No-Regression test with 8 threads, tc=15+0.15:
http://tests.stockfishchess.org/tests/view/5bc874ca0ebc592439f85938
LLR: 2.94 (-2.94,2.94) [-3.00,1.00]
Total: 24740 W: 3977 L: 3863 D: 16900 Elo +1.60
This was a cooperation between me and Michael Stembera:
-me recognizing SF having problems with resolving FH's efficiently at
high depths, thus starting some tests based on consecutive FH's.
-mstembera picking up the idea with first success at STC & LTC (so full
credits to him!)
-me suggesting how to resolve the issues pinpointed by S.G on PR #1768
and finally restricting the logic to the main thread so that it don't
regresses at multi-thread.
Enable numa machinery only for STRICTLY MORE than 8 threads. Reason for this
change is that nowadays SMP tests are always done with 8 threads. That is a
problem for multi-socket Windows machines running on fishtest.
The patch adds a small random component (+-1) to VALUE_DRAW for the evaluation
of draw positions (mostly 3folds). This random component is not static, but
potentially different for each visit of the node (hence derived from the node
counter). The effect is that in positions with many 3fold draw lines, different
lines are followed at each iteration. This keeps the search much more dynamic,
as opposed to being locked to one particular 3fold.
An example of a position where master suffers from 3fold-blindness and this patch
solves quickly is the famous TCEC game 53:
FEN: 3r2k1/pr6/1p3q1p/5R2/3P3p/8/5RP1/3Q2K1 b - - 0 51
master doesn't see that this is a lost position (draw eval up to depth 50) as
Qf6-e6 d4-d5 (found by patch at depth 23) leads to a loss.
The 3fold-blindness is more important at longer TC, the patch was yellow STC and
LTC, but passed VLTC:
Currently we update (track up) the pv even in the fail high case.
However most times in such cases the pv in the ply below remains unset
because there we have value == alpha and so finally we see truncated
pv's (=just one move) in fail high cases.
Of course tracking down these pv's (+sending them to the gui) comes at a
certian cost, but no-regression tests passed:
N.B.: Digging also into qsearch was tried in another version but seemed
not to pass the tests. This means that we don't always will get a pv
until the very tips.
Miguel Lahoz [Thu, 20 Sep 2018 07:12:12 +0000 (15:12 +0800)]
Simplify evaluation of blockers_for_king
Currently, we have two evaluation terms which account for pinned pieces.
One is for all pinned pieces in kingDanger computation and another for
just pinned pawns in ThreatByRank. We can increase the relevant bonus
for kingDanger calculation and do away with the ThreatByRank, which
seems to just add more complexity.
ttCapture can be assigned to only once outside of the main loop. The patch seems
functional at higher depths (seems possible in the case of non-legal TTmoves that
are captures).
31m059 [Mon, 8 Oct 2018 18:43:45 +0000 (14:43 -0400)]
Combo
This PR is a combination of two unrelated [0, 4] patches that appeared promising
but not quite strong enough to pass on their own. The combination initially failed
STC with a positive score after a long run, and the subsequent speculative LTC test
passed.
* tweak_threatOnQueen4 :
Increase the middlegame components of ThreatByMinor[QUEEN]
and ThreatByRook[QUEEN] by 15 each. Bryan's (@crossbr) analysis of CCC Bonus Game 10
inspired several tests on penalizing a queen with limited safe mobility. While
attempting to implement this idea, I noticed that when I did not include the queen's
current square in the calculations, the Elo gains seemed to vanish--and only then did
I have the idea to revisit ThreatByMinor[QUEEN] and ThreatByRook[QUEEN], adding a
corresponding value to each. Without Bryan's work, this test would never have been
submitted. I would also like to recognize the efforts and contributions of @SFisGOD,
who also vigorously worked on this idea.
* Use pure static eval for null move pruning :
This idea was directly re-purposed from a promising test by Jerry Donald Watson
(@jerrydonaldwatson) in August. It was also independently developed and tested by
Stefan Geschwentner (@locutus2) previously.
Thank you all!
Note by snicolet: I use this non-functional change patch
as a pretext to correct the wrong bench number I introduced
in the message of the previous commit.
These two simplifications appear to be affecting and/or offsetting each other.
Neither can be removed independently, but in combination they pass -3,1.
Storing unconditionally the current generation and bound is equivalent to master.
Part of the condition was added as a speed optimization in #429.
Here the branch is fully eliminated.
