1ZGETRI(1)                LAPACK routine (version 3.1)                ZGETRI(1)
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NAME

6       ZGETRI - the inverse of a matrix using the LU factorization computed by
7       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.
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22       This  method  inverts  U and then computes inv(A) by solving the system
23       inv(A)*L = inv(U) for inv(A).
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ARGUMENTS

27       N       (input) INTEGER
28               The order of the matrix A.  N >= 0.
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30       A       (input/output) COMPLEX*16 array, dimension (LDA,N)
31               On entry, the factors L and U from the factorization A =  P*L*U
32               as  computed  by  ZGETRF.  On exit, if INFO = 0, the inverse of
33               the original matrix A.
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35       LDA     (input) INTEGER
36               The leading dimension of the array A.  LDA >= max(1,N).
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38       IPIV    (input) INTEGER array, dimension (N)
39               The pivot indices from ZGETRF; for 1<=i<=N, row i of the matrix
40               was interchanged with row IPIV(i).
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42       WORK    (workspace/output) COMPLEX*16 array, dimension (MAX(1,LWORK))
43               On exit, if INFO=0, then WORK(1) returns the optimal LWORK.
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45       LWORK   (input) INTEGER
46               The dimension of the array WORK.  LWORK >= max(1,N).  For opti‐
47               mal performance LWORK >= N*NB, where NB is the  optimal  block‐
48               size returned by ILAENV.
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50               If  LWORK  = -1, then a workspace query is assumed; the routine
51               only calculates the optimal size of  the  WORK  array,  returns
52               this  value  as the first entry of the WORK array, and no error
53               message related to LWORK is issued by XERBLA.
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55       INFO    (output) INTEGER
56               = 0:  successful exit
57               < 0:  if INFO = -i, the i-th argument had an illegal value
58               > 0:  if INFO = i, U(i,i) is exactly zero; the matrix is singu‐
59               lar and its inverse could not be computed.
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63 LAPACK routine (version 3.1)    November 2006                       ZGETRI(1)
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