DSYT01_3 reconstructs a symmetric indefinite matrix A from its


 block L*D*L' or U*D*U' factorization computed by DSYTRF_RK


 (or DSYTRF_BK) 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)


          Diagonal of the block diagonal matrix D and factors U or L


          as computed by DSYTRF_RK and DSYTRF_BK:


            a) ONLY diagonal elements of the symmetric block diagonal


               matrix D on the diagonal of A, i.e. D(k,k) = A(k,k);


               (superdiagonal (or subdiagonal) elements of D


                should be provided on entry in array E), and


            b) If UPLO = 'U': factor U in the superdiagonal part of A.


               If UPLO = 'L': factor L in the subdiagonal part of A.

LDAFAC

          LDAFAC is INTEGER


          The leading dimension of the array AFAC.


          LDAFAC >= max(1,N).

E

          E is DOUBLE PRECISION array, dimension (N)


          On entry, contains the superdiagonal (or subdiagonal)


          elements of the symmetric block diagonal matrix D


          with 1-by-1 or 2-by-2 diagonal blocks, where


          If UPLO = 'U': E(i) = D(i-1,i),i=2:N, E(1) not referenced;


          If UPLO = 'L': E(i) = D(i+1,i),i=1:N-1, E(N) not referenced.

IPIV

          IPIV is INTEGER array, dimension (N)


          The pivot indices from DSYTRF_RK (or DSYTRF_BK).

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

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