# DGETRI (3) - Linux Manuals

dgetri.f -

## SYNOPSIS

### Functions/Subroutines

subroutine dgetri (N, A, LDA, IPIV, WORK, LWORK, INFO)
DGETRI

## Function/Subroutine Documentation

### subroutine dgetri (integerN, double precision, dimension( lda, * )A, integerLDA, integer, dimension( * )IPIV, double precision, dimension( * )WORK, integerLWORK, integerINFO)

DGETRI

Purpose:

``` DGETRI computes the inverse of a matrix using the LU factorization
computed by DGETRF.

This method inverts U and then computes inv(A) by solving the system
inv(A)*L = inv(U) for inv(A).
```

Parameters:

N

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

A

```          A is DOUBLE PRECISION array, dimension (LDA,N)
On entry, the factors L and U from the factorization
A = P*L*U as computed by DGETRF.
On exit, if INFO = 0, the inverse of the original matrix A.
```

LDA

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

IPIV

```          IPIV is INTEGER array, dimension (N)
The pivot indices from DGETRF; for 1<=i<=N, row i of the
matrix was interchanged with row IPIV(i).
```

WORK

```          WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))
On exit, if INFO=0, then WORK(1) returns the optimal LWORK.
```

LWORK

```          LWORK is INTEGER
The dimension of the array WORK.  LWORK >= max(1,N).
For optimal performance LWORK >= N*NB, where NB is
the optimal blocksize returned by ILAENV.

If LWORK = -1, then a workspace query is assumed; the routine
only 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 LWORK 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, U(i,i) is exactly zero; the matrix is
singular and its inverse could not be computed.
```

Author:

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:

November 2011

Definition at line 115 of file dgetri.f.

## Author

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