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Annotation of rpl/lapack/lapack/zpotri.f, revision 1.18

1.9       bertrand    1: *> \brief \b ZPOTRI
                      2: *
                      3: *  =========== DOCUMENTATION ===========
                      4: *
1.15      bertrand    5: * Online html documentation available at
                      6: *            http://www.netlib.org/lapack/explore-html/
1.9       bertrand    7: *
                      8: *> \htmlonly
1.15      bertrand    9: *> Download ZPOTRI + dependencies
                     10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zpotri.f">
                     11: *> [TGZ]</a>
                     12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zpotri.f">
                     13: *> [ZIP]</a>
                     14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zpotri.f">
1.9       bertrand   15: *> [TXT]</a>
1.15      bertrand   16: *> \endhtmlonly
1.9       bertrand   17: *
                     18: *  Definition:
                     19: *  ===========
                     20: *
                     21: *       SUBROUTINE ZPOTRI( UPLO, N, A, LDA, INFO )
1.15      bertrand   22: *
1.9       bertrand   23: *       .. Scalar Arguments ..
                     24: *       CHARACTER          UPLO
                     25: *       INTEGER            INFO, LDA, N
                     26: *       ..
                     27: *       .. Array Arguments ..
                     28: *       COMPLEX*16         A( LDA, * )
                     29: *       ..
1.15      bertrand   30: *
1.9       bertrand   31: *
                     32: *> \par Purpose:
                     33: *  =============
                     34: *>
                     35: *> \verbatim
                     36: *>
                     37: *> ZPOTRI computes the inverse of a complex Hermitian positive definite
                     38: *> matrix A using the Cholesky factorization A = U**H*U or A = L*L**H
                     39: *> computed by ZPOTRF.
                     40: *> \endverbatim
                     41: *
                     42: *  Arguments:
                     43: *  ==========
                     44: *
                     45: *> \param[in] UPLO
                     46: *> \verbatim
                     47: *>          UPLO is CHARACTER*1
                     48: *>          = 'U':  Upper triangle of A is stored;
                     49: *>          = 'L':  Lower triangle of A is stored.
                     50: *> \endverbatim
                     51: *>
                     52: *> \param[in] N
                     53: *> \verbatim
                     54: *>          N is INTEGER
                     55: *>          The order of the matrix A.  N >= 0.
                     56: *> \endverbatim
                     57: *>
                     58: *> \param[in,out] A
                     59: *> \verbatim
                     60: *>          A is COMPLEX*16 array, dimension (LDA,N)
                     61: *>          On entry, the triangular factor U or L from the Cholesky
                     62: *>          factorization A = U**H*U or A = L*L**H, as computed by
                     63: *>          ZPOTRF.
                     64: *>          On exit, the upper or lower triangle of the (Hermitian)
                     65: *>          inverse of A, overwriting the input factor U or L.
                     66: *> \endverbatim
                     67: *>
                     68: *> \param[in] LDA
                     69: *> \verbatim
                     70: *>          LDA is INTEGER
                     71: *>          The leading dimension of the array A.  LDA >= max(1,N).
                     72: *> \endverbatim
                     73: *>
                     74: *> \param[out] INFO
                     75: *> \verbatim
                     76: *>          INFO is INTEGER
                     77: *>          = 0:  successful exit
                     78: *>          < 0:  if INFO = -i, the i-th argument had an illegal value
                     79: *>          > 0:  if INFO = i, the (i,i) element of the factor U or L is
                     80: *>                zero, and the inverse could not be computed.
                     81: *> \endverbatim
                     82: *
                     83: *  Authors:
                     84: *  ========
                     85: *
1.15      bertrand   86: *> \author Univ. of Tennessee
                     87: *> \author Univ. of California Berkeley
                     88: *> \author Univ. of Colorado Denver
                     89: *> \author NAG Ltd.
1.9       bertrand   90: *
                     91: *> \ingroup complex16POcomputational
                     92: *
                     93: *  =====================================================================
1.1       bertrand   94:       SUBROUTINE ZPOTRI( UPLO, N, A, LDA, INFO )
                     95: *
1.18    ! bertrand   96: *  -- LAPACK computational routine --
1.1       bertrand   97: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
                     98: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
                     99: *
                    100: *     .. Scalar Arguments ..
                    101:       CHARACTER          UPLO
                    102:       INTEGER            INFO, LDA, N
                    103: *     ..
                    104: *     .. Array Arguments ..
                    105:       COMPLEX*16         A( LDA, * )
                    106: *     ..
                    107: *
                    108: *  =====================================================================
                    109: *
                    110: *     .. External Functions ..
                    111:       LOGICAL            LSAME
                    112:       EXTERNAL           LSAME
                    113: *     ..
                    114: *     .. External Subroutines ..
                    115:       EXTERNAL           XERBLA, ZLAUUM, ZTRTRI
                    116: *     ..
                    117: *     .. Intrinsic Functions ..
                    118:       INTRINSIC          MAX
                    119: *     ..
                    120: *     .. Executable Statements ..
                    121: *
                    122: *     Test the input parameters.
                    123: *
                    124:       INFO = 0
                    125:       IF( .NOT.LSAME( UPLO, 'U' ) .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
                    126:          INFO = -1
                    127:       ELSE IF( N.LT.0 ) THEN
                    128:          INFO = -2
                    129:       ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
                    130:          INFO = -4
                    131:       END IF
                    132:       IF( INFO.NE.0 ) THEN
                    133:          CALL XERBLA( 'ZPOTRI', -INFO )
                    134:          RETURN
                    135:       END IF
                    136: *
                    137: *     Quick return if possible
                    138: *
                    139:       IF( N.EQ.0 )
                    140:      $   RETURN
                    141: *
                    142: *     Invert the triangular Cholesky factor U or L.
                    143: *
                    144:       CALL ZTRTRI( UPLO, 'Non-unit', N, A, LDA, INFO )
                    145:       IF( INFO.GT.0 )
                    146:      $   RETURN
                    147: *
1.8       bertrand  148: *     Form inv(U) * inv(U)**H or inv(L)**H * inv(L).
1.1       bertrand  149: *
                    150:       CALL ZLAUUM( UPLO, N, A, LDA, INFO )
                    151: *
                    152:       RETURN
                    153: *
                    154: *     End of ZPOTRI
                    155: *
                    156:       END