{0.75}\right)\right)} \]

   2. sub-neg 96.4%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\log \color{blue}{\left(1 + \left(-\frac{u - 0.25}{0.75}\right)\right)}\right) \]

   3. log1p-def 98.2%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\color{blue}{\mathsf{log1p}\left(-\frac{u - 0.25}{0.75}\right)}\right) \]

   4. distribute-neg-frac 98.2%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\mathsf{log1p}\left(\color{blue}{\frac{-\left(u - 0.25\right)}{0.75}}\right)\right) \]

   5. sub-neg 98.2%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\mathsf{log1p}\left(\frac{-\color{blue}{\left(u + \left(-0.25\right)\right)}}{0.75}\right)\right) \]

   6. metadata-eval 98.2%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\mathsf{log1p}\left(\frac{-\left(u + \color{blue}{-0.25}\right)}{0.75}\right)\right) \]

3. Simplified 98.2%

   \[\leadsto \color{blue}{\left(3 \cdot s\right) \cdot \left(-\mathsf{log1p}\left(\frac{-\left(u + -0.25\right)}{0.75}\right)\right)} \]
4. Step-by-step derivation

   1. log1p-udef 96.4%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\color{blue}{\log \left(1 + \frac{-\left(u + -0.25\right)}{0.75}\right)}\right) \]

   2. metadata-eval 96.4%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\log \left(1 + \frac{-\left(u + \color{blue}{\left(-0.25\right)}\right)}{0.75}\right)\right) \]

   3. sub-neg 96.4%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\log \left(1 + \frac{-\color{blue}{\left(u - 0.25\right)}}{0.75}\right)\right) \]

   4. distribute-frac-neg 96.4%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\log \left(1 + \color{blue}{\left(-\frac{u - 0.25}{0.75}\right)}\right)\right) \]

   5. sub-neg 96.4%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\log \color{blue}{\left(1 - \frac{u - 0.25}{0.75}\right)}\right) \]

   6. flip-- 95.7%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\log \color{blue}{\left(\frac{1 \cdot 1 - \frac{u - 0.25}{0.75} \cdot \frac{u - 0.25}{0.75}}{1 + \frac{u - 0.25}{0.75}}\right)}\right) \]

   7. log-div 95.8%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\color{blue}{\left(\log \left(1 \cdot 1 - \frac{u - 0.25}{0.75} \cdot \frac{u - 0.25}{0.75}\right) - \log \left(1 + \frac{u - 0.25}{0.75}\right)\right)}\right) \]

5. Applied egg-rr 97.0%

   \[\leadsto \left(3 \cdot s\right) \cdot \left(-\color{blue}{\left(\log \left(1 - {\left(u + -0.25\right)}^{2} \cdot 1.7777777777777777\right) - \mathsf{log1p}\left(u \cdot 1.3333333333333333 + -0.3333333333333333\right)\right)}\right) \]
6. Step-by-step derivation

   1. sub-neg 97.0%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\left(\log \color{blue}{\left(1 + \left(-{\left(u + -0.25\right)}^{2} \cdot 1.7777777777777777\right)\right)} - \mathsf{log1p}\left(u \cdot 1.3333333333333333 + -0.3333333333333333\right)\right)\right) \]

   2. log1p-def 97.5%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\left(\color{blue}{\mathsf{log1p}\left(-{\left(u + -0.25\right)}^{2} \cdot 1.7777777777777777\right)} - \mathsf{log1p}\left(u \cdot 1.3333333333333333 + -0.3333333333333333\right)\right)\right) \]

   3. *-commutative 97.5%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\left(\mathsf{log1p}\left(-\color{blue}{1.7777777777777777 \cdot {\left(u + -0.25\right)}^{2}}\right) - \mathsf{log1p}\left(u \cdot 1.3333333333333333 + -0.3333333333333333\right)\right)\right) \]

   4. distribute-lft-neg-in 97.5%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\left(\mathsf{log1p}\left(\color{blue}{\left(-1.7777777777777777\right) \cdot {\left(u + -0.25\right)}^{2}}\right) - \mathsf{log1p}\left(u \cdot 1.3333333333333333 + -0.3333333333333333\right)\right)\right) \]

