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subroutine rbicgst3d(cc,ce,cw,cn,cs,ct,cb,u,rhs,
& eps,rmax,ier,im,jm,km)
c
c This routine was lifted from stab.f. Minor modifications have
c been made.
c
implicit none
c
integer,intent(in) :: im,jm,km
real*8,intent(inout) :: cc(im,jm,km),cn(im,jm,km),cs(im,jm,km),
$ ce(im,jm,km),cw(im,jm,km),ct(im,jm,km),cb(im,jm,km)
real*8,intent(in) :: eps
real*8,intent(out) :: rmax
real*8,intent(inout) :: u(im,jm,km),rhs(im,jm,km)
c Local variable
integer ncyc
integer iscale,i,j,k,ier
c
c******************************************************************************
c
ncyc = (im-2)*(jm-2)*(km-2)
ier=0
*
* Determine whether we can diagonally scale the problem to speed
* convergence. Can only be done if there are no zeros on the main
* diagonal (ie. central difference coefficient).
*
iscale=1
do k = 2,km-1
do j = 2,jm-1
do i = 2,im-1
if (cc(i,j,k).eq.0.) iscale = 0
enddo
enddo
enddo
*
* Do the diagonal scaling if we can.
*
if (iscale.eq.1) then
do k = 2,km-1
do j = 2,jm-1
do i = 2,im-1
rhs(i,j,k)=rhs(i,j,k)/cc(i,j,k)
cb(i,j,k)=cb(i,j,k)/cc(i,j,k)
ct(i,j,k)=ct(i,j,k)/cc(i,j,k)
cw(i,j,k)=cw(i,j,k)/cc(i,j,k)
ce(i,j,k)=ce(i,j,k)/cc(i,j,k)
cs(i,j,k)=cs(i,j,k)/cc(i,j,k)
cn(i,j,k)=cn(i,j,k)/cc(i,j,k)
cc(i,j,k)=1.
enddo
enddo
enddo
endif
*
* Now call the bicgstab routine
*
call rbicgstab (cc,cn,cs,ce,cw,ct,cb,u,rhs,eps,ncyc,rmax,ier,
& im,jm,km)
if (rmax.gt.eps) then
ier = -1
print*,'Did not converge'
print*,' maximum residual = ',rmax
print*,' tolerance = ',eps
endif
return
end
c
c******************************************************************
c
subroutine rbicgstab (cc,cn,cs,ce,cw,ct,cb,x,r,tol,ncyc,rnorm,
$ ier,im,jm,km)
c
c This routine was lifted from stab.f. Minor modifications have
c been made.
c
implicit none
c
integer,intent(in) :: im,jm,km
integer,intent(in) :: ncyc
real*8,intent(in) :: cc(im*jm*km),cn(im*jm*km)
real*8,intent(in) :: cs(im*jm*km),ce(im*jm*km)
real*8,intent(in) :: cw(im*jm*km),ct(im*jm*km)
real*8,intent(in) :: cb(im*jm*km)
real*8,intent(in) :: tol
real*8,intent(out) :: rnorm
integer,intent(out) :: ier
real*8,intent(inout) :: x(im*jm*km),r(im*jm*km)
c Local variables
integer :: i,j,k,kk
real*8, allocatable :: p(:),Ap(:),w(:),As(:)
real*8 :: omega, chi,chi1,chi2, delta, deltap, pp
*
***********************************************************************
*
allocate(p(im*jm*km),Ap(im*jm*km),w(im*jm*km),As(im*jm*km))
do i = 1,im*jm*km
p(i) = 0.
Ap(i) = 0.
w(i) = 0.
As(i) = 0.
enddo
kk = 0
10 call rusermv(cc,cn,cs,ce,cw,ct,cb,x,Ap,im,jm,km)
do i = 1,im*jm*km
r(i) = r(i)-Ap(i)
p(i) = r(i)
enddo
c delta = sum(r)
delta = 0.
do i = 1,im*jm*km
delta = delta+r(i)
enddo
if (delta.eq.0.) then
ier=-1
return
endif
call rusermv(cc,cn,cs,ce,cw,ct,cb,p,Ap,im,jm,km)
c phi = sum(Ap)
pp = 0.
do i = 1,im*jm*km
pp = pp+Ap(i)
enddo
pp = pp/delta
if (pp.eq.0.) then
ier=-1
return
endif
c rnorm = sum(r**2)
rnorm = 0.
do i = 1,im*jm*km
rnorm = rnorm + r(i)**2
enddo
rnorm=sqrt(rnorm)
c Test if initial guess is great (residual less than tolerance)
if (rnorm .lt. tol) return
1 continue
kk = kk + 1
omega = 1./pp
do i = 1,im*jm*km
w(i) = r(i) - omega*Ap(i)
enddo
call rusermv(cc,cn,cs,ce,cw,ct,cb,w,As,im,jm,km)
c chi1 = sum(As*w)
chi1 = 0.
do i = 1,im*jm*km
chi1 = chi1+As(i)*w(i)
enddo
c chi2 = sum(As**2)
chi2 = 0.
do i = 1,im*jm*km
chi2 = chi2+As(i)**2
enddo
chi = chi1/chi2
do i = 1,im*jm*km
r(i) = w(i) - chi*As(i)
x(i) = x(i) + omega*p(i) + chi*w(i)
enddo
deltap = delta
c delta = sum(r)
delta = 0.
do i = 1,im*jm*km
delta = delta+r(i)
enddo
if (delta.eq.0.) then
goto 10
endif
do i = 1,im*jm*km
p(i) = r(i) + (p(i)-chi*Ap(i))*omega*
& delta/(deltap*chi)
enddo
call rusermv(cc,cn,cs,ce,cw,ct,cb,p,Ap,im,jm,km)
c phi = sum(Ap)
pp = 0.
do i = 1,im*jm*km
pp = pp+Ap(i)
enddo
pp=pp/delta
if (pp.eq.0.) then
goto 10
endif
if (kk.gt.ncyc) then
print*,' BI-CGStab solver reached maximum nuber of iterations.'
ier=-1
return
endif
c rnorm = sum(r**2)
rnorm = 0.
do i = 1,im*jm*km
rnorm = rnorm+r(i)**2
enddo
rnorm=sqrt(rnorm)
if (rnorm .gt. tol) goto 1
c
deallocate(p,Ap,w,As)
c
return
end
c
c******************************************************************
c
subroutine rusermv(cc,cn,cs,ce,cw,ct,cb,x,y,im,jm,km)
c
c This routine was lifted from stab.f. Minor modifications have
c been made.
c
c Be careful that the cs are zero on their outer boundary!!
c
implicit none
c
integer,intent(in) :: im,jm,km
real*8,intent(in) :: cc(im*jm*km),cn(im*jm*km)
real*8,intent(in) :: cs(im*jm*km),ce(im*jm*km)
real*8,intent(in) :: cw(im*jm*km),ct(im*jm*km)
real*8,intent(in) :: cb(im*jm*km)
real*8,intent(inout) :: x(im*jm*km), y(im*jm*km)
c Local variables
integer :: i, j, k
*
***********************************************************************
*
*
do i = im*jm+im+1,im*(jm*km-jm-1)
y(i) = cw(i)*x(i-1)
& +cc(i)*x(i)
& +ce(i)*x(i+1)
& +cn(i)*x(i+im)
& +cs(i)*x(i-im)
& +ct(i)*x(i+im*jm)
& +cb(i)*x(i-im*jm)
enddo
c
return
end
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