1 - \left(\frac{1}{1 + 0.3275911 \cdot \left|x\right|} \cdot \left(0.254829592 + \frac{1}{1 + 0.3275911 \cdot \left|x\right|} \cdot \left(-0.284496736 + \frac{1}{1 + 0.3275911 \cdot \left|x\right|} \cdot \left(1.421413741 + \frac{1}{1 + 0.3275911 \cdot \left|x\right|} \cdot \left(-1.453152027 + \frac{1}{1 + 0.3275911 \cdot \left|x\right|} \cdot 1.061405429\right)\right)\right)\right)\right) \cdot e^{-\left|x\right| \cdot \left|x\right|}\frac{1 - \sqrt{{\left(\frac{0.254829592 + \frac{-0.284496736 + \frac{1.421413741 + \frac{-1.453152027 + \frac{1.061405429}{1 + 0.3275911 \cdot \left|x\right|}}{1 + 0.3275911 \cdot \left|x\right|}}{1 + 0.3275911 \cdot \left|x\right|}}{1 + 0.3275911 \cdot \left|x\right|}}{\left(1 + 0.3275911 \cdot \left|x\right|\right) \cdot e^{{\left(\left|x\right|\right)}^{2}}}\right)}^{3}} \cdot \sqrt{{\left(\frac{0.254829592 + \frac{-0.284496736 + \frac{1.421413741 + \frac{-1.453152027 + \frac{1.061405429}{1 + 0.3275911 \cdot \left|x\right|}}{1 + 0.3275911 \cdot \left|x\right|}}{1 + 0.3275911 \cdot \left|x\right|}}{1 + 0.3275911 \cdot \left|x\right|}}{\left(1 + 0.3275911 \cdot \left|x\right|\right) \cdot e^{{\left(\left|x\right|\right)}^{2}}}\right)}^{3}}}{1 + \frac{0.254829592 + \frac{-0.284496736 + \frac{1.421413741 + \frac{-1.453152027 + \frac{1.061405429}{1 + 0.3275911 \cdot \left|x\right|}}{1 + 0.3275911 \cdot \left|x\right|}}{1 + 0.3275911 \cdot \left|x\right|}}{1 + 0.3275911 \cdot \left|x\right|}}{\left(1 + 0.3275911 \cdot \left|x\right|\right) \cdot e^{{\left(\left|x\right|\right)}^{2}}} \cdot \left(1 + \frac{0.254829592 + \frac{-0.284496736 + \frac{1.421413741 + \frac{-1.453152027 + \frac{1.061405429}{1 + 0.3275911 \cdot \left|x\right|}}{1 + 0.3275911 \cdot \left|x\right|}}{1 + 0.3275911 \cdot \left|x\right|}}{1 + 0.3275911 \cdot \left|x\right|}}{\left(1 + 0.3275911 \cdot \left|x\right|\right) \cdot e^{{\left(\left|x\right|\right)}^{2}}}\right)}(FPCore (x)
:precision binary64
(-
1.0
(*
(*
(/ 1.0 (+ 1.0 (* 0.3275911 (fabs x))))
(+
0.254829592
(*
(/ 1.0 (+ 1.0 (* 0.3275911 (fabs x))))
(+
-0.284496736
(*
(/ 1.0 (+ 1.0 (* 0.3275911 (fabs x))))
(+
1.421413741
(*
(/ 1.0 (+ 1.0 (* 0.3275911 (fabs x))))
(+
-1.453152027
(* (/ 1.0 (+ 1.0 (* 0.3275911 (fabs x)))) 1.061405429)))))))))
(exp (- (* (fabs x) (fabs x)))))))(FPCore (x)
:precision binary64
(/
(-
1.0
(*
(sqrt
(pow
(/
(+
0.254829592
(/
(+
-0.284496736
(/
(+
1.421413741
(/
(+ -1.453152027 (/ 1.061405429 (+ 1.0 (* 0.3275911 (fabs x)))))
(+ 1.0 (* 0.3275911 (fabs x)))))
(+ 1.0 (* 0.3275911 (fabs x)))))
(+ 1.0 (* 0.3275911 (fabs x)))))
(* (+ 1.0 (* 0.3275911 (fabs x))) (exp (pow (fabs x) 2.0))))
3.0))
(sqrt
(pow
(/
(+
0.254829592
(/
(+
-0.284496736
(/
(+
1.421413741
(/
(+ -1.453152027 (/ 1.061405429 (+ 1.0 (* 0.3275911 (fabs x)))))
(+ 1.0 (* 0.3275911 (fabs x)))))
(+ 1.0 (* 0.3275911 (fabs x)))))
(+ 1.0 (* 0.3275911 (fabs x)))))
