Migdal et al, Equation (64)

Percentage Accurate: 99.5% → 99.6%
Time: 8.6s
Alternatives: 9
Speedup: 1.9×

Specification

?
\[\begin{array}{l} \\ \begin{array}{l} t_1 := \frac{\cos th}{\sqrt{2}}\\ t\_1 \cdot \left(a1 \cdot a1\right) + t\_1 \cdot \left(a2 \cdot a2\right) \end{array} \end{array} \]
(FPCore (a1 a2 th)
 :precision binary64
 (let* ((t_1 (/ (cos th) (sqrt 2.0))))
   (+ (* t_1 (* a1 a1)) (* t_1 (* a2 a2)))))
double code(double a1, double a2, double th) {
	double t_1 = cos(th) / sqrt(2.0);
	return (t_1 * (a1 * a1)) + (t_1 * (a2 * a2));
}
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(a1, a2, th)
use fmin_fmax_functions
    real(8), intent (in) :: a1
    real(8), intent (in) :: a2
    real(8), intent (in) :: th
    real(8) :: t_1
    t_1 = cos(th) / sqrt(2.0d0)
    code = (t_1 * (a1 * a1)) + (t_1 * (a2 * a2))
end function
public static double code(double a1, double a2, double th) {
	double t_1 = Math.cos(th) / Math.sqrt(2.0);
	return (t_1 * (a1 * a1)) + (t_1 * (a2 * a2));
}
def code(a1, a2, th):
	t_1 = math.cos(th) / math.sqrt(2.0)
	return (t_1 * (a1 * a1)) + (t_1 * (a2 * a2))
function code(a1, a2, th)
	t_1 = Float64(cos(th) / sqrt(2.0))
	return Float64(Float64(t_1 * Float64(a1 * a1)) + Float64(t_1 * Float64(a2 * a2)))
end
function tmp = code(a1, a2, th)
	t_1 = cos(th) / sqrt(2.0);
	tmp = (t_1 * (a1 * a1)) + (t_1 * (a2 * a2));
end
code[a1_, a2_, th_] := Block[{t$95$1 = N[(N[Cos[th], $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]}, N[(N[(t$95$1 * N[(a1 * a1), $MachinePrecision]), $MachinePrecision] + N[(t$95$1 * N[(a2 * a2), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}

\\
\begin{array}{l}
t_1 := \frac{\cos th}{\sqrt{2}}\\
t\_1 \cdot \left(a1 \cdot a1\right) + t\_1 \cdot \left(a2 \cdot a2\right)
\end{array}
\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 9 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: 99.5% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \begin{array}{l} t_1 := \frac{\cos th}{\sqrt{2}}\\ t\_1 \cdot \left(a1 \cdot a1\right) + t\_1 \cdot \left(a2 \cdot a2\right) \end{array} \end{array} \]
(FPCore (a1 a2 th)
 :precision binary64
 (let* ((t_1 (/ (cos th) (sqrt 2.0))))
   (+ (* t_1 (* a1 a1)) (* t_1 (* a2 a2)))))
double code(double a1, double a2, double th) {
	double t_1 = cos(th) / sqrt(2.0);
	return (t_1 * (a1 * a1)) + (t_1 * (a2 * a2));
}
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(a1, a2, th)
use fmin_fmax_functions
    real(8), intent (in) :: a1
    real(8), intent (in) :: a2
    real(8), intent (in) :: th
    real(8) :: t_1
    t_1 = cos(th) / sqrt(2.0d0)
    code = (t_1 * (a1 * a1)) + (t_1 * (a2 * a2))
end function
public static double code(double a1, double a2, double th) {
	double t_1 = Math.cos(th) / Math.sqrt(2.0);
	return (t_1 * (a1 * a1)) + (t_1 * (a2 * a2));
}
def code(a1, a2, th):
	t_1 = math.cos(th) / math.sqrt(2.0)
	return (t_1 * (a1 * a1)) + (t_1 * (a2 * a2))
function code(a1, a2, th)
	t_1 = Float64(cos(th) / sqrt(2.0))
	return Float64(Float64(t_1 * Float64(a1 * a1)) + Float64(t_1 * Float64(a2 * a2)))
end
function tmp = code(a1, a2, th)
	t_1 = cos(th) / sqrt(2.0);
	tmp = (t_1 * (a1 * a1)) + (t_1 * (a2 * a2));
end
code[a1_, a2_, th_] := Block[{t$95$1 = N[(N[Cos[th], $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]}, N[(N[(t$95$1 * N[(a1 * a1), $MachinePrecision]), $MachinePrecision] + N[(t$95$1 * N[(a2 * a2), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]]
\begin{array}{l}

