Data.Array.Repa.Algorithms.Pixel:doubleRmsOfRGB8 from repa-algorithms-3.4.0.1

Percentage Accurate: 44.9% → 99.6%
Time: 7.5s
Alternatives: 4
Speedup: 2.7×

Specification

?
\[\begin{array}{l} \\ \sqrt{\frac{\left(x \cdot x + y \cdot y\right) + z \cdot z}{3}} \end{array} \]
(FPCore (x y z)
 :precision binary64
 (sqrt (/ (+ (+ (* x x) (* y y)) (* z z)) 3.0)))
double code(double x, double y, double z) {
	return sqrt(((((x * x) + (y * y)) + (z * z)) / 3.0));
}
real(8) function code(x, y, z)
    real(8), intent (in) :: x
    real(8), intent (in) :: y
    real(8), intent (in) :: z
    code = sqrt(((((x * x) + (y * y)) + (z * z)) / 3.0d0))
end function
public static double code(double x, double y, double z) {
	return Math.sqrt(((((x * x) + (y * y)) + (z * z)) / 3.0));
}
def code(x, y, z):
	return math.sqrt(((((x * x) + (y * y)) + (z * z)) / 3.0))
function code(x, y, z)
	return sqrt(Float64(Float64(Float64(Float64(x * x) + Float64(y * y)) + Float64(z * z)) / 3.0))
end
function tmp = code(x, y, z)
	tmp = sqrt(((((x * x) + (y * y)) + (z * z)) / 3.0));
end
code[x_, y_, z_] := N[Sqrt[N[(N[(N[(N[(x * x), $MachinePrecision] + N[(y * y), $MachinePrecision]), $MachinePrecision] + N[(z * z), $MachinePrecision]), $MachinePrecision] / 3.0), $MachinePrecision]], $MachinePrecision]
\begin{array}{l}

\\
\sqrt{\frac{\left(x \cdot x + y \cdot y\right) + z \cdot z}{3}}
\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: 44.9% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \sqrt{\frac{\left(x \cdot x + y \cdot y\right) + z \cdot z}{3}} \end{array} \]
(FPCore (x y z)
 :precision binary64
 (sqrt (/ (+ (+ (* x x) (* y y)) (* z z)) 3.0)))
double code(double x, double y, double z) {
	return sqrt(((((x * x) + (y * y)) + (z * z)) / 3.0));
}
real(8) function code(x, y, z)
    real(8), intent (in) :: x
    real(8), intent (in) :: y
    real(8), intent (in) :: z
    code = sqrt(((((x * x) + (y * y)) + (z * z)) / 3.0d0))
end function
public static double code(double x, double y, double z) {
	return Math.sqrt(((((x * x) + (y * y)) + (z * z)) / 3.0));
}
def code(x, y, z):
	return math.sqrt(((((x * x) + (y * y)) + (z * z)) / 3.0))
function code(x, y, z)
	return sqrt(Float64(Float64(Float64(Float64(x * x) + Float64(y * y)) + Float64(z * z)) / 3.0))
end
function tmp = code(x, y, z)
	tmp = sqrt(((((x * x) + (y * y)) + (z * z)) / 3.0));
end
code[x_, y_, z_] := N[Sqrt[N[(N[(N[(N[(x * x), $MachinePrecision] + N[(y * y), $MachinePrecision]), $MachinePrecision] + N[(z * z), $MachinePrecision]), $MachinePrecision] / 3.0), $MachinePrecision]], $MachinePrecision]
\begin{array}{l}

\\
\sqrt{\frac{\left(x \cdot x + y \cdot y\right) + z \cdot z}{3}}
\end{array}

Alternative 1: 99.6% accurate, 0.1× speedup?

