dla_syamv man page on Scientific

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```DLA_SYAMV(1LAPACK routine (version 3.2)				  DLA_SYAMV(1)

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

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

IMPLICIT	     NONE

DOUBLE	     PRECISION ALPHA, BETA

INTEGER	     INCX, INCY, LDA, N, UPLO

DOUBLE	     PRECISION A( LDA, * ), X( * ), Y( * )

PURPOSE
DLA_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 pro‐
tect 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 con‐
sidered "symbolic" if all multiplications involved  in  computing  that
entry have at least one zero multiplicand.

ARGUMENTS
UPLO   - 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 refer‐
enced.  UPLO = BLAS_LOWER	  Only the lower triangular part of  A
is to be referenced.  Unchanged on exit.

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

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

A      - DOUBLE PRECISION   array of DIMENSION ( LDA, n ).
Before entry, the leading m by n part of the array A  must  con‐
tain the matrix of coefficients.	Unchanged on exit.

LDA    - 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      - DOUBLE PRECISION   array of DIMENSION at least
(	 1  +  (  n  - 1 )*abs( INCX ) ) Before entry, the incremented
array X must contain the vector x.  Unchanged on exit.

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

BETA   - 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      - DOUBLE PRECISION   array of DIMENSION at least
( 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   - 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) November 2008			  DLA_SYAMV(1)
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