You gotta love Perft... just not too much!

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MartinBryant
Posts: 8
Joined: Wed Nov 20, 2013 11:37 pm
Location: Manchester, UK
Full name: Martin Bryant

You gotta love Perft... just not too much!

Post by MartinBryant » Sat Jul 27, 2019 8:23 am

Whilst re-writing Colossus to use bitboards I obviously used Perft to try to verify the correctness of the new move generators etc, mainly using the positions and results given here...
https://www.chessprogramming.org/Perft_Results

I have automated the testing now and I re-run them every so often just to get a warm, cosy glow :)
In fact, I was so warm and cosy that I would have bet a large sum of money that the move-generators were now bug free!

However, last night I stumbled across this remarkable mate in 89!
viewtopic.php?f=2&t=70695&p=798285&hili ... in#p798285

Just for fun I put it into Colossus... but was shocked to see it announce a mate in 8! :o
I stepped through it's PV to get to here...



...which Colossus thought was a mate in 1 (Qf1+)! OOPS!!

So, it turns out that there WAS still a bug in one of my 'generate-moves-out-of-check' routines but it only occurred when a BLACK PROMOTING pawn (it would have worked for white in a mirrored position or shifted one rank north) was blocking the rayed check... boy oh boy... glad I didn't make any bets! Humbling to accept that searching hundreds of billions of positions doesn't necessarily drive your code through all paths!

Perhaps someone with editing permissions would like to add this to the wiki page if they consider it worthy of note?

Uri Blass
Posts: 8602
Joined: Wed Mar 08, 2006 11:37 pm
Location: Tel-Aviv Israel

Re: You gotta love Perft... just not too much!

Post by Uri Blass » Sat Jul 27, 2019 8:51 am

I suggest that you add perft pgn command to verify your move generator.

The idea is that you take a big pgn and calculate the sum of perft(n) for all the positions in the pgn and find if the sum is correct(I am sure that part of the positions should have a promotion of a pawn in reply to check because it happens in chess games.

Movei support this command.
suppose that you have in the same folder the movei engine and also the pgn file that you want to calculate sum of perft(n) for all the positions in the pgn for some n that you choose n>=1
Suppose the name of the pgn is event.pgn

You only need to run movei in console mode and type
perftpgn event.pgn 2 and the program will give you sum of perft(2) for all positions in the pgn.

If you type
perfpgn event.pgn 3 then you will get the sum of perft(3)

Note that I stopped to work on movei many years ago and
I am not sure if movei has no bugs in calculating perft or in reading pgn.

elcabesa
Posts: 815
Joined: Sun May 23, 2010 11:32 am
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Re: You gotta love Perft... just not too much!

Post by elcabesa » Sat Jul 27, 2019 9:10 am

if you like you can find a lot of perft position and result in Vajolet test directory:

https://github.com/elcabesa/vajolet/blo ... ischer.txt
https://github.com/elcabesa/vajolet/blo ... /perft.txt

each line of the file contains a position and the perft value from depth 1 to depth 6 separed by ","

the positions are randomly sample from engine games

MartinBryant
Posts: 8
Joined: Wed Nov 20, 2013 11:37 pm
Location: Manchester, UK
Full name: Martin Bryant

Re: You gotta love Perft... just not too much!

Post by MartinBryant » Sat Jul 27, 2019 9:27 am

@Uri
Oh I see... so instead of searching billions of positions from a single root position you search thousands of root positions to a much shallower depth and sum them... great idea. Of course you need at least one other engine that can do this to compare the results against :) So thank you for the suggestion and for Movei!

Going off at a tangent, I have a text file containing many 'curious' positions that I've collected over the years... do you remember this one you posted years ago to highlight a bug in Glaurung?



Love these weird positions. I think it's amazing that the best engines today (well Stockfish at least) just immediately see this as a draw!


