Speed up update_accumulator_refresh_cache with AVX512ICL

Passed STC:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 212960 W: 55550 L: 54991 D: 102419
Ptnml(0-2): 583, 23688, 57393, 24219, 597
https://tests.stockfishchess.org/tests/view/69ab916ccb31ee884aed62ea

closes https://github.com/official-stockfish/Stockfish/pull/6657

No functional change

src/nnue/features/half_ka_v2_hm.cpp

@@ -27,6 +27,75 @@
 
 namespace Stockfish::Eval::NNUE::Features {
 
+#if defined(USE_AVX512ICL)
+void HalfKAv2_hm::write_indices(const std::array<Piece, SQUARE_NB>& oldPieces,
+                                const std::array<Piece, SQUARE_NB>& newPieces,
+                                Bitboard                            removedBB,
+                                Bitboard                            addedBB,
+                                Color                               perspective,
+                                Square                              ksq,
+                                IndexList&                          removed,
+                                IndexList&                          added) {
+
+    auto* write_removed = removed.make_space(popcount(removedBB));
+    auto* write_added   = added.make_space(popcount(addedBB));
+
+    const __m512i vecOldPieces = _mm512_loadu_si512(oldPieces.data());
+    const __m512i vecNewPieces = _mm512_loadu_si512(newPieces.data());
+
+    static constexpr uint16_t psiTable[COLOR_NB][32] = {
+      {PS_NONE, PS_W_PAWN, PS_W_KNIGHT, PS_W_BISHOP, PS_W_ROOK, PS_W_QUEEN, PS_KING, PS_NONE,
+       PS_NONE, PS_B_PAWN, PS_B_KNIGHT, PS_B_BISHOP, PS_B_ROOK, PS_B_QUEEN, PS_KING, PS_NONE,
+       PS_NONE, PS_NONE,   PS_NONE,     PS_NONE,     PS_NONE,   PS_NONE,    PS_NONE, PS_NONE,
+       PS_NONE, PS_NONE,   PS_NONE,     PS_NONE,     PS_NONE,   PS_NONE,    PS_NONE, PS_NONE},
+
+      {PS_NONE, PS_B_PAWN, PS_B_KNIGHT, PS_B_BISHOP, PS_B_ROOK, PS_B_QUEEN, PS_KING, PS_NONE,
+       PS_NONE, PS_W_PAWN, PS_W_KNIGHT, PS_W_BISHOP, PS_W_ROOK, PS_W_QUEEN, PS_KING, PS_NONE,
+       PS_NONE, PS_NONE,   PS_NONE,     PS_NONE,     PS_NONE,   PS_NONE,    PS_NONE, PS_NONE,
+       PS_NONE, PS_NONE,   PS_NONE,     PS_NONE,     PS_NONE,   PS_NONE,    PS_NONE, PS_NONE}};
+    const __m512i psi = _mm512_loadu_si512(psiTable[perspective]);
+
+    const __m512i allSquares = _mm512_set_epi8(
+      63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41,
+      40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18,
+      17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0);
+
+    const uint16_t flip   = 56 * perspective;
+    const __m512i  orient = _mm512_set1_epi16((uint16_t) OrientTBL[ksq] ^ flip);
+    const __m512i  bucket = _mm512_set1_epi16((uint16_t) KingBuckets[int(ksq) ^ flip]);
+
+    __m512i removed_squares       = _mm512_maskz_compress_epi8(removedBB, allSquares);
+    __m512i removed_pieces        = _mm512_permutexvar_epi8(removed_squares, vecOldPieces);
+    removed_squares               = _mm512_cvtepi8_epi16(_mm512_castsi512_si256(removed_squares));
+    removed_pieces                = _mm512_cvtepi8_epi16(_mm512_castsi512_si256(removed_pieces));
+    const __m512i removed_psi     = _mm512_permutexvar_epi16(removed_pieces, psi);
+    __m512i       removed_indices = _mm512_xor_si512(removed_squares, orient);
+    removed_indices               = _mm512_add_epi16(removed_indices, removed_psi);
+    removed_indices               = _mm512_add_epi16(removed_indices, bucket);
+
+    __m512i added_squares       = _mm512_maskz_compress_epi8(addedBB, allSquares);
+    __m512i added_pieces        = _mm512_permutexvar_epi8(added_squares, vecNewPieces);
+    added_squares               = _mm512_cvtepi8_epi16(_mm512_castsi512_si256(added_squares));
+    added_pieces                = _mm512_cvtepi8_epi16(_mm512_castsi512_si256(added_pieces));
+    const __m512i added_psi     = _mm512_permutexvar_epi16(added_pieces, psi);
+    __m512i       added_indices = _mm512_xor_si512(added_squares, orient);
+    added_indices               = _mm512_add_epi16(added_indices, added_psi);
+    added_indices               = _mm512_add_epi16(added_indices, bucket);
+
+    const __m512i removed_indices0 = _mm512_cvtepi16_epi32(_mm512_castsi512_si256(removed_indices));
+    const __m512i removed_indices1 =
+      _mm512_cvtepi16_epi32(_mm512_extracti64x4_epi64(removed_indices, 1));
+    _mm512_storeu_si512(write_removed, removed_indices0);
+    _mm512_storeu_si512(write_removed + 16, removed_indices1);
+
+    const __m512i added_indices0 = _mm512_cvtepi16_epi32(_mm512_castsi512_si256(added_indices));
+    const __m512i added_indices1 =
+      _mm512_cvtepi16_epi32(_mm512_extracti64x4_epi64(added_indices, 1));
+    _mm512_storeu_si512(write_added, added_indices0);
+    _mm512_storeu_si512(write_added + 16, added_indices1);
+}
+#endif
+
 // Index of a feature for a given king position and another piece on some square
 