The multithreaded test was run after a plausible suggestion by @mstembera that the effect of this could be larger with many cores. The result seems to indicate this doesn't really matter on the 8core architecture abundantly available on fishtest.
This patch is a combinaison of two parameters tweaks patches which
have failed as strong yellows at LTC recently, by Alain Savard (Rocky640)
and Fabian Fichter (ianfab):
http://tests.stockfishchess.org/tests/view/5b8a71e60ebc592cf2749b1d
http://tests.stockfishchess.org/tests/view/5b81ce3b0ebc5902bdbb6585
The null move reduction formula in line 769 of search.cpp is quite convoluted
and full of mysterious magic constants at the moment, it would certainly be
nice to simplify it and/or gain more Elo from it:
Rocky640 [Fri, 31 Aug 2018 13:30:16 +0000 (09:30 -0400)]
Long Diagonal Tweaks
a) Reduce PSQT values along the long diagonals on non-central squares
and increase the LongDiagonal bonus accordingly. The effect is to penalise
bishops on the long diagonal which can not "see" the 2 central squares.
The "good" bishops still have more or less the same bonus as current master.
b) For a bishop on a central square, because of the "| s" term in the code,
the LongDiagonalBonus was always given. So while being there, remove the "| s"
and compensate the central Bishop PSQT accordingly.
protonspring [Wed, 29 Aug 2018 00:48:45 +0000 (02:48 +0200)]
Remove PawnsOnBothFlanks
It looks like PawnsOnBothFlanks can be removed from initiative().
A barrage of tests seem to confirm that the adjustment to -110
does not gain elo to offset any potential loss by removing
PawnsOnBothFlanks.
The fact that endgames with all the pawns on only one flank are
drawish is a well-known chess idea, so it seems quite strange that
this can be removed so easily without losing Elo.
In the past there had been attempts to improve on PawnsOnBothFlanks
with similar concepts (for instance using the pawn span value), but
the tests were at best neutral. Maybe Stockfish is now mature enough
that these refined ideas would work to replace PawnsOnBothFlanks?
MJZ1977 [Wed, 29 Aug 2018 00:27:47 +0000 (02:27 +0200)]
Fix bug with "excludedMove" for probcut
Bugfix: "excludedMove" has to be skipped in the probcut loop too.
If it is not skipped, the probcut can exit quickly with a wrong return
value corresponding to the excluded move. See the following forum
thread for a discussion:
https://groups.google.com/forum/?fromgroups=#!topic/fishcooking/GGithf_VwSU
Shrink the hash table of tablebases back to 4096 entries
There is no need to make this as large as 65536 just for the sake of the
single 7-man tablebase that happens to have the key 0xf9247fff. Idea for the
fix by Ronald de Man, who suggested simply to allow more buckets past the end.
We also implement Robin Hood hashing for the hash table, which takes the worst
-case search for full 7-man tablebases down from 68 to 11 probes (Also takes
the average probe length from 2.06 to 2.05). For a table with 8K entries, the
corresponding numbers would be worst-case from 9 to 4, with average from 1.30
to 1.29.
Ondrej Mosnacek [Tue, 28 Aug 2018 23:22:22 +0000 (01:22 +0200)]
Refactor pure static eval code
This commit tries to make the new pure static eval code more readable by
splitting up the nested assignments into separate lines and making a few
more cosmetic tweaks.
protonspring [Mon, 20 Aug 2018 16:29:46 +0000 (10:29 -0600)]
make DistanceRing more consistent
This is a non-functional change. By pre-incrementing minKingPawnDistance
instead of post-incrementing, we can remove this -1.
This also makes DistanceRing more consistent with the rest of stockfish
since it now holds an actual "distance" instead of a less natural distance-1.
In current master, PseudoAttacks[KING][ksq] == DistanceRingBB[ksq][0]
With this patch, it will be PseudoAttacks[KING][ksq] == DistanceRingBB[ksq][1]
ie squares at distance 1 from the king. This is more natural use of distance.
The current array size DistanceRingBB[SQUARE_NB][8] is still OK with the new
definition, because maximum distance between two squares on a chess board is
seven (for example Kh1 and a8).
I think that more elo can be found in tweaks of this parameters so I plan
to further try some "hand-tuning", including increasing/decreasing ratio of
two constants and making bonus assimetric to 0. Thx to @AndyGrant for helping
with github and @jerrydonaldwatson for original idea.
