anchor.diff:  clater        if(ierr.ne.izero) return
   c
   clater        call iterate(
  -clater     &   alnz,pcg,zcg,ja,                                               ! sparse
  -clater     &   b,btot,bres,pvec,gvec1,gvec2,grav,                             ! force
  -clater     &   x,d,deld,dprev,dcur,id,iwink,wink,nsysdat,                     ! global
  +clater     &   alnz,pcg,zcg,dprev,ja,                                         ! sparse
  +clater     &   bextern,btraction,bgravity,bconcforce,bprestress,bintern,      ! force
  +clater     &   bresid,bwork,dispvec,nforce,grav,                              ! force
  +clater     &   x,d,deld,dcur,id,iwink,wink,nsysdat,                           ! global
   clater     &   dx,deldx,dxcur,idx,iwinkx,winkx,idslp,ipslp,                   ! slip
   clater     &   nfault,dfault,tfault,                                          ! fault
   clater     &   s,stemp,                                                       ! stiff
  
positive.code: c
  cdebug      write(6,*) "Hello from elastc_f!"
  c
        if(idout.ne.izero) open(kw,file=ofile,status="old",
       & access="append")
        if(idsk.eq.ione) open(kp,file=pfile,status="old",access="append")
        if(idsk.eq.itwo) open(kp,file=pfile,status="old",
       & form="unformatted",access="append")
        skc=iskopt.ge.izero.and.iskopt.ne.ione.and.numslp.ne.izero
        call fill(b,zero,neq)
        call fill(bres,zero,neq)
        call fill(btot,zero,neq)
        call fill(gvec1,zero,neq)
        call fill(pvec,zero,neq)
        call fill(pcg,zero,neq)
        call fill(zcg,zero,neq)
        call fill(deld,zero,ndof*numnp)
        call fill(deldx,zero,ndof*numnp)
        call fill(dcur,zero,ndof*numnp)
  
negative.code: clater        if(ierr.ne.izero) return
  c
  clater        call formdf_ld(
  clater     &   bintern,neq,                                                   ! force
  clater     &   x,d,dcur,numnp,                                                ! global
  clater     &   s,stemp,                                                       ! stiff
  clater     &   dmat,ien,lm,lmx,infiel,iddmat,ndmatsz,numelt,nconsz,           ! elemnt
  