tpl_disjoint_sparse_table.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
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*/
 
 
# ifndef TPL_DISJOINT_SPARSE_TABLE_H
# define TPL_DISJOINT_SPARSE_TABLE_H
 
# include <bit>
# include <cassert>
# include <cstdlib>
# include <concepts>
# include <initializer_list>
# include <type_traits>
# include <vector>
# include <utility>
# include <algorithm>
# include <ah-concepts.H>
# include <tpl_array.H>
# include <tpl_dynList.H>
# include <ahFunction.H>
# include <ah-errors.H>
 
namespace Aleph
{
  template <typename F, typename T>
  concept DisjointSparseTableOp = Aleph::ClosedBinaryOp<F, T>;
 
  template <typename T, class Op>
    requires DisjointSparseTableOp<Op, T>
  class Gen_Disjoint_Sparse_Table
  {
    Array<T> data;         // original values: data[i] = a[i]
    Array<T> table;        // flattened 2D: table[k * n + i]
    size_t n = 0;          // number of logical elements
    size_t levels = 0;     // number of levels
 
    Op op;
 
    T & at(const size_t k, const size_t i) { return table(k * n + i); }
    const T & at(const size_t k, const size_t i) const
    {
      return table(k * n + i);
    }
 
    static constexpr size_t compute_levels(const size_t nn) noexcept
    {
      if (nn <= 1) return 0;
      return static_cast<size_t>(std::bit_width(nn - 1));
    }
 
    void build()
    {
      if (n <= 1)
        return;
 
      for (size_t k = 0; k < levels; ++k)
        {
          const size_t half = size_t{1} << k;
          const size_t block_sz = half << 1;
 
          for (size_t b = 0; b < n; b += block_sz)
            {
              const size_t mid = b + half;
              if (mid > n) break;
 
              // Suffix aggregates: from mid-1 going left to b
              at(k, mid - 1) = data(mid - 1);
              for (size_t i = mid - 1; i > b; --i)
                at(k, i - 1) = op(data(i - 1), at(k, i));
 
              // Prefix aggregates: from mid-going right
              if (mid < n)
                {
                  at(k, mid) = data(mid);
                  const size_t right_end = std::min(b + block_sz, n);
                  for (size_t i = mid + 1; i < right_end; ++i)
                    at(k, i) = op(at(k, i - 1), data(i));
                }
            }
        }
    }
 
    template <class Getter>
    void fill_data(Getter getter)
    {
      for (size_t i = 0; i < n; ++i)
        data(i) = getter(i);
    }
 
    template <class AlephIt>
    void fill_data_from_aleph_it(AlephIt it)
    {
      size_t i = 0;
      for (; it.has_curr(); it.next_ne())
        data(i++) = it.get_curr();
    }
 
  public:
    using Item_Type = T;
 
    Gen_Disjoint_Sparse_Table(const size_t num, const T & init_val,
                              Op oper = Op())
      : data(Array<T>::create(std::max(num, size_t{1}))),
        table(Array<T>::create(
          std::max(compute_levels(num) * num, size_t{1}))),
        n(num), levels(compute_levels(num)), op(oper)
    {
      fill_data([&init_val](size_t) { return init_val; });
      build();
    }
 
    Gen_Disjoint_Sparse_Table(std::initializer_list<T> il, Op oper = Op())
      : data(Array<T>::create(std::max(il.size(), size_t{1}))),
        table(Array<T>::create(
          std::max(compute_levels(il.size()) * il.size(), size_t{1}))),
        n(il.size()), levels(compute_levels(il.size())), op(oper)
    {
      auto it = il.begin();
      fill_data([&it](size_t) { return *it++; });
      build();
    }
 
