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Annotation of rpl/lapack/lapack/dsytri2.f, revision 1.3

1.1       bertrand    1:       SUBROUTINE DSYTRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO )
                      2: *
1.3     ! bertrand    3: *  -- LAPACK routine (version 3.3.1) --
1.1       bertrand    4: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
                      5: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.3     ! bertrand    6: *  -- April 2011                                                      --
1.1       bertrand    7: *
                      8: *  -- Written by Julie Langou of the Univ. of TN    --
                      9: *
1.3     ! bertrand   10: * @generated d
1.1       bertrand   11: *     .. Scalar Arguments ..
                     12:       CHARACTER          UPLO
                     13:       INTEGER            INFO, LDA, LWORK, N
                     14: *     ..
                     15: *     .. Array Arguments ..
                     16:       INTEGER            IPIV( * )
                     17:       DOUBLE PRECISION   A( LDA, * ), WORK( * )
                     18: *     ..
                     19: *
                     20: *  Purpose
                     21: *  =======
                     22: *
1.3     ! bertrand   23: *  DSYTRI2 computes the inverse of a DOUBLE PRECISION hermitian indefinite matrix
1.1       bertrand   24: *  A using the factorization A = U*D*U**T or A = L*D*L**T computed by
                     25: *  DSYTRF. DSYTRI2 sets the LEADING DIMENSION of the workspace
                     26: *  before calling DSYTRI2X that actually computes the inverse.
                     27: *
                     28: *  Arguments
                     29: *  =========
                     30: *
                     31: *  UPLO    (input) CHARACTER*1
                     32: *          Specifies whether the details of the factorization are stored
                     33: *          as an upper or lower triangular matrix.
                     34: *          = 'U':  Upper triangular, form is A = U*D*U**T;
                     35: *          = 'L':  Lower triangular, form is A = L*D*L**T.
                     36: *
                     37: *  N       (input) INTEGER
                     38: *          The order of the matrix A.  N >= 0.
                     39: *
                     40: *  A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
                     41: *          On entry, the NB diagonal matrix D and the multipliers
                     42: *          used to obtain the factor U or L as computed by DSYTRF.
                     43: *
                     44: *          On exit, if INFO = 0, the (symmetric) inverse of the original
                     45: *          matrix.  If UPLO = 'U', the upper triangular part of the
                     46: *          inverse is formed and the part of A below the diagonal is not
                     47: *          referenced; if UPLO = 'L' the lower triangular part of the
                     48: *          inverse is formed and the part of A above the diagonal is
                     49: *          not referenced.
                     50: *
                     51: *  LDA     (input) INTEGER
                     52: *          The leading dimension of the array A.  LDA >= max(1,N).
                     53: *
                     54: *  IPIV    (input) INTEGER array, dimension (N)
                     55: *          Details of the interchanges and the NB structure of D
                     56: *          as determined by DSYTRF.
                     57: *
                     58: *  WORK    (workspace) DOUBLE PRECISION array, dimension (N+NB+1)*(NB+3)
                     59: *
                     60: *  LWORK   (input) INTEGER
                     61: *          The dimension of the array WORK.
                     62: *          WORK is size >= (N+NB+1)*(NB+3)
                     63: *          If LDWORK = -1, then a workspace query is assumed; the routine
                     64: *           calculates:
                     65: *              - the optimal size of the WORK array, returns
                     66: *          this value as the first entry of the WORK array,
                     67: *              - and no error message related to LDWORK is issued by XERBLA.
                     68: *
                     69: *  INFO    (output) INTEGER
                     70: *          = 0: successful exit
                     71: *          < 0: if INFO = -i, the i-th argument had an illegal value
                     72: *          > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its
                     73: *               inverse could not be computed.
                     74: *
                     75: *  =====================================================================
                     76: *
                     77: *     .. Local Scalars ..
                     78:       LOGICAL            UPPER, LQUERY
                     79:       INTEGER            MINSIZE, NBMAX
                     80: *     ..
                     81: *     .. External Functions ..
                     82:       LOGICAL            LSAME
                     83:       INTEGER            ILAENV
                     84:       EXTERNAL           LSAME, ILAENV
                     85: *     ..
                     86: *     .. External Subroutines ..
                     87:       EXTERNAL           DSYTRI2X
                     88: *     ..
                     89: *     .. Executable Statements ..
                     90: *
                     91: *     Test the input parameters.
                     92: *
                     93:       INFO = 0
                     94:       UPPER = LSAME( UPLO, 'U' )
                     95:       LQUERY = ( LWORK.EQ.-1 )
                     96: *     Get blocksize
                     97:       NBMAX = ILAENV( 1, 'DSYTRF', UPLO, N, -1, -1, -1 )
1.3     ! bertrand   98:       IF ( NBMAX .GE. N ) THEN
        !            99:          MINSIZE = N
        !           100:       ELSE
        !           101:          MINSIZE = (N+NBMAX+1)*(NBMAX+3)
        !           102:       END IF
1.1       bertrand  103: *
                    104:       IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
                    105:          INFO = -1
                    106:       ELSE IF( N.LT.0 ) THEN
                    107:          INFO = -2
                    108:       ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
                    109:          INFO = -4
                    110:       ELSE IF (LWORK .LT. MINSIZE .AND. .NOT.LQUERY ) THEN
                    111:          INFO = -7
                    112:       END IF
                    113: *
                    114: *     Quick return if possible
                    115: *
                    116: *
                    117:       IF( INFO.NE.0 ) THEN
                    118:          CALL XERBLA( 'DSYTRI2', -INFO )
                    119:          RETURN
                    120:       ELSE IF( LQUERY ) THEN
1.3     ! bertrand  121:          WORK(1)=MINSIZE
1.1       bertrand  122:          RETURN
                    123:       END IF
                    124:       IF( N.EQ.0 )
                    125:      $   RETURN
                    126:       
1.3     ! bertrand  127:       IF( NBMAX .GE. N ) THEN
        !           128:          CALL DSYTRI( UPLO, N, A, LDA, IPIV, WORK, INFO )
        !           129:       ELSE
        !           130:          CALL DSYTRI2X( UPLO, N, A, LDA, IPIV, WORK, NBMAX, INFO )
        !           131:       END IF
1.1       bertrand  132:       RETURN
                    133: *
                    134: *     End of DSYTRI2
                    135: *
                    136:       END