This patch improves mate finding results by protecting mate scores from being forgotten in a later iteration. This applies especially to aborted searches, but also to completed iterations in e.g. `go depth` scenarios. The only visible change to the user is the final UCI info line.
The case of TB wins/losses was excluded from this patch on purpose. The reason is that in some corner cases related to rounding in some DTZ Syzygy EGTBs, later searches may turn a TB loss into a draw, for example. See #5175 and the example
```
info depth 5 seldepth 5 multipv 1 score cp -20000 nodes 122 nps 8714 hashfull 0 tbhits 26 time 14 pv h1b1 a7b6 f6e5 b6b1 e5f4 c8c3 f4g5 d7h7 g5f4 b1f5 f4f5 c3e5 f5g6 e5f4 g6h7 f4g5 h7h8 b8c7 h8h7 c7d6 h7h8 d6e5 h8h7 e5f6 h7h8 g5g7
info depth 6 seldepth 9 multipv 1 score cp 0 nodes 255 nps 18214 hashfull 0 tbhits 26 time 14 pv h1h2 d7d6 f6g5 a7e7
```
from #5414.
Matetrack for patch:
```
Using ./stockfish on matetrack.epd with --nodes 1000000
Engine ID: Stockfish dev-20260510-dbbc3ed1
Total FENs: 6554
Found mates: 3054
Best mates: 2224
```
This is slightly more/equal compared to master (3040 and 2224), see https://github.com/vondele/matetrack/blob/faf7cf3be95ab7dfdcde6e035de28a30887cd8a5/matetrack1000000.csv#L4368.
Passed STC non-reg:
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 108224 W: 27565 L: 27429 D: 53230
Ptnml(0-2): 212, 11755, 30064, 11847, 234
https://tests.stockfishchess.org/tests/view/6a00899e9392f0c31721406c
closes https://github.com/official-stockfish/Stockfish/pull/6816
No functional change
This does require the user to have set `/sys/kernel/mm/transparent_hugepage/shmem_enabled` to something other than `never` (unfortunately the default, at least on Ubuntu).
```
Result of 50 runs
==================
base (...kfish.master) = 1814244 +/- 4396
test (./stockfish ) = 1823756 +/- 3448
diff = +9512 +/- 5496
speedup = +0.0052
P(speedup > 0) = 0.9996
```
```
Performance counter stats for './stockfish bench':
237,561 dTLB-misses
5,783,003,231 cycles
Performance counter stats for './bins/stockfish.master bench':
2,219,832 dTLB-misses
5,932,779,255 cycles
```
closes https://github.com/official-stockfish/Stockfish/pull/6805
No functional change
I found these changes useful and natural when working on a patch to improve mate reporting. I can revert some of the changes if maintainers would prefer that. E.g. I am not sure whether `unset_bound_flags()` is worth defining.
closes https://github.com/official-stockfish/Stockfish/pull/6785
No functional change
Failed VVLTC non-regression
https://tests.stockfishchess.org/tests/view/69d562b84088e069540a2288
LLR: -2.96 (-2.94,2.94) <-1.75,0.25>
Total: 386998 W: 99181 L: 99760 D: 188057
Ptnml(0-2): 35, 35792, 122429, 35203, 40
Failed STC non-regression
https://tests.stockfishchess.org/tests/view/69f3c6601e5788938e86a99e
LLR: -2.93 (-2.94,2.94) <-1.75,0.25>
Total: 33696 W: 8492 L: 8795 D: 16409
Ptnml(0-2): 124, 4209, 8504, 3868, 143
Many thanks to Dubslow, Torom, ces42, Shawn, vondele, Disservin and others for discussion.
## Summary
The venerable small net has been around for quite some time now, and while the big net architecture has substantially advanced with TI, the small net has stayed with plain HalfKA. It therefore presents a few burdens: multiple net architectures to maintain, multiple nets to train, and a whole lot of templates to deal with the variable L1 size.
