Jmat.Real.erfi, branch x less than or equal to 0.5

Average Error: 0.2 → 0.1

Time: 19.8s

Precision: binary64

Cost: 27136

\[x \leq 0.5\]

Math

\[\left|\frac{1}{\sqrt{\pi}} \cdot \left(\left(\left(2 \cdot \left|x\right| + \frac{2}{3} \cdot \left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right) + \frac{1}{5} \cdot \left(\left(\left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right) + \frac{1}{21} \cdot \left(\left(\left(\left(\left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right)\right| \]

↓

\[\left|\frac{\left(x \cdot x\right) \cdot \left(\left(x \cdot \left(\left(0.047619047619047616 \cdot x\right) \cdot x\right) + x \cdot 0.2\right) \cdot x + 0.6666666666666666\right) + 2}{\sqrt{\pi}} \cdot \left|x\right|\right| \]

FPCore

(FPCore (x)
 :precision binary64
 (fabs
  (*
   (/ 1.0 (sqrt PI))
   (+
    (+
     (+ (* 2.0 (fabs x)) (* (/ 2.0 3.0) (* (* (fabs x) (fabs x)) (fabs x))))
     (*
      (/ 1.0 5.0)
      (* (* (* (* (fabs x) (fabs x)) (fabs x)) (fabs x)) (fabs x))))
    (*
     (/ 1.0 21.0)
     (*
      (* (* (* (* (* (fabs x) (fabs x)) (fabs x)) (fabs x)) (fabs x)) (fabs x))
      (fabs x)))))))

↓

(FPCore (x)
 :precision binary64
 (fabs
  (*
   (/
    (+
     (*
      (* x x)
      (+
       (* (+ (* x (* (* 0.047619047619047616 x) x)) (* x 0.2)) x)
       0.6666666666666666))
     2.0)
    (sqrt PI))
   (fabs x))))

C

double code(double x) {
	return fabs(((1.0 / sqrt(((double) M_PI))) * ((((2.0 * fabs(x)) + ((2.0 / 3.0) * ((fabs(x) * fabs(x)) * fabs(x)))) + ((1.0 / 5.0) * ((((fabs(x) * fabs(x)) * fabs(x)) * fabs(x)) * fabs(x)))) + ((1.0 / 21.0) * ((((((fabs(x) * fabs(x)) * fabs(x)) * fabs(x)) * fabs(x)) * fabs(x)) * fabs(x))))));
}

↓

double code(double x) {
	return fabs((((((x * x) * ((((x * ((0.047619047619047616 * x) * x)) + (x * 0.2)) * x) + 0.6666666666666666)) + 2.0) / sqrt(((double) M_PI))) * fabs(x)));
}

Java

public static double code(double x) {
	return Math.abs(((1.0 / Math.sqrt(Math.PI)) * ((((2.0 * Math.abs(x)) + ((2.0 / 3.0) * ((Math.abs(x) * Math.abs(x)) * Math.abs(x)))) + ((1.0 / 5.0) * ((((Math.abs(x) * Math.abs(x)) * Math.abs(x)) * Math.abs(x)) * Math.abs(x)))) + ((1.0 / 21.0) * ((((((Math.abs(x) * Math.abs(x)) * Math.abs(x)) * Math.abs(x)) * Math.abs(x)) * Math.abs(x)) * Math.abs(x))))));
}

↓

public static double code(double x) {
	return Math.abs((((((x * x) * ((((x * ((0.047619047619047616 * x) * x)) + (x * 0.2)) * x) + 0.6666666666666666)) + 2.0) / Math.sqrt(Math.PI)) * Math.abs(x)));
}

Python

def code(x):
	return math.fabs(((1.0 / math.sqrt(math.pi)) * ((((2.0 * math.fabs(x)) + ((2.0 / 3.0) * ((math.fabs(x) * math.fabs(x)) * math.fabs(x)))) + ((1.0 / 5.0) * ((((math.fabs(x) * math.fabs(x)) * math.fabs(x)) * math.fabs(x)) * math.fabs(x)))) + ((1.0 / 21.0) * ((((((math.fabs(x) * math.fabs(x)) * math.fabs(x)) * math.fabs(x)) * math.fabs(x)) * math.fabs(x)) * math.fabs(x))))))

