Subroutine */
| 12832 | } /* slaeda_ */ |
| 12833 | |
| 12834 | /* Subroutine */ int slaev2_(real *a, real *b, real *c__, real *rt1, real * |
| 12835 | rt2, real *cs1, real *sn1) |
| 12836 | { |
| 12837 | /* System generated locals */ |
| 12838 | real r__1; |
| 12839 | |
| 12840 | /* Local variables */ |
| 12841 | static real ab, df, cs, ct, tb, sm, tn, rt, adf, acs; |
| 12842 | static integer sgn1, sgn2; |
| 12843 | static real acmn, acmx; |
| 12844 | |
| 12845 | |
| 12846 | /* |
| 12847 | -- LAPACK auxiliary routine (version 3.2) -- |
| 12848 | -- LAPACK is a software package provided by Univ. of Tennessee, -- |
| 12849 | -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- |
| 12850 | November 2006 |
| 12851 | |
| 12852 | |
| 12853 | Purpose |
| 12854 | ======= |
| 12855 | |
| 12856 | SLAEV2 computes the eigendecomposition of a 2-by-2 symmetric matrix |
| 12857 | [ A B ] |
| 12858 | [ B C ]. |
| 12859 | On return, RT1 is the eigenvalue of larger absolute value, RT2 is the |
| 12860 | eigenvalue of smaller absolute value, and (CS1,SN1) is the unit right |
| 12861 | eigenvector for RT1, giving the decomposition |
| 12862 | |
| 12863 | [ CS1 SN1 ] [ A B ] [ CS1 -SN1 ] = [ RT1 0 ] |
| 12864 | [-SN1 CS1 ] [ B C ] [ SN1 CS1 ] [ 0 RT2 ]. |
| 12865 | |
| 12866 | Arguments |
| 12867 | ========= |
| 12868 | |
| 12869 | A (input) REAL |
| 12870 | The (1,1) element of the 2-by-2 matrix. |
| 12871 | |
| 12872 | B (input) REAL |
| 12873 | The (1,2) element and the conjugate of the (2,1) element of |
| 12874 | the 2-by-2 matrix. |
| 12875 | |
| 12876 | C (input) REAL |
| 12877 | The (2,2) element of the 2-by-2 matrix. |
| 12878 | |
| 12879 | RT1 (output) REAL |
| 12880 | The eigenvalue of larger absolute value. |
| 12881 | |
| 12882 | RT2 (output) REAL |
| 12883 | The eigenvalue of smaller absolute value. |
| 12884 | |
| 12885 | CS1 (output) REAL |
| 12886 | SN1 (output) REAL |
| 12887 | The vector (CS1, SN1) is a unit right eigenvector for RT1. |
| 12888 | |
| 12889 | Further Details |
| 12890 | =============== |
| 12891 |