csyswapr()

subroutine csyswapr	(	character	uplo,
		integer	n,
		complex, dimension( lda, n )	a,
		integer	lda,
		integer	i1,
		integer	i2 )

CSYSWAPR

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Purpose:

!>
!> CSYSWAPR applies an elementary permutation on the rows and the columns of
!> a symmetric matrix.
!> 

Parameters

[in]	UPLO	!> 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. !>
[in]	N	!> N is INTEGER !> The order of the matrix A. N >= 0. !>
[in,out]	A	!> A is COMPLEX array, dimension (LDA,N) !> 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. !>
[in]	LDA	!> LDA is INTEGER !> The leading dimension of the array A. LDA >= max(1,N). !>
[in]	I1	!> I1 is INTEGER !> Index of the first row to swap !>
[in]	I2	!> I2 is INTEGER !> Index of the second row to swap !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 97 of file csyswapr.f.

*
*  -- 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 ..
      COMPLEX          A( LDA, N )
*
*  =====================================================================
*
*     ..
*     .. Local Scalars ..
      LOGICAL            UPPER
      COMPLEX            TMP
*
*     .. External Functions ..
      LOGICAL            LSAME
      EXTERNAL           lsame
*     ..
*     .. External Subroutines ..
      EXTERNAL           cswap
*     ..
*     .. Executable Statements ..
*
      upper = lsame( uplo, 'U' )
      IF (upper) THEN
*
*         UPPER
*         first swap
*          - swap column I1 and I2 from I1 to I1-1
         CALL cswap( 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 cswap( 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 cswap( 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 cswap ( 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 cswap( 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 cswap( n-i2, a(i2+1,i1), 1, a(i2+1,i2), 1 )
*
      ENDIF

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