ENA, Section 1.4, Exercise 4b, n=2

Percentage Accurate: 75.9% → 100.0%
Time: 3.6s
Alternatives: 5
Speedup: TODO×

Specification

?
\[{\left(x + \varepsilon\right)}^{2} - {x}^{2} \]

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 5 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.

Alternative 1?

\[\varepsilon \cdot \mathsf{fma}\left(2, x, \varepsilon\right) \]
Derivation
  1. Initial program 72.9%

    \[{\left(x + \varepsilon\right)}^{2} - {x}^{2} \]
  2. Step-by-step derivation
    1. unpow272.9%

      \[\leadsto \color{blue}{\left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right)} - {x}^{2} \]
    2. unpow272.9%

      \[\leadsto \left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right) - \color{blue}{x \cdot x} \]
    3. difference-of-squares72.8%

      \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) + x\right) \cdot \left(\left(x + \varepsilon\right) - x\right)} \]
    4. *-commutative72.8%

      \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right)} \]
    5. +-commutative72.8%

      \[\leadsto \left(\color{blue}{\left(\varepsilon + x\right)} - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
    6. associate--l+100.0%

      \[\leadsto \color{blue}{\left(\varepsilon + \left(x - x\right)\right)} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
    7. +-inverses100.0%

      \[\leadsto \left(\varepsilon + \color{blue}{0}\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
    8. +-rgt-identity100.0%

      \[\leadsto \color{blue}{\varepsilon} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
    9. +-commutative100.0%

      \[\leadsto \varepsilon \cdot \color{blue}{\left(x + \left(x + \varepsilon\right)\right)} \]
    10. associate-+r+100.0%

      \[\leadsto \varepsilon \cdot \color{blue}{\left(\left(x + x\right) + \varepsilon\right)} \]
    11. count-2100.0%

      \[\leadsto \varepsilon \cdot \left(\color{blue}{2 \cdot x} + \varepsilon\right) \]
    12. fma-def100.0%

      \[\leadsto \varepsilon \cdot \color{blue}{\mathsf{fma}\left(2, x, \varepsilon\right)} \]
  3. Simplified100.0%

    \[\leadsto \color{blue}{\varepsilon \cdot \mathsf{fma}\left(2, x, \varepsilon\right)} \]
  4. Final simplification100.0%

    \[\leadsto \varepsilon \cdot \mathsf{fma}\left(2, x, \varepsilon\right) \]

Alternative 2?

\[\begin{array}{l} \mathbf{if}\;x \leq -1.9 \cdot 10^{-126} \lor \neg \left(x \leq 1.85 \cdot 10^{-113}\right):\\ \;\;\;\;2 \cdot \left(\varepsilon \cdot x\right)\\ \mathbf{else}:\\ \;\;\;\;\varepsilon \cdot \varepsilon\\ \end{array} \]
Derivation
  1. Split input into 2 regimes
  2. if x < -1.8999999999999999e-126 or 1.8499999999999999e-113 < x

    1. Initial program 31.3%

      \[{\left(x + \varepsilon\right)}^{2} - {x}^{2} \]
    2. Step-by-step derivation
      1. unpow231.3%

        \[\leadsto \color{blue}{\left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right)} - {x}^{2} \]
      2. unpow231.3%

        \[\leadsto \left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right) - \color{blue}{x \cdot x} \]
      3. difference-of-squares31.2%

        \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) + x\right) \cdot \left(\left(x + \varepsilon\right) - x\right)} \]
      4. *-commutative31.2%

