[FullCG] Preserve attention LSE through the custom-op boundary (#31050)
This commit is contained in:
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"""CPU unit tests for the graph-safe ``RadixAttention`` interface."""
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import unittest
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from contextlib import ExitStack
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from types import SimpleNamespace
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from unittest.mock import patch
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import torch
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import sglang.srt.layers.radix_attention as radix_attention_module
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from sglang.srt.layers.radix_attention import RadixAttention
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from sglang.srt.model_executor.forward_batch_info import ForwardMode
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from sglang.test.ci.ci_register import register_cpu_ci
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from sglang.test.test_utils import CustomTestCase
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register_cpu_ci(est_time=5, suite="base-a-test-cpu")
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class _RecordingAttentionBackend:
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def __init__(self, *, return_lse=True):
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self.calls = []
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self.return_lse = return_lse
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def forward(
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self,
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query,
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key,
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value,
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attention_layer,
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forward_batch,
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save_kv_cache,
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**kwargs,
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):
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self.calls.append(
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SimpleNamespace(
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query=query,
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key=key,
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value=value,
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attention_layer=attention_layer,
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output=forward_batch._attn_output,
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out_cache_loc=forward_batch.out_cache_loc.clone(),
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save_kv_cache=save_kv_cache,
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kwargs=kwargs,
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)
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)
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output = torch.full_like(query, 3)
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lse = torch.full((query.shape[0], query.shape[1]), 7, dtype=torch.float32)
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return (output, lse) if self.return_lse else output
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class TestRadixAttentionGraphInterface(CustomTestCase):
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@staticmethod
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def _new_layer() -> RadixAttention:
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layer = RadixAttention(
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num_heads=2,
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head_dim=3,
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scaling=1.0,
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num_kv_heads=2,
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layer_id=0,
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)
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return layer
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@staticmethod
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def _new_impl_context(
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attention_layers,
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*,
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mha_companion_layers=None,
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num_tokens=4,
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real_num_tokens=2,
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):
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forward_batch = SimpleNamespace(
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num_token_non_padded_cpu=real_num_tokens,
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out_cache_loc=torch.arange(num_tokens, dtype=torch.int64),
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_attn_output=None,
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)
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return SimpleNamespace(
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forward_batch=forward_batch,
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attention_layers=attention_layers,
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mha_companion_layers=mha_companion_layers,
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num_tokens=None,
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raw_num_tokens=None,
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)
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def test_forward_dispatches_all_graph_and_lse_variants(self):
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layer = self._new_layer()
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query = torch.zeros((4, 2, 3))
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key = torch.zeros_like(query)
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value = torch.zeros_like(query)
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op_names = {
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(False, False): "unified_attention_with_output",
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(False, True): "unified_attention_with_output_and_lse",
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(True, False): "breakable_unified_attention_with_output",
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(True, True): "breakable_unified_attention_with_output_and_lse",
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}
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for breakable in (False, True):
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for return_lse in (False, True):
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with self.subTest(breakable=breakable, return_lse=return_lse):
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forward_batch = SimpleNamespace(
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forward_mode=ForwardMode.EXTEND,
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mha_return_lse=return_lse,
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)
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calls = []
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def output_only(*args, **kwargs):
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args[3].fill_(5)
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calls.append(kwargs)
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def output_and_lse(*args, **kwargs):
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args[3].fill_(5)
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calls.append(kwargs)
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return torch.full((4, 2), 11, dtype=torch.float32)
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with ExitStack() as stack:
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stack.enter_context(
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patch.object(
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radix_attention_module,
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"get_tc_piecewise_forward_context",
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return_value=SimpleNamespace(
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mha_companion_layers=[layer]
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),
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)
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)
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stack.enter_context(
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patch.object(
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radix_attention_module,
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"is_in_breakable_cuda_graph",
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return_value=breakable,
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)
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)
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mocks = {
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name: stack.enter_context(
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patch.object(
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radix_attention_module,
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name,
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side_effect=(
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output_and_lse
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if name.endswith("and_lse")
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else output_only
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),
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)
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)
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for name in op_names.values()
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}
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result = layer(
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query,
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key,
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value,
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forward_batch,
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key_value_num_tokens=3,
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)
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selected_name = op_names[(breakable, return_lse)]
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for name, mock in mocks.items():
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self.assertEqual(mock.call_count, int(name == selected_name))
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self.assertEqual(
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calls,
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[
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{
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"use_mha_companion": True,
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"key_value_num_tokens": 3,
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}
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],
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)
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if return_lse:
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output, lse = result
