# ?la_syrcond_x

Computes the infinity norm condition number of op(A)*diag(x) for symmetric indefinite matrices.

## Syntax

FORTRAN 77:

call cla_syrcond_x( uplo, n, a, lda, af, ldaf, ipiv, x, info, work, rwork )

call zla_syrcond_x( uplo, n, a, lda, af, ldaf, ipiv, x, info, work, rwork )

## Include Files

• Fortran: mkl.fi
• C: mkl.h

## Description

The function computes the infinity norm condition number of

`op(A) * diag(x)`

where the x is a COMPLEX vector for cla_syrcond_x and a DOUBLE COMPLEX vector for zla_syrcond_x.

## Input Parameters

uplo

CHARACTER*1. Must be 'U' or 'L'.

Specifies the triangle of A to store:

If `uplo = 'U'`, the upper triangle of A is stored,

If `uplo = 'L'`, the lower triangle of A is stored.

n

INTEGER. The number of linear equations, that is, the order of the matrix A; n 0.

a

COMPLEX for cla_syrcond_c

DOUBLE COMPLEX for zla_syrcond_c

Array, DIMENSION `(lda, *)`. On entry, the n-by-n matrix A. The second dimension of a must be at least `max(1,n)`.

lda

INTEGER. The leading dimension of the array a. lda `max(1,n)`.

af

COMPLEX for cla_syrcond_c

DOUBLE COMPLEX for zla_syrcond_c

Array, DIMENSION `(ldaf, *)`. The block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by ?sytrf. The second dimension of af must be at least `max(1,n)`.

ldaf

INTEGER. The leading dimension of the array af. ldaf `max(1,n)`.

ipiv

INTEGER.

Array with DIMENSION n. Details of the interchanges and the block structure of D as determined by ?sytrf.

x

COMPLEX for cla_syrcond_c

DOUBLE COMPLEX for zla_syrcond_c

Array x with DIMENSION n. The vector x in the formula

`op(A) * inv(diag(x))`.

work

COMPLEX for cla_syrcond_c

DOUBLE COMPLEX for zla_syrcond_c

Array DIMENSION 2*n. Workspace.

rwork

REAL for cla_syrcond_c

DOUBLE PRECISION for zla_syrcond_c

Array DIMENSION n. Workspace.

## Output Parameters

info

INTEGER.

If info = 0, the execution is successful.

If i > 0, the i-th parameter is invalid.