dgbmv.f(3)

NAME
dgbmv.f -

SYNOPSIS

  Functions/Subroutines
subroutine dgbmv (TRANS, M, N, KL, KU, ALPHA, A, LDA, X, INCX, BETA, Y, INCY)
DGBMV

Function/Subroutine Documentation

  subroutine dgbmv (characterTRANS, integerM, integerN, integerKL, integerKU, double precisionALPHA, double precision, dimension(lda,*)A, integerLDA, double precision, dimension(*)X, integerINCX, double precisionBETA, double precision, dimension(*)Y, integerINCY)

DGBMV Purpose:

     DGBMV  performs one of the matrix-vector operations
        y := alpha*A*x + beta*y,   or   y := alpha*A**T*x + beta*y,
     where alpha and beta are scalars, x and y are vectors and A is an
     m by n band matrix, with kl sub-diagonals and ku super-diagonals.

Parameters:
    TRANS

              TRANS is CHARACTER*1
               On entry, TRANS specifies the operation to be performed as
               follows:
                  TRANS = 'N' or 'n'   y := alpha*A*x + beta*y.
                  TRANS = 'T' or 't'   y := alpha*A**T*x + beta*y.
                  TRANS = 'C' or 'c'   y := alpha*A**T*x + beta*y.

    M

              M is INTEGER
               On entry, M specifies the number of rows of the matrix A.
               M must be at least zero.

    N

              N is INTEGER
               On entry, N specifies the number of columns of the matrix A.
               N must be at least zero.

    KL

              KL is INTEGER
               On entry, KL specifies the number of sub-diagonals of the
               matrix A. KL must satisfy  0 .le. KL.

    KU

              KU is INTEGER
               On entry, KU specifies the number of super-diagonals of the
               matrix A. KU must satisfy  0 .le. KU.

    ALPHA

              ALPHA is DOUBLE PRECISION.
               On entry, ALPHA specifies the scalar alpha.

    A

              A is DOUBLE PRECISION array of DIMENSION ( LDA, n ).
               Before entry, the leading ( kl + ku + 1 ) by n part of the
               array A must contain the matrix of coefficients, supplied
               column by column, with the leading diagonal of the matrix in
               row ( ku + 1 ) of the array, the first super-diagonal
               starting at position 2 in row ku, the first sub-diagonal
               starting at position 1 in row ( ku + 2 ), and so on.
               Elements in the array A that do not correspond to elements
               in the band matrix (such as the top left ku by ku triangle)
               are not referenced.
               The following program segment will transfer a band matrix
               from conventional full matrix storage to band storage:
                     DO 20, J = 1, N
                        K = KU + 1 - J
                        DO 10, I = MAX( 1, J - KU ), MIN( M, J + KL )
                           A( K + I, J ) = matrix( I, J )
                  10    CONTINUE
                  20 CONTINUE

    LDA

              LDA is INTEGER
               On entry, LDA specifies the first dimension of A as declared
               in the calling (sub) program. LDA must be at least
               ( kl + ku + 1 ).

    X

              X is DOUBLE PRECISION array of DIMENSION at least
               ( 1 + ( n - 1 )*abs( INCX ) ) when TRANS = 'N' or 'n'
               and at least
               ( 1 + ( m - 1 )*abs( INCX ) ) otherwise.
               Before entry, the incremented array X must contain the
               vector x.

    INCX

              INCX is INTEGER
               On entry, INCX specifies the increment for the elements of
               X. INCX must not be zero.

    BETA

              BETA is DOUBLE PRECISION.
               On entry, BETA specifies the scalar beta. When BETA is
               supplied as zero then Y need not be set on input.

    Y

              Y is DOUBLE PRECISION array of DIMENSION at least
               ( 1 + ( m - 1 )*abs( INCY ) ) when TRANS = 'N' or 'n'
               and at least
               ( 1 + ( n - 1 )*abs( INCY ) ) otherwise.
               Before entry, the incremented array Y must contain the
               vector y. On exit, Y is overwritten by the updated vector y.

    INCY

              INCY is INTEGER
               On entry, INCY specifies the increment for the elements of
               Y. INCY must not be zero.

Author:
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Date:
    November 2011

Further Details:

      Level 2 Blas routine.
      The vector and matrix arguments are not referenced when N = 0, or M = 0
      -- Written on 22-October-1986.
         Jack Dongarra, Argonne National Lab.
         Jeremy Du Croz, Nag Central Office.
         Sven Hammarling, Nag Central Office.
         Richard Hanson, Sandia National Labs.

Definition at line 186 of file dgbmv.f.

Author

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