Ian Simplification

Percentage Accurate: 6.7% → 8.1%
Time: 9.8s
Alternatives: 4
Speedup: 1.1×

Specification

?
\[\begin{array}{l} \\ \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right) \end{array} \]
(FPCore (x)
 :precision binary64
 (- (/ (PI) 2.0) (* 2.0 (asin (sqrt (/ (- 1.0 x) 2.0))))))
\begin{array}{l}

\\
\frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)
\end{array}

Sampling outcomes in binary64 precision:

Local Percentage Accuracy vs ?

The average percentage accuracy by input value. Horizontal axis shows value of an input variable; the variable is choosen in the title. Vertical axis is accuracy; higher is better. Red represent the original program, while blue represents Herbie's suggestion. These can be toggled with buttons below the plot. The line is an average while dots represent individual samples.

Accuracy vs Speed?

Herbie found 4 alternatives:

AlternativeAccuracySpeedup
The accuracy (vertical axis) and speed (horizontal axis) of each alternatives. Up and to the right is better. The red square shows the initial program, and each blue circle shows an alternative.The line shows the best available speed-accuracy tradeoffs.

Initial Program: 6.7% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right) \end{array} \]
(FPCore (x)
 :precision binary64
 (- (/ (PI) 2.0) (* 2.0 (asin (sqrt (/ (- 1.0 x) 2.0))))))
\begin{array}{l}

\\
\frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)
\end{array}

Alternative 1: 8.1% accurate, 0.1× speedup?

\[\begin{array}{l} \\ \begin{array}{l} t_0 := 0.5 \cdot \mathsf{PI}\left(\right)\\ t_1 := t\_0 - \cos^{-1} \left(\sqrt{\left(1 - x\right) \cdot 0.5}\right)\\ t_2 := t\_1 \cdot -2\\ t_3 := \mathsf{fma}\left(t\_0, t\_0 - t\_2, {t\_2}^{2}\right)\\ \frac{{t\_1}^{3} \cdot -8}{t\_3} + \frac{{t\_0}^{3}}{t\_3} \end{array} \end{array} \]
(FPCore (x)
 :precision binary64
 (let* ((t_0 (* 0.5 (PI)))
        (t_1 (- t_0 (acos (sqrt (* (- 1.0 x) 0.5)))))
        (t_2 (* t_1 -2.0))
        (t_3 (fma t_0 (- t_0 t_2) (pow t_2 2.0))))
   (+ (/ (* (pow t_1 3.0) -8.0) t_3) (/ (pow t_0 3.0) t_3))))
\begin{array}{l}

\\
\begin{array}{l}
t_0 := 0.5 \cdot \mathsf{PI}\left(\right)\\
t_1 := t\_0 - \cos^{-1} \left(\sqrt{\left(1 - x\right) \cdot 0.5}\right)\\
t_2 := t\_1 \cdot -2\\
t_3 := \mathsf{fma}\left(t\_0, t\_0 - t\_2, {t\_2}^{2}\right)\\
\frac{{t\_1}^{3} \cdot -8}{t\_3} + \frac{{t\_0}^{3}}{t\_3}
\end{array}
\end{array}
Derivation
  1. Initial program 6.5%

    \[\frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right) \]
  2. Add Preprocessing
  3. Step-by-step derivation
    1. lift-asin.f64N/A

      \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \color{blue}{\sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)} \]
    2. asin-acosN/A

      \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \color{blue}{\left(\frac{\mathsf{PI}\left(\right)}{2} - \cos^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)\right)} \]
    3. lift-PI.f64N/A

      \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \left(\frac{\color{blue}{\mathsf{PI}\left(\right)}}{2} - \cos^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)\right) \]
    4. lift-/.f64N/A

      \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \left(\color{blue}{\frac{\mathsf{PI}\left(\right)}{2}} - \cos^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)\right) \]
    5. lower--.f64N/A

      \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \color{blue}{\left(\frac{\mathsf{PI}\left(\right)}{2} - \cos^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)\right)} \]
    6. lower-acos.f648.1

      \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \left(\frac{\mathsf{PI}\left(\right)}{2} - \color{blue}{\cos^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)}\right) \]
  4. Applied rewrites8.1%

