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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/claev2.c | |
| parent | 01f64c1ecd0d4ffa9e3a74478335f1745f26cc75 (diff) | |
| download | ydb-90d450f74722da7859d6f510a869f6c6908fd12f.tar.gz | |
[] add metering mode to CLI
Diffstat (limited to 'contrib/libs/clapack/claev2.c')
| -rw-r--r-- | contrib/libs/clapack/claev2.c | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/contrib/libs/clapack/claev2.c b/contrib/libs/clapack/claev2.c new file mode 100644 index 0000000000..f2d1cc0eb3 --- /dev/null +++ b/contrib/libs/clapack/claev2.c @@ -0,0 +1,123 @@ +/* claev2.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 claev2_(complex *a, complex *b, complex *c__, real *rt1, + real *rt2, real *cs1, complex *sn1) +{ + /* System generated locals */ + real r__1, r__2, r__3; + complex q__1, q__2; + + /* Builtin functions */ + double c_abs(complex *); + void r_cnjg(complex *, complex *); + + /* Local variables */ + real t; + complex w; + extern /* Subroutine */ int slaev2_(real *, real *, real *, real *, real * +, real *, real *); + + +/* -- LAPACK auxiliary routine (version 3.2) -- */ +/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */ +/* November 2006 */ + +/* .. Scalar Arguments .. */ +/* .. */ + +/* Purpose */ +/* ======= */ + +/* CLAEV2 computes the eigendecomposition of a 2-by-2 Hermitian matrix */ +/* [ A B ] */ +/* [ CONJG(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 CONJG(SN1) ] [ A B ] [ CS1 -CONJG(SN1) ] = [ RT1 0 ] */ +/* [-SN1 CS1 ] [ CONJG(B) C ] [ SN1 CS1 ] [ 0 RT2 ]. */ + +/* Arguments */ +/* ========= */ + +/* A (input) COMPLEX */ +/* The (1,1) element of the 2-by-2 matrix. */ + +/* B (input) COMPLEX */ +/* The (1,2) element and the conjugate of the (2,1) element of */ +/* the 2-by-2 matrix. */ + +/* C (input) COMPLEX */ +/* 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. */ + +/* CS1 (output) REAL */ +/* SN1 (output) COMPLEX */ +/* 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 .. */ +/* .. */ +/* .. External Subroutines .. */ +/* .. */ +/* .. Intrinsic Functions .. */ +/* .. */ +/* .. Executable Statements .. */ + + if (c_abs(b) == 0.f) { + w.r = 1.f, w.i = 0.f; + } else { + r_cnjg(&q__2, b); + r__1 = c_abs(b); + q__1.r = q__2.r / r__1, q__1.i = q__2.i / r__1; + w.r = q__1.r, w.i = q__1.i; + } + r__1 = a->r; + r__2 = c_abs(b); + r__3 = c__->r; + slaev2_(&r__1, &r__2, &r__3, rt1, rt2, cs1, &t); + q__1.r = t * w.r, q__1.i = t * w.i; + sn1->r = q__1.r, sn1->i = q__1.i; + return 0; + +/* End of CLAEV2 */ + +} /* claev2_ */ |