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authorshmel1k <shmel1k@ydb.tech>2022-09-02 12:44:59 +0300
committershmel1k <shmel1k@ydb.tech>2022-09-02 12:44:59 +0300
commit90d450f74722da7859d6f510a869f6c6908fd12f (patch)
tree538c718dedc76cdfe37ad6d01ff250dd930d9278 /contrib/libs/clapack/dlaev2.c
parent01f64c1ecd0d4ffa9e3a74478335f1745f26cc75 (diff)
downloadydb-90d450f74722da7859d6f510a869f6c6908fd12f.tar.gz
[] add metering mode to CLI
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+/* dlaev2.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 "f2c.h"
+#include "blaswrap.h"
+
+/* Subroutine */ int dlaev2_(doublereal *a, doublereal *b, doublereal *c__,
+ doublereal *rt1, doublereal *rt2, doublereal *cs1, doublereal *sn1)
+{
+ /* System generated locals */
+ doublereal d__1;
+
+ /* Builtin functions */
+ double sqrt(doublereal);
+
+ /* Local variables */
+ doublereal ab, df, cs, ct, tb, sm, tn, rt, adf, acs;
+ integer sgn1, sgn2;
+ doublereal acmn, acmx;
+
+
+/* -- LAPACK auxiliary routine (version 3.2) -- */
+/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
+/* November 2006 */
+
+/* .. Scalar Arguments .. */
+/* .. */
+
+/* Purpose */
+/* ======= */
+
+/* DLAEV2 computes the eigendecomposition of a 2-by-2 symmetric matrix */
+/* [ A B ] */
+/* [ B C ]. */
+/* On return, RT1 is the eigenvalue of larger absolute value, RT2 is the */
+/* eigenvalue of smaller absolute value, and (CS1,SN1) is the unit right */
+/* eigenvector for RT1, giving the decomposition */
+
+/* [ CS1 SN1 ] [ A B ] [ CS1 -SN1 ] = [ RT1 0 ] */
+/* [-SN1 CS1 ] [ B C ] [ SN1 CS1 ] [ 0 RT2 ]. */
+
+/* Arguments */
+/* ========= */
+
+/* A (input) DOUBLE PRECISION */
+/* The (1,1) element of the 2-by-2 matrix. */
+
+/* B (input) DOUBLE PRECISION */
+/* The (1,2) element and the conjugate of the (2,1) element of */
+/* the 2-by-2 matrix. */
+
+/* C (input) DOUBLE PRECISION */
+/* The (2,2) element of the 2-by-2 matrix. */
+
+/* RT1 (output) DOUBLE PRECISION */
+/* The eigenvalue of larger absolute value. */
+
+/* RT2 (output) DOUBLE PRECISION */
+/* The eigenvalue of smaller absolute value. */
+
+/* CS1 (output) DOUBLE PRECISION */
+/* SN1 (output) DOUBLE PRECISION */
+/* The vector (CS1, SN1) is a unit right eigenvector for RT1. */
+
+/* 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. */
+
+/* CS1 and SN1 are accurate to a few ulps barring over/underflow. */
+
+/* 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 = abs(df);
+ tb = *b + *b;
+ ab = abs(tb);
+ if (abs(*a) > abs(*c__)) {
+ acmx = *a;
+ acmn = *c__;
+ } else {
+ acmx = *c__;
+ acmn = *a;
+ }
+ if (adf > ab) {
+/* Computing 2nd power */
+ d__1 = ab / adf;
+ rt = adf * sqrt(d__1 * d__1 + 1.);
+ } else if (adf < ab) {
+/* Computing 2nd power */
+ d__1 = adf / ab;
+ rt = ab * sqrt(d__1 * d__1 + 1.);
+ } else {
+
+/* Includes case AB=ADF=0 */
+
+ rt = ab * sqrt(2.);
+ }
+ if (sm < 0.) {
+ *rt1 = (sm - rt) * .5;
+ sgn1 = -1;
+
+/* 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.) {
+ *rt1 = (sm + rt) * .5;
+ sgn1 = 1;
+
+/* 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 * .5;
+ *rt2 = rt * -.5;
+ sgn1 = 1;
+ }
+
+/* Compute the eigenvector */
+
+ if (df >= 0.) {
+ cs = df + rt;
+ sgn2 = 1;
+ } else {
+ cs = df - rt;
+ sgn2 = -1;
+ }
+ acs = abs(cs);
+ if (acs > ab) {
+ ct = -tb / cs;
+ *sn1 = 1. / sqrt(ct * ct + 1.);
+ *cs1 = ct * *sn1;
+ } else {
+ if (ab == 0.) {
+ *cs1 = 1.;
+ *sn1 = 0.;
+ } else {
+ tn = -cs / tb;
+ *cs1 = 1. / sqrt(tn * tn + 1.);
+ *sn1 = tn * *cs1;
+ }
+ }
+ if (sgn1 == sgn2) {
+ tn = *cs1;
+ *cs1 = -(*sn1);
+ *sn1 = tn;
+ }
+ return 0;
+
+/* End of DLAEV2 */
+
+} /* dlaev2_ */