SRC/dsycon_3.f(3)          Library Functions Manual          SRC/dsycon_3.f(3)

NAME
       SRC/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)
       DSYCON_3

       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
       Generated automatically by Doxygen for LAPACK from the source code.

LAPACK                          Version 3.12.0               SRC/dsycon_3.f(3)