pderrscal()

subroutine pderrscal	(	double precision	errbnd,
		double precision	psclr,
		double precision	x,
		double precision	prec
	)

Definition at line 3245 of file pdblas1tst.f.

*
*  -- PBLAS test routine (version 2.0) --
*     University of Tennessee, Knoxville, Oak Ridge National Laboratory,
*     and University of California, Berkeley.
*     April 1, 1998
*
*     .. Scalar Arguments ..
      DOUBLE PRECISION   ERRBND, PREC, PSCLR, X
*     ..
*
*  Purpose
*  =======
*
*  PDERRSCAL serially computes the product PSCLR * X and returns a sca-
*  led relative acceptable error bound on the result.
*
*  Notes
*  =====
*
*  If s1 = PSCLR*X and  s2 are two different computed results, and s1 is
*  being assumed to be correct, we require
*
*        abs( s1 - s2 ) <= ERRBND = ERRFACT * abs( s1 ),
*
*  where ERRFACT is computed as two times the machine precision.
*
*  Arguments
*  =========
*
*  ERRBND  (global output) DOUBLE PRECISION
*          On exit, ERRBND  specifies the scaled relative acceptable er-
*          ror bound.
*
*  PSCLR   (global input) DOUBLE PRECISION
*          On entry, PSCLR specifies the scale factor.
*
*  X       (global input/global output) DOUBLE PRECISION
*          On entry, X  specifies the scalar to be scaled. On exit, X is
*          the scaled entry.
*
*  PREC    (global input) DOUBLE PRECISION
*          On entry, PREC specifies the machine precision.
*
*  -- Written on April 1, 1998 by
*     Antoine Petitet, University  of  Tennessee, Knoxville 37996, USA.
*
*  =====================================================================
*
*     .. Parameters ..
      DOUBLE PRECISION   TWO
      parameter( two = 2.0d+0 )
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          abs
*     ..
*     .. Executable Statements ..
*
      x = psclr * x
*
      errbnd = ( two * prec ) * abs( x )
*
      RETURN
*
*     End of PDERRSCAL
*

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