LAPACK  3.5.0
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iladlr.f
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1 *> \brief \b ILADLR scans a matrix for its last non-zero row.
2 *
3 * =========== DOCUMENTATION ===========
4 *
5 * Online html documentation available at
6 * http://www.netlib.org/lapack/explore-html/
7 *
8 *> \htmlonly
9 *> Download ILADLR + dependencies
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11 *> [TGZ]</a>
12 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/iladlr.f">
13 *> [ZIP]</a>
14 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/iladlr.f">
15 *> [TXT]</a>
16 *> \endhtmlonly
17 *
18 * Definition:
19 * ===========
20 *
21 * INTEGER FUNCTION ILADLR( M, N, A, LDA )
22 *
23 * .. Scalar Arguments ..
24 * INTEGER M, N, LDA
25 * ..
26 * .. Array Arguments ..
27 * DOUBLE PRECISION A( LDA, * )
28 * ..
29 *
30 *
31 *> \par Purpose:
32 * =============
33 *>
34 *> \verbatim
35 *>
36 *> ILADLR 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 DOUBLE PRECISION 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 September 2012
75 *
76 *> \ingroup auxOTHERauxiliary
77 *
78 * =====================================================================
79  INTEGER FUNCTION iladlr( M, N, A, LDA )
80 *
81 * -- LAPACK auxiliary routine (version 3.4.2) --
82 * -- LAPACK is a software package provided by Univ. of Tennessee, --
83 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
84 * September 2012
85 *
86 * .. Scalar Arguments ..
87  INTEGER m, n, lda
88 * ..
89 * .. Array Arguments ..
90  DOUBLE PRECISION a( lda, * )
91 * ..
92 *
93 * =====================================================================
94 *
95 * .. Parameters ..
96  DOUBLE PRECISION zero
97  parameter( zero = 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  iladlr = m
107  ELSE IF( a(m, 1).NE.zero .OR. a(m, n).NE.zero ) THEN
108  iladlr = m
109  ELSE
110 * Scan up each column tracking the last zero row seen.
111  iladlr = 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  iladlr = max( iladlr, i )
118  END DO
119  END IF
120  RETURN
121  END