(* (+ 1.0 (* 0.3275911 (fabs x))) (exp (pow (fabs x) 2.0))))
3.0))))
(+
1.0
(*
(/
(+
0.254829592
(/
(+
-0.284496736
(/
(+
1.421413741
(/
(+ -1.453152027 (/ 1.061405429 (+ 1.0 (* 0.3275911 (fabs x)))))
(+ 1.0 (* 0.3275911 (fabs x)))))
(+ 1.0 (* 0.3275911 (fabs x)))))
(+ 1.0 (* 0.3275911 (fabs x)))))
(* (+ 1.0 (* 0.3275911 (fabs x))) (exp (pow (fabs x) 2.0))))
(+
1.0
(/
(+
0.254829592
(/
(+
-0.284496736
(/
(+
1.421413741
(/
(+ -1.453152027 (/ 1.061405429 (+ 1.0 (* 0.3275911 (fabs x)))))
(+ 1.0 (* 0.3275911 (fabs x)))))
(+ 1.0 (* 0.3275911 (fabs x)))))
(+ 1.0 (* 0.3275911 (fabs x)))))
(* (+ 1.0 (* 0.3275911 (fabs x))) (exp (pow (fabs x) 2.0)))))))))double code(double x) {
return 1.0 - (((1.0 / (1.0 + (0.3275911 * fabs(x)))) * (0.254829592 + ((1.0 / (1.0 + (0.3275911 * fabs(x)))) * (-0.284496736 + ((1.0 / (1.0 + (0.3275911 * fabs(x)))) * (1.421413741 + ((1.0 / (1.0 + (0.3275911 * fabs(x)))) * (-1.453152027 + ((1.0 / (1.0 + (0.3275911 * fabs(x)))) * 1.061405429))))))))) * exp(-(fabs(x) * fabs(x))));
}
double code(double x) {
return (1.0 - (sqrt(pow(((0.254829592 + ((-0.284496736 + ((1.421413741 + ((-1.453152027 + (1.061405429 / (1.0 + (0.3275911 * fabs(x))))) / (1.0 + (0.3275911 * fabs(x))))) / (1.0 + (0.3275911 * fabs(x))))) / (1.0 + (0.3275911 * fabs(x))))) / ((1.0 + (0.3275911 * fabs(x))) * exp(pow(fabs(x), 2.0)))), 3.0)) * sqrt(pow(((0.254829592 + ((-0.284496736 + ((1.421413741 + ((-1.453152027 + (1.061405429 / (1.0 + (0.3275911 * fabs(x))))) / (1.0 + (0.3275911 * fabs(x))))) / (1.0 + (0.3275911 * fabs(x))))) / (1.0 + (0.3275911 * fabs(x))))) / ((1.0 + (0.3275911 * fabs(x))) * exp(pow(fabs(x), 2.0)))), 3.0)))) / (1.0 + (((0.254829592 + ((-0.284496736 + ((1.421413741 + ((-1.453152027 + (1.061405429 / (1.0 + (0.3275911 * fabs(x))))) / (1.0 + (0.3275911 * fabs(x))))) / (1.0 + (0.3275911 * fabs(x))))) / (1.0 + (0.3275911 * fabs(x))))) / ((1.0 + (0.3275911 * fabs(x))) * exp(pow(fabs(x), 2.0)))) * (1.0 + ((0.254829592 + ((-0.284496736 + ((1.421413741 + ((-1.453152027 + (1.061405429 / (1.0 + (0.3275911 * fabs(x))))) / (1.0 + (0.3275911 * fabs(x))))) / (1.0 + (0.3275911 * fabs(x))))) / (1.0 + (0.3275911 * fabs(x))))) / ((1.0 + (0.3275911 * fabs(x))) * exp(pow(fabs(x), 2.0)))))));
}



Bits error versus x
Results
Initial program 14.0
Simplified14.0
rmApplied flip3--_binary6414.0
Simplified14.0
Simplified14.0
rmApplied add-sqr-sqrt_binary6413.2
Final simplification13.2
herbie shell --seed 2020232
(FPCore (x)
:name "Jmat.Real.erf"
:precision binary64
(- 1.0 (* (* (/ 1.0 (+ 1.0 (* 0.3275911 (fabs x)))) (+ 0.254829592 (* (/ 1.0 (+ 1.0 (* 0.3275911 (fabs x)))) (+ -0.284496736 (* (/ 1.0 (+ 1.0 (* 0.3275911 (fabs x)))) (+ 1.421413741 (* (/ 1.0 (+ 1.0 (* 0.3275911 (fabs x)))) (+ -1.453152027 (* (/ 1.0 (+ 1.0 (* 0.3275911 (fabs x)))) 1.061405429))))))))) (exp (- (* (fabs x) (fabs x)))))))