Ciekce/Stormphrax - Githubissues

# Stormphrax [![License][license-badge]][license-link] [![GitHub release (latest by date)][release-badge]][release-link] [![Commits since latest release][commits-badge]][commits-link] ![LGBTQ+ friendly][lgbtqp-badge] ![trans rights][trans-rights-badge]

a work-in-progress UCI chess and chess960 engine, with NNUE evaluation trained from zero knowledge starting with random weights

this project is a continuation of my HCE engine Polaris

Strength

Version	CCRL 40/15	CCRL Blitz	CCRL 40/2 FRC	CEGT 40/4	MCERL
5.0.0	-	-	-	-	-
4.1.0	3484	-	3802	-	-
4.0.0	3476	3566	3775	3440	3542
3.0.0	3408	3491	3691	-	3495
2.0.0	3399	3481	3671	3339	3482
1.0.0	3318	3374	3540	3235	3346

Features

standard PVS with quiescence search and iterative deepening
- aspiration windows
- futility pruning
- history
- capture history
- 1-ply continuation history (countermove history)
- 2-ply continuation history (follow-up history)
- 4-ply continuation history
- history pruning
- internal iterative reduction
- killers (2 per ply)
- late move reductions
- late move pruning
- mate distance pruning
- multicut
- nullmove pruning
- reverse futility pruning
- probcut
- SEE move ordering and pruning
- singular extensions
- double extensions
- triple extensions
- various negative extensions
- Syzygy tablebase support
NNUE
- (768x4->1536)x2->1x8 architecture, horizontally mirrored
- trained from zero knowledge with reinforcement learning from a randomly-initialised network
BMI2 attacks in the bmi2 build, otherwise fancy black magic
- pext/pdep for rooks
- pext for bishops
lazy SMP
static contempt

To-do

make it stronger uwu

UCI options

Name	Type	Default value	Valid values	Description
`Hash`	integer	64	[1, 131072]	Memory allocated to the transposition table (in MB).
`Clear Hash`	button	N/A	N/A	Clears the transposition table.
`Threads`	integer	1	[1, 2048]	Number of threads used to search.
`UCI_Chess960`	check	`false`	`false`, `true`	Whether Stormphrax plays Chess960 instead of standard chess.
`UCI_ShowWDL`	check	`true`	`false`, `true`	Whether Stormphrax displays predicted win/draw/loss probabilities in UCI output.
`ShowCurrMove`	check	`false`	`false`, `true`	Whether Stormphrax starts printing the move currently being searched after a short delay.
`Move Overhead`	integer	10	[0, 50000]	Amount of time Stormphrax assumes to be lost to overhead when making a move (in ms).
`EnableWeirdTCs`	check	`false`	`false`, `true`	Whether unusual time controls (movestogo != 0, or increment = 0) are enabled. Enabling this option means you recognise that Stormphrax is neither designed for nor tested with these TCs, and is likely to perform worse than under X+Y.
`SyzygyPath`	string	`<empty>`	any path, or `<empty>`	Location of Syzygy tablebases to probe during search.
`SyzygyProbeDepth`	spin	1	[1, 255]	Minimum depth to probe Syzygy tablebases at.
`SyzygyProbeLimit`	spin	7	[0, 7]	Maximum number of pieces on the board to probe Syzygy tablebases with.
`EvalFile`	string	`<internal>`	any path, or `<internal>`	NNUE file to use for evaluation.

Builds

vnni512: requires BMI2, AVX-512 and VNNI (Zen 4/Cascade Lake-SP/Rocket Lake and up)
avx512: requires BMI2 and AVX-512 (Skylake-X, Cannon Lake)
avx2-bmi2: requires BMI2 and AVX2 and assumes fast pext and pdep (i.e. no Bulldozer, Piledriver, Steamroller, Excavator, Zen 1, Zen+ or Zen 2)
avx2: requires BMI and AVX2 - primarily useful for pre-Zen 3 AMD CPUs back to Excavator
sse41-popcnt: needs SSE 4.1 and popcnt - for older x64 CPUs

If in doubt, compare the avx2-bmi2 and avx2 binaries and pick the one that's faster. BMI2 will always be faster on Intel CPUs.

Alternatively, build the makefile target native for a binary tuned for your specific CPU (see below)

Note:

If you have an AMD Zen 1 (Ryzen x 1xxx), Zen+ (Ryzen x 2xxx) or Zen 2 (Ryzen x 3xxx) CPU, use the avx2 build even though your CPU supports BMI2. These CPUs implement the BMI2 instructions pext and pdep in microcode, which makes them unusably slow for Stormphrax's purposes.

Building

Requires Make and a competent C++20 compiler that supports LTO. GCC is not currently supported, so the usual compiler is Clang. MSVC explicitly does not work.

> make <BUILD> CXX=<COMPILER>

replace <COMPILER> with your preferred compiler - for example, clang++ or icpx
- if not specified, the compiler defaults to clang++
replace <BUILD> with the binary you wish to build - native/vnni512/avx512/avx2-bmi2/avx2/sse41-popcnt
- if not specified, the default build is native
if you wish, you can have Stormphrax include the current git commit hash in its UCI version string - pass COMMIT_HASH=on

By default, the makefile builds binaries with profile-guided optimisation (PGO). To disable this, pass PGO=off. When using Clang with PGO enabled, llvm-profdata must be in your PATH.

Credit

Stormphrax uses Fathom for tablebase probing, licensed under the MIT license, and a slightly modified version of incbin for embedding neural network files, under the Unlicense.

Stormphrax is tested on this OpenBench instance - thanks to all the people there, SP would be much weaker without your support :3

In no particular order, these engines have been notable sources of ideas or inspiration:

Stormphrax's current networks are trained with bullet. Previous networks were trained with Marlinflow.

The name "Stormphrax" is a reference to the excellent Edge Chronicles :)