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Lines Matching defs:erf

33 static char sccsid[] = "@(#)erf.c	8.1 (Berkeley) 6/4/93";
55 /* double erf(double x)
59  *     erf(x)  =  ---------  | exp(-t*t)dt
63  *     erfc(x) =  1-erf(x)
66  *      1. Reduce x to |x| by erf(-x) = -erf(x)
68  *	    erf(x)  = x + x*P(x^2)
69  *          erfc(x) = 1 - erf(x)           if x<=0.25
74  * 	   is an approximation to (erf(x)-x)/x with precision
77  *			| P - (erf(x)-x)/x | <= 2
81  *          erf(x) = (2/sqrt(pi))*(x - x^3/3 + x^5/10 - x^7/42 + ....)
85  *	   point of erf(x) is near 0.6174 (i.e., erf(x)=x when x is
87  * 	   guarantee the error is less than one ulp for erf.
91  *         	erf(x)  = c  + P1(s)/Q1(s)
93  *         	|P1/Q1 - (erf(x)-c)| <= 2**-59.06
95  *		erf(1+s) = erf(1) + s*Poly(s)
98  *			erf(1+s) - (c = (single)0.84506291151)
105  *         	erf(x)  = 1.0 - tiny
111  *         	erf(x)  = 1.0 - tiny
138  *         	erf(x)  = 1 - tiny  (raise inexact)
142  *         	erf(0)  = 0, erf(inf)  = 1, erf(-inf) = -1,
144  *	   	erfc/erf(NaN) is NaN
170  * Coefficients for approximation to erf in [0,0.84375]
185  * Coefficients for approximation to erf in [0.84375,1.25]
266 erf(double x)
269 	if(!finite(x)) {		/* erf(nan)=nan */
272 	    return (x > 0 ? one : -one); /* erf(+/-inf)= +/-1 */
326 	return (float)erf(x);