A recent commit introduced a decrease of the static evaluation of
an inner node dependent on the previous stat score, which finally
was also stored in the transposition table. Now only the unchanged
static evaluation are stored there.
Remark:
For the case that a static evaluation can be retrieved from the
transposition table the value is now used unchanged. Another test
which also applies the modification in this case failed:
http://tests.stockfishchess.org/tests/view/5b7af6df0ebc5902bdbae2f6
Follow-up for the previous patch: we use an affine formula to mix stats
and evaluation in search. The idea is to give a bonus if the previous
move of the opponent was historically bad, and a malus if the previous
move of the opponent was historically good.
More precisely, if x is the stat score of the previous move by the opponent,
we implement the following formulas to tweak the evaluation at an internal
node of the tree for our pruning decisions at this node:
if x = 0, use v' = eval(P)
if x > 0, use v' = eval(P) - 5 - x/1024
if x < 0, use v' = eval(P) + 5 - x/1024
For reference, the previous master had this simpler rule:
if x > 0, use v' = eval(P) - 10
if x <= 0, use v' = eval(P)
VoyagerOne [Thu, 16 Aug 2018 21:58:48 +0000 (23:58 +0200)]
Mix search stats with evaluation
Mix search stats with evaluation: if the opponent's move has a good historyStat,
then decrease the evaluation of the internal node a bit for the pruning decisions
during search.
• the use of the previous stat score can probably be simplified in lines 587 and 716
• we could try to use a continuous bonus based on the previous stat score, instead
of just a fixed offset of -10 when the opponent previous move was good.
----------
Comments by Stefan Geschwentner:
Interesting idea. Because only the eval in search is tweak this should only
influence the eval and static eval used at inner nodes, and not on the return
search value (which comes in the end from quiescence search), except through
saving in TT followed by a TT cutoff.
So essentialy this effects diverse pruning/reduction parts -- eval and static
eval are lowered for good opponent moves:
• tt cutoff (ttValue)
• improving (static eval)
• more razoring (eval)
• less futility pruning (eval)
• less null move pruning (eval + static eval) (but with little more depth)
• more probcut (static eval)
• more move futility pruning (static eval)
protonspring [Fri, 17 Aug 2018 08:19:32 +0000 (10:19 +0200)]
Simplify king file dependancy in evaluate_shelter()
Remove the special value we used for the file of the king in the
evaluate_shelter() function, and compensate by tweaking some of
the ShelterStrength[] array values.
We double in this patch the weight of the capture history table in the
local scoring of captures for move ordering.
The capture history table is indexed by the triplet (capturing piece,
capture square, captured piece) and gets information like "it seems to
have been historically good in that part of the search tree to capture
a pawn with a rook on g3, even if it seems to lose material", and affect
the normaly pure « Most Valuable Victim » ordering of captures.
Finished yellow at STC after 228842 games (posting a +1.36 Elo gain):
LLR: -2.95 (-2.94,2.94) [0.00,4.00]
Total: 228842 W: 50894 L: 50152 D: 127796
http://tests.stockfishchess.org/tests/view/5b714bb00ebc5902bdba332d
Alain SAVARD [Tue, 14 Aug 2018 06:31:56 +0000 (08:31 +0200)]
Remove pawncount array in imbalance
This is a natural follow up to last commit where values on the
QuadraticOurs diagonal and some piece value deltas were changed.
@Stefano80 tried to simplify the newly introduced pawncount array
using QuadraticOurs[1][1] =52 and a -30 adjustment on pawn values
So I started a 80000 30+0.3 SPSA on the QuadraticOurs diagonal and
on the piece values using @Stefano80 start values.
SPSA gave the new values QuadraticOurs[1][1] =38 and a -33 on pawn
values (the other changes on QuadraticOurs were kept, but were not
ignificant according to this test
http://tests.stockfishchess.org/tests/view/5b710ccb0ebc5902bdba2f27)
GuardianRM [Sun, 12 Aug 2018 16:40:03 +0000 (18:40 +0200)]
Non-linear bonus for pawn count
This patch introduces a non-linear bonus for pawns, along with some
(linear) corrections for the other pieces types.
The original values were obtained by a massive non-linear tuning of both
pawns and other pieces by GuardianRM, while Alain Savard and Chris Cain
later simplified the patch by observing that, apart from the pawn case, the
tuned corrections were in fact almost affine and could be incorporated in
our current code base via the piece values in types.h (offset) and the diagonal
of the quadratic matrix (slope). See discussion in PR#1725 :
https://github.com/official-stockfish/Stockfish/pull/1725
How to continue from there?
