Disney BSSRDF, sample scattering profile, upper

Percentage Accurate: 95.9% → 97.9%

Time: 6.0s

Alternatives: 4

Speedup: 1.2×

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

module fmin_fmax_functions
    implicit none
    private
    public fmax
    public fmin

    interface fmax
        module procedure fmax88
        module procedure fmax44
        module procedure fmax84
        module procedure fmax48
    end interface
    interface fmin
        module procedure fmin88
        module procedure fmin44
        module procedure fmin84
        module procedure fmin48
    end interface
contains
    real(8) function fmax88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(4) function fmax44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(8) function fmax84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, max(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmax48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), max(dble(x), y), y /= y), x /= x)
    end function
    real(8) function fmin88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(4) function fmin44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(8) function fmin84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, min(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmin48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), min(dble(x), y), y /= y), x /= x)
    end function
end module

real(4) function code(s, u)
use fmin_fmax_functions
    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: 95.9% 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

module fmin_fmax_functions
    implicit none
    private
    public fmax
    public fmin

    interface fmax
        module procedure fmax88
        module procedure fmax44
        module procedure fmax84
        module procedure fmax48
    end interface
    interface fmin
        module procedure fmin88
        module procedure fmin44
        module procedure fmin84
        module procedure fmin48
    end interface
contains
    real(8) function fmax88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(4) function fmax44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(8) function fmax84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, max(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmax48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), max(dble(x), y), y /= y), x /= x)
    end function
    real(8) function fmin88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(4) function fmin44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(8) function fmin84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, min(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmin48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), min(dble(x), y), y /= y), x /= x)
    end function
end module

real(4) function code(s, u)
use fmin_fmax_functions
    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: 97.9% accurate, 1.2× speedup

Math

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

FPCore

(FPCore (s u)
 :precision binary32
 (* (* (log1p (fma -1.3333333333333333 u 0.3333333333333333)) -3.0) s))

C

float code(float s, float u) {
	return (log1pf(fmaf(-1.3333333333333333f, u, 0.3333333333333333f)) * -3.0f) * s;
}

Julia

function code(s, u)
	return Float32(Float32(log1p(fma(Float32(-1.3333333333333333), u, Float32(0.3333333333333333))) * Float32(-3.0)) * s)
end

Derivation

1. Initial program 95.9%

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

3. Taylor expanded in s around 0

   \[\leadsto \color{blue}{3 \cdot \left(s \cdot \log \left(\frac{1}{1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)}\right)\right)} \]
4. Step-by-step derivation

   1. associate-*r* N/A

      \[\leadsto \color{blue}{\left(3 \cdot s\right) \cdot \log \left(\frac{1}{1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)}\right)} \]

   2. log-rec N/A

      \[\leadsto \left(3 \cdot s\right) \cdot \color{blue}{\left(\mathsf{neg}\left(\log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right)\right)\right)} \]

   3. distribute-rgt-neg-out N/A

      \[\leadsto \color{blue}{\mathsf{neg}\left(\left(3 \cdot s\right) \cdot \log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right)\right)} \]

   4. distribute-lft-neg-in N/A

      \[\leadsto \color{blue}{\left(\mathsf{neg}\left(3 \cdot s\right)\right) \cdot \log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right)} \]

   5. distribute-lft-neg-out N/A

      \[\leadsto \color{blue}{\left(\left(\mathsf{neg}\left(3\right)\right) \cdot s\right)} \cdot \log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right) \]

   6. metadata-eval N/A

      \[\leadsto \left(\color{blue}{-3} \cdot s\right) \cdot \log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right) \]

   7. lower-*.f32 N/A

      \[\leadsto \color{blue}{\left(-3 \cdot s\right) \cdot \log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right)} \]

   8. lower-*.f32 N/A

      \[\leadsto \color{blue}{\left(-3 \cdot s\right)} \cdot \log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right) \]

   9. fp-cancel-sub-sign-inv N/A

      \[\leadsto \left(-3 \cdot s\right) \cdot \log \color{blue}{\left(1 + \left(\mathsf{neg}\left(\frac{4}{3}\right)\right) \cdot \left(u - \frac{1}{4}\right)\right)} \]

   10. lower-log1p.f32 N/A

       \[\leadsto \left(-3 \cdot s\right) \cdot \color{blue}{\mathsf{log1p}\left(\left(\mathsf{neg}\left(\frac{4}{3}\right)\right) \cdot \left(u - \frac{1}{4}\right)\right)} \]