        \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right)} \]
      5. +-commutative31.2%

        \[\leadsto \left(\color{blue}{\left(\varepsilon + x\right)} - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      6. associate--l+99.9%

        \[\leadsto \color{blue}{\left(\varepsilon + \left(x - x\right)\right)} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      7. +-inverses99.9%

        \[\leadsto \left(\varepsilon + \color{blue}{0}\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      8. +-rgt-identity99.9%

        \[\leadsto \color{blue}{\varepsilon} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      9. +-commutative99.9%

        \[\leadsto \varepsilon \cdot \color{blue}{\left(x + \left(x + \varepsilon\right)\right)} \]
      10. associate-+r+100.0%

        \[\leadsto \varepsilon \cdot \color{blue}{\left(\left(x + x\right) + \varepsilon\right)} \]
      11. count-2100.0%

        \[\leadsto \varepsilon \cdot \left(\color{blue}{2 \cdot x} + \varepsilon\right) \]
      12. fma-def100.0%

        \[\leadsto \varepsilon \cdot \color{blue}{\mathsf{fma}\left(2, x, \varepsilon\right)} \]
    3. Simplified100.0%

      \[\leadsto \color{blue}{\varepsilon \cdot \mathsf{fma}\left(2, x, \varepsilon\right)} \]
    4. Taylor expanded in eps around 0 91.1%

      \[\leadsto \color{blue}{2 \cdot \left(\varepsilon \cdot x\right)} \]

    if -1.8999999999999999e-126 < x < 1.8499999999999999e-113

    1. Initial program 99.1%

      \[{\left(x + \varepsilon\right)}^{2} - {x}^{2} \]
    2. Step-by-step derivation
      1. unpow299.1%

        \[\leadsto \color{blue}{\left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right)} - {x}^{2} \]
      2. unpow299.1%

        \[\leadsto \left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right) - \color{blue}{x \cdot x} \]
      3. difference-of-squares99.1%

        \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) + x\right) \cdot \left(\left(x + \varepsilon\right) - x\right)} \]
      4. *-commutative99.1%

        \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right)} \]
      5. +-commutative99.1%

        \[\leadsto \left(\color{blue}{\left(\varepsilon + x\right)} - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      6. associate--l+100.0%

        \[\leadsto \color{blue}{\left(\varepsilon + \left(x - x\right)\right)} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      7. +-inverses100.0%

        \[\leadsto \left(\varepsilon + \color{blue}{0}\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      8. +-rgt-identity100.0%

        \[\leadsto \color{blue}{\varepsilon} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      9. +-commutative100.0%

        \[\leadsto \varepsilon \cdot \color{blue}{\left(x + \left(x + \varepsilon\right)\right)} \]
      10. associate-+r+100.0%

        \[\leadsto \varepsilon \cdot \color{blue}{\left(\left(x + x\right) + \varepsilon\right)} \]
      11. count-2100.0%

        \[\leadsto \varepsilon \cdot \left(\color{blue}{2 \cdot x} + \varepsilon\right) \]
      12. fma-def100.0%

        \[\leadsto \varepsilon \cdot \color{blue}{\mathsf{fma}\left(2, x, \varepsilon\right)} \]
    3. Simplified100.0%

      \[\leadsto \color{blue}{\varepsilon \cdot \mathsf{fma}\left(2, x, \varepsilon\right)} \]
    4. Taylor expanded in eps around inf 98.4%

      \[\leadsto \color{blue}{{\varepsilon}^{2}} \]
    5. Step-by-step derivation
      1. unpow298.4%

        \[\leadsto \color{blue}{\varepsilon \cdot \varepsilon} \]
    6. Simplified98.4%

      \[\leadsto \color{blue}{\varepsilon \cdot \varepsilon} \]
  3. Recombined 2 regimes into one program.
  4. Final simplification95.6%

    \[\leadsto \begin{array}{l} \mathbf{if}\;x \leq -1.9 \cdot 10^{-126} \lor \neg \left(x \leq 1.85 \cdot 10^{-113}\right):\\ \;\;\;\;2 \cdot \left(\varepsilon \cdot x\right)\\ \mathbf{else}:\\ \;\;\;\;\varepsilon \cdot \varepsilon\\ \end{array} \]

Alternative 3?

