Add benchmark: CFG rejection sampling + CFG no rejection sampling

benchmarks/bench_cfg_guide.py

@@ -38,23 +38,31 @@ def setup(self, grammar_name):
         )
 
     @staticmethod
-    def _run_random_cfg(guide):
+    def _run_random_cfg(guide, rejection_sampling=True):
         state = guide.initial_state
         token_ids = list(guide.tokenizer.vocabulary.values())
         for i in range(40):
             # simulate ordering of logits top prob to lowest prob
             random.shuffle(token_ids)
             # simulate sampling and state update
-            next_token_id = next(guide.iter_valid_token_ids(state, token_ids))
-            state = guide.get_next_state(state, next_token_id)
+            if rejection_sampling:
+                next_token_id = next(guide.iter_valid_token_ids(state, token_ids))
+                state = guide.get_next_state(state, next_token_id)
+            else:
+                next_token_id = random.choice(guide.get_next_instruction(state).tokens)
+                state = guide.get_next_state(state, next_token_id)
 
     @cache_disabled()
     def time_cfg_guide_setup(self, grammar_name):
         CFGGuide(benched_grammars[grammar_name], self.tokenizer)
 
+    @cache_disabled()
+    def time_cfg_guide_run_rejection_sampling(self, grammar):
+        self._run_random_cfg(self.prebuilt_cfg_guide, rejection_sampling=True)
+
     @cache_disabled()
     def time_cfg_guide_run(self, grammar):
-        self._run_random_cfg(self.prebuilt_cfg_guide)
+        self._run_random_cfg(self.prebuilt_cfg_guide, rejection_sampling=False)
 
     @cache_disabled()
     def peakmem_cfg_guide_run(self, grammar):