LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
Loading...
Searching...
No Matches

◆ 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.