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better erfc for lossy transmission line

This commit is contained in:
dwarning 2008-05-11 20:29:50 +00:00
parent a28ad1a197
commit 201f5f42d8
1 changed files with 27 additions and 3 deletions
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30
src/maths/misc/erfc.c
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@ -4,12 +4,12 @@ Author: 1987 Kartikeya Mayaram, U. C. Berkeley CAD Group
**********/
#include "ngspice.h"
#include "numglobs.h"
#include "numconst.h"
/* erfc computes the erfc(x) the code is from sedan's derfc.f */
#ifndef HAVE_ERFC
double erfc ( double x)
/* erfc computes the erfc(x) the code is from sedan's derfc.f */
double erfc (double x)
{
double sqrtPi, n, temp1, xSq, sum1, sum2;
sqrtPi = sqrt( PI );
@ -45,3 +45,27 @@ double erfc ( double x)
}
}
/* From C. Hastings, Jr., Approximations for digital computers,
Princeton Univ. Press, 1955.
Approximation accurate to within 1.5E-7
(making some assumptions about your machine's floating point mechanism)
*/
double
ierfc(double x)
{
double t, z;
t = 1/(1 + 0.3275911*x);
z = 1.061405429;
z = -1.453152027 + t * z;
z = 1.421413741 + t * z;
z = -0.284496736 + t * z;
z = 0.254829592 + t * z;
z = exp(-x*x) * t * z;
return(z);
}
#else
int Dummy_Symbol_5;
#endif