@elcabesa
Thank you so much for that resource! I'm feeling warmer and cosier already :)

mar
Posts: 2007
Joined: Fri Nov 26, 2010 1:00 pm
Location: Czech Republic
Full name: Martin Sedlak

Re: You gotta love Perft... just not too much!

Post by mar » Sat Jul 27, 2019 11:03 am

I believe in a small set of artificial positions that test all the gotchas with perft runs to very shallow depth.
It will run in a couple of milliseconds and the results will be way more valuable than running zillions of positions and waiting forever.
Especially useful when you need to re-test after bugfixes.
It has been discussed here in the past but you'd have to search the forum.
Jon has these in Arasan IIRC (among others).

Also don't forget that in FRC castling can be prevented due to backrank self-check.
Martin Sedlak

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Ajedrecista
Posts: 1401
Joined: Wed Jul 13, 2011 7:04 pm
Location: Madrid, Spain.
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Re: You gotta love Perft... just not too much!

Post by Ajedrecista » Sat Jul 27, 2019 12:52 pm

Hello Martin:

FWIW, here are JetChess perft counter results:

------------------------

First position:

[d]8/ppp3p1/8/8/3p4/5Q2/1ppp2K1/brk4n w - - 11 7

Code: Select all

8/ppp3p1/8/8/3p4/5Q2/1ppp2K1/brk4n w - - 11 7

  1  Qf3-e4           1
  2  Qf3-d5           1
  3  Qf3-c6           1
  4  Qf3*b7           1
  5  Qf3-g4           1
  6  Qf3-h5           1
  7  Qf3-e2           1
  8  Qf3-d1           1
  9  Qf3-f4           1
 10  Qf3-f5           1
 11  Qf3-f6           1
 12  Qf3-f7           1
 13  Qf3-f8           1
 14  Qf3-g3           1
 15  Qf3-h3           1
 16  Qf3-e3           1
 17  Qf3-d3           1
 18  Qf3-c3           1
 19  Qf3-b3           1
 20  Qf3-a3           1
 21  Qf3-f2           1
 22  Qf3-f1           1
 23  Kg2-h2           1
 24  Kg2-h3           1
 25  Kg2-f1           1
 26  Kg2-g1           1
 27  Kg2*h1           1

Total:               27


27 (move pathes after 1 half move).

Code: Select all

8/ppp3p1/8/8/3p4/5Q2/1ppp2K1/brk4n w - - 11 7

  1  Qf3-e4          16
  2  Qf3-d5          16
  3  Qf3-c6          15
  4  Qf3*b7          14
  5  Qf3-g4          15
  6  Qf3-h5          15
  7  Qf3-e2          15
  8  Qf3-d1           5
  9  Qf3-f4          12
 10  Qf3-f5          16
 11  Qf3-f6          17
 12  Qf3-f7          16
 13  Qf3-f8          16
 14  Qf3-g3          16
 15  Qf3-h3          16
 16  Qf3-e3          13
 17  Qf3-d3          15
 18  Qf3-c3          17
 19  Qf3-b3          16
 20  Qf3-a3          16
 21  Qf3-f2          16
 22  Qf3-f1           4
 23  Kg2-h2          15
 24  Kg2-h3          15
 25  Kg2-f1          15
 26  Kg2-g1          15
 27  Kg2*h1          13

Total:              390

390 (move pathes after 2 half moves).

Code: Select all

8/ppp3p1/8/8/3p4/5Q2/1ppp2K1/brk4n w - - 11 7

  1  Qf3-e4         410
  2  Qf3-d5         422
  3  Qf3-c6         361
  4  Qf3*b7         291
  5  Qf3-g4         337
  6  Qf3-h5         386
  7  Qf3-e2         354
  8  Qf3-d1          22
  9  Qf3-f4         314
 10  Qf3-f5         465
 11  Qf3-f6         428
 12  Qf3-f7         410
 13  Qf3-f8         407
 14  Qf3-g3         367
 15  Qf3-h3         368
 16  Qf3-e3         327
 17  Qf3-d3         368
 18  Qf3-c3         365
 19  Qf3-b3         400
 20  Qf3-a3         381
 21  Qf3-f2         318
 22  Qf3-f1          82
 23  Kg2-h2         411
 24  Kg2-h3         381
 25  Kg2-f1         320
 26  Kg2-g1         367
 27  Kg2*h1         292

Total:             9354

9,354 (move pathes after 3 half moves).

