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
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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 <tpl_array.H>
# include <tpl_dynList.H>
# include <ahFunction.H>
# include <ah-errors.H>
 
namespace Aleph
{
  template <typename F, typename T>
  concept DisjointSparseTableOp =
      requires(const F& f, const T& a, const T& b)
        {
          { f(a, b) } -> std::convertible_to<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 */