fstr_contact_assembly.f90

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!-------------------------------------------------------------------------------
! Copyright (c) 2019 FrontISTR Commons
! This software is released under the MIT License, see LICENSE.txt
!-------------------------------------------------------------------------------
module m_fstr_contact_assembly
  use hecmw
  use m_fstr
  use mcontactdef
  use m_fstr_contact_element
  use m_fstr_contact_elem_common, only: computetm_tt
  use m_fstr_contact_interference
  use m_fstr_contact_elem_alag
  use m_fstr_contact_damping
  implicit none
 
  public :: calc_contact_pair_refstiff
 
contains
 
  subroutine calc_contact_pair_refstiff(contact, diag, ndof, hecMESH)
    type(tcontact), intent(inout)        :: contact
    real(kind=kreal), intent(in)         :: diag(:)   
    integer(kind=kint), intent(in)       :: ndof
    type(hecmwst_local_mesh), intent(in) :: hecmesh
    
    integer(kind=kint) :: i, j, k, slave_node, master_node, nnode, ctsurf
    integer(kind=kint) :: idx_start, idx_end, n_slave
    integer(kind=kint) :: cgrp, ic, iss, outtype, fnodes(100)
    real(kind=kreal)   :: maxv
    real(kind=kreal)   :: a_rep, slave_reflen_sum
    real(kind=kreal)   :: elem(3, l_max_surface_node), r0(2)
 
    maxv = 0.0d0
 
    ! Loop over slave nodes
    do j = 1, size(contact%slave)
      slave_node = contact%slave(j)
      ! The mortar refStiff must be partition-invariant: skip GHOST(external) rows, whose
      ! diagonal is not fully assembled here. Every slave node is internal on exactly one
      ! rank, so the allreduce-MAX below still sees every fully-assembled diagonal.
      if( contact%method == contacts2s .and. slave_node > hecmesh%nn_internal ) cycle
      idx_start = ndof * (slave_node - 1) + 1
      idx_end = ndof * slave_node
      maxv = max(maxv, maxval(diag(idx_start:idx_end)))
    enddo
    
    ! Loop over master surfaces and nodes
    if( contact%method == contacts2s ) then
      ! Enumerate the master faces from the surface group instead of contact%master: with
      ! !PARTITION, CONTACT_OWNER=SLAVE a rank that owns no slave node takes no master surface
      ! at all (fstr_contact_init), so the diagonals of the master nodes it owns would never
      ! enter the max and refStiff would depend on the partition. The surface group items are
      ! present wherever the element is, so taking internal rows only on every rank lets the
      ! allreduce-MAX reproduce the serial value.
      cgrp = contact%surf_id2
      if( cgrp > 0 ) then
        do i = hecmesh%surf_group%grp_index(cgrp-1)+1, hecmesh%surf_group%grp_index(cgrp)
          ic = hecmesh%surf_group%grp_item(2*i-1)
          call getsubface( hecmesh%elem_type(ic), hecmesh%surf_group%grp_item(2*i), outtype, fnodes )
          nnode = getnumberofnodes( outtype )
          iss = hecmesh%elem_node_index(ic-1)
          do j = 1, nnode
            master_node = hecmesh%elem_node_item( iss + fnodes(j) )
            if( master_node > hecmesh%nn_internal ) cycle
            idx_start = ndof * (master_node - 1) + 1
            idx_end = ndof * master_node
            maxv = max(maxv, maxval(diag(idx_start:idx_end)))
          enddo
        enddo
      endif
    else
      do ctsurf = 1, size(contact%master)
        nnode = size(contact%master(ctsurf)%nodes)
        do j = 1, nnode
          master_node = contact%master(ctsurf)%nodes(j)
          idx_start = ndof * (master_node - 1) + 1
          idx_end = ndof * master_node
          maxv = max(maxv, maxval(diag(idx_start:idx_end)))
        enddo
      enddo
    endif
    
    ! Parallel reduction
    call hecmw_allreduce_r1(hecmesh, maxv, hecmw_max)
    
    ! Set reference stiffness for this contact pair
    contact%refStiff = maxv
 
    ! Mortar dimensional correction: the mortar penalty multiplies refStiff by the contact
    ! area, so refStiff is divided by a representative tributary area A_rep = (slave reflen)^2
    ! to make mu = nPenalty*refStiff a pressure density. The same nPenalty then gives the same
    ! effective stiffness as the NODE-SURF per-node form. reflen is taken from the slave element
    ! (the constraint is integrated on the slave surface). NODE-SURF pairs are left untouched.
    if( contact%method == contacts2s ) then
      ! Local slave reference-length sum and slave-face count (0 if this rank owns none).
      slave_reflen_sum = 0.0d0
      n_slave = 0
      if( associated(contact%slave_surf) ) n_slave = size(contact%slave_surf)
      do j = 1, n_slave
        nnode = size(contact%slave_surf(j)%nodes)
        do k = 1, nnode
          ctsurf = contact%slave_surf(j)%nodes(k)
          elem(1:3,k) = hecmesh%node(3*ctsurf-2:3*ctsurf)
        enddo
        call getelementcenter( contact%slave_surf(j)%etype, r0 )
        slave_reflen_sum = slave_reflen_sum + &
          getreferencelength( contact%slave_surf(j)%etype, nnode, r0, elem )
      enddo
      ! Reduced outside the slave_surf>0 gate (ranks owning no slave face must still join the
      ! collective) but inside the method gate. Slave faces are owned by exactly one rank, so the
      ! SUM reproduces the serial value on every rank.
      call hecmw_allreduce_r1(hecmesh, slave_reflen_sum, hecmw_sum)
      call hecmw_allreduce_i1(hecmesh, n_slave, hecmw_sum)
      a_rep = 0.0d0
      if( n_slave > 0 ) then
        a_rep = ( slave_reflen_sum / dble(n_slave) ) ** 2
        if( a_rep > 0.0d0 ) contact%refStiff = contact%refStiff / a_rep
      endif
    endif
 