Code: Select all

8/ppp3p1/8/8/3p4/5Q2/1ppp2K1/brk4n w - - 11 7

  1  Qf3-e4        5899
  2  Qf3-d5        6608
  3  Qf3-c6        5432
  4  Qf3*b7        3953
  5  Qf3-g4        4844
  6  Qf3-h5        5551
  7  Qf3-e2        4713
  8  Qf3-d1         379
  9  Qf3-f4        4250
 10  Qf3-f5        6799
 11  Qf3-f6        6427
 12  Qf3-f7        6259
 13  Qf3-f8        6299
 14  Qf3-g3        5330
 15  Qf3-h3        5519
 16  Qf3-e3        4394
 17  Qf3-d3        5033
 18  Qf3-c3        5056
 19  Qf3-b3        5880
 20  Qf3-a3        5895
 21  Qf3-f2        4107
 22  Qf3-f1        1126
 23  Kg2-h2        5836
 24  Kg2-h3        5349
 25  Kg2-f1        4573
 26  Kg2-g1        5214
 27  Kg2*h1        3442

Total:           134167

134,167 (move pathes after 4 half moves).

Code: Select all

8/ppp3p1/8/8/3p4/5Q2/1ppp2K1/brk4n w - - 11 7

  1  Qf3-e4      138960
  2  Qf3-d5      155852
  3  Qf3-c6      121304
  4  Qf3*b7       83809
  5  Qf3-g4      107489
  6  Qf3-h5      119826
  7  Qf3-e2      103674
  8  Qf3-d1        1258
  9  Qf3-f4      102071
 10  Qf3-f5      158339
 11  Qf3-f6      145979
 12  Qf3-f7      143477
 13  Qf3-f8      136666
 14  Qf3-g3      113119
 15  Qf3-h3      118792
 16  Qf3-e3      102035
 17  Qf3-d3      110892
 18  Qf3-c3      105554
 19  Qf3-b3      126624
 20  Qf3-a3      120367
 21  Qf3-f2       86114
 22  Qf3-f1       20972
 23  Kg2-h2      126411
 24  Kg2-h3      111919
 25  Kg2-f1       85841
 26  Kg2-g1      106717
 27  Kg2*h1       68598

Total:          2922659

2,922,659 (move pathes after 5 half moves).

Code: Select all

8/ppp3p1/8/8/3p4/5Q2/1ppp2K1/brk4n w - - 11 7

  1  Qf3-e4     2043067
  2  Qf3-d5     2400718
  3  Qf3-c6     1875494
  4  Qf3*b7     1179900
  5  Qf3-g4     1577369
  6  Qf3-h5     1789106
  7  Qf3-e2     1498385
  8  Qf3-d1       23534
  9  Qf3-f4     1460575
 10  Qf3-f5     2379999
 11  Qf3-f6     2202790
 12  Qf3-f7     2189457
 13  Qf3-f8     2117195
 14  Qf3-g3     1616046
 15  Qf3-h3     1769424
 16  Qf3-e3     1446800
 17  Qf3-d3     1613799
 18  Qf3-c3     1540867
 19  Qf3-b3     1920057
 20  Qf3-a3     1851273
 21  Qf3-f2     1205034
 22  Qf3-f1      321529
 23  Kg2-h2     1841479
 24  Kg2-h3     1616605
 25  Kg2-f1     1189022
 26  Kg2-g1     1506314
 27  Kg2*h1      783792

Total:         42959630

42,959,630 (move pathes after 6 half moves).

