Remove bogus assert

Unsigned compare is incorrect here

ConflictSet.cpp

@@ -766,6 +766,8 @@ private:
 
 int getNodeIndex(Node3 *self, uint8_t index) {
   Node3 *n = (Node3 *)self;
+  assume(n->numChildren >= 1);
+  assume(n->numChildren <= 3);
   for (int i = 0; i < n->numChildren; ++i) {
     if (n->index[i] == index) {
       return i;
@@ -774,6 +776,18 @@ int getNodeIndex(Node3 *self, uint8_t index) {
   return -1;
 }
 
+int getNodeIndexExists(Node3 *self, uint8_t index) {
+  Node3 *n = (Node3 *)self;
+  assume(n->numChildren >= 1);
+  assume(n->numChildren <= 3);
+  for (int i = 0; i < n->numChildren; ++i) {
+    if (n->index[i] == index) {
+      return i;
+    }
+  }
+  __builtin_unreachable(); // GCOVR_EXCL_LINE
+}
+
 int getNodeIndex(Node16 *self, uint8_t index) {
 
 #ifdef HAS_AVX
@@ -834,13 +848,52 @@ int getNodeIndex(Node16 *self, uint8_t index) {
 #endif
 }
 
+int getNodeIndexExists(Node16 *self, uint8_t index) {
+
+#ifdef HAS_AVX
+  __m128i key_vec = _mm_set1_epi8(index);
+  __m128i indices;
+  memcpy(&indices, self->index, Node16::kMaxNodes);
+  __m128i results = _mm_cmpeq_epi8(key_vec, indices);
+  uint32_t mask = (1 << self->numChildren) - 1;
+  uint32_t bitfield = _mm_movemask_epi8(results) & mask;
+  assume(bitfield != 0);
+  return std::countr_zero(bitfield);
+#elif defined(HAS_ARM_NEON)
+  // Based on
+  // https://community.arm.com/arm-community-blogs/b/infrastructure-solutions-blog/posts/porting-x86-vector-bitmask-optimizations-to-arm-neon
+
+  uint8x16_t indices;
+  memcpy(&indices, self->index, Node16::kMaxNodes);
+  // 0xff for each match
+  uint16x8_t results =
+      vreinterpretq_u16_u8(vceqq_u8(vdupq_n_u8(index), indices));
+  assume(self->numChildren <= Node16::kMaxNodes);
+  uint64_t mask = self->numChildren == 16
+                      ? uint64_t(-1)
+                      : (uint64_t(1) << (self->numChildren * 4)) - 1;
+  // 0xf for each match in valid range
+  uint64_t bitfield =
+      vget_lane_u64(vreinterpret_u64_u8(vshrn_n_u16(results, 4)), 0) & mask;
+  assume(bitfield != 0);
+  return std::countr_zero(bitfield) / 4;
+#else
+  for (int i = 0; i < self->numChildren; ++i) {
+    if (self->index[i] == index) {
+      return i;
+    }
+  }
+  __builtin_unreachable(); // GCOVR_EXCL_LINE
+#endif
+}
+
 // Precondition - an entry for index must exist in the node
 Node *&getChildExists(Node3 *self, uint8_t index) {
-  return self->children[getNodeIndex(self, index)];
+  return self->children[getNodeIndexExists(self, index)];
 }
 // Precondition - an entry for index must exist in the node
 Node *&getChildExists(Node16 *self, uint8_t index) {
-  return self->children[getNodeIndex(self, index)];
+  return self->children[getNodeIndexExists(self, index)];
 }
 // Precondition - an entry for index must exist in the node
 Node *&getChildExists(Node48 *self, uint8_t index) {
@@ -885,12 +938,12 @@ InternalVersionT maxVersion(Node *n) {
     __builtin_unreachable(); // GCOVR_EXCL_LINE
   case Type_Node3: {
     auto *n3 = static_cast<Node3 *>(n);
-    int i = getNodeIndex(n3, index);
+    int i = getNodeIndexExists(n3, index);
     return n3->childMaxVersion[i];
   }
   case Type_Node16: {
     auto *n16 = static_cast<Node16 *>(n);
-    int i = getNodeIndex(n16, index);
+    int i = getNodeIndexExists(n16, index);
     return n16->childMaxVersion[i];
   }
   case Type_Node48: {
@@ -918,12 +971,12 @@ InternalVersionT exchangeMaxVersion(Node *n, InternalVersionT newMax) {
     __builtin_unreachable(); // GCOVR_EXCL_LINE
   case Type_Node3: {
     auto *n3 = static_cast<Node3 *>(n);
-    int i = getNodeIndex(n3, index);
+    int i = getNodeIndexExists(n3, index);
     return std::exchange(n3->childMaxVersion[i], newMax);
   }
   case Type_Node16: {
     auto *n16 = static_cast<Node16 *>(n);
-    int i = getNodeIndex(n16, index);
+    int i = getNodeIndexExists(n16, index);
     return std::exchange(n16->childMaxVersion[i], newMax);
   }
   case Type_Node48: {
@@ -952,13 +1005,13 @@ void setMaxVersion(Node *n, InternalVersionT newMax) {
     __builtin_unreachable(); // GCOVR_EXCL_LINE
   case Type_Node3: {
     auto *n3 = static_cast<Node3 *>(n);
-    int i = getNodeIndex(n3, index);
+    int i = getNodeIndexExists(n3, index);
     n3->childMaxVersion[i] = newMax;
     return;
   }
   case Type_Node16: {
     auto *n16 = static_cast<Node16 *>(n);
-    int i = getNodeIndex(n16, index);
+    int i = getNodeIndexExists(n16, index);
     n16->childMaxVersion[i] = newMax;
     return;
   }
@@ -1070,6 +1123,8 @@ ChildAndMaxVersion getChildAndMaxVersion(Node *self, uint8_t index) {
 Node *getChildGeq(Node0 *, int) { return nullptr; }
 