   5. metadata-eval 97.5%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\left(\mathsf{log1p}\left(\color{blue}{-1.7777777777777777} \cdot {\left(u + -0.25\right)}^{2}\right) - \mathsf{log1p}\left(u \cdot 1.3333333333333333 + -0.3333333333333333\right)\right)\right) \]

   6. *-commutative 97.5%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\left(\mathsf{log1p}\left(-1.7777777777777777 \cdot {\left(u + -0.25\right)}^{2}\right) - \mathsf{log1p}\left(\color{blue}{1.3333333333333333 \cdot u} + -0.3333333333333333\right)\right)\right) \]

   7. fma-def 98.3%

      \[\leadsto \left(3 \cdot s\right) \cdot \left(-\left(\mathsf{log1p}\left(-1.7777777777777777 \cdot {\left(u + -0.25\right)}^{2}\right) - \mathsf{log1p}\left(\color{blue}{\mathsf{fma}\left(1.3333333333333333, u, -0.3333333333333333\right)}\right)\right)\right) \]

7. Simplified 98.3%

   \[\leadsto \left(3 \cdot s\right) \cdot \left(-\color{blue}{\left(\mathsf{log1p}\left(-1.7777777777777777 \cdot {\left(u + -0.25\right)}^{2}\right) - \mathsf{log1p}\left(\mathsf{fma}\left(1.3333333333333333, u, -0.3333333333333333\right)\right)\right)}\right) \]

8. Final simplification 98.3%

   \[\leadsto \left(3 \cdot s\right) \cdot \left(\mathsf{log1p}\left(\mathsf{fma}\left(1.3333333333333333, u, -0.3333333333333333\right)\right) - \mathsf{log1p}\left(-1.7777777777777777 \cdot {\left(u + -0.25\right)}^{2}\right)\right) \]

Alternative 2: 96.2% accurate, 1.0× speedup

Math

\[\begin{array}{l} \\ -3 \cdot \left(s \cdot \log \left(1.3333333333333333 + u \cdot -1.3333333333333333\right)\right) \end{array} \]

FPCore

(FPCore (s u)
 :precision binary32
 (* -3.0 (* s (log (+ 1.3333333333333333 (* u -1.3333333333333333))))))

C

float code(float s, float u) {
	return -3.0f * (s * logf((1.3333333333333333f + (u * -1.3333333333333333f))));
}

Fortran

real(4) function code(s, u)
    real(4), intent (in) :: s
    real(4), intent (in) :: u
    code = (-3.0e0) * (s * log((1.3333333333333333e0 + (u * (-1.3333333333333333e0)))))
end function

Julia

function code(s, u)
	return Float32(Float32(-3.0) * Float32(s * log(Float32(Float32(1.3333333333333333) + Float32(u * Float32(-1.3333333333333333))))))
end

MATLAB

function tmp = code(s, u)
	tmp = single(-3.0) * (s * log((single(1.3333333333333333) + (u * single(-1.3333333333333333)))));
end

Derivation

1. Initial program 95.8%

   \[\left(3 \cdot s\right) \cdot \log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right) \]
2. Step-by-step derivation

   1. associate-*l* 95.9%

      \[\leadsto \color{blue}{3 \cdot \left(s \cdot \log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right)\right)} \]

   2. *-commutative 95.9%

      \[\leadsto \color{blue}{\left(s \cdot \log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right)\right) \cdot 3} \]

   3. associate-*l* 96.0%

      \[\leadsto \color{blue}{s \cdot \left(\log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right) \cdot 3\right)} \]

   4. log-rec 96.5%

      \[\leadsto s \cdot \left(\color{blue}{\left(-\log \left(1 - \frac{u - 0.25}{0.75}\right)\right)} \cdot 3\right) \]

   5. distribute-lft-neg-out 96.5%

      \[\leadsto s \cdot \color{blue}{\left(-\log \left(1 - \frac{u - 0.25}{0.75}\right) \cdot 3\right)} \]

