Fix another invalid prefetch. Better output on range check error.

Author: michaelbautin

hnswlib/hnswalg.h

@@ -1111,7 +1111,9 @@ class HierarchicalNSW : public AlgorithmInterface<dist_t> {
                     tableint *datal = (tableint *) (data + 1);
                     HNSWLIB_MM_PREFETCH(getDataByInternalId(*datal), _MM_HINT_T0);
                     for (int i = 0; i < size; i++) {
-                        HNSWLIB_MM_PREFETCH(getDataByInternalId(*(datal + i + 1)), _MM_HINT_T0);
+                        if (i + 1 < size) {
+                            HNSWLIB_MM_PREFETCH(getDataByInternalId(*(datal + i + 1)), _MM_HINT_T0);
+                        }
                         tableint cand = datal[i];
                         dist_t d = fstdistfunc_(dataPoint, getDataByInternalId(cand), dist_func_param_);
                         if (d < curdist) {

hnswlib/hnswlib.h

@@ -437,7 +437,13 @@ class ChunkedArray {
     }
 
     char* operator[](size_t i) const {
+#ifndef NDEBUG
+        if (i >= getCapacity()) {
+            HNSWERR << "Chunked array index out of range: i="  << i
+                    << ", capacity=" << getCapacity() << std::endl;
+        }
         assert(i < getCapacity());
+#endif
         if (i >= getCapacity()) return nullptr;
         size_t chunk_index = i / elements_per_chunk_;
         size_t index_in_chunk = i % elements_per_chunk_;