Code: Select all

8/ppp3p1/8/8/3p4/5Q2/1ppp2K1/brk4n w - - 11 7

  1  Qf3-e4    44252259
  2  Qf3-d5    51796142
  3  Qf3-c6    39893873
  4  Qf3*b7    24406651
  5  Qf3-g4    33595491
  6  Qf3-h5    37403885
  7  Qf3-e2    31348692
  8  Qf3-d1       97895
  9  Qf3-f4    32503481
 10  Qf3-f5    51405304
 11  Qf3-f6    47637692
 12  Qf3-f7    47023255
 13  Qf3-f8    44057526
 14  Qf3-g3    33558958
 15  Qf3-h3    36392227
 16  Qf3-e3    31633575
 17  Qf3-d3    33779341
 18  Qf3-c3    31914699
 19  Qf3-b3    39645781
 20  Qf3-a3    36734943
 21  Qf3-f2    25046125
 22  Qf3-f1     6136738
 23  Kg2-h2    37846214
 24  Kg2-h3    32303239
 25  Kg2-f1    22440757
 26  Kg2-g1    30357266
 27  Kg2*h1    15585287

Total:        898797296

898,797,296 (move pathes after 7 half moves).

Code: Select all

8/ppp3p1/8/8/3p4/5Q2/1ppp2K1/brk4n w - - 11 7

  1  Qf3-e4   679398792
  2  Qf3-d5   818211933
  3  Qf3-c6   636311309
  4  Qf3*b7   362615718
  5  Qf3-g4   513893076
  6  Qf3-h5   581538175
  7  Qf3-e2   479915024
  8  Qf3-d1     1942029
  9  Qf3-f4   479826230
 10  Qf3-f5   801569459
 11  Qf3-f6   743662006
 12  Qf3-f7   738633069
 13  Qf3-f8   698864140
 14  Qf3-g3   501420741
 15  Qf3-h3   560378434
 16  Qf3-e3   466204810
 17  Qf3-d3   519668407
 18  Qf3-c3   491717592
 19  Qf3-b3   623626109
 20  Qf3-a3   581173372
 21  Qf3-f2   373707786
 22  Qf3-f1   104168822
 23  Kg2-h2   584042362
 24  Kg2-h3   495811901
 25  Kg2-f1   314299765
 26  Kg2-g1   439912431
 27  Kg2*h1   183502917

Total:      13776016409

13,776,016,409 (move pathes after 8 half moves).

Code: Select all

8/ppp3p1/8/8/3p4/5Q2/1ppp2K1/brk4n w - - 11 7

  1  Qf3-e4  14121497680
  2  Qf3-d5  16912831764
  3  Qf3-c6  13095468820
  4  Qf3*b7   7354886931
  5  Qf3-g4  10591111014
  6  Qf3-h5  11829340293
  7  Qf3-e2   9761516479
  8  Qf3-d1      7743493
  9  Qf3-f4  10210708624
 10  Qf3-f5  16591304499
 11  Qf3-f6  15471611915
 12  Qf3-f7  15239601790
 13  Qf3-f8  14238403577
 14  Qf3-g3  10229529752
 15  Qf3-h3  11353583884
 16  Qf3-e3   9794154338
 17  Qf3-d3  10568629839
 18  Qf3-c3   9979277108
 19  Qf3-b3  12579228547
 20  Qf3-a3  11510736023
 21  Qf3-f2   7665402220
 22  Qf3-f1   1997500610
 23  Kg2-h2  11660507736
 24  Kg2-h3   9693913965
 25  Kg2-f1   5989115732
 26  Kg2-g1   8820377379
 27  Kg2*h1   3666868008

Total:      280934852020

280,934,852,020 (move pathes after 9 half moves).

