LAPACK  3.4.2
LAPACK: Linear Algebra PACKage
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cla_heamv.f File Reference

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Functions/Subroutines

subroutine cla_heamv (UPLO, N, ALPHA, A, LDA, X, INCX, BETA, Y, INCY)
 CLA_HEAMV computes a matrix-vector product using a Hermitian indefinite matrix to calculate error bounds.

Function/Subroutine Documentation

subroutine cla_heamv ( integer  UPLO,
integer  N,
real  ALPHA,
complex, dimension( lda, * )  A,
integer  LDA,
complex, dimension( * )  X,
integer  INCX,
real  BETA,
real, dimension( * )  Y,
integer  INCY 
)

CLA_HEAMV computes a matrix-vector product using a Hermitian indefinite matrix to calculate error bounds.

Download CLA_HEAMV + dependencies [TGZ] [ZIP] [TXT]
Purpose:
 CLA_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.
Parameters:
[in]UPLO
          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.
[in]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.
[in]ALPHA
          ALPHA is REAL .
           On entry, ALPHA specifies the scalar alpha.
           Unchanged on exit.
[in]A
          A is COMPLEX 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.
[in]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, n ).
           Unchanged on exit.
[in]X
          X is COMPLEX array, dimension
           ( 1 + ( n - 1 )*abs( INCX ) )
           Before entry, the incremented array X must contain the
           vector x.
           Unchanged on exit.
[in]INCX
          INCX is INTEGER
           On entry, INCX specifies the increment for the elements of
           X. INCX must not be zero.
           Unchanged on exit.
[in]BETA
          BETA is 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.
[in,out]Y
          Y is 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.
[in]INCY
          INCY is INTEGER
           On entry, INCY specifies the increment for the elements of
           Y. INCY must not be zero.
           Unchanged on exit.
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
September 2012
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

Definition at line 178 of file cla_heamv.f.

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