!
! Parallel Sparse BLAS version 3.5
! (C) Copyright 2006, 2010, 2015, 2017
! Salvatore Filippone Cranfield University
! Alfredo Buttari CNRS-IRIT, Toulouse
!
! 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_dfcg.f90
!!
!! Contributors: Ambra Abdullahi (UNITOV) and Pasqua D’Ambra (IAC-CNR)
!!
! 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 [4] Notay, Yvan C
! C Flexible Conjugate gradients C
! C SIAM Journal on Scientific Computing 22(4), C
! C pp. 1444-1460, 2000 C
! C C
! C C
! CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
! File: psb_dfcg.f90
!
! Subroutine: psb_dfcg
! This subroutine implements the Flexible Conjugate Gradient method.
!
!
! Arguments:
!
! a - type(psb_dspmat_type) Input: sparse matrix containing A.
! prec - class(psb_dprec_type) Input: preconditioner
! b(:) - real Input: vector containing the
! right hand side B
! x(:) - real Input/Output: vector containing the
! initial guess and final solution X.
! eps - real Input: Stopping tolerance; the iteration is
! stopped when the error estimate |err| <= eps
! desc_a - type(psb_desc_type). Input: The communication descriptor.
! info - integer. Output: Return code
!
! itmax - integer(optional) Input: maximum number of iterations to be
! performed.
! iter - integer(optional) Output: how many iterations have been
! performed.
! performed.
! err - real (optional) Output: error estimate on exit. If the
! denominator of the estimate is exactly
! 0, it is changed into 1.
! itrace - integer(optional) Input: print an informational message
! with the error estimate every itrace
! iterations
! istop - integer(optional) Input: stopping criterion, or how
! to estimate the error.
! 1: err = |r|/(|a||x|+|b|); here the iteration is
! stopped when |r| <= eps * (|a||x|+|b|)
! 2: err = |r|/|b|; here the iteration is
! stopped when |r| <= eps * |b|
! where r is the (preconditioned, recursive
! estimate of) residual.
!
!
subroutine psb_dfcg_vect(a,prec,b,x,eps,desc_a,info,&
& itmax,iter,err,itrace,istop,cond)
use psb_base_mod
use psb_prec_mod
use psb_d_krylov_conv_mod
use psb_krylov_mod
implicit none
type(psb_dspmat_type), intent(in) :: a
Type(psb_desc_type), Intent(in) :: desc_a
class(psb_dprec_type), intent(inout) :: prec
type(psb_d_vect_type), Intent(inout) :: b
type(psb_d_vect_type), Intent(inout) :: x
real(psb_dpk_), Intent(in) :: eps
integer(psb_ipk_), intent(out) :: info
integer(psb_ipk_), Optional, Intent(in) :: itmax, itrace, istop
integer(psb_ipk_), Optional, Intent(out) :: iter
real(psb_dpk_), Optional, Intent(out) :: err,cond
! = Local data
type(psb_d_vect_type) :: v, w
type(psb_d_vect_type), dimension(0:1) :: d
real(psb_dpk_) :: alpha, tau, tau1, beta, delta
real(psb_dpk_) :: derr
integer(psb_ipk_) :: i, idx, nc2l, it, itx, istop_, itmax_, itrace_
integer(psb_ipk_) :: n_col, mglob, naux, err_act
integer(psb_ipk_) :: debug_level, debug_unit
integer(psb_ipk_) :: np, me, ictxt
real(psb_dpk_), allocatable, target :: aux(:)
character(len=20) :: name
type(psb_itconv_type) :: stopdat
character(len=*), parameter :: methdname='FCG'
info = psb_success_
name = 'psb_dfcg'
call psb_erractionsave(err_act)
debug_unit = psb_get_debug_unit()
debug_level = psb_get_debug_level()
