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    1:       SUBROUTINE ZHETRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO )
    2: *
    3: *  -- LAPACK routine (version 3.3.1) --
    4: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
    5: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
    6: *  -- April 2011                                                      --
    7: *
    8: *  -- Written by Julie Langou of the Univ. of TN    --
    9: *
   10: * @precisions normal z -> c
   11: *
   12: *     .. Scalar Arguments ..
   13:       CHARACTER          UPLO
   14:       INTEGER            INFO, LDA, LWORK, N
   15: *     ..
   16: *     .. Array Arguments ..
   17:       INTEGER            IPIV( * )
   18:       COMPLEX*16         A( LDA, * ), WORK( * )
   19: *     ..
   20: *
   21: *  Purpose
   22: *  =======
   23: *
   24: *  ZHETRI2 computes the inverse of a COMPLEX*16 hermitian indefinite matrix
   25: *  A using the factorization A = U*D*U**T or A = L*D*L**T computed by
   26: *  ZHETRF. ZHETRI2 set the LEADING DIMENSION of the workspace
   27: *  before calling ZHETRI2X that actually computes the inverse.
   28: *
   29: *  Arguments
   30: *  =========
   31: *
   32: *  UPLO    (input) CHARACTER*1
   33: *          Specifies whether the details of the factorization are stored
   34: *          as an upper or lower triangular matrix.
   35: *          = 'U':  Upper triangular, form is A = U*D*U**T;
   36: *          = 'L':  Lower triangular, form is A = L*D*L**T.
   37: *
   38: *  N       (input) INTEGER
   39: *          The order of the matrix A.  N >= 0.
   40: *
   41: *  A       (input/output) COMPLEX*16 array, dimension (LDA,N)
   42: *          On entry, the NB diagonal matrix D and the multipliers
   43: *          used to obtain the factor U or L as computed by ZHETRF.
   44: *
   45: *          On exit, if INFO = 0, the (symmetric) inverse of the original
   46: *          matrix.  If UPLO = 'U', the upper triangular part of the
   47: *          inverse is formed and the part of A below the diagonal is not
   48: *          referenced; if UPLO = 'L' the lower triangular part of the
   49: *          inverse is formed and the part of A above the diagonal is
   50: *          not referenced.
   51: *
   52: *  LDA     (input) INTEGER
   53: *          The leading dimension of the array A.  LDA >= max(1,N).
   54: *
   55: *  IPIV    (input) INTEGER array, dimension (N)
   56: *          Details of the interchanges and the NB structure of D
   57: *          as determined by ZHETRF.
   58: *
   59: *  WORK    (workspace) COMPLEX*16 array, dimension (N+NB+1)*(NB+3)
   60: *
   61: *  LWORK   (input) INTEGER
   62: *          The dimension of the array WORK.
   63: *          WORK is size >= (N+NB+1)*(NB+3)
   64: *          If LDWORK = -1, then a workspace query is assumed; the routine
   65: *           calculates:
   66: *              - the optimal size of the WORK array, returns
   67: *          this value as the first entry of the WORK array,
   68: *              - and no error message related to LDWORK is issued by XERBLA.
   69: *
   70: *  INFO    (output) INTEGER
   71: *          = 0: successful exit
   72: *          < 0: if INFO = -i, the i-th argument had an illegal value
   73: *          > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its
   74: *               inverse could not be computed.
   75: *
   76: *  =====================================================================
   77: *
   78: *     .. Local Scalars ..
   79:       LOGICAL            UPPER, LQUERY
   80:       INTEGER            MINSIZE, NBMAX
   81: *     ..
   82: *     .. External Functions ..
   83:       LOGICAL            LSAME
   84:       INTEGER            ILAENV
   85:       EXTERNAL           LSAME, ILAENV
   86: *     ..
   87: *     .. External Subroutines ..
   88:       EXTERNAL           ZHETRI2X
   89: *     ..
   90: *     .. Executable Statements ..
   91: *
   92: *     Test the input parameters.
   93: *
   94:       INFO = 0
   95:       UPPER = LSAME( UPLO, 'U' )
   96:       LQUERY = ( LWORK.EQ.-1 )
   97: *     Get blocksize
   98:       NBMAX = ILAENV( 1, 'ZHETRF', UPLO, N, -1, -1, -1 )
   99:       IF ( NBMAX .GE. N ) THEN
  100:          MINSIZE = N
  101:       ELSE
  102:          MINSIZE = (N+NBMAX+1)*(NBMAX+3)
  103:       END IF
  104: *
  105:       IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
  106:          INFO = -1
  107:       ELSE IF( N.LT.0 ) THEN
  108:          INFO = -2
  109:       ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
  110:          INFO = -4
  111:       ELSE IF (LWORK .LT. MINSIZE .AND. .NOT.LQUERY ) THEN
  112:          INFO = -7
  113:       END IF
  114: *
  115: *     Quick return if possible
  116: *
  117: *
  118:       IF( INFO.NE.0 ) THEN
  119:          CALL XERBLA( 'ZHETRI2', -INFO )
  120:          RETURN
  121:       ELSE IF( LQUERY ) THEN
  122:          WORK(1)=MINSIZE
  123:          RETURN
  124:       END IF
  125:       IF( N.EQ.0 )
  126:      $   RETURN
  127:       
  128:       IF( NBMAX .GE. N ) THEN
  129:          CALL ZHETRI( UPLO, N, A, LDA, IPIV, WORK, INFO )
  130:       ELSE
  131:          CALL ZHETRI2X( UPLO, N, A, LDA, IPIV, WORK, NBMAX, INFO )
  132:       END IF
  133:       RETURN
  134: *
  135: *     End of ZHETRI2
  136: *
  137:       END