Locally I measure a slowdown of -2.5% in NPS with this branch – and it's probably more on non-AVX512 architectures – but a pure slowdown of that magnitude would lead to more dramatic losses (even at VVLTC) than exhibited in the above tests, suggesting that the small net's lower eval quality is deleterious.
Bonus: Shawn found this interesting PGN among the VVLTC games: https://lichess.org/study/hvo8jflc/OeTOityv `master` seems to misevaluate the fortress because all positions go to small net (the material difference is larger than the threshold).
closes https://github.com/official-stockfish/Stockfish/pull/6796
Bench: 2877007
Recent changes to this part of the code mean that the variable `completedDepth` is no longer neeeded. The only *functional* part of this patch is the effect on the thread voting formula. Basically, compared to master this patch raises the depth weight in the formula uniformly by 1. For very, very low depths this may have a tiny effect on thread selection compared to master. But in general we expect this patch to have no effect on game play at STC and LTC.
Passed STC SMP non-reg:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 284808 W: 72944 L: 72994 D: 138870
Ptnml(0-2): 351, 32192, 77370, 32138, 353
https://tests.stockfishchess.org/tests/view/69eddd011e5788938e86a075
closes https://github.com/official-stockfish/Stockfish/pull/6793
No functional change
Master in `pv()` incorrectly assumes that any root move with `i != pvIdx` has an exact score. This can lead to the suppression of bound flags for (a) root moves that have been partially searched in an iteration but do not end up to be best move, or (b) when an aborted search for `pvIdx > 0` leads to a new best move. This latter case is the cause for issue #6783.
Fixes#6783.
The bug in its incarnation (a) was independently discovered by @ciekce a couple of weeks ago, and we have jointly discussed a patch that fixes it. He is therefore a co-author of the bugfix part of this patch.
While at it, we also fix three minor oversights in the PV roll-back for aborted searches with a loss score:
* We only roll back the PV if the aborted search would report an exact score.
* Master inadvertently may have reported a bound for the rolled-back score+PV.
* We ensure a final UCI info line with the correct search depth and searched nodes statistics etc.
closes https://github.com/official-stockfish/Stockfish/pull/6784
No functional change
Co-Authored-By: Ciekce <44617491+Ciekce@users.noreply.github.com>
The core idea here is to greatly speed up the backwards insertion loop of the insertion sort. We can store up to 16 sorted moves and their values/scores in vectors. We obtain all moves with a smaller score (i.e., sorted later than the move-to-insert) as a mask, giving us something like `1111111111000000`. If we subtract one this gives us `1111111110111111` which can be can be used as an expand mask, to insert the new move.
Passed STC:
https://tests.stockfishchess.org/tests/view/69e9c9190e9667dd5a765853
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 45024 W: 11867 L: 11550 D: 21607
Ptnml(0-2): 101, 4938, 12142, 5205, 126
Local test:
```
Result of 50 runs
==================
base (...kfish.master) = 2026071 +/- 5124
test (./stockfish ) = 2083770 +/- 5964
diff = +57699 +/- 8535
speedup = +0.0285
P(speedup > 0) = 1.0000
```
closes https://github.com/official-stockfish/Stockfish/pull/6768
No functional change
Passed STC
https://tests.stockfishchess.org/tests/view/69e82e200e9667dd5a765631
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 115424 W: 29950 L: 29822 D: 55652
Ptnml(0-2): 318, 12712, 31544, 12800, 338
Passed AVX2-only STC
https://tests.stockfishchess.org/tests/view/69e953080e9667dd5a7657c0
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 134720 W: 34773 L: 34665 D: 65282
Ptnml(0-2): 344, 14958, 36694, 14974, 390
Now that our L1 size is much smaller, the overhead of tracking diffs for
`double_inc_update` is a larger share of the cost.
Interestingly ces42 measured a -0.9% slowdown locally (avxvnni build).
