Rust f64::atanh

Percentage Accurate: 100.0% → 100.0%
Time: 3.1s
Alternatives: 7
Speedup: 1.0×

Specification

?
\[\begin{array}{l} \\ \tanh^{-1} x \end{array} \]
(FPCore (x) :precision binary64 (atanh x))
double code(double x) {
	return atanh(x);
}
def code(x):
	return math.atanh(x)
function code(x)
	return atanh(x)
end
function tmp = code(x)
	tmp = atanh(x);
end
code[x_] := N[ArcTanh[x], $MachinePrecision]
\begin{array}{l}

\\
\tanh^{-1} 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 7 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: 100.0% accurate, 1.0× speedup?

\[\begin{array}{l} \\ 0.5 \cdot \mathsf{log1p}\left(\frac{2 \cdot x}{1 - x}\right) \end{array} \]
(FPCore (x) :precision binary64 (* 0.5 (log1p (/ (* 2.0 x) (- 1.0 x)))))
double code(double x) {
	return 0.5 * log1p(((2.0 * x) / (1.0 - x)));
}
public static double code(double x) {
	return 0.5 * Math.log1p(((2.0 * x) / (1.0 - x)));
}
def code(x):
	return 0.5 * math.log1p(((2.0 * x) / (1.0 - x)))
function code(x)
	return Float64(0.5 * log1p(Float64(Float64(2.0 * x) / Float64(1.0 - x))))
end
code[x_] := N[(0.5 * N[Log[1 + N[(N[(2.0 * x), $MachinePrecision] / N[(1.0 - x), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
0.5 \cdot \mathsf{log1p}\left(\frac{2 \cdot x}{1 - x}\right)
\end{array}

Alternative 1: 100.0% accurate, 1.0× speedup?

\[\begin{array}{l} \\ 0.5 \cdot \mathsf{log1p}\left(\frac{x + x}{1 - x}\right) \end{array} \]
(FPCore (x) :precision binary64 (* 0.5 (log1p (/ (+ x x) (- 1.0 x)))))
double code(double x) {
	return 0.5 * log1p(((x + x) / (1.0 - x)));
}
public static double code(double x) {
	return 0.5 * Math.log1p(((x + x) / (1.0 - x)));
}
def code(x):
	return 0.5 * math.log1p(((x + x) / (1.0 - x)))
function code(x)
	return Float64(0.5 * log1p(Float64(Float64(x + x) / Float64(1.0 - x))))
end
code[x_] := N[(0.5 * N[Log[1 + N[(N[(x + x), $MachinePrecision] / N[(1.0 - x), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
0.5 \cdot \mathsf{log1p}\left(\frac{x + x}{1 - x}\right)
\end{array}
Derivation
  1. Initial program 100.0%

    \[0.5 \cdot \mathsf{log1p}\left(\frac{2 \cdot x}{1 - x}\right) \]
  2. Add Preprocessing
  3. Step-by-step derivation
    1. lift-*.f64N/A

      \[\leadsto \frac{1}{2} \cdot \mathsf{log1p}\left(\frac{\color{blue}{2 \cdot x}}{1 - x}\right) \]
    2. count-2-revN/A

      \[\leadsto \frac{1}{2} \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
    3. lower-+.f64100.0

      \[\leadsto 0.5 \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
  4. Applied rewrites100.0%

    \[\leadsto 0.5 \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
  5. Add Preprocessing

Alternative 2: 99.8% accurate, 3.2× speedup?

\[\begin{array}{l} \\ \mathsf{fma}\left(\left(\mathsf{fma}\left(\mathsf{fma}\left(x \cdot x, 0.14285714285714285, 0.2\right), x \cdot x, 0.3333333333333333\right) \cdot x\right) \cdot x, x, x\right) \end{array} \]
(FPCore (x)
 :precision binary64
 (fma
  (*
   (* (fma (fma (* x x) 0.14285714285714285 0.2) (* x x) 0.3333333333333333) x)
   x)
  x
  x))
double code(double x) {
	return fma(((fma(fma((x * x), 0.14285714285714285, 0.2), (x * x), 0.3333333333333333) * x) * x), x, x);
}
function code(x)
	return fma(Float64(Float64(fma(fma(Float64(x * x), 0.14285714285714285, 0.2), Float64(x * x), 0.3333333333333333) * x) * x), x, x)
end
code[x_] := N[(N[(N[(N[(N[(N[(x * x), $MachinePrecision] * 0.14285714285714285 + 0.2), $MachinePrecision] * N[(x * x), $MachinePrecision] + 0.3333333333333333), $MachinePrecision] * x), $MachinePrecision] * x), $MachinePrecision] * x + x), $MachinePrecision]
\begin{array}{l}

