Loading...
Searching...
No Matches

## sgecon()

subroutine sgecon | ( | character | norm,
|  | integer | n,
|  | real, dimension( lda, * ) | a,
|  | integer | lda,
|  | real | anorm,
|  | real | rcond,
|  | real, dimension( * ) | work,
|  | integer, dimension( * ) | iwork,
|  | integer | info )

SGECON

Download SGECON + dependencies [TGZ] [ZIP] [TXT]

Purpose:

      !>
      !> SGECON estimates the reciprocal of the condition number of a general
      !> real matrix A, in either the 1-norm or the infinity-norm, using
      !> the LU factorization computed by SGETRF.
      !>
      !> An estimate is obtained for norm(inv(A)), and the reciprocal of the
      !> condition number is computed as
      !>    RCOND = 1 / ( norm(A) * norm(inv(A)) ).
      !>

Parameters

  [in]

  NORM

      !>          NORM is CHARACTER*1
      !>          Specifies whether the 1-norm condition number or the
      !>          infinity-norm condition number is required:
      !>          = '1' or 'O':  1-norm;
      !>          = 'I':         Infinity-norm.
      !>

  [in]

  N

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

  [in]

  A

      !>          A is REAL array, dimension (LDA,N)
      !>          The factors L and U from the factorization A = P*L*U
      !>          as computed by SGETRF.
      !>

  [in]

  LDA

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

  [in]

  ANORM

      !>          ANORM is REAL
      !>          If NORM = '1' or 'O', the 1-norm of the original matrix A.
      !>          If NORM = 'I', the infinity-norm of the original matrix A.
      !>

  [out]

  RCOND

      !>          RCOND is REAL
      !>          The reciprocal of the condition number of the matrix A,
      !>          computed as RCOND = 1/(norm(A) * norm(inv(A))).
      !>

  [out]

  WORK

      !>          WORK is REAL array, dimension (4*N)
      !>

  [out]

  IWORK

      !>          IWORK is INTEGER array, dimension (N)
      !>

  [out]

  INFO

      !>          INFO is INTEGER
      !>          = 0:  successful exit
      !>          < 0:  if INFO = -i, the i-th argument had an illegal value.
      !>                NaNs are illegal values for ANORM, and they propagate to
      !>                the output parameter RCOND.
      !>                Infinity is illegal for ANORM, and it propagates to the output
      !>                parameter RCOND as 0.
      !>          = 1:  if RCOND = NaN, or
      !>                   RCOND = Inf, or
      !>                   the computed norm of the inverse of A is 0.
      !>                In the latter, RCOND = 0 is returned.
      !>

Author
  Univ. of Tennessee
  Univ. of California Berkeley
  Univ. of Colorado Denver
  NAG Ltd.