    ! Report penalty settings
    if (hecmw_comm_get_rank() == 0) then
      write(*,'(A,A,A,1pE12.3,A,1pE12.3,A,1pE12.3)') "  Contact [", &
        trim(contact%pair_name), "] set penalty: normal & tied ", &
        contact%nPenalty * contact%refStiff, ", tangential ", &
        contact%tPenalty * contact%refStiff, ", refStiff ", contact%refStiff
    endif
 
  end subroutine calc_contact_pair_refstiff
 
  subroutine assemble_contact_force_residual(nnode,ndLocal,id_lagrange,ctNForce,ctTForce,conMAT)
    integer(kind=kint), intent(in)       :: nnode
    integer(kind=kint), intent(in)       :: ndLocal(nnode + 1)
    integer(kind=kint), intent(in)       :: id_lagrange
    real(kind=kreal), intent(in)         :: ctnforce((nnode+1)*3+1) 
    real(kind=kreal), intent(in)         :: cttforce((nnode+1)*3+1) 
    type(hecmwst_matrix), intent(inout)  :: conmat
 
    integer(kind=kint) :: i, inod, idx
 
    do i = 1, nnode + 1
      inod = ndlocal(i)
      idx = (inod-1)*3+1
      conmat%B(idx:idx+2) = conmat%B(idx:idx+2) + ctnforce((i-1)*3+1:(i-1)*3+3) + cttforce((i-1)*3+1:(i-1)*3+3)
    enddo
 
    ! Accumulate: several contributions can target the same Lagrange row (the caller
    ! zero-clears conMAT%B before the contact assembly).
    if( id_lagrange > 0 ) then
      conmat%B(conmat%NP*conmat%NDOF+id_lagrange) = &
      conmat%B(conmat%NP*conmat%NDOF+id_lagrange) + ctnforce((nnode+1)*3+1) + cttforce((nnode+1)*3+1)
    endif
 
  end subroutine assemble_contact_force_residual
 
  subroutine assemble_contact_force_output(nnode,ndLocal,ctNForce,ctTForce,cont_nforce,cont_fric)
    integer(kind=kint), intent(in)          :: nnode
    integer(kind=kint), intent(in)          :: ndlocal(nnode + 1)
    real(kind=kreal), intent(in)            :: ctnforce((nnode+1)*3+1) 
    real(kind=kreal), intent(in)            :: cttforce((nnode+1)*3+1) 
    real(kind=kreal), pointer, intent(inout) :: cont_nforce(:)    
    real(kind=kreal), pointer, optional, intent(inout) :: cont_fric(:) 
 
    integer(kind=kint) :: i, inod, idx
 
    do i = 1, nnode + 1
      inod = ndlocal(i)
      idx = (inod-1)*3+1
      cont_nforce(idx:idx+2) = cont_nforce(idx:idx+2) + ctnforce((i-1)*3+1:(i-1)*3+3)
      if( present(cont_fric) ) cont_fric(idx:idx+2) = cont_fric(idx:idx+2) + cttforce((i-1)*3+1:(i-1)*3+3)
    enddo
 
  end subroutine assemble_contact_force_output
 
  subroutine update_contact_multiplier( contact, coord, disp, ddisp, fcoeff, &
    hecMESH, hecLagMAT, gnt, ctchanged )
    type( tcontact ), intent(inout)      :: contact
    real(kind=kreal), intent(in)         :: coord(:)       
    real(kind=kreal), intent(in)         :: disp(:)        
    real(kind=kreal), intent(in)         :: ddisp(:)       
    real(kind=kreal), intent(in)         :: fcoeff         
    type(hecmwst_local_mesh), intent(in) :: hecmesh
    type(hecmwst_matrix_lagrange), intent(in) :: hecLagMAT
    real(kind=kreal), intent(inout)      :: gnt(2)         
    logical, intent(inout)               :: ctchanged
 
    integer(kind=kint)  :: slave, etype, master
    integer(kind=kint)  :: nn, i, cnt
    real(kind=kreal)    :: lgnt(2)
    integer(kind=kint)  :: ndLocal(l_max_elem_node+1)
    real(kind=kreal)    :: ctnforce(l_max_elem_node*3+3)
    real(kind=kreal)    :: cttforce(l_max_elem_node*3+3)
    real(kind=kreal)    :: max_jump_ratio, jump_ratio_local
    real(kind=kreal)    :: mut_old, mut_new, threthold
 
    cnt = 0
    lgnt(:) = 0.d0
    max_jump_ratio = 0.0d0
    ! ===== NODE-SURF multiplier update (per slave node) =====
    do i = 1, size(contact%slave)
      if(.not. is_contact_active(contact%states(i)%state)) cycle   ! only STICK/SLIP
 
      slave = contact%slave(i)
      master = contact%states(i)%surface
      nn = size(contact%master(master)%nodes)
      etype = contact%master(master)%etype
 
      ndlocal(1) = slave
      ndlocal(2:nn+1) = contact%master(master)%nodes(1:nn)
 
      ! Update multiplier and calculate forces
      call updatecontactmultiplier_alag(contact%states(i), ndlocal(1:nn+1), coord, disp, ddisp, &
        contact%nPenalty * contact%refStiff, contact%tPenalty * contact%refStiff, &
        fcoeff, contact%master(master), lgnt, ctchanged, ctnforce, cttforce, jump_ratio_local, contact%smoothing)
 
      ! Track maximum jump ratio
      max_jump_ratio = max(max_jump_ratio, jump_ratio_local)
 
      cnt = cnt + 1
    enddo
 
    if(cnt > 0) lgnt(:) = lgnt(:) / cnt
    gnt = gnt + lgnt
    
    call hecmw_allreduce_r1(hecmesh, max_jump_ratio, hecmw_max)
    
