C program for floating point error function
erf(x) returns the error function of its argument
erfc(x) returns 1.0-erf(x)
${2 over sqrt(pi)} int from 0 to x e sup {-t sup 2} dt$
the entry for erfc is provided because of the
extreme loss of relative accuracy if erf(x) is
called for large x and the result subtracted
from 1. (e.g. for x= 10, 12 places are lost).
There are no error returns.
Coefficients for large x are #5667 from Hart & Cheney (18.72D).
static double torp
= 1.1283791670955125738961589031;
0.804373630960840172832162e5
,
0.740407142710151470082064e4
,
0.301782788536507577809226e4
,
0.380140318123903008244444e2
,
0.143383842191748205576712e2
,
-.288805137207594084924010e0
,
0.007547728033418631287834e0
,
0.804373630960840172826266e5
,
0.342165257924628539769006e5
,
0.637960017324428279487120e4
,
0.658070155459240506326937e3
,
0.380190713951939403753468e2
,
0.100000000000000000000000e1
,
0.18263348842295112592168999e4
,
0.28980293292167655611275846e4
,
0.2320439590251635247384768711e4
,
0.1143262070703886173606073338e4
,
0.3685196154710010637133875746e3
,
0.7708161730368428609781633646e2
,
0.9675807882987265400604202961e1
,
0.5641877825507397413087057563e0
,
0.18263348842295112595576438e4
,
0.495882756472114071495438422e4
,
0.60895424232724435504633068e4
,
0.4429612803883682726711528526e4
,
0.2094384367789539593790281779e4
,
0.6617361207107653469211984771e3
,
0.1371255960500622202878443578e3
,
0.1714980943627607849376131193e2
,
for(n
=0,d
=0,i
=M
-1; i
>=0; i
--){
return(sign
*torp
*arg
*n
/d
);
return(sign
*(1. - erfc(arg
)));
for(n
=0,d
=0,i
=N
-1; i
>=0; i
--){
return(exp(-arg
*arg
)*n
/d
);