185 lines
4.8 KiB
Fortran
185 lines
4.8 KiB
Fortran
*> \brief \b DLASET initializes the off-diagonal elements and the diagonal elements of a matrix to given values.
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*
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* =========== DOCUMENTATION ===========
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*
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* Online html documentation available at
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* http://www.netlib.org/lapack/explore-html/
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*
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*> \htmlonly
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*> Download DLASET + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlaset.f">
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*> [TGZ]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlaset.f">
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*> [ZIP]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlaset.f">
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*> [TXT]</a>
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*> \endhtmlonly
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*
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* Definition:
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* ===========
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*
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* SUBROUTINE DLASET( UPLO, M, N, ALPHA, BETA, A, LDA )
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*
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* .. Scalar Arguments ..
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* CHARACTER UPLO
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* INTEGER LDA, M, N
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* DOUBLE PRECISION ALPHA, BETA
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* ..
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* .. Array Arguments ..
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* DOUBLE PRECISION A( LDA, * )
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* ..
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*
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*
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*> \par Purpose:
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* =============
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*>
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*> \verbatim
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*>
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*> DLASET initializes an m-by-n matrix A to BETA on the diagonal and
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*> ALPHA on the offdiagonals.
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*> \endverbatim
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*
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* Arguments:
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* ==========
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*
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*> \param[in] UPLO
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*> \verbatim
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*> UPLO is CHARACTER*1
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*> Specifies the part of the matrix A to be set.
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*> = 'U': Upper triangular part is set; the strictly lower
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*> triangular part of A is not changed.
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*> = 'L': Lower triangular part is set; the strictly upper
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*> triangular part of A is not changed.
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*> Otherwise: All of the matrix A is set.
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*> \endverbatim
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*>
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*> \param[in] M
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*> \verbatim
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*> M is INTEGER
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*> The number of rows of the matrix A. M >= 0.
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*> \endverbatim
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*>
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*> \param[in] N
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*> \verbatim
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*> N is INTEGER
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*> The number of columns of the matrix A. N >= 0.
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*> \endverbatim
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*>
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*> \param[in] ALPHA
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*> \verbatim
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*> ALPHA is DOUBLE PRECISION
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*> The constant to which the offdiagonal elements are to be set.
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*> \endverbatim
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*>
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*> \param[in] BETA
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*> \verbatim
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*> BETA is DOUBLE PRECISION
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*> The constant to which the diagonal elements are to be set.
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*> \endverbatim
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*>
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*> \param[out] A
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*> \verbatim
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*> A is DOUBLE PRECISION array, dimension (LDA,N)
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*> On exit, the leading m-by-n submatrix of A is set as follows:
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*>
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*> if UPLO = 'U', A(i,j) = ALPHA, 1<=i<=j-1, 1<=j<=n,
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*> if UPLO = 'L', A(i,j) = ALPHA, j+1<=i<=m, 1<=j<=n,
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*> otherwise, A(i,j) = ALPHA, 1<=i<=m, 1<=j<=n, i.ne.j,
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*>
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*> and, for all UPLO, A(i,i) = BETA, 1<=i<=min(m,n).
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*> \endverbatim
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*>
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*> \param[in] LDA
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*> \verbatim
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*> LDA is INTEGER
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*> The leading dimension of the array A. LDA >= max(1,M).
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*> \endverbatim
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*
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* Authors:
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* ========
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*
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*> \author Univ. of Tennessee
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*> \author Univ. of California Berkeley
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*> \author Univ. of Colorado Denver
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*> \author NAG Ltd.
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*
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*> \date December 2016
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*
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*> \ingroup OTHERauxiliary
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*
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* =====================================================================
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SUBROUTINE DLASET( UPLO, M, N, ALPHA, BETA, A, LDA )
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*
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* -- LAPACK auxiliary routine (version 3.7.0) --
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* -- LAPACK is a software package provided by Univ. of Tennessee, --
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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* December 2016
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*
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* .. Scalar Arguments ..
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CHARACTER UPLO
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INTEGER LDA, M, N
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DOUBLE PRECISION ALPHA, BETA
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* ..
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* .. Array Arguments ..
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DOUBLE PRECISION A( LDA, * )
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* ..
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*
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* =====================================================================
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*
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* .. Local Scalars ..
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INTEGER I, J
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* ..
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* .. External Functions ..
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LOGICAL LSAME
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EXTERNAL LSAME
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC MIN
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* ..
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* .. Executable Statements ..
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*
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IF( LSAME( UPLO, 'U' ) ) THEN
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*
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* Set the strictly upper triangular or trapezoidal part of the
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* array to ALPHA.
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*
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DO 20 J = 2, N
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DO 10 I = 1, MIN( J-1, M )
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A( I, J ) = ALPHA
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10 CONTINUE
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20 CONTINUE
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*
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ELSE IF( LSAME( UPLO, 'L' ) ) THEN
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*
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* Set the strictly lower triangular or trapezoidal part of the
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* array to ALPHA.
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*
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DO 40 J = 1, MIN( M, N )
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DO 30 I = J + 1, M
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A( I, J ) = ALPHA
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30 CONTINUE
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40 CONTINUE
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*
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ELSE
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*
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* Set the leading m-by-n submatrix to ALPHA.
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*
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DO 60 J = 1, N
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DO 50 I = 1, M
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A( I, J ) = ALPHA
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50 CONTINUE
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60 CONTINUE
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END IF
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*
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* Set the first min(M,N) diagonal elements to BETA.
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*
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DO 70 I = 1, MIN( M, N )
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A( I, I ) = BETA
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70 CONTINUE
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*
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RETURN
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*
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* End of DLASET
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*
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END
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