NAME

       sla_geamv.f -

SYNOPSIS

   Functions/Subroutines
       subroutine sla_geamv (TRANS, M, N, ALPHA, A, LDA, X, INCX, BETA, Y, INCY)
           SLA_GEAMV computes a matrix-vector product using a general matrix to calculate error
           bounds.

Function/Subroutine Documentation

   subroutine sla_geamv (integerTRANS, integerM, integerN, realALPHA, real, dimension( lda, * )A,
       integerLDA, real, dimension( * )X, integerINCX, realBETA, real, dimension( * )Y,
       integerINCY)
       SLA_GEAMV computes a matrix-vector product using a general matrix to calculate error
       bounds.

       Purpose:

            SLA_GEAMV  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.

           ALPHA

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

           A

                     A is REAL array of DIMENSION ( LDA, n )
                      Before entry, the leading m by n part of the array A must
                      contain the matrix of coefficients.
                      Unchanged on exit.

           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
                      max( 1, m ).
                      Unchanged on exit.

           X

                     X is REAL 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 REAL
                      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 REAL
                      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 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 174 of file sla_geamv.f.

Author

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