- Maybe the non-linearity for the pawn value could be somewhat tempered
again and a simpler linear correction for pawns would work?
Original patches:
- [Piece values](http://tests.stockfishchess.org/tests/view/5b6d2cc00ebc5902bdba02d5) by Stefano Cardanobile
- [Stat bonus](http://tests.stockfishchess.org/tests/view/5b6adbc90ebc5902bdb9da73) by Stefan Geschwentner
- [Rook on pawn](http://tests.stockfishchess.org/tests/view/5b62a95b0ebc5902bdb961c0) by Mark Tenzer
- [Hanging bonus](http://tests.stockfishchess.org/tests/view/5b5d2fa00ebc5902bdb90855) by Ivan Ilvec
- [ss tweak](http://tests.stockfishchess.org/tests/view/5b58b7240ebc5902bdb89025) by miguel-l
Simple razoring: depth 1 only, no distinction between PV / NonPV
We simplify the razoring logic by applying it to all nodes at depth 1 only.
An added advantage is that only one razor margin is needed now, and we treat
PV and Non-PV nodes in the same manner.
How to continue?
- There may be some conditions in which depth 2 razoring is beneficial.
- We can see whether the razor margin can be tuned, perhaps even with a
different value for PV nodes.
- Perhaps we can unify the treatment of PV and Non-PV nodes in other parts
of the search as well.
We are opting for this patch as the more logical and simple of the two,
and it appears to be no less strong. Thanks in particular to @DU-jdto
for input into this patch.
Miguel Lahoz [Thu, 9 Aug 2018 14:04:36 +0000 (22:04 +0800)]
Remove Condition For Passed Pawns
Currently, we do not consider pawns passed if there is another pawn of
the same color in front of them. It appears that this condition is not
necessary. The idea is that the doubled pawns are likely to be weak and
one of them will be likely captured anyway. On the other hand, if we do
somehow manage to promote a pawn, then the pawn behind it becomes passed
as well. In any case, the end result is we end up with an extra
potentially passed pawn. The current evaluation for passed pawns already
handles this case by also scaling down this effect.
Unify the "quiet" and "non-quiet" reduction rules for use at any kind of moves.
The idea behind it was that both rules reduce at similiar cases in master:
one directly for late previous moves and the other indirectly by using a
bad stat score which is used for most move sorting and so approximates the
late move condition.
For captures/promotions the old rule was triggered in 25% but the new
rule only for 3% of all cases (so now more reductions are done, whereas
for quiet moves reductions keep the same level).
Currently, we first calculate some bitboards at the top of Evaluation::space()
and then check whether we actually need them. Invert the ordering. Of course this
does not make a difference in current master because the constexpr bitboard
calculations are in fact done at compile time by any decent compiler, but I find
my version a bit healthier since it will always meet or exceed current implementation
even if we eventually change the spaceMask to something not contsexpr.
FauziAkram [Wed, 8 Aug 2018 15:48:06 +0000 (17:48 +0200)]
King Psqt Tuning
After a session of tuning for King Psqt I got some new values, which was later
tweaked manually by me Fauzi, to result in an Elo-gain patch which seems to scale
pretty well:
Introduce voting system for best move selction in multi-threads mode.
Joint work with Stefan Geschwentner, based on ideas introduced by
Michael Stembera.
Moves are upvoted by every thread using the margin to the minimum score
across threads and the completed depth.
First thread voting for the winner move is selected as best thread.
Passed STC, LTC. A further LTC test with only 4 threads failed with positive
score. A LTC with 31 threads was stopped with LLR 0.77 after 25k games to
avoid use of excessive resources (equivalent to 1.5M STC games).
Similar ideas were proposed by Michael Stembera 2 years ago #507, #508.
This implementation seems simpler and more understandable, the results
slightly more promising.
Further possible work:
1) Tweak of the formula using for assigning votes.
2) Use a different baseline for the score dependent part: maximum score
or winning probability could make more sense.
3) Assign votes in `Thread::Search` as iterations are completed and use
voting results to stop search.
4) Select best thread as the threads voting for best move with the highest
completed depth or, alternatively, vote on PV moves.
Marco Costalba [Sat, 28 Jul 2018 13:33:39 +0000 (15:33 +0200)]
Improve Stats definition
Use operator const T&() instead of operator T() to avoid possible
costly hidden copies of non-scalar nested types.