Meanwhile Torom and I find this branch to be 2% faster. I'm not sure exactly
what's going on but more tests may be in order
closes https://github.com/official-stockfish/Stockfish/pull/6776
No functional change
TRACKED_TOP previously used a shell pipeline (xargs, awk, sort) to extract
unique top-level directory/file names from SRCS and HEADERS. When invoking make
from cmd.exe on Windows, $(shell ...) uses cmd.exe rather than sh.exe, so the
pipeline fails because cmd.exe does not support Unix pipe syntax. Other MSYS2
tools (e.g. the compiler) work fine because they are invoked directly as
commands, not through a shell pipeline. This caused TRACKED_TOP to be empty, so
ln -s never ran and the per-arch temp_builds subdirectories were left without a
Makefile symlink, breaking the universal build with: "No rule to make target
'universal-object-nopgo'". Fixed by replacing the shell pipeline with pure GNU
make built-in functions (sort, foreach, firstword, subst) which have no shell
or PATH dependencies and work identically on Windows, Linux and macOS.
closes https://github.com/official-stockfish/Stockfish/pull/6762
No functional change
For quite some time SF has reported a too low final search depth in rare cases
(in multi-threaded search if a non-main thread was selected). Unfortunately,
the recent refactoring in #6704 means that this now happens for almost every
stopped search.
This PR fixes this issue, which was first spotted and reported by joergoster,
by ensuring that `rootDepth` always holds the last depth for which a search was
started.
Fixes#6756.
closes https://github.com/official-stockfish/Stockfish/pull/6761
No functional change.
Piece promotion is generated, and then type_of(promotion) is used to retrieve
the underlying type. The class Move provides .promotion_type() natively,
meaning we can cache the type directly and avoid extracting it indirectly
afterward. By extracting pt = m.promotion_type(); up front, we don't need to
call type_of(promotion) iteratively inside the assertions or conditions below.
closes https://github.com/official-stockfish/Stockfish/pull/6759
No functional change
This PR is a replacement for #6652 and takes into account the changes made to this part of the code since then.
In multiPV analysis master may suppress genuine proven mated-in scores, if the iteration for a secondary PV line is aborted. In very rare cases, it may also evict a proven mated-in score from the best PV line with a score from an incomplete iteration of a secondary PV line. This PR avoids both.
In addition, we allow best thread selection in multithreaded multiPV searches. This was originally disabled in #524.
Single PV searches are not affected by this patch at all.
Fixes#6642.
closes https://github.com/official-stockfish/Stockfish/pull/6728
No functional change.
LLR: 2.97 (-2.94,2.94) <0.00,2.00>
Total: 38400 W: 10057 L: 9749 D: 18594
Ptnml(0-2): 93, 4110, 10498, 4394, 105
https://tests.stockfishchess.org/tests/view/69d2073261a12cebe17edc04
compile time generation leads to sharing tables through the binary, resulting
in gain on fishtest, as well as reduced memory usage. The downside is slightly
longer compilation time.
Using pdep reduces table size 4x, and gains a little outside of fishtest as well.
closes https://github.com/official-stockfish/Stockfish/pull/6706
No functional change
In setup_benchmark, the variables evaluating the current ply simply mirror the
exact iterative progress of the string arrays loop (since ply just increments
by 1 with every pass). We can delete the separate integer assignment and
execute it securely within the loop declaration.
closes https://github.com/official-stockfish/Stockfish/pull/6732
No functional change
Fix MultiArray::at() which was marked noexcept despite delegating to
std::array::at() that throws on out-of-range. Per review feedback, at() now
keeps standard bounds-checking semantics (only noexcept removed), and
operator[] gains an assert for debug-mode safety.
All eight correction history lookups in search.cpp (correction_value and
update_correction_history) are switched from .at(us) to [us].
Passed STC:
https://tests.stockfishchess.org/tests/view/69de7a735c67bee7d241ff92
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 77536 W: 20031 L: 19860 D: 37645
Ptnml(0-2): 221, 8411, 21338, 8572, 226
closes https://github.com/official-stockfish/Stockfish/pull/6734
No functional change
We maintain support for quite a few x86 ISA extensions but relied on the end
user to select the binary that is best for their system. We can detect at
runtime which architecture to use, and ship a single binary (per OS/ISA
combination). This PR does so, maintaining performance.