\[\begin{array}{l} z_m = \left|z\right| \\ y_m = \left|y\right| \\ x_m = \left|x\right| \\ [x_m, y_m, z_m] = \mathsf{sort}([x_m, y_m, z_m])\\ \\ \left(\mathsf{hypot}\left(z\_m, y\_m\right) \cdot {0.3333333333333333}^{0.25}\right) \cdot {0.3333333333333333}^{0.25} \end{array} \]
z_m = (fabs.f64 z)
y_m = (fabs.f64 y)
x_m = (fabs.f64 x)
NOTE: x_m, y_m, and z_m should be sorted in increasing order before calling this function.
(FPCore (x_m y_m z_m)
 :precision binary64
 (*
  (* (hypot z_m y_m) (pow 0.3333333333333333 0.25))
  (pow 0.3333333333333333 0.25)))
z_m = fabs(z);
y_m = fabs(y);
x_m = fabs(x);
assert(x_m < y_m && y_m < z_m);
double code(double x_m, double y_m, double z_m) {
	return (hypot(z_m, y_m) * pow(0.3333333333333333, 0.25)) * pow(0.3333333333333333, 0.25);
}
z_m = Math.abs(z);
y_m = Math.abs(y);
x_m = Math.abs(x);
assert x_m < y_m && y_m < z_m;
public static double code(double x_m, double y_m, double z_m) {
	return (Math.hypot(z_m, y_m) * Math.pow(0.3333333333333333, 0.25)) * Math.pow(0.3333333333333333, 0.25);
}
z_m = math.fabs(z)
y_m = math.fabs(y)
x_m = math.fabs(x)
[x_m, y_m, z_m] = sort([x_m, y_m, z_m])
def code(x_m, y_m, z_m):
	return (math.hypot(z_m, y_m) * math.pow(0.3333333333333333, 0.25)) * math.pow(0.3333333333333333, 0.25)
z_m = abs(z)
y_m = abs(y)
x_m = abs(x)
x_m, y_m, z_m = sort([x_m, y_m, z_m])
function code(x_m, y_m, z_m)
	return Float64(Float64(hypot(z_m, y_m) * (0.3333333333333333 ^ 0.25)) * (0.3333333333333333 ^ 0.25))
end
z_m = abs(z);
y_m = abs(y);
x_m = abs(x);
x_m, y_m, z_m = num2cell(sort([x_m, y_m, z_m])){:}
function tmp = code(x_m, y_m, z_m)
	tmp = (hypot(z_m, y_m) * (0.3333333333333333 ^ 0.25)) * (0.3333333333333333 ^ 0.25);
end
z_m = N[Abs[z], $MachinePrecision]
y_m = N[Abs[y], $MachinePrecision]
x_m = N[Abs[x], $MachinePrecision]
NOTE: x_m, y_m, and z_m should be sorted in increasing order before calling this function.
code[x$95$m_, y$95$m_, z$95$m_] := N[(N[(N[Sqrt[z$95$m ^ 2 + y$95$m ^ 2], $MachinePrecision] * N[Power[0.3333333333333333, 0.25], $MachinePrecision]), $MachinePrecision] * N[Power[0.3333333333333333, 0.25], $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
z_m = \left|z\right|
\\
y_m = \left|y\right|
\\
x_m = \left|x\right|
\\
[x_m, y_m, z_m] = \mathsf{sort}([x_m, y_m, z_m])\\
\\
\left(\mathsf{hypot}\left(z\_m, y\_m\right) \cdot {0.3333333333333333}^{0.25}\right) \cdot {0.3333333333333333}^{0.25}
\end{array}
Derivation
  1. Initial program 46.2%

    \[\sqrt{\frac{\left(x \cdot x + y \cdot y\right) + z \cdot z}{3}} \]
  2. Add Preprocessing
  3. Taylor expanded in x around 0

    \[\leadsto \color{blue}{\sqrt{\frac{1}{3}} \cdot \sqrt{{y}^{2} + {z}^{2}}} \]
  4. Step-by-step derivation
    1. *-commutativeN/A

