math.square on complex, real part

Percentage Accurate: 93.7% → 100.0%
Time: 1.1s
Alternatives: 2
Speedup: 1.2×

Specification

?
\[re \cdot re - im \cdot im \]
(FPCore re_sqr (re im)
  :precision binary64
  (- (* re re) (* im im)))
double re_sqr(double re, double im) {
	return (re * re) - (im * im);
}
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 re_sqr(re, im)
use fmin_fmax_functions
    real(8), intent (in) :: re
    real(8), intent (in) :: im
    re_sqr = (re * re) - (im * im)
end function
public static double re_sqr(double re, double im) {
	return (re * re) - (im * im);
}
def re_sqr(re, im):
	return (re * re) - (im * im)
function re_sqr(re, im)
	return Float64(Float64(re * re) - Float64(im * im))
end
function tmp = re_sqr(re, im)
	tmp = (re * re) - (im * im);
end
re$95$sqr[re_, im_] := N[(N[(re * re), $MachinePrecision] - N[(im * im), $MachinePrecision]), $MachinePrecision]
re \cdot re - im \cdot im

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 2 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: 93.7% accurate, 1.0× speedup?

\[re \cdot re - im \cdot im \]
(FPCore re_sqr (re im)
  :precision binary64
  (- (* re re) (* im im)))
double re_sqr(double re, double im) {
	return (re * re) - (im * im);
}
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 re_sqr(re, im)
use fmin_fmax_functions
    real(8), intent (in) :: re
    real(8), intent (in) :: im
    re_sqr = (re * re) - (im * im)
end function
public static double re_sqr(double re, double im) {
	return (re * re) - (im * im);
}
def re_sqr(re, im):
	return (re * re) - (im * im)
function re_sqr(re, im)
	return Float64(Float64(re * re) - Float64(im * im))
end
function tmp = re_sqr(re, im)
	tmp = (re * re) - (im * im);
end
re$95$sqr[re_, im_] := N[(N[(re * re), $MachinePrecision] - N[(im * im), $MachinePrecision]), $MachinePrecision]
re \cdot re - im \cdot im

Alternative 1: 100.0% accurate, 1.2× speedup?

\[\left(re - im\right) \cdot \left(im + re\right) \]
(FPCore re_sqr (re im)
  :precision binary64
  (* (- re im) (+ im re)))
double re_sqr(double re, double im) {
	return (re - im) * (im + re);
}
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 re_sqr(re, im)
use fmin_fmax_functions
    real(8), intent (in) :: re
    real(8), intent (in) :: im
    re_sqr = (re - im) * (im + re)
end function
public static double re_sqr(double re, double im) {
	return (re - im) * (im + re);
}
def re_sqr(re, im):
	return (re - im) * (im + re)
function re_sqr(re, im)
	return Float64(Float64(re - im) * Float64(im + re))
end
function tmp = re_sqr(re, im)
	tmp = (re - im) * (im + re);
end
re$95$sqr[re_, im_] := N[(N[(re - im), $MachinePrecision] * N[(im + re), $MachinePrecision]), $MachinePrecision]
\left(re - im\right) \cdot \left(im + re\right)
Derivation
  1. Initial program 93.7%

    \[re \cdot re - im \cdot im \]
  2. Step-by-step derivation
    1. lift--.f64N/A

      \[\leadsto \color{blue}{re \cdot re - im \cdot im} \]
    2. lift-*.f64N/A

      \[\leadsto \color{blue}{re \cdot re} - im \cdot im \]
    3. lift-*.f64N/A

      \[\leadsto re \cdot re - \color{blue}{im \cdot im} \]
    4. difference-of-squaresN/A

      \[\leadsto \color{blue}{\left(re + im\right) \cdot \left(re - im\right)} \]
    5. *-commutativeN/A

      \[\leadsto \color{blue}{\left(re - im\right) \cdot \left(re + im\right)} \]
    6. lower-*.f64N/A

