.TH "SRC/zla_syamv.f" 3 "Version 3.12.0" "LAPACK" \" -*- nroff -*-
.ad l
.nh
.SH NAME
SRC/zla_syamv.f
.SH SYNOPSIS
.br
.PP
.SS "Functions/Subroutines"

.in +1c
.ti -1c
.RI "subroutine \fBzla_syamv\fP (uplo, n, alpha, a, lda, x, incx, beta, y, incy)"
.br
.RI "\fBZLA_SYAMV\fP computes a matrix-vector product using a symmetric indefinite matrix to calculate error bounds\&. "
.in -1c
.SH "Function/Subroutine Documentation"
.PP 
.SS "subroutine zla_syamv (integer uplo, integer n, double precision alpha, complex*16, dimension( lda, * ) a, integer lda, complex*16, dimension( * ) x, integer incx, double precision beta, double precision, dimension( * ) y, integer incy)"

.PP
\fBZLA_SYAMV\fP computes a matrix-vector product using a symmetric indefinite matrix to calculate error bounds\&.  
.PP
\fBPurpose:\fP
.RS 4

.PP
.nf
!>
!> ZLA_SYAMV  performs the matrix-vector operation
!>
!>         y := alpha*abs(A)*abs(x) + beta*abs(y),
!>
!> 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,
!>  zero components are not perturbed\&.  A zero
!> entry is considered  if all multiplications involved
!> in computing that entry have at least one zero multiplicand\&.
!> 
.fi
.PP
 
.RE
.PP
\fBParameters\fP
.RS 4
\fIUPLO\fP 
.PP
.nf
!>          UPLO is 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\&.
!> 
.fi
.PP
.br
\fIN\fP 
.PP
.nf
!>          N is INTEGER
!>           On entry, N specifies the number of columns of the matrix A\&.
!>           N must be at least zero\&.
!>           Unchanged on exit\&.
!> 
.fi
.PP
.br
\fIALPHA\fP 
.PP
.nf
!>          ALPHA is DOUBLE PRECISION \&.
!>           On entry, ALPHA specifies the scalar alpha\&.
!>           Unchanged on exit\&.
!> 
.fi
.PP
.br
\fIA\fP 
.PP
.nf
!>          A is COMPLEX*16 array, dimension ( LDA, n )\&.
!>           Before entry, the leading m by n part of the array A must
!>           contain the matrix of coefficients\&.
!>           Unchanged on exit\&.
!> 
.fi
.PP
.br
\fILDA\fP 
.PP
.nf
!>          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, n )\&.
!>           Unchanged on exit\&.
!> 
.fi
.PP
.br
\fIX\fP 
.PP
.nf
!>          X is COMPLEX*16 array, dimension at least
!>           ( 1 + ( n - 1 )*abs( INCX ) )
!>           Before entry, the incremented array X must contain the
!>           vector x\&.
!>           Unchanged on exit\&.
!> 
.fi
.PP
.br
\fIINCX\fP 
.PP
.nf
!>          INCX is INTEGER
!>           On entry, INCX specifies the increment for the elements of
!>           X\&. INCX must not be zero\&.
!>           Unchanged on exit\&.
!> 
.fi
.PP
.br
\fIBETA\fP 
.PP
.nf
!>          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\&.
!> 
.fi
.PP
.br
\fIY\fP 
.PP
.nf
!>          Y is DOUBLE PRECISION 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\&.
!> 
.fi
.PP
.br
\fIINCY\fP 
.PP
.nf
!>          INCY is INTEGER
!>           On entry, INCY specifies the increment for the elements of
!>           Y\&. INCY must not be zero\&.
!>           Unchanged on exit\&.
!> 
.fi
.PP
 
.RE
.PP
\fBAuthor\fP
.RS 4
Univ\&. of Tennessee 

.PP
Univ\&. of California Berkeley 

.PP
Univ\&. of Colorado Denver 

.PP
NAG Ltd\&. 
.RE
.PP
\fBFurther Details:\fP
.RS 4

.PP
.nf
!>
!>  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
!> 
.fi
.PP
 
.RE
.PP

.PP
Definition at line \fB177\fP of file \fBzla_syamv\&.f\fP\&.
.SH "Author"
.PP 
Generated automatically by Doxygen for LAPACK from the source code\&.