    \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \color{blue}{\left(\frac{\mathsf{PI}\left(\right)}{2} - \cos^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)\right)} \]
  5. Taylor expanded in x around 0

    \[\leadsto \color{blue}{\frac{1}{2} \cdot \mathsf{PI}\left(\right) - 2 \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\frac{1}{2}} \cdot \sqrt{1 - x}\right)\right)} \]
  6. Step-by-step derivation
    1. fp-cancel-sub-sign-invN/A

      \[\leadsto \color{blue}{\frac{1}{2} \cdot \mathsf{PI}\left(\right) + \left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\frac{1}{2}} \cdot \sqrt{1 - x}\right)\right)} \]
    2. +-commutativeN/A

      \[\leadsto \color{blue}{\left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\frac{1}{2}} \cdot \sqrt{1 - x}\right)\right) + \frac{1}{2} \cdot \mathsf{PI}\left(\right)} \]
    3. *-commutativeN/A

      \[\leadsto \left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \color{blue}{\left(\sqrt{1 - x} \cdot \sqrt{\frac{1}{2}}\right)}\right) + \frac{1}{2} \cdot \mathsf{PI}\left(\right) \]
    4. *-lft-identityN/A

      \[\leadsto \left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{1 - \color{blue}{1 \cdot x}} \cdot \sqrt{\frac{1}{2}}\right)\right) + \frac{1}{2} \cdot \mathsf{PI}\left(\right) \]
    5. metadata-evalN/A

      \[\leadsto \left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{1 - \color{blue}{\left(\mathsf{neg}\left(-1\right)\right)} \cdot x} \cdot \sqrt{\frac{1}{2}}\right)\right) + \frac{1}{2} \cdot \mathsf{PI}\left(\right) \]
    6. cancel-sign-subN/A

      \[\leadsto \left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\color{blue}{1 + -1 \cdot x}} \cdot \sqrt{\frac{1}{2}}\right)\right) + \frac{1}{2} \cdot \mathsf{PI}\left(\right) \]
    7. *-commutativeN/A

      \[\leadsto \left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \color{blue}{\left(\sqrt{\frac{1}{2}} \cdot \sqrt{1 + -1 \cdot x}\right)}\right) + \frac{1}{2} \cdot \mathsf{PI}\left(\right) \]
  7. Applied rewrites8.1%

    \[\leadsto \color{blue}{\mathsf{fma}\left(-2, \mathsf{PI}\left(\right) \cdot 0.5 - \cos^{-1} \left(\sqrt{1 - x} \cdot \sqrt{0.5}\right), \mathsf{PI}\left(\right) \cdot 0.5\right)} \]
  8. Step-by-step derivation
    1. Applied rewrites8.1%

      \[\leadsto \frac{{\left(0.5 \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\left(1 - x\right) \cdot 0.5}\right)\right)}^{3} \cdot -8}{\mathsf{fma}\left(0.5 \cdot \mathsf{PI}\left(\right), 0.5 \cdot \mathsf{PI}\left(\right) - \left(0.5 \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\left(1 - x\right) \cdot 0.5}\right)\right) \cdot -2, {\left(\left(0.5 \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\left(1 - x\right) \cdot 0.5}\right)\right) \cdot -2\right)}^{2}\right)} + \color{blue}{\frac{{\left(0.5 \cdot \mathsf{PI}\left(\right)\right)}^{3}}{\mathsf{fma}\left(0.5 \cdot \mathsf{PI}\left(\right), 0.5 \cdot \mathsf{PI}\left(\right) - \left(0.5 \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\left(1 - x\right) \cdot 0.5}\right)\right) \cdot -2, {\left(\left(0.5 \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\left(1 - x\right) \cdot 0.5}\right)\right) \cdot -2\right)}^{2}\right)}} \]
    2. Add Preprocessing

    Alternative 2: 8.1% accurate, 1.0× speedup?

    \[\begin{array}{l} \\ \begin{array}{l} t_0 := 0.5 \cdot \mathsf{PI}\left(\right)\\ \mathsf{fma}\left(t\_0 - \cos^{-1} \left(\sqrt{\left(1 - x\right) \cdot 0.5}\right), -2, t\_0\right) \end{array} \end{array} \]
    (FPCore (x)
     :precision binary64
     (let* ((t_0 (* 0.5 (PI))))
       (fma (- t_0 (acos (sqrt (* (- 1.0 x) 0.5)))) -2.0 t_0)))
    \begin{array}{l}
    