\\
\mathsf{fma}\left(\left(\mathsf{fma}\left(\mathsf{fma}\left(x \cdot x, 0.14285714285714285, 0.2\right), x \cdot x, 0.3333333333333333\right) \cdot x\right) \cdot x, x, x\right)
\end{array}
Derivation
  1. Initial program 100.0%

    \[0.5 \cdot \mathsf{log1p}\left(\frac{2 \cdot x}{1 - x}\right) \]
  2. Add Preprocessing
  3. Step-by-step derivation
    1. lift-*.f64N/A

      \[\leadsto \frac{1}{2} \cdot \mathsf{log1p}\left(\frac{\color{blue}{2 \cdot x}}{1 - x}\right) \]
    2. count-2-revN/A

      \[\leadsto \frac{1}{2} \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
    3. lower-+.f64100.0

      \[\leadsto 0.5 \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
  4. Applied rewrites100.0%

    \[\leadsto 0.5 \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
  5. Taylor expanded in x around 0

    \[\leadsto \color{blue}{x \cdot \left(1 + {x}^{2} \cdot \left(\frac{1}{3} + {x}^{2} \cdot \left(\frac{1}{5} + \frac{1}{7} \cdot {x}^{2}\right)\right)\right)} \]
  6. Step-by-step derivation
    1. Applied rewrites99.6%

      \[\leadsto \color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(0.14285714285714285, x \cdot x, 0.2\right), x \cdot x, 0.3333333333333333\right), x \cdot x, 1\right) \cdot x} \]
    2. Step-by-step derivation
      1. Applied rewrites99.6%

        \[\leadsto \mathsf{fma}\left(x, \color{blue}{1}, x \cdot \left(\left(\mathsf{fma}\left(\mathsf{fma}\left(0.14285714285714285, x \cdot x, 0.2\right), x \cdot x, 0.3333333333333333\right) \cdot x\right) \cdot x\right)\right) \]
      2. Applied rewrites99.6%

        \[\leadsto \color{blue}{\mathsf{fma}\left(\left(\mathsf{fma}\left(\mathsf{fma}\left(x \cdot x, 0.14285714285714285, 0.2\right), x \cdot x, 0.3333333333333333\right) \cdot x\right) \cdot x, x, x\right)} \]
      3. Add Preprocessing

      Alternative 3: 99.7% accurate, 3.2× speedup?

      \[\begin{array}{l} \\ \mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(0.14285714285714285, x \cdot x, 0.2\right), x \cdot x, 0.3333333333333333\right), x \cdot x, 1\right) \cdot x \end{array} \]
      (FPCore (x)
       :precision binary64
       (*
        (fma
         (fma (fma 0.14285714285714285 (* x x) 0.2) (* x x) 0.3333333333333333)
         (* x x)
         1.0)
        x))
      double code(double x) {
      	return fma(fma(fma(0.14285714285714285, (x * x), 0.2), (x * x), 0.3333333333333333), (x * x), 1.0) * x;
      }
      
      function code(x)
      	return Float64(fma(fma(fma(0.14285714285714285, Float64(x * x), 0.2), Float64(x * x), 0.3333333333333333), Float64(x * x), 1.0) * x)
      end
      
      code[x_] := N[(N[(N[(N[(0.14285714285714285 * N[(x * x), $MachinePrecision] + 0.2), $MachinePrecision] * N[(x * x), $MachinePrecision] + 0.3333333333333333), $MachinePrecision] * N[(x * x), $MachinePrecision] + 1.0), $MachinePrecision] * x), $MachinePrecision]
      
      \begin{array}{l}
      
      \\
      \mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(0.14285714285714285, x \cdot x, 0.2\right), x \cdot x, 0.3333333333333333\right), x \cdot x, 1\right) \cdot x
      \end{array}
      
