dla_gbamv.f(3)

NAME
dla_gbamv.f -

SYNOPSIS

  Functions/Subroutines
subroutine dla_gbamv (TRANS, M, N, KL, KU, ALPHA, AB, LDAB, X, INCX, BETA, Y, INCY)
DLA_GBAMV performs a matrix-vector operation to calculate error bounds.

Function/Subroutine Documentation

  subroutine dla_gbamv (integerTRANS, integerM, integerN, integerKL, integerKU, double precisionALPHA, double precision, dimension( ldab, * )AB, integerLDAB, double precision, dimension( * )X, integerINCX, double precisionBETA, double precision, dimension( * )Y, integerINCY)

DLA_GBAMV performs a matrix-vector operation to calculate error bounds.

Purpose:

     DLA_GBAMV  performs one of the matrix-vector operations
             y := alpha*abs(A)*abs(x) + beta*abs(y),
        or   y := alpha*abs(A)**T*abs(x) + beta*abs(y),
     where alpha and beta are scalars, x and y are vectors and A is an
     m by n matrix.
     This function is primarily used in calculating error bounds.
     To protect against underflow during evaluation, components in
     the resulting vector are perturbed away from zero by (N+1)
     times the underflow threshold.  To prevent unnecessarily large
     errors for block-structure embedded in general matrices,
     "symbolically" zero components are not perturbed.  A zero
     entry is considered "symbolic" if all multiplications involved
     in computing that entry have at least one zero multiplicand.

Parameters:
    TRANS

              TRANS is INTEGER
               On entry, TRANS specifies the operation to be performed as
               follows:
                 BLAS_NO_TRANS      y := alpha*abs(A)*abs(x) + beta*abs(y)
                 BLAS_TRANS         y := alpha*abs(A**T)*abs(x) + beta*abs(y)
                 BLAS_CONJ_TRANS    y := alpha*abs(A**T)*abs(x) + beta*abs(y)
               Unchanged on exit.

    M

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

    N

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

    KL

              KL is INTEGER
               The number of subdiagonals within the band of A.  KL >= 0.

    KU

              KU is INTEGER
               The number of superdiagonals within the band of A.  KU >= 0.

    ALPHA

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

    AB

              AB is DOUBLE PRECISION array of DIMENSION ( LDAB, n )
               Before entry, the leading m by n part of the array AB must
               contain the matrix of coefficients.
               Unchanged on exit.

    LDAB

              LDAB is INTEGER
               On entry, LDA specifies the first dimension of AB as declared
               in the calling (sub) program. LDAB must be at least
               max( 1, m ).
               Unchanged on exit.

    X

              X is DOUBLE PRECISION array, dimension
               ( 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.
               Unchanged on exit.

    INCX

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

    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.
               Unchanged on exit.

    Y

              Y is DOUBLE PRECISION array, dimension
               ( 1 + ( m - 1 )*abs( INCY ) ) when TRANS = 'N' or 'n'
               and at least
               ( 1 + ( n - 1 )*abs( INCY ) ) otherwise.
               Before entry with BETA non-zero, 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.
               Unchanged on exit.
      Level 2 Blas routine.

Author:
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Date:
    September 2012

Definition at line 185 of file dla_gbamv.f.

Author

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