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Annotation of rpl/lapack/lapack/dsytri2.f, revision 1.1

1.1     ! bertrand    1:       SUBROUTINE DSYTRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO )
        !             2: *
        !             3: *  -- LAPACK routine (version 3.3.0) --
        !             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 2010
        !             7: *
        !             8: *  -- Written by Julie Langou of the Univ. of TN    --
        !             9: *
        !            10: *     .. Scalar Arguments ..
        !            11:       CHARACTER          UPLO
        !            12:       INTEGER            INFO, LDA, LWORK, N
        !            13: *     ..
        !            14: *     .. Array Arguments ..
        !            15:       INTEGER            IPIV( * )
        !            16:       DOUBLE PRECISION   A( LDA, * ), WORK( * )
        !            17: *     ..
        !            18: *
        !            19: *  Purpose
        !            20: *  =======
        !            21: *
        !            22: *  DSYTRI2 computes the inverse of a real symmetric indefinite matrix
        !            23: *  A using the factorization A = U*D*U**T or A = L*D*L**T computed by
        !            24: *  DSYTRF. DSYTRI2 sets the LEADING DIMENSION of the workspace
        !            25: *  before calling DSYTRI2X that actually computes the inverse.
        !            26: *
        !            27: *  Arguments
        !            28: *  =========
        !            29: *
        !            30: *  UPLO    (input) CHARACTER*1
        !            31: *          Specifies whether the details of the factorization are stored
        !            32: *          as an upper or lower triangular matrix.
        !            33: *          = 'U':  Upper triangular, form is A = U*D*U**T;
        !            34: *          = 'L':  Lower triangular, form is A = L*D*L**T.
        !            35: *
        !            36: *  N       (input) INTEGER
        !            37: *          The order of the matrix A.  N >= 0.
        !            38: *
        !            39: *  A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
        !            40: *          On entry, the NB diagonal matrix D and the multipliers
        !            41: *          used to obtain the factor U or L as computed by DSYTRF.
        !            42: *
        !            43: *          On exit, if INFO = 0, the (symmetric) inverse of the original
        !            44: *          matrix.  If UPLO = 'U', the upper triangular part of the
        !            45: *          inverse is formed and the part of A below the diagonal is not
        !            46: *          referenced; if UPLO = 'L' the lower triangular part of the
        !            47: *          inverse is formed and the part of A above the diagonal is
        !            48: *          not referenced.
        !            49: *
        !            50: *  LDA     (input) INTEGER
        !            51: *          The leading dimension of the array A.  LDA >= max(1,N).
        !            52: *
        !            53: *  IPIV    (input) INTEGER array, dimension (N)
        !            54: *          Details of the interchanges and the NB structure of D
        !            55: *          as determined by DSYTRF.
        !            56: *
        !            57: *  WORK    (workspace) DOUBLE PRECISION array, dimension (N+NB+1)*(NB+3)
        !            58: *
        !            59: *  LWORK   (input) INTEGER
        !            60: *          The dimension of the array WORK.
        !            61: *          WORK is size >= (N+NB+1)*(NB+3)
        !            62: *          If LDWORK = -1, then a workspace query is assumed; the routine
        !            63: *           calculates:
        !            64: *              - the optimal size of the WORK array, returns
        !            65: *          this value as the first entry of the WORK array,
        !            66: *              - and no error message related to LDWORK is issued by XERBLA.
        !            67: *
        !            68: *  INFO    (output) INTEGER
        !            69: *          = 0: successful exit
        !            70: *          < 0: if INFO = -i, the i-th argument had an illegal value
        !            71: *          > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its
        !            72: *               inverse could not be computed.
        !            73: *
        !            74: *  =====================================================================
        !            75: *
        !            76: *     .. Local Scalars ..
        !            77:       LOGICAL            UPPER, LQUERY
        !            78:       INTEGER            MINSIZE, NBMAX
        !            79: *     ..
        !            80: *     .. External Functions ..
        !            81:       LOGICAL            LSAME
        !            82:       INTEGER            ILAENV
        !            83:       EXTERNAL           LSAME, ILAENV
        !            84: *     ..
        !            85: *     .. External Subroutines ..
        !            86:       EXTERNAL           DSYTRI2X
        !            87: *     ..
        !            88: *     .. Executable Statements ..
        !            89: *
        !            90: *     Test the input parameters.
        !            91: *
        !            92:       INFO = 0
        !            93:       UPPER = LSAME( UPLO, 'U' )
        !            94:       LQUERY = ( LWORK.EQ.-1 )
        !            95: *     Get blocksize
        !            96:       NBMAX = ILAENV( 1, 'DSYTRF', UPLO, N, -1, -1, -1 )
        !            97:       MINSIZE = (N+NBMAX+1)*(NBMAX+3)
        !            98: *
        !            99:       IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
        !           100:          INFO = -1
        !           101:       ELSE IF( N.LT.0 ) THEN
        !           102:          INFO = -2
        !           103:       ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
        !           104:          INFO = -4
        !           105:       ELSE IF (LWORK .LT. MINSIZE .AND. .NOT.LQUERY ) THEN
        !           106:          INFO = -7
        !           107:       END IF
        !           108: *
        !           109: *     Quick return if possible
        !           110: *
        !           111: *
        !           112:       IF( INFO.NE.0 ) THEN
        !           113:          CALL XERBLA( 'DSYTRI2', -INFO )
        !           114:          RETURN
        !           115:       ELSE IF( LQUERY ) THEN
        !           116:          WORK(1)=(N+NBMAX+1)*(NBMAX+3)
        !           117:          RETURN
        !           118:       END IF
        !           119:       IF( N.EQ.0 )
        !           120:      $   RETURN
        !           121:       
        !           122:       CALL DSYTRI2X( UPLO, N, A, LDA, IPIV, WORK, NBMAX, INFO )
        !           123:       RETURN
        !           124: *
        !           125: *     End of DSYTRI2
        !           126: *
        !           127:       END