      \[\leadsto \color{blue}{\sqrt{{y}^{2} + {z}^{2}} \cdot \sqrt{\frac{1}{3}}} \]
    2. lower-*.f64N/A

      \[\leadsto \color{blue}{\sqrt{{y}^{2} + {z}^{2}} \cdot \sqrt{\frac{1}{3}}} \]
    3. +-commutativeN/A

      \[\leadsto \sqrt{\color{blue}{{z}^{2} + {y}^{2}}} \cdot \sqrt{\frac{1}{3}} \]
    4. unpow2N/A

      \[\leadsto \sqrt{\color{blue}{z \cdot z} + {y}^{2}} \cdot \sqrt{\frac{1}{3}} \]
    5. unpow2N/A

      \[\leadsto \sqrt{z \cdot z + \color{blue}{y \cdot y}} \cdot \sqrt{\frac{1}{3}} \]
    6. lower-hypot.f64N/A

      \[\leadsto \color{blue}{\mathsf{hypot}\left(z, y\right)} \cdot \sqrt{\frac{1}{3}} \]
    7. lower-sqrt.f6472.0

      \[\leadsto \mathsf{hypot}\left(z, y\right) \cdot \color{blue}{\sqrt{0.3333333333333333}} \]
  5. Applied rewrites72.0%

    \[\leadsto \color{blue}{\mathsf{hypot}\left(z, y\right) \cdot \sqrt{0.3333333333333333}} \]
  6. Step-by-step derivation
    1. Applied rewrites72.1%

      \[\leadsto {0.3333333333333333}^{0.25} \cdot \color{blue}{\left({0.3333333333333333}^{0.25} \cdot \mathsf{hypot}\left(z, y\right)\right)} \]
    2. Final simplification72.1%

      \[\leadsto \left(\mathsf{hypot}\left(z, y\right) \cdot {0.3333333333333333}^{0.25}\right) \cdot {0.3333333333333333}^{0.25} \]
    3. Add Preprocessing

    Alternative 2: 99.4% accurate, 0.4× speedup?

    \[\begin{array}{l} z_m = \left|z\right| \\ y_m = \left|y\right| \\ x_m = \left|x\right| \\ [x_m, y_m, z_m] = \mathsf{sort}([x_m, y_m, z_m])\\ \\ \sqrt{0.3333333333333333} \cdot \mathsf{hypot}\left(z\_m, y\_m\right) \end{array} \]
    z_m = (fabs.f64 z)
    y_m = (fabs.f64 y)
    x_m = (fabs.f64 x)
    NOTE: x_m, y_m, and z_m should be sorted in increasing order before calling this function.
    (FPCore (x_m y_m z_m)
     :precision binary64
     (* (sqrt 0.3333333333333333) (hypot z_m y_m)))
    z_m = fabs(z);
    y_m = fabs(y);
    x_m = fabs(x);
    assert(x_m < y_m && y_m < z_m);
    double code(double x_m, double y_m, double z_m) {
    	return sqrt(0.3333333333333333) * hypot(z_m, y_m);
    }
    
    z_m = Math.abs(z);
    y_m = Math.abs(y);
    x_m = Math.abs(x);
    assert x_m < y_m && y_m < z_m;
    public static double code(double x_m, double y_m, double z_m) {
    	return Math.sqrt(0.3333333333333333) * Math.hypot(z_m, y_m);
    }
    
    z_m = math.fabs(z)
    y_m = math.fabs(y)
    x_m = math.fabs(x)
    [x_m, y_m, z_m] = sort([x_m, y_m, z_m])
    def code(x_m, y_m, z_m):
    	return math.sqrt(0.3333333333333333) * math.hypot(z_m, y_m)
    
    z_m = abs(z)
    y_m = abs(y)
    x_m = abs(x)
    x_m, y_m, z_m = sort([x_m, y_m, z_m])
    function code(x_m, y_m, z_m)
    	return Float64(sqrt(0.3333333333333333) * hypot(z_m, y_m))
    end
    
