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Annotation of rpl/lapack/lapack/dlaset.f, revision 1.7

1.1       bertrand    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