feat: Add FlexAttention Backend for Efficient Sparse Attention (#9947)

Co-authored-by: Baizhou Zhang <sobereddiezhang@gmail.com>

test/srt/test_torch_flex_attention_backend.py

@@ -0,0 +1,49 @@
+"""
+Usage:
+python3 -m unittest test_torch_flex_attention_backend.TestTorchFlexAttnBackend.test_gsm8k
+"""
+
+import unittest
+from types import SimpleNamespace
+
+from sglang.srt.utils import kill_process_tree
+from sglang.test.few_shot_gsm8k import run_eval as run_eval_few_shot_gsm8k
+from sglang.test.test_utils import (
+    DEFAULT_MODEL_NAME_FOR_TEST,
+    DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
+    DEFAULT_URL_FOR_TEST,
+    CustomTestCase,
+    popen_launch_server,
+)
+
+
+class TestTorchFlexAttnBackend(CustomTestCase):
+    def test_gsm8k(self):
+        model = DEFAULT_MODEL_NAME_FOR_TEST
+        base_url = DEFAULT_URL_FOR_TEST
+        process = popen_launch_server(
+            model,
+            base_url,
+            timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
+            other_args=["--attention-backend", "flex_attention"],
+        )
+
+        try:
+            args = SimpleNamespace(
+                num_shots=8,
+                data_path=None,
+                num_questions=100,
+                parallel=10,
+                max_new_tokens=512,
+                host="http://127.0.0.1",
+                port=int(base_url.split(":")[-1]),
+            )
+            metrics = run_eval_few_shot_gsm8k(args)
+            print(f"{metrics=}")
+            self.assertGreater(metrics["accuracy"], 0.62)
+        finally:
+            kill_process_tree(process.pid)
+
+
+if __name__ == "__main__":
+    unittest.main()