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dgscale.F
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	subroutine dgscale( nn, gold, xdiff, diag, rmin )


	c ==================================================================
	c SUBROUTINE dgscale
	c ==================================================================
	c
	c o computes new preconditioner and writes it to OPWARMD
	c
	c o started: ??? not reproducible
	c
	c o Version: 2.1.0, 02-Mar-2000: Patrick Heimbach, MIT/EAPS
	c
	c ==================================================================
	c SUBROUTINE dgscale
	c ==================================================================

	implicit none

	#include "blas1.h"

	integer nn
	double precision gold(nn), xdiff(nn), diag(nn)

	integer i
	double precision r1, rmin, den


	c-----------------------------------------
	c read diagonal
	c-----------------------------------------
	call dostore( nn, diag, .false., 3 )

	r1 = 0.
	do i = 1, nn
	r1 = r1 + gold(i)gold(i)diag(i)
	end do
	r1 = 1.0 / r1

	call SSCAL( nn, r1, diag, 1 )

	c-----------------------------------------
	c update the diagonal
	c (gg is used as an auxiliary vector)
	c-----------------------------------------

	den = 0.0

	do i = 1, nn
	cph(
	if (diag(i).LE.0) then
	cph print *, 'pathei-lsopt: in dgscale; diag = 0 for i=', i
	diag(i) = rmin
	end if
	cph)
	den = den + xdiff(i)*xdiff(i) / diag(i)
	end do

	do i = 1, nn
	diag(i) = 1./
	$ (1./diag(i)+gold(i)2-(xdiff(i)/diag(i))2/den)
	if (diag(i).le.0.) then
	diag(i) = rmin
	endif
	end do

	c-----------------------------------------
	c write diagonal
	c-----------------------------------------
	call dostore( nn, diag, .true., 3 )

	return
	end