diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index a0c0a7b..c5e8053 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -702,7 +702,22 @@ int getChildGeq(Node *self, int child) {
   } else if (self->type == Type::Node16) {
     auto *self16 = static_cast<Node16 *>(self);
 #ifdef HAS_AVX
-// TODO
+    __m128i key_vec = _mm_set1_epi8(child);
+    __m128i indices;
+    memcpy(&indices, self16->index, sizeof(self16->index));
+    __m128i results = _mm_cmpeq_epi8(key_vec, _mm_min_epu8(key_vec, indices));
+    int mask = (1 << self16->numChildren) - 1;
+    int bitfield = _mm_movemask_epi8(results) & mask;
+    int result = bitfield == 0 ? -1 : self16->index[__builtin_ctz(bitfield)];
+    assert(result == [&]() -> int {
+      for (int i = 0; i < self16->numChildren; ++i) {
+        if (self16->index[i] >= child) {
+          return self16->index[i];
+        }
+      }
+      return -1;
+    }());
+    return result;
 #elif defined(HAS_ARM_NEON)
     uint8x16_t indices;
     memcpy(&indices, self16->index, sizeof(self16->index));
@@ -790,7 +805,23 @@ int getChildLeq(Node *self, int child) {
   } else if (self->type == Type::Node16) {
     auto *self16 = static_cast<Node16 *>(self);
 #ifdef HAS_AVX
-// TODO
+    __m128i key_vec = _mm_set1_epi8(child);
+    __m128i indices;
+    memcpy(&indices, self16->index, sizeof(self16->index));
+    __m128i results = _mm_cmpeq_epi8(key_vec, _mm_max_epu8(key_vec, indices));
+    int mask = (1 << self16->numChildren) - 1;
+    int bitfield = _mm_movemask_epi8(results) & mask;
+    int result =
+        bitfield == 0 ? -1 : self16->index[31 - __builtin_clz(bitfield)];
+    assert(result == [&]() -> int {
+      for (int i = self16->numChildren - 1; i >= 0; --i) {
+        if (self16->index[i] <= child) {
+          return self16->index[i];
+        }
+      }
+      return -1;
+    }());
+    return result;
 #elif defined(HAS_ARM_NEON)
     uint8x16_t indices;
     memcpy(&indices, self16->index, sizeof(self16->index));
@@ -1540,4 +1571,4 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
 }
 #endif
 
-// GCOVR_EXCL_STOP
\ No newline at end of file
+// GCOVR_EXCL_STOP