79 lines
1.7 KiB
C++
79 lines
1.7 KiB
C++
#ifdef __cplusplus
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extern "C" {
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#endif
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#include "lmp_f2c.h"
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int dlaev2_(doublereal *a, doublereal *b, doublereal *c__, doublereal *rt1, doublereal *rt2,
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doublereal *cs1, doublereal *sn1)
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{
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doublereal d__1;
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double sqrt(doublereal);
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doublereal ab, df, cs, ct, tb, sm, tn, rt, adf, acs;
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integer sgn1, sgn2;
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doublereal acmn, acmx;
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sm = *a + *c__;
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df = *a - *c__;
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adf = abs(df);
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tb = *b + *b;
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ab = abs(tb);
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if (abs(*a) > abs(*c__)) {
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acmx = *a;
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acmn = *c__;
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} else {
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acmx = *c__;
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acmn = *a;
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}
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if (adf > ab) {
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d__1 = ab / adf;
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rt = adf * sqrt(d__1 * d__1 + 1.);
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} else if (adf < ab) {
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d__1 = adf / ab;
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rt = ab * sqrt(d__1 * d__1 + 1.);
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} else {
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rt = ab * sqrt(2.);
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}
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if (sm < 0.) {
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*rt1 = (sm - rt) * .5;
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sgn1 = -1;
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*rt2 = acmx / *rt1 * acmn - *b / *rt1 * *b;
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} else if (sm > 0.) {
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*rt1 = (sm + rt) * .5;
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sgn1 = 1;
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*rt2 = acmx / *rt1 * acmn - *b / *rt1 * *b;
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} else {
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*rt1 = rt * .5;
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*rt2 = rt * -.5;
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sgn1 = 1;
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}
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if (df >= 0.) {
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cs = df + rt;
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sgn2 = 1;
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} else {
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cs = df - rt;
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sgn2 = -1;
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}
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acs = abs(cs);
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if (acs > ab) {
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ct = -tb / cs;
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*sn1 = 1. / sqrt(ct * ct + 1.);
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*cs1 = ct * *sn1;
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} else {
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if (ab == 0.) {
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*cs1 = 1.;
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*sn1 = 0.;
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} else {
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tn = -cs / tb;
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*cs1 = 1. / sqrt(tn * tn + 1.);
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*sn1 = tn * *cs1;
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}
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}
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if (sgn1 == sgn2) {
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tn = *cs1;
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*cs1 = -(*sn1);
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*sn1 = tn;
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}
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return 0;
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}
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#ifdef __cplusplus
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}
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#endif
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