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File: psb_krylov_mod.f90 ! Interfaces for Krylov subspace iterative methods. ! Subroutine: psb_skrylov ! ! Front-end for the Krylov subspace iterations, real version ! ! Arguments: ! ! methd - character The specific method; can take the values: ! CG ! CGS ! BICG ! BICGSTAB ! BICGSTABL ! RGMRES ! ! a - type(psb_sspmat_type) Input: sparse matrix containing A. ! prec - class(psb_sprec_type) Input: preconditioner ! b - real,dimension(:) Input: vector containing the ! right hand side B ! x - real,dimension(:) 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. ! err - real (optional) Output: error estimate on exit ! itrace - integer(optional) Input: print an informational message ! with the error estimate every itrace ! iterations ! irst - integer(optional) Input: restart parameter for RGMRES and ! BICGSTAB(L) methods ! istop - integer(optional) Input: stopping criterion, or how ! to estimate the error. ! 1: err = |r|/|b| ! 2: err = |r|/(|a||x|+|b|) ! where r is the (preconditioned, recursive ! estimate of) residual ! Subroutine psb_skrylov(method,a,prec,b,x,eps,desc_a,info,itmax,iter,err,itrace,irst,istop,cond) use psb_base_mod use psb_prec_mod,only : psb_sprec_type, psb_dprec_type, psb_cprec_type, psb_zprec_type use psb_krylov_mod, psb_protect_name => psb_skrylov character(len=*) :: method Type(psb_sspmat_type), Intent(in) :: a Type(psb_desc_type), Intent(in) :: desc_a class(psb_sprec_type), intent(in) :: prec Real(psb_spk_), Intent(in) :: b(:) Real(psb_spk_), Intent(inout) :: x(:) Real(psb_spk_), Intent(in) :: eps integer, intent(out) :: info Integer, Optional, Intent(in) :: itmax, itrace, irst,istop Integer, Optional, Intent(out) :: iter Real(psb_spk_), Optional, Intent(out) :: err,cond interface subroutine psb_scg(a,prec,b,x,eps,& & desc_a,info,itmax,iter,err,itrace,istop,cond) use psb_base_mod, only : psb_desc_type, psb_sspmat_type, psb_spk_ use psb_prec_mod, only : psb_sprec_type type(psb_sspmat_type), intent(in) :: a type(psb_desc_type), intent(in) :: desc_a real(psb_spk_), intent(in) :: b(:) real(psb_spk_), intent(inout) :: x(:) real(psb_spk_), intent(in) :: eps class(psb_sprec_type), intent(in) :: prec integer, intent(out) :: info integer, optional, intent(in) :: itmax, itrace,istop integer, optional, intent(out) :: iter real(psb_spk_), optional, intent(out) :: err,cond end subroutine psb_scg subroutine psb_sbicg(a,prec,b,x,eps,& & desc_a,info,itmax,iter,err,itrace,istop) use psb_base_mod, only : psb_desc_type, psb_sspmat_type, psb_spk_ use psb_prec_mod, only : psb_sprec_type type(psb_sspmat_type), intent(in) :: a type(psb_desc_type), intent(in) :: desc_a real(psb_spk_), intent(in) :: b(:) real(psb_spk_), intent(inout) :: x(:) real(psb_spk_), intent(in) :: eps class(psb_sprec_type), intent(in) :: prec integer, intent(out) :: info integer, optional, intent(in) :: itmax, itrace,istop integer, optional, intent(out) :: iter real(psb_spk_), optional, intent(out) :: err end subroutine psb_sbicg subroutine psb_scgstab(a,prec,b,x,eps,& & desc_a,info,itmax,iter,err,itrace,istop) use psb_base_mod, only : psb_desc_type, psb_sspmat_type, psb_spk_ use psb_prec_mod, only : psb_sprec_type type(psb_sspmat_type), intent(in) :: a type(psb_desc_type), intent(in) :: desc_a