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, 60 insertions, 0 deletions

diff --git a/include/tt.c b/include/tt.c
new file mode 100644
index 0000000..b1f583e
--- /dev/null
+++ b/include/tt.c
@@ -0,0 +1,60 @@
+/*
+  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/>.
+*/
+
+#include "tt.h"
+#include <string.h>
+
+// ===================================================================
+// Variables
+// ===================================================================
+
+static tt_entry_t table[TT_SIZE + 1];
+static uint16_t tt_gen = 0;
+
+// ===================================================================
+// Exported functions
+// ===================================================================
+
+int tt_init(void) {
+  tt_gen++;
+  if (tt_gen == 0)
+    memset(table, 0, sizeof(table));
+  return EXIT_SUCCESS;
+}
+
+tt_entry_t *tt_seek(const uint64_t key) {
+  tt_entry_t *e = &table[key & TT_SIZE];
+  if (e->gen == tt_gen && e->key == key)
+    return e;
+  return NULL;
+}
+
+int tt_insert(const uint64_t key, const enum TT_FLAG flag,
+              const uint8_t depth, const float value,
+              const action_t action) {
+  tt_entry_t *e = &table[key & TT_SIZE];
+  // Replacement scheme: keep a stale-but-deeper entry over a shallower new one.
+  if (e->gen == tt_gen && e->depth > depth)
+    return EXIT_SUCCESS;
+  e->key = key;
+  e->value = value;
+  e->action = action;
+  e->gen = tt_gen;
+  e->flag = flag;
+  e->depth = depth;
+  return EXIT_SUCCESS;
+}