    ! Adjust tPenalty
    threthold = 100.d0
    if (max_jump_ratio > threthold) then
      mut_old = contact%tPenalty * contact%refStiff
      contact%tPenalty = contact%tPenalty * max(1.d0/dsqrt(threthold), 1.0d0/dsqrt(max_jump_ratio))
      mut_new = contact%tPenalty * contact%refStiff
      if (hecmw_comm_get_rank() == 0) then
        write(*,'(A,A,A,1pE12.3,A,1pE12.3,A)') "  Contact [", trim(contact%pair_name), &
          "] tangential penalty adjusted: ", mut_old, " -> ", mut_new, " (friction jump)"
      endif
    endif
      
  end subroutine update_contact_multiplier
 
  subroutine update_contact_multiplier_surfsurf( contact, coord, disp, ddisp, fcoeff )
    type( tcontact ), intent(inout)      :: contact
    real(kind=kreal), intent(in)         :: coord(:)       
    real(kind=kreal), intent(in)         :: disp(:)        
    real(kind=kreal), intent(in)         :: ddisp(:)       
    real(kind=kreal), intent(in)         :: fcoeff         
 
    integer(kind=kint)  :: i, g, r, a, nnode_s, unique_count
    integer(kind=kint)  :: maplist(max_n_intp), master_idxs(MAX_N_INTP)
    integer(kind=kint), allocatable :: sorted_idx(:)
    ! per-node-within-group quantities; the per-node lambda_n drives the normal path
    real(kind=kreal),   allocatable :: snode(:,:), nsnode(:,:,:), gapwnode(:,:), lambda_node(:,:)
    real(kind=kreal)    :: mu, lambda_new
    ! --- friction: per-node slip/normal, per-node basis, return mapping ---
    real(kind=kreal),   allocatable :: sigma_node(:,:,:), nacc_node(:,:,:)
    real(kind=kreal),   allocatable :: lam_t_cur(:,:,:)
    integer(kind=kint), allocatable :: fric_state_cur(:,:)
    real(kind=kreal)    :: nhat(3), t1(3), t2(3), nrm, dxi(2)
    real(kind=kreal)    :: rho_t, alpha, that(2), lam_t_new(2)
    integer(kind=kint)  :: fstate
 
    ! ===== mortar multiplier update (per slave segment) =====
    mu = contact%nPenalty * contact%refStiff
    rho_t = contact%tPenalty * contact%refStiff   ! tangential penalty, used only if fcoeff/=0
    do i = 1, size(contact%slave_surf)
      if( contact%slave_surf(i)%state == contactfree ) cycle
 
      call get_unique_map(contact%slave_surf(i), maplist, master_idxs, unique_count)
      nnode_s = size(contact%slave_surf(i)%nodes)
      allocate(snode(unique_count,nnode_s), nsnode(unique_count,nnode_s,24), gapwnode(unique_count,nnode_s))
      call getintgap(contact%slave_surf(i), contact%master, coord, disp, ddisp, &
                     unique_count, maplist, master_idxs, &
                     snode, nsnode, gapwnode)
 
      allocate(sorted_idx(unique_count), lambda_node(nnode_s,unique_count))
      if( fcoeff /= 0.d0 ) then
        ! Resolve the tangent warm-start (working -> begin -> 0/STICK) before the working
        ! buffer is rebuilt below. lambda_n resolution is identical to the fcoeff=0 path.
        allocate(lam_t_cur(2,nnode_s,unique_count), fric_state_cur(nnode_s,unique_count))
        call resolve_lambda_cur(contact%slave_surf(i), master_idxs, unique_count, nnode_s, sorted_idx, &
                                lambda_node, lam_t_cur, fric_state_cur)
      else
        call resolve_lambda_cur(contact%slave_surf(i), master_idxs, unique_count, nnode_s, sorted_idx, &
                                lambda_node)
      endif
 
      ! Per-node augmented update: lambda_node(a,g) += mu*gapwnode(g,a), clamped at 0.
      do g = 1, unique_count
        do a = 1, nnode_s
          lambda_new = lambda_node(a,g) + (mu * gapwnode(g,a))
          if( lambda_new < 0.d0 ) lambda_new = 0.d0
          lambda_node(a,g) = lambda_new
        enddo
      enddo
 
      ! Rebuild the working buffer from the active master set (ascending); BEGIN left it empty.
      contact%slave_surf(i)%lam_work_n = unique_count
      do r = 1, unique_count
        contact%slave_surf(i)%lam_work_id(r)  = master_idxs(sorted_idx(r))
        contact%slave_surf(i)%lam_work_val(1:nnode_s,r) = lambda_node(1:nnode_s,sorted_idx(r))
      enddo
 
