1DGETRI(1)                LAPACK routine (version 3.2)                DGETRI(1)
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NAME

6       DGETRI  -  computes  the inverse of a matrix using the LU factorization
7       computed by DGETRF
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SYNOPSIS

10       SUBROUTINE DGETRI( N, A, LDA, IPIV, WORK, LWORK, INFO )
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12           INTEGER        INFO, LDA, LWORK, N
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14           INTEGER        IPIV( * )
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16           DOUBLE         PRECISION A( LDA, * ), WORK( * )
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PURPOSE

19       DGETRI computes the inverse of a matrix using the LU factorization com‐
20       puted  by  DGETRF.   This  method inverts U and then computes inv(A) by
21       solving the system inv(A)*L = inv(U) for inv(A).
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ARGUMENTS

24       N       (input) INTEGER
25               The order of the matrix A.  N >= 0.
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27       A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
28               On entry, the factors L and U from the factorization A =  P*L*U
29               as  computed  by  DGETRF.  On exit, if INFO = 0, the inverse of
30               the original matrix A.
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32       LDA     (input) INTEGER
33               The leading dimension of the array A.  LDA >= max(1,N).
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35       IPIV    (input) INTEGER array, dimension (N)
36               The pivot indices from DGETRF; for 1<=i<=N, row i of the matrix
37               was interchanged with row IPIV(i).
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39       WORK       (workspace/output)   DOUBLE   PRECISION   array,   dimension
40       (MAX(1,LWORK))
41               On exit, if INFO=0, then WORK(1) returns the optimal LWORK.
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43       LWORK   (input) INTEGER
44               The dimension of the array WORK.  LWORK >= max(1,N).  For opti‐
45               mal  performance  LWORK >= N*NB, where NB is the optimal block‐
46               size returned by ILAENV.  If LWORK = -1, then a workspace query
47               is assumed; the routine only calculates the optimal size of the
48               WORK array, returns this value as the first entry of  the  WORK
49               array,  and  no  error  message  related  to LWORK is issued by
50               XERBLA.
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52       INFO    (output) INTEGER
53               = 0:  successful exit
54               < 0:  if INFO = -i, the i-th argument had an illegal value
55               > 0:  if INFO = i, U(i,i) is exactly zero; the matrix is singu‐
56               lar and its inverse could not be computed.
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60 LAPACK routine (version 3.2)    November 2008                       DGETRI(1)
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