      Derivation
      1. Initial program 100.0%

        \[0.5 \cdot \mathsf{log1p}\left(\frac{2 \cdot x}{1 - x}\right) \]
      2. Add Preprocessing
      3. Step-by-step derivation
        1. lift-*.f64N/A

          \[\leadsto \frac{1}{2} \cdot \mathsf{log1p}\left(\frac{\color{blue}{2 \cdot x}}{1 - x}\right) \]
        2. count-2-revN/A

          \[\leadsto \frac{1}{2} \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
        3. lower-+.f64100.0

          \[\leadsto 0.5 \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
      4. Applied rewrites100.0%

        \[\leadsto 0.5 \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
      5. Taylor expanded in x around 0

        \[\leadsto \color{blue}{x \cdot \left(1 + {x}^{2} \cdot \left(\frac{1}{3} + {x}^{2} \cdot \left(\frac{1}{5} + \frac{1}{7} \cdot {x}^{2}\right)\right)\right)} \]
      6. Step-by-step derivation
        1. Applied rewrites99.6%

          \[\leadsto \color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(\mathsf{fma}\left(0.14285714285714285, x \cdot x, 0.2\right), x \cdot x, 0.3333333333333333\right), x \cdot x, 1\right) \cdot x} \]
        2. Add Preprocessing

        Alternative 4: 99.7% accurate, 4.5× speedup?

        \[\begin{array}{l} \\ \mathsf{fma}\left(\mathsf{fma}\left(0.2, x \cdot x, 0.3333333333333333\right), x \cdot x, 1\right) \cdot x \end{array} \]
        (FPCore (x)
         :precision binary64
         (* (fma (fma 0.2 (* x x) 0.3333333333333333) (* x x) 1.0) x))
        double code(double x) {
        	return fma(fma(0.2, (x * x), 0.3333333333333333), (x * x), 1.0) * x;
        }
        
        function code(x)
        	return Float64(fma(fma(0.2, Float64(x * x), 0.3333333333333333), Float64(x * x), 1.0) * x)
        end
        
        code[x_] := N[(N[(N[(0.2 * N[(x * x), $MachinePrecision] + 0.3333333333333333), $MachinePrecision] * N[(x * x), $MachinePrecision] + 1.0), $MachinePrecision] * x), $MachinePrecision]
        
        \begin{array}{l}
        
        \\
        \mathsf{fma}\left(\mathsf{fma}\left(0.2, x \cdot x, 0.3333333333333333\right), x \cdot x, 1\right) \cdot x
        \end{array}
        
        Derivation
        1. Initial program 100.0%

          \[0.5 \cdot \mathsf{log1p}\left(\frac{2 \cdot x}{1 - x}\right) \]
        2. Add Preprocessing
        3. Step-by-step derivation
          1. lift-*.f64N/A

            \[\leadsto \frac{1}{2} \cdot \mathsf{log1p}\left(\frac{\color{blue}{2 \cdot x}}{1 - x}\right) \]
          2. count-2-revN/A

            \[\leadsto \frac{1}{2} \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
          3. lower-+.f64100.0

            \[\leadsto 0.5 \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
        4. Applied rewrites100.0%

          \[\leadsto 0.5 \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
        5. Taylor expanded in x around 0

          \[\leadsto \color{blue}{x \cdot \left(1 + {x}^{2} \cdot \left(\frac{1}{3} + \frac{1}{5} \cdot {x}^{2}\right)\right)} \]
        6. Step-by-step derivation
          1. Applied rewrites99.5%

            \[\leadsto \color{blue}{\mathsf{fma}\left(\mathsf{fma}\left(0.2, x \cdot x, 0.3333333333333333\right), x \cdot x, 1\right) \cdot x} \]
          2. Add Preprocessing

          Alternative 5: 99.5% accurate, 7.4× speedup?

          \[\begin{array}{l} \\ \mathsf{fma}\left(\left(x \cdot x\right) \cdot 0.3333333333333333, x, x\right) \end{array} \]
          (FPCore (x) :precision binary64 (fma (* (* x x) 0.3333333333333333) x x))
          double code(double x) {
          	return fma(((x * x) * 0.3333333333333333), x, x);
          }
          
          function code(x)
          	return fma(Float64(Float64(x * x) * 0.3333333333333333), x, x)
          end
          
          code[x_] := N[(N[(N[(x * x), $MachinePrecision] * 0.3333333333333333), $MachinePrecision] * x + x), $MachinePrecision]
          
          \begin{array}{l}
          
          \\
          \mathsf{fma}\left(\left(x \cdot x\right) \cdot 0.3333333333333333, x, x\right)
          \end{array}
          
