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>
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.
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.
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
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
The uci pv suppression and PV roll-back logic in master is a bit
convoluted, which makes it hard to reason about the code. In fact,
subtle bugs that led to wrong mated-in scores in game play or a mismatch
between bestmove and first PV move were only recently fixed. Moreover,
in master the uci pv output through `pv()` is called in four different
places.
This PR proposes to simplify this logic. In this patch, the PV is sent
to the GUI from within `iterative_deepening()` only (a) for fail
highs/lows or (b) when an iteration for a root move is completed. All
other PV outputs are now handled by `start_searching()`, just before the
bestmove extraction. This easily ensures that bestmove (and ponder move)
will always be in sync with the final PV output.
The only noticeable change to master is for multi-threaded searches that
do not involve `limits.depth`. Here master would show both the PV from
the aborted search in main thread, as well as the new PV from the
selected best thread. This patch would only show the latter.
While at it, we also remove the requirement to finish at least a depth 1
search and simplify the logic around stalemates/checkmates at root and
in particular avoid any PVs that start with `Move::none()`.
Passed STC non-reg:
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 72416 W: 18784 L: 18609 D: 35023
Ptnml(0-2): 200, 7762, 20127, 7901, 218
https://tests.stockfishchess.org/tests/view/69d3ef0c33584dad27b3c85a
closes https://github.com/official-stockfish/Stockfish/pull/6704
No functional change
Passed simp STC
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 29632 W: 7772 L: 7552 D: 14308
Ptnml(0-2): 76, 3155, 8147, 3349,
Id expect there to be a small speedup (bc the compiler can skip some
stores) but i haven’t tried to measure it
closes https://github.com/official-stockfish/Stockfish/pull/6688
No functional change
In master for various reasons the given ponder move may get out of sync
with (the second move of) the last PV sent to the GUI:
1. If a ponder move is extracted from the TT despite bestmove leading to
a game ending draw.
2. If a ponder move is extracted from the TT from a fail high/low, since
after the ponder move extraction no new PV is sent to the GUI.
3. If `syzygy_extend_pv()` from within the call to `pv()` changes the PV
after the ponder move has been selected.
4. If the PV roll-back to protect mated-in scores differs in the second
move from the final PV sent to the GUI.
This PR keeps ponder move and the last printed PV in sync.
Fixes#6676.
closes https://github.com/official-stockfish/Stockfish/pull/6679
No functional change
STC
```
LLR: 5.45 (-2.94,2.94) <0.00,2.00>
Total: 612192 W: 158602 L: 157260 D: 296330
Ptnml(0-2): 1634, 67783, 166027, 68911, 1741
```
@Torom measured:
```
sf_base = 2380902 +/- 1016 (95%)
sf_test = 2391426 +/- 1065 (95%)
diff = 10524 +/- 1336 (95%)
speedup = 0.44203% +/- 0.056% (95%)
```
I've verified that `_mm512_slli_epi16(v, 0)` gets optimized out in GCC
9+ and clang 4+. Added constants to types.h so that people messing
around with the layout of `Move` don't have to know about this part of
the code.
closes https://github.com/official-stockfish/Stockfish/pull/6670
No functional change
Ever since #5094 master only lets the main thread terminate `go mate`
searches, reverting the earlier improvement #1215.
This PR restores the old logic. So any thread that found a "mate in x"
can now stop the search.
To make this work robustly, we need to guard against inexact mate scores
in the best thread selection. In addition, in contrast to time limits,
the main thread may now not complete a d1 search for a mated-in
position.
In master an aborted d1 search may have a PV beginning with
`Move::none()`, in which case no thread selection is performed. See
#623. We fix this bug here by checking if `lastBestPV` is empty or not.
For interrupted d1 searches we now label mated-in scores as inexact.
While at it, we also simplify the logic for detecting if we can
terminate a go mate x search, using the fact that threads.stop can only
be false if we have a completed iteration with a valid score.
The PR has no effect on game play, but should slightly improve general
mate finding and speed up multi-threaded `go mate` searches.
We also add a corresponding matecheck run to the CI. This only involves
61 mates up to mate-in-2. Test runs with the first 50 or 100 mates from
`mates2000.epd` did at times not finish within 30 minutes on my fork or
in local tests, possibly due to search explosions for some mate-in-3
positions.
closes https://github.com/official-stockfish/Stockfish/pull/6668
No functional change
Currently, the engine updates each level of the continuation history stack (ply -1, -2, -3, etc.) with fixed weights that are independent of one another. The idea behind CMHC is to scale the magnitude of these updates based on the consistency of the move's performance across the stack.
By tracking how often a move has historically performed well (positive history) within the current continuation context, we can adjust the update magnitude dynamically. Moves that demonstrate "continuity" (appearing as strong candidates across multiple historical contexts) receive more significant updates, while unproven or inconsistent moves are dampened.
Passed STC:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 103264 W: 26954 L: 26541 D: 49769
Ptnml(0-2): 338, 11910, 26728, 12313, 343
https://tests.stockfishchess.org/tests/view/69a81702fac54339cf435a87
Passed LTC:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 47406 W: 12259 L: 11920 D: 23227
Ptnml(0-2): 22, 5052, 13237, 5349, 43
https://tests.stockfishchess.org/tests/view/69aab480bd35724e4b290498
closes https://github.com/official-stockfish/Stockfish/pull/6653
Bench: 2356418
Co-Authored-By: Daniel Samek <samekdaniel@email.cz>
This PR removes the variable threads.abortedSearch introduced in #4990 and
relies on threads.stop and completedDepth instead.
The logic in master is only guaranteed to work in single threaded search. For
multiple threads, as soon as threads.stop is set, some of the threads may abort
their search, and so their mated-in scores are not reliable.
Compared to master, this patch prevents unproven mated-in scores in these
multi-threaded scenarios:
in game play (when time management is used)
when the uci commands quit or stop are received
when maximum depth is reached
for go mate commands
The patch will change the bestmove in those very rare situations where the bug
occurs in master. This is because bestmove is taken from rootMoves[0].pv[0],
which will now no longer contain unproven mated-in PVs. In that sense the patch
is "functional". But of course, it does not change bench.
While at it, we also fix a bug in master that suppressed PV output for inexact
mated-in scores on receiving threads.stop. In cases where uciScore < score with
score not being a proven loss, and where the new bestmove was different from
the last completed iteration, this led to a bestmove output that did not match
the final PV (which was for an exact score).
Fixes#6293.
Fixes#6626.
closes https://github.com/official-stockfish/Stockfish/pull/6636
No functional change
