Cleanup comments and some code reorg.

passed STC:
https://tests.stockfishchess.org/tests/view/6536dc7dcc309ae83955b04d
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 58048 W: 14693 L: 14501 D: 28854
Ptnml(0-2): 200, 6399, 15595, 6669, 161

closes https://github.com/official-stockfish/Stockfish/pull/4846

No functional change

src/evaluate.cpp

@@ -123,11 +123,11 @@ void NNUE::verify() {
         std::string msg1 =
           "Network evaluation parameters compatible with the engine must be available.";
         std::string msg2 = "The network file " + eval_file + " was not loaded successfully.";
-        std::string msg3 =
+        std::string msg3 = "The UCI option EvalFile might need to specify the full path, "
-          "The UCI option EvalFile might need to specify the full path, including the directory name, to the network file.";
+                           "including the directory name, to the network file.";
-        std::string msg4 =
+        std::string msg4 = "The default net can be downloaded from: "
-          "The default net can be downloaded from: https://tests.stockfishchess.org/api/nn/"
+                           "https://tests.stockfishchess.org/api/nn/"
-          + std::string(EvalFileDefaultName);
+                         + std::string(EvalFileDefaultName);
         std::string msg5 = "The engine will be terminated now.";
 
         sync_cout << "info string ERROR: " << msg1 << sync_endl;

src/movepick.cpp

@@ -263,11 +263,9 @@ top:
 
     case GOOD_CAPTURE :
         if (select<Next>([&]() {
-                return pos.see_ge(*cur, Value(-cur->value))
+                // Move losing capture to endBadCaptures to be tried later
-                       ?
+                return pos.see_ge(*cur, Value(-cur->value)) ? true
-                       // Move losing capture to endBadCaptures to be tried later
+                                                            : (*endBadCaptures++ = *cur, false);
-                         true
-                       : (*endBadCaptures++ = *cur, false);
             }))
             return *(cur - 1);
 

src/nnue/evaluate_nnue.cpp

@@ -407,8 +407,8 @@ bool save_eval(const std::optional<std::string>& filename) {
     {
         if (currentEvalFileName != EvalFileDefaultName)
         {
-            msg =
+            msg = "Failed to export a net. "
-              "Failed to export a net. A non-embedded net can only be saved if the filename is specified";
+                  "A non-embedded net can only be saved if the filename is specified";
 
             sync_cout << msg << sync_endl;
             return false;

src/nnue/layers/affine_transform.h

@@ -256,7 +256,8 @@ class AffineTransform {
         else if constexpr (OutputDimensions == 1)
         {
 
-    // We cannot use AVX512 for the last layer because there's only 32 inputs and the buffer is not padded to 64 elements.
+    // We cannot use AVX512 for the last layer because there are only 32 inputs
+    // and the buffer is not padded to 64 elements.
     #if defined(USE_AVX2)
             using vec_t = __m256i;
         #define vec_setzero _mm256_setzero_si256

src/nnue/nnue_architecture.h

@@ -113,8 +113,8 @@ struct Network {
         ac_1.propagate(buffer.fc_1_out, buffer.ac_1_out);
         fc_2.propagate(buffer.ac_1_out, buffer.fc_2_out);
 
-        // buffer.fc_0_out[FC_0_OUTPUTS] is such that 1.0 is equal to 127*(1<<WeightScaleBits) in quantized form
+        // buffer.fc_0_out[FC_0_OUTPUTS] is such that 1.0 is equal to 127*(1<<WeightScaleBits) in
-        // but we want 1.0 to be equal to 600*OutputScale
+        // quantized form, but we want 1.0 to be equal to 600*OutputScale
         std::int32_t fwdOut =
           int(buffer.fc_0_out[FC_0_OUTPUTS]) * (600 * OutputScale) / (127 * (1 << WeightScaleBits));
         std::int32_t outputValue = buffer.fc_2_out[0] + fwdOut;

src/nnue/nnue_feature_transformer.h

@@ -338,8 +338,10 @@ class FeatureTransformer {
 
     // NOTE: The parameter states_to_update is an array of position states, ending with nullptr.
     //       All states must be sequential, that is states_to_update[i] must either be reachable
-    //       by repeatedly applying ->previous from states_to_update[i+1] or states_to_update[i] == nullptr.
+    //       by repeatedly applying ->previous from states_to_update[i+1] or
-    //       computed_st must be reachable by repeatedly applying ->previous on states_to_update[0], if not nullptr.
+    //       states_to_update[i] == nullptr.
+    //       computed_st must be reachable by repeatedly applying ->previous on
+    //       states_to_update[0], if not nullptr.
     template<Color Perspective, size_t N>
     void update_accumulator_incremental(const Position& pos,
                                         StateInfo*      computed_st,

src/search.cpp

@@ -379,8 +379,8 @@ void Thread::search() {
             int failedHighCnt = 0;
             while (true)
             {
-                // Adjust the effective depth searched, but ensure at least one effective increment for every
+                // Adjust the effective depth searched, but ensure at least one effective increment
-                // four searchAgain steps (see issue #2717).
+                // for every four searchAgain steps (see issue #2717).
                 Depth adjustedDepth =
                   std::max(1, rootDepth - failedHighCnt - 3 * (searchAgainCounter + 1) / 4);
                 bestValue = Stockfish::search<Root>(rootPos, ss, alpha, beta, adjustedDepth, false);
@@ -633,7 +633,8 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
                 if (!ttCapture)
                     update_quiet_stats(pos, ss, ttMove, stat_bonus(depth));
 
