DSYT01 reconstructs a symmetric 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.

UPLO

          UPLO is CHARACTER*1


          Specifies whether the upper or lower triangular part of the


          symmetric matrix A is stored:


          = 'U':  Upper triangular


          = 'L':  Lower triangular

N

          N is INTEGER


          The number of rows and columns of the matrix A.  N >= 0.

A

          A is DOUBLE PRECISION array, dimension (LDA,N)


          The original symmetric matrix A.

LDA

          LDA is INTEGER


          The leading dimension of the array A.  LDA >= max(1,N)

AFAC

          AFAC is DOUBLE PRECISION 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 DSYTRF.

LDAFAC

          LDAFAC is INTEGER


          The leading dimension of the array AFAC.  LDAFAC >= max(1,N).

IPIV

          IPIV is INTEGER array, dimension (N)


          The pivot indices from DSYTRF.

C

          C is DOUBLE PRECISION array, dimension (LDC,N)

LDC

          LDC is INTEGER


          The leading dimension of the array C.  LDC >= max(1,N).

RWORK

          RWORK is DOUBLE PRECISION array, dimension (N)

RESID

          RESID is DOUBLE PRECISION


          If UPLO = 'L', norm(L*D*L' - A) / ( N * norm(A) * EPS )


          If UPLO = 'U', norm(U*D*U' - A) / ( N * norm(A) * EPS )

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.