Generate: Add new decoding strategy "DoLa" in .generate() (#29619)

Co-authored-by: Joao Gante <joao@huggingface.co>

tests/models/llama/test_modeling_llama.py

@@ -703,6 +703,29 @@ class LlamaIntegrationTest(unittest.TestCase):
             )
         )
 
+    @slow
+    def test_model_7b_dola_generation(self):
+        # ground truth text generated with dola_layers="low", repetition_penalty=1.2
+        EXPECTED_TEXT_COMPLETION = (
+            "Simply put, the theory of relativity states that 1) time and space are relative, and 2) the laws of "
+            "physics are the same for all observers in uniform motion relative to one another.\n\nThe theory of "
+            "relativity was developed by Albert Einstein in the early 20th century, and it revolutionized our "
+            "understanding of space and time."
+        )
+        prompt = "Simply put, the theory of relativity states that "
+        tokenizer = LlamaTokenizer.from_pretrained("meta-llama/Llama-2-7b-chat-hf")
+        model = LlamaForCausalLM.from_pretrained(
+            "meta-llama/Llama-2-7b-chat-hf", device_map="sequential", torch_dtype=torch.float16
+        )
+        model_inputs = tokenizer(prompt, return_tensors="pt").to(model.device)
+
+        # greedy generation outputs
+        generated_ids = model.generate(
+            **model_inputs, max_new_tokens=64, top_p=None, temperature=1, do_sample=False, dola_layers="low"
+        )
+        text = tokenizer.decode(generated_ids[0], skip_special_tokens=True)
+        self.assertEqual(EXPECTED_TEXT_COMPLETION, text)
+
     @slow
     @require_torch_gpu
     @require_read_token