TD(lambda), and a big rework

NOTE: 6x6 weights are as-yet untrained

On the performance side:
* switch from linked-list chaining hash table to direct mapping
* cache check_win by hash
* persist transposition tables across plies (this was a big deal and difficult to puzzle out)
* add align directives to the network floats
* prepare_nn_input gained a small LUT to avoid branching (i suppose you might call this 1D embedding)
* apply mtune=native for the native builds

On the correctness side:
* Zobrist has now includes the ply parity
* the network now predicts something in [-1, 1] using tanh (approximated by polynomials)
* the training object is now MSE because we're learning a value estimate
* use .clangd instead of compile_commands.json

On the training side:
* completely forgo human-derived data set
* implement td(lambda), self-play, tournaments

1 files changed, 62 insertions, 0 deletions

diff --git a/include/tt.h b/include/tt.h
new file mode 100644
index 0000000..b8e1a2e
--- /dev/null
+++ b/include/tt.h
@@ -0,0 +1,62 @@
+/*
+  This file is part of ctak.
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with ctak. If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#ifndef TT_H
+#define TT_H
+
+#include <stdint.h>
+
+#include <actions.h>
+
+// ===================================================================
+// Types
+// ===================================================================
+
+enum TT_FLAG { TT_EXACT, TT_LOWERBOUND, TT_UPPERBOUND };
+
+typedef struct tt_node_s {
+  uint16_t gen;
+  uint64_t key;
+  enum TT_FLAG flag;
+  uint8_t depth;
+  float value;
+  action_t action;
+} tt_entry_t;
+
+// ===================================================================
+// Variables
+// ===================================================================
+
+// Direct-mapped hash table (no chaining); one slot per key.
+#define TT_SIZE ((uint32_t)((1 << 19) - 1))
+
+// ===================================================================
+// Methods
+// ===================================================================
+
+// Bump the generation counter, invalidating all entries (memsets the
+// table on wraparound). Called from negamax_init when the board size
+// (and hence the zobrist table) changes; entries are otherwise kept
+// across plies on purpose (see negamax.c).
+int tt_init(void);
+
+tt_entry_t *tt_seek(const uint64_t key);
+
+int tt_insert(const uint64_t key, const enum TT_FLAG flag, const uint8_t depth,
+              const float value, const action_t action);
+
+#endif