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--- chess:programming:perft [2021/10/12 10:00] – peter
+++ chess:programming:perft [2021/10/12 10:27] (current) – peter
@@ Line 1: / Line 1: @@
 ====== Chess - Programming - Perft ======
-**Perft** does a raw node count, up to some specified depth, by doing a full tree search.
+**Perft**, standing for Performance Test, does a raw node count, up to some specified depth, by doing a full tree search.
+  * By recording the amount of time taken to complete a Perft Test, it is possible to check the performance.
 Draws by threefold repetition are ignored.
+----
+===== Perft Function =====
+A simple perft function might look as follows:
+<code cpp>
+typedef unsigned long long u64;
+u64 Perft(int depth)
+{
+  MOVE move_list[256];
+  int n_moves, i;
+  u64 nodes = 0;
+  if (depth == 0) return 1;
+  n_moves = GenerateMoves(move_list);
+  for (i = 0; i < n_moves; i++) {
+      MakeMove(move_list[i]);
+      nodes += Perft(depth - 1);
+      UndoMove(move_list[i]);
+  }
+  return nodes;
+}
+</code>
 ----
@@ Line 30: / Line 60: @@
 |11|2097651003696806| | | | |39147687661803|1078854669486| |
 |12|62,854,969,236,701,747| | | | |1224448528652016|8361091858959| |
+|13|1,981,066,775,000,396,239| | | | | | | |
 ----
@@ Line 138: / Line 169: @@
 |5|3605103|3797944|
 |6|71179139|74977083|
+----
+==== Position 1 ====
+This position is very good because it catches many possible bugs:
+<code>
+Position r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq -
+</code>
+^Depth^Perft Value^
+|1|48|
+|2|2039|
+|3|97862|
+|4|4085603|
+|5|193690690|
+|6|8031647685|
+</code>
 ----
@@ Line 175: / Line 225: @@
 |5|15833292|2046173|6512|0|329464|200568| |
 |6|706045033|210369132|212|10882006|81102984|26973664| |
 ----
-A very interesting FEN:
+===== A very interesting FEN =====
 queens with only 6 captures:
@@ Line 186: / Line 236: @@
 k1qrq3/rq4Qq/3q1Q2/Q6q/3Q4/1Q4Q1/R1q1Q2Q/KQR2q1q/
 </code>
+----
+===== Other FENs useful for finding bugs =====
+<code>
+Position 8/3K4/2p5/p2b2r1/5k2/8/8/1q6 b - 1 67
+Perft(1) = 50
+Perft(2) = 279
+Position 8/7p/p5pb/4k3/P1pPn3/8/P5PP/1rB2RK1 b - d3 0 28
+Perft(6) = 38633283
+Position rnbqkb1r/ppppp1pp/7n/4Pp2/8/8/PPPP1PPP/RNBQKBNR w KQkq f6 0 3
+Perft(5) = 11139762
+Position 8/2p5/3p4/KP5r/1R3p1k/8/4P1P1/8 w - -
+Perft(6) = 11030083
+Perft(7) = 178633661
+</code>
 ----