    \\
    \begin{array}{l}
    t_0 := 0.5 \cdot \mathsf{PI}\left(\right)\\
    \mathsf{fma}\left(t\_0 - \cos^{-1} \left(\sqrt{\left(1 - x\right) \cdot 0.5}\right), -2, t\_0\right)
    \end{array}
    \end{array}
    
    Derivation
    1. Initial program 6.5%

      \[\frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right) \]
    2. Add Preprocessing
    3. Step-by-step derivation
      1. lift-asin.f64N/A

        \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \color{blue}{\sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)} \]
      2. asin-acosN/A

        \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \color{blue}{\left(\frac{\mathsf{PI}\left(\right)}{2} - \cos^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)\right)} \]
      3. lift-PI.f64N/A

        \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \left(\frac{\color{blue}{\mathsf{PI}\left(\right)}}{2} - \cos^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)\right) \]
      4. lift-/.f64N/A

        \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \left(\color{blue}{\frac{\mathsf{PI}\left(\right)}{2}} - \cos^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)\right) \]
      5. lower--.f64N/A

        \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \color{blue}{\left(\frac{\mathsf{PI}\left(\right)}{2} - \cos^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)\right)} \]
      6. lower-acos.f648.1

        \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \left(\frac{\mathsf{PI}\left(\right)}{2} - \color{blue}{\cos^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)}\right) \]
    4. Applied rewrites8.1%

      \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \color{blue}{\left(\frac{\mathsf{PI}\left(\right)}{2} - \cos^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)\right)} \]
    5. Taylor expanded in x around 0

      \[\leadsto \color{blue}{\frac{1}{2} \cdot \mathsf{PI}\left(\right) - 2 \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\frac{1}{2}} \cdot \sqrt{1 - x}\right)\right)} \]
    6. Step-by-step derivation
      1. fp-cancel-sub-sign-invN/A

        \[\leadsto \color{blue}{\frac{1}{2} \cdot \mathsf{PI}\left(\right) + \left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\frac{1}{2}} \cdot \sqrt{1 - x}\right)\right)} \]
      2. +-commutativeN/A

        \[\leadsto \color{blue}{\left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\frac{1}{2}} \cdot \sqrt{1 - x}\right)\right) + \frac{1}{2} \cdot \mathsf{PI}\left(\right)} \]
      3. *-commutativeN/A

        \[\leadsto \left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \color{blue}{\left(\sqrt{1 - x} \cdot \sqrt{\frac{1}{2}}\right)}\right) + \frac{1}{2} \cdot \mathsf{PI}\left(\right) \]
      4. *-lft-identityN/A

        \[\leadsto \left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{1 - \color{blue}{1 \cdot x}} \cdot \sqrt{\frac{1}{2}}\right)\right) + \frac{1}{2} \cdot \mathsf{PI}\left(\right) \]
      5. metadata-evalN/A

        \[\leadsto \left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{1 - \color{blue}{\left(\mathsf{neg}\left(-1\right)\right)} \cdot x} \cdot \sqrt{\frac{1}{2}}\right)\right) + \frac{1}{2} \cdot \mathsf{PI}\left(\right) \]
      6. cancel-sign-subN/A

        \[\leadsto \left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\color{blue}{1 + -1 \cdot x}} \cdot \sqrt{\frac{1}{2}}\right)\right) + \frac{1}{2} \cdot \mathsf{PI}\left(\right) \]
      7. *-commutativeN/A

        \[\leadsto \left(\mathsf{neg}\left(2\right)\right) \cdot \left(\frac{1}{2} \cdot \mathsf{PI}\left(\right) - \cos^{-1} \color{blue}{\left(\sqrt{\frac{1}{2}} \cdot \sqrt{1 + -1 \cdot x}\right)}\right) + \frac{1}{2} \cdot \mathsf{PI}\left(\right) \]
    7. Applied rewrites8.1%