      ! --- friction tangent update: per slave node, project the mortar slip onto the
      !     per-node tangent frame, return-map with cone radius fcoeff*lambda_node(a,g),
      !     and write lambda_t / fric_state into the working buffer. ---
      if( fcoeff /= 0.d0 ) then
        allocate(sigma_node(unique_count,nnode_s,3), nacc_node(unique_count,nnode_s,3))
        call gettangentslip(contact%slave_surf(i), contact%master, coord, disp, ddisp, &
                            maplist, sigma_node, nacc_node)
        do g = 1, unique_count
          do a = 1, nnode_s
            nrm = sqrt( nacc_node(g,a,1)**2 + nacc_node(g,a,2)**2 + nacc_node(g,a,3)**2 )
            ! Project the per-node slip onto the per-node orthonormal frame, then Coulomb
            ! return-map. rho_t*Dxi matches the per-node mu*gapwnode area weighting (both
            ! node-tributary integrated), so the averaged back-distribution cancels the area.
            if( nrm < 1.d-30 ) then
              dxi(1:2) = 0.d0
              nhat(1:3) = 0.d0
            else
              nhat(1:3) = nacc_node(g,a,1:3) / nrm
              call build_group_tangent_basis(nhat, t1, t2)
              dxi(1) = dot_product(t1(1:3), sigma_node(g,a,1:3))
              dxi(2) = dot_product(t2(1:3), sigma_node(g,a,1:3))
            endif
            fstate = fric_state_cur(a,g)
            call group_return_mapping(lam_t_cur(1:2,a,g), rho_t, dxi, fcoeff, lambda_node(a,g), &
                                      contact%eps_fric_band, lam_t_new, fstate, alpha, that, &
                                      update_state=.true.)
            lam_t_cur(1:2,a,g)  = lam_t_new(1:2)
            fric_state_cur(a,g) = fstate
          enddo
        enddo
        ! Write the tangent working buffer parallel to the rebuilt lambda_n (ascending master order).
        do r = 1, unique_count
          contact%slave_surf(i)%lam_work_t(1:2,1:nnode_s,r)  = lam_t_cur(1:2,1:nnode_s,sorted_idx(r))
          contact%slave_surf(i)%lam_work_fstate(1:nnode_s,r) = fric_state_cur(1:nnode_s,sorted_idx(r))
        enddo
        deallocate(sigma_node, nacc_node, lam_t_cur, fric_state_cur)
      endif
 
      deallocate(sorted_idx)
      deallocate(snode, nsnode, gapwnode, lambda_node)
    enddo
 
  end subroutine update_contact_multiplier_surfsurf
 
  subroutine update_tied_multiplier( contact, disp, ddisp, ctchanged )
    type( tcontact ), intent(inout)   :: contact
    real(kind=kreal), intent(in)      :: disp(:)        
    real(kind=kreal), intent(in)      :: ddisp(:)       
    logical, intent(inout)            :: ctchanged
 
    integer(kind=kint)  :: slave, etype, master
    integer(kind=kint)  :: nn, i, j, iSS
    real(kind=kreal)    :: dg(3), dgmax
    real(kind=kreal)    :: shapefunc(l_max_surface_node)
    real(kind=kreal)    :: edisp(3*l_max_elem_node+3)
    real(kind=kreal)    :: mu                          
 
    ! Calculate penalty from contact structure
    mu = contact%nPenalty * contact%refStiff
 
    do i= 1, size(contact%slave)
      if( .not. is_contact_active(contact%states(i)%state) ) cycle   ! only STICK/SLIP
      slave = contact%slave(i)
      edisp(1:3) = disp(3*slave-2:3*slave)+ddisp(3*slave-2:3*slave)
      master = contact%states(i)%surface
 
      nn = size( contact%master(master)%nodes )
      etype = contact%master(master)%etype
      do j=1,nn
        iss = contact%master(master)%nodes(j)
        edisp(3*j+1:3*j+3) = disp(3*iss-2:3*iss)+ddisp(3*iss-2:3*iss)
      enddo
      call getshapefunc( etype, contact%states(i)%lpos(1:2), shapefunc )
 
      ! normal component
      dg(1:3) = edisp(1:3)
      do j=1,nn
        dg(1:3) = dg(1:3)-shapefunc(j)*edisp(3*j+1:3*j+3)
      enddo
 
      contact%states(i)%multiplier(1:3) = contact%states(i)%multiplier(1:3) + mu*dg(1:3)
 
      ! check if tied constraint converged
      dgmax = 0.d0
      do j=1,(nn+1)*3
        dgmax = dgmax + dabs(edisp(j))
      enddo
      dgmax = dgmax/dble((nn+1)*3)
      do j=1,3
        if( dabs(dg(j))/dmax1(1.d0,dgmax) > 1.d-3 ) ctchanged = .true.
      enddo
 
    enddo
  end subroutine
 
  subroutine update_contact_tangentforce( contact )
    type( tcontact ), intent(inout)   :: contact
 
    integer(kind=kint)  :: i
 
    do i= 1, size(contact%slave)
      if( .not. is_contact_active(contact%states(i)%state) ) then
        contact%states(i)%tangentForce(1:3) = 0.d0
        contact%states(i)%tangentForce_trial(1:3) = 0.d0
        contact%states(i)%tangentForce_final(1:3) = 0.d0
      else
        contact%states(i)%tangentForce(1:3) = contact%states(i)%tangentForce_final(1:3)
      end if
      contact%states(i)%tangentForce1(1:3) = contact%states(i)%tangentForce(1:3)
    enddo
  end subroutine update_contact_tangentforce
 
  subroutine calcu_contact_stiffness_nodesurf( ctAlgo, contact, coord, disp, ddisp, iter, lagrange_array, &
    conMAT, hecLagMAT)
    integer(kind=kint), intent(in)             :: ctalgo
    type(tcontact), intent(inout)              :: contact
    real(kind=kreal), intent(in)               :: coord(:)        
    real(kind=kreal), intent(in)               :: disp(:)         
    real(kind=kreal), intent(in)               :: ddisp(:)        
    integer(kind=kint), intent(in)             :: iter
    real(kind=kreal), intent(in)               :: lagrange_array(:) 
    type(hecmwst_matrix), intent(inout)        :: conmat
    type(hecmwst_matrix_lagrange), intent(inout) :: hecLagMAT
 
    integer(kind=kint) :: ctsurf, nnode, ndLocal(21), etype
    integer(kind=kint) :: j, k, algtype, id_lagrange
    real(kind=kreal)   :: lagrange
    real(kind=kreal)   :: stiffness((l_max_surface_node+1)*3+1, (l_max_surface_node+1)*3+1)
    real(kind=kreal)   :: elecoord(3, l_max_surface_node)  
    real(kind=kreal)   :: eledisp(l_max_surface_node*3+3)  
    real(kind=kreal)   :: force(l_max_surface_node*3+3)    
    logical            :: is_contact_active_flag, is_damping_active_flag
 
    algtype = contact%algtype
 
    do j = 1, size(contact%slave)
 
