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HNSW: implement last resort node reallocation.

This commit is contained in:
antirez 2025-03-13 11:30:07 +01:00
parent 095842a748
commit 9500539c55
1 changed files with 27 additions and 4 deletions
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31
hnsw.c
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@ -1085,10 +1085,33 @@ void select_neighbors(HNSW *index, pqueue *candidates, hnswNode *new_node,
} else {
/* Otherwise we have no other option than reallocating
* the max number of links for this target node, and
* ensure at least a few connections for our new node.
*
* XXX: Implement this part. */
debugmsg("Node overbooking needed: allocate more\n");
* ensure at least a few connections for our new node. */
uint32_t reallocation_limit = layer == 0 ?
index->M * 3 : index->M *2;
if (neighbor->layers[layer].max_links >= reallocation_limit)
continue;
uint32_t new_max_links = neighbor->layers[layer].max_links+1;
hnswNode **new_links = hrealloc(neighbor->layers[layer].links,
sizeof(hnswNode*) * new_max_links);
if (new_links == NULL) continue; // Non critical.
/* Update neighbor's link capacity. */
neighbor->layers[layer].links = new_links;
neighbor->layers[layer].max_links = new_max_links;
/* Establish bidirectional link. */
uint32_t n = neighbor->layers[layer].num_links;
neighbor->layers[layer].links[n] = new_node;
neighbor->layers[layer].num_links++;
hnsw_update_worst_neighbor_on_add(index, neighbor, layer,
n, dist);
n = new_node->layers[layer].num_links;
new_node->layers[layer].links[n] = neighbor;
new_node->layers[layer].num_links++;
hnsw_update_worst_neighbor_on_add(index, new_node, layer,
n, dist);
continue;
}
}