 Node *getChildGeq(Node3 *n, int child) {
+  assume(n->numChildren >= 1);
+  assume(n->numChildren <= 3);
   for (int i = 0; i < n->numChildren; ++i) {
     if (n->index[i] >= child) {
       return n->children[i];
@@ -1549,7 +1604,6 @@ __attribute__((target("avx512f"))) void rezero16(InternalVersionT *vs,
       _mm512_sub_epi32(_mm512_loadu_epi32(vs), zvec), _mm512_setzero_epi32());
   _mm512_mask_storeu_epi32(vs, m, zvec);
 }
-
 __attribute__((target("default")))
 #endif
 
@@ -2416,6 +2470,7 @@ checkMaxBetweenExclusive(Node *n, int begin, int end,
 }
 __attribute__((target("default")))
 #endif
+
 bool checkMaxBetweenExclusive(Node *n, int begin, int end,
                          InternalVersionT readVersion, ReadContext *tls) {
   return checkMaxBetweenExclusiveImpl<false>(n, begin, end, readVersion, tls);
@@ -2855,6 +2910,72 @@ void addPointWrite(Node *&root, std::span<const uint8_t> key,
   }
 }
 
+#if defined(HAS_AVX) && !defined(__SANITIZE_THREAD__)
+__attribute__((target("avx512f"))) InternalVersionT
+horizontalMaxUpTo16(InternalVersionT *vs, InternalVersionT z, int len) {
+  assume(len <= 16);
+#if USE_64_BIT
+  // Hope it gets vectorized
+  InternalVersionT max = vs[0];
+  for (int i = 1; i < len; ++i) {
+    max = std::max(vs[i], max);
+  }
+  return max;
+#else
+  uint32_t zero;
+  memcpy(&zero, &z, sizeof(zero));
+  auto zeroVec = _mm512_set1_epi32(zero);
+  auto max = InternalVersionT(
+      zero +
+      _mm512_reduce_max_epi32(_mm512_sub_epi32(
+          _mm512_mask_loadu_epi32(zeroVec, _mm512_int2mask((1 << len) - 1), vs),
+          zeroVec)));
+  return max;
+#endif
+}
+__attribute__((target("default")))
+#endif
+
+InternalVersionT
+horizontalMaxUpTo16(InternalVersionT *vs, InternalVersionT, int len) {
+  assume(len <= 16);
+  InternalVersionT max = vs[0];
+  for (int i = 1; i < len; ++i) {
+    max = std::max(vs[i], max);
+  }
+  return max;
+}
+
+#if defined(HAS_AVX) && !defined(__SANITIZE_THREAD__)
+__attribute__((target("avx512f"))) InternalVersionT
+horizontalMax16(InternalVersionT *vs, InternalVersionT z) {
+#if USE_64_BIT
+  // Hope it gets vectorized
+  InternalVersionT max = vs[0];
+  for (int i = 1; i < 16; ++i) {
+    max = std::max(vs[i], max);
+  }
+  return max;
+#else
+  uint32_t zero;
+  memcpy(&zero, &z, sizeof(zero));
+  auto zeroVec = _mm512_set1_epi32(zero);
+  return InternalVersionT(zero + _mm512_reduce_max_epi32(_mm512_sub_epi32(
+                                     _mm512_loadu_epi32(vs), zeroVec)));
+#endif
+}
+__attribute__((target("default")))
+#endif
+
+InternalVersionT
