anchor.diff:         nvars,nclasses,nseqs,neff,seqs,err,err_string)
   
     if (err /= 0) then
  +     if(iproc == 0) write(0,*) 'ERROR ! cannot read from msa file'
        call mpi_wrapper_finalize(err)
        stop
     end if
  
positive.code:   close(udata)
  
    ! open output
  
    call units_open(trim(mode)//'.log','unknown',ulog,err)
    if(err /= 0) then
       if (iproc == 0) write(0,*) "error opening file ", trim(mode)//'.log'
  
negative.code:      call read_prm_unit(uprm,nvars,nclasses,&
            prm,data_format,err)
       if (err /= 0) then
          if(iproc == 0) write(0,*) 'ERROR ! cannot read from prm'
          call mpi_wrapper_finalize(err)
          stop
       end if
  