exp2 (problem 3.3.7)

Percentage Accurate: 52.5% → 99.2%
Time: 10.1s
Alternatives: 6
Speedup: 34.8×

Specification

?
\[\left|x\right| \leq 710\]
\[\begin{array}{l} \\ \left(e^{x} - 2\right) + e^{-x} \end{array} \]
(FPCore (x) :precision binary64 (+ (- (exp x) 2.0) (exp (- x))))
double code(double x) {
	return (exp(x) - 2.0) + exp(-x);
}
real(8) function code(x)
    real(8), intent (in) :: x
    code = (exp(x) - 2.0d0) + exp(-x)
end function
public static double code(double x) {
	return (Math.exp(x) - 2.0) + Math.exp(-x);
}
def code(x):
	return (math.exp(x) - 2.0) + math.exp(-x)
function code(x)
	return Float64(Float64(exp(x) - 2.0) + exp(Float64(-x)))
end
function tmp = code(x)
	tmp = (exp(x) - 2.0) + exp(-x);
end
code[x_] := N[(N[(N[Exp[x], $MachinePrecision] - 2.0), $MachinePrecision] + N[Exp[(-x)], $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\left(e^{x} - 2\right) + e^{-x}
\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 6 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: 52.5% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \left(e^{x} - 2\right) + e^{-x} \end{array} \]
(FPCore (x) :precision binary64 (+ (- (exp x) 2.0) (exp (- x))))
double code(double x) {
	return (exp(x) - 2.0) + exp(-x);
}
real(8) function code(x)
    real(8), intent (in) :: x
    code = (exp(x) - 2.0d0) + exp(-x)
end function
public static double code(double x) {
	return (Math.exp(x) - 2.0) + Math.exp(-x);
}
def code(x):
	return (math.exp(x) - 2.0) + math.exp(-x)
function code(x)
	return Float64(Float64(exp(x) - 2.0) + exp(Float64(-x)))
end
function tmp = code(x)
	tmp = (exp(x) - 2.0) + exp(-x);
end
code[x_] := N[(N[(N[Exp[x], $MachinePrecision] - 2.0), $MachinePrecision] + N[Exp[(-x)], $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\left(e^{x} - 2\right) + e^{-x}
\end{array}

Alternative 1: 99.2% accurate, 4.8× speedup?

\[\begin{array}{l} \\ \mathsf{fma}\left(\left(x \cdot x\right) \cdot x, \mathsf{fma}\left(\mathsf{fma}\left(4.96031746031746 \cdot 10^{-5}, x \cdot x, 0.002777777777777778\right), x \cdot x, 0.08333333333333333\right), x\right) \cdot x \end{array} \]
(FPCore (x)
 :precision binary64
 (*
  (fma
   (* (* x x) x)
   (fma
    (fma 4.96031746031746e-5 (* x x) 0.002777777777777778)
    (* x x)
    0.08333333333333333)
   x)
  x))
double code(double x) {
	return fma(((x * x) * x), fma(fma(4.96031746031746e-5, (x * x), 0.002777777777777778), (x * x), 0.08333333333333333), x) * x;
}
function code(x)
	return Float64(fma(Float64(Float64(x * x) * x), fma(fma(4.96031746031746e-5, Float64(x * x), 0.002777777777777778), Float64(x * x), 0.08333333333333333), x) * x)
end
code[x_] := N[(N[(N[(N[(x * x), $MachinePrecision] * x), $MachinePrecision] * N[(N[(4.96031746031746e-5 * N[(x * x), $MachinePrecision] + 0.002777777777777778), $MachinePrecision] * N[(x * x), $MachinePrecision] + 0.08333333333333333), $MachinePrecision] + x), $MachinePrecision] * x), $MachinePrecision]
\begin{array}{l}