\[\begin{array}{l} \mathbf{if}\;x \leq -3.5 \cdot 10^{-126} \lor \neg \left(x \leq 9.5 \cdot 10^{-110}\right):\\ \;\;\;\;\varepsilon \cdot \left(x + x\right)\\ \mathbf{else}:\\ \;\;\;\;\varepsilon \cdot \varepsilon\\ \end{array} \]
Derivation
  1. Split input into 2 regimes
  2. if x < -3.5e-126 or 9.50000000000000004e-110 < x

    1. Initial program 31.3%

      \[{\left(x + \varepsilon\right)}^{2} - {x}^{2} \]
    2. Step-by-step derivation
      1. unpow231.3%

        \[\leadsto \color{blue}{\left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right)} - {x}^{2} \]
      2. unpow231.3%

        \[\leadsto \left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right) - \color{blue}{x \cdot x} \]
      3. difference-of-squares31.2%

        \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) + x\right) \cdot \left(\left(x + \varepsilon\right) - x\right)} \]
      4. *-commutative31.2%

        \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right)} \]
      5. +-commutative31.2%

        \[\leadsto \left(\color{blue}{\left(\varepsilon + x\right)} - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      6. associate--l+99.9%

        \[\leadsto \color{blue}{\left(\varepsilon + \left(x - x\right)\right)} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      7. +-inverses99.9%

        \[\leadsto \left(\varepsilon + \color{blue}{0}\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      8. +-rgt-identity99.9%

        \[\leadsto \color{blue}{\varepsilon} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      9. +-commutative99.9%

        \[\leadsto \varepsilon \cdot \color{blue}{\left(x + \left(x + \varepsilon\right)\right)} \]
      10. associate-+r+100.0%

        \[\leadsto \varepsilon \cdot \color{blue}{\left(\left(x + x\right) + \varepsilon\right)} \]
      11. count-2100.0%

        \[\leadsto \varepsilon \cdot \left(\color{blue}{2 \cdot x} + \varepsilon\right) \]
      12. fma-def100.0%

        \[\leadsto \varepsilon \cdot \color{blue}{\mathsf{fma}\left(2, x, \varepsilon\right)} \]
    3. Simplified100.0%

      \[\leadsto \color{blue}{\varepsilon \cdot \mathsf{fma}\left(2, x, \varepsilon\right)} \]
    4. Step-by-step derivation
      1. fma-udef100.0%

        \[\leadsto \varepsilon \cdot \color{blue}{\left(2 \cdot x + \varepsilon\right)} \]
      2. distribute-rgt-in100.0%

        \[\leadsto \color{blue}{\left(2 \cdot x\right) \cdot \varepsilon + \varepsilon \cdot \varepsilon} \]
    5. Applied egg-rr100.0%

      \[\leadsto \color{blue}{\left(2 \cdot x\right) \cdot \varepsilon + \varepsilon \cdot \varepsilon} \]
    6. Taylor expanded in x around inf 91.1%

      \[\leadsto \color{blue}{2 \cdot \left(\varepsilon \cdot x\right)} \]
    7. Step-by-step derivation
      1. count-291.1%

        \[\leadsto \color{blue}{\varepsilon \cdot x + \varepsilon \cdot x} \]
      2. distribute-lft-out91.1%

        \[\leadsto \color{blue}{\varepsilon \cdot \left(x + x\right)} \]
    8. Simplified91.1%

      \[\leadsto \color{blue}{\varepsilon \cdot \left(x + x\right)} \]

    if -3.5e-126 < x < 9.50000000000000004e-110

    1. Initial program 99.1%

      \[{\left(x + \varepsilon\right)}^{2} - {x}^{2} \]
    2. Step-by-step derivation
      1. unpow299.1%

        \[\leadsto \color{blue}{\left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right)} - {x}^{2} \]
      2. unpow299.1%

        \[\leadsto \left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right) - \color{blue}{x \cdot x} \]
      3. difference-of-squares99.1%

        \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) + x\right) \cdot \left(\left(x + \varepsilon\right) - x\right)} \]
      4. *-commutative99.1%