    Gen_Disjoint_Sparse_Table(const Array<T> & values, Op oper = Op())
      : data(Array<T>::create(std::max(values.size(), size_t{1}))),
        table(Array<T>::create(
          std::max(compute_levels(values.size()) * values.size(),
                   size_t{1}))),
        n(values.size()), levels(compute_levels(values.size())), op(oper)
    {
      fill_data([&values](size_t i) { return values(i); });
      build();
    }
 
    Gen_Disjoint_Sparse_Table(const std::vector<T> & values,
                              Op oper = Op())
      : data(Array<T>::create(std::max(values.size(), size_t{1}))),
        table(Array<T>::create(
          std::max(compute_levels(values.size()) * values.size(),
                   size_t{1}))),
        n(values.size()), levels(compute_levels(values.size())), op(oper)
    {
      fill_data([&values](size_t i) { return values[i]; });
      build();
    }
 
    Gen_Disjoint_Sparse_Table(const DynList<T> & values, Op oper = Op())
      : data(Array<T>::create(std::max(values.size(), size_t{1}))),
        table(Array<T>::create(
          std::max(compute_levels(values.size()) * values.size(),
                   size_t{1}))),
        n(values.size()), levels(compute_levels(values.size())), op(oper)
    {
      fill_data_from_aleph_it(values.get_it());
      build();
    }
 
    Gen_Disjoint_Sparse_Table(const Gen_Disjoint_Sparse_Table &) = default;
 
    Gen_Disjoint_Sparse_Table(Gen_Disjoint_Sparse_Table &&) noexcept
      = default;
 
    Gen_Disjoint_Sparse_Table & operator=(const Gen_Disjoint_Sparse_Table &)
      = default;
 
    Gen_Disjoint_Sparse_Table & operator=(Gen_Disjoint_Sparse_Table &&)
      noexcept = default;
 
    T query(const size_t l, const size_t r) const
    {
      ah_out_of_range_error_if(r >= n)
        << "Gen_Disjoint_Sparse_Table::query: r=" << r << " >= n=" << n;
      ah_out_of_range_error_if(l > r)
        << "Gen_Disjoint_Sparse_Table::query: l=" << l << " > r=" << r;
 
      if (l == r)
        return data(l);
 
      const size_t k = static_cast<size_t>(std::bit_width(l ^ r)) - 1;
      return op(at(k, l), at(k, r));
    }
 
    T get(const size_t i) const
    {
      ah_out_of_range_error_if(i >= n)
        << "Gen_Disjoint_Sparse_Table::get: index " << i
        << " >= size " << n;
 
      return data(i);
    }
 
    [[nodiscard]] constexpr size_t size() const noexcept { return n; }
 
    [[nodiscard]] constexpr bool is_empty() const noexcept { return n == 0; }
 
    [[nodiscard]] constexpr size_t num_levels() const noexcept
    {
      return levels;
    }
 
    Array<T> values() const
    {
      auto ret = Array<T>::create(n);
      for (size_t i = 0; i < n; ++i)
        ret(i) = data(i);
      return ret;
    }
 
    void swap(Gen_Disjoint_Sparse_Table & other) noexcept
    {
      data.swap(other.data);
      table.swap(other.table);
      std::swap(n, other.n);
      std::swap(levels, other.levels);
      std::swap(op, other.op);
    }
  };
 
 
  template <typename T>
  struct Sum_Disjoint_Sparse_Table
      : public Gen_Disjoint_Sparse_Table<T, Aleph::plus<T>>
  {
    using Base = Gen_Disjoint_Sparse_Table<T, Aleph::plus<T>>;
    using Base::Base; // inherit all constructors
  };
 
  template <typename T>
  struct Product_Disjoint_Sparse_Table
      : public Gen_Disjoint_Sparse_Table<T, Aleph::multiplies<T>>
  {
    using Base = Gen_Disjoint_Sparse_Table<T, Aleph::multiplies<T>>;
    using Base::Base; // inherit all constructors
  };
 
} // end namespace Aleph
 
# endif /* TPL_DISJOINT_SPARSE_TABLE_H */