SRC/zla_gbamv.f(3)         Library Functions Manual         SRC/zla_gbamv.f(3)

NAME
       SRC/zla_gbamv.f

SYNOPSIS
   Functions/Subroutines
       subroutine zla_gbamv (trans, m, n, kl, ku, alpha, ab, ldab, x, incx,
           beta, y, incy)
           ZLA_GBAMV performs a matrix-vector operation to calculate error
           bounds.

Function/Subroutine Documentation
   subroutine zla_gbamv (integer trans, integer m, integer n, integer kl,
       integer ku, double precision alpha, complex*16, dimension( ldab, * )
       ab, integer ldab, complex*16, dimension( * ) x, integer incx, double
       precision beta, double precision, dimension( * ) y, integer incy)
       ZLA_GBAMV performs a matrix-vector operation to calculate error bounds.

       Purpose:


            ZLA_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 COMPLEX*16 array, 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, LDAB 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 COMPLEX*16 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.
                      If either m or n is zero, then Y not referenced and the function
                      performs a quick return.

           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.

       Definition at line 186 of file zla_gbamv.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

LAPACK                          Version 3.12.0              SRC/zla_gbamv.f(3)