Provided by: liblapack-doc_3.3.1-1_all bug

NAME

       LAPACK-3 - performs the matrix-vector operation   y := alpha*abs(A)*abs(x) + beta*abs(y),

SYNOPSIS

       SUBROUTINE SLA_SYAMV( UPLO, N, ALPHA, A, LDA, X, INCX, BETA, Y, INCY )

           IMPLICIT          NONE

           REAL              ALPHA, BETA

           INTEGER           INCX, INCY, LDA, N, UPLO

           REAL              A( LDA, * ), X( * ), Y( * )

PURPOSE

       SLA_SYAMV  performs the matrix-vector operation
        where alpha and beta are scalars, x and y are vectors and A is an
        n by n symmetric 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.

ARGUMENTS

        UPLO    (input) INTEGER
                On entry, UPLO specifies whether the upper or lower
                triangular part of the array A is to be referenced as
                follows:
                UPLO = BLAS_UPPER   Only the upper triangular part of A
                is to be referenced.
                UPLO = BLAS_LOWER   Only the lower triangular part of A
                is to be referenced.
                Unchanged on exit.

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

        ALPHA   (input) REAL            .
                On entry, ALPHA specifies the scalar alpha.
                Unchanged on exit.

        A      - 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     (input) INTEGER
                On entry, LDA specifies the first dimension of A as declared
                in the calling (sub) program. LDA must be at least
                max( 1, n ).
                Unchanged on exit.

        X       (input) REAL array, dimension
                ( 1 + ( n - 1 )*abs( INCX ) )
                Before entry, the incremented array X must contain the
                vector x.
                Unchanged on exit.

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

        BETA    (input) 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       (input/output) REAL array, dimension
                ( 1 + ( n - 1 )*abs( INCY ) )
                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    (input) INTEGER
                On entry, INCY specifies the increment for the elements of
                Y. INCY must not be zero.
                Unchanged on exit.

FURTHER DETAILS

        Level 2 Blas routine.
        -- 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.
        -- Modified for the absolute-value product, April 2006
           Jason Riedy, UC Berkeley

    LAPACK routine (version 3.2.2)          April 2011                         SLA_SYAMV(3lapack)