      \[\leadsto \color{blue}{\mathsf{fma}\left(-2, \mathsf{PI}\left(\right) \cdot 0.5 - \cos^{-1} \left(\sqrt{1 - x} \cdot \sqrt{0.5}\right), \mathsf{PI}\left(\right) \cdot 0.5\right)} \]
    8. Step-by-step derivation
      1. Applied rewrites8.1%

        \[\leadsto \color{blue}{\mathsf{fma}\left(0.5 \cdot \mathsf{PI}\left(\right) - \cos^{-1} \left(\sqrt{\left(1 - x\right) \cdot 0.5}\right), -2, 0.5 \cdot \mathsf{PI}\left(\right)\right)} \]
      2. Add Preprocessing

      Alternative 3: 6.7% accurate, 1.1× speedup?

      \[\begin{array}{l} \\ \mathsf{fma}\left(\sin^{-1} \left(\sqrt{\mathsf{fma}\left(-0.5, x, 0.5\right)}\right), -2, \frac{\mathsf{PI}\left(\right)}{2}\right) \end{array} \]
      (FPCore (x)
       :precision binary64
       (fma (asin (sqrt (fma -0.5 x 0.5))) -2.0 (/ (PI) 2.0)))
      \begin{array}{l}
      
      \\
      \mathsf{fma}\left(\sin^{-1} \left(\sqrt{\mathsf{fma}\left(-0.5, x, 0.5\right)}\right), -2, \frac{\mathsf{PI}\left(\right)}{2}\right)
      \end{array}
      
      Derivation
      1. Initial program 6.5%

        \[\frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right) \]
      2. Add Preprocessing
      3. Step-by-step derivation
        1. lift--.f64N/A

          \[\leadsto \color{blue}{\frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)} \]
        2. lift-*.f64N/A

          \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - \color{blue}{2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)} \]
        3. fp-cancel-sub-sign-invN/A

          \[\leadsto \color{blue}{\frac{\mathsf{PI}\left(\right)}{2} + \left(\mathsf{neg}\left(2\right)\right) \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)} \]
        4. +-commutativeN/A

          \[\leadsto \color{blue}{\left(\mathsf{neg}\left(2\right)\right) \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right) + \frac{\mathsf{PI}\left(\right)}{2}} \]
        5. *-commutativeN/A

          \[\leadsto \color{blue}{\sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right) \cdot \left(\mathsf{neg}\left(2\right)\right)} + \frac{\mathsf{PI}\left(\right)}{2} \]
        6. lower-fma.f64N/A

          \[\leadsto \color{blue}{\mathsf{fma}\left(\sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right), \mathsf{neg}\left(2\right), \frac{\mathsf{PI}\left(\right)}{2}\right)} \]
        7. metadata-eval6.5

          \[\leadsto \mathsf{fma}\left(\sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right), \color{blue}{-2}, \frac{\mathsf{PI}\left(\right)}{2}\right) \]
      4. Applied rewrites6.5%

        \[\leadsto \color{blue}{\mathsf{fma}\left(\sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right), -2, \frac{\mathsf{PI}\left(\right)}{2}\right)} \]
      5. Taylor expanded in x around 0

        \[\leadsto \mathsf{fma}\left(\sin^{-1} \left(\sqrt{\color{blue}{\frac{1}{2} + \frac{-1}{2} \cdot x}}\right), -2, \frac{\mathsf{PI}\left(\right)}{2}\right) \]
      6. Step-by-step derivation
        1. +-commutativeN/A

          \[\leadsto \mathsf{fma}\left(\sin^{-1} \left(\sqrt{\color{blue}{\frac{-1}{2} \cdot x + \frac{1}{2}}}\right), -2, \frac{\mathsf{PI}\left(\right)}{2}\right) \]
        2. lower-fma.f646.5

          \[\leadsto \mathsf{fma}\left(\sin^{-1} \left(\sqrt{\color{blue}{\mathsf{fma}\left(-0.5, x, 0.5\right)}}\right), -2, \frac{\mathsf{PI}\left(\right)}{2}\right) \]
      7. Applied rewrites6.5%

        \[\leadsto \mathsf{fma}\left(\sin^{-1} \left(\sqrt{\color{blue}{\mathsf{fma}\left(-0.5, x, 0.5\right)}}\right), -2, \frac{\mathsf{PI}\left(\right)}{2}\right) \]
      8. Add Preprocessing

