search.py

from argparse import ArgumentParser
import json
import numpy as np 
import os
import faiss
import time
from multiprocessing.pool import  Pool
import cohere 
import zstandard

cohere_key = os.environ["COHERE_API_KEY"]
co = cohere.Client(cohere_key)

faiss.omp_set_num_threads(4)

def get_bin_embedding(query, model):
    query_emb = np.asarray(co.embed(texts=[query], model=model, input_type="search_query").embeddings)
    query_emb_bin = np.zeros_like(query_emb, dtype=np.int8)
    query_emb_bin[query_emb > 0] = 1
    query_emb_bin = np.packbits(query_emb_bin, axis=-1)
    return query_emb, query_emb_bin



def search_cluster(args):
    #1) Open Centroid
    with open(os.path.join(args['input_path'], f"emb/{args['cid_folder']}/{args['cid']}.npy"), "rb") as fIn:
        cluster_emb = np.load(fIn)
        cluster_index = faiss.IndexBinaryFlat(cluster_emb.shape[1]*8)
        cluster_index.add(cluster_emb)

    #2) Search
    cluster_scores, cluster_doc_ids = cluster_index.search(args['query_emb_bin'], args['topk'])
    
    return [{'cid': args['cid'], 'doc_idx': doc_idx, 'doc_score': doc_score, 'doc_emb': cluster_emb[doc_idx]} for doc_score, doc_idx in zip(cluster_scores[0], cluster_doc_ids[0])]

def search(args, centroids, query):
    num_rescore = args.topk*5 

    #Query encoding
    start_time = time.time()
    query_emb, query_emb_bin = get_bin_embedding(query, args.model)
    print(f"Query encoding took {(time.time()-start_time)*1000:.2f}ms")

    start_time = time.time()
    #Search nprobe closest centroids
    centroid_scores, centroid_ids = centroids.search(query_emb_bin, args.nprobe)
    centroid_ids = centroid_ids[0]
    print(f"Centroid search took {(time.time()-start_time)*1000:.2f}ms")

    start_time = time.time()
    all_hits = []

    #for cid in centroid_ids:
    #    global_scores.extend(search_cluster(cid, query_emb_bin))

    pool_args = []
    for cid in centroid_ids:
        cid_str = str(cid.item()).zfill(args.ivf['zfill'])
        cid_folder = cid_str[-args.ivf['folder']:]
        pool_args.append({'cid': cid_str, 'cid_folder': cid_folder, 'input_path': args.input, 'topk': args.topk, 'query_emb_bin': query_emb_bin})

    for result in pool.imap_unordered(search_cluster, pool_args, chunksize=10):
        all_hits.extend(result)
 
    #Sort global scores
    all_hits.sort(key=lambda x: x['doc_score'])
    all_hits = all_hits[0:num_rescore]

    print(f"Searching in clusters took {(time.time()-start_time)*1000:.2f}ms"); start_time = time.time()

    #Dense - Binary Rescoring
    for hit in all_hits:
        doc_emb = hit['doc_emb']
        doc_emb_bin_unpacked = np.unpackbits(doc_emb, axis=-1).astype("int")
        doc_emb_bin_unpacked = 2*doc_emb_bin_unpacked-1
        hit['cont_score'] = (query_emb @ doc_emb_bin_unpacked.T).item()

    all_hits.sort(key=lambda x: x['cont_score'], reverse=True)
    all_hits = all_hits[0:args.topk]
    print(f"Dense-Binary rescoring took {(time.time()-start_time)*1000:.2f}ms"); start_time = time.time()
    

    #Fetch documents
    results = []

    for hit in all_hits:
        with zstandard.open(os.path.join(args.input, f"text/{hit['cid'][-args.ivf['folder']:]}/{hit['cid']}.jsonl.zst"), "rt") as fIn:
            for line_idx, line in enumerate(fIn):
                if line_idx == hit['doc_idx']:
                    data = json.loads(line)
                    data['_score'] = hit['cont_score']
                    results.append(data)
                    break

    print(f"Fetch docs took {(time.time()-start_time)*1000:.2f}ms")

    for hit in results[0:3]:
        print(hit)
        print("-------------")


def main():
    parser = ArgumentParser()
    parser.add_argument("--model", default="embed-english-v3.0")
    parser.add_argument("--input", required=True, help="IVF Folder")
    parser.add_argument("--nprobe", type=int, default=100)
    parser.add_argument("--topk", type=int, default=10)
    args = parser.parse_args()

    #Load config
    with open(f"{args.input}/config.json") as fIn:
        args.ivf = json.load(fIn)
    
    
    #Restore centroid index
    with open(os.path.join(args.input, "centroid_vecs.npy"), "rb") as fIn:
        centroid_vec = np.load(fIn)
        print("Centroids shape:", centroid_vec.shape)
        centroids = faiss.IndexBinaryFlat(centroid_vec.shape[1]*8)
        centroids.add(centroid_vec)


    while True:
        query = input("Query: ")
        search(args, centroids, query)
        print("\n===========================\n")


if __name__ == "__main__":
    pool = Pool(processes=8)
    main()