Well, I guess I've solved the hideous en passant bug. After some quick tests it seems to work now fine. Right now I'm testing it playing many games in fast controls, but in any case the improve is good enough to update the code in the github repository. So please replace the old code ASAP with the new one:
https://github.com/pocopito/secondchess


Best regards and thanks everybody who is testing the code.

E Diaz

Emilio
My compile problems persist as now trying to compile the latest 1.24v secondchess. c with tcc I get xboard type error eg:

Code:

SecondChess>tcc secondchess.c
secondchess.c:2000: incompatible types for redefinition of 'xboard'

Any idea why & how to fix?
Best wishes

Hi Richard

Thanks for testing and for the feedback.
I'm not quite sure how the xboard part works, but check this: Right under the "main" section:
/*
****************************************************************************
* Main program *
****************************************************************************
*/

//void xboard();


Check either the "void xboard()" part is either commented or not, and just change to the opposite :) (I've seen that with different compilers I need one or the other option.)

Regards

Emilio

Emilio
Thanks for your quick reply-your fix worked (I uncommented xboard).
Then I compiled fine (tcc) & played my second game & I lost on time!!!
(I'm having a bad day.....) Game pgn below:

[Event "Computer chess game"]
[Site "RICHARD-PC"]
[Date "2012.04.25"]
[Round "?"]
[White "Richard"]
[Black "SecondChess"]
[Result "0-1"]
[BlackElo "2000"]
[ECO "A18"]
[Opening "English"]
[Time "17:22:55"]
[Variation "Mikenas, Flohr, 4...d4"]
[WhiteElo "2400"]
[TimeControl "300"]
[Termination "time forfeit"]
[PlyCount "114"]
[WhiteType "human"]
[BlackType "program"]

1. e4 d5 2. Nc3 d4 3. Nce2 e6 4. Nf3 Nc6 5. e5 a6 6. Ng3 Qd5 7. d3 Nxe5 8.
Nxe5 Qxe5+ 9. Qe2 Bb4+ 10. Bd2 Bxd2+ 11. Kxd2 Qf4+ 12. Ke1 Nf6 13. Qd2
Qxd2+ 14. Kxd2 O-O 15. Be2 Bd7 16. Bf3 Rad8 17. Bxb7 a5 18. Ba6 Bc6 19. f3
Ra8 20. Bc4 Rab8 21. b3 Bd5 22. Bxd5 exd5 23. Rae1 a4 24. Re7 Rbc8 25. Nf5
axb3 26. axb3 c5 27. Ra1 Ra8 28. Rxa8 Rxa8 29. Rc7 g6 30. Ne7+ Kf8 31. Nc6
Kg8 32. Ra7 Rxa7 33. Nxa7 c4 34. b4 Kh8 35. b5 Kg8 36. b6 Nd7 37. b7 Nb8
38. Nc8 Kf8 39. dxc4 dxc4 40. Nd6 c3+ 41. Kd3 Nc6 42. Nb5 Ne5+ 43. Kxd4
Nc6+ 44. Kxc3 Kg8 45. Kc4 Na5+ 46. Kc5 Nxb7+ 47. Kb6 Nd8 48. c4 Ne6 49. c5
Nf4 50. c6 Nd5+ 51. Kb7 f6 52. c7 Nxc7 53. Kxc7 Kf8 54. Nd4 Kg8 55. Kd7 Kf7
56. g4 h5 57. h3 Kg7 58. ... {White forfeits on time} 0-1

I was surprised SecondChess played quicker-I was expecting it to time out like my first game! So it's one all (game score) and now I'll have to play a deciding game....
Thanks

richardpd wrote:Emilio
Thanks for your quick reply-your fix worked (I uncommented xboard).
Then I compiled fine (tcc) & played my second game & I lost on time!!!
(I'm having a bad day.....) Game pgn below:

[Event "Computer chess game"]
[Site "RICHARD-PC"]
[Date "2012.04.25"]
[Round "?"]
[White "Richard"]
[Black "SecondChess"]
[Result "0-1"]
[BlackElo "2000"]
[ECO "A18"]
[Opening "English"]
[Time "17"]
[Variation "Mikenas, Flohr, 4...d4"]
[WhiteElo "2400"]
[TimeControl "300"]
[Termination "time forfeit"]
[PlyCount "114"]
[WhiteType "human"]
[BlackType "program"]