      ! stick or sliding contact is active
      is_contact_active_flag = is_contact_active(contact%states(j)%state)
      ! damping is active
      is_damping_active_flag = contact%states(j)%state == contactnear .and. &
        &  is_damping_enabled(contact)
 
      if( .not. is_contact_active_flag .and. .not. is_damping_active_flag ) cycle
 
      ctsurf = contact%states(j)%surface
      etype = contact%master(ctsurf)%etype
      nnode = size(contact%master(ctsurf)%nodes)
      ndlocal(1) = contact%slave(j)
      ndlocal(2:nnode+1) = contact%master(ctsurf)%nodes(1:nnode)
 
      ! Prepare master node coordinates for ALagrange (deformed configuration)
      do k = 1, nnode
        elecoord(1:3, k) = coord(3*ndlocal(k+1)-2:3*ndlocal(k+1)) + disp(3*ndlocal(k+1)-2:3*ndlocal(k+1))
      enddo
 
      if( is_contact_active_flag ) then
 
        if( algtype == contactsslid .or. algtype == contactfslid ) then
 
          if( ctalgo == kcaslagrange ) then
            id_lagrange = contact%states(j)%id_lagrange
            lagrange = lagrange_array(id_lagrange)
            call getcontactstiffness_slag(contact%states(j), contact%master(ctsurf), iter, &
              contact%tPenalty, contact%fcoeff, lagrange, stiffness, smoothing_type=contact%smoothing)
 
            ! Assemble contact stiffness matrix of contact pair into global stiffness matrix
            call hecmw_mat_ass_contactlag(nnode, ndlocal, id_lagrange, contact%fcoeff, stiffness, conmat, heclagmat)
 
          else if( ctalgo == kcaalagrange ) then
            ! Build element displacement increment for consistent tangent evaluation
            eledisp(1:3) = ddisp(3*ndlocal(1)-2:3*ndlocal(1))
            do k = 1, nnode
              eledisp(k*3+1:k*3+3) = ddisp(3*ndlocal(k+1)-2:3*ndlocal(k+1))
            enddo
            call getcontactstiffness_alag(contact%states(j), contact%master(ctsurf), elecoord(:,1:nnode), &
              contact%nPenalty * contact%refStiff, contact%tPenalty * contact%refStiff, &
              contact%fcoeff, contact%symmetric, stiffness, force, &
              smoothing_type=contact%smoothing, edisp=eledisp(1:nnode*3+3), iter=iter, &
              slvpos=coord(3*ndlocal(1)-2:3*ndlocal(1)) + disp(3*ndlocal(1)-2:3*ndlocal(1)))
 
            ! Assemble contact stiffness matrix into global stiffness matrix
            call hecmw_mat_ass_elem(conmat, nnode+1, ndlocal, stiffness)
 
          end if
 
        else if( algtype == contacttied ) then
 
          if( ctalgo == kcaslagrange ) then
            do k = 1, 3
              id_lagrange = contact%states(j)%id_lagrange + k - 1
              lagrange = lagrange_array(id_lagrange)
 
              call gettiedstiffness_slag(contact%states(j), contact%master(ctsurf), k, stiffness, &
                contact%smoothing)
              ! Assemble contact stiffness matrix of contact pair into global stiffness matrix
              call hecmw_mat_ass_contactlag(nnode, ndlocal, id_lagrange, 0.d0, stiffness, conmat, heclagmat)
            enddo
 
          else if( ctalgo == kcaalagrange ) then
            call gettiedstiffness_alag(contact%states(j), contact%master(ctsurf), &
              contact%nPenalty * contact%refStiff, stiffness, force)
 
            ! Assemble contact stiffness matrix into global stiffness matrix
            call hecmw_mat_ass_elem(conmat, nnode+1, ndlocal, stiffness)
 
          end if
 
        endif
 
      else if( is_damping_active_flag ) then
        call getdampingstiffness(contact%states(j), contact%master(ctsurf), &
          contact%damp_alpha * contact%refStiff, contact%damp_gact, &
          stiffness, smoothing_type=contact%smoothing)
 
        ! Assemble full damping stiffness for slave+master contact element
        call hecmw_mat_ass_elem(conmat, nnode+1, ndlocal, stiffness)
 
      endif
 
    enddo
 
  end subroutine calcu_contact_stiffness_nodesurf
 
  subroutine calcu_contact_stiffness_surfsurf( ctAlgo, contact, coord, disp, ddisp, hecMAT )
    integer(kind=kint), intent(in)             :: ctAlgo
    type(tcontact), intent(inout)              :: contact
    real(kind=kreal), intent(in)               :: coord(:)        
    real(kind=kreal), intent(in)               :: disp(:)         
    real(kind=kreal), intent(in)               :: ddisp(:)        
    type(hecmwst_matrix), intent(inout)        :: hecmat
 
    integer(kind=kint) :: i, g, a, nnode_m, nnode_s, unique_count, ctsurf
    integer(kind=kint) :: ndlocal(l_max_surface_node+1)
    integer(kind=kint) :: maplist(MAX_N_INTP), master_idxs(MAX_N_INTP)
    real(kind=kreal),   allocatable :: stiff_n(:,:,:,:), stiff_t(:,:,:,:)
    logical,            allocatable :: active_n(:,:), active_t(:,:)
 
    do i = 1, size(contact%slave_surf)
      if( contact%slave_surf(i)%state == contactfree ) cycle
      if( ctalgo /= kcaalagrange ) cycle
 
      call get_unique_map( contact%slave_surf(i), maplist, master_idxs, unique_count )
      nnode_s = size(contact%slave_surf(i)%nodes)
      allocate(stiff_n(24,24,nnode_s,unique_count), active_n(nnode_s,unique_count))
 
