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Annotation of rpl/lapack/lapack/dpotri.f, revision 1.1

1.1     ! bertrand    1:       SUBROUTINE DPOTRI( UPLO, N, A, LDA, INFO )
        !             2: *
        !             3: *  -- LAPACK routine (version 3.2) --
        !             4: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
        !             5: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
        !             6: *     November 2006
        !             7: *
        !             8: *     .. Scalar Arguments ..
        !             9:       CHARACTER          UPLO
        !            10:       INTEGER            INFO, LDA, N
        !            11: *     ..
        !            12: *     .. Array Arguments ..
        !            13:       DOUBLE PRECISION   A( LDA, * )
        !            14: *     ..
        !            15: *
        !            16: *  Purpose
        !            17: *  =======
        !            18: *
        !            19: *  DPOTRI computes the inverse of a real symmetric positive definite
        !            20: *  matrix A using the Cholesky factorization A = U**T*U or A = L*L**T
        !            21: *  computed by DPOTRF.
        !            22: *
        !            23: *  Arguments
        !            24: *  =========
        !            25: *
        !            26: *  UPLO    (input) CHARACTER*1
        !            27: *          = 'U':  Upper triangle of A is stored;
        !            28: *          = 'L':  Lower triangle of A is stored.
        !            29: *
        !            30: *  N       (input) INTEGER
        !            31: *          The order of the matrix A.  N >= 0.
        !            32: *
        !            33: *  A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
        !            34: *          On entry, the triangular factor U or L from the Cholesky
        !            35: *          factorization A = U**T*U or A = L*L**T, as computed by
        !            36: *          DPOTRF.
        !            37: *          On exit, the upper or lower triangle of the (symmetric)
        !            38: *          inverse of A, overwriting the input factor U or L.
        !            39: *
        !            40: *  LDA     (input) INTEGER
        !            41: *          The leading dimension of the array A.  LDA >= max(1,N).
        !            42: *
        !            43: *  INFO    (output) INTEGER
        !            44: *          = 0:  successful exit
        !            45: *          < 0:  if INFO = -i, the i-th argument had an illegal value
        !            46: *          > 0:  if INFO = i, the (i,i) element of the factor U or L is
        !            47: *                zero, and the inverse could not be computed.
        !            48: *
        !            49: *  =====================================================================
        !            50: *
        !            51: *     .. External Functions ..
        !            52:       LOGICAL            LSAME
        !            53:       EXTERNAL           LSAME
        !            54: *     ..
        !            55: *     .. External Subroutines ..
        !            56:       EXTERNAL           DLAUUM, DTRTRI, XERBLA
        !            57: *     ..
        !            58: *     .. Intrinsic Functions ..
        !            59:       INTRINSIC          MAX
        !            60: *     ..
        !            61: *     .. Executable Statements ..
        !            62: *
        !            63: *     Test the input parameters.
        !            64: *
        !            65:       INFO = 0
        !            66:       IF( .NOT.LSAME( UPLO, 'U' ) .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
        !            67:          INFO = -1
        !            68:       ELSE IF( N.LT.0 ) THEN
        !            69:          INFO = -2
        !            70:       ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
        !            71:          INFO = -4
        !            72:       END IF
        !            73:       IF( INFO.NE.0 ) THEN
        !            74:          CALL XERBLA( 'DPOTRI', -INFO )
        !            75:          RETURN
        !            76:       END IF
        !            77: *
        !            78: *     Quick return if possible
        !            79: *
        !            80:       IF( N.EQ.0 )
        !            81:      $   RETURN
        !            82: *
        !            83: *     Invert the triangular Cholesky factor U or L.
        !            84: *
        !            85:       CALL DTRTRI( UPLO, 'Non-unit', N, A, LDA, INFO )
        !            86:       IF( INFO.GT.0 )
        !            87:      $   RETURN
        !            88: *
        !            89: *     Form inv(U)*inv(U)' or inv(L)'*inv(L).
        !            90: *
        !            91:       CALL DLAUUM( UPLO, N, A, LDA, INFO )
        !            92: *
        !            93:       RETURN
        !            94: *
        !            95: *     End of DPOTRI
        !            96: *
        !            97:       END