mirror of
https://github.com/opencv/opencv.git
synced 2024-12-11 14:39:11 +08:00
142 lines
3.6 KiB
C
142 lines
3.6 KiB
C
/* slae2.f -- translated by f2c (version 20061008).
|
|
You must link the resulting object file with libf2c:
|
|
on Microsoft Windows system, link with libf2c.lib;
|
|
on Linux or Unix systems, link with .../path/to/libf2c.a -lm
|
|
or, if you install libf2c.a in a standard place, with -lf2c -lm
|
|
-- in that order, at the end of the command line, as in
|
|
cc *.o -lf2c -lm
|
|
Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
|
|
|
|
http://www.netlib.org/f2c/libf2c.zip
|
|
*/
|
|
|
|
#include "clapack.h"
|
|
|
|
|
|
/* Subroutine */ int slae2_(real *a, real *b, real *c__, real *rt1, real *rt2)
|
|
{
|
|
/* System generated locals */
|
|
real r__1;
|
|
|
|
/* Builtin functions */
|
|
double sqrt(doublereal);
|
|
|
|
/* Local variables */
|
|
real ab, df, tb, sm, rt, adf, acmn, acmx;
|
|
|
|
|
|
/* -- LAPACK auxiliary routine (version 3.2) -- */
|
|
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
|
|
/* November 2006 */
|
|
|
|
/* .. Scalar Arguments .. */
|
|
/* .. */
|
|
|
|
/* Purpose */
|
|
/* ======= */
|
|
|
|
/* SLAE2 computes the eigenvalues of a 2-by-2 symmetric matrix */
|
|
/* [ A B ] */
|
|
/* [ B C ]. */
|
|
/* On return, RT1 is the eigenvalue of larger absolute value, and RT2 */
|
|
/* is the eigenvalue of smaller absolute value. */
|
|
|
|
/* Arguments */
|
|
/* ========= */
|
|
|
|
/* A (input) REAL */
|
|
/* The (1,1) element of the 2-by-2 matrix. */
|
|
|
|
/* B (input) REAL */
|
|
/* The (1,2) and (2,1) elements of the 2-by-2 matrix. */
|
|
|
|
/* C (input) REAL */
|
|
/* The (2,2) element of the 2-by-2 matrix. */
|
|
|
|
/* RT1 (output) REAL */
|
|
/* The eigenvalue of larger absolute value. */
|
|
|
|
/* RT2 (output) REAL */
|
|
/* The eigenvalue of smaller absolute value. */
|
|
|
|
/* Further Details */
|
|
/* =============== */
|
|
|
|
/* RT1 is accurate to a few ulps barring over/underflow. */
|
|
|
|
/* RT2 may be inaccurate if there is massive cancellation in the */
|
|
/* determinant A*C-B*B; higher precision or correctly rounded or */
|
|
/* correctly truncated arithmetic would be needed to compute RT2 */
|
|
/* accurately in all cases. */
|
|
|
|
/* Overflow is possible only if RT1 is within a factor of 5 of overflow. */
|
|
/* Underflow is harmless if the input data is 0 or exceeds */
|
|
/* underflow_threshold / macheps. */
|
|
|
|
/* ===================================================================== */
|
|
|
|
/* .. Parameters .. */
|
|
/* .. */
|
|
/* .. Local Scalars .. */
|
|
/* .. */
|
|
/* .. Intrinsic Functions .. */
|
|
/* .. */
|
|
/* .. Executable Statements .. */
|
|
|
|
/* Compute the eigenvalues */
|
|
|
|
sm = *a + *c__;
|
|
df = *a - *c__;
|
|
adf = dabs(df);
|
|
tb = *b + *b;
|
|
ab = dabs(tb);
|
|
if (dabs(*a) > dabs(*c__)) {
|
|
acmx = *a;
|
|
acmn = *c__;
|
|
} else {
|
|
acmx = *c__;
|
|
acmn = *a;
|
|
}
|
|
if (adf > ab) {
|
|
/* Computing 2nd power */
|
|
r__1 = ab / adf;
|
|
rt = adf * sqrt(r__1 * r__1 + 1.f);
|
|
} else if (adf < ab) {
|
|
/* Computing 2nd power */
|
|
r__1 = adf / ab;
|
|
rt = ab * sqrt(r__1 * r__1 + 1.f);
|
|
} else {
|
|
|
|
/* Includes case AB=ADF=0 */
|
|
|
|
rt = ab * sqrt(2.f);
|
|
}
|
|
if (sm < 0.f) {
|
|
*rt1 = (sm - rt) * .5f;
|
|
|
|
/* Order of execution important. */
|
|
/* To get fully accurate smaller eigenvalue, */
|
|
/* next line needs to be executed in higher precision. */
|
|
|
|
*rt2 = acmx / *rt1 * acmn - *b / *rt1 * *b;
|
|
} else if (sm > 0.f) {
|
|
*rt1 = (sm + rt) * .5f;
|
|
|
|
/* Order of execution important. */
|
|
/* To get fully accurate smaller eigenvalue, */
|
|
/* next line needs to be executed in higher precision. */
|
|
|
|
*rt2 = acmx / *rt1 * acmn - *b / *rt1 * *b;
|
|
} else {
|
|
|
|
/* Includes case RT1 = RT2 = 0 */
|
|
|
|
*rt1 = rt * .5f;
|
|
*rt2 = rt * -.5f;
|
|
}
|
|
return 0;
|
|
|
|
/* End of SLAE2 */
|
|
|
|
} /* slae2_ */
|