[Core] Composable parallel: Phase 1 strategy overlay (TP/DP/stage-replica) (RFC #4084) (#4281)

Signed-off-by: Kushan A. <kahmadian@nvidia.com>
Signed-off-by: kushanam <kushanam@users.noreply.github.com>
Signed-off-by: Kushan A <kahmadian@nvidia.com>
Signed-off-by: kahmadian <kahmadian@users.noreply.github.com>
Co-authored-by: kushanam <kushanam@users.noreply.github.com>
Co-authored-by: kahmadian <kahmadian@users.noreply.github.com>

tests/config/composable_parallel/test_strategy_loader.py

@@ -0,0 +1,97 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""Tests for parsing/loading strategy files."""
+
+from __future__ import annotations
+
+import pytest
+
+from vllm_omni.config.composable_parallel.routing import Broadcast, RouteByStage
+from vllm_omni.config.composable_parallel.strategy_loader import (
+    StrategyLoadError,
+    load_strategy_specs,
+    parse_strategy_specs,
+)
+
+pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
+
+
+def test_parse_basic():
+    data = {
+        "strategies": {
+            "thinker": [{"axis": "tp", "size": 2}],
+            "talker": [{"axis": "stage_replica", "size": 2, "routing": "round_robin"}],
+        }
+    }
+    specs = parse_strategy_specs(data)
+    assert set(specs) == {"thinker", "talker"}
+
+    (tp_spec,) = specs["thinker"]
+    assert tp_spec.mesh_axis.kind == "tp"
+    assert tp_spec.mesh_axis.size == 2
+    assert isinstance(tp_spec.routing, Broadcast)
+
+    (sr_spec,) = specs["talker"]
+    assert sr_spec.mesh_axis.kind == "stage_replica"
+    assert isinstance(sr_spec.routing, RouteByStage)
+    assert sr_spec.routing.routing_policy == "round_robin"
+
+
+def test_parse_without_strategies_key():
+    # A bare role mapping (no top-level "strategies") is also accepted.
+    specs = parse_strategy_specs({"thinker": [{"axis": "tp", "size": 4}]})
+    assert specs["thinker"][0].mesh_axis.size == 4
+
+
+def test_l1_owner_goes_to_shard_extension():
+    specs = parse_strategy_specs({"talker": [{"axis": "stage_replica", "size": 2, "l1_owner": "delegated"}]})
+    assert specs["talker"][0].shard_extension["l1_owner"] == "delegated"
+
+
+def test_missing_axis_raises():
+    with pytest.raises(StrategyLoadError):
+        parse_strategy_specs({"thinker": [{"size": 2}]})
+
+
+def test_missing_size_raises():
+    with pytest.raises(StrategyLoadError):
+        parse_strategy_specs({"thinker": [{"axis": "tp"}]})
+
+
+def test_routing_on_non_policy_axis_raises():
+    with pytest.raises(StrategyLoadError):
+        parse_strategy_specs({"thinker": [{"axis": "tp", "size": 2, "routing": "random"}]})
+
+
+def test_bad_size_raises():
+    with pytest.raises(StrategyLoadError):
+        parse_strategy_specs({"thinker": [{"axis": "tp", "size": "two"}]})
+
+
+def test_entries_must_be_list():
+    with pytest.raises(StrategyLoadError):
+        parse_strategy_specs({"thinker": {"axis": "tp", "size": 2}})
+
+
+def test_non_mapping_entry_raises():
+    # A list whose elements are not mappings (e.g. a bare string) must raise a
+    # StrategyLoadError, not an opaque TypeError from dict(entry).
+    with pytest.raises(StrategyLoadError):
+        parse_strategy_specs({"thinker": ["tp"]})
+
+
+def test_load_from_file(tmp_path):
+    path = tmp_path / "strategy.yaml"
+    path.write_text(
+        "strategies:\n"
+        "  thinker:\n"
+        "    - axis: tp\n"
+        "      size: 2\n"
+        "  talker:\n"
+        "    - axis: stage_replica\n"
+        "      size: 2\n"
+        "      routing: least_queue\n"
+    )
+    specs = load_strategy_specs(str(path))
+    assert specs["thinker"][0].mesh_axis.size == 2
+    assert specs["talker"][0].routing.routing_policy == "least_queue"