Currently StatsEntry has a single member T, so assuming
sizeof(StatsEntry) == sizeof(T) it happens to work, but it's
better to use the size of the proper entry type in std::fill.
Note that current code works because std::array items are ensured
to be allocated in contiguous memory and there is no padding among
nested arrays. The latter condition does not seem to be strictly
enforced by the standard, so be careful here.
Finally use address-of operator instead of get() to fully hide the
wrapper class StatsEntry at calling sites. For completness add
the arrow operator too and simplify the C++ code a bit more.
Same binary code as previous master under the Clang compiler.
This is the first patch teaching Stockfish how to use the 7-pieces
Syzygy tablebase currently calculated by Bujun Guo (@noobpwnftw) and
Ronald de Man (@syzygy1). The 7-pieces database are so big that they
required a change in the internal format of the files (technically,
some DTZ values are 16 bits long, so this had to be stored as wide
integers in the Huffman tree).
Here are the estimated file size for the 7-pieces Syzygy files,
compared to the 151G of the 6-pieces Syzygy:
```
7.1T ./7men_testing/4v3_pawnful (ongoing, 120 of 325 sets remaining)
2.4T ./7men_testing/4v3_pawnless
2.3T ./7men_testing/5v2_pawnful
660G ./7men_testing/5v2_pawnless
117G ./7men_testing/6v1_pawnful
87G ./7men_testing/6v1_pawnless
```
Some pointers to download or recalculate the tables:
Location of original files, by Bujun Guo:
ftp://ftp.chessdb.cn/pub/syzygy/
Bench: 5591925 (No functional change if SyzygyTB is not used)
----------------------
Comment by Leonardo Ljubičić (@DragonMist)
This is an amazing achievement, generating and being able to use 7 men syzygy
on the fly. Thank you for your efforts @noobpwnftw !! Looking forward how this
will work in real life, and expecting some trade off between gaining perfect
play and slow disc Access, but once the disc speed and space is not a problem,
I expect 7 men to yield something like 30 elo at least.
-----------------------
Comment by Michael Byrne (@MichaelB7)
This definitely has a bright future. I turned off the 50 move rule (ala ICCF
new rules) for the following position: `[d]8/8/1b6/8/4N2r/1k6/7B/R1K5 w - - 0 1`
This position is a 451 ply win for white (sans the 50 move rule, this position
was identified by the generator as the longest cursed win for white in KRBN v KRB).
This patch adds the tropism measure as a new term in the king danger variable.
Since we then trasform this variable as a Score via a quadratic formula, the
main effect of the patch is the positive correlation of the tropism measure
with some checks and pins information already present in the king danger code.
Miguel Lahoz [Fri, 27 Jul 2018 16:23:53 +0000 (00:23 +0800)]
Increase the mg->eg gradient for the PawnlessFlank malus
Just a change of value to S(19, 84). Also somewhat of a follow up
to the recent tweak in definition of KingFlank.
I tried a lot of other values before this, increasing and decreasing
but with little success, and before giving up I wanted to try tweaking
the middlegame and endgame values in the opposite directions. I guess
this is somewhat lucky.
The previous commit wouldn't compile on the Microsoft Virtual Studio C++ compiler. So use a more compatible style for the same idea (which we already use in numerous places of evaluate.cpp, for instance in line 563).
Under the Clang compiler, both versions generate exactly the same machine code (same md5 signatures for the two binaries).
Remove a popcount for HinderPassedPawn, and compensate by doubling
the bonus from S(4,0) to to S(8,0).
Maybe it was pure luck, but we got the idea of this Elo gaining patch by
seing the simplification attempt by Mike Whiteley in pull request #1703.
This suggests that whenever we have a passed evaluation simplification,
we should consider the possibility that the master bonus has become
slightly out of tune with time, and we should try a few Elo gaining [0..4]
tests by hand-tuning the master bonus.
Miguel Lahoz [Wed, 25 Jul 2018 16:11:51 +0000 (00:11 +0800)]
Tweak KingFlank when king is on edge files
This tweak excludes files D and E from the KingFlank bitboard when our
king is on the A or H files respectively. As far as I can tell, this
affects two things: the calculation for CloseEnemies and PawnlessFlank.
Aside from filtering out slightly less relevant attacks in the flank,
I suspect this helps with king prophylaxis, avoiding attacks and moving
towards the center when the pawns start to come off.
How to continue: Tweaking the two bonuses mentioned might give some
gain, although as far as I can tell, CloseEnemies is very sensitive to
even small changes.