      ! Element level: one stiffness block per (slave-surf node a, master group g) constraint.
      if( contact%fcoeff /= 0.d0 ) then
        allocate(stiff_t(24,24,nnode_s,unique_count), active_t(nnode_s,unique_count))
        call getcontactstiffness_alag_surfsurf( contact%slave_surf(i), contact%master, coord, disp, ddisp, &
          contact%nPenalty * contact%refStiff, contact%tPenalty * contact%refStiff, contact%fcoeff, &
          contact%symmetric, contact%eps_fric_band, unique_count, maplist, master_idxs, &
          stiff_n, active_n, stiff_t, active_t )
      else
        call getcontactstiffness_alag_surfsurf( contact%slave_surf(i), contact%master, coord, disp, ddisp, &
          contact%nPenalty * contact%refStiff, contact%tPenalty * contact%refStiff, contact%fcoeff, &
          contact%symmetric, contact%eps_fric_band, unique_count, maplist, master_idxs, &
          stiff_n, active_n )
      endif
 
      ! ===== Normal stiffness =====
      do g = 1, unique_count
        ctsurf = master_idxs(g)
        nnode_m = size(contact%master(ctsurf)%nodes)
        ndlocal(1:nnode_s) = contact%slave_surf(i)%nodes(1:nnode_s)
        ndlocal(nnode_s+1:nnode_s+nnode_m) = contact%master(ctsurf)%nodes(1:nnode_m)
        do a = 1, nnode_s
          if( .not. active_n(a,g) ) cycle
          call hecmw_mat_ass_elem(hecmat, nnode_s+nnode_m, ndlocal, stiff_n(:,:,a,g))
        enddo
      enddo
 
      ! ===== Friction consistent tangent, assembled in a second pass =====
      if( contact%fcoeff /= 0.d0 ) then
        do g = 1, unique_count
          ctsurf = master_idxs(g)
          nnode_m = size(contact%master(ctsurf)%nodes)
          ndlocal(1:nnode_s) = contact%slave_surf(i)%nodes(1:nnode_s)
          ndlocal(nnode_s+1:nnode_s+nnode_m) = contact%master(ctsurf)%nodes(1:nnode_m)
          do a = 1, nnode_s
            if( .not. active_t(a,g) ) cycle
            call hecmw_mat_ass_elem(hecmat, nnode_s+nnode_m, ndlocal, stiff_t(:,:,a,g))
          enddo
        enddo
        deallocate(stiff_t, active_t)
      endif
 
      deallocate(stiff_n, active_n)
    enddo
 
  end subroutine calcu_contact_stiffness_surfsurf
 
  subroutine calcu_contact_ndforce_nodesurf( purpose, ctAlgo, contact, coord, disp, ddisp, lagrange_array, &
    conMAT, CONT_NFORCE, CONT_FRIC )
    integer(kind=kint), intent(in)       :: purpose
    integer(kind=kint), intent(in)       :: ctAlgo
    type( tcontact ), intent(inout)      :: contact
    real(kind=kreal), intent(in)         :: coord(:)        
    real(kind=kreal), intent(in)         :: disp(:)         
    real(kind=kreal), intent(in)         :: ddisp(:)        
    real(kind=kreal), intent(in)         :: lagrange_array(:) 
    type(hecmwst_matrix), intent(inout)  :: conmat
    real(kind=kreal), pointer            :: cont_nforce(:)  
    real(kind=kreal), pointer            :: cont_fric(:)    
 
    integer(kind=kint) :: ctsurf, nnode, ndlocal(21)
    integer(kind=kint) :: j, k, algtype, id_lagrange
    real(kind=kreal)   :: ndcoord(21*3)
    real(kind=kreal)   :: ndu(21*3), nddu(21*3)
    real(kind=kreal)   :: lagrange
    real(kind=kreal)   :: ctnforce(21*3+1)
    real(kind=kreal)   :: cttforce(21*3+1)
    real(kind=kreal)   :: mu_n, mu_t
    logical            :: if_flag
    logical            :: is_contact_active_flag, is_damping_active_flag
    real(kind=kreal)   :: ctime, etime
    integer(kind=kint) :: if_type
 
    algtype = contact%algtype
    if_flag = (contact%if_type /= 0)
    if(if_flag)then
      ctime = contact%ctime
      etime = contact%if_etime
      if_type = contact%if_type
    end if
 
    do j = 1, size(contact%slave)
 
      ! stick or sliding contact is active
      is_contact_active_flag = is_contact_active(contact%states(j)%state)
      ! damping is active (residual only)
      is_damping_active_flag = (purpose == kctforresidual) .and. &
        contact%states(j)%state == contactnear .and. is_damping_enabled(contact)
 
      if( .not. is_contact_active_flag .and. .not. is_damping_active_flag ) cycle
 
      ctsurf = contact%states(j)%surface
      nnode = size(contact%master(ctsurf)%nodes)
      ndlocal(1) = contact%slave(j)
      ndlocal(2:nnode+1) = contact%master(ctsurf)%nodes(1:nnode)
      do k = 1, nnode+1
        nddu((k-1)*3+1:(k-1)*3+3) = ddisp((ndlocal(k)-1)*3+1:(ndlocal(k)-1)*3+3)
        ndu((k-1)*3+1:(k-1)*3+3) = disp((ndlocal(k)-1)*3+1:(ndlocal(k)-1)*3+3) + nddu((k-1)*3+1:(k-1)*3+3)
        ndcoord((k-1)*3+1:(k-1)*3+3) = coord((ndlocal(k)-1)*3+1:(ndlocal(k)-1)*3+3) + ndu((k-1)*3+1:(k-1)*3+3)
      enddo
 
      if( is_contact_active_flag ) then
 
        if(if_flag) call set_shrink_factor(ctime, contact%states(j), etime, if_type)
 