real(psb_spk_), intent(in) :: b(:) real(psb_spk_), intent(inout) :: x(:) real(psb_spk_), intent(in) :: eps class(psb_sprec_type), intent(in) :: prec integer, intent(out) :: info integer, optional, intent(in) :: itmax, itrace,istop integer, optional, intent(out) :: iter real(psb_spk_), optional, intent(out) :: err end subroutine psb_scgstab Subroutine psb_scgstabl(a,prec,b,x,eps,desc_a,info,& &itmax,iter,err, itrace,irst,istop) use psb_base_mod, only : psb_desc_type, psb_sspmat_type, psb_spk_ use psb_prec_mod, only : psb_sprec_type Type(psb_sspmat_type), Intent(in) :: a Type(psb_desc_type), Intent(in) :: desc_a class(psb_sprec_type), intent(in) :: prec Real(psb_spk_), Intent(in) :: b(:) Real(psb_spk_), Intent(inout) :: x(:) Real(psb_spk_), Intent(in) :: eps integer, intent(out) :: info Integer, Optional, Intent(in) :: itmax, itrace, irst,istop Integer, Optional, Intent(out) :: iter Real(psb_spk_), Optional, Intent(out) :: err end subroutine psb_scgstabl Subroutine psb_srgmres(a,prec,b,x,eps,desc_a,info,& &itmax,iter,err,itrace,irst,istop) use psb_base_mod, only : psb_desc_type, psb_sspmat_type, psb_spk_ use psb_prec_mod, only : psb_sprec_type Type(psb_sspmat_type), Intent(in) :: a Type(psb_desc_type), Intent(in) :: desc_a class(psb_sprec_type), intent(in) :: prec Real(psb_spk_), Intent(in) :: b(:) Real(psb_spk_), Intent(inout) :: x(:) Real(psb_spk_), Intent(in) :: eps integer, intent(out) :: info Integer, Optional, Intent(in) :: itmax, itrace, irst,istop Integer, Optional, Intent(out) :: iter Real(psb_spk_), Optional, Intent(out) :: err end subroutine psb_srgmres subroutine psb_scgs(a,prec,b,x,eps,desc_a,info,& &itmax,iter,err,itrace,istop) use psb_base_mod, only : psb_desc_type, psb_sspmat_type, psb_spk_ use psb_prec_mod, only : psb_sprec_type type(psb_sspmat_type), intent(in) :: a type(psb_desc_type), intent(in) :: desc_a class(psb_sprec_type), intent(in) :: prec real(psb_spk_), intent(in) :: b(:) real(psb_spk_), intent(inout) :: x(:) real(psb_spk_), intent(in) :: eps integer, intent(out) :: info integer, optional, intent(in) :: itmax, itrace,istop integer, optional, intent(out) :: iter real(psb_spk_), optional, intent(out) :: err end subroutine psb_scgs end interface integer :: ictxt,me,np,err_act character(len=20) :: name info = psb_success_ name = 'psb_krylov' call psb_erractionsave(err_act) ictxt=psb_cd_get_context(desc_a) call psb_info(ictxt, me, np) select case(psb_toupper(method)) case('CG') call psb_scg(a,prec,b,x,eps,desc_a,info,& &itmax,iter,err,itrace,istop,cond) case('CGS') call psb_scgs(a,prec,b,x,eps,desc_a,info,& &itmax,iter,err,itrace,istop) case('BICG') call psb_sbicg(a,prec,b,x,eps,desc_a,info,& &itmax,iter,err,itrace,istop) case('BICGSTAB') call psb_scgstab(a,prec,b,x,eps,desc_a,info,& &itmax,iter,err,itrace,istop) case('RGMRES') call psb_srgmres(a,prec,b,x,eps,desc_a,info,& &itmax,iter,err,itrace,irst,istop) case('BICGSTABL') call psb_scgstabl(a,prec,b,x,eps,desc_a,info,& &itmax,iter,err,itrace,irst,istop) case default if (me == 0) write(psb_err_unit,*) trim(name),': Warning: Unknown method ',method,& & ', defaulting to BiCGSTAB' call psb_scgstab(a,prec,b,x,eps,desc_a,info,& &itmax,iter,err,itrace,istop) end select if(info /= psb_success_) 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 == psb_act_abort_) then call psb_error(ictxt) return end if end subroutine psb_skrylov