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NAME
     dgetri - compute the inverse of a matrix using the  LU  fac-
     torization computed by DGETRF

SYNOPSIS
     SUBROUTINE DGETRI( N, A, LDA, IPIV, WORK, LWORK, INFO )

     INTEGER INFO, LDA, LWORK, N

     INTEGER IPIV( * )

     DOUBLE PRECISION A( LDA, * ), WORK( LWORK )



     #include <sunperf.h>

     void dgetri(int n, double *da, int  lda,  int  *ipivot,  int
               *info) ;

PURPOSE
     DGETRI computes the inverse of a matrix using the LU factor-
     ization computed by DGETRF.

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


ARGUMENTS
     N         (input) INTEGER
               The order of the matrix A.  N >= 0.

     A         (input/output) DOUBLE PRECISION  array,  dimension
               (LDA,N)
               On entry, the factors L and U from the  factoriza-
               tion A = P*L*U as computed by DGETRF.  On exit, if
               INFO = 0, the inverse of the original matrix A.

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

     IPIV      (input) 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      (workspace/output) DOUBLE PRECISION array,  dimen-
               sion (LWORK)
               On exit,  if  INFO=0,  then  WORK(1)  returns  the
               optimal LWORK.

     LWORK     (input) 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.

     INFO      (output) INTEGER
               = 0:  successful exit
               < 0:  if INFO = -i, the i-th argument had an ille-
               gal value
               > 0:  if INFO = i, U(i,i)  is  exactly  zero;  the
               matrix  is  singular  and its inverse could not be
               computed.

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