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author | shmel1k <shmel1k@ydb.tech> | 2022-09-02 12:44:59 +0300 |
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committer | shmel1k <shmel1k@ydb.tech> | 2022-09-02 12:44:59 +0300 |
commit | 90d450f74722da7859d6f510a869f6c6908fd12f (patch) | |
tree | 538c718dedc76cdfe37ad6d01ff250dd930d9278 /contrib/libs/clapack/dlaev2.c | |
parent | 01f64c1ecd0d4ffa9e3a74478335f1745f26cc75 (diff) | |
download | ydb-90d450f74722da7859d6f510a869f6c6908fd12f.tar.gz |
[] add metering mode to CLI
Diffstat (limited to 'contrib/libs/clapack/dlaev2.c')
-rw-r--r-- | contrib/libs/clapack/dlaev2.c | 188 |
1 files changed, 188 insertions, 0 deletions
diff --git a/contrib/libs/clapack/dlaev2.c b/contrib/libs/clapack/dlaev2.c new file mode 100644 index 0000000000..6cd4c93fa6 --- /dev/null +++ b/contrib/libs/clapack/dlaev2.c @@ -0,0 +1,188 @@ +/* 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_ */ |