    z_m = abs(z);
    y_m = abs(y);
    x_m = abs(x);
    x_m, y_m, z_m = num2cell(sort([x_m, y_m, z_m])){:}
    function tmp = code(x_m, y_m, z_m)
    	tmp = sqrt(0.3333333333333333) * hypot(z_m, y_m);
    end
    
    z_m = N[Abs[z], $MachinePrecision]
    y_m = N[Abs[y], $MachinePrecision]
    x_m = N[Abs[x], $MachinePrecision]
    NOTE: x_m, y_m, and z_m should be sorted in increasing order before calling this function.
    code[x$95$m_, y$95$m_, z$95$m_] := N[(N[Sqrt[0.3333333333333333], $MachinePrecision] * N[Sqrt[z$95$m ^ 2 + y$95$m ^ 2], $MachinePrecision]), $MachinePrecision]
    
    \begin{array}{l}
    z_m = \left|z\right|
    \\
    y_m = \left|y\right|
    \\
    x_m = \left|x\right|
    \\
    [x_m, y_m, z_m] = \mathsf{sort}([x_m, y_m, z_m])\\
    \\
    \sqrt{0.3333333333333333} \cdot \mathsf{hypot}\left(z\_m, y\_m\right)
    \end{array}
    
    Derivation
    1. Initial program 46.2%

      \[\sqrt{\frac{\left(x \cdot x + y \cdot y\right) + z \cdot z}{3}} \]
    2. Add Preprocessing
    3. Taylor expanded in x around 0

      \[\leadsto \color{blue}{\sqrt{\frac{1}{3}} \cdot \sqrt{{y}^{2} + {z}^{2}}} \]
    4. Step-by-step derivation
      1. *-commutativeN/A

        \[\leadsto \color{blue}{\sqrt{{y}^{2} + {z}^{2}} \cdot \sqrt{\frac{1}{3}}} \]
      2. lower-*.f64N/A

        \[\leadsto \color{blue}{\sqrt{{y}^{2} + {z}^{2}} \cdot \sqrt{\frac{1}{3}}} \]
      3. +-commutativeN/A

        \[\leadsto \sqrt{\color{blue}{{z}^{2} + {y}^{2}}} \cdot \sqrt{\frac{1}{3}} \]
      4. unpow2N/A

        \[\leadsto \sqrt{\color{blue}{z \cdot z} + {y}^{2}} \cdot \sqrt{\frac{1}{3}} \]
      5. unpow2N/A

        \[\leadsto \sqrt{z \cdot z + \color{blue}{y \cdot y}} \cdot \sqrt{\frac{1}{3}} \]
      6. lower-hypot.f64N/A

        \[\leadsto \color{blue}{\mathsf{hypot}\left(z, y\right)} \cdot \sqrt{\frac{1}{3}} \]
      7. lower-sqrt.f6472.0

        \[\leadsto \mathsf{hypot}\left(z, y\right) \cdot \color{blue}{\sqrt{0.3333333333333333}} \]
    5. Applied rewrites72.0%

      \[\leadsto \color{blue}{\mathsf{hypot}\left(z, y\right) \cdot \sqrt{0.3333333333333333}} \]
    6. Final simplification72.0%

      \[\leadsto \sqrt{0.3333333333333333} \cdot \mathsf{hypot}\left(z, y\right) \]
    7. Add Preprocessing

    Alternative 3: 98.8% accurate, 0.8× speedup?

