anchor.diff:  
       ! further compress data into 'sparse' multiplicities
       n_multi = count(multi0 > 0)
  -    allocate(multi_z(n_multi),stat=err)
  -    allocate(multi(n_multi),stat=err)
  +    allocate(multi_z(0:n_multi),stat=err)
  +    allocate(multi(0:n_multi),stat=err)
  +    multi_z(0) = 0
  +    multi(0) = n_empty_bins
       k_ = 0
       do i_ = 1, nmax
          if (multi0(i_) > 0) then
  
positive.code:     integer(int32)              :: err
      integer(int32)              :: nmax
      integer(int32), allocatable :: multi0(:)
  
      ! compute multiplicities
      ! nmax is the largest number of samples in a bin
  
negative.code:   implicit none
  
    integer(int32)              :: n_data
    real(real64)                :: n_empty_bins
    real(real64)                :: alphabet_size
    integer(int32), allocatable :: multi_z(:)
  