\\
\begin{array}{l}
t_1 := \frac{\cos th}{\sqrt{2}}\\
t\_1 \cdot \left(a1 \cdot a1\right) + t\_1 \cdot \left(a2 \cdot a2\right)
\end{array}
\end{array}

Alternative 1: 99.6% accurate, 1.1× speedup?

\[\begin{array}{l} \\ \frac{\mathsf{fma}\left(\cos th \cdot a2, a2, \left(\cos th \cdot a1\right) \cdot a1\right)}{\sqrt{2}} \end{array} \]
(FPCore (a1 a2 th)
 :precision binary64
 (/ (fma (* (cos th) a2) a2 (* (* (cos th) a1) a1)) (sqrt 2.0)))
double code(double a1, double a2, double th) {
	return fma((cos(th) * a2), a2, ((cos(th) * a1) * a1)) / sqrt(2.0);
}
function code(a1, a2, th)
	return Float64(fma(Float64(cos(th) * a2), a2, Float64(Float64(cos(th) * a1) * a1)) / sqrt(2.0))
end
code[a1_, a2_, th_] := N[(N[(N[(N[Cos[th], $MachinePrecision] * a2), $MachinePrecision] * a2 + N[(N[(N[Cos[th], $MachinePrecision] * a1), $MachinePrecision] * a1), $MachinePrecision]), $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{\mathsf{fma}\left(\cos th \cdot a2, a2, \left(\cos th \cdot a1\right) \cdot a1\right)}{\sqrt{2}}
\end{array}
Derivation
  1. Initial program 99.6%

    \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
  2. Add Preprocessing
  3. Applied rewrites99.7%

    \[\leadsto \color{blue}{\frac{\mathsf{fma}\left(\cos th \cdot a2, a2, \left(\cos th \cdot a1\right) \cdot a1\right)}{\sqrt{2}}} \]
  4. Add Preprocessing

Alternative 2: 99.6% accurate, 1.9× speedup?

\[\begin{array}{l} \\ \frac{\cos th \cdot \mathsf{fma}\left(a2, a2, a1 \cdot a1\right)}{\sqrt{2}} \end{array} \]
(FPCore (a1 a2 th)
 :precision binary64
 (/ (* (cos th) (fma a2 a2 (* a1 a1))) (sqrt 2.0)))
double code(double a1, double a2, double th) {
	return (cos(th) * fma(a2, a2, (a1 * a1))) / sqrt(2.0);
}
function code(a1, a2, th)
	return Float64(Float64(cos(th) * fma(a2, a2, Float64(a1 * a1))) / sqrt(2.0))
end
code[a1_, a2_, th_] := N[(N[(N[Cos[th], $MachinePrecision] * N[(a2 * a2 + N[(a1 * a1), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{\cos th \cdot \mathsf{fma}\left(a2, a2, a1 \cdot a1\right)}{\sqrt{2}}
\end{array}
Derivation
  1. Initial program 99.6%

    \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
  2. Add Preprocessing
  3. Applied rewrites99.6%

    \[\leadsto \color{blue}{\frac{\cos th \cdot \mathsf{fma}\left(a2, a2, a1 \cdot a1\right)}{\sqrt{2}}} \]
  4. Add Preprocessing

Alternative 3: 99.6% accurate, 1.9× speedup?