      \[\leadsto \color{blue}{\left(re - im\right) \cdot \left(re + im\right)} \]
    7. lower--.f64N/A

      \[\leadsto \color{blue}{\left(re - im\right)} \cdot \left(re + im\right) \]
    8. +-commutativeN/A

      \[\leadsto \left(re - im\right) \cdot \color{blue}{\left(im + re\right)} \]
    9. lower-+.f64100.0%

      \[\leadsto \left(re - im\right) \cdot \color{blue}{\left(im + re\right)} \]
  3. Applied rewrites100.0%

    \[\leadsto \color{blue}{\left(re - im\right) \cdot \left(im + re\right)} \]
  4. Add Preprocessing

Alternative 2: 60.6% accurate, 0.9× speedup?

\[\left(\left|re\right| - \left|im\right|\right) \cdot \left|im\right| \]
(FPCore re_sqr (re im)
  :precision binary64
  (* (- (fabs re) (fabs im)) (fabs im)))
double re_sqr(double re, double im) {
	return (fabs(re) - fabs(im)) * fabs(im);
}
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 re_sqr(re, im)
use fmin_fmax_functions
    real(8), intent (in) :: re
    real(8), intent (in) :: im
    re_sqr = (abs(re) - abs(im)) * abs(im)
end function
public static double re_sqr(double re, double im) {
	return (Math.abs(re) - Math.abs(im)) * Math.abs(im);
}
def re_sqr(re, im):
	return (math.fabs(re) - math.fabs(im)) * math.fabs(im)
function re_sqr(re, im)
	return Float64(Float64(abs(re) - abs(im)) * abs(im))
end
function tmp = re_sqr(re, im)
	tmp = (abs(re) - abs(im)) * abs(im);
end
re$95$sqr[re_, im_] := N[(N[(N[Abs[re], $MachinePrecision] - N[Abs[im], $MachinePrecision]), $MachinePrecision] * N[Abs[im], $MachinePrecision]), $MachinePrecision]
\left(\left|re\right| - \left|im\right|\right) \cdot \left|im\right|
Derivation
  1. Initial program 93.7%

    \[re \cdot re - im \cdot im \]
  2. Step-by-step derivation
    1. lift--.f64N/A

      \[\leadsto \color{blue}{re \cdot re - im \cdot im} \]
    2. lift-*.f64N/A

      \[\leadsto \color{blue}{re \cdot re} - im \cdot im \]
    3. lift-*.f64N/A

      \[\leadsto re \cdot re - \color{blue}{im \cdot im} \]
    4. difference-of-squaresN/A

      \[\leadsto \color{blue}{\left(re + im\right) \cdot \left(re - im\right)} \]
    5. *-commutativeN/A

      \[\leadsto \color{blue}{\left(re - im\right) \cdot \left(re + im\right)} \]
    6. lower-*.f64N/A

      \[\leadsto \color{blue}{\left(re - im\right) \cdot \left(re + im\right)} \]
    7. lower--.f64N/A

      \[\leadsto \color{blue}{\left(re - im\right)} \cdot \left(re + im\right) \]
    8. +-commutativeN/A

      \[\leadsto \left(re - im\right) \cdot \color{blue}{\left(im + re\right)} \]
    9. lower-+.f64100.0%

      \[\leadsto \left(re - im\right) \cdot \color{blue}{\left(im + re\right)} \]
  3. Applied rewrites100.0%

    \[\leadsto \color{blue}{\left(re - im\right) \cdot \left(im + re\right)} \]
  4. Taylor expanded in re around 0

    \[\leadsto \left(re - im\right) \cdot \color{blue}{im} \]
  5. Step-by-step derivation
    1. Applied rewrites56.9%

      \[\leadsto \left(re - im\right) \cdot \color{blue}{im} \]
    2. Add Preprocessing

    Reproduce

    ?
    herbie shell --seed 2025285 -o generate:evaluate
    (FPCore re_sqr (re im)
      :name "math.square on complex, real part"
      :precision binary64
      (- (* re re) (* im im)))