update hybrid for mrtydi (#739)

pyserini/hsearch/__main__.py

@@ -38,7 +38,9 @@
 def define_fusion_args(parser):
     parser.add_argument('--alpha', type=float, metavar='num', required=False, default=0.1,
                         help="alpha for hybrid search")
+    parser.add_argument('--hits', type=int, required=False, default=10, help='number of hits from dense and sparse')
     parser.add_argument('--normalization', action='store_true', required=False, help='hybrid score with normalization')
+    parser.add_argument('--weight-on-dense', action='store_true', required=False, help='weight on dense part')
 
 
 def parse_args(parser, commands):
@@ -160,16 +162,16 @@ def parse_args(parser, commands):
         batch_topic_ids = list()
         for index, (topic_id, text) in enumerate(tqdm(query_iterator, total=len(topics.keys()))):
             if args.run.batch_size <= 1 and args.run.threads <= 1:
-                hits = hsearcher.search(text, args.run.hits, args.fusion.alpha, args.fusion.normalization)
+                hits = hsearcher.search(text, args.fusion.hits, args.run.hits, args.fusion.alpha, args.fusion.normalization, args.fusion.weight_on_dense)
                 results = [(topic_id, hits)]
             else:
                 batch_topic_ids.append(str(topic_id))
                 batch_topics.append(text)
                 if (index + 1) % args.run.batch_size == 0 or \
                         index == len(topics.keys()) - 1:
                     results = hsearcher.batch_search(
-                        batch_topics, batch_topic_ids, args.run.hits, args.run.threads,
-                        args.fusion.alpha, args.fusion.normalization)
+                        batch_topics, batch_topic_ids, args.fusion.hits, args.run.hits, args.run.threads,
+                        args.fusion.alpha, args.fusion.normalization, args.fusion.weight_on_dense)
                     results = [(id_, results[id_]) for id_ in batch_topic_ids]
                     batch_topic_ids.clear()
                     batch_topics.clear()

pyserini/hsearch/_hybrid.py

@@ -36,24 +36,24 @@ def __init__(self, dense_searcher, sparse_searcher):
         self.dense_searcher = dense_searcher
         self.sparse_searcher = sparse_searcher
 
-    def search(self, query: str, k: int = 10, alpha: float = 0.1, normalization: bool = False) -> List[DenseSearchResult]:
-        dense_hits = self.dense_searcher.search(query, k)
-        sparse_hits = self.sparse_searcher.search(query, k)
-        return self._hybrid_results(dense_hits, sparse_hits, alpha, k, normalization)
+    def search(self, query: str, k0: int = 10, k: int = 10, alpha: float = 0.1, normalization: bool = False, weight_on_dense: bool = False) -> List[DenseSearchResult]:
+        dense_hits = self.dense_searcher.search(query, k0)
+        sparse_hits = self.sparse_searcher.search(query, k0)
+        return self._hybrid_results(dense_hits, sparse_hits, alpha, k, normalization, weight_on_dense)
 
-    def batch_search(self, queries: List[str], q_ids: List[str], k: int = 10, threads: int = 1,
-                     alpha: float = 0.1, normalization: bool = False) \
+    def batch_search(self, queries: List[str], q_ids: List[str], k0: int = 10, k: int = 10, threads: int = 1,
+            alpha: float = 0.1, normalization: bool = False, weight_on_dense: bool = False) \
             -> Dict[str, List[DenseSearchResult]]:
-        dense_result = self.dense_searcher.batch_search(queries, q_ids, k, threads)
-        sparse_result = self.sparse_searcher.batch_search(queries, q_ids, k, threads)
+        dense_result = self.dense_searcher.batch_search(queries, q_ids, k0, threads)
+        sparse_result = self.sparse_searcher.batch_search(queries, q_ids, k0, threads)
         hybrid_result = {
-            key: self._hybrid_results(dense_result[key], sparse_result[key], alpha, k, normalization)
+            key: self._hybrid_results(dense_result[key], sparse_result[key], alpha, k, normalization, weight_on_dense)
             for key in dense_result
         }
         return hybrid_result
 
     @staticmethod
-    def _hybrid_results(dense_results, sparse_results, alpha, k, normalization=False):
+    def _hybrid_results(dense_results, sparse_results, alpha, k, normalization=False, weight_on_dense=False):
         dense_hits = {hit.docid: hit.score for hit in dense_results}
         sparse_hits = {hit.docid: hit.score for hit in sparse_results}
         hybrid_result = []
@@ -76,6 +76,6 @@ def _hybrid_results(dense_results, sparse_results, alpha, k, normalization=False
                                / (max_sparse_score - min_sparse_score)
                 dense_score = (dense_score - (min_dense_score + max_dense_score) / 2) \
                               / (max_dense_score - min_dense_score)
-            score = alpha * sparse_score + dense_score
+            score = alpha * sparse_score + dense_score if not weight_on_dense else sparse_score + alpha * dense_score
             hybrid_result.append(DenseSearchResult(doc, score))
         return sorted(hybrid_result, key=lambda x: x.score, reverse=True)[:k]

pyserini/search/_impact_searcher.py

@@ -23,7 +23,6 @@
 from typing import Dict, List, Optional, Union
 import numpy as np
 from ._base import Document
-from pyserini.index import IndexReader
 from pyserini.pyclass import autoclass, JFloat, JArrayList, JHashMap, JString
 from pyserini.util import download_prebuilt_index
 from pyserini.encode import QueryEncoder, TokFreqQueryEncoder, UniCoilQueryEncoder, CachedDataQueryEncoder
@@ -230,6 +229,7 @@ def _init_query_encoder_from_str(query_encoder):
 
     @staticmethod
     def _compute_idf(index_path):
+        from pyserini.index import IndexReader
         index_reader = IndexReader(index_path)
         tokens = []
         dfs = []