\\
\mathsf{fma}\left(\left(x \cdot x\right) \cdot x, \mathsf{fma}\left(\mathsf{fma}\left(4.96031746031746 \cdot 10^{-5}, x \cdot x, 0.002777777777777778\right), x \cdot x, 0.08333333333333333\right), x\right) \cdot x
\end{array}
Derivation
  1. Initial program 51.4%

    \[\left(e^{x} - 2\right) + e^{-x} \]
  2. Add Preprocessing
  3. Taylor expanded in x around 0

    \[\leadsto \color{blue}{{x}^{2} \cdot \left(1 + {x}^{2} \cdot \left(\frac{1}{12} + {x}^{2} \cdot \left(\frac{1}{360} + \frac{1}{20160} \cdot {x}^{2}\right)\right)\right)} \]
  4. Step-by-step derivation
    1. *-commutativeN/A

      \[\leadsto \color{blue}{\left(1 + {x}^{2} \cdot \left(\frac{1}{12} + {x}^{2} \cdot \left(\frac{1}{360} + \frac{1}{20160} \cdot {x}^{2}\right)\right)\right) \cdot {x}^{2}} \]
    2. unpow2N/A

      \[\leadsto \left(1 + {x}^{2} \cdot \left(\frac{1}{12} + {x}^{2} \cdot \left(\frac{1}{360} + \frac{1}{20160} \cdot {x}^{2}\right)\right)\right) \cdot \color{blue}{\left(x \cdot x\right)} \]
    3. associate-*r*N/A

      \[\leadsto \color{blue}{\left(\left(1 + {x}^{2} \cdot \left(\frac{1}{12} + {x}^{2} \cdot \left(\frac{1}{360} + \frac{1}{20160} \cdot {x}^{2}\right)\right)\right) \cdot x\right) \cdot x} \]
    4. lower-*.f64N/A

      \[\leadsto \color{blue}{\left(\left(1 + {x}^{2} \cdot \left(\frac{1}{12} + {x}^{2} \cdot \left(\frac{1}{360} + \frac{1}{20160} \cdot {x}^{2}\right)\right)\right) \cdot x\right) \cdot x} \]
  5. Applied rewrites99.3%

    \[\leadsto \color{blue}{\mathsf{fma}\left({x}^{3}, \mathsf{fma}\left(\mathsf{fma}\left(4.96031746031746 \cdot 10^{-5}, x \cdot x, 0.002777777777777778\right), x \cdot x, 0.08333333333333333\right), x\right) \cdot x} \]
  6. Step-by-step derivation
    1. Applied rewrites99.3%

      \[\leadsto \mathsf{fma}\left(\left(x \cdot x\right) \cdot x, \mathsf{fma}\left(\mathsf{fma}\left(4.96031746031746 \cdot 10^{-5}, x \cdot x, 0.002777777777777778\right), x \cdot x, 0.08333333333333333\right), x\right) \cdot x \]
    2. Add Preprocessing

    Alternative 2: 99.1% accurate, 6.3× speedup?

    \[\begin{array}{l} \\ \left(\mathsf{fma}\left(\mathsf{fma}\left(0.002777777777777778, x \cdot x, 0.08333333333333333\right), x \cdot x, 1\right) \cdot x\right) \cdot x \end{array} \]
    (FPCore (x)
     :precision binary64
     (*
      (*
       (fma (fma 0.002777777777777778 (* x x) 0.08333333333333333) (* x x) 1.0)
       x)
      x))
    double code(double x) {
    	return (fma(fma(0.002777777777777778, (x * x), 0.08333333333333333), (x * x), 1.0) * x) * x;
    }
    
    function code(x)
    	return Float64(Float64(fma(fma(0.002777777777777778, Float64(x * x), 0.08333333333333333), Float64(x * x), 1.0) * x) * x)
    end
    
    code[x_] := N[(N[(N[(N[(0.002777777777777778 * N[(x * x), $MachinePrecision] + 0.08333333333333333), $MachinePrecision] * N[(x * x), $MachinePrecision] + 1.0), $MachinePrecision] * x), $MachinePrecision] * x), $MachinePrecision]
    
    \begin{array}{l}
    
    \\
    \left(\mathsf{fma}\left(\mathsf{fma}\left(0.002777777777777778, x \cdot x, 0.08333333333333333\right), x \cdot x, 1\right) \cdot x\right) \cdot x
    \end{array}
    