   11. metadata-eval N/A

       \[\leadsto \left(-3 \cdot s\right) \cdot \mathsf{log1p}\left(\color{blue}{\frac{-4}{3}} \cdot \left(u - \frac{1}{4}\right)\right) \]

   12. lower-*.f32 N/A

       \[\leadsto \left(-3 \cdot s\right) \cdot \mathsf{log1p}\left(\color{blue}{\frac{-4}{3} \cdot \left(u - \frac{1}{4}\right)}\right) \]

   13. lower--.f32 97.8

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

5. Applied rewrites 97.8%

   \[\leadsto \color{blue}{\left(-3 \cdot s\right) \cdot \mathsf{log1p}\left(-1.3333333333333333 \cdot \left(u - 0.25\right)\right)} \]
6. Step-by-step derivation

7. Applied rewrites 97.9%

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

8. Taylor expanded in u around 0

   \[\leadsto \left(\mathsf{log1p}\left(\frac{1}{3} + \frac{-4}{3} \cdot u\right) \cdot -3\right) \cdot s \]
9. Step-by-step derivation

10. Applied rewrites 97.9%

    \[\leadsto \left(\mathsf{log1p}\left(\mathsf{fma}\left(-1.3333333333333333, u, 0.3333333333333333\right)\right) \cdot -3\right) \cdot s \]
11. Add Preprocessing

Alternative 2: 97.9% accurate, 1.2× speedup

Math

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

FPCore

(FPCore (s u)
 :precision binary32
 (* (* -3.0 s) (log1p (fma -1.3333333333333333 u 0.3333333333333333))))

C

float code(float s, float u) {
	return (-3.0f * s) * log1pf(fmaf(-1.3333333333333333f, u, 0.3333333333333333f));
}

Julia

function code(s, u)
	return Float32(Float32(Float32(-3.0) * s) * log1p(fma(Float32(-1.3333333333333333), u, Float32(0.3333333333333333))))
end

Derivation

1. Initial program 95.9%

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

3. Taylor expanded in s around 0

   \[\leadsto \color{blue}{3 \cdot \left(s \cdot \log \left(\frac{1}{1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)}\right)\right)} \]
4. Step-by-step derivation

   1. associate-*r* N/A

      \[\leadsto \color{blue}{\left(3 \cdot s\right) \cdot \log \left(\frac{1}{1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)}\right)} \]

   2. log-rec N/A

      \[\leadsto \left(3 \cdot s\right) \cdot \color{blue}{\left(\mathsf{neg}\left(\log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right)\right)\right)} \]

   3. distribute-rgt-neg-out N/A

      \[\leadsto \color{blue}{\mathsf{neg}\left(\left(3 \cdot s\right) \cdot \log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right)\right)} \]

   4. distribute-lft-neg-in N/A

      \[\leadsto \color{blue}{\left(\mathsf{neg}\left(3 \cdot s\right)\right) \cdot \log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right)} \]

   5. distribute-lft-neg-out N/A

      \[\leadsto \color{blue}{\left(\left(\mathsf{neg}\left(3\right)\right) \cdot s\right)} \cdot \log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right) \]

   6. metadata-eval N/A

      \[\leadsto \left(\color{blue}{-3} \cdot s\right) \cdot \log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right) \]

   7. lower-*.f32 N/A

      \[\leadsto \color{blue}{\left(-3 \cdot s\right) \cdot \log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right)} \]

   8. lower-*.f32 N/A

      \[\leadsto \color{blue}{\left(-3 \cdot s\right)} \cdot \log \left(1 - \frac{4}{3} \cdot \left(u - \frac{1}{4}\right)\right) \]

   9. fp-cancel-sub-sign-inv N/A

      \[\leadsto \left(-3 \cdot s\right) \cdot \log \color{blue}{\left(1 + \left(\mathsf{neg}\left(\frac{4}{3}\right)\right) \cdot \left(u - \frac{1}{4}\right)\right)} \]

   10. lower-log1p.f32 N/A

       \[\leadsto \left(-3 \cdot s\right) \cdot \color{blue}{\mathsf{log1p}\left(\left(\mathsf{neg}\left(\frac{4}{3}\right)\right) \cdot \left(u - \frac{1}{4}\right)\right)} \]

   11. metadata-eval N/A

       \[\leadsto \left(-3 \cdot s\right) \cdot \mathsf{log1p}\left(\color{blue}{\frac{-4}{3}} \cdot \left(u - \frac{1}{4}\right)\right) \]