        ! --- Determine penalty parameters: zero for output (multiplier-only)
        if( ctalgo == kcaalagrange .and. purpose == kctforoutput ) then
          mu_n = 0.0d0
          mu_t = 0.0d0
        else
          mu_n = contact%nPenalty * contact%refStiff
          mu_t = contact%tPenalty * contact%refStiff
        endif
 
        if( algtype == contactsslid .or. algtype == contactfslid ) then
          ! Obtain contact nodal force vector of contact pair
          if(if_flag) call get_shrink_elemact_surf(contact%states(j),ndcoord, nnode)
 
          if( ctalgo == kcaslagrange ) then
            id_lagrange = contact%states(j)%id_lagrange
            lagrange = lagrange_array(id_lagrange)
            call getcontactnodalforce_slag(contact%states(j),contact%master(ctsurf),ndcoord,nddu,    &
              contact%tPenalty,contact%fcoeff,lagrange,ctnforce,cttforce,.true.,contact%smoothing)
 
          else if( ctalgo == kcaalagrange ) then
            id_lagrange = 0
            call getcontactnodalforce_alag(contact%states(j),contact%master(ctsurf),ndcoord,nddu,    &
              mu_n, mu_t, contact%fcoeff,contact%symmetric,ctnforce,cttforce,contact%smoothing)
 
          end if
 
          ! Assemble contact force
          if( purpose == kctforresidual ) then
            call assemble_contact_force_residual(nnode,ndlocal,id_lagrange,ctnforce,cttforce,conmat)
          else
            call assemble_contact_force_output(nnode,ndlocal,ctnforce,cttforce,cont_nforce,cont_fric)
          endif
 
        else if( algtype == contacttied ) then
 
          if( ctalgo == kcaslagrange ) then
            do k=1,3
              id_lagrange = contact%states(j)%id_lagrange + k - 1
              lagrange = lagrange_array(id_lagrange)
              contact%states(j)%multiplier(k) = lagrange
 
              call gettiednodalforce_slag(contact%states(j),contact%master(ctsurf),k,ndu, &
              &  lagrange,ctnforce,cttforce,contact%smoothing)
              if( purpose == kctforresidual ) then
                call assemble_contact_force_residual(nnode,ndlocal,id_lagrange,ctnforce,cttforce,conmat)
              else
                call assemble_contact_force_output(nnode,ndlocal,ctnforce,cttforce,cont_nforce)
              endif
            end do
 
          else if( ctalgo == kcaalagrange ) then
            id_lagrange = 0
            call gettiednodalforce_alag(contact%states(j),contact%master(ctsurf),ndu,    &
              mu_n, ctnforce,cttforce)
            if( purpose == kctforresidual ) then
              call assemble_contact_force_residual(nnode,ndlocal,id_lagrange,ctnforce,cttforce,conmat)
            else
              call assemble_contact_force_output(nnode,ndlocal,ctnforce,cttforce,cont_nforce)
            endif
 
          end if
 
        endif
 
      else if( is_damping_active_flag ) then
 
        call getdampingnodalforce(contact%states(j), contact%master(ctsurf), nddu, &
          contact%damp_alpha * contact%refStiff, contact%damp_gact, &
          ctnforce, cttforce, smoothing_type=contact%smoothing)
 
        ! Assemble damping force for slave+master contact element
        call assemble_contact_force_residual(nnode,ndlocal,0,ctnforce,cttforce,conmat)
 
      endif
 
    enddo
 
  end subroutine calcu_contact_ndforce_nodesurf
 
  subroutine calcu_contact_ndforce_exp( contact, coord, disp, ddisp, CONT_NFORCE, CONT_FRIC )
    type( tcontact ), intent(inout)      :: contact
    real(kind=kreal), intent(in)         :: coord(:)        
    real(kind=kreal), intent(in)         :: disp(:)         
    real(kind=kreal), intent(in)         :: ddisp(:)        
    real(kind=kreal), pointer            :: cont_nforce(:)  
    real(kind=kreal), pointer            :: cont_fric(:)    
 
    integer(kind=kint) :: ctsurf, nnode, ndLocal(21), j, k
    real(kind=kreal)   :: ndcoord(21*3), ndu(21*3), nddu(21*3)
    real(kind=kreal)   :: ctnforce(21*3+1), cttforce(21*3+1)
    real(kind=kreal)   :: tm(3,3*(l_max_surface_node+1)), tt(3,3*(l_max_surface_node+1))
 
    do j = 1, size(contact%slave)
      if( .not. is_contact_active(contact%states(j)%state) ) cycle
 
      ctsurf = contact%states(j)%surface
      nnode = size(contact%master(ctsurf)%nodes)
      ndlocal(1) = contact%slave(j)
      ndlocal(2:nnode+1) = contact%master(ctsurf)%nodes(1:nnode)
      do k = 1, nnode+1
        nddu((k-1)*3+1:(k-1)*3+3) = ddisp((ndlocal(k)-1)*3+1:(ndlocal(k)-1)*3+3)
        ndu((k-1)*3+1:(k-1)*3+3) = disp((ndlocal(k)-1)*3+1:(ndlocal(k)-1)*3+3) + nddu((k-1)*3+1:(k-1)*3+3)
        ndcoord((k-1)*3+1:(k-1)*3+3) = coord((ndlocal(k)-1)*3+1:(ndlocal(k)-1)*3+3) + ndu((k-1)*3+1:(k-1)*3+3)
      enddo
 