-                // Extra penalty for early quiet moves of the previous ply (~0 Elo on STC, ~2 Elo on LTC)
+                // Extra penalty for early quiet moves of
+                // the previous ply (~0 Elo on STC, ~2 Elo on LTC).
                 if (prevSq != SQ_NONE && (ss - 1)->moveCount <= 2 && !priorCapture)
                     update_continuation_histories(ss - 1, pos.piece_on(prevSq), prevSq,
                                                   -stat_bonus(depth + 1));
@@ -715,7 +716,8 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
     }
     else if (excludedMove)
     {
-        // Providing the hint that this node's accumulator will be used often brings significant Elo gain (~13 Elo)
+        // Providing the hint that this node's accumulator will be used often
+        // brings significant Elo gain (~13 Elo).
         Eval::NNUE::hint_common_parent_position(pos);
         eval = ss->staticEval;
     }
@@ -817,8 +819,9 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
         }
     }
 
-    // Step 10. If the position doesn't have a ttMove, decrease depth by 2
+    // Step 10. If the position doesn't have a ttMove, decrease depth by 2,
-    // (or by 4 if the TT entry for the current position was hit and the stored depth is greater than or equal to the current depth).
+    // or by 4 if the TT entry for the current position was hit and
+    // the stored depth is greater than or equal to the current depth.
     // Use qsearch if depth is equal or below zero (~9 Elo)
     if (PvNode && !ttMove)
         depth -= 2 + 2 * (ss->ttHit && tte->depth() >= depth);
@@ -967,13 +970,15 @@ moves_loop:  // When in check, search starts here
             if (capture || givesCheck)
             {
                 // Futility pruning for captures (~2 Elo)
-                if (!givesCheck && lmrDepth < 7 && !ss->inCheck
+                if (!givesCheck && lmrDepth < 7 && !ss->inCheck)
-                    && ss->staticEval + 188 + 206 * lmrDepth + PieceValue[pos.piece_on(to_sq(move))]
+                {
-                           + captureHistory[movedPiece][to_sq(move)]
+                    Piece capturedPiece = pos.piece_on(to_sq(move));
-                                           [type_of(pos.piece_on(to_sq(move)))]
+                    int   futilityEval =
-                               / 7
+                      ss->staticEval + 188 + 206 * lmrDepth + PieceValue[capturedPiece]
-                         < alpha)
+                      + captureHistory[movedPiece][to_sq(move)][type_of(capturedPiece)] / 7;
-                    continue;
+                    if (futilityEval < alpha)
+                        continue;
+                }
 
                 // SEE based pruning for captures and checks (~11 Elo)
                 if (!pos.see_ge(move, Value(-185) * depth))
@@ -1018,9 +1023,9 @@ moves_loop:  // When in check, search starts here
             // that depth margin and singularBeta margin are known for having non-linear
             // scaling. Their values are optimized to time controls of 180+1.8 and longer
             // so changing them requires tests at this type of time controls.
-            if (!rootNode
+            // Recursive singular search is avoided.
+            if (!rootNode && move == ttMove && !excludedMove
                 && depth >= 4 - (thisThread->completedDepth > 24) + 2 * (PvNode && tte->is_pv())
-                && move == ttMove && !excludedMove  // Avoid recursive singular search
                 && abs(ttValue) < VALUE_TB_WIN_IN_MAX_PLY && (tte->bound() & BOUND_LOWER)
                 && tte->depth() >= depth - 3)
             {
@@ -1053,7 +1058,7 @@ moves_loop:  // When in check, search starts here
                 else if (singularBeta >= beta)
                     return singularBeta;
 
-                // If the eval of ttMove is greater than beta, we reduce it (negative extension) (~7 Elo)
+                // If the eval of ttMove is greater than beta, reduce it (negative extension) (~7 Elo)
                 else if (ttValue >= beta)
                     extension = -2 - !PvNode;
 
@@ -1061,7 +1066,7 @@ moves_loop:  // When in check, search starts here
                 else if (cutNode)
                     extension = depth < 19 ? -2 : -1;
 
-                // If the eval of ttMove is less than value, we reduce it (negative extension) (~1 Elo)
+                // If the eval of ttMove is less than value, reduce it (negative extension) (~1 Elo)
                 else if (ttValue <= value)
                     extension = -1;
             }

src/uci.cpp

@@ -178,8 +178,9 @@ void bench(Position& pos, std::istream& args, StateListPtr& states) {
     uint64_t    num, nodes = 0, cnt = 1;
 
     std::vector<std::string> list = setup_bench(pos, args);
-    num                           = count_if(list.begin(), list.end(),
+
-                                             [](const std::string& s) { return s.find("go ") == 0 || s.find("eval") == 0; });
+    num = count_if(list.begin(), list.end(),
+                   [](const std::string& s) { return s.find("go ") == 0 || s.find("eval") == 0; });
 
     TimePoint elapsed = now();