Statistiques
| Révision :

root / src / lapack / double / dlaset.f @ 9

Historique | Voir | Annoter | Télécharger (3,15 ko)

1 
      SUBROUTINE DLASET( UPLO, M, N, ALPHA, BETA, A, LDA )
2 
*
3 
*  -- LAPACK auxiliary routine (version 3.2) --
4 
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
5 
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
6 
*     November 2006
7 
*
8 
*     .. Scalar Arguments ..
9 
      CHARACTER          UPLO
10 
      INTEGER            LDA, M, N
11 
      DOUBLE PRECISION   ALPHA, BETA
12 
*     ..
13 
*     .. Array Arguments ..
14 
      DOUBLE PRECISION   A( LDA, * )
15 
*     ..
16 
*
17 
*  Purpose
18 
*  =======
19 
*
20 
*  DLASET initializes an m-by-n matrix A to BETA on the diagonal and
21 
*  ALPHA on the offdiagonals.
22 
*
23 
*  Arguments
24 
*  =========
25 
*
26 
*  UPLO    (input) CHARACTER*1
27 
*          Specifies the part of the matrix A to be set.
28 
*          = 'U':      Upper triangular part is set; the strictly lower
29 
*                      triangular part of A is not changed.
30 
*          = 'L':      Lower triangular part is set; the strictly upper
31 
*                      triangular part of A is not changed.
32 
*          Otherwise:  All of the matrix A is set.
33 
*
34 
*  M       (input) INTEGER
35 
*          The number of rows of the matrix A.  M >= 0.
36 
*
37 
*  N       (input) INTEGER
38 
*          The number of columns of the matrix A.  N >= 0.
39 
*
40 
*  ALPHA   (input) DOUBLE PRECISION
41 
*          The constant to which the offdiagonal elements are to be set.
42 
*
43 
*  BETA    (input) DOUBLE PRECISION
44 
*          The constant to which the diagonal elements are to be set.
45 
*
46 
*  A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
47 
*          On exit, the leading m-by-n submatrix of A is set as follows:
48 
*
49 
*          if UPLO = 'U', A(i,j) = ALPHA, 1<=i<=j-1, 1<=j<=n,
50 
*          if UPLO = 'L', A(i,j) = ALPHA, j+1<=i<=m, 1<=j<=n,
51 
*          otherwise,     A(i,j) = ALPHA, 1<=i<=m, 1<=j<=n, i.ne.j,
52 
*
53 
*          and, for all UPLO, A(i,i) = BETA, 1<=i<=min(m,n).
54 
*
55 
*  LDA     (input) INTEGER
56 
*          The leading dimension of the array A.  LDA >= max(1,M).
57 
*
58 
* =====================================================================
59 
*
60 
*     .. Local Scalars ..
61 
      INTEGER            I, J
62 
*     ..
63 
*     .. External Functions ..
64 
      LOGICAL            LSAME
65 
      EXTERNAL           LSAME
66 
*     ..
67 
*     .. Intrinsic Functions ..
68 
      INTRINSIC          MIN
69 
*     ..
70 
*     .. Executable Statements ..
71 
*
72 
      IF( LSAME( UPLO, 'U' ) ) THEN
73 
*
74 
*        Set the strictly upper triangular or trapezoidal part of the
75 
*        array to ALPHA.
76 
*
77 
         DO 20 J = 2, N
78 
            DO 10 I = 1, MIN( J-1, M )
79 
               A( I, J ) = ALPHA
80 
   10       CONTINUE
81 
   20    CONTINUE
82 
*
83 
      ELSE IF( LSAME( UPLO, 'L' ) ) THEN
84 
*
85 
*        Set the strictly lower triangular or trapezoidal part of the
86 
*        array to ALPHA.
87 
*
88 
         DO 40 J = 1, MIN( M, N )
89 
            DO 30 I = J + 1, M
90 
               A( I, J ) = ALPHA
91 
   30       CONTINUE
92 
   40    CONTINUE
93 
*
94 
      ELSE
95 
*
96 
*        Set the leading m-by-n submatrix to ALPHA.
97 
*
98 
         DO 60 J = 1, N
99 
            DO 50 I = 1, M
100 
               A( I, J ) = ALPHA
101 
   50       CONTINUE
102 
   60    CONTINUE
103 
      END IF
104 
*
105 
*     Set the first min(M,N) diagonal elements to BETA.
106 
*
107 
      DO 70 I = 1, MIN( M, N )
108 
         A( I, I ) = BETA
109 
   70 CONTINUE
110 
*
111 
      RETURN
112 
*
113 
*     End of DLASET
114 
*
115 
      END