↓

def code(x):
	return math.fabs((((((x * x) * ((((x * ((0.047619047619047616 * x) * x)) + (x * 0.2)) * x) + 0.6666666666666666)) + 2.0) / math.sqrt(math.pi)) * math.fabs(x)))

Julia

function code(x)
	return abs(Float64(Float64(1.0 / sqrt(pi)) * Float64(Float64(Float64(Float64(2.0 * abs(x)) + Float64(Float64(2.0 / 3.0) * Float64(Float64(abs(x) * abs(x)) * abs(x)))) + Float64(Float64(1.0 / 5.0) * Float64(Float64(Float64(Float64(abs(x) * abs(x)) * abs(x)) * abs(x)) * abs(x)))) + Float64(Float64(1.0 / 21.0) * Float64(Float64(Float64(Float64(Float64(Float64(abs(x) * abs(x)) * abs(x)) * abs(x)) * abs(x)) * abs(x)) * abs(x))))))
end

↓

function code(x)
	return abs(Float64(Float64(Float64(Float64(Float64(x * x) * Float64(Float64(Float64(Float64(x * Float64(Float64(0.047619047619047616 * x) * x)) + Float64(x * 0.2)) * x) + 0.6666666666666666)) + 2.0) / sqrt(pi)) * abs(x)))
end

MATLAB

function tmp = code(x)
	tmp = abs(((1.0 / sqrt(pi)) * ((((2.0 * abs(x)) + ((2.0 / 3.0) * ((abs(x) * abs(x)) * abs(x)))) + ((1.0 / 5.0) * ((((abs(x) * abs(x)) * abs(x)) * abs(x)) * abs(x)))) + ((1.0 / 21.0) * ((((((abs(x) * abs(x)) * abs(x)) * abs(x)) * abs(x)) * abs(x)) * abs(x))))));
end

↓

function tmp = code(x)
	tmp = abs((((((x * x) * ((((x * ((0.047619047619047616 * x) * x)) + (x * 0.2)) * x) + 0.6666666666666666)) + 2.0) / sqrt(pi)) * abs(x)));
end

Wolfram

code[x_] := N[Abs[N[(N[(1.0 / N[Sqrt[Pi], $MachinePrecision]), $MachinePrecision] * N[(N[(N[(N[(2.0 * N[Abs[x], $MachinePrecision]), $MachinePrecision] + N[(N[(2.0 / 3.0), $MachinePrecision] * N[(N[(N[Abs[x], $MachinePrecision] * N[Abs[x], $MachinePrecision]), $MachinePrecision] * N[Abs[x], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] + N[(N[(1.0 / 5.0), $MachinePrecision] * N[(N[(N[(N[(N[Abs[x], $MachinePrecision] * N[Abs[x], $MachinePrecision]), $MachinePrecision] * N[Abs[x], $MachinePrecision]), $MachinePrecision] * N[Abs[x], $MachinePrecision]), $MachinePrecision] * N[Abs[x], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] + N[(N[(1.0 / 21.0), $MachinePrecision] * N[(N[(N[(N[(N[(N[(N[Abs[x], $MachinePrecision] * N[Abs[x], $MachinePrecision]), $MachinePrecision] * N[Abs[x], $MachinePrecision]), $MachinePrecision] * N[Abs[x], $MachinePrecision]), $MachinePrecision] * N[Abs[x], $MachinePrecision]), $MachinePrecision] * N[Abs[x], $MachinePrecision]), $MachinePrecision] * N[Abs[x], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]

↓

code[x_] := N[Abs[N[(N[(N[(N[(N[(x * x), $MachinePrecision] * N[(N[(N[(N[(x * N[(N[(0.047619047619047616 * x), $MachinePrecision] * x), $MachinePrecision]), $MachinePrecision] + N[(x * 0.2), $MachinePrecision]), $MachinePrecision] * x), $MachinePrecision] + 0.6666666666666666), $MachinePrecision]), $MachinePrecision] + 2.0), $MachinePrecision] / N[Sqrt[Pi], $MachinePrecision]), $MachinePrecision] * N[Abs[x], $MachinePrecision]), $MachinePrecision]], $MachinePrecision]