   12. lower-*.f32 N/A

       \[\leadsto \left(-3 \cdot s\right) \cdot \mathsf{log1p}\left(\color{blue}{\frac{-4}{3} \cdot \left(u - \frac{1}{4}\right)}\right) \]

   13. lower--.f32 97.8

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

5. Applied rewrites 97.8%

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

6. Taylor expanded in u around 0

   \[\leadsto \left(-3 \cdot s\right) \cdot \mathsf{log1p}\left(\frac{1}{3} + \frac{-4}{3} \cdot u\right) \]
7. Step-by-step derivation

8. Applied rewrites 97.8%

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

9. Final simplification 97.8%

   \[\leadsto \left(-3 \cdot s\right) \cdot \mathsf{log1p}\left(\mathsf{fma}\left(-1.3333333333333333, u, 0.3333333333333333\right)\right) \]
10. Add Preprocessing

Alternative 3: 25.7% accurate, 1.2× speedup

Math

\[\begin{array}{l} \\ \mathsf{fma}\left(u, 3, \log 0.421875\right) \cdot s \end{array} \]

FPCore

(FPCore (s u) :precision binary32 (* (fma u 3.0 (log 0.421875)) s))

C

float code(float s, float u) {
	return fmaf(u, 3.0f, logf(0.421875f)) * s;
}

Julia

function code(s, u)
	return Float32(fma(u, Float32(3.0), log(Float32(0.421875))) * s)
end

Derivation

1. Initial program 95.9%

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

   1. lift-*.f32 N/A

      \[\leadsto \color{blue}{\left(3 \cdot s\right) \cdot \log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)} \]

   2. *-commutative N/A

      \[\leadsto \color{blue}{\log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right) \cdot \left(3 \cdot s\right)} \]

   3. lift-*.f32 N/A

      \[\leadsto \log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right) \cdot \color{blue}{\left(3 \cdot s\right)} \]

   4. associate-*r* N/A

      \[\leadsto \color{blue}{\left(\log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right) \cdot 3\right) \cdot s} \]

   5. lower-*.f32 N/A

      \[\leadsto \color{blue}{\left(\log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right) \cdot 3\right) \cdot s} \]

   6. lower-*.f32 95.8

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

   7. lift-log.f32 N/A

      \[\leadsto \left(\color{blue}{\log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)} \cdot 3\right) \cdot s \]

   8. lift-/.f32 N/A

      \[\leadsto \left(\log \color{blue}{\left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)} \cdot 3\right) \cdot s \]

   9. log-rec N/A

      \[\leadsto \left(\color{blue}{\left(\mathsf{neg}\left(\log \left(1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}\right)\right)\right)} \cdot 3\right) \cdot s \]

   10. lower-neg.f32 N/A

       \[\leadsto \left(\color{blue}{\left(-\log \left(1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}\right)\right)} \cdot 3\right) \cdot s \]

   11. lower-log.f32 96.6

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

4. Applied rewrites 96.6%

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

   1. lift-*.f32 N/A

      \[\leadsto \color{blue}{\left(\left(-\log \left(1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}\right)\right) \cdot 3\right)} \cdot s \]

   2. *-commutative N/A

      \[\leadsto \color{blue}{\left(3 \cdot \left(-\log \left(1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}\right)\right)\right)} \cdot s \]

   3. lift-neg.f32 N/A

      \[\leadsto \left(3 \cdot \color{blue}{\left(\mathsf{neg}\left(\log \left(1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}\right)\right)\right)}\right) \cdot s \]

   4. lift-log.f32 N/A

      \[\leadsto \left(3 \cdot \left(\mathsf{neg}\left(\color{blue}{\log \left(1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}\right)}\right)\right)\right) \cdot s \]

   5. neg-log N/A

      \[\leadsto \left(3 \cdot \color{blue}{\log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)}\right) \cdot s \]

   6. lift--.f32 N/A

      \[\leadsto \left(3 \cdot \log \left(\frac{1}{\color{blue}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}}\right)\right) \cdot s \]

   7. lift-/.f32 N/A

      \[\leadsto \left(3 \cdot \log \left(\frac{1}{1 - \color{blue}{\frac{u - \frac{1}{4}}{\frac{3}{4}}}}\right)\right) \cdot s \]

   8. lift--.f32 N/A

      \[\leadsto \left(3 \cdot \log \left(\frac{1}{1 - \frac{\color{blue}{u - \frac{1}{4}}}{\frac{3}{4}}}\right)\right) \cdot s \]

