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