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slaset.f
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1 *> \brief \b SLASET initializes the off-diagonal elements and the diagonal elements of a matrix to given values.
2 *
3 * =========== DOCUMENTATION ===========
4 *
5 * Online html documentation available at
6 * http://www.netlib.org/lapack/explore-html/
7 *
8 *> \htmlonly
9 *> Download SLASET + 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/slaset.f">
13 *> [ZIP]</a>
14 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/slaset.f">
15 *> [TXT]</a>
16 *> \endhtmlonly
17 *
18 * Definition:
19 * ===========
20 *
21 * SUBROUTINE SLASET( UPLO, M, N, ALPHA, BETA, A, LDA )
22 *
23 * .. Scalar Arguments ..
24 * CHARACTER UPLO
25 * INTEGER LDA, M, N
26 * REAL ALPHA, BETA
27 * ..
28 * .. Array Arguments ..
29 * REAL A( LDA, * )
30 * ..
31 *
32 *
33 *> \par Purpose:
34 * =============
35 *>
36 *> \verbatim
37 *>
38 *> SLASET initializes an m-by-n matrix A to BETA on the diagonal and
39 *> ALPHA on the offdiagonals.
40 *> \endverbatim
41 *
42 * Arguments:
43 * ==========
44 *
45 *> \param[in] UPLO
46 *> \verbatim
47 *> UPLO is CHARACTER*1
48 *> Specifies the part of the matrix A to be set.
49 *> = 'U': Upper triangular part is set; the strictly lower
50 *> triangular part of A is not changed.
51 *> = 'L': Lower triangular part is set; the strictly upper
52 *> triangular part of A is not changed.
53 *> Otherwise: All of the matrix A is set.
54 *> \endverbatim
55 *>
56 *> \param[in] M
57 *> \verbatim
58 *> M is INTEGER
59 *> The number of rows of the matrix A. M >= 0.
60 *> \endverbatim
61 *>
62 *> \param[in] N
63 *> \verbatim
64 *> N is INTEGER
65 *> The number of columns of the matrix A. N >= 0.
66 *> \endverbatim
67 *>
68 *> \param[in] ALPHA
69 *> \verbatim
70 *> ALPHA is REAL
71 *> The constant to which the offdiagonal elements are to be set.
72 *> \endverbatim
73 *>
74 *> \param[in] BETA
75 *> \verbatim
76 *> BETA is REAL
77 *> The constant to which the diagonal elements are to be set.
78 *> \endverbatim
79 *>
80 *> \param[in,out] A
81 *> \verbatim
82 *> A is REAL array, dimension (LDA,N)
83 *> On exit, the leading m-by-n submatrix of A is set as follows:
84 *>
85 *> if UPLO = 'U', A(i,j) = ALPHA, 1<=i<=j-1, 1<=j<=n,
86 *> if UPLO = 'L', A(i,j) = ALPHA, j+1<=i<=m, 1<=j<=n,
87 *> otherwise, A(i,j) = ALPHA, 1<=i<=m, 1<=j<=n, i.ne.j,
88 *>
89 *> and, for all UPLO, A(i,i) = BETA, 1<=i<=min(m,n).
90 *> \endverbatim
91 *>
92 *> \param[in] LDA
93 *> \verbatim
94 *> LDA is INTEGER
95 *> The leading dimension of the array A. LDA >= max(1,M).
96 *> \endverbatim
97 *
98 * Authors:
99 * ========
100 *
101 *> \author Univ. of Tennessee
102 *> \author Univ. of California Berkeley
103 *> \author Univ. of Colorado Denver
104 *> \author NAG Ltd.
105 *
106 *> \date September 2012
107 *
108 *> \ingroup auxOTHERauxiliary
109 *
110 * =====================================================================
111  SUBROUTINE slaset( UPLO, M, N, ALPHA, BETA, A, LDA )
112 *
113 * -- LAPACK auxiliary routine (version 3.4.2) --
114 * -- LAPACK is a software package provided by Univ. of Tennessee, --
115 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
116 * September 2012
117 *
118 * .. Scalar Arguments ..
119  CHARACTER uplo
120  INTEGER lda, m, n
121  REAL alpha, beta
122 * ..
123 * .. Array Arguments ..
124  REAL a( lda, * )
125 * ..
126 *
127 * =====================================================================
128 *
129 * .. Local Scalars ..
130  INTEGER i, j
131 * ..
132 * .. External Functions ..
133  LOGICAL lsame
134  EXTERNAL lsame
135 * ..
136 * .. Intrinsic Functions ..
137  INTRINSIC min
138 * ..
139 * .. Executable Statements ..
140 *
141  IF( lsame( uplo, 'U' ) ) THEN
142 *
143 * Set the strictly upper triangular or trapezoidal part of the
144 * array to ALPHA.
145 *
146  DO 20 j = 2, n
147  DO 10 i = 1, min( j-1, m )
148  a( i, j ) = alpha
149  10 CONTINUE
150  20 CONTINUE
151 *
152  ELSE IF( lsame( uplo, 'L' ) ) THEN
153 *
154 * Set the strictly lower triangular or trapezoidal part of the
155 * array to ALPHA.
156 *
157  DO 40 j = 1, min( m, n )
158  DO 30 i = j + 1, m
159  a( i, j ) = alpha
160  30 CONTINUE
161  40 CONTINUE
162 *
163  ELSE
164 *
165 * Set the leading m-by-n submatrix to ALPHA.
166 *
167  DO 60 j = 1, n
168  DO 50 i = 1, m
169  a( i, j ) = alpha
170  50 CONTINUE
171  60 CONTINUE
172  END IF
173 *
174 * Set the first min(M,N) diagonal elements to BETA.
175 *
176  DO 70 i = 1, min( m, n )
177  a( i, i ) = beta
178  70 CONTINUE
179 *
180  RETURN
181 *
182 * End of SLASET
183 *
184  END