I don't measure any speed-up on my system, with two parallel benches at depth 22:
Total time (ms) : 74989
Nodes searched : 144830258
Nodes/second : 1931353
master
Total time (ms) : 75341
Nodes searched : 144830258
Nodes/second : 1922329
testedpatch
And anyway, like Stefan Geschwentner, I don't think that a 0.3% speed-up would
be enough to pass a [0..5] LTC test -- as a first approximation, we have this
rule of thumb that 1% speed-up gives about 1 Elo point.
However, considering the facts that the reformatting by itself is interesting,
that this is your first green test and that you played by the rules by running
the SPRT[0..5] test before opening the pull request, I will commit the change.
I will only take the liberty to change the occurrences of safe in lines 590 and
591 to b, to make the code more similar to lines 584 and 585.
How to continue after this patch: there is now a slight semantic
overlap between the ThreatByPawnPush and the ThreatBySafePawn bonuses,
so hand-tuning either of these, or both at the same time, is natural.
This patch implements some idea by Alain Savard and Mike Whiteley taken from the perpertual renaming/reformatting thread.
This is a pure code cleaning patch (so no change in functionality), but I use it as a pretext to correct the bogus bench number that I introduced in the previous commit.
2) So there was a suspicion that the original fast passing LTC test which lead
us to accept the patch may have been a statistical accident, so we organized
a match against the previous master at LTC to get an Elo estimate for the
patch:
Replace the depth part in the reduction formula for higher depths
with a slower growing linear function. So for depth > 3 less reductions
are used.
What we can try next:
- move the break point to even higher depths
- tweak the slope for lower and higher depth
- even possibly use a further higher depth threshold for a another
slower growing function
Remove stronglyProtected Queen for ThreatByRook. Idea is that in the
current master the SliderOnQueen bonus and the see_ge() function do
something similar as ThreatByRook for Queen, so this patch removes
some redundancy, in that sense.
This is a non-functional simplification. We change replaces an 'OR'
and a lookup (rank_bb(ksq)) with a bitwise ~. This is fewer operations
and is probably faster.
This is a follow-up of the previous pull request (#1686) by Miguel.
We simplify the "Overload" bonus condition by re-using the "weak"
variable, which captures well the essence of the overload condition.
This may also be a small speed optimization because the weak variable
is in a register at this point of the code.
Miguel Lahoz [Thu, 19 Jul 2018 11:18:30 +0000 (19:18 +0800)]
Remove connectivity.
There seems to be some strange interaction between Overload and Connectivity.
Overload encourages us to not have too many defended and attacked pieces,
as this may expose us to various tactics. This feels somewhat like it is in
conflict with Connectivity, where pieces are defended preemptively.
Here I take the "pick one or the other" approach and just remove connectivity,
while strengthening the effect of Overload to compensate. The reasoning is that
if we defend our pieces preemptively, then it does get attacked, we want to do
something about it so we don't get penalized by Overload. On the other
hand, if it doesn't get attacked, then there's no need to defend it.
Use in addition the counter move history table for sorting quiet
check evasion moves in main and quiecence search. Also rename
"contHistory" to "continuationHistory" while there.
Miguel Lahoz [Mon, 16 Jul 2018 16:51:43 +0000 (00:51 +0800)]
Use single value for KingProtector.
After some recent big tuning session, the values for King Protector were
simplified to only be used on minor pieces. This patch tries to further
simplify by just using a single value, since current S(6,5) and S(5,6)
are close to each other. The value S(6,6) ended up passing, although
S(5,5) was also tried and failed STC.
Extend the bonus for Overload to cases where our side
has more than one attacker to a non pawn piece.
Based on an idea by Bryan in the forum. For instance,
now black gets the overload bonus in this position:
8/5R1k/6pb/p6p/P1N4P/1Pp5/2K3P1/2N4r b - - 6 46
because two black pieces are attacking the knight on c1
that is defended only by the king.
This was broken when cuckoo hashing was added, and
subtly broke (for example) lichess' Android application,
thus illustrating the original judgement was sound.
I think I reached the limit of the fishtest framework. It frequently
crashed at 2 million games already. The small values also moved a lot
throughout the entire tuning session though with smaller margin. The
passed danger and close enemies values seems the most sensitive (changing
close enemies alone to 6 failed before but now it passes), whether or not
they are close to optimal I don't know, but it seems some parameters are
also correlated to others.