\[\begin{array}{l} \\ \frac{\mathsf{fma}\left(a2, a2, a1 \cdot a1\right)}{\sqrt{2}} \cdot \cos th \end{array} \]
(FPCore (a1 a2 th)
 :precision binary64
 (* (/ (fma a2 a2 (* a1 a1)) (sqrt 2.0)) (cos th)))
double code(double a1, double a2, double th) {
	return (fma(a2, a2, (a1 * a1)) / sqrt(2.0)) * cos(th);
}
function code(a1, a2, th)
	return Float64(Float64(fma(a2, a2, Float64(a1 * a1)) / sqrt(2.0)) * cos(th))
end
code[a1_, a2_, th_] := N[(N[(N[(a2 * a2 + N[(a1 * a1), $MachinePrecision]), $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision] * N[Cos[th], $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{\mathsf{fma}\left(a2, a2, a1 \cdot a1\right)}{\sqrt{2}} \cdot \cos th
\end{array}
Derivation
  1. Initial program 99.6%

    \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
  2. Add Preprocessing
  3. Applied rewrites99.7%

    \[\leadsto \color{blue}{\frac{\mathsf{fma}\left(\cos th \cdot a2, a2, \left(\cos th \cdot a1\right) \cdot a1\right)}{\sqrt{2}}} \]
  4. Applied rewrites99.6%

    \[\leadsto \color{blue}{\frac{\mathsf{fma}\left(a2, a2, a1 \cdot a1\right)}{\sqrt{2}} \cdot \cos th} \]
  5. Add Preprocessing

Alternative 4: 57.5% accurate, 2.0× speedup?

\[\begin{array}{l} \\ \frac{\left(\cos th \cdot a2\right) \cdot a2}{\sqrt{2}} \end{array} \]
(FPCore (a1 a2 th) :precision binary64 (/ (* (* (cos th) a2) a2) (sqrt 2.0)))
double code(double a1, double a2, double th) {
	return ((cos(th) * a2) * a2) / sqrt(2.0);
}
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(a1, a2, th)
use fmin_fmax_functions
    real(8), intent (in) :: a1
    real(8), intent (in) :: a2
    real(8), intent (in) :: th
    code = ((cos(th) * a2) * a2) / sqrt(2.0d0)
end function
public static double code(double a1, double a2, double th) {
	return ((Math.cos(th) * a2) * a2) / Math.sqrt(2.0);
}
def code(a1, a2, th):
	return ((math.cos(th) * a2) * a2) / math.sqrt(2.0)
function code(a1, a2, th)
	return Float64(Float64(Float64(cos(th) * a2) * a2) / sqrt(2.0))
end
function tmp = code(a1, a2, th)
	tmp = ((cos(th) * a2) * a2) / sqrt(2.0);
end
code[a1_, a2_, th_] := N[(N[(N[(N[Cos[th], $MachinePrecision] * a2), $MachinePrecision] * a2), $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{\left(\cos th \cdot a2\right) \cdot a2}{\sqrt{2}}
\end{array}
Derivation
  1. Initial program 99.6%

    \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
  2. Add Preprocessing
  3. Applied rewrites99.7%

    \[\leadsto \color{blue}{\frac{\mathsf{fma}\left(\cos th \cdot a2, a2, \left(\cos th \cdot a1\right) \cdot a1\right)}{\sqrt{2}}} \]
  4. Taylor expanded in th around 0

    \[\leadsto \frac{\color{blue}{{a1}^{2} + {a2}^{2}}}{\sqrt{2}} \]
  5. Step-by-step derivation
    1. Applied rewrites64.8%

      \[\leadsto \frac{\color{blue}{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)}}{\sqrt{2}} \]
    2. Taylor expanded in a1 around inf

      \[\leadsto \frac{{a1}^{\color{blue}{2}}}{\sqrt{2}} \]
    3. Step-by-step derivation
      1. Applied rewrites43.8%

        \[\leadsto \frac{a1 \cdot \color{blue}{a1}}{\sqrt{2}} \]
      2. Taylor expanded in a1 around 0

        \[\leadsto \frac{\color{blue}{{a2}^{2} \cdot \cos th}}{\sqrt{2}} \]
      3. Step-by-step derivation
        1. Applied rewrites50.4%

          \[\leadsto \frac{\color{blue}{\left(\cos th \cdot a2\right) \cdot a2}}{\sqrt{2}} \]
        2. Add Preprocessing