Derivation

1. Initial program 0.2

   \[\left|\frac{1}{\sqrt{\pi}} \cdot \left(\left(\left(2 \cdot \left|x\right| + \frac{2}{3} \cdot \left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right) + \frac{1}{5} \cdot \left(\left(\left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right) + \frac{1}{21} \cdot \left(\left(\left(\left(\left(\left(\left|x\right| \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right) \cdot \left|x\right|\right)\right)\right| \]

2. Simplified 0.5

   \[\leadsto \color{blue}{\left|\frac{\left|x\right| \cdot \left({\left(x \cdot x\right)}^{2} \cdot \left(0.2 + 0.047619047619047616 \cdot \left(x \cdot x\right)\right) + \mathsf{fma}\left(0.6666666666666666 \cdot x, x, 2\right)\right)}{\sqrt{\pi}}\right|} \]
   Proof

3. Applied egg-rr 0.1

   \[\leadsto \left|\color{blue}{\frac{\left(x \cdot x\right) \cdot \left(\mathsf{fma}\left(0.047619047619047616 \cdot x, x, 0.2\right) \cdot \left(x \cdot x\right) + 0.6666666666666666\right) + 2}{\sqrt{\pi}} \cdot \left|x\right|}\right| \]

4. Applied egg-rr 0.1

   \[\leadsto \left|\frac{\left(x \cdot x\right) \cdot \left(\color{blue}{\left(\mathsf{fma}\left(0.047619047619047616 \cdot x, x, 0.2\right) \cdot x\right) \cdot x} + 0.6666666666666666\right) + 2}{\sqrt{\pi}} \cdot \left|x\right|\right| \]

5. Applied egg-rr 0.1

   \[\leadsto \left|\frac{\left(x \cdot x\right) \cdot \left(\color{blue}{\left(x \cdot \left(\left(0.047619047619047616 \cdot x\right) \cdot x\right) + x \cdot 0.2\right)} \cdot x + 0.6666666666666666\right) + 2}{\sqrt{\pi}} \cdot \left|x\right|\right| \]

Alternatives

Alternative 1
Error	4.2
Cost	26624

\[\left|\frac{\left(x \cdot x\right) \cdot \left(0.2 \cdot \left(x \cdot x\right) + 0.6666666666666666\right) + 2}{\sqrt{\pi}} \cdot \left|x\right|\right| \]

Alternative 2
Error	4.3
Cost	26368

\[\left|\frac{1}{\sqrt{\pi}} \cdot \left(\left|x\right| \cdot \left(\left(x \cdot x\right) \cdot 0.6666666666666666 + 2\right)\right)\right| \]

Alternative 3
Error	4.3
Cost	26240

\[\left|\frac{\left(x \cdot 0.6666666666666666\right) \cdot x + 2}{\sqrt{\pi}} \cdot \left|x\right|\right| \]

Alternative 4
Error	4.6
Cost	25856

\[\left|\frac{2}{\sqrt{\pi}} \cdot \left|x\right|\right| \]

Reproduce

herbie shell --seed 2023010 
(FPCore (x)
  :name "Jmat.Real.erfi, branch x less than or equal to 0.5"
  :precision binary64
  :pre (<= x 0.5)
  (fabs (* (/ 1.0 (sqrt PI)) (+ (+ (+ (* 2.0 (fabs x)) (* (/ 2.0 3.0) (* (* (fabs x) (fabs x)) (fabs x)))) (* (/ 1.0 5.0) (* (* (* (* (fabs x) (fabs x)) (fabs x)) (fabs x)) (fabs x)))) (* (/ 1.0 21.0) (* (* (* (* (* (* (fabs x) (fabs x)) (fabs x)) (fabs x)) (fabs x)) (fabs x)) (fabs x)))))))