   6. distribute-rgt-neg-in 96.5%

      \[\leadsto s \cdot \color{blue}{\left(\log \left(1 - \frac{u - 0.25}{0.75}\right) \cdot \left(-3\right)\right)} \]

   7. div-sub 95.4%

      \[\leadsto s \cdot \left(\log \left(1 - \color{blue}{\left(\frac{u}{0.75} - \frac{0.25}{0.75}\right)}\right) \cdot \left(-3\right)\right) \]

   8. associate--r- 95.4%

      \[\leadsto s \cdot \left(\log \color{blue}{\left(\left(1 - \frac{u}{0.75}\right) + \frac{0.25}{0.75}\right)} \cdot \left(-3\right)\right) \]

   9. sub-neg 95.4%

      \[\leadsto s \cdot \left(\log \left(\color{blue}{\left(1 + \left(-\frac{u}{0.75}\right)\right)} + \frac{0.25}{0.75}\right) \cdot \left(-3\right)\right) \]

   10. +-commutative 95.4%

       \[\leadsto s \cdot \left(\log \left(\color{blue}{\left(\left(-\frac{u}{0.75}\right) + 1\right)} + \frac{0.25}{0.75}\right) \cdot \left(-3\right)\right) \]

   11. associate-+l+ 94.4%

       \[\leadsto s \cdot \left(\log \color{blue}{\left(\left(-\frac{u}{0.75}\right) + \left(1 + \frac{0.25}{0.75}\right)\right)} \cdot \left(-3\right)\right) \]

   12. distribute-neg-frac 94.4%

       \[\leadsto s \cdot \left(\log \left(\color{blue}{\frac{-u}{0.75}} + \left(1 + \frac{0.25}{0.75}\right)\right) \cdot \left(-3\right)\right) \]

   13. neg-mul-1 94.4%

       \[\leadsto s \cdot \left(\log \left(\frac{\color{blue}{-1 \cdot u}}{0.75} + \left(1 + \frac{0.25}{0.75}\right)\right) \cdot \left(-3\right)\right) \]

   14. associate-/l* 94.2%

       \[\leadsto s \cdot \left(\log \left(\color{blue}{\frac{-1}{\frac{0.75}{u}}} + \left(1 + \frac{0.25}{0.75}\right)\right) \cdot \left(-3\right)\right) \]

   15. associate-/r/ 95.9%

       \[\leadsto s \cdot \left(\log \left(\color{blue}{\frac{-1}{0.75} \cdot u} + \left(1 + \frac{0.25}{0.75}\right)\right) \cdot \left(-3\right)\right) \]

   16. metadata-eval 95.9%

       \[\leadsto s \cdot \left(\log \left(\color{blue}{-1.3333333333333333} \cdot u + \left(1 + \frac{0.25}{0.75}\right)\right) \cdot \left(-3\right)\right) \]

   17. metadata-eval 95.9%

       \[\leadsto s \cdot \left(\log \left(-1.3333333333333333 \cdot u + \left(1 + \color{blue}{0.3333333333333333}\right)\right) \cdot \left(-3\right)\right) \]

   18. metadata-eval 95.9%

       \[\leadsto s \cdot \left(\log \left(-1.3333333333333333 \cdot u + \color{blue}{1.3333333333333333}\right) \cdot \left(-3\right)\right) \]

   19. metadata-eval 95.9%

       \[\leadsto s \cdot \left(\log \left(-1.3333333333333333 \cdot u + 1.3333333333333333\right) \cdot \color{blue}{-3}\right) \]

3. Simplified 95.9%

   \[\leadsto \color{blue}{s \cdot \left(\log \left(-1.3333333333333333 \cdot u + 1.3333333333333333\right) \cdot -3\right)} \]

4. Taylor expanded in u around inf 95.9%

   \[\leadsto s \cdot \left(\log \color{blue}{\left(1.3333333333333333 + -1.3333333333333333 \cdot u\right)} \cdot -3\right) \]
5. Step-by-step derivation

