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psblas3/krylov/psb_dcg.f90

304 lines
10 KiB
Fortran

!!$
!!$ Parallel Sparse BLAS v2.0
!!$ (C) Copyright 2006 Salvatore Filippone University of Rome Tor Vergata
!!$ Alfredo Buttari University of Rome Tor Vergata
!!$
!!$ Redistribution and use in source and binary forms, with or without
!!$ modification, are permitted provided that the following conditions
!!$ are met:
!!$ 1. Redistributions of source code must retain the above copyright
!!$ notice, this list of conditions and the following disclaimer.
!!$ 2. Redistributions in binary form must reproduce the above copyright
!!$ notice, this list of conditions, and the following disclaimer in the
!!$ documentation and/or other materials provided with the distribution.
!!$ 3. The name of the PSBLAS group or the names of its contributors may
!!$ not be used to endorse or promote products derived from this
!!$ software without specific written permission.
!!$
!!$ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
!!$ ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
!!$ TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
!!$ PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE PSBLAS GROUP OR ITS CONTRIBUTORS
!!$ BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
!!$ CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
!!$ SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
!!$ INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
!!$ CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
!!$ ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
!!$ POSSIBILITY OF SUCH DAMAGE.
!!$
!!$
! File: psb_dcg.f90
!!$ CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
!!$ C C
!!$ C References: C
!!$ C [1] Duff, I., Marrone, M., Radicati, G., and Vittoli, C. C
!!$ C Level 3 basic linear algebra subprograms for sparse C
!!$ C matrices: a user level interface C
!!$ C ACM Trans. Math. Softw., 23(3), 379-401, 1997. C
!!$ C C
!!$ C C
!!$ C [2] S. Filippone, M. Colajanni C
!!$ C PSBLAS: A library for parallel linear algebra C
!!$ C computation on sparse matrices C
!!$ C ACM Trans. on Math. Softw., 26(4), 527-550, Dec. 2000. C
!!$ C C
!!$ C [3] M. Arioli, I. Duff, M. Ruiz C
!!$ C Stopping criteria for iterative solvers C
!!$ C SIAM J. Matrix Anal. Appl., Vol. 13, pp. 138-144, 1992 C
!!$ C C
!!$ C C
!!$ C [4] R. Barrett et al C
!!$ C Templates for the solution of linear systems C
!!$ C SIAM, 1993
!!$ C C
!!$ C C
!!$ CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
! File: psb_dcg.f90
!
! Subroutine: psb_dcg
! This subroutine implements the Conjugate Gradient method.
!
! Arguments:
! a - type(<psb_dspmat_type>). The sparse matrix containing A.
! prec - type(<psb_prec_type>). The data structure containing the preconditioner.
! b - real,dimension(:). The right hand side.
! x - real,dimension(:). The vector of unknowns.
! eps - real. The error tolerance.
! desc_a - type(<psb_desc_type>). The communication descriptor.
! info - integer. Return code
! itmax - integer(optional). The maximum number of iterations.
! iter - integer(optional). The number of iterations performed.
! err - real(optional). The error on return.
! itrace - integer(optional). The unit to write messages onto.
! istop - integer(optional). The stopping criterium.
!
Subroutine psb_dcg(a,prec,b,x,eps,desc_a,info,&
&itmax,iter,err, itrace, istop)
use psb_base_mod
use psb_prec_mod
implicit none
!!$ Parameters
Type(psb_dspmat_type), Intent(in) :: a
Type(psb_dprec_type), Intent(in) :: prec
Type(psb_desc_type), Intent(in) :: desc_a
Real(Kind(1.d0)), Intent(in) :: b(:)
Real(Kind(1.d0)), Intent(inout) :: x(:)
Real(Kind(1.d0)), Intent(in) :: eps
integer, intent(out) :: info
Integer, Optional, Intent(in) :: itmax, itrace, istop
Integer, Optional, Intent(out) :: iter
Real(Kind(1.d0)), Optional, Intent(out) :: err
!!$ Local data
real(kind(1.d0)), allocatable, target :: aux(:), wwrk(:,:)
real(kind(1.d0)), pointer :: q(:), p(:), r(:), z(:), w(:)
real(kind(1.d0)) ::rerr
real(kind(1.d0)) ::alpha, beta, rho, rho_old, rni, xni, bni, ani,bn2,&
& sigma
integer :: litmax, liter, istop_, naux, m, mglob, it, itx, itrace_,&
& np,me, n_col, isvch, ich, ictxt, n_row,err_act, int_err(5)
logical, parameter :: exchange=.true., noexchange=.false.
character(len=20) :: name
info = 0
name = 'psb_dcg'
call psb_erractionsave(err_act)
ictxt = psb_cd_get_context(desc_a)
call psb_info(ictxt, me, np)
mglob = psb_cd_get_global_rows(desc_a)
n_row = psb_cd_get_local_rows(desc_a)
n_col = psb_cd_get_local_cols(desc_a)
if (present(istop)) then
istop_ = istop
else
istop_ = 1
endif
!