    Derivation
    1. Initial program 51.4%

      \[\left(e^{x} - 2\right) + e^{-x} \]
    2. Add Preprocessing
    3. Taylor expanded in x around 0

      \[\leadsto \color{blue}{{x}^{2} \cdot \left(1 + {x}^{2} \cdot \left(\frac{1}{12} + \frac{1}{360} \cdot {x}^{2}\right)\right)} \]
    4. Step-by-step derivation
      1. unpow2N/A

        \[\leadsto \color{blue}{\left(x \cdot x\right)} \cdot \left(1 + {x}^{2} \cdot \left(\frac{1}{12} + \frac{1}{360} \cdot {x}^{2}\right)\right) \]
      2. associate-*l*N/A

        \[\leadsto \color{blue}{x \cdot \left(x \cdot \left(1 + {x}^{2} \cdot \left(\frac{1}{12} + \frac{1}{360} \cdot {x}^{2}\right)\right)\right)} \]
      3. *-commutativeN/A

        \[\leadsto \color{blue}{\left(x \cdot \left(1 + {x}^{2} \cdot \left(\frac{1}{12} + \frac{1}{360} \cdot {x}^{2}\right)\right)\right) \cdot x} \]
      4. lower-*.f64N/A

        \[\leadsto \color{blue}{\left(x \cdot \left(1 + {x}^{2} \cdot \left(\frac{1}{12} + \frac{1}{360} \cdot {x}^{2}\right)\right)\right) \cdot x} \]
      5. +-commutativeN/A

        \[\leadsto \left(x \cdot \color{blue}{\left({x}^{2} \cdot \left(\frac{1}{12} + \frac{1}{360} \cdot {x}^{2}\right) + 1\right)}\right) \cdot x \]
      6. distribute-lft-inN/A

        \[\leadsto \color{blue}{\left(x \cdot \left({x}^{2} \cdot \left(\frac{1}{12} + \frac{1}{360} \cdot {x}^{2}\right)\right) + x \cdot 1\right)} \cdot x \]
      7. associate-*r*N/A

        \[\leadsto \left(\color{blue}{\left(x \cdot {x}^{2}\right) \cdot \left(\frac{1}{12} + \frac{1}{360} \cdot {x}^{2}\right)} + x \cdot 1\right) \cdot x \]
      8. *-rgt-identityN/A

        \[\leadsto \left(\left(x \cdot {x}^{2}\right) \cdot \left(\frac{1}{12} + \frac{1}{360} \cdot {x}^{2}\right) + \color{blue}{x}\right) \cdot x \]
      9. lower-fma.f64N/A

        \[\leadsto \color{blue}{\mathsf{fma}\left(x \cdot {x}^{2}, \frac{1}{12} + \frac{1}{360} \cdot {x}^{2}, x\right)} \cdot x \]
      10. unpow2N/A

        \[\leadsto \mathsf{fma}\left(x \cdot \color{blue}{\left(x \cdot x\right)}, \frac{1}{12} + \frac{1}{360} \cdot {x}^{2}, x\right) \cdot x \]
      11. cube-unmultN/A

        \[\leadsto \mathsf{fma}\left(\color{blue}{{x}^{3}}, \frac{1}{12} + \frac{1}{360} \cdot {x}^{2}, x\right) \cdot x \]
      12. metadata-evalN/A

        \[\leadsto \mathsf{fma}\left({x}^{\color{blue}{\left(2 + 1\right)}}, \frac{1}{12} + \frac{1}{360} \cdot {x}^{2}, x\right) \cdot x \]
      13. lower-pow.f64N/A

        \[\leadsto \mathsf{fma}\left(\color{blue}{{x}^{\left(2 + 1\right)}}, \frac{1}{12} + \frac{1}{360} \cdot {x}^{2}, x\right) \cdot x \]
      14. metadata-evalN/A

        \[\leadsto \mathsf{fma}\left({x}^{\color{blue}{3}}, \frac{1}{12} + \frac{1}{360} \cdot {x}^{2}, x\right) \cdot x \]
      15. +-commutativeN/A

        \[\leadsto \mathsf{fma}\left({x}^{3}, \color{blue}{\frac{1}{360} \cdot {x}^{2} + \frac{1}{12}}, x\right) \cdot x \]
      16. lower-fma.f64N/A