ictxt = desc_a%get_context()
call psb_info(ictxt, me, np)
if (.not.allocated(b%v)) then
info = psb_err_invalid_vect_state_
call psb_errpush(info,name)
goto 9999
endif
if (.not.allocated(x%v)) then
info = psb_err_invalid_vect_state_
call psb_errpush(info,name)
goto 9999
endif
mglob = desc_a%get_global_rows()
n_col = desc_a%get_local_cols()
if (present(istop)) then
istop_ = istop
else
istop_ = 2
endif
call psb_chkvect(mglob,ione,x%get_nrows(),ione,ione,desc_a,info)
if (info == psb_success_)&
& call psb_chkvect(mglob,ione,b%get_nrows(),ione,ione,desc_a,info)
if(info /= psb_success_) then
info=psb_err_from_subroutine_
call psb_errpush(info,name,a_err='psb_chkvect on X/B')
goto 9999
end if
naux=4*n_col
allocate(aux(naux), stat=info)
if (present(itmax)) then
itmax_ = itmax
else
itmax_ = 1000
endif
if (present(itrace)) then
itrace_ = itrace
else
itrace_ = 0
end if
!Assemble w, v
call psb_geasb(w,&
& desc_a,info,&
& scratch=.true.,mold=b%v)
call psb_geasb(v,&
& desc_a,info,&
& scratch=.true.,mold=b%v)
!Assemble d(0) and d(1)
call psb_geasb(d(0),&
& desc_a,info,&
& scratch=.true.,mold=x%v)
call psb_geasb(d(1),&
& desc_a,info,&
& scratch=.true.,mold=x%v)
call psb_init_conv(methdname,istop_,itrace_,itmax_,a,x,b,eps,desc_a,stopdat,info)
itx=0
restart: do
if (itx>= itmax_) exit restart
! w=b
call psb_geaxpby(done,b,dzero,w,&
& desc_a,info)
if (psb_errstatus_fatal()) then
nc2l = desc_a%get_local_cols()
info=psb_err_alloc_request_
call psb_errpush(info,name,i_err=(/2*nc2l,izero,izero,izero,izero/),&
& a_err='real(psb_dpk_)')
goto 9999
end if
!Compute v = Ax
call psb_spmm(done,a,x,dzero,v,desc_a,info)
if (info /= psb_success_) then
call psb_errpush(psb_err_internal_error_,name,&
& a_err='Error during residue')
goto 9999
end if
!Compute w = -Ax + b
call psb_geaxpby(-done, v, done, w, desc_a, info)
!Apply the preconditioner
idx=0
call prec%apply(w,d(idx),desc_a,info,work=aux)
delta = psb_gedot(d(idx), w, desc_a, info)
!Loop
if (psb_check_conv(methdname,itx ,x,w,desc_a,stopdat,info)) exit restart
if (info /= psb_success_) Then
call psb_errpush(psb_err_from_subroutine_non_,name)
goto 9999
End If
iteration: do
call psb_spmm(done,a,d(idx),dzero,v,desc_a,info)
if (info /= psb_success_) then
call psb_errpush(psb_err_internal_error_,name,&
& a_err='Error during residue')
goto 9999
end if
tau = psb_gedot(d(idx), v, desc_a, info)
alpha = delta/tau
!Update solution x
call psb_geaxpby(alpha, d(idx), done, x, desc_a, info)
!Update residual w
call psb_geaxpby(-alpha, v, done, w, desc_a, info)
itx = itx + 1
idx=mod(itx ,2)
call d(idx)%set(dzero)
call prec%apply(w,d(idx),desc_a,info,work=aux)
tau1= psb_gedot(d(idx), v, desc_a, info)
beta=tau1/tau
if (idx == 1) then
call psb_geaxpby(-beta, d(idx - 1), done, d(idx), desc_a, info)
else
call psb_geaxpby(-beta, d(idx + 1), done, d(idx), desc_a, info)
endif
delta = psb_gedot(w, d(idx), desc_a, info)
if (psb_check_conv(methdname,itx ,x,w,desc_a,stopdat,info)) exit restart
if (info /= psb_success_) Then
call psb_errpush(psb_err_from_subroutine_non_,name)
goto 9999
End If
end do iteration
end do restart
call psb_end_conv(methdname,itx ,desc_a,stopdat,info,derr,iter)
if (present(err)) err = derr
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_dfcg_vect