.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,
 '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\&.
.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\&.