---
name: "zsytri2.f"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/zsytri2.f"
---

# zsytri2.f(3)

## NAME

SRC/zsytri2.f

## SYNOPSIS

### Functions/Subroutines

subroutine **zsytri2** (uplo, n, a, lda, ipiv, work, lwork, info)\
 **ZSYTRI2**

## Function/Subroutine Documentation

### subroutine zsytri2 (character uplo, integer n, complex\*16, dimension( lda, \* ) a, integer lda, integer, dimension( \* ) ipiv, complex\*16, dimension( \* ) work, integer lwork, integer info)

**ZSYTRI2**

**Purpose:**

```
!>
!> ZSYTRI2 computes the inverse of a COMPLEX*16 symmetric indefinite matrix
!> A using the factorization A = U*D*U**T or A = L*D*L**T computed by
!> ZSYTRF. ZSYTRI2 sets the LEADING DIMENSION of the workspace
!> before calling ZSYTRI2X that actually computes the inverse.
!>
```

**Parameters**

*UPLO*

```
!>          UPLO is 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*

```
!>          N is INTEGER
!>          The order of the matrix A.  N >= 0.
!>
```

*A*

```
!>          A is 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*

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

*IPIV*

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

*WORK*

```
!>          WORK is COMPLEX*16 array, dimension (N+NB+1)*(NB+3)
!>
```

*LWORK*

```
!>          LWORK is INTEGER
!>          The dimension of the array WORK.
!>          WORK is size >= (N+NB+1)*(NB+3)
!>          If LDWORK = -1, then a workspace query is assumed; the routine
!>           calculates:
!>              - the optimal size of the WORK array, returns
!>          this value as the first entry of the WORK array,
!>              - and no error message related to LDWORK is issued by XERBLA.
!>
```

*INFO*

```
!>          INFO is INTEGER
!>          = 0: successful exit
!>          < 0: if INFO = -i, the i-th argument had an illegal value
!>          > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its
!>               inverse could not be computed.
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **126** of file **zsytri2.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.