This is what I've landed on after quite a few iterations. Basically, we build
each arch separately, use `cpuid` to select one, and jump to that arch's main
function. Some details:
- The preprocessor macro `UNIVERSAL_BINARY` is defined when building for the universal binary.
- The Makefile target `universal-object-[no]pgo` is added, which produces a `stockfish.o` in each arch's build directory.
- To prevent symbol collisions between the multiple builds, we `#define Stockfish Stockfish_[arch]`. Furthermore we wrap the `main` function in `namespace Stockfish { }`.
- We can still get PGO data by linking to a per-arch binary, with `Stockfish_x86_64_avx2::main` as `main`, and running `bench`.
- For arches not supported by the host we can use Intel SDE – this is what we do in CI.
- When embedding the NNUE, we use C++26/C23 `#embed` instead of `INCBIN`. The issue with `INCBIN` is that it injects assembly directives that we have no control over.
- To ensure there's only one copy of the networks in the final binary, we define the network data as weak symbols in each per-arch build. Then, in the final link, we add a special nnue_embed.cpp which provides strong symbols.
- This does require GCC 15. Statically linking libstdc++ allows the binary to still run on older OSes though. And latest msys2 already does static linking + is based off GCC 15.2.0
building can be as simple as
make -j profile-build ARCH=x86-64-universal
or using the sde if the host doesn't support all architectures supported in the
universal binary, and the default host compiler is not recent enough.
make -j profile-build ARCH=x86-64-universal RUN_PREFIX="/path/to/sde -future --" CXX=g++-15
This change is also integrated in CI, so universal binaries are available as
downloadable artifacts.
Next we could also do ARM64, especially Android (all Apple silicon users use
the same binary). It also might be worth getting this to work with clang.
closes https://github.com/official-stockfish/Stockfish/pull/6740
No functional change
In C++, all standard input streams (including std::istringstream) are initialized with the skipws format flag enabled by default. Because these stream objects are scoped locally and freshly constructed on each loop iteration, we are guaranteed that skipws is already active.
closes https://github.com/official-stockfish/Stockfish/pull/6719
No functional change
Conditions for no pawn pushes, non-pawn material and last captured piece are already such restrictive that we don't need to artificially set checkers bitboard for legal move generation.
Also moving the check for available pawn pushes at first place, as it should already filter about 90% of cases.
Passed STC and LTC non-regression tests.
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 171232 W: 44202 L: 44131 D: 82899
Ptnml(0-2): 466, 18809, 47023, 18824, 494
https://tests.stockfishchess.org/tests/view/69d3623b61a12cebe17ededa
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 55662 W: 14424 L: 14247 D: 26991
Ptnml(0-2): 38, 5479, 16609, 5678, 27
https://tests.stockfishchess.org/tests/view/69d64cada07a818b0a25f95e
And also neutral on 10k fixed games test with custom stalemate book.
Elo: 0.24 ± 0.9 (95%) LOS: 69.9%
Total: 10000 W: 4681 L: 4674 D: 645
Ptnml(0-2): 0, 87, 4819, 94, 0
nElo: 1.81 ± 6.8 (95%) PairsRatio: 1.08
https://tests.stockfishchess.org/tests/view/69d7e4183ca80bdf151d43b8
closes https://github.com/official-stockfish/Stockfish/pull/6715
Bench: 2984258
A bit tricky to identify, but in `apple-silicon` builds, specifying a value for
`SyzygyPath` could still lead to crashes at certain depths from a
SIGBUS/SIGSEGV.
This PR replaces the `std::count_if()` adjustment in `tbprobe.cpp`'s
`do_probe_table()` with an annotated handwritten loop, avoiding the clang/LTO
miscompilation behind the crash.
closes https://github.com/official-stockfish/Stockfish/pull/6721
No functional change.
the assert checks for `bestThreadDecisive && newThreadDecisive`. However `newThreadDecisive` is not guaranteed at this point, leading to assertion failures. This PR rearranges the conditions to ensure correctness.
closes https://github.com/official-stockfish/Stockfish/pull/6716
No functional change