In the current master, ThreatByKing is an array of two Scores, one for
when we have a single attack and one for when we have many. The latter
case is very rarely called during bench and was recently given a strange
negative value during a tuning run, as pointed out by @candirufish on
commit efd4ca2. Here, we simplify away this second case entirely, and
increase the remaining ThreatByKing to compensate.
Although I derived the parameter tweak independently, with the goal of
preserving the same average bonus, I later noticed that a very similar
Score had already been derived by an ongoing SPSA tuning session.
I therefore recognize @candirufish for first discovering these values.
I would also like to thank @Rocky640 for valuable feedback that pointed
me in the direction of ThreatByKing.
Ondrej Mosnáček [Sat, 9 Jun 2018 11:45:49 +0000 (13:45 +0200)]
Move PSQ score to Position
This patch simplifies Position::do_move() by moving the PSQ score from
StateInfo to Position and updating it inside the put/remove/move_piece
functions.
The downside is that there is now slightly more computation done in
Position::undo_move(), but the fishtest results are Elo neutral.
protonspring [Sun, 17 Jun 2018 02:26:25 +0000 (20:26 -0600)]
Remove make_bitboard()
In current master, the function make_bitboard() does nothing apart from
helping initialize the SquareBB[] array. This seems like an unnecessary
abstraction layer.
The advantage of make_bitboard() is we can define a bitboard, in a simple
and general way, not only from a single square but also from a list of
squares. It is more elegant, faster and readable than combining multiple
SquareBB explicitly, but the last complex use case in evaluation was
simplified away a few months ago.
If make_bitboard() becomes useful again to define complicated bitboards,
it will be easy enough to reintroduce it using this pull request as
an implementation reference.
Alain SAVARD [Sun, 24 Jun 2018 22:06:13 +0000 (18:06 -0400)]
Simplify HinderPassedPawn bonus
Make sure each piece is not scored more than once as a passed pawn "hinderer",
by scoring only the blockers along the passed pawn path. Inspired by TCEC Game 29.
Passed STC as a simplification
http://tests.stockfishchess.org/tests/view/5b3016d00ebc5902b2e58552
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 75388 W: 16656 L: 16641 D: 42091
Passed LTC as a simplification
http://tests.stockfishchess.org/tests/view/5b302ed90ebc5902b2e587fc
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 49157 W: 8460 L: 8386 D: 32311
Current master was also counting the number of attacks along a passed pawn path,
which might be misleading:
a) a defender might be counted many times for the same pawn path. For example a
White rook on a1 attacking a black pawn on a7 would score the bonus * 6 but
would be probably better placed on a8
b) a defender might be counted on different pawn paths and might be overloaded. For
example a Ke4 or Qe4 against pawns on d6 and f6 would score the bonus * 6.
Counting each blocker or attacker only once is more complicated, and does not help
either: http://tests.stockfishchess.org/tests/view/5b2ff1cb0ebc5902b2e582b2
After this small simplification, there might be ways to increase the HinderPassedPawn
penalty.
Give more incentive to king activity in the endgame by increasing the weight
of the "outflanking" variable from 8 to 12 in the function evaluate_initiative().
Michael An [Thu, 21 Jun 2018 01:05:27 +0000 (21:05 -0400)]
Fix GCC 8 cast warnings
Silences the following warnings when compiling with GCC 8.
The fix is to use an intermediate pointer to anonymous function:
```
misc.cpp: In function 'int WinProcGroup::get_group(size_t)':
misc.cpp:241:77: warning: cast between incompatible function types from 'FARPROC' {aka 'long long int (*)()'} to 'fun1_t' {aka 'bool (*)(_LOGICAL_PROCESSOR_RELATIONSHIP, _SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX*, long unsigned int*)'} [-Wcast-function-type]
auto fun1 = (fun1_t)GetProcAddress(k32, "GetLogicalProcessorInformationEx");
^
misc.cpp: In function 'void WinProcGroup::bindThisThread(size_t)':
misc.cpp:309:71: warning: cast between incompatible function types from 'FARPROC' {aka 'long long int (*)()'} to 'fun2_t' {aka 'bool (*)(short unsigned int, _GROUP_AFFINITY*)'} [-Wcast-function-type]
auto fun2 = (fun2_t)GetProcAddress(k32, "GetNumaNodeProcessorMaskEx");
^
misc.cpp:310:67: warning: cast between incompatible function types from 'FARPROC' {aka 'long long int (*)()'} to 'fun3_t' {aka 'bool (*)(void*, const _GROUP_AFFINITY*, _GROUP_AFFINITY*)'} [-Wcast-function-type]
auto fun3 = (fun3_t)GetProcAddress(k32, "SetThreadGroupAffinity");
^
```
DU-jdto [Wed, 13 Jun 2018 05:22:52 +0000 (15:22 +1000)]
Remove lmrDepth restriction on quiet see pruning
And tweak the threshold value. With this threshold and the current piece
values, this permits see pruning on quiets to be done up to an lmrDepth
of 9 (beyond that the threshold is below -QueenValueMg and see_ge will
pass unconditionally).