        \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right)} \]
      5. +-commutative99.1%

        \[\leadsto \left(\color{blue}{\left(\varepsilon + x\right)} - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      6. associate--l+100.0%

        \[\leadsto \color{blue}{\left(\varepsilon + \left(x - x\right)\right)} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      7. +-inverses100.0%

        \[\leadsto \left(\varepsilon + \color{blue}{0}\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      8. +-rgt-identity100.0%

        \[\leadsto \color{blue}{\varepsilon} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
      9. +-commutative100.0%

        \[\leadsto \varepsilon \cdot \color{blue}{\left(x + \left(x + \varepsilon\right)\right)} \]
      10. associate-+r+100.0%

        \[\leadsto \varepsilon \cdot \color{blue}{\left(\left(x + x\right) + \varepsilon\right)} \]
      11. count-2100.0%

        \[\leadsto \varepsilon \cdot \left(\color{blue}{2 \cdot x} + \varepsilon\right) \]
      12. fma-def100.0%

        \[\leadsto \varepsilon \cdot \color{blue}{\mathsf{fma}\left(2, x, \varepsilon\right)} \]
    3. Simplified100.0%

      \[\leadsto \color{blue}{\varepsilon \cdot \mathsf{fma}\left(2, x, \varepsilon\right)} \]
    4. Taylor expanded in eps around inf 98.4%

      \[\leadsto \color{blue}{{\varepsilon}^{2}} \]
    5. Step-by-step derivation
      1. unpow298.4%

        \[\leadsto \color{blue}{\varepsilon \cdot \varepsilon} \]
    6. Simplified98.4%

      \[\leadsto \color{blue}{\varepsilon \cdot \varepsilon} \]
  3. Recombined 2 regimes into one program.
  4. Final simplification95.6%

    \[\leadsto \begin{array}{l} \mathbf{if}\;x \leq -3.5 \cdot 10^{-126} \lor \neg \left(x \leq 9.5 \cdot 10^{-110}\right):\\ \;\;\;\;\varepsilon \cdot \left(x + x\right)\\ \mathbf{else}:\\ \;\;\;\;\varepsilon \cdot \varepsilon\\ \end{array} \]

Alternative 4?

\[\varepsilon \cdot \left(2 \cdot x\right) + \varepsilon \cdot \varepsilon \]
Derivation
  1. Initial program 72.9%

    \[{\left(x + \varepsilon\right)}^{2} - {x}^{2} \]
  2. Step-by-step derivation
    1. unpow272.9%

      \[\leadsto \color{blue}{\left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right)} - {x}^{2} \]
    2. unpow272.9%

      \[\leadsto \left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right) - \color{blue}{x \cdot x} \]
    3. difference-of-squares72.8%

      \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) + x\right) \cdot \left(\left(x + \varepsilon\right) - x\right)} \]
    4. *-commutative72.8%

      \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right)} \]
    5. +-commutative72.8%

      \[\leadsto \left(\color{blue}{\left(\varepsilon + x\right)} - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
    6. associate--l+100.0%

      \[\leadsto \color{blue}{\left(\varepsilon + \left(x - x\right)\right)} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
    7. +-inverses100.0%

      \[\leadsto \left(\varepsilon + \color{blue}{0}\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
    8. +-rgt-identity100.0%

      \[\leadsto \color{blue}{\varepsilon} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
    9. +-commutative100.0%

      \[\leadsto \varepsilon \cdot \color{blue}{\left(x + \left(x + \varepsilon\right)\right)} \]
    10. associate-+r+100.0%

      \[\leadsto \varepsilon \cdot \color{blue}{\left(\left(x + x\right) + \varepsilon\right)} \]
    11. count-2100.0%

      \[\leadsto \varepsilon \cdot \left(\color{blue}{2 \cdot x} + \varepsilon\right) \]
    12. fma-def100.0%

      \[\leadsto \varepsilon \cdot \color{blue}{\mathsf{fma}\left(2, x, \varepsilon\right)} \]
  3. Simplified100.0%