        Alternative 5: 57.5% accurate, 2.0× speedup?

        \[\begin{array}{l} \\ \left(a2 \cdot a2\right) \cdot \frac{\cos th}{\sqrt{2}} \end{array} \]
        (FPCore (a1 a2 th) :precision binary64 (* (* a2 a2) (/ (cos th) (sqrt 2.0))))
        double code(double a1, double a2, double th) {
        	return (a2 * a2) * (cos(th) / sqrt(2.0));
        }
        
        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(a1, a2, th)
        use fmin_fmax_functions
            real(8), intent (in) :: a1
            real(8), intent (in) :: a2
            real(8), intent (in) :: th
            code = (a2 * a2) * (cos(th) / sqrt(2.0d0))
        end function
        
        public static double code(double a1, double a2, double th) {
        	return (a2 * a2) * (Math.cos(th) / Math.sqrt(2.0));
        }
        
        def code(a1, a2, th):
        	return (a2 * a2) * (math.cos(th) / math.sqrt(2.0))
        
        function code(a1, a2, th)
        	return Float64(Float64(a2 * a2) * Float64(cos(th) / sqrt(2.0)))
        end
        
        function tmp = code(a1, a2, th)
        	tmp = (a2 * a2) * (cos(th) / sqrt(2.0));
        end
        
        code[a1_, a2_, th_] := N[(N[(a2 * a2), $MachinePrecision] * N[(N[Cos[th], $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
        
        \begin{array}{l}
        
        \\
        \left(a2 \cdot a2\right) \cdot \frac{\cos th}{\sqrt{2}}
        \end{array}
        
        Derivation
        1. Initial program 99.6%

          \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
        2. Add Preprocessing
        3. Applied rewrites99.6%

          \[\leadsto \color{blue}{\mathsf{fma}\left(a2, a2, a1 \cdot a1\right) \cdot \frac{\cos th}{\sqrt{2}}} \]
        4. Taylor expanded in a1 around 0

          \[\leadsto \color{blue}{{a2}^{2}} \cdot \frac{\cos th}{\sqrt{2}} \]
        5. Step-by-step derivation
          1. Applied rewrites50.4%

            \[\leadsto \color{blue}{\left(a2 \cdot a2\right)} \cdot \frac{\cos th}{\sqrt{2}} \]
          2. Add Preprocessing

          Alternative 6: 65.8% accurate, 8.1× speedup?

          \[\begin{array}{l} \\ \frac{\mathsf{fma}\left(a2, a2, a1 \cdot a1\right)}{\sqrt{2}} \end{array} \]
          (FPCore (a1 a2 th) :precision binary64 (/ (fma a2 a2 (* a1 a1)) (sqrt 2.0)))
          double code(double a1, double a2, double th) {
          	return fma(a2, a2, (a1 * a1)) / sqrt(2.0);
          }
          
          function code(a1, a2, th)
          	return Float64(fma(a2, a2, Float64(a1 * a1)) / sqrt(2.0))
          end
          
          code[a1_, a2_, th_] := N[(N[(a2 * a2 + N[(a1 * a1), $MachinePrecision]), $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]
          
          \begin{array}{l}
          
          \\
          \frac{\mathsf{fma}\left(a2, a2, a1 \cdot a1\right)}{\sqrt{2}}
          \end{array}
          
