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

6       ZGETRI  -  computes  the inverse of a matrix using the LU factorization
7       computed by ZGETRF
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SYNOPSIS

10       SUBROUTINE ZGETRI( 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           COMPLEX*16     A( LDA, * ), WORK( * )
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PURPOSE

19       ZGETRI computes the inverse of a matrix using the LU factorization com‐
20       puted  by  ZGETRF.   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) COMPLEX*16 array, dimension (LDA,N)
28               On entry, the factors L and U from the factorization A =  P*L*U
29               as  computed  by  ZGETRF.  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 ZGETRF; for 1<=i<=N, row i of the matrix
37               was interchanged with row IPIV(i).
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39       WORK    (workspace/output) COMPLEX*16 array, dimension (MAX(1,LWORK))
40               On exit, if INFO=0, then WORK(1) returns the optimal LWORK.
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42       LWORK   (input) INTEGER
43               The dimension of the array WORK.  LWORK >= max(1,N).  For opti‐
44               mal performance LWORK >= N*NB, where NB is the  optimal  block‐
45               size returned by ILAENV.  If LWORK = -1, then a workspace query
46               is assumed; the routine only calculates the optimal size of the
47               WORK  array,  returns this value as the first entry of the WORK
48               array, and no error message  related  to  LWORK  is  issued  by
49               XERBLA.
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51       INFO    (output) INTEGER
52               = 0:  successful exit
53               < 0:  if INFO = -i, the i-th argument had an illegal value
54               > 0:  if INFO = i, U(i,i) is exactly zero; the matrix is singu‐
55               lar and its inverse could not be computed.
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59 LAPACK routine (version 3.2)    November 2008                       ZGETRI(1)
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