FenwickByteF.hpp

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/*
 * Sux: Succinct data structures
 *
 * Copyright (C) 2019-2020 Stefano Marchini
 *
 *  This library is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU Lesser General Public License as published by the Free
 *  Software Foundation; either version 3 of the License, or (at your option)
 *  any later version.
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 3, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 *
 * Under Section 7 of GPL version 3, you are granted additional permissions
 * described in the GCC Runtime Library Exception, version 3.1, as published by
 * the Free Software Foundation.
 *
 * You should have received a copy of the GNU General Public License and a copy of
 * the GCC Runtime Library Exception along with this program; see the files
 * COPYING3 and COPYING.RUNTIME respectively.  If not, see
 * <http://www.gnu.org/licenses/>.
 */
 
#pragma once
 
#include "SearchablePrefixSums.hpp"
#include "Vector.hpp"
 
namespace sux::util {
 
template <size_t BOUND, AllocType AT = MALLOC> class FenwickByteF : public SearchablePrefixSums, public Expandable {
  public:
    static constexpr size_t BOUNDSIZE = ceil_log2_plus1(BOUND);
    static_assert(BOUNDSIZE >= 1 && BOUNDSIZE <= 64, "Leaves can't be stored in a 64-bit word");
 
  protected:
    Vector<uint8_t, AT> Tree;
    size_t Size;
 
  public:
    FenwickByteF() : Tree(0), Size(0) {}
 
    FenwickByteF(uint64_t sequence[], size_t size) : Tree(pos(size + 1) + 8), Size(size) {
        for (size_t i = 1; i <= Size; i++) bytewrite(&Tree[pos(i)], bytesize(i), sequence[i - 1]);
 
        for (size_t m = 2; m <= Size; m <<= 1) {
            for (size_t idx = m; idx <= Size; idx += m) {
                const uint64_t left = byteread(&Tree[pos(idx)], bytesize(idx));
                const uint64_t right = byteread(&Tree[pos(idx - m / 2)], bytesize(idx - m / 2));
                bytewrite(&Tree[pos(idx)], bytesize(idx), left + right);
            }
        }
    }
 
    virtual uint64_t prefix(size_t idx) {
        uint64_t sum = 0;
 
        while (idx != 0) {
            sum += byteread(&Tree[pos(idx)], bytesize(idx));
            idx = clear_rho(idx);
        }
 
        return sum;
    }
 
    virtual void add(size_t idx, int64_t inc) {
        while (idx <= Size) {
            bytewrite_inc(&Tree[pos(idx)], inc);
            idx += mask_rho(idx);
        }
    }
 
    using SearchablePrefixSums::find;
    virtual size_t find(uint64_t *val) {
        size_t node = 0;
 
        for (size_t m = mask_lambda(Size); m != 0; m >>= 1) {
            if (node + m > Size) continue;
 
            const uint64_t value = byteread(&Tree[pos(node + m)], bytesize(node + m));
 
            if (*val >= value) {
                node += m;
                *val -= value;
            }
        }
 
        return node;
    }
 
    using SearchablePrefixSums::compFind;
    virtual size_t compFind(uint64_t *val) {
        size_t node = 0;
 
        for (size_t m = mask_lambda(Size); m != 0; m >>= 1) {
            if (node + m > Size) continue;
 
            const uint64_t value = (BOUND << rho(node + m)) - byteread(&Tree[pos(node + m)], bytesize(node + m));
 
            if (*val >= value) {
                node += m;
                *val -= value;
            }
        }
 
        return node;
    }
 
    virtual void push(uint64_t val) {
        size_t p = pos(++Size);
        Tree.resize(p + 8);
        bytewrite(&Tree[p], bytesize(Size), val);
 
        if ((Size & 1) == 0) {
            for (size_t idx = Size - 1; rho(idx) < rho(Size); idx = clear_rho(idx)) {
                uint64_t inc = byteread(&Tree[pos(idx)], bytesize(idx));
                bytewrite_inc(&Tree[p], inc);
            }
        }
    }
 
    virtual void pop() { Size--; }
 
    virtual void grow(size_t space) { Tree.grow(pos(space) + 8); }
 
    virtual void reserve(size_t space) { Tree.reserve(pos(space) + 8); }
 
    virtual void trim(size_t space) { Tree.trim(pos(space) + 8); };
 
    virtual void trimToFit() { trim(Size); };
 
    virtual void resize(size_t space) { Tree.resize(pos(space) + 8); }
 
    virtual void size(size_t space) { Tree.size(pos(space) + 8); };
 
    virtual size_t size() const { return Size; }
 
    virtual size_t bitCount() const { return Tree.bitCount() - sizeof(Tree) * 8 - sizeof(*this) * 8; }
 
  private:
    static inline size_t bytesize(size_t idx) { return ((rho(idx) + BOUNDSIZE - 1) >> 3) + 1; }
 
    static inline size_t holes(size_t idx) {
        // Exhaustive benchmarking shows it is better to use no holes on (relatively) small trees,
        // but we expect holes to be handy again in (very) big trees
        if (BOUNDSIZE >= 32) return 0;
 
#ifdef HFT_DISABLE_TRANSHUGE
        return (idx >> (18 + (64 - BOUNDSIZE) % 8));
#else
        return (idx >> (28 + (64 - BOUNDSIZE) % 8));
#endif
    }
 
    static inline size_t pos(size_t idx) {
        idx--;
        constexpr size_t NEXTBYTE = ((BOUNDSIZE - 1) | (8 - 1)) + 1;
 
        constexpr size_t SMALL = ((BOUNDSIZE - 1) >> 3) + 1;
        constexpr size_t MEDIUM = NEXTBYTE - BOUNDSIZE + 1;
        constexpr size_t LARGE = MEDIUM + 8;
 
        constexpr size_t MULTIPLIER = 8 - SMALL - 1;
 
        return idx * SMALL + (idx >> MEDIUM) + (idx >> LARGE) * MULTIPLIER + holes(idx);
    }
 
    friend std::ostream &operator<<(std::ostream &os, const FenwickByteF<BOUND, AT> &ft) {
        os.write((char *)&ft.Size, sizeof(uint64_t));
        return os << ft.Tree;
    }
 
    friend std::istream &operator>>(std::istream &is, FenwickByteF<BOUND, AT> &ft) {
        is.read((char *)(&ft.Size), sizeof(uint64_t));
        return is >> ft.Tree;
    }
};
 
} // namespace sux::util