   9. log-pow-rev N/A

      \[\leadsto \color{blue}{\log \left({\left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)}^{3}\right)} \cdot s \]

   10. lower-log.f32 N/A

       \[\leadsto \color{blue}{\log \left({\left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)}^{3}\right)} \cdot s \]

   11. lower-pow.f32 N/A

       \[\leadsto \log \color{blue}{\left({\left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)}^{3}\right)} \cdot s \]

   12. lift--.f32 N/A

       \[\leadsto \log \left({\left(\frac{1}{1 - \frac{\color{blue}{u - \frac{1}{4}}}{\frac{3}{4}}}\right)}^{3}\right) \cdot s \]

   13. lift-/.f32 N/A

       \[\leadsto \log \left({\left(\frac{1}{1 - \color{blue}{\frac{u - \frac{1}{4}}{\frac{3}{4}}}}\right)}^{3}\right) \cdot s \]

   14. lift--.f32 N/A

       \[\leadsto \log \left({\left(\frac{1}{\color{blue}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}}\right)}^{3}\right) \cdot s \]

   15. lower-/.f32 95.9

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

6. Applied rewrites 95.9%

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

7. Taylor expanded in u around 0

   \[\leadsto \color{blue}{\left(\log \frac{27}{64} + 3 \cdot u\right)} \cdot s \]
8. Step-by-step derivation

   1. +-commutative N/A

      \[\leadsto \color{blue}{\left(3 \cdot u + \log \frac{27}{64}\right)} \cdot s \]

   2. *-commutative N/A

      \[\leadsto \left(\color{blue}{u \cdot 3} + \log \frac{27}{64}\right) \cdot s \]

   3. lower-fma.f32 N/A

      \[\leadsto \color{blue}{\mathsf{fma}\left(u, 3, \log \frac{27}{64}\right)} \cdot s \]

   4. lower-log.f32 26.1

      \[\leadsto \mathsf{fma}\left(u, 3, \color{blue}{\log 0.421875}\right) \cdot s \]

9. Applied rewrites 26.1%

   \[\leadsto \color{blue}{\mathsf{fma}\left(u, 3, \log 0.421875\right)} \cdot s \]
10. Add Preprocessing

Alternative 4: 7.3% accurate, 1.3× speedup

Math

\[\begin{array}{l} \\ \log 0.421875 \cdot s \end{array} \]

FPCore

(FPCore (s u) :precision binary32 (* (log 0.421875) s))

C

float code(float s, float u) {
	return logf(0.421875f) * s;
}

Fortran

module fmin_fmax_functions
    implicit none
    private
    public fmax
    public fmin

    interface fmax
        module procedure fmax88
        module procedure fmax44
        module procedure fmax84
        module procedure fmax48
    end interface
    interface fmin
        module procedure fmin88
        module procedure fmin44
        module procedure fmin84
        module procedure fmin48
    end interface
contains
    real(8) function fmax88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(4) function fmax44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, max(x, y), y /= y), x /= x)
    end function
    real(8) function fmax84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, max(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmax48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), max(dble(x), y), y /= y), x /= x)
    end function
    real(8) function fmin88(x, y) result (res)
        real(8), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(4) function fmin44(x, y) result (res)
        real(4), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(y, merge(x, min(x, y), y /= y), x /= x)
    end function
    real(8) function fmin84(x, y) result(res)
        real(8), intent (in) :: x
        real(4), intent (in) :: y
        res = merge(dble(y), merge(x, min(x, dble(y)), y /= y), x /= x)
    end function
    real(8) function fmin48(x, y) result(res)
        real(4), intent (in) :: x
        real(8), intent (in) :: y
        res = merge(y, merge(dble(x), min(dble(x), y), y /= y), x /= x)
    end function
end module

real(4) function code(s, u)
use fmin_fmax_functions
    real(4), intent (in) :: s
    real(4), intent (in) :: u
    code = log(0.421875e0) * s
end function

Julia

function code(s, u)
	return Float32(log(Float32(0.421875)) * s)
end

MATLAB

function tmp = code(s, u)
	tmp = log(single(0.421875)) * s;
end

Derivation

1. Initial program 95.9%

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

   1. lift-*.f32 N/A

      \[\leadsto \color{blue}{\left(3 \cdot s\right) \cdot \log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)} \]