   1. +-commutative 95.9%

      \[\leadsto s \cdot \left(\log \color{blue}{\left(-1.3333333333333333 \cdot u + 1.3333333333333333\right)} \cdot -3\right) \]

   2. *-commutative 95.9%

      \[\leadsto s \cdot \left(\log \left(\color{blue}{u \cdot -1.3333333333333333} + 1.3333333333333333\right) \cdot -3\right) \]

   3. fma-udef 96.5%

      \[\leadsto s \cdot \left(\log \color{blue}{\left(\mathsf{fma}\left(u, -1.3333333333333333, 1.3333333333333333\right)\right)} \cdot -3\right) \]

6. Simplified 96.5%

   \[\leadsto s \cdot \left(\log \color{blue}{\left(\mathsf{fma}\left(u, -1.3333333333333333, 1.3333333333333333\right)\right)} \cdot -3\right) \]

7. Taylor expanded in s around 0 95.9%

   \[\leadsto \color{blue}{-3 \cdot \left(s \cdot \log \left(1.3333333333333333 + -1.3333333333333333 \cdot u\right)\right)} \]

8. Final simplification 95.9%

   \[\leadsto -3 \cdot \left(s \cdot \log \left(1.3333333333333333 + u \cdot -1.3333333333333333\right)\right) \]

Alternative 3: 97.8% accurate, 1.0× speedup

Math

\[\begin{array}{l} \\ -3 \cdot \left(s \cdot \mathsf{log1p}\left(1.3333333333333333 \cdot \left(0.25 - u\right)\right)\right) \end{array} \]

FPCore

(FPCore (s u)
 :precision binary32
 (* -3.0 (* s (log1p (* 1.3333333333333333 (- 0.25 u))))))

C

float code(float s, float u) {
	return -3.0f * (s * log1pf((1.3333333333333333f * (0.25f - u))));
}

Julia

function code(s, u)
	return Float32(Float32(-3.0) * Float32(s * log1p(Float32(Float32(1.3333333333333333) * Float32(Float32(0.25) - u)))))
end

Derivation

1. Initial program 95.8%

   \[\left(3 \cdot s\right) \cdot \log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right) \]
2. Step-by-step derivation

   1. associate-*l* 95.9%

      \[\leadsto \color{blue}{3 \cdot \left(s \cdot \log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right)\right)} \]

   2. *-commutative 95.9%

      \[\leadsto \color{blue}{\left(s \cdot \log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right)\right) \cdot 3} \]

   3. associate-*l* 96.0%

      \[\leadsto \color{blue}{s \cdot \left(\log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right) \cdot 3\right)} \]

   4. log-rec 96.5%

      \[\leadsto s \cdot \left(\color{blue}{\left(-\log \left(1 - \frac{u - 0.25}{0.75}\right)\right)} \cdot 3\right) \]

   5. distribute-lft-neg-out 96.5%

      \[\leadsto s \cdot \color{blue}{\left(-\log \left(1 - \frac{u - 0.25}{0.75}\right) \cdot 3\right)} \]

   6. distribute-rgt-neg-in 96.5%

      \[\leadsto s \cdot \color{blue}{\left(\log \left(1 - \frac{u - 0.25}{0.75}\right) \cdot \left(-3\right)\right)} \]

   7. sub-neg 96.5%

      \[\leadsto s \cdot \left(\log \color{blue}{\left(1 + \left(-\frac{u - 0.25}{0.75}\right)\right)} \cdot \left(-3\right)\right) \]

   8. log1p-def 98.2%

      \[\leadsto s \cdot \left(\color{blue}{\mathsf{log1p}\left(-\frac{u - 0.25}{0.75}\right)} \cdot \left(-3\right)\right) \]

   9. distribute-neg-frac 98.2%

      \[\leadsto s \cdot \left(\mathsf{log1p}\left(\color{blue}{\frac{-\left(u - 0.25\right)}{0.75}}\right) \cdot \left(-3\right)\right) \]

