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Annotation of rpl/lapack/lapack/dpotri.f, revision 1.9

1.9     ! bertrand    1: *> \brief \b DPOTRI
        !             2: *
        !             3: *  =========== DOCUMENTATION ===========
        !             4: *
        !             5: * Online html documentation available at 
        !             6: *            http://www.netlib.org/lapack/explore-html/ 
        !             7: *
        !             8: *> \htmlonly
        !             9: *> Download DPOTRI + dependencies 
        !            10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dpotri.f"> 
        !            11: *> [TGZ]</a> 
        !            12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dpotri.f"> 
        !            13: *> [ZIP]</a> 
        !            14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dpotri.f"> 
        !            15: *> [TXT]</a>
        !            16: *> \endhtmlonly 
        !            17: *
        !            18: *  Definition:
        !            19: *  ===========
        !            20: *
        !            21: *       SUBROUTINE DPOTRI( UPLO, N, A, LDA, INFO )
        !            22: * 
        !            23: *       .. Scalar Arguments ..
        !            24: *       CHARACTER          UPLO
        !            25: *       INTEGER            INFO, LDA, N
        !            26: *       ..
        !            27: *       .. Array Arguments ..
        !            28: *       DOUBLE PRECISION   A( LDA, * )
        !            29: *       ..
        !            30: *  
        !            31: *
        !            32: *> \par Purpose:
        !            33: *  =============
        !            34: *>
        !            35: *> \verbatim
        !            36: *>
        !            37: *> DPOTRI computes the inverse of a real symmetric positive definite
        !            38: *> matrix A using the Cholesky factorization A = U**T*U or A = L*L**T
        !            39: *> computed by DPOTRF.
        !            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 DOUBLE PRECISION array, dimension (LDA,N)
        !            61: *>          On entry, the triangular factor U or L from the Cholesky
        !            62: *>          factorization A = U**T*U or A = L*L**T, as computed by
        !            63: *>          DPOTRF.
        !            64: *>          On exit, the upper or lower triangle of the (symmetric)
        !            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: *
        !            86: *> \author Univ. of Tennessee 
        !            87: *> \author Univ. of California Berkeley 
        !            88: *> \author Univ. of Colorado Denver 
        !            89: *> \author NAG Ltd. 
        !            90: *
        !            91: *> \date November 2011
        !            92: *
        !            93: *> \ingroup doublePOcomputational
        !            94: *
        !            95: *  =====================================================================
1.1       bertrand   96:       SUBROUTINE DPOTRI( UPLO, N, A, LDA, INFO )
                     97: *
1.9     ! bertrand   98: *  -- LAPACK computational routine (version 3.4.0) --
1.1       bertrand   99: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
                    100: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.9     ! bertrand  101: *     November 2011
1.1       bertrand  102: *
                    103: *     .. Scalar Arguments ..
                    104:       CHARACTER          UPLO
                    105:       INTEGER            INFO, LDA, N
                    106: *     ..
                    107: *     .. Array Arguments ..
                    108:       DOUBLE PRECISION   A( LDA, * )
                    109: *     ..
                    110: *
                    111: *  =====================================================================
                    112: *
                    113: *     .. External Functions ..
                    114:       LOGICAL            LSAME
                    115:       EXTERNAL           LSAME
                    116: *     ..
                    117: *     .. External Subroutines ..
                    118:       EXTERNAL           DLAUUM, DTRTRI, XERBLA
                    119: *     ..
                    120: *     .. Intrinsic Functions ..
                    121:       INTRINSIC          MAX
                    122: *     ..
                    123: *     .. Executable Statements ..
                    124: *
                    125: *     Test the input parameters.
                    126: *
                    127:       INFO = 0
                    128:       IF( .NOT.LSAME( UPLO, 'U' ) .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
                    129:          INFO = -1
                    130:       ELSE IF( N.LT.0 ) THEN
                    131:          INFO = -2
                    132:       ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
                    133:          INFO = -4
                    134:       END IF
                    135:       IF( INFO.NE.0 ) THEN
                    136:          CALL XERBLA( 'DPOTRI', -INFO )
                    137:          RETURN
                    138:       END IF
                    139: *
                    140: *     Quick return if possible
                    141: *
                    142:       IF( N.EQ.0 )
                    143:      $   RETURN
                    144: *
                    145: *     Invert the triangular Cholesky factor U or L.
                    146: *
                    147:       CALL DTRTRI( UPLO, 'Non-unit', N, A, LDA, INFO )
                    148:       IF( INFO.GT.0 )
                    149:      $   RETURN
                    150: *
1.8       bertrand  151: *     Form inv(U) * inv(U)**T or inv(L)**T * inv(L).
1.1       bertrand  152: *
                    153:       CALL DLAUUM( UPLO, N, A, LDA, INFO )
                    154: *
                    155:       RETURN
                    156: *
                    157: *     End of DPOTRI
                    158: *
                    159:       END