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sglang/test/registered/unit/spec/test_dflash_overlap_hostsync.py
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"""Unit tests for the DFlash spec-v2 host-sync removal: compact-rebuild
kernel bit-exactness, vocab-parallel draft sampler select, host seq-lens
upper bound, hybrid needs_cpu_seq_lens delegation, filter_batch host
keep-list."""
import unittest
from types import SimpleNamespace
import torch
from sglang.srt.runtime_context import get_context
from sglang.test.ci.ci_register import register_cuda_ci
from sglang.test.test_utils import CustomTestCase
register_cuda_ci(est_time=13, stage="base-b", runner_config="1-gpu-small")
_HAS_CUDA = torch.cuda.is_available()
def _compact_lens_exact(seq_lens, window, page):
fake_self = SimpleNamespace(
device=seq_lens.device, draft_window_size=window, page_size=page
)
from sglang.srt.speculative.dflash_worker_v2 import DFlashWorkerV2
return DFlashWorkerV2._compute_compact_draft_seq_lens(fake_self, seq_lens)
def _compact_lens_host(seq_lens, window, page):
fake_self = SimpleNamespace(draft_window_size=window, page_size=page)
out = torch.empty(seq_lens.numel(), dtype=torch.int32)
from sglang.srt.speculative.dflash_worker_v2 import DFlashWorkerV2
DFlashWorkerV2._compute_compact_draft_seq_lens_host(fake_self, seq_lens, out)
return out
class TestCompactSeqLensHostBound(CustomTestCase):
def test_upper_bound_of_exact(self):
g = torch.Generator().manual_seed(0)
for window, page in [(4096, 64), (4096, 1), (128, 32), (64, 1)]:
seq = torch.randint(1, 3 * window, (512,), generator=g)
exact = _compact_lens_exact(seq, window, page).to(torch.int64)
bound = _compact_lens_host(seq, window, page).to(torch.int64)
self.assertTrue(
bool((bound >= exact).all()),
f"host bound under-shoots exact at window={window} page={page}",
)
def test_sawtooth_counterexample(self):
# exact(4160) = 4096 < exact(4100) = 4100 at window=4096 page=64:
# a host mirror of the exact math fed the reserved over-estimate
# (4160 >= true 4100) would under-shoot; the envelope must not.
window, page = 4096, 64
true_len = torch.tensor([4100])
reserved = torch.tensor([4160])
exact_true = _compact_lens_exact(true_len, window, page).to(torch.int64)
exact_reserved = _compact_lens_exact(reserved, window, page).to(torch.int64)
self.assertLess(int(exact_reserved), int(exact_true))
bound = _compact_lens_host(reserved, window, page).to(torch.int64)
self.assertGreaterEqual(int(bound), int(exact_true))
class _FakeTpGroup:
"""Single-process stand-in for the TP GroupCoordinator: replays the
concatenation of all ranks' recorded all-gather inputs."""
def __init__(self, world_size):
self.world_size = world_size
self.recording = True
self.recorded = {} # (rank, call_idx) -> tensor
self.rank = 0
self.call_idx = 0
def all_gather_into_tensor(self, output, input_):
if self.recording:
self.recorded[(self.rank, self.call_idx)] = input_.clone()
else:
output.copy_(
torch.cat(
[self.recorded[(r, self.call_idx)] for r in range(self.world_size)]
)
)
self.call_idx += 1
class TestDflashDraftSamplerVocabParallel(CustomTestCase):
def _run(self, vocab, hidden, bs, block_size, world, dtype, weight=None):
from sglang.srt.speculative.dflash_worker_v2 import _DflashDraftSampler
device = torch.device("cuda" if _HAS_CUDA else "cpu")
g = torch.Generator(device=device).manual_seed(0)
if weight is None:
weight = torch.randn(vocab, hidden, generator=g, device=device, dtype=dtype)
hs = torch.randn(
bs * block_size, hidden, generator=g, device=device, dtype=dtype
)
shard = vocab // world
group = _FakeTpGroup(world)
samplers = [
_DflashDraftSampler(
weight=weight[r * shard : (r + 1) * shard].contiguous(),
block_size=block_size,
num_org=shard,
org_vocab_start=r * shard,
max_bs=bs,
tp_group=group,
)
for r in range(world)
]
for phase_recording in (True, False):
group.recording = phase_recording
for r, s in enumerate(samplers):
group.rank, group.call_idx = r, 0
s(hs)
n = bs * (block_size - 1)
ref_hs = hs.view(bs, block_size, -1)[:, 1:, :].reshape(-1, hidden)
ref = torch.argmax(torch.matmul(ref_hs.to(weight.dtype), weight.T), dim=-1).to(
torch.long
)
for r, s in enumerate(samplers):
torch.testing.assert_close(
s.out[:n], ref, rtol=0, atol=0, msg=f"rank {r} mismatch"
)
def test_matches_full_vocab_argmax(self):
self._run(
vocab=512, hidden=64, bs=3, block_size=8, world=4, dtype=torch.float32
)
def test_shard_boundary_tie_resolves_to_first_global_index(self):