Code: Select all

8/ppp3p1/8/8/3p4/5Q2/1ppp2K1/brk4n w - - 11 7

  1  Qf3-e4  229051918319
  2  Qf3-d5  279913009105
  3  Qf3-c6  219025117242
  4  Qf3*b7  117591776369
  5  Qf3-g4  171218402338
  6  Qf3-h5  193577642122
  7  Qf3-e2  158744542570
  8  Qf3-d1     164182745
  9  Qf3-f4  157427397766
 10  Qf3-f5  271783797498
 11  Qf3-f6  253632232167
 12  Qf3-f7  250905997217
 13  Qf3-f8  235729250880
 14  Qf3-g3  162724064213
 15  Qf3-h3  184037916652
 16  Qf3-e3  151196637763
 17  Qf3-d3  172788014801
 18  Qf3-c3  163426496951
 19  Qf3-b3  208299912413
 20  Qf3-a3  191480280026
 21  Qf3-f2  122607502461
 22  Qf3-f1   37023130162
 23  Kg2-h2  192714491938
 24  Kg2-h3  160300032793
 25  Kg2-f1   86594354892
 26  Kg2-g1  132955498297
 27  Kg2*h1   46248557504

Total:      4551162157204

4,551,162,157,204 (move pathes after 10 half moves).

Code: Select all

8/ppp3p1/8/8/3p4/5Q2/1ppp2K1/brk4n w - - 11 7

  1  Qf3-e4  4639240576627
  2  Qf3-d5  5643850258030
  3  Qf3-c6  4408578155286
  4  Qf3*b7  2352954475738
  5  Qf3-g4  3451130305535
  6  Qf3-h5  3870284702050
  7  Qf3-e2  3167251824222
  8  Qf3-d1      703637654
  9  Qf3-f4  3255840729546
 10  Qf3-f5  5486343980658
 11  Qf3-f6  5148457931823
 12  Qf3-f7  5054982106848
 13  Qf3-f8  4724108757950
 14  Qf3-g3  3268935659958
 15  Qf3-h3  3678391789721
 16  Qf3-e3  3103067435753
 17  Qf3-d3  3455087808740
 18  Qf3-c3  3273555340342
 19  Qf3-b3  4145011419201
 20  Qf3-a3  3778864861725
 21  Qf3-f2  2470715600826
 22  Qf3-f1   709187300245
 23  Kg2-h2  3782089600933
 24  Kg2-h3  3098518454062
 25  Kg2-f1  1666255902064
 26  Kg2-g1  2654869996046
 27  Kg2*h1   927271888594

Total:      91215550500177

91,215,550,500,177 (move pathes after 11 half moves).

Code: Select all

8/ppp3p1/8/8/3p4/5Q2/1ppp2K1/brk4n w - - 11 7

perft( 1) =                 27
perft( 2) =                390
perft( 3) =              9,354
perft( 4) =            134,167
perft( 5) =          2,922,659
perft( 6) =         42,959,630
perft( 7) =        898,797,296
perft( 8) =     13,776,016,409
perft( 9) =    280,934,852,020
perft(10) =  4,551,162,157,204
perft(11) = 91,215,550,500,177
------------------------

Second position:

[d]8/6kR/8/8/8/bq6/1rqqqqqq/K1nqnbrq b - - 0 1

Code: Select all

8/6kR/8/8/8/bq6/1rqqqqqq/K1nqnbrq b - - 0 1

  1  qc2*h7          1
  2  qh2*h7          1
  3  kg7*h7          1
  4  kg7-f6          1
  5  kg7-g6          1
  6  kg7-f8          1
  7  kg7-g8          1

Total:               7


7 (move pathes after 1 half move).

Code: Select all

8/6kR/8/8/8/bq6/1rqqqqqq/K1nqnbrq b - - 0 1

  1  qc2*h7           0
  2  qh2*h7           0
  3  kg7*h7           0
  4  kg7-f6          13
  5  kg7-g6          13
  6  kg7-f8          13
  7  kg7-g8          13

Total:               52

52 (move pathes after 2 half moves).

