# sla_porpvgrw.f man page

sla_porpvgrw.f —

## Synopsis

### Functions/Subroutines

REAL functionsla_porpvgrw(UPLO, NCOLS, A, LDA, AF, LDAF, WORK)SLA_PORPVGRWcomputes the reciprocal pivot growth factor norm(A)/norm(U) for a symmetric or Hermitian positive-definite matrix.

## Function/Subroutine Documentation

### REAL function sla_porpvgrw (character*1UPLO, integerNCOLS, real, dimension( lda, * )A, integerLDA, real, dimension( ldaf, * )AF, integerLDAF, real, dimension( * )WORK)

**SLA_PORPVGRW** computes the reciprocal pivot growth factor norm(A)/norm(U) for a symmetric or Hermitian positive-definite matrix.

**Purpose:**

```
SLA_PORPVGRW computes the reciprocal pivot growth factor
norm(A)/norm(U). The "max absolute element" norm is used. If this is
much less than 1, the stability of the LU factorization of the
(equilibrated) matrix A could be poor. This also means that the
solution X, estimated condition numbers, and error bounds could be
unreliable.
```

**Parameters:**

*UPLO*

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

*NCOLS*

```
NCOLS is INTEGER
The number of columns of the matrix A. NCOLS >= 0.
```

*A*

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

*LDA*

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

*AF*

```
AF is REAL array, dimension (LDAF,N)
The triangular factor U or L from the Cholesky factorization
A = U**T*U or A = L*L**T, as computed by SPOTRF.
```

*LDAF*

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

*WORK*

`WORK is REAL array, dimension (2*N)`

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

September 2012

Definition at line 105 of file sla_porpvgrw.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

sla_porpvgrw(3) is an alias of sla_porpvgrw.f(3).