! ISTOP_ = 1: Normwise backward error, infinity norm
! ISTOP_ = 2: ||r||/||b|| norm 2
!
!!$ If ((prec%prec < min_prec_).Or.(prec%prec > max_prec_) ) Then
!!$ Write(0,*) 'F90_CG: Invalid IPREC',prec%prec
!!$ If (Present(ierr)) ierr=-1
!!$ Return
!!$ Endif
if ((istop_ < 1 ).or.(istop_ > 2 ) ) then
write(0,*) 'psb_cg: invalid istop',istop_
info=5001
int_err(1)=istop_
err=info
call psb_errpush(info,name,i_err=int_err)
goto 9999
endif
call psb_chkvect(mglob,1,size(x,1),1,1,desc_a,info)
if(info /= 0) then
info=4010
call psb_errpush(info,name,a_err='psb_chkvect on X')
goto 9999
end if
call psb_chkvect(mglob,1,size(b,1),1,1,desc_a,info)
if(info /= 0) then
info=4010
call psb_errpush(info,name,a_err='psb_chkvect on B')
goto 9999
end if
naux=4*n_col
allocate(aux(naux), stat=info)
if (info == 0) call psb_geall(wwrk,desc_a,info,n=5)
if (info == 0) call psb_geasb(wwrk,desc_a,info)
if (info.ne.0) then
info=4011
call psb_errpush(info,name)
goto 9999
end if
p => wwrk(:,1)
q => wwrk(:,2)
r => wwrk(:,3)
z => wwrk(:,4)
w => wwrk(:,5)
if (present(itmax)) then
litmax = itmax
else
litmax = 1000
endif
if (present(itrace)) then
itrace_ = itrace
else
itrace_ = 0
end if
itx=0
! Ensure global coherence for convergence checks.
call psb_set_coher(ictxt,isvch)
restart: do
!!$
!!$ r0 = b-Ax0
!!$
if (itx>= litmax) exit restart
it = 0
call psb_geaxpby(done,b,dzero,r,desc_a,info)
call psb_spmm(-done,a,x,done,r,desc_a,info,work=aux)
if (info.ne.0) then
info=4011
call psb_errpush(info,name)
goto 9999
end if
rho = dzero
if (istop_ == 1) then
ani = psb_spnrmi(a,desc_a,info)
bni = psb_geamax(b,desc_a,info)
else if (istop_ == 2) then
bn2 = psb_genrm2(b,desc_a,info)
endif
if (info.ne.0) then
info=4011
call psb_errpush(info,name)
goto 9999
end if
iteration: do
it = it + 1
itx = itx + 1
Call psb_precaply(prec,r,z,desc_a,info,work=aux)
rho_old = rho
rho = psb_gedot(r,z,desc_a,info)
if (it==1) then
call psb_geaxpby(done,z,dzero,p,desc_a,info)
else
if (rho_old==dzero) then
write(0,*) 'CG Iteration breakdown'
exit iteration
endif
beta = rho/rho_old
call psb_geaxpby(done,z,beta,p,desc_a,info)
end if
call psb_spmm(done,a,p,dzero,q,desc_a,info,work=aux)
sigma = psb_gedot(p,q,desc_a,info)
if (sigma==dzero) then
write(0,*) 'CG Iteration breakdown'
exit iteration
endif
alpha = rho/sigma
call psb_geaxpby(alpha,p,done,x,desc_a,info)
call psb_geaxpby(-alpha,q,done,r,desc_a,info)
if (istop_ == 1) Then
rni = psb_geamax(r,desc_a,info)
xni = psb_geamax(x,desc_a,info)
rerr = rni/(ani*xni+bni)
Else If (istop_ == 2) Then
rni = psb_genrm2(r,desc_a,info)
rerr = rni/bn2
Endif
if (rerr<=eps) exit restart
if (itx>= litmax) exit restart
If (itrace_ > 0) then
if ((mod(itx,itrace_)==0).and.(me == 0))&
& write(*,'(a,i4,3(2x,es10.4))') 'cg: ',itx,rerr
end If
end do iteration
end do restart
If (itrace_ > 0) then
if (me == 0) write(*,'(a,i4,3(2x,es10.4))') 'cg: ',itx,rerr
end If
if (present(err)) err=rerr
if (present(iter)) iter = itx
if (rerr>eps) then
write(0,*) 'CG Failed to converge to ',eps,&
& ' in ',litmax,' iterations '
info=itx
end if
deallocate(aux)
call psb_gefree(wwrk,desc_a,info)
! restore external global coherence behaviour
call psb_restore_coher(ictxt,isvch)
if (info.ne.0) then
call psb_errpush(info,name)
goto 9999
end if
call psb_erractionrestore(err_act)
return
9999 continue
call psb_erractionrestore(err_act)
if (err_act.eq.psb_act_abort_) then
call psb_error()
return
end if
return
end subroutine psb_dcg