[core] Multi Step Scheduling (#7000)

Co-authored-by: afeldman-nm <156691304+afeldman-nm@users.noreply.github.com>

tests/worker/test_model_input.py

@@ -10,6 +10,7 @@ from vllm.model_executor.pooling_metadata import PoolingMetadata
 from vllm.worker.embedding_model_runner import (
     ModelInputForGPUWithPoolingMetadata)
 from vllm.worker.model_runner import ModelInputForGPUWithSamplingMetadata
+from vllm.worker.multi_step_model_runner import StatefulModelInput
 
 
 class MockAttentionBackend(AttentionBackend):
@@ -154,3 +155,79 @@ def test_embedding_model_runner_input():
                        None) == getattr(attn_metadata, field.name, None)
     # Pooling metadata is not broadcast.
     assert received_model_input.pooling_metadata is None
+
+
+def test_multi_step_model_runner_input():
+    sampling_metadata = SamplingMetadata(
+        ["seq_group"],
+        "selected_token_indices",
+        "categorized_sample_indices",
+        "num_prompts",
+    )
+    attn_metadata = AttentionMetadata(
+        num_prefills=1,
+        num_prefill_tokens=2,
+        num_decode_tokens=3,
+        slot_mapping=torch.zeros(1),
+    )
+    frozen_model_input = ModelInputForGPUWithSamplingMetadata(
+        input_tokens=torch.ones(10),
+        input_positions=torch.ones(10),
+        sampling_metadata=sampling_metadata,
+        attn_metadata=attn_metadata)
+
+    model_input = StatefulModelInput(
+        frozen_model_input=frozen_model_input,
+        is_last_step=True,
+        is_first_multi_step=False,
+        current_step=4,
+        last_sampled_token_ids=torch.ones((10, 1)),
+        is_multi_step=True,
+        num_queries=8,
+        num_seqs=5,
+        cached_outputs=[],
+    )
+
+    assert isinstance(model_input, StatefulModelInput)
+
+    # Test round trip serialization.
+    tensor_dict = model_input.as_broadcastable_tensor_dict()
+    attn_backend = MockAttentionBackend()
+    received_model_input = (StatefulModelInput.from_broadcasted_tensor_dict(
+        tensor_dict, attn_backend=attn_backend))
+
+    receieved_frozen_input = received_model_input.frozen_model_input
+
+    # Check that received copy has correct values.
+    assert isinstance(received_model_input, StatefulModelInput)
+    assert receieved_frozen_input.input_tokens is not None
+    assert (receieved_frozen_input.input_tokens ==
+            frozen_model_input.input_tokens).all()
+    assert receieved_frozen_input.input_positions is not None
+    assert (receieved_frozen_input.input_positions ==
+            frozen_model_input.input_positions).all()
+    assert receieved_frozen_input.multi_modal_kwargs is None
+    assert (frozen_model_input.multi_modal_kwargs ==
+            frozen_model_input.multi_modal_kwargs)
+    assert receieved_frozen_input.lora_requests is None
+    assert (receieved_frozen_input.lora_requests ==
+            frozen_model_input.lora_requests)
+    assert receieved_frozen_input.lora_mapping is None
+    assert (
+        receieved_frozen_input.lora_mapping == frozen_model_input.lora_mapping)
+    for field in dataclasses.fields(AttentionMetadata):
+        assert getattr(receieved_frozen_input.attn_metadata, field.name,
+                       None) == getattr(attn_metadata, field.name, None)
+    # For sampling metadata, only selected_token_indices is copied.
+    assert (receieved_frozen_input.sampling_metadata.selected_token_indices ==
+            sampling_metadata.selected_token_indices)
+    assert receieved_frozen_input.sampling_metadata.seq_groups is None
+
+    # check non frozen fields
+    assert received_model_input.is_last_step == model_input.is_last_step
+    assert (received_model_input.is_first_multi_step ==
+            model_input.is_first_multi_step)
+    assert received_model_input.current_step == model_input.current_step
+    assert (received_model_input.last_sampled_token_ids ==
+            model_input.last_sampled_token_ids).all()
+    assert received_model_input.is_multi_step == model_input.is_multi_step