      call getcontactnodalforce_slag( contact%states(j), contact%master(ctsurf), ndcoord, nddu, &
        0.d0, 0.d0, contact%states(j)%multiplier(1), ctnforce, cttforce, .false., contact%smoothing )
 
      call computetm_tt( contact%states(j), contact%master(ctsurf), contact%fcoeff, &
        tm, tt, contact%smoothing )
      cttforce(:) = 0.d0
      cttforce(1:3*(nnode+1)) = -matmul(transpose(tm(1:3,1:3*(nnode+1))), &
        contact%states(j)%tangentForce_final)
 
      call assemble_contact_force_output( nnode, ndlocal, ctnforce, cttforce, cont_nforce, cont_fric )
    enddo
 
  end subroutine calcu_contact_ndforce_exp
 
  subroutine calcu_contact_ndforce_surfsurf( purpose, ctAlgo, contact, coord, disp, ddisp, &
    conMAT, CONT_NFORCE, CONT_FRIC )
    integer(kind=kint), intent(in)       :: purpose
    integer(kind=kint), intent(in)       :: ctAlgo
    type( tcontact ), intent(inout)      :: contact
    real(kind=kreal), intent(in)         :: coord(:)        
    real(kind=kreal), intent(in)         :: disp(:)         
    real(kind=kreal), intent(in)         :: ddisp(:)        
    type(hecmwst_matrix), intent(inout)  :: conmat
    real(kind=kreal), pointer            :: cont_nforce(:)  
    real(kind=kreal), pointer            :: cont_fric(:)    
 
    integer(kind=kint) :: i, g, a, j, nd, nnode_m, nnode_s, unique_count, ctsurf
    integer(kind=kint) :: ndlocal(l_max_surface_node+1)
    integer(kind=kint) :: maplist(MAX_N_INTP), master_idxs(MAX_N_INTP)
    real(kind=kreal),   allocatable :: ctnforce(:,:,:), cttforce(:,:,:)
    logical,            allocatable :: active_n(:,:), active_t(:,:)
 
    do i = 1, size(contact%slave_surf)
      if( contact%slave_surf(i)%state == contactfree ) cycle
      if( ctalgo /= kcaalagrange ) cycle
 
      call get_unique_map( contact%slave_surf(i), maplist, master_idxs, unique_count )
      nnode_s = size(contact%slave_surf(i)%nodes)
      allocate(ctnforce(24,nnode_s,unique_count), active_n(nnode_s,unique_count))
 
      ! Element level: one force vector per (slave-surf node a, master group g) constraint,
      ! already signed as the residual contribution.
      if( contact%fcoeff /= 0.d0 ) then
        allocate(cttforce(24,nnode_s,unique_count), active_t(nnode_s,unique_count))
        call getcontactnodalforce_alag_surfsurf( purpose, contact%slave_surf(i), contact%master, coord, disp, ddisp, &
          contact%nPenalty * contact%refStiff, contact%tPenalty * contact%refStiff, contact%fcoeff, &
          contact%symmetric, contact%eps_fric_band, unique_count, maplist, master_idxs, &
          ctnforce, active_n, cttforce, active_t )
      else
        call getcontactnodalforce_alag_surfsurf( purpose, contact%slave_surf(i), contact%master, coord, disp, ddisp, &
          contact%nPenalty * contact%refStiff, contact%tPenalty * contact%refStiff, contact%fcoeff, &
          contact%symmetric, contact%eps_fric_band, unique_count, maplist, master_idxs, &
          ctnforce, active_n )
      endif
 
      ! ===== Normal force =====
      do g = 1, unique_count
        ctsurf = master_idxs(g)
        nnode_m = size(contact%master(ctsurf)%nodes)
        ndlocal(1:nnode_s) = contact%slave_surf(i)%nodes(1:nnode_s)
        ndlocal(nnode_s+1:nnode_s+nnode_m) = contact%master(ctsurf)%nodes(1:nnode_m)
        do a = 1, nnode_s
          if( .not. active_n(a,g) ) cycle
          do j = 1, nnode_s + nnode_m
            nd = ndlocal(j)
            if( purpose == kctforresidual ) then
              conmat%B(3*nd-2:3*nd) = conmat%B(3*nd-2:3*nd) + ctnforce(3*j-2:3*j,a,g)
            else if ( purpose == kctforoutput ) then
              cont_nforce(3*nd-2:3*nd) = cont_nforce(3*nd-2:3*nd) + ctnforce(3*j-2:3*j,a,g)
            end if
          enddo
        enddo
      enddo
 
      ! ===== Friction force, assembled in a second pass =====
      if( contact%fcoeff /= 0.d0 ) then
        do g = 1, unique_count
          ctsurf = master_idxs(g)
          nnode_m = size(contact%master(ctsurf)%nodes)
          ndlocal(1:nnode_s) = contact%slave_surf(i)%nodes(1:nnode_s)
          ndlocal(nnode_s+1:nnode_s+nnode_m) = contact%master(ctsurf)%nodes(1:nnode_m)
          do a = 1, nnode_s
            if( .not. active_t(a,g) ) cycle
            do j = 1, nnode_s + nnode_m
              nd = ndlocal(j)
              if( purpose == kctforresidual ) then
                conmat%B(3*nd-2:3*nd) = conmat%B(3*nd-2:3*nd) + cttforce(3*j-2:3*j,a,g)
              else if( purpose == kctforoutput ) then
                cont_fric(3*nd-2:3*nd) = cont_fric(3*nd-2:3*nd) + cttforce(3*j-2:3*j,a,g)
              end if
            enddo
          enddo
        enddo
        deallocate(cttforce, active_t)
      endif
 
      deallocate(ctnforce, active_n)
    enddo
 
  end subroutine calcu_contact_ndforce_surfsurf
 
end module m_fstr_contact_assembly