[Performance][Model Loader] Skip non-local expert weights during EP model loading (#37136)

Signed-off-by: esmeetu <jasonailu87@gmail.com>

tests/model_executor/model_loader/test_ep_weight_filter.py

@@ -0,0 +1,361 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""Tests for EP weight filtering during model loading."""
+
+import glob
+import tempfile
+
+import huggingface_hub.constants
+import pytest
+import torch
+
+from vllm.model_executor.model_loader.ep_weight_filter import (
+    compute_local_expert_ids,
+    parse_expert_id,
+    should_skip_weight,
+)
+from vllm.model_executor.model_loader.weight_utils import (
+    safetensors_weights_iterator,
+)
+
+# ---------------------------------------------------------------------------
+# Unit tests for parse_expert_id
+# ---------------------------------------------------------------------------
+
+
+class TestParseExpertId:
+    def test_routed_expert(self):
+        name = "model.layers.0.mlp.experts.42.gate_proj.weight"
+        assert parse_expert_id(name) == 42
+
+    def test_large_expert_id(self):
+        name = "model.layers.60.mlp.experts.383.down_proj.weight"
+        assert parse_expert_id(name) == 383
+
+    def test_shared_expert(self):
+        # Shared experts use a different naming convention in most models
+        name = "model.layers.0.mlp.shared_experts.gate_proj.weight"
+        assert parse_expert_id(name) is None
+
+    def test_attention_weight(self):
+        name = "model.layers.0.self_attn.q_proj.weight"
+        assert parse_expert_id(name) is None
+
+    def test_embedding(self):
+        name = "model.embed_tokens.weight"
+        assert parse_expert_id(name) is None
+
+    def test_layernorm(self):
+        name = "model.layers.0.input_layernorm.weight"
+        assert parse_expert_id(name) is None
+
+    def test_fused_3d_expert(self):
+        # 3D fused-expert tensors (e.g. gpt-oss) have no numeric expert id.
+        # They must NOT be filtered — slicing happens later in weight_loader.
+        name = "model.layers.0.mlp.experts.gate_proj.weight"
+        assert parse_expert_id(name) is None
+
+    def test_fused_3d_expert_down_proj(self):
+        name = "model.layers.10.mlp.experts.down_proj.weight"
+        assert parse_expert_id(name) is None
+
+    def test_expert_scale(self):
+        # NVFP4 quantized models have scale tensors for experts
+        name = "model.layers.5.mlp.experts.100.gate_proj.weight_scale"
+        assert parse_expert_id(name) == 100
+
+    def test_expert_zero_id(self):
+        name = "model.layers.0.mlp.experts.0.up_proj.weight"
+        assert parse_expert_id(name) == 0
+
+
+# ---------------------------------------------------------------------------
+# Unit tests for compute_local_expert_ids
+# ---------------------------------------------------------------------------
+
+
+class TestComputeLocalExpertIds:
+    def test_ep_disabled(self):
+        assert compute_local_expert_ids(64, ep_size=1, ep_rank=0) is None
+
+    def test_even_split(self):
+        # 64 experts, EP=8 → 8 per rank
+        ids = compute_local_expert_ids(64, ep_size=8, ep_rank=0)
+        assert ids == set(range(0, 8))
+
+        ids = compute_local_expert_ids(64, ep_size=8, ep_rank=7)
+        assert ids == set(range(56, 64))
+
+    def test_uneven_split(self):
+        # 10 experts, EP=3 → ranks get 4, 3, 3
+        ids_0 = compute_local_expert_ids(10, ep_size=3, ep_rank=0)
+        ids_1 = compute_local_expert_ids(10, ep_size=3, ep_rank=1)
+        ids_2 = compute_local_expert_ids(10, ep_size=3, ep_rank=2)
+
+        assert len(ids_0) == 4
+        assert len(ids_1) == 3
+        assert len(ids_2) == 3
+        # All experts covered, no overlap
+        assert ids_0 | ids_1 | ids_2 == set(range(10))
+        assert ids_0.isdisjoint(ids_1)
+        assert ids_1.isdisjoint(ids_2)
+
+    def test_384_experts_ep8(self):
+        # Kimi-K2.5 config: 384 experts, EP=8
+        for rank in range(8):
+            ids = compute_local_expert_ids(384, ep_size=8, ep_rank=rank)
+            assert len(ids) == 48
+
+        # All experts covered
+        all_ids = set()
+        for rank in range(8):
+            ids = compute_local_expert_ids(384, ep_size=8, ep_rank=rank)
+            all_ids |= ids
+        assert all_ids == set(range(384))
+
+    def test_384_experts_ep16(self):
+        for rank in range(16):
+            ids = compute_local_expert_ids(384, ep_size=16, ep_rank=rank)
+            assert len(ids) == 24
+
+    def test_384_experts_ep24(self):
+        # 384 / 24 = 16 exactly
+        for rank in range(24):
+            ids = compute_local_expert_ids(384, ep_size=24, ep_rank=rank)
+            assert len(ids) == 16
+
+    # round_robin placement tests
+
+    def test_round_robin_basic(self):
+        # 8 experts, EP=2: rank 0 → {0,2,4,6}, rank 1 → {1,3,5,7}
+        rr = "round_robin"