        \[\leadsto \mathsf{fma}\left({x}^{3}, \color{blue}{\mathsf{fma}\left(\frac{1}{360}, {x}^{2}, \frac{1}{12}\right)}, x\right) \cdot x \]
      17. unpow2N/A

        \[\leadsto \mathsf{fma}\left({x}^{3}, \mathsf{fma}\left(\frac{1}{360}, \color{blue}{x \cdot x}, \frac{1}{12}\right), x\right) \cdot x \]
      18. lower-*.f6499.2

        \[\leadsto \mathsf{fma}\left({x}^{3}, \mathsf{fma}\left(0.002777777777777778, \color{blue}{x \cdot x}, 0.08333333333333333\right), x\right) \cdot x \]
    5. Applied rewrites99.2%

      \[\leadsto \color{blue}{\mathsf{fma}\left({x}^{3}, \mathsf{fma}\left(0.002777777777777778, x \cdot x, 0.08333333333333333\right), x\right) \cdot x} \]
    6. Step-by-step derivation
      1. Applied rewrites99.2%

        \[\leadsto \mathsf{fma}\left(\mathsf{fma}\left(0.002777777777777778, x \cdot x, 0.08333333333333333\right) \cdot \left(x \cdot x\right), x, x\right) \cdot x \]
      2. Step-by-step derivation
        1. Applied rewrites99.2%

          \[\leadsto \left(\mathsf{fma}\left(\mathsf{fma}\left(0.002777777777777778, x \cdot x, 0.08333333333333333\right), x \cdot x, 1\right) \cdot x\right) \cdot x \]
        2. Add Preprocessing

        Alternative 3: 98.9% accurate, 7.7× speedup?

        \[\begin{array}{l} \\ \mathsf{fma}\left(\left(x \cdot x\right) \cdot \left(x \cdot x\right), 0.08333333333333333, x \cdot x\right) \end{array} \]
        (FPCore (x)
         :precision binary64
         (fma (* (* x x) (* x x)) 0.08333333333333333 (* x x)))
        double code(double x) {
        	return fma(((x * x) * (x * x)), 0.08333333333333333, (x * x));
        }
        
        function code(x)
        	return fma(Float64(Float64(x * x) * Float64(x * x)), 0.08333333333333333, Float64(x * x))
        end
        
        code[x_] := N[(N[(N[(x * x), $MachinePrecision] * N[(x * x), $MachinePrecision]), $MachinePrecision] * 0.08333333333333333 + N[(x * x), $MachinePrecision]), $MachinePrecision]
        
        \begin{array}{l}
        
        \\
        \mathsf{fma}\left(\left(x \cdot x\right) \cdot \left(x \cdot x\right), 0.08333333333333333, x \cdot x\right)
        \end{array}
        
        Derivation
        1. Initial program 51.4%

          \[\left(e^{x} - 2\right) + e^{-x} \]
        2. Add Preprocessing
        3. Taylor expanded in x around 0

          \[\leadsto \color{blue}{{x}^{2} \cdot \left(1 + \frac{1}{12} \cdot {x}^{2}\right)} \]
        4. Step-by-step derivation
          1. +-commutativeN/A

            \[\leadsto {x}^{2} \cdot \color{blue}{\left(\frac{1}{12} \cdot {x}^{2} + 1\right)} \]
          2. distribute-lft-inN/A

            \[\leadsto \color{blue}{{x}^{2} \cdot \left(\frac{1}{12} \cdot {x}^{2}\right) + {x}^{2} \cdot 1} \]
          3. *-commutativeN/A

            \[\leadsto {x}^{2} \cdot \color{blue}{\left({x}^{2} \cdot \frac{1}{12}\right)} + {x}^{2} \cdot 1 \]
          4. associate-*r*N/A

            \[\leadsto \color{blue}{\left({x}^{2} \cdot {x}^{2}\right) \cdot \frac{1}{12}} + {x}^{2} \cdot 1 \]
          5. *-rgt-identityN/A

            \[\leadsto \left({x}^{2} \cdot {x}^{2}\right) \cdot \frac{1}{12} + \color{blue}{{x}^{2}} \]
          6. lower-fma.f64N/A

