dsytri2.f - Man Page



subroutine dsytri2 (UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO)

Function/Subroutine Documentation

subroutine dsytri2 (character UPLO, integer N, double precision, dimension( lda, * ) A, integer LDA, integer, dimension( * ) IPIV, double precision, dimension( * ) WORK, integer LWORK, integer INFO)



 DSYTRI2 computes the inverse of a DOUBLE PRECISION symmetric indefinite matrix
 A using the factorization A = U*D*U**T or A = L*D*L**T computed by
 DSYTRF. DSYTRI2 sets the LEADING DIMENSION of the workspace
 before calling DSYTRI2X that actually computes the inverse.


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


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


          A is DOUBLE PRECISION array, dimension (LDA,N)
          On entry, the NB diagonal matrix D and the multipliers
          used to obtain the factor U or L as computed by DSYTRF.

          On exit, if INFO = 0, the (symmetric) inverse of the original
          matrix.  If UPLO = 'U', the upper triangular part of the
          inverse is formed and the part of A below the diagonal is not
          referenced; if UPLO = 'L' the lower triangular part of the
          inverse is formed and the part of A above the diagonal is
          not referenced.


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


          IPIV is INTEGER array, dimension (N)
          Details of the interchanges and the NB structure of D
          as determined by DSYTRF.


          WORK is DOUBLE PRECISION array, dimension (N+NB+1)*(NB+3)


          LWORK is INTEGER
          The dimension of the array WORK.
          WORK is size >= (N+NB+1)*(NB+3)
          If LDWORK = -1, then a workspace query is assumed; the routine
              - the optimal size of the WORK array, returns
          this value as the first entry of the WORK array,
              - and no error message related to LDWORK is issued by XERBLA.


          INFO is INTEGER
          = 0: successful exit
          < 0: if INFO = -i, the i-th argument had an illegal value
          > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its
               inverse could not be computed.

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.


November 2017

Definition at line 129 of file dsytri2.f.


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Referenced By

The man page dsytri2(3) is an alias of dsytri2.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK