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sglang/test/registered/cuda_graph/test_breakable_cuda_graph.py
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2026-04-11 00:36:56 -07:00

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9.5 KiB
Python

"""Unit tests for the breakable CUDA graph mechanism.
Tests the core capture/replay logic with simple tensor operations,
verifying that graph breaks work correctly and outputs are properly
propagated across segments.
"""
import unittest
import torch
from sglang.test.ci.ci_register import register_cuda_ci
from sglang.test.test_utils import CustomTestCase
# CI Registration
register_cuda_ci(est_time=30, suite="stage-b-test-1-gpu-small")
def _skip_if_no_cuda(test_func):
return unittest.skipUnless(torch.cuda.is_available(), "CUDA not available")(
test_func
)
def _skip_if_no_cuda_bindings(test_func):
try:
from cuda.bindings import runtime as rt # noqa: F401
return test_func
except ImportError:
return unittest.skip("cuda-python not installed")(test_func)
class TestBreakableCUDAGraphBasic(CustomTestCase):
"""Test basic breakable CUDA graph capture and replay."""
@classmethod
def setUpClass(cls):
if not torch.cuda.is_available():
raise unittest.SkipTest("CUDA not available")
try:
from cuda.bindings import runtime # noqa: F401
except ImportError:
raise unittest.SkipTest("cuda-python not installed")
from sglang.srt.model_executor.breakable_cuda_graph.breakable_cuda_graph import (
BreakableCUDAGraph,
BreakableCUDAGraphCapture,
eager_on_graph,
)
cls.BreakableCUDAGraph = BreakableCUDAGraph
cls.BreakableCUDAGraphCapture = BreakableCUDAGraphCapture
cls.eager_on_graph = staticmethod(eager_on_graph)
cls.device = torch.device("cuda:0")
def test_no_break_capture_replay(self):
"""Capture and replay without any graph breaks should work like normal CUDA graph."""
x = torch.zeros(4, device=self.device)
y = torch.zeros(4, device=self.device)
graph = self.BreakableCUDAGraph()
stream = torch.cuda.Stream(self.device)
with self.BreakableCUDAGraphCapture(graph, stream=stream):
y.copy_(x + 1.0)
# Replay with new input
x.fill_(5.0)
graph.replay()
torch.cuda.synchronize()
self.assertTrue(torch.allclose(y, torch.full((4,), 6.0, device=self.device)))
def test_single_break(self):
"""A single graph break should split capture into two segments."""
x = torch.zeros(4, device=self.device)
intermediate = torch.zeros(4, device=self.device)
y = torch.zeros(4, device=self.device)
@self.eager_on_graph(enable=True)
def eager_op(src):
return src * 2.0
graph = self.BreakableCUDAGraph()
stream = torch.cuda.Stream(self.device)
with self.BreakableCUDAGraphCapture(graph, stream=stream):
intermediate.copy_(x + 1.0)
broken = eager_op(intermediate)
y.copy_(broken + 3.0)
# Replay with new input
x.fill_(10.0)
graph.replay()
torch.cuda.synchronize()
# x=10 -> intermediate=11 -> eager: 11*2=22 -> y=22+3=25
self.assertTrue(torch.allclose(y, torch.full((4,), 25.0, device=self.device)))
def test_multiple_breaks(self):
"""Multiple graph breaks should produce correct chained results."""
x = torch.zeros(4, device=self.device)
y = torch.zeros(4, device=self.device)
@self.eager_on_graph(enable=True)
def add_one(src):
return src + 1.0
@self.eager_on_graph(enable=True)
def double(src):
return src * 2.0
graph = self.BreakableCUDAGraph()
stream = torch.cuda.Stream(self.device)
with self.BreakableCUDAGraphCapture(graph, stream=stream):
t1 = x + 1.0 # graph segment 1
t2 = add_one(t1) # break 1: eager
t3 = t2 + 1.0 # graph segment 2
t4 = double(t3) # break 2: eager
y.copy_(t4) # graph segment 3
# Replay: x=5 -> +1=6 -> add_one=7 -> +1=8 -> double=16
x.fill_(5.0)
graph.replay()
torch.cuda.synchronize()
self.assertTrue(torch.allclose(y, torch.full((4,), 16.0, device=self.device)))
def test_eager_on_graph_disabled(self):
"""@eager_on_graph(enable=False) should be a no-op passthrough."""
@self.eager_on_graph(enable=False)
def my_fn(x):
return x + 1.0
# Should just be the original function
t = torch.tensor([1.0, 2.0], device=self.device)
result = my_fn(t)
self.assertTrue(
torch.allclose(result, torch.tensor([2.0, 3.0], device=self.device))
)
def test_eager_on_graph_outside_capture(self):
"""@eager_on_graph called outside capture should run the function directly."""
@self.eager_on_graph(enable=True)
def my_fn(x):
return x + 1.0
t = torch.tensor([1.0, 2.0], device=self.device)
result = my_fn(t)
self.assertTrue(
torch.allclose(result, torch.tensor([2.0, 3.0], device=self.device))
)
def test_replay_updates_output(self):
"""Replay should produce different results when input buffers change."""
x = torch.zeros(4, device=self.device)
y = torch.zeros(4, device=self.device)
@self.eager_on_graph(enable=True)
def scale(src):
return src * 3.0
graph = self.BreakableCUDAGraph()
stream = torch.cuda.Stream(self.device)
with self.BreakableCUDAGraphCapture(graph, stream=stream):
t = x + 1.0
t2 = scale(t)
y.copy_(t2)
# First replay: x=0 -> 0+1=1 -> 1*3=3
graph.replay()
torch.cuda.synchronize()
self.assertTrue(torch.allclose(y, torch.full((4,), 3.0, device=self.device)))
# Second replay: x=10 -> 10+1=11 -> 11*3=33
x.fill_(10.0)
graph.replay()
torch.cuda.synchronize()
self.assertTrue(torch.allclose(y, torch.full((4,), 33.0, device=self.device)))
class TestCopyOutput(CustomTestCase):
"""Test the _copy_output helper for structured output writeback."""
@classmethod
def setUpClass(cls):
if not torch.cuda.is_available():
raise unittest.SkipTest("CUDA not available")
try:
from cuda.bindings import runtime # noqa: F401
except ImportError:
raise unittest.SkipTest("cuda-python not installed")
from sglang.srt.model_executor.breakable_cuda_graph.breakable_cuda_graph import (
_copy_output,
)
cls._copy_output = staticmethod(_copy_output)
cls.device = torch.device("cuda:0")
def test_tensor_copy(self):
dst = torch.zeros(4, device=self.device)
src = torch.ones(4, device=self.device) * 5.0
result = self._copy_output(dst, src)
self.assertIs(result, dst)
self.assertTrue(torch.allclose(dst, src))
def test_dict_copy(self):
dst = {
"a": torch.zeros(4, device=self.device),
"b": torch.zeros(4, device=self.device),
}
src = {
"a": torch.ones(4, device=self.device),
"b": torch.ones(4, device=self.device) * 2.0,
}
result = self._copy_output(dst, src)
self.assertIs(result, dst)
self.assertTrue(torch.allclose(dst["a"], torch.ones(4, device=self.device)))
self.assertTrue(
torch.allclose(dst["b"], torch.ones(4, device=self.device) * 2.0)
)
def test_object_copy(self):
class FakeOutput:
def __init__(self, t, label):
self.tensor = t
self.label = label
dst = FakeOutput(torch.zeros(4, device=self.device), "old")
src = FakeOutput(torch.ones(4, device=self.device) * 3.0, "new")
result = self._copy_output(dst, src)
self.assertIs(result, dst)
self.assertTrue(
torch.allclose(dst.tensor, torch.ones(4, device=self.device) * 3.0)
)
self.assertEqual(dst.label, "new")
def test_non_tensor_fallback(self):
result = self._copy_output(42, 99)
self.assertEqual(result, 99)
class TestBreakGraphHelper(CustomTestCase):
"""Test the break_graph() convenience function."""
@classmethod
def setUpClass(cls):
if not torch.cuda.is_available():
raise unittest.SkipTest("CUDA not available")
try:
from cuda.bindings import runtime # noqa: F401
except ImportError:
raise unittest.SkipTest("cuda-python not installed")
from sglang.srt.model_executor.breakable_cuda_graph.breakable_cuda_graph import (
BreakableCUDAGraph,
BreakableCUDAGraphCapture,
break_graph,
)
cls.BreakableCUDAGraph = BreakableCUDAGraph
cls.BreakableCUDAGraphCapture = BreakableCUDAGraphCapture
cls.break_graph = staticmethod(break_graph)
cls.device = torch.device("cuda:0")
def test_break_graph_inserts_segment(self):
"""break_graph() should insert a graph break even though it does nothing."""
x = torch.zeros(4, device=self.device)
y = torch.zeros(4, device=self.device)
graph = self.BreakableCUDAGraph()
stream = torch.cuda.Stream(self.device)
with self.BreakableCUDAGraphCapture(graph, stream=stream):
t = x + 1.0
self.break_graph()
y.copy_(t + 2.0)
x.fill_(10.0)
graph.replay()
torch.cuda.synchronize()
# x=10 -> +1=11 -> break -> +2=13
self.assertTrue(torch.allclose(y, torch.full((4,), 13.0, device=self.device)))
if __name__ == "__main__":
unittest.main()