1. e4 d5 2. Nc3 d4 3. Nce2 e6 4. Nf3 Nc6 5. e5 a6 6. Ng3 Qd5 7. d3 Nxe5 8.
Nxe5 Qxe5+ 9. Qe2 Bb4+ 10. Bd2 Bxd2+ 11. Kxd2 Qf4+ 12. Ke1 Nf6 13. Qd2
Qxd2+ 14. Kxd2 O-O 15. Be2 Bd7 16. Bf3 Rad8 17. Bxb7 a5 18. Ba6 Bc6 19. f3
Ra8 20. Bc4 Rab8 21. b3 Bd5 22. Bxd5 exd5 23. Rae1 a4 24. Re7 Rbc8 25. Nf5
axb3 26. axb3 c5 27. Ra1 Ra8 28. Rxa8 Rxa8 29. Rc7 g6 30. Ne7+ Kf8 31. Nc6
Kg8 32. Ra7 Rxa7 33. Nxa7 c4 34. b4 Kh8 35. b5 Kg8 36. b6 Nd7 37. b7 Nb8
38. Nc8 Kf8 39. dxc4 dxc4 40. Nd6 c3+ 41. Kd3 Nc6 42. Nb5 Ne5+ 43. Kxd4
Nc6+ 44. Kxc3 Kg8 45. Kc4 Na5+ 46. Kc5 Nxb7+ 47. Kb6 Nd8 48. c4 Ne6 49. c5
Nf4 50. c6 Nd5+ 51. Kb7 f6 52. c7 Nxc7 53. Kxc7 Kf8 54. Nd4 Kg8 55. Kd7 Kf7
56. g4 h5 57. h3 Kg7 58. ... {White forfeits on time} 0-1

I was surprised SecondChess played quicker-I was expecting it to time out like my first game! So it's one all (game score) and now I'll have to play a deciding game....
Thanks

Could you please send me link to the latest build?

richardpd wrote:Emilio
Thanks for your quick reply-your fix worked (I uncommented xboard).
Then I compiled fine (tcc) & played my second game & I lost on time!!!
(I'm having a bad day.....) Game pgn below:
...

I was surprised SecondChess played quicker-I was expecting it to time out like my first game! So it's one all (game score) and now I'll have to play a deciding game....
Thanks

I'm glad the trick worked!

If the engine is playing faster, it can be due to several reasons:
-You modified the max_depth parameter to a lower value (which'd make the engine play faster but, of course, worse)
-Maybe you applied an optimization option in the compilation, but it seems tcc has nothing like this
-If in the search function you switch from

Code:

else
{
//value = Quiescent(alpha, beta);
value = -Eval();
}

to

Code:

else
{
value = Quiescent(alpha, beta);
//value = -Eval();
}

The engine will play slower.

In any case I'm glad you're enjoying it. If while reading the code you find some parts hard to understand, please let me know, as the main goal of secondchess is being a useful tool for anyone interested on how a chess engine works.

Regards

Emilio

PS: secondchess has no opening book or random on its code, so if you want to get some variations in the game, the "novelties" must be made by you
PS': take into account that despite you're playing games with time control seondchess has no idea of this issue. I mean, it won't play faster when you set a shorter time control.

Hi Emilio
Since my last post I have played quite a few games versus SecondChess-some I win & some I lose.
Like the game I posted earlier all the games I have played as White with 1.e4 & SecondChess always replies 1.d5 (Scandinavian opening).
I do not mind this as it gives me practice in this opening!!(one day I will let SecondChess play white!!).

Meanwhile I have been trying to learn C programming from internet resources and playing around trying to make my own C console chess engine.
This will take a while as my C programming expertise/skill is basic!
I do hope to look at SecondChess C sourcecode and understand it more now I know more of C language!
If I look at it & get queries I will ask for your help & many thanks for trying to make this engine understandable to a fledgling/beginner chess programmer-this is very helpful!

I am posting this from my login on my wife's desktop computer Win7, where I have just compiled SecondChess so I can play it on this computer(my computer is updating Ubuntu as I type-although it dual boots with Win7 -via KVM switch...).I did this in Geany editor for windows (this uses gcc compiler that is from DevC++ which is in the Win7 path).
It compiled with some error messages which I post below but it runs fine in Arena.

I thought you might be interested in the compile errors/warnings:

gcc -Wall -c "secondchess.c" (in directory: C:\pocopito-secondchess-v0.1-30-gc8db4a0\pocopito-secondchess-c8db4a0)
secondchess.c: In function `Gen':
secondchess.c:530: warning: implicit declaration of function `IsInCheck'
secondchess.c:531: warning: implicit declaration of function `IsAttacked'
secondchess.c: In function `GenCaps':
secondchess.c:603: warning: unused variable `row'
secondchess.c: In function `TakeBack':
secondchess.c:1432: warning: unused variable `i'
secondchess.c: In function `perft':
secondchess.c:1767: warning: unused variable `value'
secondchess.c:1772: warning: unused variable `tmpMove'
Compilation finished successfully.

