LAPACK  3.10.1
LAPACK: Linear Algebra PACKage

◆ cslect()

logical function cslect ( complex  Z)

CSLECT

Purpose:
 CSLECT returns .TRUE. if the eigenvalue Z is to be selected,
 otherwise it returns .FALSE.
 It is used by CCHK41 to test if CGEES successfully sorts eigenvalues,
 and by CCHK43 to test if CGEESX successfully sorts eigenvalues.

 The common block /SSLCT/ controls how eigenvalues are selected.
 If SELOPT = 0, then CSLECT return .TRUE. when real(Z) is less than
 zero, and .FALSE. otherwise.
 If SELOPT is at least 1, CSLECT returns SELVAL(SELOPT) and adds 1
 to SELOPT, cycling back to 1 at SELMAX.
Parameters
[in]Z
          Z is COMPLEX
          The eigenvalue Z.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.

Definition at line 55 of file cslect.f.

56 *
57 * -- LAPACK test routine --
58 * -- LAPACK is a software package provided by Univ. of Tennessee, --
59 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
60 *
61 * .. Scalar Arguments ..
62  COMPLEX Z
63 * ..
64 *
65 * =====================================================================
66 *
67 * .. Parameters ..
68  REAL ZERO
69  parameter( zero = 0.0e0 )
70 * ..
71 * .. Local Scalars ..
72  INTEGER I
73  REAL RMIN, X
74 * ..
75 * .. Scalars in Common ..
76  INTEGER SELDIM, SELOPT
77 * ..
78 * .. Arrays in Common ..
79  LOGICAL SELVAL( 20 )
80  REAL SELWI( 20 ), SELWR( 20 )
81 * ..
82 * .. Common blocks ..
83  COMMON / sslct / selopt, seldim, selval, selwr, selwi
84 * ..
85 * .. Intrinsic Functions ..
86  INTRINSIC abs, cmplx, real
87 * ..
88 * .. Executable Statements ..
89 *
90  IF( selopt.EQ.0 ) THEN
91  cslect = ( real( z ).LT.zero )
92  ELSE
93  rmin = abs( z-cmplx( selwr( 1 ), selwi( 1 ) ) )
94  cslect = selval( 1 )
95  DO 10 i = 2, seldim
96  x = abs( z-cmplx( selwr( i ), selwi( i ) ) )
97  IF( x.LE.rmin ) THEN
98  rmin = x
99  cslect = selval( i )
100  END IF
101  10 CONTINUE
102  END IF
103  RETURN
104 *
105 * End of CSLECT
106 *
logical function cslect(Z)
CSLECT
Definition: cslect.f:56