retrieval : fix memory leak in retrieval query handling (#8955)

* retrieval

* Reuse querybatch to reduce frequent memory allocation

* delete unused white space

examples/retrieval/retrieval.cpp

@@ -253,14 +253,15 @@ int main(int argc, char ** argv) {
         chunks[i].tokens.clear();
     }
 
+    struct llama_batch query_batch = llama_batch_init(n_batch, 0, 1);
+
     // start loop, receive query and return top k similar chunks based on cosine similarity
     std::string query;
     while (true) {
         printf("Enter query: ");
         std::getline(std::cin, query);
         std::vector<int32_t> query_tokens = llama_tokenize(ctx, query, true);
 
-        struct llama_batch query_batch = llama_batch_init(n_batch, 0, 1);
         batch_add_seq(query_batch, query_tokens, 0);
 
         std::vector<float> query_emb(n_embd, 0);
@@ -293,6 +294,7 @@ int main(int argc, char ** argv) {
     }
 
     // clean up
+    llama_batch_free(query_batch);
     llama_print_timings(ctx);
     llama_free(ctx);
     llama_free_model(model);