+        ids_0 = compute_local_expert_ids(8, 2, 0, placement=rr)
+        ids_1 = compute_local_expert_ids(8, 2, 1, placement=rr)
+        assert ids_0 == {0, 2, 4, 6}
+        assert ids_1 == {1, 3, 5, 7}
+
+    def test_round_robin_full_coverage(self):
+        # 384 experts, EP=8: all experts covered, no overlap
+        rr = "round_robin"
+        all_ids: set[int] = set()
+        for rank in range(8):
+            ids = compute_local_expert_ids(384, 8, rank, placement=rr)
+            assert ids is not None and len(ids) == 48
+            assert all_ids.isdisjoint(ids)
+            all_ids |= ids
+        assert all_ids == set(range(384))
+
+    def test_round_robin_uneven(self):
+        # 10 experts, EP=3: rank 0→{0,3,6,9}, rank 1→{1,4,7}, rank 2→{2,5,8}
+        rr = "round_robin"
+        ids_0 = compute_local_expert_ids(10, 3, 0, placement=rr)
+        ids_1 = compute_local_expert_ids(10, 3, 1, placement=rr)
+        ids_2 = compute_local_expert_ids(10, 3, 2, placement=rr)
+        assert ids_0 == {0, 3, 6, 9}
+        assert ids_1 == {1, 4, 7}
+        assert ids_2 == {2, 5, 8}
+        assert ids_0 | ids_1 | ids_2 == set(range(10))
+
+
+# ---------------------------------------------------------------------------
+# Unit tests for should_skip_weight
+# ---------------------------------------------------------------------------
+
+
+class TestShouldSkipWeight:
+    def setup_method(self):
+        # Simulate EP=8, rank=0 → experts 0-47
+        self.local_ids = compute_local_expert_ids(384, ep_size=8, ep_rank=0)
+
+    def test_no_filter(self):
+        assert not should_skip_weight("anything", None)
+
+    def test_dense_not_skipped(self):
+        assert not should_skip_weight(
+            "model.layers.0.self_attn.q_proj.weight", self.local_ids
+        )
+
+    def test_local_expert_not_skipped(self):
+        assert not should_skip_weight(
+            "model.layers.0.mlp.experts.10.gate_proj.weight", self.local_ids
+        )
+
+    def test_remote_expert_skipped(self):
+        assert should_skip_weight(
+            "model.layers.0.mlp.experts.200.gate_proj.weight", self.local_ids
+        )
+
+    def test_boundary_expert(self):
+        # Expert 47 is local (last one), 48 is not
+        assert not should_skip_weight(
+            "model.layers.0.mlp.experts.47.gate_proj.weight", self.local_ids
+        )
+        assert should_skip_weight(
+            "model.layers.0.mlp.experts.48.gate_proj.weight", self.local_ids
+        )
+
+    def test_shared_expert_not_skipped(self):
+        assert not should_skip_weight(
+            "model.layers.0.mlp.shared_experts.gate_proj.weight", self.local_ids
+        )
+
+    def test_embedding_not_skipped(self):
+        assert not should_skip_weight("model.embed_tokens.weight", self.local_ids)
+
+    def test_fused_3d_expert_not_skipped(self):
+        # 3D fused-expert tensors (gpt-oss style) have no numeric id.
+        # Must not be skipped — weight_loader handles slicing later.
+        assert not should_skip_weight(
+            "model.layers.0.mlp.experts.gate_proj.weight", self.local_ids
+        )
+
+
+# ---------------------------------------------------------------------------
+# Integration test: safetensors_weights_iterator with EP filtering
+# ---------------------------------------------------------------------------
+
+
+class TestSafetensorsWeightsIteratorWithEpFilter:
+    """Verify that EP filtering produces a strict subset of unfiltered loading
+    and that all expected dense + local expert weights are present."""
+
+    @pytest.fixture(scope="class")
+    def gpt2_files(self):
+        """Download GPT-2 safetensors to a temp dir (shared across class)."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            huggingface_hub.constants.HF_HUB_OFFLINE = False
+            from vllm.model_executor.model_loader.weight_utils import (
+                download_weights_from_hf,
+            )
+
+            download_weights_from_hf(
+                "openai-community/gpt2",
+                allow_patterns=["*.safetensors"],
+                cache_dir=tmpdir,
+            )
+            files = glob.glob(f"{tmpdir}/**/*.safetensors", recursive=True)
+            assert len(files) > 0
+            yield files
+
+    def test_no_filter_returns_all(self, gpt2_files):
+        """With local_expert_ids=None, all weights are returned (no MoE)."""
+        all_weights = dict(safetensors_weights_iterator(gpt2_files, False))
+        filtered_weights = dict(
+            safetensors_weights_iterator(gpt2_files, False, local_expert_ids=None)
+        )
+        assert set(all_weights.keys()) == set(filtered_weights.keys())
+
+    def test_empty_filter_skips_experts_only(self, gpt2_files):
+        """GPT-2 has no expert weights, so even an empty local_expert_ids
+        set should return all weights (all are dense)."""
