1 files changed, 30 insertions, 0 deletions
diff --git a/rag/retriever/rerank/local.py b/rag/retriever/rerank/local.py
new file mode 100644
index 0000000..758c5dc
--- /dev/null
+++ b/rag/retriever/rerank/local.py
@@ -0,0 +1,30 @@
+import os
+
+from loguru import logger as log
+from sentence_transformers import CrossEncoder
+
+from rag.generator.prompt import Prompt
+from rag.retriever.rerank.abstract import AbstractReranker
+
+
+class Reranker(metaclass=AbstractReranker):
+    def __init__(self) -> None:
+        self.model = CrossEncoder(os.environ["RERANK_MODEL"])
+        self.top_k = int(os.environ["RERANK_TOP_K"])
+
+    def rank(self, prompt: Prompt) -> Prompt:
+        if prompt.documents:
+            results = self.model.rank(
+                query=prompt.query,
+                documents=[d.text for d in prompt.documents],
+                return_documents=False,
+                top_k=self.top_k,
+            )
+            ranking = list(filter(lambda x: x.get("score", 0.0) > 0.5, results))
+            log.debug(
+                f"Reranking gave {len(ranking)} relevant documents of {len(prompt.documents)}"
+            )
+            prompt.documents = [
+                prompt.documents[r.get("corpus_id", 0)] for r in ranking
+            ]
+        return prompt