   10. sub-neg 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{-\color{blue}{\left(u + \left(-0.25\right)\right)}}{0.75}\right) \cdot \left(-3\right)\right) \]

   11. +-commutative 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{-\color{blue}{\left(\left(-0.25\right) + u\right)}}{0.75}\right) \cdot \left(-3\right)\right) \]

   12. distribute-neg-in 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{\color{blue}{\left(-\left(-0.25\right)\right) + \left(-u\right)}}{0.75}\right) \cdot \left(-3\right)\right) \]

   13. metadata-eval 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{\left(-\color{blue}{-0.25}\right) + \left(-u\right)}{0.75}\right) \cdot \left(-3\right)\right) \]

   14. metadata-eval 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{\color{blue}{0.25} + \left(-u\right)}{0.75}\right) \cdot \left(-3\right)\right) \]

   15. unsub-neg 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{\color{blue}{0.25 - u}}{0.75}\right) \cdot \left(-3\right)\right) \]

   16. metadata-eval 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{0.25 - u}{0.75}\right) \cdot \color{blue}{-3}\right) \]

3. Simplified 98.2%

   \[\leadsto \color{blue}{s \cdot \left(\mathsf{log1p}\left(\frac{0.25 - u}{0.75}\right) \cdot -3\right)} \]

4. Taylor expanded in s around 0 96.2%

   \[\leadsto \color{blue}{-3 \cdot \left(s \cdot \log \left(1 + 1.3333333333333333 \cdot \left(0.25 - u\right)\right)\right)} \]
5. Step-by-step derivation

   1. log1p-def 97.9%

      \[\leadsto -3 \cdot \left(s \cdot \color{blue}{\mathsf{log1p}\left(1.3333333333333333 \cdot \left(0.25 - u\right)\right)}\right) \]

6. Simplified 97.9%

   \[\leadsto \color{blue}{-3 \cdot \left(s \cdot \mathsf{log1p}\left(1.3333333333333333 \cdot \left(0.25 - u\right)\right)\right)} \]

7. Final simplification 97.9%

   \[\leadsto -3 \cdot \left(s \cdot \mathsf{log1p}\left(1.3333333333333333 \cdot \left(0.25 - u\right)\right)\right) \]

Alternative 4: 98.3% accurate, 1.0× speedup

Math

\[\begin{array}{l} \\ s \cdot \left(\mathsf{log1p}\left(\frac{0.25 - u}{0.75}\right) \cdot -3\right) \end{array} \]

FPCore

(FPCore (s u) :precision binary32 (* s (* (log1p (/ (- 0.25 u) 0.75)) -3.0)))

C

float code(float s, float u) {
	return s * (log1pf(((0.25f - u) / 0.75f)) * -3.0f);
}

Julia

function code(s, u)
	return Float32(s * Float32(log1p(Float32(Float32(Float32(0.25) - u) / Float32(0.75))) * Float32(-3.0)))
end

Derivation

1. Initial program 95.8%

   \[\left(3 \cdot s\right) \cdot \log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right) \]
2. Step-by-step derivation

   1. associate-*l* 95.9%

      \[\leadsto \color{blue}{3 \cdot \left(s \cdot \log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right)\right)} \]

   2. *-commutative 95.9%

      \[\leadsto \color{blue}{\left(s \cdot \log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right)\right) \cdot 3} \]

   3. associate-*l* 96.0%

      \[\leadsto \color{blue}{s \cdot \left(\log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right) \cdot 3\right)} \]

   4. log-rec 96.5%

      \[\leadsto s \cdot \left(\color{blue}{\left(-\log \left(1 - \frac{u - 0.25}{0.75}\right)\right)} \cdot 3\right) \]

   5. distribute-lft-neg-out 96.5%

      \[\leadsto s \cdot \color{blue}{\left(-\log \left(1 - \frac{u - 0.25}{0.75}\right) \cdot 3\right)} \]

   6. distribute-rgt-neg-in 96.5%

      \[\leadsto s \cdot \color{blue}{\left(\log \left(1 - \frac{u - 0.25}{0.75}\right) \cdot \left(-3\right)\right)} \]

