99 lines
1.4 KiB
C
99 lines
1.4 KiB
C
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/**********
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Copyright 1991 Regents of the University of California. All rights reserved.
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**********/
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/*
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* Missing math functions
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*/
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#include <config.h>
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#include "ngspice.h"
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#include <stdio.h>
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#include "missing_math.h"
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#ifndef HAVE_LOGB
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double
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logb(double x)
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{
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double y = 0.0;
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if (x != 0.0)
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{
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if (x < 0.0)
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x = - x;
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while (x > 2.0)
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{
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y += 1.0;
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x /= 2.0;
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}
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while (x < 1.0)
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{
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y -= 1.0;
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x *= 2.0;
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}
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}
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else
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y = 0.0;
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return y;
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}
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#endif
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#ifndef HAVE_SCALB
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# ifdef HAVE_SCALBN
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# define scalb scalbn
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#else /* Chris Inbody */
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double
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scalb(double x, int n)
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{
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double y, z = 1.0, k = 2.0;
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if (n < 0) {
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n = -n;
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k = 0.5;
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}
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if (x != 0.0)
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for (y = 1.0; n; n >>= 1) {
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y *= k;
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if (n & 1)
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z *= y;
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}
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return x * z;
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}
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# endif /* HAVE_SCALBN */
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#endif /* HAVE_SCALB */
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#ifndef HAVE_ERFC
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/* From C. Hastings, Jr., Approximations for digital computers,
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Princeton Univ. Press, 1955.
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Approximation accurate to within 1.5E-7
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(making some assumptions about your machine's floating point mechanism)
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*/
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double
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erfc(double x)
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{
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double t, z;
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t = 1/(1 + 0.3275911*x);
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z = 1.061405429;
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z = -1.453152027 + t * z;
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z = 1.421413741 + t * z;
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z = -0.284496736 + t * z;
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z = 0.254829592 + t * z;
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z = exp(-x*x) * t * z;
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return(z);
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}
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#endif
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