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man pages->IRIX man pages -> complib/zsytri (3)
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### Contents

```
ZSYTRI(3F)							    ZSYTRI(3F)

```

### NAME[Toc][Back]

```     ZSYTRI - compute the inverse of a complex symmetric indefinite matrix A
using the factorization A = U*D*U**T or A = L*D*L**T computed by ZSYTRF
```

### SYNOPSIS[Toc][Back]

```     SUBROUTINE	ZSYTRI(	UPLO, N, A, LDA, IPIV, WORK, INFO )

CHARACTER	UPLO

INTEGER	INFO, LDA, N

INTEGER	IPIV( *	)

COMPLEX*16	A( LDA,	* ), WORK( * )
```

### PURPOSE[Toc][Back]

```     ZSYTRI computes the inverse of a complex symmetric	indefinite matrix A
using the factorization A = U*D*U**T or A = L*D*L**T computed by ZSYTRF.

```

### ARGUMENTS[Toc][Back]

```     UPLO    (input) CHARACTER*1
Specifies whether the details of the factorization	are stored as
an	upper or lower triangular matrix.  = 'U':  Upper triangular,
form is A = U*D*U**T;
= 'L':  Lower triangular, form is A = L*D*L**T.

N	     (input) INTEGER
The order of the matrix A.	 N >= 0.

A	     (input/output) COMPLEX*16 array, dimension	(LDA,N)
On	entry, the block diagonal matrix D and the multipliers used to
obtain the	factor U or L as computed by ZSYTRF.

On	exit, if INFO =	0, the (symmetric) inverse of the original
matrix.  If UPLO =	'U', the upper triangular part of the inverse
is	formed and the part of A below the diagonal is not referenced;
if	UPLO = 'L' the lower triangular	part of	the inverse is formed
and the part of A above the diagonal is not referenced.

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

IPIV    (input) INTEGER array, dimension (N)
Details of	the interchanges and the block structure of D as
determined	by ZSYTRF.

WORK    (workspace) COMPLEX*16 array, dimension (2*N)

INFO    (output) INTEGER
= 0: successful exit
< 0: if INFO = -i,	the i-th argument had an illegal value

Page 1

ZSYTRI(3F)							    ZSYTRI(3F)

> 0: if INFO = i, D(i,i) =	0; the matrix is singular and its
inverse could not be computed.
ZSYTRI(3F)							    ZSYTRI(3F)

```

### NAME[Toc][Back]

```     ZSYTRI - compute the inverse of a complex symmetric indefinite matrix A
using the factorization A = U*D*U**T or A = L*D*L**T computed by ZSYTRF
```

### SYNOPSIS[Toc][Back]

```     SUBROUTINE	ZSYTRI(	UPLO, N, A, LDA, IPIV, WORK, INFO )

CHARACTER	UPLO

INTEGER	INFO, LDA, N

INTEGER	IPIV( *	)

COMPLEX*16	A( LDA,	* ), WORK( * )
```

### PURPOSE[Toc][Back]

```     ZSYTRI computes the inverse of a complex symmetric	indefinite matrix A
using the factorization A = U*D*U**T or A = L*D*L**T computed by ZSYTRF.

```

### ARGUMENTS[Toc][Back]

```     UPLO    (input) CHARACTER*1
Specifies whether the details of the factorization	are stored as
an	upper or lower triangular matrix.  = 'U':  Upper triangular,
form is A = U*D*U**T;
= 'L':  Lower triangular, form is A = L*D*L**T.

N	     (input) INTEGER
The order of the matrix A.	 N >= 0.

A	     (input/output) COMPLEX*16 array, dimension	(LDA,N)
On	entry, the block diagonal matrix D and the multipliers used to
obtain the	factor U or L as computed by ZSYTRF.

On	exit, if INFO =	0, the (symmetric) inverse of the original
matrix.  If UPLO =	'U', the upper triangular part of the inverse
is	formed and the part of A below the diagonal is not referenced;
if	UPLO = 'L' the lower triangular	part of	the inverse is formed
and the part of A above the diagonal is not referenced.

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

IPIV    (input) INTEGER array, dimension (N)
Details of	the interchanges and the block structure of D as
determined	by ZSYTRF.

WORK    (workspace) COMPLEX*16 array, dimension (2*N)

INFO    (output) INTEGER
= 0: successful exit
< 0: if INFO = -i,	the i-th argument had an illegal value

Page 1

ZSYTRI(3F)							    ZSYTRI(3F)

> 0: if INFO = i, D(i,i) =	0; the matrix is singular and its
inverse could not be computed.

PPPPaaaaggggeeee 2222```
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