Best Perft() position

[pinkfloydhomer]

If you could only choose _one_ position for Perft()-ing, which one would it be?

I guess it would involve all sorts of moves from all sorts of pieces, including promotions, castling, en passant, pins, double checks, castlings that are illegal because the king is attacked, because the interim square is attacked or because the destination square is attacked, en passant captures that are illegal because the captured pawn blocks a check etc.

Gentlemen, gimme your best FENs

[Kempelen]

Try these:

r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - 0 1
depth nodes totalnodes
1 48 48
2 2039 2087
3 97862 99949
4 4085603 4185552
5 193690690 197876242
6 8031647685 8229523927

n1n5/PPPk4/8/8/8/8/4Kppp/5N1N b - - 0 1
depth nodes totalnodes
1 24 24
2 496 520
3 9483 10003
4 182838 192841
5 3605103 3797944
6 71179139 74977083

[wgarvin]

Try these:

r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - 0 1
depth nodes totalnodes
1 48 48
2 2039 2087
3 97862 99949
4 4085603 4185552
5 193690690 197876242
6 8031647685 8229523927

That first one you posted, is listed on the wiki on the Perft results page.

It lists the number of e.p. moves, castles, promotions, checks and checkmates at each ply (according to that page, this position has some of everything by depth 4)

[pinkfloydhomer]

I propose something like this, as a first attempt:

r3k2r/pppp1ppp/1b3bnN/nP6/BBP1P3/q4NP1/P2P2PP/R2Q1RK1 w kq - 0 1

Although it doesn't test everything for both sides. Castling stuff is tested for black. Tricky illegal en passants are checked for white. I guess by starting out with white uncastled, this position would appear in the tree near the root and castling would also be tested for white. Back to the drawing board

[pinkfloydhomer]

Forgot promotions in the last one.

I think this position covers most if not all of the tricky situations, although not the same situations for both sides. So the reversed position should probably be used as well:

r3k2r/Pppp1ppp/1b3nbN/nP6/BBP1P3/q4N2/Pp1P2PP/R2Q1RK1 w kq - 0 1
r2q1rk1/pP1p2pp/Q4n2/bbp1p3/Np6/1B3NBn/pPPP1PPP/R3K2R b KQ - 0 1

1: 6
2: 264
3: 9467
4: 422333
5: 15833292
6: 706045033