    \[\leadsto \color{blue}{\varepsilon \cdot \mathsf{fma}\left(2, x, \varepsilon\right)} \]
  4. Step-by-step derivation
    1. fma-udef100.0%

      \[\leadsto \varepsilon \cdot \color{blue}{\left(2 \cdot x + \varepsilon\right)} \]
    2. distribute-rgt-in100.0%

      \[\leadsto \color{blue}{\left(2 \cdot x\right) \cdot \varepsilon + \varepsilon \cdot \varepsilon} \]
  5. Applied egg-rr100.0%

    \[\leadsto \color{blue}{\left(2 \cdot x\right) \cdot \varepsilon + \varepsilon \cdot \varepsilon} \]
  6. Final simplification100.0%

    \[\leadsto \varepsilon \cdot \left(2 \cdot x\right) + \varepsilon \cdot \varepsilon \]

Alternative 5?

\[\varepsilon \cdot \varepsilon \]
Derivation
  1. Initial program 72.9%

    \[{\left(x + \varepsilon\right)}^{2} - {x}^{2} \]
  2. Step-by-step derivation
    1. unpow272.9%

      \[\leadsto \color{blue}{\left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right)} - {x}^{2} \]
    2. unpow272.9%

      \[\leadsto \left(x + \varepsilon\right) \cdot \left(x + \varepsilon\right) - \color{blue}{x \cdot x} \]
    3. difference-of-squares72.8%

      \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) + x\right) \cdot \left(\left(x + \varepsilon\right) - x\right)} \]
    4. *-commutative72.8%

      \[\leadsto \color{blue}{\left(\left(x + \varepsilon\right) - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right)} \]
    5. +-commutative72.8%

      \[\leadsto \left(\color{blue}{\left(\varepsilon + x\right)} - x\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
    6. associate--l+100.0%

      \[\leadsto \color{blue}{\left(\varepsilon + \left(x - x\right)\right)} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
    7. +-inverses100.0%

      \[\leadsto \left(\varepsilon + \color{blue}{0}\right) \cdot \left(\left(x + \varepsilon\right) + x\right) \]
    8. +-rgt-identity100.0%

      \[\leadsto \color{blue}{\varepsilon} \cdot \left(\left(x + \varepsilon\right) + x\right) \]
    9. +-commutative100.0%

      \[\leadsto \varepsilon \cdot \color{blue}{\left(x + \left(x + \varepsilon\right)\right)} \]
    10. associate-+r+100.0%

      \[\leadsto \varepsilon \cdot \color{blue}{\left(\left(x + x\right) + \varepsilon\right)} \]
    11. count-2100.0%

      \[\leadsto \varepsilon \cdot \left(\color{blue}{2 \cdot x} + \varepsilon\right) \]
    12. fma-def100.0%

      \[\leadsto \varepsilon \cdot \color{blue}{\mathsf{fma}\left(2, x, \varepsilon\right)} \]
  3. Simplified100.0%

    \[\leadsto \color{blue}{\varepsilon \cdot \mathsf{fma}\left(2, x, \varepsilon\right)} \]
  4. Taylor expanded in eps around inf 70.8%

    \[\leadsto \color{blue}{{\varepsilon}^{2}} \]
  5. Step-by-step derivation
    1. unpow270.8%

      \[\leadsto \color{blue}{\varepsilon \cdot \varepsilon} \]
  6. Simplified70.8%

    \[\leadsto \color{blue}{\varepsilon \cdot \varepsilon} \]
  7. Final simplification70.8%

    \[\leadsto \varepsilon \cdot \varepsilon \]

Reproduce

?
herbie shell --seed 2023166 
(FPCore (x eps)
  :name "ENA, Section 1.4, Exercise 4b, n=2"
  :precision binary64
  :pre (and (and (<= -1000000000.0 x) (<= x 1000000000.0)) (and (<= -1.0 eps) (<= eps 1.0)))
  (- (pow (+ x eps) 2.0) (pow x 2.0)))