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## sla_syrcond()

real function sla_syrcond | ( | character | uplo,
|  | integer | n,
|  | real, dimension( lda, * ) | a,
|  | integer | lda,
|  | real, dimension( ldaf, * ) | af,
|  | integer | ldaf,
|  | integer, dimension( * ) | ipiv,
|  | integer | cmode,
|  | real, dimension( * ) | c,
|  | integer | info,
|  | real, dimension( * ) | work,
|  | integer, dimension( * ) | iwork )

SLA_SYRCOND estimates the Skeel condition number for a symmetric indefinite matrix.

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

Purpose:

      !>
      !>    SLA_SYRCOND estimates the Skeel condition number of  op(A) * op2(C)
      !>    where op2 is determined by CMODE as follows
      !>    CMODE =  1    op2(C) = C
      !>    CMODE =  0    op2(C) = I
      !>    CMODE = -1    op2(C) = inv(C)
      !>    The Skeel condition number cond(A) = norminf( |inv(A)||A| )
      !>    is computed by computing scaling factors R such that
      !>    diag(R)*A*op2(C) is row equilibrated and computing the standard
      !>    infinity-norm condition number.
      !>

Parameters

  [in]

  UPLO

      !>          UPLO is CHARACTER*1
      !>       = 'U':  Upper triangle of A is stored;
      !>       = 'L':  Lower triangle of A is stored.
      !>

  [in]

  N

      !>          N is INTEGER
      !>     The number of linear equations, i.e., the order of the
      !>     matrix A.  N >= 0.
      !>

  [in]

  A

      !>          A is REAL array, dimension (LDA,N)
      !>     On entry, the N-by-N matrix A.
      !>

  [in]

  LDA

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

  [in]

  AF

      !>          AF is REAL array, dimension (LDAF,N)
      !>     The block diagonal matrix D and the multipliers used to
      !>     obtain the factor U or L as computed by SSYTRF.
      !>

  [in]

  LDAF

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

  [in]

  IPIV

      !>          IPIV is INTEGER array, dimension (N)
      !>     Details of the interchanges and the block structure of D
      !>     as determined by SSYTRF.
      !>

  [in]

  CMODE

      !>          CMODE is INTEGER
      !>     Determines op2(C) in the formula op(A) * op2(C) as follows:
      !>     CMODE =  1    op2(C) = C
      !>     CMODE =  0    op2(C) = I
      !>     CMODE = -1    op2(C) = inv(C)
      !>

  [in]

  C

      !>          C is REAL array, dimension (N)
      !>     The vector C in the formula op(A) * op2(C).
      !>

  [out]

  INFO

      !>          INFO is INTEGER
      !>       = 0:  Successful exit.
      !>     i > 0:  The ith argument is invalid.
      !>

  [out]

  WORK

      !>          WORK is REAL array, dimension (3*N).
      !>     Workspace.
      !>

  [out]

  IWORK

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

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