          Derivation
          1. Initial program 100.0%

            \[0.5 \cdot \mathsf{log1p}\left(\frac{2 \cdot x}{1 - x}\right) \]
          2. Add Preprocessing
          3. Step-by-step derivation
            1. lift-*.f64N/A

              \[\leadsto \frac{1}{2} \cdot \mathsf{log1p}\left(\frac{\color{blue}{2 \cdot x}}{1 - x}\right) \]
            2. count-2-revN/A

              \[\leadsto \frac{1}{2} \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
            3. lower-+.f64100.0

              \[\leadsto 0.5 \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
          4. Applied rewrites100.0%

            \[\leadsto 0.5 \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
          5. Taylor expanded in x around 0

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

              \[\leadsto \color{blue}{\mathsf{fma}\left(x \cdot x, 0.3333333333333333, 1\right) \cdot x} \]
            2. Step-by-step derivation
              1. Applied rewrites99.2%

                \[\leadsto \mathsf{fma}\left(x, \color{blue}{1}, x \cdot \left(0.3333333333333333 \cdot \left(x \cdot x\right)\right)\right) \]
              2. Step-by-step derivation
                1. Applied rewrites99.2%

                  \[\leadsto \mathsf{fma}\left(\left(x \cdot x\right) \cdot 0.3333333333333333, \color{blue}{x}, x\right) \]
                2. Add Preprocessing

                Alternative 6: 99.5% accurate, 7.4× speedup?

                \[\begin{array}{l} \\ \mathsf{fma}\left(x \cdot x, 0.3333333333333333, 1\right) \cdot x \end{array} \]
                (FPCore (x) :precision binary64 (* (fma (* x x) 0.3333333333333333 1.0) x))
                double code(double x) {
                	return fma((x * x), 0.3333333333333333, 1.0) * x;
                }
                
                function code(x)
                	return Float64(fma(Float64(x * x), 0.3333333333333333, 1.0) * x)
                end
                
                code[x_] := N[(N[(N[(x * x), $MachinePrecision] * 0.3333333333333333 + 1.0), $MachinePrecision] * x), $MachinePrecision]
                
                \begin{array}{l}
                
                \\
                \mathsf{fma}\left(x \cdot x, 0.3333333333333333, 1\right) \cdot x
                \end{array}
                
                Derivation
                1. Initial program 100.0%

                  \[0.5 \cdot \mathsf{log1p}\left(\frac{2 \cdot x}{1 - x}\right) \]
                2. Add Preprocessing
                3. Step-by-step derivation
                  1. lift-*.f64N/A

                    \[\leadsto \frac{1}{2} \cdot \mathsf{log1p}\left(\frac{\color{blue}{2 \cdot x}}{1 - x}\right) \]
                  2. count-2-revN/A

                    \[\leadsto \frac{1}{2} \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
                  3. lower-+.f64100.0

                    \[\leadsto 0.5 \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
                4. Applied rewrites100.0%

                  \[\leadsto 0.5 \cdot \mathsf{log1p}\left(\frac{\color{blue}{x + x}}{1 - x}\right) \]
                5. Taylor expanded in x around 0

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

                    \[\leadsto \color{blue}{\mathsf{fma}\left(x \cdot x, 0.3333333333333333, 1\right) \cdot x} \]
                  2. Add Preprocessing

                  Alternative 7: 98.9% accurate, 125.0× speedup?

                  \[\begin{array}{l} \\ x \end{array} \]
                  (FPCore (x) :precision binary64 x)
                  double code(double x) {
                  	return 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 = x
                  end function
                  
                  public static double code(double x) {
                  	return x;
                  }
                  
                  def code(x):
                  	return x
                  
                  function code(x)
                  	return x
                  end
                  
                  function tmp = code(x)
                  	tmp = x;
                  end
                  
                  code[x_] := x
                  
                  \begin{array}{l}
                  
                  \\
                  x
                  \end{array}
                  
                  Derivation
                  1. Initial program 100.0%

                    \[0.5 \cdot \mathsf{log1p}\left(\frac{2 \cdot x}{1 - x}\right) \]
                  2. Add Preprocessing
                  3. Taylor expanded in x around 0

                    \[\leadsto \color{blue}{x} \]
                  4. Step-by-step derivation
                    1. Applied rewrites98.8%

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

                    Reproduce

                    ?
                    herbie shell --seed 2025025 
                    (FPCore (x)
                      :name "Rust f64::atanh"
                      :precision binary64
                      (* 0.5 (log1p (/ (* 2.0 x) (- 1.0 x)))))