            \[\leadsto \color{blue}{\mathsf{fma}\left({x}^{2} \cdot {x}^{2}, \frac{1}{12}, {x}^{2}\right)} \]
          7. pow-sqrN/A

            \[\leadsto \mathsf{fma}\left(\color{blue}{{x}^{\left(2 \cdot 2\right)}}, \frac{1}{12}, {x}^{2}\right) \]
          8. lower-pow.f64N/A

            \[\leadsto \mathsf{fma}\left(\color{blue}{{x}^{\left(2 \cdot 2\right)}}, \frac{1}{12}, {x}^{2}\right) \]
          9. metadata-evalN/A

            \[\leadsto \mathsf{fma}\left({x}^{\color{blue}{4}}, \frac{1}{12}, {x}^{2}\right) \]
          10. unpow2N/A

            \[\leadsto \mathsf{fma}\left({x}^{4}, \frac{1}{12}, \color{blue}{x \cdot x}\right) \]
          11. lower-*.f6499.1

            \[\leadsto \mathsf{fma}\left({x}^{4}, 0.08333333333333333, \color{blue}{x \cdot x}\right) \]
        5. Applied rewrites99.1%

          \[\leadsto \color{blue}{\mathsf{fma}\left({x}^{4}, 0.08333333333333333, x \cdot x\right)} \]
        6. Step-by-step derivation
          1. Applied rewrites99.1%

            \[\leadsto \mathsf{fma}\left(\left(x \cdot x\right) \cdot \left(x \cdot x\right), 0.08333333333333333, x \cdot x\right) \]
          2. Add Preprocessing

          Alternative 4: 98.9% accurate, 9.5× speedup?

          \[\begin{array}{l} \\ \mathsf{fma}\left(\left(x \cdot x\right) \cdot x, 0.08333333333333333, x\right) \cdot x \end{array} \]
          (FPCore (x)
           :precision binary64
           (* (fma (* (* x x) x) 0.08333333333333333 x) x))
          double code(double x) {
          	return fma(((x * x) * x), 0.08333333333333333, x) * x;
          }
          
          function code(x)
          	return Float64(fma(Float64(Float64(x * x) * x), 0.08333333333333333, x) * x)
          end
          
          code[x_] := N[(N[(N[(N[(x * x), $MachinePrecision] * x), $MachinePrecision] * 0.08333333333333333 + x), $MachinePrecision] * x), $MachinePrecision]
          
          \begin{array}{l}
          
          \\
          \mathsf{fma}\left(\left(x \cdot x\right) \cdot x, 0.08333333333333333, x\right) \cdot x
          \end{array}
          
          Derivation
          1. Initial program 51.4%

            \[\left(e^{x} - 2\right) + e^{-x} \]
          2. Add Preprocessing
          3. Taylor expanded in x around 0

            \[\leadsto \color{blue}{{x}^{2} \cdot \left(1 + {x}^{2} \cdot \left(\frac{1}{12} + {x}^{2} \cdot \left(\frac{1}{360} + \frac{1}{20160} \cdot {x}^{2}\right)\right)\right)} \]
          4. Step-by-step derivation
            1. *-commutativeN/A

              \[\leadsto \color{blue}{\left(1 + {x}^{2} \cdot \left(\frac{1}{12} + {x}^{2} \cdot \left(\frac{1}{360} + \frac{1}{20160} \cdot {x}^{2}\right)\right)\right) \cdot {x}^{2}} \]
            2. unpow2N/A

              \[\leadsto \left(1 + {x}^{2} \cdot \left(\frac{1}{12} + {x}^{2} \cdot \left(\frac{1}{360} + \frac{1}{20160} \cdot {x}^{2}\right)\right)\right) \cdot \color{blue}{\left(x \cdot x\right)} \]
            3. associate-*r*N/A

              \[\leadsto \color{blue}{\left(\left(1 + {x}^{2} \cdot \left(\frac{1}{12} + {x}^{2} \cdot \left(\frac{1}{360} + \frac{1}{20160} \cdot {x}^{2}\right)\right)\right) \cdot x\right) \cdot x} \]
            4. lower-*.f64N/A

