---
name: "csytri"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/csytri/3lapack"
---

# csytri(3lapack)

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 CSYTRF

## NAME

CSYTRI - 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 CSYTRF

## SYNOPSIS

- SUBROUTINE CSYTRI(

  UPLO, N, A, LDA, IPIV, WORK, INFO )

- CHARACTER

  UPLO

- INTEGER

  INFO, LDA, N

- INTEGER

  IPIV( \* )

- COMPLEX

  A( LDA, \* ), WORK( \* )

## PURPOSE

CSYTRI 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 CSYTRF.

## ARGUMENTS

- 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 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 CSYTRF. 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 CSYTRF.

- WORK (workspace) COMPLEX array, dimension (2\*N)

  - INFO (output) 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.