    \[\begin{array}{l} z_m = \left|z\right| \\ y_m = \left|y\right| \\ x_m = \left|x\right| \\ [x_m, y_m, z_m] = \mathsf{sort}([x_m, y_m, z_m])\\ \\ \mathsf{fma}\left(0.5 \cdot z\_m, \frac{y\_m}{z\_m} \cdot \frac{y\_m}{z\_m}, z\_m\right) \cdot \sqrt{0.3333333333333333} \end{array} \]
    z_m = (fabs.f64 z)
    y_m = (fabs.f64 y)
    x_m = (fabs.f64 x)
    NOTE: x_m, y_m, and z_m should be sorted in increasing order before calling this function.
    (FPCore (x_m y_m z_m)
     :precision binary64
     (*
      (fma (* 0.5 z_m) (* (/ y_m z_m) (/ y_m z_m)) z_m)
      (sqrt 0.3333333333333333)))
    z_m = fabs(z);
    y_m = fabs(y);
    x_m = fabs(x);
    assert(x_m < y_m && y_m < z_m);
    double code(double x_m, double y_m, double z_m) {
    	return fma((0.5 * z_m), ((y_m / z_m) * (y_m / z_m)), z_m) * sqrt(0.3333333333333333);
    }
    
    z_m = abs(z)
    y_m = abs(y)
    x_m = abs(x)
    x_m, y_m, z_m = sort([x_m, y_m, z_m])
    function code(x_m, y_m, z_m)
    	return Float64(fma(Float64(0.5 * z_m), Float64(Float64(y_m / z_m) * Float64(y_m / z_m)), z_m) * sqrt(0.3333333333333333))
    end
    
    z_m = N[Abs[z], $MachinePrecision]
    y_m = N[Abs[y], $MachinePrecision]
    x_m = N[Abs[x], $MachinePrecision]
    NOTE: x_m, y_m, and z_m should be sorted in increasing order before calling this function.
    code[x$95$m_, y$95$m_, z$95$m_] := N[(N[(N[(0.5 * z$95$m), $MachinePrecision] * N[(N[(y$95$m / z$95$m), $MachinePrecision] * N[(y$95$m / z$95$m), $MachinePrecision]), $MachinePrecision] + z$95$m), $MachinePrecision] * N[Sqrt[0.3333333333333333], $MachinePrecision]), $MachinePrecision]
    
    \begin{array}{l}
    z_m = \left|z\right|
    \\
    y_m = \left|y\right|
    \\
    x_m = \left|x\right|
    \\
    [x_m, y_m, z_m] = \mathsf{sort}([x_m, y_m, z_m])\\
    \\
    \mathsf{fma}\left(0.5 \cdot z\_m, \frac{y\_m}{z\_m} \cdot \frac{y\_m}{z\_m}, z\_m\right) \cdot \sqrt{0.3333333333333333}
    \end{array}
    
    Derivation
    1. Initial program 46.2%

      \[\sqrt{\frac{\left(x \cdot x + y \cdot y\right) + z \cdot z}{3}} \]
    2. Add Preprocessing
    3. Taylor expanded in x around 0

      \[\leadsto \color{blue}{\sqrt{\frac{1}{3}} \cdot \sqrt{{y}^{2} + {z}^{2}}} \]
    4. Step-by-step derivation
      1. *-commutativeN/A

        \[\leadsto \color{blue}{\sqrt{{y}^{2} + {z}^{2}} \cdot \sqrt{\frac{1}{3}}} \]
      2. lower-*.f64N/A

        \[\leadsto \color{blue}{\sqrt{{y}^{2} + {z}^{2}} \cdot \sqrt{\frac{1}{3}}} \]
      3. +-commutativeN/A

        \[\leadsto \sqrt{\color{blue}{{z}^{2} + {y}^{2}}} \cdot \sqrt{\frac{1}{3}} \]
      4. unpow2N/A

        \[\leadsto \sqrt{\color{blue}{z \cdot z} + {y}^{2}} \cdot \sqrt{\frac{1}{3}} \]
      5. unpow2N/A

        \[\leadsto \sqrt{z \cdot z + \color{blue}{y \cdot y}} \cdot \sqrt{\frac{1}{3}} \]
      6. lower-hypot.f64N/A

