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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Functions/Subroutines

Function/Subroutine Documentation