          Derivation
          1. Initial program 99.6%

            \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
          2. Add Preprocessing
          3. Applied rewrites99.7%

            \[\leadsto \color{blue}{\frac{\mathsf{fma}\left(\cos th \cdot a2, a2, \left(\cos th \cdot a1\right) \cdot a1\right)}{\sqrt{2}}} \]
          4. Taylor expanded in th around 0

            \[\leadsto \frac{\color{blue}{{a1}^{2} + {a2}^{2}}}{\sqrt{2}} \]
          5. Step-by-step derivation
            1. Applied rewrites64.8%

              \[\leadsto \frac{\color{blue}{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)}}{\sqrt{2}} \]
            2. Step-by-step derivation
              1. Applied rewrites64.8%

                \[\leadsto \frac{\mathsf{fma}\left(a2, \color{blue}{a2}, a1 \cdot a1\right)}{\sqrt{2}} \]
              2. Add Preprocessing

              Alternative 7: 65.8% accurate, 8.1× speedup?

              \[\begin{array}{l} \\ \frac{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)}{\sqrt{2}} \end{array} \]
              (FPCore (a1 a2 th) :precision binary64 (/ (fma a1 a1 (* a2 a2)) (sqrt 2.0)))
              double code(double a1, double a2, double th) {
              	return fma(a1, a1, (a2 * a2)) / sqrt(2.0);
              }
              
              function code(a1, a2, th)
              	return Float64(fma(a1, a1, Float64(a2 * a2)) / sqrt(2.0))
              end
              
              code[a1_, a2_, th_] := N[(N[(a1 * a1 + N[(a2 * a2), $MachinePrecision]), $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]
              
              \begin{array}{l}
              
              \\
              \frac{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)}{\sqrt{2}}
              \end{array}
              
              Derivation
              1. Initial program 99.6%

                \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
              2. Add Preprocessing
              3. Applied rewrites99.7%

                \[\leadsto \color{blue}{\frac{\mathsf{fma}\left(\cos th \cdot a2, a2, \left(\cos th \cdot a1\right) \cdot a1\right)}{\sqrt{2}}} \]
              4. Taylor expanded in th around 0

                \[\leadsto \frac{\color{blue}{{a1}^{2} + {a2}^{2}}}{\sqrt{2}} \]
              5. Step-by-step derivation
                1. Applied rewrites64.8%

                  \[\leadsto \frac{\color{blue}{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)}}{\sqrt{2}} \]
                2. Add Preprocessing

                Alternative 8: 40.1% accurate, 9.9× speedup?

                \[\begin{array}{l} \\ \frac{a2 \cdot a2}{\sqrt{2}} \end{array} \]
                (FPCore (a1 a2 th) :precision binary64 (/ (* a2 a2) (sqrt 2.0)))
                double code(double a1, double a2, double th) {
                	return (a2 * a2) / sqrt(2.0);
                }
                
                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(a1, a2, th)
                use fmin_fmax_functions
                    real(8), intent (in) :: a1
                    real(8), intent (in) :: a2
                    real(8), intent (in) :: th
                    code = (a2 * a2) / sqrt(2.0d0)
                end function
                
                public static double code(double a1, double a2, double th) {
                	return (a2 * a2) / Math.sqrt(2.0);
                }
                
                def code(a1, a2, th):
                	return (a2 * a2) / math.sqrt(2.0)
                
                function code(a1, a2, th)
                	return Float64(Float64(a2 * a2) / sqrt(2.0))
                end
                
                function tmp = code(a1, a2, th)
                	tmp = (a2 * a2) / sqrt(2.0);
                end
                
                code[a1_, a2_, th_] := N[(N[(a2 * a2), $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]
                
                \begin{array}{l}
                
                \\
                \frac{a2 \cdot a2}{\sqrt{2}}
                \end{array}
                
                Derivation
                1. Initial program 99.6%

                  \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
                2. Add Preprocessing
                3. Applied rewrites99.7%

                  \[\leadsto \color{blue}{\frac{\mathsf{fma}\left(\cos th \cdot a2, a2, \left(\cos th \cdot a1\right) \cdot a1\right)}{\sqrt{2}}} \]
                4. Taylor expanded in th around 0