Code: Select all

8/6kR/8/8/8/bq6/1rqqqqqq/K1nqnbrq b - - 0 1

  1  qc2*h7           0
  2  qh2*h7           0
  3  kg7*h7           0
  4  kg7-f6        1173
  5  kg7-g6        1134
  6  kg7-f8        1150
  7  kg7-g8        1136

Total:             4593

4,593 (move pathes after 3 half moves).

Code: Select all

8/6kR/8/8/8/bq6/1rqqqqqq/K1nqnbrq b - - 0 1

  1  qc2*h7           0
  2  qh2*h7           0
  3  kg7*h7           0
  4  kg7-f6       12875
  5  kg7-g6       12407
  6  kg7-f8       12568
  7  kg7-g8       12418

Total:            50268

50,268 (move pathes after 4 half moves).

Code: Select all

8/6kR/8/8/8/bq6/1rqqqqqq/K1nqnbrq b - - 0 1

  1  qc2*h7           0
  2  qh2*h7           0
  3  kg7*h7           0
  4  kg7-f6     1203890
  5  kg7-g6     1130012
  6  kg7-f8     1161600
  7  kg7-g8     1138882

Total:          4634384

4,634,384 (move pathes after 5 half moves).

Code: Select all

8/6kR/8/8/8/bq6/1rqqqqqq/K1nqnbrq b - - 0 1

  1  qc2*h7           0
  2  qh2*h7           0
  3  kg7*h7           0
  4  kg7-f6    12918613
  5  kg7-g6    12129128
  6  kg7-f8    12434860
  7  kg7-g8    12202759

Total:         49685360

49,685,360 (move pathes after 6 half moves).

Code: Select all

8/6kR/8/8/8/bq6/1rqqqqqq/K1nqnbrq b - - 0 1

  1  qc2*h7           0
  2  qh2*h7           0
  3  kg7*h7           0
  4  kg7-f6  1257041566
  5  kg7-g6  1160039868
  6  kg7-f8  1204915549
  7  kg7-g8  1181183228

Total:       4803180211

4,803,180,211 (move pathes after 7 half moves).

Code: Select all

8/6kR/8/8/8/bq6/1rqqqqqq/K1nqnbrq b - - 0 1

  1  qc2*h7            0
  2  qh2*h7            0
  3  kg7*h7            0
  4  kg7-f6  13231048562
  5  kg7-g6  12207734928
  6  kg7-f8  12669010038
  7  kg7-g8  12429964013

Total:       50537757541

50,537,757,541 (move pathes after 8 half moves).

Code: Select all

8/6kR/8/8/8/bq6/1rqqqqqq/K1nqnbrq b - - 0 1

  1  qc2*h7              0
  2  qh2*h7              0
  3  kg7*h7              0
  4  kg7-f6  1330980120571
  5  kg7-g6  1212934307577
  6  kg7-f8  1276610769146
  7  kg7-g8  1255748211784

Total:       5076273409078

5,076,273,409,078 (move pathes after 9 half moves).

Code: Select all

8/6kR/8/8/8/bq6/1rqqqqqq/K1nqnbrq b - - 0 1

perft(1) =                 7
perft(2) =                52
perft(3) =             4,593
perft(4) =            50,268
perft(5) =         4,634,384
perft(6) =        49,685,360
perft(7) =     4,803,180,211
perft(8) =    50,537,757,541
perft(9) = 5,076,273,409,078
------------------------

Regards from Spain.

Ajedrecista.

Uri Blass
Posts: 8602
Joined: Wed Mar 08, 2006 11:37 pm
Location: Tel-Aviv Israel

Re: You gotta love Perft... just not too much!

Post by Uri Blass » Sat Jul 27, 2019 1:15 pm

mar wrote:
Sat Jul 27, 2019 11:03 am
I believe in a small set of artificial positions that test all the gotchas with perft runs to very shallow depth.
It will run in a couple of milliseconds and the results will be way more valuable than running zillions of positions and waiting forever.
Especially useful when you need to re-test after bugfixes.
It has been discussed here in the past but you'd have to search the forum.
Jon has these in Arasan IIRC (among others).

