Average Error: 29.6 → 0.6
Time: 18.5s
Precision: 64
Internal Precision: 1344
\[e^{a \cdot x} - 1\]
↓
\[\begin{array}{l} \mathbf{if}\;a \cdot x \le -173.7775306990116:\\ \;\;\;\;\log \left(e^{e^{a \cdot x} - 1}\right)\\ \mathbf{else}:\\ \;\;\;\;x \cdot \left(a \cdot \left(\left(x \cdot \frac{1}{2}\right) \cdot a\right) + a\right) + {\left(a \cdot x\right)}^{3} \cdot \frac{1}{6}\\ \end{array}\]

Error

Bits error versus a

Bits error versus x

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Your Program's Arguments

Results

Enter valid numbers for all inputs

Target

Original29.6
Target0.2
Herbie0.6
\[\begin{array}{l} \mathbf{if}\;\left|a \cdot x\right| \lt \frac{1}{10}:\\ \;\;\;\;\left(a \cdot x\right) \cdot \left(1 + \left(\frac{a \cdot x}{2} + \frac{{\left(a \cdot x\right)}^{2}}{6}\right)\right)\\ \mathbf{else}:\\ \;\;\;\;e^{a \cdot x} - 1\\ \end{array}\]

Derivation

  1. Split input into 2 regimes

  2. if (* a x) < -173.7775306990116

    1. Initial program 0

      \[e^{a \cdot x} - 1\]
    2. Using strategy rm

    3. Applied add-log-exp0

      \[\leadsto \color{blue}{\log \left(e^{e^{a \cdot x} - 1}\right)}\]

    if -173.7775306990116 < (* a x)

    1. Initial program 43.9

      \[e^{a \cdot x} - 1\]

    2. Taylor expanded around 0 14.2

      \[\leadsto \color{blue}{\frac{1}{2} \cdot \left({a}^{2} \cdot {x}^{2}\right) + \left(a \cdot x + \frac{1}{6} \cdot \left({a}^{3} \cdot {x}^{3}\right)\right)}\]

    3. Simplified4.9

      \[\leadsto \color{blue}{\frac{1}{6} \cdot {\left(a \cdot x\right)}^{3} + x \cdot \left(a + \left(a \cdot a\right) \cdot \left(x \cdot \frac{1}{2}\right)\right)}\]
    4. Using strategy rm

    5. Applied associate-*l*0.9

      \[\leadsto \frac{1}{6} \cdot {\left(a \cdot x\right)}^{3} + x \cdot \left(a + \color{blue}{a \cdot \left(a \cdot \left(x \cdot \frac{1}{2}\right)\right)}\right)\]
  3. Recombined 2 regimes into one program.

  4. Final simplification0.6

    \[\leadsto \begin{array}{l} \mathbf{if}\;a \cdot x \le -173.7775306990116:\\ \;\;\;\;\log \left(e^{e^{a \cdot x} - 1}\right)\\ \mathbf{else}:\\ \;\;\;\;x \cdot \left(a \cdot \left(\left(x \cdot \frac{1}{2}\right) \cdot a\right) + a\right) + {\left(a \cdot x\right)}^{3} \cdot \frac{1}{6}\\ \end{array}\]

Runtime

Time bar (total: 18.5s)Debug logProfile

herbie shell --seed 2018221 
(FPCore (a x)
  :name "expax (section 3.5)"

  :herbie-target
  (if (< (fabs (* a x)) 1/10) (* (* a x) (+ 1 (+ (/ (* a x) 2) (/ (pow (* a x) 2) 6)))) (- (exp (* a x)) 1))

  (- (exp (* a x)) 1))