rope_benchmark.cc

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/*
                          Aleph_w
 
  Data structures & Algorithms
  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
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
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  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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  SOFTWARE.
*/
 
#include <tpl_rope.H>
 
#include <chrono>
#include <cstdlib>
#include <iomanip>
#include <iostream>
#include <random>
#include <string>
#include <string_view>
 
using namespace Aleph;
 
namespace
{
using Clock = std::chrono::steady_clock;
 
double elapsed_ms(const Clock::time_point start)
{
  return std::chrono::duration<double, std::milli>(Clock::now() - start).count();
}
 
void print_row(const std::string & label, const double ms, const size_t final_size)
{
  std::cout << "  " << std::left << std::setw(28) << label << std::right
            << std::setw(10) << std::fixed << std::setprecision(2) << ms << " ms"
            << "   (final size " << final_size << ")\n";
}
 
void bench_string_append(const int chunk_count)
{
  const auto start = Clock::now();
  std::string s;
  for (int i = 0; i < chunk_count; ++i)
    {
      const char c = static_cast<char>('a' + (i % 26));
      s += std::string_view(&c, 1);
    }
  print_row("std::string::operator+=", elapsed_ms(start), s.size());
}
 
void bench_rope_concat(const int chunk_count)
{
  const auto start = Clock::now();
  Rope<char> r;
  for (int i = 0; i < chunk_count; ++i)
    {
      const char c = static_cast<char>('a' + (i % 26));
      r = r.concat(Rope<char>{std::string_view(&c, 1)});
    }
  print_row("Rope::concat (1 char/call)", elapsed_ms(start), r.size());
}
 
void bench_rope_concat_chunked(const int total_chars, const int chunk_size)
{
  const auto start = Clock::now();
  Rope<char> r;
  if (total_chars <= 0 or chunk_size <= 0)
    {
      print_row("Rope::concat (" + std::to_string(chunk_size) + " chars/call)",
                elapsed_ms(start), r.size());
      return;
    }
  std::string chunk(static_cast<size_t>(chunk_size), 'a');
  for (int built = 0; built < total_chars; )
    {
      const int remaining = total_chars - built;
      const int piece_size = remaining < chunk_size ? remaining : chunk_size;
      const std::string_view piece(chunk.data(), static_cast<size_t>(piece_size));
      r = r.concat(Rope<char>{piece});
      built += piece_size;
    }
  print_row("Rope::concat (" + std::to_string(chunk_size) + " chars/call)",
            elapsed_ms(start), r.size());
}
 
void bench_string_edits(const std::string & base, const int edit_count)
{
  const auto start = Clock::now();
  std::string s = base;
  const std::string marker = "<<edit>>";
  std::mt19937 rng(0xEDEDu);
  for (int i = 0; i < edit_count; ++i)
    {
      std::uniform_int_distribution<size_t> pos_dist(0, s.size());
      const size_t pos = pos_dist(rng);
      s.insert(pos, marker);
      s.erase(pos, marker.size());
    }
  print_row("std::string insert+erase", elapsed_ms(start), s.size());
}
 
void bench_rope_edits(const Rope<char> & base, const int edit_count)
{
  const auto start = Clock::now();
  Rope<char> r = base;
  const Rope<char> marker{std::string_view("<<edit>>")};
  std::mt19937 rng(0xEDEDu);
  for (int i = 0; i < edit_count; ++i)
    {
      std::uniform_int_distribution<size_t> pos_dist(0, r.size());
      const size_t pos = pos_dist(rng);
      r = r.insert(pos, marker);
      r = r.erase(pos, marker.size());
    }
  print_row("Rope insert+erase", elapsed_ms(start), r.size());
}
}  // namespace
 
int main(int argc, char * argv[])
{
  // Defaults large enough to actually reach the crossover where Rope's
  // typical O(log n) structural edits beat std::string's O(n) ones (see [2]
  // below); smaller sizes finish faster but may not show it.
  int chunk_count = 2000000;
  int edit_count = 5000;
 
  for (int i = 1; i < argc; ++i)
    {
      const std::string_view arg = argv[i];
      if (arg == "--chunks" and i + 1 < argc)
        chunk_count = std::atoi(argv[++i]);
      else if (arg == "--edits" and i + 1 < argc)
        edit_count = std::atoi(argv[++i]);
      else if (arg == "--help")
        {
          std::cout << "Usage: rope_benchmark [--chunks N] [--edits N]\n";
          return 0;
        }
    }
  if (chunk_count < 0)
    chunk_count = 0;
  if (edit_count < 0)
    edit_count = 0;
 
  std::cout << "\n=== Aleph::Rope vs std::string benchmark ===\n\n";
 
  std::cout << "[1] Large concatenation: " << chunk_count
            << " single-character appends\n";
  bench_string_append(chunk_count);
  bench_rope_concat(chunk_count);
  std::cout << "  (Rope's documented weak case -- every successful "
               "absorption re-copies the whole receiving leaf; see below "
               "for the pattern it is actually built for.)\n";
 
  constexpr int chunk_size = 1000;
  // Overflow-safe ceiling division: `chunk_count + chunk_size - 1` (the
  // usual `(a + b - 1) / b` idiom) can overflow `int` for a large
  // `--chunks` value before the division ever runs; `(chunk_count - 1) /
  // chunk_size + 1` reaches the same result without ever adding two
  // positive values that could each be close to INT_MAX.
  const int chunked_calls =
    chunk_count == 0 ? 0 : (chunk_count - 1) / chunk_size + 1;
  std::cout << "\n[1b] Same total size via " << chunked_calls
            << " chunked concatenations (" << chunk_size
            << " chars/call, Rope's intended "
               "usage pattern)\n";
  bench_rope_concat_chunked(chunk_count, chunk_size);
 
  std::cout << "\n[2] Structural editing: " << edit_count
            << " random middle insert+erase pairs on a "
            << chunk_count << "-character base sequence\n";
  const std::string base_string(static_cast<size_t>(chunk_count), 'x');
  const Rope<char> base_rope{std::string_view(base_string)};
  bench_string_edits(base_string, edit_count);
  bench_rope_edits(base_rope, edit_count);
 
  std::cout << "\nDone.\n";
  return 0;
}