Doesn't seem to be any major issue here but you may want to consider fixing the code for the GCC compiler?
I have not tried it with VisStudioExpress cl.exe as I did initially on my machine! (As per my orginal post here. Also I have now more experience with various C compilers on Win7 eg cl.exe, tcc, gcc, lcc etc & various IDE eg MSVisStudioExpress/DevC++/Geany!).

Best wishes

Hi Richard

I'm glad to read the good news, specially the one related to the use of geany+gcc in order to compile secondchess without problems under windows. Probably I'll add this info to the README file, and I guess I myself will use it in order to provide windows executables. Thanks for the info!

One little tip: if you want to play something different to the scandinavian, you can undo the d5 move played by black, make the move you desire. After that the engine will play white automatically, but all you have to do is just undo its move and play as white again.

I myself am not a good C programmer, and actually one of the reasons I started this little project was to refresh and improve my C skills.

Thanks for the compiler warnings. I guess most of them are due to the fact that currently secondchess is in an unstable stage, and some of the tests I do leave bad code such as unused vars.
By the way, as you're working under linux, give a try to the clang compiler. It works quite like gcc, but very often the kind of info it provides is more human friendly:
http://clang.llvm.org/diagnostics.html

I'm not sure if I provided this info on a previous post, but just in case:

This is a nice forum about chess programming:
http://talkchess.com/forum/index.php

And this is a nice wikispace about the same topic:
http://chessprogramming.wikispaces.com/

Cheers

E Diaz

Emilio
Many thanks for your prompt & helpful reply and all your help with SecondChess.
I'm sure our Chess & C programming will progress well!
Best wishes

Emilio
I have been running SecondChess in Arena GUI but I've just tried it in console mode-but the board display there is not so good. Have you noticed that?
With a minor adjustment to PrintBoard function this is fixed eg:
Presently I have this console output:-

Code:

Second Chess, by Emilio Diaz
 Help
 d: display board
 MOVE: make a move (e.g. b1c3, a7a8q, e1g1)
 on: force computer to move
 quit: exit
 sd n: set engine depth to n plies
 undo: take back last move
sc> e2e4
 +---+---+---+---+---+---+---+---+
 8 | r | n | b | q | k | b | n | r |
 +---+---+---+---+---+---+---+---+
 7 | p | p | p | p | p | p | p | p |
 +---+---+---+---+---+---+---+---+
 6 |  |  |  |  |  |  |  |  |
 +---+---+---+---+---+---+---+---+
 5 |  |  |  |  |  |  |  |  |
 +---+---+---+---+---+---+---+---+
 4 |  |  |  |  | P |  |  |  |
 +---+---+---+---+---+---+---+---+
 3 |  |  |  |  | * |  |  |  |
 +---+---+---+---+---+---+---+---+
 2 | P | P | P | P |  | P | P | P |
 +---+---+---+---+---+---+---+---+
 1 | R | N | B | Q | K | B | N | R |
 +---+---+---+---+---+---+---+---+
    a  b  c  d  e  f  g  h
Search result: move = d7d5; nodes = 0, evaluations = 4074706, moves made = 45130
41, depth = 6, score = 0.85, time = 3.26s, knps = 0.00
 +---+---+---+---+---+---+---+---+
 8 | r | n | b | q | k | b | n | r |
 +---+---+---+---+---+---+---+---+
 7 | p | p | p |  | p | p | p | p |
 +---+---+---+---+---+---+---+---+
 6 |  |  |  | * |  |  |  |  |
 +---+---+---+---+---+---+---+---+
 5 |  |  |  | p |  |  |  |  |
 +---+---+---+---+---+---+---+---+
 4 |  |  |  |  | P |  |  |  |
 +---+---+---+---+---+---+---+---+
 3 |  |  |  |  |  |  |  |  |
 +---+---+---+---+---+---+---+---+
 2 | P | P | P | P |  | P | P | P |
 +---+---+---+---+---+---+---+---+
 1 | R | N | B | Q | K | B | N | R |
 +---+---+---+---+---+---+---+---+
    a  b  c  d  e  f  g  h
CASTLE: 15
sc>





SO...on changing PrintBoard function to:-

Code:


void PrintBoard()
{
   char pieceName[] = "PNBRQKpnbrqk";
   int i;
   for (i = 0; i < 64; i++)
   {
      if ((i & 7) == 0)
      {
         printf("    +---+---+---+---+---+---+---+---+\n");
         if (i <= 56)
         {
            printf(" %2d |", 8 - (((unsigned) i) >> 3));
         }
      }
      if (piece[i] == EMPTY)
         printf("  |");
      else if (piece[i] == EPS_SQUARE)
         printf(" * |");
      else
      {
         printf(" %c |", pieceName[piece[i] + (color[i] == WHITE ? 0 : 6)]);
      }
      if ((i & 7) == 7)
         printf("\n");
   }
   printf("    +---+---+---+---+---+---+---+---+\n      a  b  c  d  e  f  g  h\n");
}




this outputs a better board at the console eg:

Code:


Second Chess, by Emilio Diaz
 Help
 d: display board
 MOVE: make a move (e.g. b1c3, a7a8q, e1g1)
 on: force computer to move
 quit: exit
 sd n: set engine depth to n plies
 undo: take back last move
sc> e2e4
    +---+---+---+---+---+---+---+---+
  8 | r | n | b | q | k | b | n | r |
    +---+---+---+---+---+---+---+---+
  7 | p | p | p | p | p | p | p | p |
    +---+---+---+---+---+---+---+---+
  6 |  |  |  |  |  |  |  |  |
    +---+---+---+---+---+---+---+---+
  5 |  |  |  |  |  |  |  |  |
    +---+---+---+---+---+---+---+---+
  4 |  |  |  |  | P |  |  |  |
    +---+---+---+---+---+---+---+---+
  3 |  |  |  |  | * |  |  |  |
    +---+---+---+---+---+---+---+---+
  2 | P | P | P | P |  | P | P | P |
    +---+---+---+---+---+---+---+---+
  1 | R | N | B | Q | K | B | N | R |
    +---+---+---+---+---+---+---+---+
      a  b  c  d  e  f  g  h
Search result: move = d7d5; nodes = 0, evaluations = 4074706, moves made = 45130
41, depth = 6, score = 0.85, time = 3.23s, knps = 0.00
    +---+---+---+---+---+---+---+---+
  8 | r | n | b | q | k | b | n | r |
    +---+---+---+---+---+---+---+---+
  7 | p | p | p |  | p | p | p | p |
    +---+---+---+---+---+---+---+---+
  6 |  |  |  | * |  |  |  |  |
    +---+---+---+---+---+---+---+---+
  5 |  |  |  | p |  |  |  |  |
    +---+---+---+---+---+---+---+---+
  4 |  |  |  |  | P |  |  |  |
    +---+---+---+---+---+---+---+---+
  3 |  |  |  |  |  |  |  |  |
    +---+---+---+---+---+---+---+---+
  2 | P | P | P | P |  | P | P | P |
    +---+---+---+---+---+---+---+---+
  1 | R | N | B | Q | K | B | N | R |
    +---+---+---+---+---+---+---+---+
      a  b  c  d  e  f  g  h
CASTLE: 15
sc>

I hope you can see the difference and do not mind me asking and showing this!?
Thanks

Of course there was something wrong about printBoard. I guess I just had got used to it and saw just right :) (the funny think is that I almost always use the terminal to play against secondchess).

Thanks for pointing it out, it's already fixed in the github repository.

Best Regards

E Diaz

Emilio
Great that you are aware of the board print console output.

I am now trying to more fully understand the PrintBoard function.
My C skills are very basic at the moment as I do not fully understand bitwise operators yet!
From Wikipedia:wikipedia bitwise
A bitwise AND takes two binary representations of equal length and performs the logical AND operation on each pair of corresponding bits.

So I need to understand these lines better

Code:

if ((i & 7) == 0)

if (i <= 56)
         {
            printf(" %d |", 8 - (((unsigned) i) >> 3));
         }

if ((i & 7) == 7)

and I need to understand this line better:

Code:

printf(" %c |", pieceName[piece[i] + (color[i] == WHITE ? 0 : 6)]);

(this line not bitwise op but the >> ? 0 : 6 << part).

SecondChess is using 1D arrays for it's board and piece reps and I need to more fully familiarise myself with this approach over the 2D approach I am more used to for matrix/board reps! Hopefully it won't take me too long to fully grasp this bitwise op & ID board rep coding ideas!

Best wishes

The printboard function is a nice work by Mr Nguyen (The creator of firstchess, from wich secondchess started on).

And about bitwise operations, two of the most important ones are in the very first lines of code:

#define COL(pos) ((pos)&7)
#define ROW(pos) (((unsigned)pos)>>3)


Thanks god (and I mean the only true one) chess is played in an 8 by 8 board.

Emilio
Many thanks again for your very helpful reply
(reminding me of the board defines is very helpful in understanding PrintBoard function!!).

Two minor modifcations:
-The diagrams are printed in a more easy to watch format
-As secondchess has no opening book, it always plays the same moves in the same position. It's a problem for me, because when I try to test it playing many games against another engine, many of the games are all the same. In order to provide more variety, and threfore allow a better detection of bugs in the move generator, I've added some randomnes to the evaluation. It's implemented in a very gross way, but so far it makes its work.