Cache the result from llm for graphrag and raptor (#4051)

### What problem does this PR solve?

#4045

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

rag/raptor.py

@@ -21,6 +21,7 @@ import umap
 import numpy as np
 from sklearn.mixture import GaussianMixture
 
+from graphrag.utils import get_llm_cache, get_embed_cache, set_embed_cache, set_llm_cache
 from rag.utils import truncate
 
 
@@ -33,6 +34,27 @@ class RecursiveAbstractiveProcessing4TreeOrganizedRetrieval:
         self._prompt = prompt
         self._max_token = max_token
 
+    def _chat(self, system, history, gen_conf):
+        response = get_llm_cache(self._llm_model.llm_name, system, history, gen_conf)
+        if response:
+            return response
+        response = self._llm_model.chat(system, history, gen_conf)
+        if response.find("**ERROR**") >= 0:
+            raise Exception(response)
+        set_llm_cache(self._llm_model.llm_name, system, response, history, gen_conf)
+        return response
+
+    def _embedding_encode(self, txt):
+        response = get_embed_cache(self._embd_model.llm_name, txt)
+        if response:
+            return response
+        embds, _ = self._embd_model.encode([txt])
+        if len(embds) < 1 or len(embds[0]) < 1:
+            raise Exception("Embedding error: ")
+        embds = embds[0]
+        set_embed_cache(self._embd_model.llm_name, txt, embds)
+        return embds
+
     def _get_optimal_clusters(self, embeddings: np.ndarray, random_state: int):
         max_clusters = min(self._max_cluster, len(embeddings))
         n_clusters = np.arange(1, max_clusters)
@@ -57,7 +79,7 @@ class RecursiveAbstractiveProcessing4TreeOrganizedRetrieval:
                 texts = [chunks[i][0] for i in ck_idx]
                 len_per_chunk = int((self._llm_model.max_length - self._max_token) / len(texts))
                 cluster_content = "\n".join([truncate(t, max(1, len_per_chunk)) for t in texts])
-                cnt = self._llm_model.chat("You're a helpful assistant.",
+                cnt = self._chat("You're a helpful assistant.",
                                            [{"role": "user",
                                              "content": self._prompt.format(cluster_content=cluster_content)}],
                                            {"temperature": 0.3, "max_tokens": self._max_token}
@@ -67,9 +89,7 @@ class RecursiveAbstractiveProcessing4TreeOrganizedRetrieval:
                 logging.debug(f"SUM: {cnt}")
                 embds, _ = self._embd_model.encode([cnt])
                 with lock:
-                    if not len(embds[0]):
-                        return
-                    chunks.append((cnt, embds[0]))
+                    chunks.append((cnt, self._embedding_encode(cnt)))
             except Exception as e:
                 logging.exception("summarize got exception")
                 return e