Slow save games - Solution proposal

[MadShadow-]

I found a few possibilities to speed up the save game process significantly.

In the serialize class, I changed the compression level from Best Compression to Best Speed. Files sizes are roughly the same, but without the attempts to perfect compression, the saving is a lot faster.

I also reduced the number of files created by collecting all npc and mob data in a respective single file. See npc and vob cpp.

!! This breaks load/save game compatibility to previous versions of course !!

To me my changes look innocent, but I might have introduced bugs. 🐞

Further thoughts

• interactive objects still end up as single files.. but they are way less, so don't have much impact in this world. In theory they could need the same improvement.
• The preview image is still a 4MB full screen image, which is unnecessary. (I've seen new commits regarding save game image size?)

[Try]

Hi, @MadShadow- !

Unfortunately, I have to reject this PR, most of it at least. We can't drop save-game compatibility support - this is strong most reason. While not really specified, but at least 1year old save should be compatible.

I changed the compression level from Best Compression to Best Speed

Is it really faster, or it's side effect of larger files? Can you provide numbers, to illustrate the performance gain?

[MadShadow-]

Is it really faster, or it's side effect of larger files? Can you provide numbers, to illustrate the performance gain?

I saved 3 games on each run. Left is MZ_BEST_COMPRESSION and right is MZ_BEST_SPEED. 3 seconds faster on my machine.

gamesession.cpp

void GameSession::save(Serialize &fout, std::string_view name, const Pixmap& screen) {
  SaveGameHeader hdr;
  hdr.version   = Serialize::Version::Current;
  hdr.name      = name;
  hdr.world     = wrld->name();

  using std::chrono::high_resolution_clock;
  using std::chrono::duration_cast;
  using std::chrono::duration;
  using std::chrono::milliseconds;

  auto t1 = high_resolution_clock::now();

  {
  time_t now = std::time(nullptr);
  tm*    tp  = std::localtime(&now);
  hdr.pcTime = *tp;
  }
  hdr.wrldTime  = wrldTime;
  hdr.playTime  = ticks;
  hdr.isGothic2 = Gothic::inst().version().game;

  // [savegame code]

  auto t2 = high_resolution_clock::now();

  /* Getting number of milliseconds as an integer. */
  auto ms_int = duration_cast<milliseconds>(t2 - t1);

  /* Getting number of milliseconds as a double. */
  duration<double, std::milli> ms_double = t2 - t1;

  std::cout << ms_int.count() << "ms\n";
  std::cout << ms_double.count() << "ms\n";
  }