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*> \brief \b SSYSWAPR applies an elementary permutation on the rows and columns of a symmetric matrix.
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
*> Download SSYSWAPR + dependencies
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/ssyswapr.f">
*> [TGZ]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/ssyswapr.f">
*> [ZIP]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/ssyswapr.f">
*> [TXT]</a>
*> \endhtmlonly
*
* Definition:
* ===========
*
* SUBROUTINE SSYSWAPR( UPLO, N, A, LDA, I1, I2)
*
* .. Scalar Arguments ..
* CHARACTER UPLO
* INTEGER I1, I2, LDA, N
* ..
* .. Array Arguments ..
* REAL A( LDA, N )
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> SSYSWAPR applies an elementary permutation on the rows and the columns of
*> a symmetric matrix.
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in] UPLO
*> \verbatim
*> UPLO is CHARACTER*1
*> Specifies whether the details of the factorization are stored
*> as an upper or lower triangular matrix.
*> = 'U': Upper triangular, form is A = U*D*U**T;
*> = 'L': Lower triangular, form is A = L*D*L**T.
*> \endverbatim
*>
*> \param[in] N
*> \verbatim
*> N is INTEGER
*> The order of the matrix A. N >= 0.
*> \endverbatim
*>
*> \param[in,out] A
*> \verbatim
*> A is REAL array, dimension (LDA,*)
*> On entry, the N-by-N matrix A. On exit, the permuted matrix
*> where the rows I1 and I2 and columns I1 and I2 are interchanged.
*> If UPLO = 'U', the interchanges are applied to the upper
*> triangular part and the strictly lower triangular part of A is
*> not referenced; if UPLO = 'L', the interchanges are applied to
*> the lower triangular part and the part of A above the diagonal
*> is not referenced.
*> \endverbatim
*>
*> \param[in] LDA
*> \verbatim
*> LDA is INTEGER
*> The leading dimension of the array A. LDA >= max(1,N).
*> \endverbatim
*>
*> \param[in] I1
*> \verbatim
*> I1 is INTEGER
*> Index of the first row to swap
*> \endverbatim
*>
*> \param[in] I2
*> \verbatim
*> I2 is INTEGER
*> Index of the second row to swap
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup heswapr
*
* =====================================================================
SUBROUTINE SSYSWAPR( UPLO, N, A, LDA, I1, I2)
*
* -- LAPACK auxiliary routine --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
* .. Scalar Arguments ..
CHARACTER UPLO
INTEGER I1, I2, LDA, N
* ..
* .. Array Arguments ..
REAL A( LDA, * )
*
* =====================================================================
*
* ..
* .. Local Scalars ..
LOGICAL UPPER
REAL TMP
*
* .. External Functions ..
LOGICAL LSAME
EXTERNAL LSAME
* ..
* .. External Subroutines ..
EXTERNAL SSWAP
* ..
* .. Executable Statements ..
*
UPPER = LSAME( UPLO, 'U' )
IF (UPPER) THEN
*
* UPPER
* first swap
* - swap column I1 and I2 from I1 to I1-1
CALL SSWAP( I1-1, A(1,I1), 1, A(1,I2), 1 )
*
* second swap :
* - swap A(I1,I1) and A(I2,I2)
* - swap row I1 from I1+1 to I2-1 with col I2 from I1+1 to I2-1
TMP=A(I1,I1)
A(I1,I1)=A(I2,I2)
A(I2,I2)=TMP
*
CALL SSWAP( I2-I1-1, A(I1,I1+1), LDA, A(I1+1,I2), 1 )
*
* third swap
* - swap row I1 and I2 from I2+1 to N
IF ( I2.LT.N )
$ CALL SSWAP( N-I2, A(I1,I2+1), LDA, A(I2,I2+1), LDA )
*
ELSE
*
* LOWER
* first swap
* - swap row I1 and I2 from I1 to I1-1
CALL SSWAP( I1-1, A(I1,1), LDA, A(I2,1), LDA )
*
* second swap :
* - swap A(I1,I1) and A(I2,I2)
* - swap col I1 from I1+1 to I2-1 with row I2 from I1+1 to I2-1
TMP=A(I1,I1)
A(I1,I1)=A(I2,I2)
A(I2,I2)=TMP
*
CALL SSWAP( I2-I1-1, A(I1+1,I1), 1, A(I2,I1+1), LDA )
*
* third swap
* - swap col I1 and I2 from I2+1 to N
IF ( I2.LT.N )
$ CALL SSWAP( N-I2, A(I2+1,I1), 1, A(I2+1,I2), 1 )
*
ENDIF
END SUBROUTINE SSYSWAPR
|