              \[\leadsto \color{blue}{\left(\left(1 + {x}^{2} \cdot \left(\frac{1}{12} + {x}^{2} \cdot \left(\frac{1}{360} + \frac{1}{20160} \cdot {x}^{2}\right)\right)\right) \cdot x\right) \cdot x} \]
          5. Applied rewrites99.3%

            \[\leadsto \color{blue}{\mathsf{fma}\left({x}^{3}, \mathsf{fma}\left(\mathsf{fma}\left(4.96031746031746 \cdot 10^{-5}, x \cdot x, 0.002777777777777778\right), x \cdot x, 0.08333333333333333\right), x\right) \cdot x} \]
          6. Step-by-step derivation
            1. Applied rewrites99.3%

              \[\leadsto \mathsf{fma}\left(\left(x \cdot x\right) \cdot x, \mathsf{fma}\left(\mathsf{fma}\left(4.96031746031746 \cdot 10^{-5}, x \cdot x, 0.002777777777777778\right), x \cdot x, 0.08333333333333333\right), x\right) \cdot x \]
            2. Taylor expanded in x around 0

              \[\leadsto \mathsf{fma}\left(\left(x \cdot x\right) \cdot x, \frac{1}{12}, x\right) \cdot x \]
            3. Step-by-step derivation
              1. Applied rewrites99.1%

                \[\leadsto \mathsf{fma}\left(\left(x \cdot x\right) \cdot x, 0.08333333333333333, x\right) \cdot x \]
              2. Add Preprocessing

              Alternative 5: 98.4% accurate, 34.8× speedup?

              \[\begin{array}{l} \\ x \cdot x \end{array} \]
              (FPCore (x) :precision binary64 (* x x))
              double code(double x) {
              	return x * x;
              }
              
              real(8) function code(x)
                  real(8), intent (in) :: x
                  code = x * x
              end function
              
              public static double code(double x) {
              	return x * x;
              }
              
              def code(x):
              	return x * x
              
              function code(x)
              	return Float64(x * x)
              end
              
              function tmp = code(x)
              	tmp = x * x;
              end
              
              code[x_] := N[(x * x), $MachinePrecision]
              
              \begin{array}{l}
              
              \\
              x \cdot x
              \end{array}
              
              Derivation
              1. Initial program 51.4%

                \[\left(e^{x} - 2\right) + e^{-x} \]
              2. Add Preprocessing
              3. Taylor expanded in x around 0

                \[\leadsto \color{blue}{{x}^{2}} \]
              4. Step-by-step derivation
                1. unpow2N/A

                  \[\leadsto \color{blue}{x \cdot x} \]
                2. lower-*.f6498.8

                  \[\leadsto \color{blue}{x \cdot x} \]
              5. Applied rewrites98.8%

                \[\leadsto \color{blue}{x \cdot x} \]
              6. Add Preprocessing

              Alternative 6: 50.3% accurate, 52.3× speedup?

              \[\begin{array}{l} \\ 2 - 2 \end{array} \]
              (FPCore (x) :precision binary64 (- 2.0 2.0))
              double code(double x) {
              	return 2.0 - 2.0;
              }
              
              real(8) function code(x)
                  real(8), intent (in) :: x
                  code = 2.0d0 - 2.0d0
              end function
              
              public static double code(double x) {
              	return 2.0 - 2.0;
              }
              
              def code(x):
              	return 2.0 - 2.0
              
              function code(x)
              	return Float64(2.0 - 2.0)
              end
              
              function tmp = code(x)
              	tmp = 2.0 - 2.0;
              end
              
              code[x_] := N[(2.0 - 2.0), $MachinePrecision]
              
              \begin{array}{l}
              
              \\
              2 - 2
              \end{array}
              
              Derivation
              1. Initial program 51.4%

                \[\left(e^{x} - 2\right) + e^{-x} \]
              2. Add Preprocessing
              3. Step-by-step derivation
                1. lift-+.f64N/A

                  \[\leadsto \color{blue}{\left(e^{x} - 2\right) + e^{-x}} \]
                2. +-commutativeN/A

                  \[\leadsto \color{blue}{e^{-x} + \left(e^{x} - 2\right)} \]
                3. lift--.f64N/A

