dsycon_3.f(3)

NAME
dsycon_3.f

SYNOPSIS

  Functions/Subroutines
subroutine dsycon_3 (UPLO, N, A, LDA, E, IPIV, ANORM, RCOND, WORK, IWORK, INFO)
DSYCON_3

Function/Subroutine Documentation

  subroutine dsycon_3 (character UPLO, integer N, double precision, dimension( lda, * ) A, integer LDA, double precision, dimension( * ) E, integer, dimension( * ) IPIV, double precision ANORM, double precision RCOND, double precision, dimension( * ) WORK, integer, dimension( * ) IWORK, integer INFO)

Purpose:

     DSYCON_3 estimates the reciprocal of the condition number (in the
     1-norm) of a real symmetric matrix A using the factorization
     computed by DSYTRF_RK or DSYTRF_BK:
        A = P*U*D*(U**T)*(P**T) or A = P*L*D*(L**T)*(P**T),
     where U (or L) is unit upper (or lower) triangular matrix,
     U**T (or L**T) is the transpose of U (or L), P is a permutation
     matrix, P**T is the transpose of P, and D is symmetric and block
     diagonal with 1-by-1 and 2-by-2 diagonal blocks.
     An estimate is obtained for norm(inv(A)), and the reciprocal of the
     condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).
     This routine uses BLAS3 solver DSYTRS_3.

Parameters
    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 = P*U*D*(U**T)*(P**T);
              = 'L':  Lower triangular, form is A = P*L*D*(L**T)*(P**T).

    N

              N is INTEGER
              The order of the matrix A.  N >= 0.

    A

              A is DOUBLE PRECISION array, dimension (LDA,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.

    LDA

              LDA is INTEGER
              The leading dimension of the array A.  LDA >= 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.
              NOTE: For 1-by-1 diagonal block D(k), where
              1 <= k <= N, the element E(k) is not referenced in both
              UPLO = 'U' or UPLO = 'L' cases.

    IPIV

              IPIV is INTEGER array, dimension (N)
              Details of the interchanges and the block structure of D
              as determined by DSYTRF_RK or DSYTRF_BK.

    ANORM

              ANORM is DOUBLE PRECISION
              The 1-norm of the original matrix A.

    RCOND

              RCOND is DOUBLE PRECISION
              The reciprocal of the condition number of the matrix A,
              computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an
              estimate of the 1-norm of inv(A) computed in this routine.

    WORK

              WORK is DOUBLE PRECISION array, dimension (2*N)

    IWORK

              IWORK is INTEGER array, dimension (N)

    INFO

              INFO is INTEGER
              = 0:  successful exit
              < 0:  if INFO = -i, the i-th argument had an illegal value

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Contributors:

      June 2017,  Igor Kozachenko,
                      Computer Science Division,
                      University of California, Berkeley
      September 2007, Sven Hammarling, Nicholas J. Higham, Craig Lucas,
                      School of Mathematics,
                      University of Manchester

Definition at line 169 of file dsycon_3.f.

Author

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