zla_geamv.f man page

zla_geamv.f —

Synopsis

Functions/Subroutines

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

Function/Subroutine Documentation

subroutine zla_geamv (integerTRANS, integerM, integerN, double precisionALPHA, complex*16, dimension( lda, * )A, integerLDA, complex*16, dimension( * )X, integerINCX, double precisionBETA, double precision, dimension( * )Y, integerINCY)

ZLA_GEAMV computes a matrix-vector product using a general matrix to calculate error bounds.

Purpose:

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

A

A is COMPLEX*16 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 COMPLEX*16 array of DIMENSION at least
 ( 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 175 of file zla_geamv.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

zla_geamv(3) is an alias of zla_geamv.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK