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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/slae2.c | |
parent | 01f64c1ecd0d4ffa9e3a74478335f1745f26cc75 (diff) | |
download | ydb-90d450f74722da7859d6f510a869f6c6908fd12f.tar.gz |
[] add metering mode to CLI
Diffstat (limited to 'contrib/libs/clapack/slae2.c')
-rw-r--r-- | contrib/libs/clapack/slae2.c | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/contrib/libs/clapack/slae2.c b/contrib/libs/clapack/slae2.c new file mode 100644 index 0000000000..c82234cbd4 --- /dev/null +++ b/contrib/libs/clapack/slae2.c @@ -0,0 +1,141 @@ +/* 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 "f2c.h" +#include "blaswrap.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_ */ |