   7. sub-neg 96.5%

      \[\leadsto s \cdot \left(\log \color{blue}{\left(1 + \left(-\frac{u - 0.25}{0.75}\right)\right)} \cdot \left(-3\right)\right) \]

   8. log1p-def 98.2%

      \[\leadsto s \cdot \left(\color{blue}{\mathsf{log1p}\left(-\frac{u - 0.25}{0.75}\right)} \cdot \left(-3\right)\right) \]

   9. distribute-neg-frac 98.2%

      \[\leadsto s \cdot \left(\mathsf{log1p}\left(\color{blue}{\frac{-\left(u - 0.25\right)}{0.75}}\right) \cdot \left(-3\right)\right) \]

   10. sub-neg 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{-\color{blue}{\left(u + \left(-0.25\right)\right)}}{0.75}\right) \cdot \left(-3\right)\right) \]

   11. +-commutative 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{-\color{blue}{\left(\left(-0.25\right) + u\right)}}{0.75}\right) \cdot \left(-3\right)\right) \]

   12. distribute-neg-in 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{\color{blue}{\left(-\left(-0.25\right)\right) + \left(-u\right)}}{0.75}\right) \cdot \left(-3\right)\right) \]

   13. metadata-eval 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{\left(-\color{blue}{-0.25}\right) + \left(-u\right)}{0.75}\right) \cdot \left(-3\right)\right) \]

   14. metadata-eval 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{\color{blue}{0.25} + \left(-u\right)}{0.75}\right) \cdot \left(-3\right)\right) \]

   15. unsub-neg 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{\color{blue}{0.25 - u}}{0.75}\right) \cdot \left(-3\right)\right) \]

   16. metadata-eval 98.2%

       \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{0.25 - u}{0.75}\right) \cdot \color{blue}{-3}\right) \]

3. Simplified 98.2%

   \[\leadsto \color{blue}{s \cdot \left(\mathsf{log1p}\left(\frac{0.25 - u}{0.75}\right) \cdot -3\right)} \]

4. Final simplification 98.2%

   \[\leadsto s \cdot \left(\mathsf{log1p}\left(\frac{0.25 - u}{0.75}\right) \cdot -3\right) \]

Alternative 5: 29.9% accurate, 22.6× speedup

Math

\[\begin{array}{l} \\ 3 \cdot \left(s \cdot u\right) \end{array} \]

FPCore

(FPCore (s u) :precision binary32 (* 3.0 (* s u)))

C

float code(float s, float u) {
	return 3.0f * (s * u);
}

Fortran

real(4) function code(s, u)
    real(4), intent (in) :: s
    real(4), intent (in) :: u
    code = 3.0e0 * (s * u)
end function

Julia

function code(s, u)
	return Float32(Float32(3.0) * Float32(s * u))
end

MATLAB

function tmp = code(s, u)
	tmp = single(3.0) * (s * u);
end

Derivation

1. Initial program 95.8%

   \[\left(3 \cdot s\right) \cdot \log \left(\frac{1}{1 - \frac{u - 0.25}{0.75}}\right) \]

2. Taylor expanded in u around 0 25.9%

   \[\leadsto \left(3 \cdot s\right) \cdot \color{blue}{\left(\log 0.75 + u\right)} \]

3. Taylor expanded in u around inf 30.5%

   \[\leadsto \color{blue}{3 \cdot \left(s \cdot u\right)} \]

4. Final simplification 30.5%

   \[\leadsto 3 \cdot \left(s \cdot u\right) \]

Reproduce

herbie shell --seed 2023238 
(FPCore (s u)
  :name "Disney BSSRDF, sample scattering profile, upper"
  :precision binary32
  :pre (and (and (<= 0.0 s) (<= s 256.0)) (and (<= 0.25 u) (<= u 1.0)))
  (* (* 3.0 s) (log (/ 1.0 (- 1.0 (/ (- u 0.25) 0.75))))))