      Alternative 4: 4.1% accurate, 1.1× speedup?

      \[\begin{array}{l} \\ \mathsf{fma}\left(\sin^{-1} \left(\sqrt{0.5}\right), -2, \frac{\mathsf{PI}\left(\right)}{2}\right) \end{array} \]
      (FPCore (x) :precision binary64 (fma (asin (sqrt 0.5)) -2.0 (/ (PI) 2.0)))
      \begin{array}{l}
      
      \\
      \mathsf{fma}\left(\sin^{-1} \left(\sqrt{0.5}\right), -2, \frac{\mathsf{PI}\left(\right)}{2}\right)
      \end{array}
      
      Derivation
      1. Initial program 6.5%

        \[\frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right) \]
      2. Add Preprocessing
      3. Step-by-step derivation
        1. lift--.f64N/A

          \[\leadsto \color{blue}{\frac{\mathsf{PI}\left(\right)}{2} - 2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)} \]
        2. lift-*.f64N/A

          \[\leadsto \frac{\mathsf{PI}\left(\right)}{2} - \color{blue}{2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)} \]
        3. fp-cancel-sub-sign-invN/A

          \[\leadsto \color{blue}{\frac{\mathsf{PI}\left(\right)}{2} + \left(\mathsf{neg}\left(2\right)\right) \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)} \]
        4. +-commutativeN/A

          \[\leadsto \color{blue}{\left(\mathsf{neg}\left(2\right)\right) \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right) + \frac{\mathsf{PI}\left(\right)}{2}} \]
        5. *-commutativeN/A

          \[\leadsto \color{blue}{\sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right) \cdot \left(\mathsf{neg}\left(2\right)\right)} + \frac{\mathsf{PI}\left(\right)}{2} \]
        6. lower-fma.f64N/A

          \[\leadsto \color{blue}{\mathsf{fma}\left(\sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right), \mathsf{neg}\left(2\right), \frac{\mathsf{PI}\left(\right)}{2}\right)} \]
        7. metadata-eval6.5

          \[\leadsto \mathsf{fma}\left(\sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right), \color{blue}{-2}, \frac{\mathsf{PI}\left(\right)}{2}\right) \]
      4. Applied rewrites6.5%

        \[\leadsto \color{blue}{\mathsf{fma}\left(\sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right), -2, \frac{\mathsf{PI}\left(\right)}{2}\right)} \]
      5. Taylor expanded in x around 0

        \[\leadsto \mathsf{fma}\left(\sin^{-1} \left(\sqrt{\color{blue}{\frac{1}{2}}}\right), -2, \frac{\mathsf{PI}\left(\right)}{2}\right) \]
      6. Step-by-step derivation
        1. Applied rewrites4.0%

          \[\leadsto \mathsf{fma}\left(\sin^{-1} \left(\sqrt{\color{blue}{0.5}}\right), -2, \frac{\mathsf{PI}\left(\right)}{2}\right) \]
        2. Add Preprocessing

        Developer Target 1: 100.0% accurate, 1.4× speedup?

        \[\begin{array}{l} \\ \sin^{-1} x \end{array} \]
        (FPCore (x) :precision binary64 (asin x))
        double code(double x) {
        	return asin(x);
        }
        
        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(8) function code(x)
        use fmin_fmax_functions
            real(8), intent (in) :: x
            code = asin(x)
        end function
        
        public static double code(double x) {
        	return Math.asin(x);
        }
        
        def code(x):
        	return math.asin(x)
        
        function code(x)
        	return asin(x)
        end
        
        function tmp = code(x)
        	tmp = asin(x);
        end
        
        code[x_] := N[ArcSin[x], $MachinePrecision]
        
        \begin{array}{l}
        
        \\
        \sin^{-1} x
        \end{array}
        

        Reproduce

        ?
        herbie shell --seed 2025015 
        (FPCore (x)
          :name "Ian Simplification"
          :precision binary64
        
          :alt
          (! :herbie-platform default (asin x))
        
          (- (/ (PI) 2.0) (* 2.0 (asin (sqrt (/ (- 1.0 x) 2.0))))))