Support speculative decoding on CPU (#27862)

Co-authored-by: Valentine233 <xuan.liao@intel.com>

test/registered/cpu/test_spec_eagle_cpu.py

@@ -0,0 +1,65 @@
+"""EAGLE spec-decoding core on CPU: the standard config (topk=1, page_size=1)
+on the synchronous (non-overlap) path. topk > 1 tree drafting is covered in
+test_spec_eagle_topk_cpu.py (split to stay under the per-file CI timeout).
+"""
+
+import unittest
+
+from sglang.srt.environ import envs
+from sglang.test.ci.ci_register import register_cpu_ci
+from sglang.test.kits.matched_stop_kit import MatchedStopMixin
+from sglang.test.kits.spec_server_kits import (
+    SpecAccuracyKit,
+    SpecCorrectnessKit,
+    SpecFeatureKit,
+    SpecLogprobKit,
+    SpecPenaltyKit,
+)
+from sglang.test.server_fixtures.spec_eagle_fixture import EagleLlama2Base
+
+# Measured 780s all-green on a 40-core GNR socket (1 launch + 18 methods).
+register_cpu_ci(est_time=800, suite="base-b-test-cpu")
+
+_KITS = (
+    SpecCorrectnessKit,
+    SpecAccuracyKit,
+    SpecLogprobKit,
+    SpecPenaltyKit,
+    SpecFeatureKit,
+    MatchedStopMixin,
+)
+
+
+class _Core(EagleLlama2Base):
+    """EAGLE (Llama-2) preset on CPU."""
+
+    attention_backend = "intel_amx"
+    disable_overlap = True
+    mem_fraction_static = 0.3
+    gsm8k_num_examples = 64
+    env_overrides = ((envs.SGLANG_ENABLE_STRICT_MEM_CHECK_DURING_BUSY, 1),)
+
+
+class TestEagleLlama2NoOverlap(_Core, *_KITS):
+    """Spec v1 (overlap scheduler off) -- the only mode reachable on CPU."""
+
+    # Standard chain config (topk=1, page_size=1), same shape as the CUDA core.
+    spec_steps = 5
+    spec_topk = 1
+    spec_tokens = 6
+    # EAGLE/Llama-2 topk=1 accepts modestly; tune against CI if needed.
+    acc_length_thres = 1.6
+    batch_accept_len_thres = 1.3
+    gsm8k_accept_len_thres = 1.3
+
+    @unittest.skip(
+        "constrained decoding on CPU needs a vocab-mask CPU branch in the "
+        "xgrammar backend (upstream gap, not spec-specific); the other grammar "
+        "backends lack the rollback spec verification requires"
+    )
+    def test_constrained_decoding(self):
+        pass
+
+
+if __name__ == "__main__":
+    unittest.main()

test/registered/cpu/test_spec_eagle_parity_cpu.py

@@ -0,0 +1,23 @@
+import unittest
+
+from sglang.srt.environ import envs
+from sglang.test.ci.ci_register import register_cpu_ci
+from sglang.test.kits.spec_server_kits import SpecParityKit
+from sglang.test.server_fixtures.spec_eagle_fixture import Eagle3Base
+
+# Estimated: 2 sequential 8B server launches + one 4-prompt greedy method
+# (CUDA sibling: 360); tune from CI TIMINGS once it has run there.
+register_cpu_ci(est_time=480, suite="base-b-test-cpu")
+
+
+class TestEagle3ParityCPU(SpecParityKit, Eagle3Base):
+    """EAGLE3 spec (intel_amx) greedy output == non-spec reference."""
+
+    attention_backend = "intel_amx"
+    disable_overlap = True
+    mem_fraction_static = 0.3
+    env_overrides = ((envs.SGLANG_ENABLE_STRICT_MEM_CHECK_DURING_BUSY, 1),)
+
+
+if __name__ == "__main__":
+    unittest.main()

test/registered/cpu/test_spec_eagle_topk_cpu.py

@@ -0,0 +1,62 @@
+"""EAGLE topk > 1 tree drafting on CPU (Llama-2 topk=4, synchronous path).
+
+Split from test_spec_eagle_cpu.py, mirroring the CUDA test_spec_eagle.py /
+test_spec_eagle_topk.py layout, so each file stays under the per-file CI
+timeout.
+"""
+
+import unittest
+
+from sglang.srt.environ import envs
+from sglang.test.ci.ci_register import register_cpu_ci
+from sglang.test.kits.spec_server_kits import (
+    SpecAccuracyKit,
+    SpecCorrectnessKit,
+    SpecFeatureKit,
+    SpecLogprobKit,
+    SpecPenaltyKit,
+)
+from sglang.test.server_fixtures.spec_eagle_fixture import EagleLlama2Base
+
+# Measured 830s all-green on a 40-core GNR socket (1 launch + 14 methods).
+register_cpu_ci(est_time=850, suite="base-b-test-cpu")
+
+
+class _Core(EagleLlama2Base):
+    """EAGLE (Llama-2) preset on CPU."""
+
+    attention_backend = "intel_amx"
+    disable_overlap = True
+    mem_fraction_static = 0.3
+    gsm8k_num_examples = 64
+    env_overrides = ((envs.SGLANG_ENABLE_STRICT_MEM_CHECK_DURING_BUSY, 1),)
+
+
+class TestEagleLlama2Topk4(
+    _Core,
+    SpecCorrectnessKit,
+    SpecAccuracyKit,
+    SpecLogprobKit,
+    SpecPenaltyKit,
+    SpecFeatureKit,
+):
+    """EAGLE/Llama-2 topk=4 tree coverage (kits listed in bases)."""
+
+    spec_steps = 3
+    spec_topk = 4
+    spec_tokens = 8
+    acc_length_thres = 2.4
+    batch_accept_len_thres = 1.6
+    gsm8k_accept_len_thres = 2.0
+
+    @unittest.skip(
+        "constrained decoding on CPU needs a vocab-mask CPU branch in the "
+        "xgrammar backend (upstream gap, not spec-specific); the other grammar "
+        "backends lack the rollback spec verification requires"
+    )
+    def test_constrained_decoding(self):
+        pass
+
+
+if __name__ == "__main__":
+    unittest.main()