 IndexType HalfKAv2_hm::make_index(Color perspective, Square s, Piece pc, Square ksq) {

src/nnue/features/half_ka_v2_hm.h

@@ -106,6 +106,18 @@ class HalfKAv2_hm {
     using IndexList                                = ValueList<IndexType, MaxActiveDimensions>;
     using DiffType                                 = DirtyPiece;
 
+#if defined(USE_AVX512ICL)
+    // Compute all changed feature indices and write them to the given lists
+    static void write_indices(const std::array<Piece, SQUARE_NB>& oldPieces,
+                              const std::array<Piece, SQUARE_NB>& newPieces,
+                              Bitboard                            removedBB,
+                              Bitboard                            addedBB,
+                              Color                               perspective,
+                              Square                              ksq,
+                              IndexList&                          removed,
+                              IndexList&                          added);
+#endif
+
     // Index of a feature for a given king position and another piece on some square
 
     static IndexType make_index(Color perspective, Square s, Piece pc, Square ksq);

src/nnue/nnue_accumulator.cpp

@@ -710,6 +710,10 @@ void update_accumulator_refresh_cache(Color                                 pers
     Bitboard       removedBB = changedBB & entry.pieceBB;
     Bitboard       addedBB   = changedBB & pos.pieces();
 
+#if defined(USE_AVX512ICL)
+    PSQFeatureSet::write_indices(entry.pieces, pos.piece_array(), removedBB, addedBB, perspective,
+                                 ksq, removed, added);
+#else
     while (removedBB)
     {
         Square sq = pop_lsb(removedBB);
@@ -720,6 +724,7 @@ void update_accumulator_refresh_cache(Color                                 pers
         Square sq = pop_lsb(addedBB);
         added.push_back(PSQFeatureSet::make_index(perspective, sq, pos.piece_on(sq), ksq));
     }
+#endif
 
     entry.pieceBB = pos.pieces();
     entry.pieces  = pos.piece_array();