Phase A NNUE: feature-indexing spec, annotation/training pipeline, dump nnuefeatures

Builds out the NNUE Phase A prototype per docs/NNUE.md:

- src/nnuefeatures.c: standalone HalfKAv2_hm feature-index reference
  implementation (new `dump nnuefeatures` command), sourced from
  Stockfish's half_ka_v2_hm.{h,cpp} (sf_16 tag), including the 0x88->64
  square conversion typhoon's own board representation needs.
- annotate_pgns/: sharded TWIC/self-play annotation harness
  (annotate.py), position extraction, quiet-position filtering (flat
  and game-shaped, plus an upstream --prefilter-quiet option),
  train/holdout game-level stratified split, WDL-sigmoid K fitting,
  the Python HalfKAv2_hm reference encoder (nnue_feature_spec.py) and
  its bit-for-bit cross-checker against the C side
  (cross_check_features.py), and a first PyTorch training pipeline
  (nnue_model.py, nnue_train.py, build_training_tensors.py) -- a
  256x2-32-32-1-ish net trained locally on CPU against ~1.85M quiet
  TWIC positions as a pipeline/framework validation pass.
- Finish an in-progress InitMagic/InitLMRTable/InitEval ->
  InitializeBitboardMagic/InitializeLMRTable/InitializeEval rename:
  chess.h's prototypes hadn't been updated to match the already-renamed
  definitions/call sites, leaving 4 implicit-function-declaration
  warnings.
- tests/arasan.epd: new curated EPD suite.
- docs/: add the project's design docs (previously untracked).

Co-Authored-By: Claude Sonnet 5 <[email protected]>

1 files changed, 28 insertions, 32 deletions

diff --git a/src/main.c b/src/main.c
index 3c6352a..ad954ad 100644
--- a/src/main.c
+++ b/src/main.c
@@ -49,7 +49,7 @@ Return value:
     char *p;
 
     Trace("Typhoon %s (built on %s %s, commit %s):\n", VERSION, __DATE__, __TIME__, GIT_COMMIT);
-    Trace("    Copyright (C) 2000-2007, Scott Gasch ([email protected])\n");
+    Trace("    Copyright (C) 2000-2026, Scott Gasch ([email protected])\n");
     Trace("    " REVISION);
     Trace("    " COMPILER_STRING);
     Trace("    Make profile used: %s\n", PROFILE);
@@ -125,7 +125,7 @@ Return value:
 
 
 FLAG
-BeginLogging(void)
+InitializeLogging(void)
 /**
 
 Routine description:
@@ -150,19 +150,24 @@ Return value:
         return(FALSE);
     }
 
-    // If the logfile we want to write already exists, back it up.
-    if (TRUE == SystemDoesFileExist(g_Options.szLogfile)) {
-        VERIFY(BackupFile(g_Options.szLogfile));
-    }
-    ASSERT(FALSE == SystemDoesFileExist(g_Options.szLogfile));
-
-    g_pfLogfile = fopen(g_Options.szLogfile, "wb+");
+    // If the logfile we want to write already exists, append to it.
+    FLAG fReusingLogfile = SystemDoesFileExist(g_Options.szLogfile);
+    g_pfLogfile = fopen(g_Options.szLogfile, "ab+");
     if (NULL == g_pfLogfile) {
         Trace("WARNING: Can't open logfile %s for write (%s); "
               "continuing without logging.\n",
               g_Options.szLogfile, strerror(errno));
         return(FALSE);
     }
+    if (TRUE == fReusingLogfile) {
+        time_t tNow = time(NULL);
+        CHAR szTimestamp[64];
+        strftime(szTimestamp, sizeof(szTimestamp), "%Y-%m-%d %H:%M:%S",
+                 localtime(&tNow));
+        fprintf(g_pfLogfile,
+                "----- New engine run re-using this logfile (%s) -----\n",
+                szTimestamp);
+    }
     return(TRUE);
 }
 
@@ -491,21 +496,12 @@ Return value:
 
 **/
 {
-    {
-        // 2026-09-16 diagnostic: allow forcing a fixed srand seed via
-        // TYPHOON_SEED for reproducing a specific run bit-for-bit
-        // (there's no --seed command-line flag) -- e.g. re-running the
-        // same debug_smoke_test.sh repro file to check whether a
-        // failure is deterministic or a genuine SMP timing race.
-        // TEMPORARY: revert once the split.c investigation is done,
-        // this isn't meant to be a permanent CLI feature.
-        const char *pszForcedSeed = getenv("TYPHOON_SEED");
-        unsigned int uSeed = pszForcedSeed ?
-            (unsigned int)strtoul(pszForcedSeed, NULL, 10) :
-            (unsigned int)time(0);
-        Trace("srand seed: %u\n", uSeed);
-        srand(uSeed);
-    }
+    const char *pszForcedSeed = getenv("TYPHOON_SEED");
+    unsigned int uSeed = pszForcedSeed ?
+        (UINT)strtoul(pszForcedSeed, NULL, 10) :
+        (UINT)time(0);
+    Trace("srand seed: %u\n", uSeed);
+    srand(uSeed);
     InitializeOptions(argc, argv);
     InitializeTreeDump();
     InitializeEGTB();
@@ -520,17 +516,17 @@ Return value:
     InitializeKnightAttackTables();
     InitializeKingAttackTables();
     InitializePawnAttackOriginTable();
-    InitMagic();
+    InitializeBitboardMagic();
     InitializeOpeningBook();
     InitializeDynamicMoveOrdering();
-    InitLMRTable();
+    InitializeLMRTable();
     InitializeHashSystem();
-    InitEval();
+    InitializeEval();
 #ifdef MP
     InitializeParallelSearch();
 #endif
     VERIFY(PreGameReset(TRUE));
-    (void)BeginLogging();
+    InitializeLogging();
     return TRUE;
 }
 
@@ -825,10 +821,10 @@ Return value:
     {
         g_uInputThreadHandle = InitInputSystemWithDedicatedThread();
     }
-    
+
     // Enter the main work loop code...
-    MainProgramLoop();  
-    
+    MainProgramLoop();
+
     // If we get here g_fExitProgram is set -- clean up.
     Trace("MAIN THREAD: thread terminating.\n");
     if (FALSE == MainProgramCleanup())
@@ -836,5 +832,5 @@ Return value:
         Trace("main: Main program cleanup code failed, aborting.\n");
         exit(-1);
     }
-    exit(0); 
+    exit(0);
 }