cla_syamv.f man page on Oracle

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cla_syamv.f(3)			    LAPACK			cla_syamv.f(3)

       cla_syamv.f -

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

Function/Subroutine Documentation
   subroutine cla_syamv (integerUPLO, integerN, realALPHA, complex, dimension(
       lda, * )A, integerLDA, complex, dimension( * )X, integerINCX, realBETA,
       real, dimension( * )Y, integerINCY)
       CLA_SYAMV computes a matrix-vector product using a symmetric indefinite
       matrix to calculate error bounds.


	    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.


		     UPLO is INTEGER
		      On entry, UPLO specifies whether the upper or lower
		      triangular part of the array A is to be referenced as

			 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.


		     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 is REAL .
		      On entry, ALPHA specifies the scalar alpha.
		      Unchanged on exit.


		     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.


		     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.


		     X is COMPLEX array, dimension
		      ( 1 + ( n - 1 )*abs( INCX ) )
		      Before entry, the incremented array X must contain the
		      vector x.
		      Unchanged on exit.


		     INCX is INTEGER
		      On entry, INCX specifies the increment for the elements of
		      X. INCX must not be zero.
		      Unchanged on exit.


		     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.


		     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.


		     INCY is INTEGER
		      On entry, INCY specifies the increment for the elements of
		      Y. INCY must not be zero.
		      Unchanged on exit.

	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

	   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 179 of file cla_syamv.f.

       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2			Tue Sep 25 2012			cla_syamv.f(3)

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