anchor.diff:  c
         subroutine elastc(
        & alnz,pcg,zcg,dprev,ja,                                           ! sparse
  -     & bextern,btraction,bgravity,bconcforce,bprestress,bintern,bresid, ! force
  -     & bwork,dispvec,nforce,grav,                                       ! force
  +     & bextern,btraction,bgravity,bconcforce,bintern,bresid,bwork,      ! force
  +     & dispvec,nforce,grav,                                             ! force
        & x,d,deld,dcur,id,iwink,wink,nsysdat,                             ! global
        & ibond,bond,                                                      ! bc
        & dx,deldx,dxcur,diforc,idx,iwinkx,winkx,idslp,ipslp,idhist,       ! slip
        & fault,nfault,dfault,tfault,                                      ! fault
        & s,stemp,                                                         ! stiff
  -     & state,dstate,dmat,ien,lm,lmx,lmf,infiel,iddmat,npar,             ! elemnt
  +     & state,dstate,state0,dmat,ien,lm,lmx,lmf,infiel,iddmat,npar,      ! elemnt
        & ielno,iside,ihistry,pres,pdir,                                   ! tractn
        & prop,mhist,infmat,infmatmod,ismatmod,                            ! materl
        & gauss,sh,shj,infetype,                                           ! eltype
  
positive.code:       call fill(btraction,zero,neq*ntractflag)
        call fill(bgravity,zero,neq*ngravflag)
        call fill(bconcforce,zero,neq*nconcflag)
        call fill(bintern,zero,neq)
        call fill(deld,zero,ndof*numnp)
        call fill(deldx,zero,ndof*numnp)
        call fill(dcur,zero,ndof*numnp)
  
negative.code:       integer istatout(*)
        double precision alnz(*),pcg(*),zcg(*),dprev(*)
        double precision bextern(*),btraction(*),bgravity(*),bconcforce(*)
        double precision bintern(*),bresid(*),bwork(*),dispvec(*),grav(*)
        double precision x(*),d(*),deld(*),dcur(*),wink(*)
        double precision bond(*)
        double precision dx(*),deldx(*),dxcur(*),diforc(*),winkx(*)
        double precision fault(*),dfault(*),tfault(*)
        double precision s(*),stemp(*)
        double precision state(*),dstate(*),state0(*),dmat(*)
        double precision  pres(*),pdir(*)
        double precision prop(*)
        double precision gauss(*),sh(*),shj(*)
  