ground/gcs/src/libs/eigen/lapack/ilazlr.f

   1 *> \brief \b ILAZLR
   2 *
   3 *  =========== DOCUMENTATION ===========
   4 *
   5 * Online html documentation available at
   6 *            http://www.netlib.org/lapack/explore-html/
   7 *
   8 *> \htmlonly
   9 *> Download ILAZLR + dependencies
  10 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/ilazlr.f">
  11 *> [TGZ]</a>
  12 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/ilazlr.f">
  13 *> [ZIP]</a>
  14 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/ilazlr.f">
  15 *> [TXT]</a>
  16 *> \endhtmlonly
  17 *
  18 *  Definition:
  19 *  ===========
  20 *
  21 *       INTEGER FUNCTION ILAZLR( M, N, A, LDA )
  22 *
  23 *       .. Scalar Arguments ..
  24 *       INTEGER            M, N, LDA
  25 *       ..
  26 *       .. Array Arguments ..
  27 *       COMPLEX*16         A( LDA, * )
  28 *       ..
  29 *
  30 *
  31 *> \par Purpose:
  32 *  =============
  33 *>
  34 *> \verbatim
  35 *>
  36 *> ILAZLR scans A for its last non-zero row.
  37 *> \endverbatim
  38 *
  39 *  Arguments:
  40 *  ==========
  41 *
  42 *> \param[in] M
  43 *> \verbatim
  44 *>          M is INTEGER
  45 *>          The number of rows of the matrix A.
  46 *> \endverbatim
  47 *>
  48 *> \param[in] N
  49 *> \verbatim
  50 *>          N is INTEGER
  51 *>          The number of columns of the matrix A.
  52 *> \endverbatim
  53 *>
  54 *> \param[in] A
  55 *> \verbatim
  56 *>          A is COMPLEX*16 array, dimension (LDA,N)
  57 *>          The m by n matrix A.
  58 *> \endverbatim
  59 *>
  60 *> \param[in] LDA
  61 *> \verbatim
  62 *>          LDA is INTEGER
  63 *>          The leading dimension of the array A. LDA >= max(1,M).
  64 *> \endverbatim
  65 *
  66 *  Authors:
  67 *  ========
  68 *
  69 *> \author Univ. of Tennessee
  70 *> \author Univ. of California Berkeley
  71 *> \author Univ. of Colorado Denver
  72 *> \author NAG Ltd.
  73 *
  74 *> \date April 2012
  75 *
  76 *> \ingroup complex16OTHERauxiliary
  77 *
  78 *  =====================================================================
  79       INTEGER FUNCTION ILAZLR( M, N, A, LDA )
  80 *
  81 *  -- LAPACK auxiliary routine (version 3.4.1) --
  82 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
  83 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
  84 *     April 2012
  85 *
  86 *     .. Scalar Arguments ..
  87       INTEGER            M, N, LDA
  88 *     ..
  89 *     .. Array Arguments ..
  90       COMPLEX*16         A( LDA, * )
  91 *     ..
  92 *
  93 *  =====================================================================
  94 *
  95 *     .. Parameters ..
  96       COMPLEX*16       ZERO
  97       PARAMETER ( ZERO = (0.0D+0, 0.0D+0) )
  98 *     ..
  99 *     .. Local Scalars ..
 100       INTEGER I, J
 101 *     ..
 102 *     .. Executable Statements ..
 103 *
 104 *     Quick test for the common case where one corner is non-zero.
 105       IF( M.EQ.0 ) THEN
 106          ILAZLR = M
 107       ELSE IF( A(M, 1).NE.ZERO .OR. A(M, N).NE.ZERO ) THEN
 108          ILAZLR = M
 109       ELSE
 110 *     Scan up each column tracking the last zero row seen.
 111          ILAZLR = 0
 112          DO J = 1, N
 113             I=M
 114             DO WHILE((A(MAX(I,1),J).EQ.ZERO).AND.(I.GE.1))
 115                I=I-1
 116             ENDDO
 117             ILAZLR = MAX( ILAZLR, I )
 118          END DO
 119       END IF
 120       RETURN
 121       END