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self.assertEqual(lse.shape, (4, 2))
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self.assertTrue(torch.all(lse == 11))
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else:
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output = result
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self.assertEqual(output.shape, query.shape)
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self.assertTrue(torch.all(output == 5))
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def test_impl_preserves_attention_identity_and_lse(self):
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mqa = SimpleNamespace()
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mha = SimpleNamespace()
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context = self._new_impl_context([mqa], mha_companion_layers=[mha])
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forward_batch = context.forward_batch
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original_out_cache_loc = forward_batch.out_cache_loc
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backend = _RecordingAttentionBackend()
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query = torch.zeros((4, 2, 3))
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with (
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patch.object(
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radix_attention_module,
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"get_tc_piecewise_forward_context",
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return_value=context,
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),
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patch.object(
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radix_attention_module, "get_attn_backend", return_value=backend
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),
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):
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for use_mha_companion, expected_layer in ((False, mqa), (True, mha)):
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with self.subTest(use_mha_companion=use_mha_companion):
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output = torch.empty_like(query)
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lse = radix_attention_module._unified_attention_with_output_impl(
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query,
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query,
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query,
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output,
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False,
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0,
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use_mha_companion,
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True,
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)
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call_record = backend.calls[-1]
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self.assertIs(call_record.attention_layer, expected_layer)
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self.assertEqual(call_record.query.shape, (2, 2, 3))
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self.assertEqual(call_record.key.shape, (2, 2, 3))
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self.assertEqual(call_record.value.shape, (2, 2, 3))
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self.assertEqual(call_record.output.shape, (2, 2, 3))
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self.assertEqual(call_record.out_cache_loc.tolist(), [0, 1])
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self.assertFalse(call_record.save_kv_cache)
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self.assertTrue(torch.all(output[:2] == 3))
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self.assertEqual(lse.shape, (4, 2))
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self.assertTrue(torch.all(lse[:2] == 7))
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self.assertTrue(torch.all(lse[2:] == 0))
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self.assertIs(forward_batch.out_cache_loc, original_out_cache_loc)
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def test_impl_uses_independent_query_and_key_value_extents(self):
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attention_layer = SimpleNamespace()
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context = self._new_impl_context([attention_layer])
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forward_batch = context.forward_batch
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original_out_cache_loc = forward_batch.out_cache_loc
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backend = _RecordingAttentionBackend()
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query = torch.zeros((4, 2, 3))
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key = torch.zeros((6, 2, 3))
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value = torch.zeros((6, 2, 3))
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k_rope = torch.zeros((6, 2, 1))
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output = torch.empty_like(query)
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with (
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patch.object(
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radix_attention_module,
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"get_tc_piecewise_forward_context",
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return_value=context,
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),
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patch.object(
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radix_attention_module, "get_attn_backend", return_value=backend
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),
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):
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lse = radix_attention_module._unified_attention_with_output_impl(
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query,
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key,
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value,
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output,
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False,
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0,
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False,
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True,
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key_value_num_tokens=5,
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k_rope=k_rope,
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)
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call_record = backend.calls[-1]
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self.assertEqual(call_record.query.shape, (2, 2, 3))
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self.assertEqual(call_record.key.shape, (5, 2, 3))
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self.assertEqual(call_record.value.shape, (5, 2, 3))
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self.assertEqual(call_record.kwargs["k_rope"].shape, (5, 2, 1))
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self.assertEqual(call_record.output.shape, (2, 2, 3))
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self.assertEqual(lse.shape, (4, 2))
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self.assertIs(forward_batch.out_cache_loc, original_out_cache_loc)
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def test_impl_preserves_output_only_contract(self):
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attention_layer = SimpleNamespace()
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context = self._new_impl_context([attention_layer])
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forward_batch = context.forward_batch
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original_out_cache_loc = forward_batch.out_cache_loc
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backend = _RecordingAttentionBackend(return_lse=False)
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query = torch.zeros((4, 2, 3))
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output = torch.empty_like(query)
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with (
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patch.object(
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radix_attention_module,
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"get_tc_piecewise_forward_context",
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return_value=context,
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),
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patch.object(
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radix_attention_module, "get_attn_backend", return_value=backend
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),
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):
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lse = radix_attention_module._unified_attention_with_output_impl(
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query,
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query,
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query,
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output,
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False,
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0,
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False,
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False,
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)
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self.assertIsNone(lse)
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self.assertIs(backend.calls[-1].attention_layer, attention_layer)
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self.assertTrue(torch.all(output[:2] == 3))
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self.assertIs(forward_batch.out_cache_loc, original_out_cache_loc)
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def test_lse_fake_impl_declares_shape_and_dtype(self):
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query = torch.empty((5, 3, 7), dtype=torch.float16)
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output = torch.empty_like(query)
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lse = radix_attention_module._unified_attention_with_output_and_lse_fake(
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query,
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None,
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None,
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output,
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False,
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0,
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)
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self.assertEqual(lse.shape, (5, 3))
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self.assertEqual(lse.dtype, torch.float32)
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self.assertEqual(lse.device, query.device)
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if __name__ == "__main__":
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unittest.main()
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