                  \[\leadsto e^{-x} + \color{blue}{\left(e^{x} - 2\right)} \]
                4. associate-+r-N/A

                  \[\leadsto \color{blue}{\left(e^{-x} + e^{x}\right) - 2} \]
                5. +-commutativeN/A

                  \[\leadsto \color{blue}{\left(e^{x} + e^{-x}\right)} - 2 \]
                6. lift-exp.f64N/A

                  \[\leadsto \left(\color{blue}{e^{x}} + e^{-x}\right) - 2 \]
                7. lift-exp.f64N/A

                  \[\leadsto \left(e^{x} + \color{blue}{e^{-x}}\right) - 2 \]
                8. lift-neg.f64N/A

                  \[\leadsto \left(e^{x} + e^{\color{blue}{\mathsf{neg}\left(x\right)}}\right) - 2 \]
                9. lower--.f64N/A

                  \[\leadsto \color{blue}{\left(e^{x} + e^{\mathsf{neg}\left(x\right)}\right) - 2} \]
                10. cosh-undefN/A

                  \[\leadsto \color{blue}{2 \cdot \cosh x} - 2 \]
                11. lower-*.f64N/A

                  \[\leadsto \color{blue}{2 \cdot \cosh x} - 2 \]
                12. lower-cosh.f6451.3

                  \[\leadsto 2 \cdot \color{blue}{\cosh x} - 2 \]
              4. Applied rewrites51.3%

                \[\leadsto \color{blue}{2 \cdot \cosh x - 2} \]
              5. Taylor expanded in x around 0

                \[\leadsto \color{blue}{2} - 2 \]
              6. Step-by-step derivation
                1. Applied rewrites49.6%

                  \[\leadsto \color{blue}{2} - 2 \]
                2. Add Preprocessing

                Developer Target 1: 99.9% accurate, 0.9× speedup?

                \[\begin{array}{l} \\ \begin{array}{l} t_0 := \sinh \left(\frac{x}{2}\right)\\ 4 \cdot \left(t\_0 \cdot t\_0\right) \end{array} \end{array} \]
                (FPCore (x)
                 :precision binary64
                 (let* ((t_0 (sinh (/ x 2.0)))) (* 4.0 (* t_0 t_0))))
                double code(double x) {
                	double t_0 = sinh((x / 2.0));
                	return 4.0 * (t_0 * t_0);
                }
                
                real(8) function code(x)
                    real(8), intent (in) :: x
                    real(8) :: t_0
                    t_0 = sinh((x / 2.0d0))
                    code = 4.0d0 * (t_0 * t_0)
                end function
                
                public static double code(double x) {
                	double t_0 = Math.sinh((x / 2.0));
                	return 4.0 * (t_0 * t_0);
                }
                
                def code(x):
                	t_0 = math.sinh((x / 2.0))
                	return 4.0 * (t_0 * t_0)
                
                function code(x)
                	t_0 = sinh(Float64(x / 2.0))
                	return Float64(4.0 * Float64(t_0 * t_0))
                end
                
                function tmp = code(x)
                	t_0 = sinh((x / 2.0));
                	tmp = 4.0 * (t_0 * t_0);
                end
                
                code[x_] := Block[{t$95$0 = N[Sinh[N[(x / 2.0), $MachinePrecision]], $MachinePrecision]}, N[(4.0 * N[(t$95$0 * t$95$0), $MachinePrecision]), $MachinePrecision]]
                
                \begin{array}{l}
                
                \\
                \begin{array}{l}
                t_0 := \sinh \left(\frac{x}{2}\right)\\
                4 \cdot \left(t\_0 \cdot t\_0\right)
                \end{array}
                \end{array}
                

                Reproduce

                ?
                herbie shell --seed 2024340 
                (FPCore (x)
                  :name "exp2 (problem 3.3.7)"
                  :precision binary64
                  :pre (<= (fabs x) 710.0)
                
                  :alt
                  (! :herbie-platform default (* 4 (* (sinh (/ x 2)) (sinh (/ x 2)))))
                
                  (+ (- (exp x) 2.0) (exp (- x))))