protonspring [Mon, 11 Jun 2018 08:17:03 +0000 (10:17 +0200)]
Optimize an expression in endgame.cpp
I believe using foward_file_bb() here is fewer instructions.
a) Fewer instructions and probably more clear (debatable).
b) Possible that a lookup is slower than a few local operations, but the
forward_file_bb table is probably used often enough that it is always
cached.
candirufish [Sun, 10 Jun 2018 08:53:05 +0000 (01:53 -0700)]
Simplify capture pruning margin formula
Using just `PawnValueEg * depth` as Capture Prune Margin. There was a bunch
of patches that passed recently regarding captures, maybe this part of the
master code redundant? The patch was tested as a simplification:
After several tests it seems best to increase contempt from 12 to 21. This does
not regress against contempt=0 and gives a gain of around 7-8 elo against SF 7
in comparison to current default contempt.
STC: Test for non-regression contempt=21 against contempt=0
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 71250 W: 13956 L: 13926 D: 43368
http://tests.stockfishchess.org/tests/view/5b19a58d0ebc5902ab9c3bfa
STC: Test contempt 21 against SF 7
ELO: 190.06 +-2.8 (95%) LOS: 100.0%
Total: 40000 W: 22608 L: 2676 D: 14716
http://tests.stockfishchess.org/tests/view/5b19a6520ebc5902ab9c3c0e
STC: Test master against SF 7 for comparison
ELO: 182.95 +-2.7 (95%) LOS: 100.0%
Total: 40000 W: 21905 L: 2595 D: 15500
http://tests.stockfishchess.org/tests/view/5b16f5bc0ebc59214346d5ca
LTC: Test for non-regression contempt=21 against contempt=0
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 47666 W: 6914 L: 6832 D: 33920
http://tests.stockfishchess.org/tests/view/5b1a170b0ebc5902ab9c3fde
LTC: Test contempt 21 against SF 7
ELO: 203.92 +-2.6 (95%) LOS: 100.0%
Total: 40000 W: 22447 L: 1340 D: 16213
http://tests.stockfishchess.org/tests/view/5b1a174b0ebc5902ab9c3fe1
LTC: Test master against SF 7 for comparison
ELO: 196.08 +-2.6 (95%) LOS: 100.0%
Total: 40000 W: 21639 L: 1191 D: 17170
http://tests.stockfishchess.org/tests/view/5b1a17e40ebc5902ab9c3fe4
candirufish [Wed, 6 Jun 2018 08:13:08 +0000 (10:13 +0200)]
Quiet move soft fail high bonus
Extra bonus for quiet move creating a huge soft fail high (triggered
in 21% of quiet bestmoves on a normal bench run). Pb00067 original idea
using PawnValueMg.
This has the property of raising alpha before calling qsearch(), thus
maybe giving some more cuts during qsearch(). The patch is equivalent
to the use of cycle detection inside qsearch() at depth 0, but is in
fact implemented by re-ordering code inside search(), which explains
the [0..4] bounds in the following tests.
STC (interrupted after 124250 games, with LLR=0.87):
http://tests.stockfishchess.org/tests/view/5b1500bd0ebc5902a8b420bf
LLR: 0.87 (-2.94,2.94) [0.00,4.00]
Total: 124250 W: 24973 L: 24470 D: 74807
After a helpful suggestion from AppVeyor support staff, moving the Stockfish
execution from ps to cmd seems to work. Alternative to PR #1624 tested in PR #1637.
Guenther Demetz [Mon, 4 Jun 2018 07:10:30 +0000 (09:10 +0200)]
Remove a superfluous subtrahend
The '- 1' subtrahend was introduced for guarding against null move
search at root, which would be nonsense. But this is actually already
guaranteed by the !PvNode condition. This followed from the discussion
in pull request 1609: https://github.com/official-stockfish/Stockfish/pull/1609