LAPACK 3.3.1 Linear Algebra PACKage

# slaset.f

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```00001       SUBROUTINE SLASET( UPLO, M, N, ALPHA, BETA, A, LDA )
00002 *
00003 *  -- LAPACK auxiliary routine (version 3.2) --
00004 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
00005 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
00006 *     November 2006
00007 *
00008 *     .. Scalar Arguments ..
00009       CHARACTER          UPLO
00010       INTEGER            LDA, M, N
00011       REAL               ALPHA, BETA
00012 *     ..
00013 *     .. Array Arguments ..
00014       REAL               A( LDA, * )
00015 *     ..
00016 *
00017 *  Purpose
00018 *  =======
00019 *
00020 *  SLASET initializes an m-by-n matrix A to BETA on the diagonal and
00021 *  ALPHA on the offdiagonals.
00022 *
00023 *  Arguments
00024 *  =========
00025 *
00026 *  UPLO    (input) CHARACTER*1
00027 *          Specifies the part of the matrix A to be set.
00028 *          = 'U':      Upper triangular part is set; the strictly lower
00029 *                      triangular part of A is not changed.
00030 *          = 'L':      Lower triangular part is set; the strictly upper
00031 *                      triangular part of A is not changed.
00032 *          Otherwise:  All of the matrix A is set.
00033 *
00034 *  M       (input) INTEGER
00035 *          The number of rows of the matrix A.  M >= 0.
00036 *
00037 *  N       (input) INTEGER
00038 *          The number of columns of the matrix A.  N >= 0.
00039 *
00040 *  ALPHA   (input) REAL
00041 *          The constant to which the offdiagonal elements are to be set.
00042 *
00043 *  BETA    (input) REAL
00044 *          The constant to which the diagonal elements are to be set.
00045 *
00046 *  A       (input/output) REAL array, dimension (LDA,N)
00047 *          On exit, the leading m-by-n submatrix of A is set as follows:
00048 *
00049 *          if UPLO = 'U', A(i,j) = ALPHA, 1<=i<=j-1, 1<=j<=n,
00050 *          if UPLO = 'L', A(i,j) = ALPHA, j+1<=i<=m, 1<=j<=n,
00051 *          otherwise,     A(i,j) = ALPHA, 1<=i<=m, 1<=j<=n, i.ne.j,
00052 *
00053 *          and, for all UPLO, A(i,i) = BETA, 1<=i<=min(m,n).
00054 *
00055 *  LDA     (input) INTEGER
00056 *          The leading dimension of the array A.  LDA >= max(1,M).
00057 *
00058 * =====================================================================
00059 *
00060 *     .. Local Scalars ..
00061       INTEGER            I, J
00062 *     ..
00063 *     .. External Functions ..
00064       LOGICAL            LSAME
00065       EXTERNAL           LSAME
00066 *     ..
00067 *     .. Intrinsic Functions ..
00068       INTRINSIC          MIN
00069 *     ..
00070 *     .. Executable Statements ..
00071 *
00072       IF( LSAME( UPLO, 'U' ) ) THEN
00073 *
00074 *        Set the strictly upper triangular or trapezoidal part of the
00075 *        array to ALPHA.
00076 *
00077          DO 20 J = 2, N
00078             DO 10 I = 1, MIN( J-1, M )
00079                A( I, J ) = ALPHA
00080    10       CONTINUE
00081    20    CONTINUE
00082 *
00083       ELSE IF( LSAME( UPLO, 'L' ) ) THEN
00084 *
00085 *        Set the strictly lower triangular or trapezoidal part of the
00086 *        array to ALPHA.
00087 *
00088          DO 40 J = 1, MIN( M, N )
00089             DO 30 I = J + 1, M
00090                A( I, J ) = ALPHA
00091    30       CONTINUE
00092    40    CONTINUE
00093 *
00094       ELSE
00095 *
00096 *        Set the leading m-by-n submatrix to ALPHA.
00097 *
00098          DO 60 J = 1, N
00099             DO 50 I = 1, M
00100                A( I, J ) = ALPHA
00101    50       CONTINUE
00102    60    CONTINUE
00103       END IF
00104 *
00105 *     Set the first min(M,N) diagonal elements to BETA.
00106 *
00107       DO 70 I = 1, MIN( M, N )
00108          A( I, I ) = BETA
00109    70 CONTINUE
00110 *
00111       RETURN
00112 *
00113 *     End of SLASET
00114 *
00115       END
```