        \[\leadsto \color{blue}{\mathsf{hypot}\left(z, y\right)} \cdot \sqrt{\frac{1}{3}} \]
      7. lower-sqrt.f6472.0

        \[\leadsto \mathsf{hypot}\left(z, y\right) \cdot \color{blue}{\sqrt{0.3333333333333333}} \]
    5. Applied rewrites72.0%

      \[\leadsto \color{blue}{\mathsf{hypot}\left(z, y\right) \cdot \sqrt{0.3333333333333333}} \]
    6. Step-by-step derivation
      1. Applied rewrites35.7%

        \[\leadsto \sqrt{\mathsf{fma}\left(z, z, y \cdot y\right)} \cdot \sqrt{\color{blue}{0.3333333333333333}} \]
      2. Taylor expanded in z around inf

        \[\leadsto \left(z \cdot \left(1 + \frac{1}{2} \cdot \frac{{y}^{2}}{{z}^{2}}\right)\right) \cdot \sqrt{\color{blue}{\frac{1}{3}}} \]
      3. Step-by-step derivation
        1. Applied rewrites20.5%

          \[\leadsto \mathsf{fma}\left(z \cdot 0.5, \frac{y}{z} \cdot \frac{y}{z}, z\right) \cdot \sqrt{\color{blue}{0.3333333333333333}} \]
        2. Final simplification20.5%

          \[\leadsto \mathsf{fma}\left(0.5 \cdot z, \frac{y}{z} \cdot \frac{y}{z}, z\right) \cdot \sqrt{0.3333333333333333} \]
        3. Add Preprocessing

        Alternative 4: 98.0% accurate, 2.7× speedup?

        \[\begin{array}{l} z_m = \left|z\right| \\ y_m = \left|y\right| \\ x_m = \left|x\right| \\ [x_m, y_m, z_m] = \mathsf{sort}([x_m, y_m, z_m])\\ \\ \sqrt{0.3333333333333333} \cdot z\_m \end{array} \]
        z_m = (fabs.f64 z)
        y_m = (fabs.f64 y)
        x_m = (fabs.f64 x)
        NOTE: x_m, y_m, and z_m should be sorted in increasing order before calling this function.
        (FPCore (x_m y_m z_m) :precision binary64 (* (sqrt 0.3333333333333333) z_m))
        z_m = fabs(z);
        y_m = fabs(y);
        x_m = fabs(x);
        assert(x_m < y_m && y_m < z_m);
        double code(double x_m, double y_m, double z_m) {
        	return sqrt(0.3333333333333333) * z_m;
        }
        
        z_m = abs(z)
        y_m = abs(y)
        x_m = abs(x)
        NOTE: x_m, y_m, and z_m should be sorted in increasing order before calling this function.
        real(8) function code(x_m, y_m, z_m)
            real(8), intent (in) :: x_m
            real(8), intent (in) :: y_m
            real(8), intent (in) :: z_m
            code = sqrt(0.3333333333333333d0) * z_m
        end function
        
        z_m = Math.abs(z);
        y_m = Math.abs(y);
        x_m = Math.abs(x);
        assert x_m < y_m && y_m < z_m;
        public static double code(double x_m, double y_m, double z_m) {
        	return Math.sqrt(0.3333333333333333) * z_m;
        }
        
        z_m = math.fabs(z)
        y_m = math.fabs(y)
        x_m = math.fabs(x)
        [x_m, y_m, z_m] = sort([x_m, y_m, z_m])
        def code(x_m, y_m, z_m):
        	return math.sqrt(0.3333333333333333) * z_m
        
        z_m = abs(z)
        y_m = abs(y)
        x_m = abs(x)
        x_m, y_m, z_m = sort([x_m, y_m, z_m])
        function code(x_m, y_m, z_m)
        	return Float64(sqrt(0.3333333333333333) * z_m)
        end
        