   2. *-commutative N/A

      \[\leadsto \color{blue}{\log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right) \cdot \left(3 \cdot s\right)} \]

   3. lift-*.f32 N/A

      \[\leadsto \log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right) \cdot \color{blue}{\left(3 \cdot s\right)} \]

   4. associate-*r* N/A

      \[\leadsto \color{blue}{\left(\log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right) \cdot 3\right) \cdot s} \]

   5. lower-*.f32 N/A

      \[\leadsto \color{blue}{\left(\log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right) \cdot 3\right) \cdot s} \]

   6. lower-*.f32 95.8

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

   7. lift-log.f32 N/A

      \[\leadsto \left(\color{blue}{\log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)} \cdot 3\right) \cdot s \]

   8. lift-/.f32 N/A

      \[\leadsto \left(\log \color{blue}{\left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)} \cdot 3\right) \cdot s \]

   9. log-rec N/A

      \[\leadsto \left(\color{blue}{\left(\mathsf{neg}\left(\log \left(1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}\right)\right)\right)} \cdot 3\right) \cdot s \]

   10. lower-neg.f32 N/A

       \[\leadsto \left(\color{blue}{\left(-\log \left(1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}\right)\right)} \cdot 3\right) \cdot s \]

   11. lower-log.f32 96.6

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

4. Applied rewrites 96.6%

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

   1. lift-*.f32 N/A

      \[\leadsto \color{blue}{\left(\left(-\log \left(1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}\right)\right) \cdot 3\right)} \cdot s \]

   2. *-commutative N/A

      \[\leadsto \color{blue}{\left(3 \cdot \left(-\log \left(1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}\right)\right)\right)} \cdot s \]

   3. lift-neg.f32 N/A

      \[\leadsto \left(3 \cdot \color{blue}{\left(\mathsf{neg}\left(\log \left(1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}\right)\right)\right)}\right) \cdot s \]

   4. lift-log.f32 N/A

      \[\leadsto \left(3 \cdot \left(\mathsf{neg}\left(\color{blue}{\log \left(1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}\right)}\right)\right)\right) \cdot s \]

   5. neg-log N/A

      \[\leadsto \left(3 \cdot \color{blue}{\log \left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)}\right) \cdot s \]

   6. lift--.f32 N/A

      \[\leadsto \left(3 \cdot \log \left(\frac{1}{\color{blue}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}}\right)\right) \cdot s \]

   7. lift-/.f32 N/A

      \[\leadsto \left(3 \cdot \log \left(\frac{1}{1 - \color{blue}{\frac{u - \frac{1}{4}}{\frac{3}{4}}}}\right)\right) \cdot s \]

   8. lift--.f32 N/A

      \[\leadsto \left(3 \cdot \log \left(\frac{1}{1 - \frac{\color{blue}{u - \frac{1}{4}}}{\frac{3}{4}}}\right)\right) \cdot s \]

   9. log-pow-rev N/A

      \[\leadsto \color{blue}{\log \left({\left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)}^{3}\right)} \cdot s \]

   10. lower-log.f32 N/A

       \[\leadsto \color{blue}{\log \left({\left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)}^{3}\right)} \cdot s \]

   11. lower-pow.f32 N/A

       \[\leadsto \log \color{blue}{\left({\left(\frac{1}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}\right)}^{3}\right)} \cdot s \]

   12. lift--.f32 N/A

       \[\leadsto \log \left({\left(\frac{1}{1 - \frac{\color{blue}{u - \frac{1}{4}}}{\frac{3}{4}}}\right)}^{3}\right) \cdot s \]

   13. lift-/.f32 N/A

       \[\leadsto \log \left({\left(\frac{1}{1 - \color{blue}{\frac{u - \frac{1}{4}}{\frac{3}{4}}}}\right)}^{3}\right) \cdot s \]

   14. lift--.f32 N/A

       \[\leadsto \log \left({\left(\frac{1}{\color{blue}{1 - \frac{u - \frac{1}{4}}{\frac{3}{4}}}}\right)}^{3}\right) \cdot s \]

   15. lower-/.f32 95.9

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

6. Applied rewrites 95.9%

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

7. Taylor expanded in u around 0

   \[\leadsto \log \color{blue}{\frac{27}{64}} \cdot s \]
8. Step-by-step derivation

9. Applied rewrites 7.7%

   \[\leadsto \log \color{blue}{0.421875} \cdot s \]
10. Add Preprocessing

Reproduce

herbie shell --seed 2025015 
(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))))))