+        all_weights = dict(safetensors_weights_iterator(gpt2_files, False))
+        filtered_weights = dict(
+            safetensors_weights_iterator(gpt2_files, False, local_expert_ids=set())
+        )
+        # GPT-2 has no experts, so nothing should be filtered
+        assert set(all_weights.keys()) == set(filtered_weights.keys())
+
+
+class TestEpFilterOnSyntheticMoeWeights:
+    """Create synthetic safetensors files with expert-like naming and verify
+    that the filter correctly skips non-local experts."""
+
+    @pytest.fixture
+    def synthetic_moe_files(self, tmp_path):
+        """Create synthetic safetensors with expert-patterned tensor names."""
+        from safetensors.torch import save_file
+
+        tensors = {}
+        # Dense weights
+        tensors["model.embed_tokens.weight"] = torch.randn(100, 64)
+        tensors["model.layers.0.self_attn.q_proj.weight"] = torch.randn(64, 64)
+        tensors["model.layers.0.input_layernorm.weight"] = torch.randn(64)
+        # Expert weights: 8 experts
+        for expert_id in range(8):
+            tensors[f"model.layers.0.mlp.experts.{expert_id}.gate_proj.weight"] = (
+                torch.randn(128, 64)
+            )
+            tensors[f"model.layers.0.mlp.experts.{expert_id}.up_proj.weight"] = (
+                torch.randn(128, 64)
+            )
+            tensors[f"model.layers.0.mlp.experts.{expert_id}.down_proj.weight"] = (
+                torch.randn(64, 128)
+            )
+        # Shared expert (should never be filtered)
+        tensors["model.layers.0.mlp.shared_experts.gate_proj.weight"] = torch.randn(
+            128, 64
+        )
+
+        filepath = str(tmp_path / "model-00001-of-00001.safetensors")
+        save_file(tensors, filepath)
+        return [filepath], tensors
+
+    def test_no_filter_returns_all(self, synthetic_moe_files):
+        files, expected = synthetic_moe_files
+        loaded = dict(safetensors_weights_iterator(files, False))
+        assert set(loaded.keys()) == set(expected.keys())
+
+    def test_ep2_rank0_gets_half_experts(self, synthetic_moe_files):
+        files, expected = synthetic_moe_files
+        # EP=2, rank=0 → experts 0-3
+        local_ids = compute_local_expert_ids(8, ep_size=2, ep_rank=0)
+        loaded = dict(
+            safetensors_weights_iterator(files, False, local_expert_ids=local_ids)
+        )
+
+        # Should have all dense + shared + experts 0-3 only
+        for name in loaded:
+            eid = parse_expert_id(name)
+            if eid is not None:
+                assert eid in local_ids, f"Non-local expert {eid} was loaded"
+
+        # Check expert count: 4 experts × 3 weights = 12
+        expert_names = [n for n in loaded if parse_expert_id(n) is not None]
+        assert len(expert_names) == 4 * 3
+
+        # Check all dense weights present
+        assert "model.embed_tokens.weight" in loaded
+        assert "model.layers.0.self_attn.q_proj.weight" in loaded
+        assert "model.layers.0.input_layernorm.weight" in loaded
+        assert "model.layers.0.mlp.shared_experts.gate_proj.weight" in loaded
+
+    def test_ep2_rank1_gets_other_half(self, synthetic_moe_files):
+        files, expected = synthetic_moe_files
+        local_ids = compute_local_expert_ids(8, ep_size=2, ep_rank=1)
+        loaded = dict(
+            safetensors_weights_iterator(files, False, local_expert_ids=local_ids)
+        )
+
+        expert_names = [n for n in loaded if parse_expert_id(n) is not None]
+        assert len(expert_names) == 4 * 3
+        for name in expert_names:
+            assert parse_expert_id(name) in local_ids
+
+    def test_ep8_each_rank_gets_one_expert(self, synthetic_moe_files):
+        files, _ = synthetic_moe_files
+        all_expert_names = set()
+        for rank in range(8):
+            local_ids = compute_local_expert_ids(8, ep_size=8, ep_rank=rank)
+            loaded = dict(
+                safetensors_weights_iterator(files, False, local_expert_ids=local_ids)
+            )
+            expert_names = {n for n in loaded if parse_expert_id(n) is not None}
+            # 1 expert × 3 weights
+            assert len(expert_names) == 3
+            all_expert_names |= expert_names
+
+        # All 8 experts × 3 weights covered across ranks
+        assert len(all_expert_names) == 24
+
+    def test_tensor_values_match(self, synthetic_moe_files):
+        """Filtered tensors have identical values to unfiltered ones."""
+        files, _ = synthetic_moe_files
+        all_weights = dict(safetensors_weights_iterator(files, False))
+
+        local_ids = compute_local_expert_ids(8, ep_size=2, ep_rank=0)
+        filtered = dict(
+            safetensors_weights_iterator(files, False, local_expert_ids=local_ids)
+        )
+
+        for name, tensor in filtered.items():
+            assert torch.equal(tensor, all_weights[name]), f"Tensor mismatch for {name}"