        z_m = abs(z);
        y_m = abs(y);
        x_m = abs(x);
        x_m, y_m, z_m = num2cell(sort([x_m, y_m, z_m])){:}
        function tmp = code(x_m, y_m, z_m)
        	tmp = sqrt(0.3333333333333333) * z_m;
        end
        
        z_m = N[Abs[z], $MachinePrecision]
        y_m = N[Abs[y], $MachinePrecision]
        x_m = N[Abs[x], $MachinePrecision]
        NOTE: x_m, y_m, and z_m should be sorted in increasing order before calling this function.
        code[x$95$m_, y$95$m_, z$95$m_] := N[(N[Sqrt[0.3333333333333333], $MachinePrecision] * z$95$m), $MachinePrecision]
        
        \begin{array}{l}
        z_m = \left|z\right|
        \\
        y_m = \left|y\right|
        \\
        x_m = \left|x\right|
        \\
        [x_m, y_m, z_m] = \mathsf{sort}([x_m, y_m, z_m])\\
        \\
        \sqrt{0.3333333333333333} \cdot z\_m
        \end{array}
        
        Derivation
        1. Initial program 46.2%

          \[\sqrt{\frac{\left(x \cdot x + y \cdot y\right) + z \cdot z}{3}} \]
        2. Add Preprocessing
        3. Taylor expanded in z around inf

          \[\leadsto \color{blue}{z \cdot \sqrt{\frac{1}{3}}} \]
        4. Step-by-step derivation
          1. *-commutativeN/A

            \[\leadsto \color{blue}{\sqrt{\frac{1}{3}} \cdot z} \]
          2. lower-*.f64N/A

            \[\leadsto \color{blue}{\sqrt{\frac{1}{3}} \cdot z} \]
          3. lower-sqrt.f6419.9

            \[\leadsto \color{blue}{\sqrt{0.3333333333333333}} \cdot z \]
        5. Applied rewrites19.9%

          \[\leadsto \color{blue}{\sqrt{0.3333333333333333} \cdot z} \]
        6. Add Preprocessing

        Developer Target 1: 97.4% accurate, 0.7× speedup?

        \[\begin{array}{l} \\ \begin{array}{l} \mathbf{if}\;z < -6.396479394109776 \cdot 10^{+136}:\\ \;\;\;\;\frac{-z}{\sqrt{3}}\\ \mathbf{elif}\;z < 7.320293694404182 \cdot 10^{+117}:\\ \;\;\;\;\frac{\sqrt{\left(z \cdot z + x \cdot x\right) + y \cdot y}}{\sqrt{3}}\\ \mathbf{else}:\\ \;\;\;\;\sqrt{0.3333333333333333} \cdot z\\ \end{array} \end{array} \]
        (FPCore (x y z)
         :precision binary64
         (if (< z -6.396479394109776e+136)
           (/ (- z) (sqrt 3.0))
           (if (< z 7.320293694404182e+117)
             (/ (sqrt (+ (+ (* z z) (* x x)) (* y y))) (sqrt 3.0))
             (* (sqrt 0.3333333333333333) z))))
        double code(double x, double y, double z) {
        	double tmp;
        	if (z < -6.396479394109776e+136) {
        		tmp = -z / sqrt(3.0);
        	} else if (z < 7.320293694404182e+117) {
        		tmp = sqrt((((z * z) + (x * x)) + (y * y))) / sqrt(3.0);
        	} else {
        		tmp = sqrt(0.3333333333333333) * z;
        	}
        	return tmp;
        }
        
        real(8) function code(x, y, z)
            real(8), intent (in) :: x
            real(8), intent (in) :: y
            real(8), intent (in) :: z
            real(8) :: tmp
            if (z < (-6.396479394109776d+136)) then
                tmp = -z / sqrt(3.0d0)
            else if (z < 7.320293694404182d+117) then
                tmp = sqrt((((z * z) + (x * x)) + (y * y))) / sqrt(3.0d0)
            else
                tmp = sqrt(0.3333333333333333d0) * z
            end if
            code = tmp
        end function
        
