csyt01_aa()

subroutine csyt01_aa	(	character	uplo,
		integer	n,
		complex, dimension( lda, * )	a,
		integer	lda,
		complex, dimension( ldafac, * )	afac,
		integer	ldafac,
		integer, dimension( * )	ipiv,
		complex, dimension( ldc, * )	c,
		integer	ldc,
		real, dimension( * )	rwork,
		real	resid )

CSYT01

Purpose:

!>
!> CSYT01 reconstructs a hermitian indefinite matrix A from its
!> block L*D*L' or U*D*U' factorization and computes the residual
!>    norm( C - A ) / ( N * norm(A) * EPS ),
!> where C is the reconstructed matrix and EPS is the machine epsilon.
!> 

Parameters

[in]	UPLO	!> UPLO is CHARACTER*1 !> Specifies whether the upper or lower triangular part of the !> hermitian matrix A is stored: !> = 'U': Upper triangular !> = 'L': Lower triangular !>
[in]	N	!> N is INTEGER !> The number of rows and columns of the matrix A. N >= 0. !>
[in]	A	!> A is REAL array, dimension (LDA,N) !> The original hermitian matrix A. !>
[in]	LDA	!> LDA is INTEGER !> The leading dimension of the array A. LDA >= max(1,N) !>
[in]	AFAC	!> AFAC is REAL array, dimension (LDAFAC,N) !> The factored form of the matrix A. AFAC contains the block !> diagonal matrix D and the multipliers used to obtain the !> factor L or U from the block L*D*L' or U*D*U' factorization !> as computed by CSYTRF. !>
[in]	LDAFAC	!> LDAFAC is INTEGER !> The leading dimension of the array AFAC. LDAFAC >= max(1,N). !>
[in]	IPIV	!> IPIV is INTEGER array, dimension (N) !> The pivot indices from CSYTRF. !>
[out]	C	!> C is REAL array, dimension (LDC,N) !>
[in]	LDC	!> LDC is INTEGER !> The leading dimension of the array C. LDC >= max(1,N). !>
[out]	RWORK	!> RWORK is REAL array, dimension (N) !>
[out]	RESID	!> RESID is REAL !> If UPLO = 'L', norm(L*D*L' - A) / ( N * norm(A) * EPS ) !> If UPLO = 'U', norm(U*D*U' - A) / ( N * norm(A) * EPS ) !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 122 of file csyt01_aa.f.

*
*  -- LAPACK test 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            LDA, LDAFAC, LDC, N
      REAL               RESID
*     ..
*     .. Array Arguments ..
      INTEGER            IPIV( * )
      COMPLEX            A( LDA, * ), AFAC( LDAFAC, * ), C( LDC, * )
      REAL               RWORK( * )
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      REAL               ZERO, ONE
      parameter( zero = 0.0e+0, one = 1.0e+0 )
      COMPLEX            CZERO, CONE
      parameter( czero = ( 0.0e+0, 0.0e+0 ),
     $                     cone  = ( 1.0e+0, 0.0e+0 ) )
*     ..
*     .. Local Scalars ..
      INTEGER            I, J
      REAL               ANORM, EPS
*     ..
*     .. External Functions ..
      LOGICAL            LSAME
      REAL               SLAMCH, CLANSY
      EXTERNAL           lsame, slamch, clansy
*     ..
*     .. External Subroutines ..
      EXTERNAL           claset, clavsy
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          real
*     ..
*     .. Executable Statements ..
*
*     Quick exit if N = 0.
*
      IF( n.LE.0 ) THEN
         resid = zero
         RETURN
      END IF
*
*     Determine EPS and the norm of A.
*
      eps = slamch( 'Epsilon' )
      anorm = clansy( '1', uplo, n, a, lda, rwork )
*
*     Initialize C to the tridiagonal matrix T.
*
      CALL claset( 'Full', n, n, czero, czero, c, ldc )
      CALL clacpy( 'F', 1, n, afac( 1, 1 ), ldafac+1, c( 1, 1 ), ldc+1 )
      IF( n.GT.1 ) THEN
         IF( lsame( uplo, 'U' ) ) THEN
            CALL clacpy( 'F', 1, n-1, afac( 1, 2 ), ldafac+1, c( 1, 2 ),
     $                   ldc+1 )
            CALL clacpy( 'F', 1, n-1, afac( 1, 2 ), ldafac+1, c( 2, 1 ),
     $                   ldc+1 )
         ELSE
            CALL clacpy( 'F', 1, n-1, afac( 2, 1 ), ldafac+1, c( 1, 2 ),
     $                   ldc+1 )
            CALL clacpy( 'F', 1, n-1, afac( 2, 1 ), ldafac+1, c( 2, 1 ),
     $                   ldc+1 )
         ENDIF
*
*        Call CTRMM to form the product U' * D (or L * D ).
*
         IF( lsame( uplo, 'U' ) ) THEN
            CALL ctrmm( 'Left', uplo, 'Transpose', 'Unit', n-1, n,
     $                  cone, afac( 1, 2 ), ldafac, c( 2, 1 ), ldc )
         ELSE
            CALL ctrmm( 'Left', uplo, 'No transpose', 'Unit', n-1, n,
     $                  cone, afac( 2, 1 ), ldafac, c( 2, 1 ), ldc )
         END IF
*
*        Call CTRMM again to multiply by U (or L ).
*
         IF( lsame( uplo, 'U' ) ) THEN
            CALL ctrmm( 'Right', uplo, 'No transpose', 'Unit', n, n-1,
     $                  cone, afac( 1, 2 ), ldafac, c( 1, 2 ), ldc )
         ELSE
            CALL ctrmm( 'Right', uplo, 'Transpose', 'Unit', n, n-1,
     $                  cone, afac( 2, 1 ), ldafac, c( 1, 2 ), ldc )
         END IF
      ENDIF
*
*     Apply symmetric pivots
*
      DO j = n, 1, -1
         i = ipiv( j )
         IF( i.NE.j )
     $      CALL cswap( n, c( j, 1 ), ldc, c( i, 1 ), ldc )
      END DO
      DO j = n, 1, -1
         i = ipiv( j )
         IF( i.NE.j )
     $      CALL cswap( n, c( 1, j ), 1, c( 1, i ), 1 )
      END DO
*
*
*     Compute the difference  C - A .
*
      IF( lsame( uplo, 'U' ) ) THEN
         DO j = 1, n
            DO i = 1, j
               c( i, j ) = c( i, j ) - a( i, j )
            END DO
         END DO
      ELSE
         DO j = 1, n
            DO i = j, n
               c( i, j ) = c( i, j ) - a( i, j )
            END DO
         END DO
      END IF
*
*     Compute norm( C - A ) / ( N * norm(A) * EPS )
*
      resid = clansy( '1', uplo, n, c, ldc, rwork )
*
      IF( anorm.LE.zero ) THEN
         IF( resid.NE.zero )
     $      resid = one / eps
      ELSE
         resid = ( ( resid / real( n ) ) / anorm ) / eps
      END IF
*
      RETURN
*
*     End of CSYT01_AA
*

Here is the call graph for this function:

Here is the caller graph for this function: