This is a non-functional simplification.
backmost_sq and frontmost_sq are redundant. It seems quite clear to always use frontmost_sq and use the correct color.
Non functional change.
We can remove the values in Pawns if we just use the piece arrays in Position. This reduces the size of a pawn entry. This simplification passed individually, and in concert with ps_passedcount100 (removes passedCount storage in pawns.).
STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 19957 W: 4529 L: 4404 D: 11024
http://tests.stockfishchess.org/tests/view/5cb3c2d00ebc5925cf016f0d
Combo STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 17368 W: 3925 L: 3795 D: 9648
http://tests.stockfishchess.org/tests/view/5cb3d3510ebc5925cf01709a
This is a non-functional simplification.
Simplification which removes the pawns connected array.
Instead of storing the values in an array, the values are
calculated real-time. This is about 1.6% faster on my machines.
Performance:
master ave nps: 159,248,672
patch ave nps: 161,905,592
STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 20363 W: 4579 L: 4455 D: 11329
http://tests.stockfishchess.org/tests/view/5c9925ba0ebc5925cfff79a6
Non functional change.
Adding a clamp function makes some of these range limitations a bit prettier and removes some #include's.
STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 28117 W: 6300 L: 6191 D: 15626
http://tests.stockfishchess.org/tests/view/5c9aa1df0ebc5925cfff8fcc
Non functional change.
This is a non-functional code style change.
If we add an accessor function for SquareBB we can consolidate all of the asserts. This is also a bit cleaner because all SquareBB accesses go through this method making future changes easier to manage.
STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 63406 W: 14084 L: 14045 D: 35277
http://tests.stockfishchess.org/tests/view/5c9ea6100ebc5925cfffc9af
No functional change.
This is a non-functional simplification/speedup.
The truth-table for popcount(support) >= popcount(lever) - 1 is:
------------------lever
------------------0-------1---------2
support--0------X-------X---------0
-----------1------X-------X---------X
-----------2------X-------X---------X
Thus, it is functionally equivalent to just do: support || !more_than_one(lever) which removes the expensive popcounts and the -1.
Result of 20 runs:
base (...h_master.exe) = 1451680 +/- 8202
test (./stockfish ) = 1454781 +/- 8604
diff = +3101 +/- 931
STC
LLR: 2.94 (-2.94,2.94) [-3.00,1.00]
Total: 35424 W: 7768 L: 7674 D: 19982
Http://tests.stockfishchess.org/tests/view/5c970f170ebc5925cfff5e28
No functional change.
A single popcount in evaluate.cpp replaces all openFiles stuff in pawns. It doesn't seem to affect performance at all.
STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 28103 W: 6134 L: 6025 D: 15944
http://tests.stockfishchess.org/tests/view/5b7d70a20ebc5902bdbb1999
No functional change.
I've gone through the RENAME/REFORMATTING thread and changed everything I could find, plus a few more. With this, let's close the previous issue and open another.
No functional change.
STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 51883 W: 11297 L: 10915 D: 29671
http://tests.stockfishchess.org/tests/view/5bf1e2ee0ebc595e0ae3cacd
LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 15859 W: 2752 L: 2565 D: 10542
http://tests.stockfishchess.org/tests/view/5bf337980ebc5902bcecbf62
Notes:
(1) The bonus value has not been carefully tested, so it may be possible
to find slightly better values.
(2) Plan is to now try adding similar restriction for pawns. I wanted to
include that as part of this pull request, but I was advised to do it as
two separate pull requests. STC is currently running here, but may not add
enough value to pass green.
Bench: 3679086
Preparation commit for the upcoming Stockfish 10 version, giving a chance to catch last minute feature bugs and evaluation regression during the one-week code freeze period. Also changing the copyright dates to include 2019.
No functional change
We don't need to pass the king square as an explicit parameter to the functions
king_safety() and do_king_safety() since we already pass in the position.
STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 69686 W: 14894 L: 14866 D: 39926
http://tests.stockfishchess.org/tests/view/5be84ac20ebc595e0ae3283c
No functional change.
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).
No functional change.
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.
STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 28291 W: 6287 L: 6178 D: 15826
http://tests.stockfishchess.org/tests/view/5b6c4b960ebc5902bdb9f256
LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 30717 W: 5256 L: 5151 D: 20310
http://tests.stockfishchess.org/tests/view/5b6c82980ebc5902bdb9f863
Bench: 4938285
Various king and pawn eval values tuned after 2 million games. Rounding
slightly adjusted.
LTC: http://tests.stockfishchess.org/tests/view/5b477a260ebc5978f4be3ed4
LLR: 2.95 (-2.94,2.94) [0.00,4.00]
Total: 32783 W: 5852 L: 5588 D: 21343
STC: http://tests.stockfishchess.org/tests/view/5b472d420ebc5978f4be3e4d
LLR: 3.23 (-2.94,2.94) [0.00,4.00]
Total: 44380 W: 10201 L: 9841 D: 24338
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.
Closes https://github.com/official-stockfish/Stockfish/pull/1670
bench: 5103722
I was able to get this to pass which reduces BlockedByPawn to one dimension
with NO distance from edge offset.
GOOD) It's more simple and may provide additional clarity for further
simplifications. Facilitates migrating unblocked to one dimension as well.
BAD) If there is indeed a distance component to BlockedStorm (may or may
not be the case), this obfuscates this component into ShelterStrength and
UnblockedStorm. This may be more convoluted. Also, it may be more convenient
to have each of the three arrays (ShelterStrength, BlockedStorm, and UnBlocked)
be the same size.
STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 96173 W: 19326 L: 19343 D: 57504
http://tests.stockfishchess.org/tests/view/5b04544d0ebc5914abc12965
LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 49818 W: 7441 L: 7363 D: 35014
http://tests.stockfishchess.org/tests/view/5b0487d50ebc5914abc12990
Closes https://github.com/official-stockfish/Stockfish/pull/1611
Bench: 5133208
We can view the patch version as adding some "undermining bonus" for
level pawns, when the defending side can not easily avoid the exchange
by advancing her pawn.
• Case 1) White b2,c3, Black a3,b3:
Black is breaking through, b2 deserves a penalty
• Case 2) White b2,c3, Black a3,c4:
if b2xa3 then White ends up with a weak pawn on a3
and probably a weak pawn on c3 too.
In either case, White can still not safely play b2-b3 and make a
phalanx with c3, which is the essence of a backward pawn definition.
Passed STC in SPRT[0, 4]:
LLR: -2.96 (-2.94,2.94) [0.00,4.00]
Total: 131169 W: 26523 L: 26199 D: 78447
http://tests.stockfishchess.org/tests/view/5aefa4d50ebc5902a409a151
ELO 1.19 [-0.38,2.88] (95%)
Passed LTC in SPRT[-3, 1]:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 24824 W: 3732 L: 3617 D: 17475
http://tests.stockfishchess.org/tests/view/5af04d3f0ebc5902a88b2e55
ELO 1.27 [-1.21,3.70] (95%)
Closes https://github.com/official-stockfish/Stockfish/pull/1584
How to continue from there?
There were some promising tests a couple of months ago about adding
a lever condition for king danger in evaluate.cpp, maybe it would
be time to re-try this after all the recent changes in pawns.cpp
Bench: 4773882
The two lines of code in the patch seem to be just as good as master.
1. We now only look at the current square to see if it is currently backward,
whereas master looks there AND further ahead in the current file (master would
declare a pawn "backward" even though it could still safely advance a little).
This simplification allows us to avoid the use of the difficult logic with
`backmost_sq(Us, neighbours | stoppers)`.
2. The condition `relative_rank(Us,s) < RANK_5` is simplified away.
Passed STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 68132 W: 14025 L: 13992 D: 40115
http://tests.stockfishchess.org/tests/view/5aedc97a0ebc5902a4099fd6
Passed LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 23789 W: 3643 L: 3527 D: 16619
http://tests.stockfishchess.org/tests/view/5aee4f970ebc5902a409a03a
Ideas for further work:
• The new code flags some pawns on the 5th rank as backward, which was not the
case in the old master. So maybe we should test a version with that included?
• Further tweaks of the backward condition with [0..5] bounds?
Closes https://github.com/official-stockfish/Stockfish/pull/1583
Bench: 5122789
When we are using the "Bitboard + Square" overloaded operators,
the compiler uses the interpediate SquareBB[s] to transform the
square into a Bitboard, and then calculate the result.
For instance, the following code:
```
b = pos.pieces(Us, PAWN) & s
```
generates in fact the code:
```
b = pos.pieces(Us, PAWN) & SquareBB[s]`
```
The bug introduced by Stéphane in the previous patch was the
use of `b = pos.pieces(Us, PAWN) & (s + Up)` which can result
in out-of-bounds errors for the SquareBB[] array if s in the
last rank of the board.
We coorect the bug, and also add some asserts in bitboard.h to
make the code more robust for this particular bug in the future.
Bug report by Joost VandeVondele. Thanks!
Bench: 5512000
Simplification: remove BlockedByKing from storm array and use a special rule.
The BlockedByKing section in the storm array is substantially similar to the
Unopposed section except for two extreme values V(-290), V(-274). Turns out
removing BlockedByKing and using a special rule for these two values shows
no Elo loss. All the other values in the BlockedByKing section are apparently
irrelevant. BlockedByKing now falls under unopposed which (to me) is a bit
more logical since there is no defending pawn on this file. Also, retuning
the Unopposed section may be another improvement.
GOOD) This is a simplification because the entire BlockedByKing section of
the storm array goes away reducing a few lines of code (and less values to
tune). This also brings clarity because the special rule is self documenting.
BAD) It takes execution time to apply the special rule. This should be negli-
gible because it is based on a template parameter and is boiled down to two
bitwise AND's.
STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 33470 W: 6820 L: 6721 D: 19929
http://tests.stockfishchess.org/tests/view/5ae7b6e60ebc5926dba90e13
LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 47627 W: 7045 L: 6963 D: 33619
http://tests.stockfishchess.org/tests/view/5ae859ff0ebc5926dba90e85
Closes https://github.com/official-stockfish/Stockfish/pull/1574
Bench: 5512000
-----------
How to continue after this patch?
This patch may open the possibility to move the special rule to evaluate.cpp
in the evaluate::king() function, where we could refine the rule using king
danger information. For instance, with a king in H2 blocking an opponent pawn
in H3, it may be critical to know that the opponent has no safe check in G2
before giving the bonus :-)
Remove the distinction between the king file and the two neighbours
files in the ShelterStrength[] array. Instead we initialize the safety
variable in the evaluate_shelter() function with a -10 penalty if our
king is on a semi-open file (ie. if our king is on a file without a pawn
protection).
Also rename shelter_storm() to evaluate_shelter() while there.
STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 23153 W: 4795 L: 4677 D: 13681
http://tests.stockfishchess.org/tests/view/5adcb83d0ebc595ec7ff8aa7
LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 25728 W: 3934 L: 3821 D: 17973
http://tests.stockfishchess.org/tests/view/5adcdcb60ebc595ec7ff8adb
See the commit history in PR#1559 for the proof that the committed
version is equivalent to the version in the tests above:
https://github.com/official-stockfish/Stockfish/pull/1559
Full credit to @protonspring for the renormalized values of the
ShelterStrength[] array used for the simplification. Thanks!
Bench: 4703935
This patch is non-functional. Current master does four operations to determine
whether an enemy pawn on this file is blocked by the king or not
```
f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 )
```
By adding a direction (based on the template color), this is reduced to two
operations. This works because b is limited to enemy pawns that are ahead of
the king and on the current file.
```
shift<Down>(b) & ksq
```
I've added a line of code, but the number of executing instructions is reduced
(I think). I'm not sure if this counts as a simplification, but it should
theoretically be a little faster (barely). The code line length is also reduced
making it a little easier to read.
Closes https://github.com/official-stockfish/Stockfish/pull/1552
No functional change.