        public static double code(double x, double y, double z) {
        	double tmp;
        	if (z < -6.396479394109776e+136) {
        		tmp = -z / Math.sqrt(3.0);
        	} else if (z < 7.320293694404182e+117) {
        		tmp = Math.sqrt((((z * z) + (x * x)) + (y * y))) / Math.sqrt(3.0);
        	} else {
        		tmp = Math.sqrt(0.3333333333333333) * z;
        	}
        	return tmp;
        }
        
        def code(x, y, z):
        	tmp = 0
        	if z < -6.396479394109776e+136:
        		tmp = -z / math.sqrt(3.0)
        	elif z < 7.320293694404182e+117:
        		tmp = math.sqrt((((z * z) + (x * x)) + (y * y))) / math.sqrt(3.0)
        	else:
        		tmp = math.sqrt(0.3333333333333333) * z
        	return tmp
        
        function code(x, y, z)
        	tmp = 0.0
        	if (z < -6.396479394109776e+136)
        		tmp = Float64(Float64(-z) / sqrt(3.0));
        	elseif (z < 7.320293694404182e+117)
        		tmp = Float64(sqrt(Float64(Float64(Float64(z * z) + Float64(x * x)) + Float64(y * y))) / sqrt(3.0));
        	else
        		tmp = Float64(sqrt(0.3333333333333333) * z);
        	end
        	return tmp
        end
        
        function tmp_2 = code(x, y, z)
        	tmp = 0.0;
        	if (z < -6.396479394109776e+136)
        		tmp = -z / sqrt(3.0);
        	elseif (z < 7.320293694404182e+117)
        		tmp = sqrt((((z * z) + (x * x)) + (y * y))) / sqrt(3.0);
        	else
        		tmp = sqrt(0.3333333333333333) * z;
        	end
        	tmp_2 = tmp;
        end
        
        code[x_, y_, z_] := If[Less[z, -6.396479394109776e+136], N[((-z) / N[Sqrt[3.0], $MachinePrecision]), $MachinePrecision], If[Less[z, 7.320293694404182e+117], N[(N[Sqrt[N[(N[(N[(z * z), $MachinePrecision] + N[(x * x), $MachinePrecision]), $MachinePrecision] + N[(y * y), $MachinePrecision]), $MachinePrecision]], $MachinePrecision] / N[Sqrt[3.0], $MachinePrecision]), $MachinePrecision], N[(N[Sqrt[0.3333333333333333], $MachinePrecision] * z), $MachinePrecision]]]
        
        \begin{array}{l}
        
        \\
        \begin{array}{l}
        \mathbf{if}\;z < -6.396479394109776 \cdot 10^{+136}:\\
        \;\;\;\;\frac{-z}{\sqrt{3}}\\
        
        \mathbf{elif}\;z < 7.320293694404182 \cdot 10^{+117}:\\
        \;\;\;\;\frac{\sqrt{\left(z \cdot z + x \cdot x\right) + y \cdot y}}{\sqrt{3}}\\
        
        \mathbf{else}:\\
        \;\;\;\;\sqrt{0.3333333333333333} \cdot z\\
        
        
        \end{array}
        \end{array}
        

        Reproduce

        ?
        herbie shell --seed 2024244 
        (FPCore (x y z)
          :name "Data.Array.Repa.Algorithms.Pixel:doubleRmsOfRGB8 from repa-algorithms-3.4.0.1"
          :precision binary64
        
          :alt
          (! :herbie-platform default (if (< z -63964793941097760000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000) (/ (- z) (sqrt 3)) (if (< z 7320293694404182000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000) (/ (sqrt (+ (+ (* z z) (* x x)) (* y y))) (sqrt 3)) (* (sqrt 3333333333333333/10000000000000000) z))))
        
          (sqrt (/ (+ (+ (* x x) (* y y)) (* z z)) 3.0)))