                  \[\leadsto \frac{\color{blue}{{a1}^{2} + {a2}^{2}}}{\sqrt{2}} \]
                5. Step-by-step derivation
                  1. Applied rewrites64.8%

                    \[\leadsto \frac{\color{blue}{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)}}{\sqrt{2}} \]
                  2. Taylor expanded in a1 around 0

                    \[\leadsto \frac{{a2}^{\color{blue}{2}}}{\sqrt{2}} \]
                  3. Step-by-step derivation
                    1. Applied rewrites33.6%

                      \[\leadsto \frac{a2 \cdot \color{blue}{a2}}{\sqrt{2}} \]
                    2. Add Preprocessing

                    Alternative 9: 38.9% accurate, 9.9× speedup?

                    \[\begin{array}{l} \\ \frac{a1 \cdot a1}{\sqrt{2}} \end{array} \]
                    (FPCore (a1 a2 th) :precision binary64 (/ (* a1 a1) (sqrt 2.0)))
                    double code(double a1, double a2, double th) {
                    	return (a1 * a1) / sqrt(2.0);
                    }
                    
                    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(a1, a2, th)
                    use fmin_fmax_functions
                        real(8), intent (in) :: a1
                        real(8), intent (in) :: a2
                        real(8), intent (in) :: th
                        code = (a1 * a1) / sqrt(2.0d0)
                    end function
                    
                    public static double code(double a1, double a2, double th) {
                    	return (a1 * a1) / Math.sqrt(2.0);
                    }
                    
                    def code(a1, a2, th):
                    	return (a1 * a1) / math.sqrt(2.0)
                    
                    function code(a1, a2, th)
                    	return Float64(Float64(a1 * a1) / sqrt(2.0))
                    end
                    
                    function tmp = code(a1, a2, th)
                    	tmp = (a1 * a1) / sqrt(2.0);
                    end
                    
                    code[a1_, a2_, th_] := N[(N[(a1 * a1), $MachinePrecision] / N[Sqrt[2.0], $MachinePrecision]), $MachinePrecision]
                    
                    \begin{array}{l}
                    
                    \\
                    \frac{a1 \cdot a1}{\sqrt{2}}
                    \end{array}
                    
                    Derivation
                    1. Initial program 99.6%

                      \[\frac{\cos th}{\sqrt{2}} \cdot \left(a1 \cdot a1\right) + \frac{\cos th}{\sqrt{2}} \cdot \left(a2 \cdot a2\right) \]
                    2. Add Preprocessing
                    3. Applied rewrites99.7%

                      \[\leadsto \color{blue}{\frac{\mathsf{fma}\left(\cos th \cdot a2, a2, \left(\cos th \cdot a1\right) \cdot a1\right)}{\sqrt{2}}} \]
                    4. Taylor expanded in th around 0

                      \[\leadsto \frac{\color{blue}{{a1}^{2} + {a2}^{2}}}{\sqrt{2}} \]
                    5. Step-by-step derivation
                      1. Applied rewrites64.8%

                        \[\leadsto \frac{\color{blue}{\mathsf{fma}\left(a1, a1, a2 \cdot a2\right)}}{\sqrt{2}} \]
                      2. Taylor expanded in a1 around inf

                        \[\leadsto \frac{{a1}^{\color{blue}{2}}}{\sqrt{2}} \]
                      3. Step-by-step derivation
                        1. Applied rewrites43.8%

                          \[\leadsto \frac{a1 \cdot \color{blue}{a1}}{\sqrt{2}} \]
                        2. Add Preprocessing

                        Reproduce

                        ?
                        herbie shell --seed 2025021 
                        (FPCore (a1 a2 th)
                          :name "Migdal et al, Equation (64)"
                          :precision binary64
                          (+ (* (/ (cos th) (sqrt 2.0)) (* a1 a1)) (* (/ (cos th) (sqrt 2.0)) (* a2 a2))))