+horizontalMax16(InternalVersionT *vs, InternalVersionT) {
+  InternalVersionT max = vs[0];
+  for (int i = 1; i < 16; ++i) {
+    max = std::max(vs[i], max);
+  }
+  return max;
+}
+
 // Precondition: `node->entryPresent`, and node is not the root
 void fixupMaxVersion(Node *node, WriteContext *tls) {
   assert(node->parent);
@@ -2866,15 +2987,13 @@ void fixupMaxVersion(Node *node, WriteContext *tls) {
     break;
   case Type_Node3: {
     auto *self3 = static_cast<Node3 *>(node);
-    for (int i = 0; i < self3->numChildren; ++i) {
-      max = std::max(self3->childMaxVersion[i], max);
-    }
+    max = std::max(max, horizontalMaxUpTo16(self3->childMaxVersion, tls->zero,
+                                            self3->numChildren));
   } break;
   case Type_Node16: {
     auto *self16 = static_cast<Node16 *>(node);
-    for (int i = 0; i < self16->numChildren; ++i) {
-      max = std::max(self16->childMaxVersion[i], max);
-    }
+    max = std::max(max, horizontalMaxUpTo16(self16->childMaxVersion, tls->zero,
+                                            self16->numChildren));
   } break;
   case Type_Node48: {
     auto *self48 = static_cast<Node48 *>(node);
@@ -2884,9 +3003,7 @@ void fixupMaxVersion(Node *node, WriteContext *tls) {
   } break;
   case Type_Node256: {
     auto *self256 = static_cast<Node256 *>(node);
-    for (auto v : self256->maxOfMax) {
-      max = std::max(v, max);
-    }
+    max = std::max(max, horizontalMax16(self256->childMaxVersion, tls->zero));
   } break;
   default:                   // GCOVR_EXCL_LINE
     __builtin_unreachable(); // GCOVR_EXCL_LINE
@@ -3978,6 +4095,24 @@ template <int kN> void benchScan2() {
   });
 }
 
+void benchHorizontal16() {
+  ankerl::nanobench::Bench bench;
+  InternalVersionT vs[16];
+  for (int i = 0; i < 16; ++i) {
+    vs[i] = InternalVersionT(rand() % 1000 + 1000);
+  }
+#if !USE_64_BIT
+  InternalVersionT::zero = InternalVersionT(rand() % 1000);
+#endif
+  bench.run("horizontal16", [&]() {
+    bench.doNotOptimizeAway(horizontalMax16(vs, InternalVersionT::zero));
+  });
+  int x = rand() % 15 + 1;
+  bench.run("horizontalUpTo16", [&]() {
+    bench.doNotOptimizeAway(horizontalMaxUpTo16(vs, InternalVersionT::zero, x));
+  });
+}
+
 void benchLCP(int len) {
   ankerl::nanobench::Bench bench;
   std::vector<uint8_t> lhs(len);
@@ -4010,11 +4145,7 @@ void printTree() {
   debugPrintDot(stdout, cs.root, &cs);
 }
 
-int main(void) {
-  for (int i = 0; i < 256; ++i) {
-    benchLCP(i);
-  }
-}
+int main(void) { benchHorizontal16(); }
 #endif
 
 #ifdef ENABLE_FUZZ