Average Error: 0.1 → 0
Time: 6.5s
Precision: binary64
Cost: 6720
\[x + \frac{x - y}{2} \]
↓
\[\mathsf{fma}\left(x, 1.5, y \cdot -0.5\right) \]
(FPCore (x y) :precision binary64 (+ x (/ (- x y) 2.0)))
↓
(FPCore (x y) :precision binary64 (fma x 1.5 (* y -0.5)))
double code(double x, double y) {
	return x + ((x - y) / 2.0);
}
↓
double code(double x, double y) {
	return fma(x, 1.5, (y * -0.5));
}

function code(x, y)
	return Float64(x + Float64(Float64(x - y) / 2.0))
end
↓
function code(x, y)
	return fma(x, 1.5, Float64(y * -0.5))
end

code[x_, y_] := N[(x + N[(N[(x - y), $MachinePrecision] / 2.0), $MachinePrecision]), $MachinePrecision]
↓
code[x_, y_] := N[(x * 1.5 + N[(y * -0.5), $MachinePrecision]), $MachinePrecision]

x + \frac{x - y}{2}
↓
\mathsf{fma}\left(x, 1.5, y \cdot -0.5\right)

Error

Target

Original0.1
Target0.1
Herbie0
\[1.5 \cdot x - 0.5 \cdot y \]

Derivation

  1. Initial program 0.1

    \[x + \frac{x - y}{2} \]

  2. Applied egg-rr31.8

    \[\leadsto \color{blue}{\frac{1}{\frac{x - \left(x - y\right) \cdot 0.5}{x \cdot x - {\left(x - y\right)}^{2} \cdot 0.25}}} \]

  3. Taylor expanded in x around 0 0.1

    \[\leadsto \color{blue}{-0.5 \cdot y + 1.5 \cdot x} \]

  4. Simplified0

    \[\leadsto \color{blue}{\mathsf{fma}\left(x, 1.5, y \cdot -0.5\right)} \]

  5. Final simplification0

    \[\leadsto \mathsf{fma}\left(x, 1.5, y \cdot -0.5\right) \]

Alternatives

Alternative 1
Error16.6
Cost456
\[\begin{array}{l} \mathbf{if}\;y \leq -9.8307112374039 \cdot 10^{+105}:\\ \;\;\;\;y \cdot -0.5\\ \mathbf{elif}\;y \leq 1.706400682227231 \cdot 10^{-16}:\\ \;\;\;\;x \cdot 1.5\\ \mathbf{else}:\\ \;\;\;\;y \cdot -0.5\\ \end{array} \]
Alternative 2
Error0.1
Cost448
\[y \cdot -0.5 + x \cdot 1.5 \]
Alternative 3
Error32.1
Cost192
\[y \cdot -0.5 \]

Error

Reproduce

herbie shell --seed 2022228 
(FPCore (x y)
  :name "Graphics.Rendering.Chart.Axis.Types:hBufferRect from Chart-1.5.3"
  :precision binary64

  :herbie-target
  (- (* 1.5 x) (* 0.5 y))

  (+ x (/ (- x y) 2.0)))