Also don't forget that in FRC castling can be prevented due to backrank self-check.

calculate the sum of some million of perft(2) from a big pgn is not waiting forever and I believe it has good chances to cover all the cases.

I doubt if a small set cover all the cases that you can think about.

I remember that I had a mistake when I believed double check cannot be done from 2 rook directions(it can be done if a pawn capture and promote gxh8+ when both h8 and rook g6 threat check).

mar
Posts: 2007
Joined: Fri Nov 26, 2010 1:00 pm
Location: Czech Republic
Full name: Martin Sedlak

Re: You gotta love Perft... just not too much!

Post by mar » Sat Jul 27, 2019 3:06 pm

Uri Blass wrote:
Sat Jul 27, 2019 1:15 pm
calculate the sum of some million of perft(2) from a big pgn is not waiting forever and I believe it has good chances to cover all the cases.

I doubt if a small set cover all the cases that you can think about.
I disagree.
you can always add a new corner case if you miss something, I never claimed it'll cover 100% cases

as for what you propose: first you need to parse the pgn, extract million positions and then run million perft(2),
this will be orders of magnitude slower (even if you preprocess and parallelize) than doing say 20-30 artificial positions for both sides.
you'll also need to get the correct perft values first so you need to preprocess this million of positions with an engine you trust,
so even more work to do

99.9% of those million(s) of positions won't stress test your movegen so it's a waste of effort and processing time plus I bet you will cover less corner cases with that
by increasing the sample size you also increase processing time, I hope you realize now how inefficient that would be
Martin Sedlak

Uri Blass
Posts: 8602
Joined: Wed Mar 08, 2006 11:37 pm
Location: Tel-Aviv Israel

Re: You gotta love Perft... just not too much!

Post by Uri Blass » Sat Jul 27, 2019 6:55 pm

mar wrote:
Sat Jul 27, 2019 3:06 pm
Uri Blass wrote:
Sat Jul 27, 2019 1:15 pm
calculate the sum of some million of perft(2) from a big pgn is not waiting forever and I believe it has good chances to cover all the cases.

I doubt if a small set cover all the cases that you can think about.
I disagree.
you can always add a new corner case if you miss something, I never claimed it'll cover 100% cases

as for what you propose: first you need to parse the pgn, extract million positions and then run million perft(2),
this will be orders of magnitude slower (even if you preprocess and parallelize) than doing say 20-30 artificial positions for both sides.
you'll also need to get the correct perft values first so you need to preprocess this million of positions with an engine you trust,
so even more work to do

99.9% of those million(s) of positions won't stress test your movegen so it's a waste of effort and processing time plus I bet you will cover less corner cases with that
by increasing the sample size you also increase processing time, I hope you realize now how inefficient that would be
My point is that you probably cannot think in advance about all corner cases and the time of calculating sum of million perft(2) is relatively small to the time you work on your move generator(even if it takes one hour then you spend many hours on your move generator.

Initially you can use small number of positions but you can also use sum of perft(2) with many positions as another test.

AndrewGrant
Posts: 493
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Location: U.S.A
Full name: Andrew Grant
Contact:

Re: You gotta love Perft... just not too much!

Post by AndrewGrant » Mon Jul 29, 2019 2:08 am

elcabesa wrote:
Sat Jul 27, 2019 9:10 am
if you like you can find a lot of perft position and result in Vajolet test directory:

https://github.com/elcabesa/vajolet/blo ... ischer.txt
https://github.com/elcabesa/vajolet/blo ... /perft.txt

each line of the file contains a position and the perft value from depth 1 to depth 6 separed by ","

the positions are randomly sample from engine games
I opened the Fischer one, and recognized it :)

The next one though. Thats a lengthy PERFT suite.

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