I improved MadChess 3.0 Beta’s Principal Variation Search (PVS) by consolidating two separate re-searches into one. In addition, I changed the null move implementation so it reduces the search horizon more aggressively if the current position’s static score far exceeds beta.
Previously, if a PVS search failed high, the engine would confirm the fail high first by restoring beta from bestScore + 1 to its original value and re-searching. If that also failed high, it restored the search horizon from a reduced value to its original value and re-searched. If that failed high the engine took a beta cutoff.
I simplified the code to a single re-search.
Null move now reduces more aggressively if the current position’s static score far exceeds beta.
This increased the playing strength of MadChess 3.0 Beta by 20 Elo.
| Feature | Category | Date | Commit1 | WAC2 | Elo Rating3 | Improvement |
|---|---|---|---|---|---|---|
| PVS and Null Move | Search | 2021 Feb 09 | f231dac | 285 | 2550 | +20 |
| Remove Aspiration Windows | Search | 2020 Dec 20 | 4b7963b | 290 | 2530 | +9 |
| Time Management | Search | 2020 Dec 19 | d143bb5 | 286 | 2521 | +8 |
| Crash Bug | Search | 2020 Aug 29 | 2d855ec | 288 | 2513 | +0 |
| King Safety | Evaluation | 2020 Aug 16 | 6794c89 | 288 | 2513 | +63 |
| Eval Param Tuning | Evaluation | 2020 Jul 23 | bef88d5 | 283 | 2450 | +30 |
| Late Move Pruning | Search | 2020 Feb 08 | 6f3d17a | 288 | 2420 | +29 |
| Piece Mobility | Evaluation | 2020 Feb 01 | 5c5d4fc | 282 | 2391 | +62 |
| Passed Pawns | Evaluation | 2018 Dec 27 | 103 | 279 | 2329 | +119 |
| Staged Move Generation | Search | 2018 Dec 15 | 93 | 275 | 2210 | +39 |
| History Heuristics | Search | 2018 Dec 03 | 84 | 275 | 2171 | +28 |
| Eval Param Tuning | Evaluation | 2018 Nov 24 | 75 | 272 | 2143 | +47 |
| Sophisticated Search Material and Piece Location |
Baseline | 2018 Nov 08 | 58 | 269 | 2096 | 0 |
- GitHub commit (hash) or Subversion source code revision (integer)
- Win At Chess position test, 3 seconds per position
- Bullet chess, 2 min / game + 1 sec / move
I work as a Software Architect at an insurance company. We're building a modern tech stack in the cloud using C#, Azure, ASP.NET Core, Angular, TypeScript, etc.