# Duplicate row 10 (shard 0) at row 200 (shard 1): identical logits, so
# a correct fold must pick 10 (torch.argmax first-max semantics).
vocab, hidden = 256, 32
device = torch.device("cuda" if _HAS_CUDA else "cpu")
weight = torch.zeros(vocab, hidden, device=device)
weight[10] = 1.0
weight[200] = 1.0
self._run(
vocab=vocab,
hidden=hidden,
bs=1,
block_size=4,
world=2,
dtype=torch.float32,
weight=weight,
)
@unittest.skipUnless(_HAS_CUDA, "triton kernel requires CUDA")
class TestRebuildCompactDraftReqToToken(CustomTestCase):
def _legacy(self, draft, target, req_idx, start, lens, verify_2d, bs, block):
from sglang.srt.speculative.spec_utils import assign_req_to_token_pool_func
lens64 = lens.to(torch.int64)
max_len = int(lens64.max().item())
offs = torch.arange(max_len, device=lens.device).unsqueeze(0)
pos2d = start.to(torch.int64).unsqueeze(1) + offs
mask = offs < lens64.unsqueeze(1)
packed = target[req_idx.to(torch.int64)[:, None], pos2d.masked_fill(~mask, 0)][
mask
].to(torch.int64)
assign_req_to_token_pool_func(
req_idx, draft, torch.zeros_like(lens), lens, packed, bs
)
assign_req_to_token_pool_func(
req_idx, draft, lens, lens + block, verify_2d.reshape(-1), bs
)
def test_bitexact_vs_legacy(self):
from sglang.kernels.ops.speculative.cache_locs import (
rebuild_compact_draft_req_to_token_func,
)
device = torch.device("cuda")
for bs, window, page, block, seed in [
(1, 64, 1, 8, 0),
(16, 64, 32, 8, 1),
(13, 128, 64, 8, 2),
(7, 512, 64, 16, 3),
]:
g = torch.Generator(device=device).manual_seed(seed)
pool_rows, width = 4 * bs, 4 * window
seq = torch.randint(
1, width - block - 1, (bs,), generator=g, device=device
).to(torch.int64)
lens = _compact_lens_exact(seq, window, page).to(device)
start = seq - lens.to(torch.int64)
req_idx = torch.randperm(pool_rows, generator=g, device=device)[:bs]
target = torch.randint(
0, 2**30, (pool_rows, width), generator=g, device=device
).to(torch.int32)
verify_2d = torch.randint(
0, 2**30, (bs, block), generator=g, device=device
).to(torch.int64)
draft_width = window + page + block + 8
draft_a = torch.full(
(pool_rows, draft_width), -1, dtype=torch.int32, device=device
)
draft_b = draft_a.clone()
self._legacy(draft_a, target, req_idx, start, lens, verify_2d, bs, block)
rebuild_compact_draft_req_to_token_func(
draft_req_to_token=draft_b,
target_req_to_token=target,
req_pool_indices=req_idx,
suffix_start=start,
draft_prefix_lens=lens,
verify_out_cache_loc_2d=verify_2d,
batch_size=bs,
block_size=block,
)
torch.testing.assert_close(draft_b, draft_a, rtol=0, atol=0)
for i in range(bs):
total = int(lens[i].item()) + block
self.assertTrue(
bool((draft_b[req_idx[i], total:] == -1).all()),
"kernel wrote past the verify block",
)
class TestHybridNeedsCpuSeqLens(CustomTestCase):
def _make(self, prefill_flag, decode_flag, spec_mode="decode"):
from sglang.srt.layers.attention.hybrid_attn_backend import HybridAttnBackend
def backend(flag):
return SimpleNamespace(
needs_cpu_seq_lens=flag,
extend_dummy_seqs_capped_by_req_pool=False,
)
runner = SimpleNamespace(
server_args=SimpleNamespace(speculative_attention_mode=spec_mode),
kv_cache_dtype=torch.bfloat16,
token_to_kv_pool=None,
req_to_token_pool=None,
kv_index_translator=None,
model_config=SimpleNamespace(context_len=2048),
)
# The backend takes the mode from the published configuration, not from
# the runner it is handed.
override = get_context().override_server_args(
speculative_attention_mode=spec_mode
)
override.install()
self.addCleanup(override.restore)
return HybridAttnBackend(runner, backend(prefill_flag), backend(decode_flag))
def test_delegation(self):
# Only backends serving the spec decode loop count: decode always,
# prefill only when speculative_attention_mode routes verify to it.
self.assertFalse(self._make(False, False).needs_cpu_seq_lens)
self.assertFalse(self._make(True, False).needs_cpu_seq_lens)
self.assertTrue(self._make(False, True).needs_cpu_seq_lens)
self.assertTrue(self._make(True, False, spec_mode="prefill").needs_cpu_seq_lens)
self.assertFalse(
self._make(False, False, spec_mode="prefill").needs_cpu_seq_lens
)
class TestFilterBatchHostIndices(CustomTestCase):
def test_host_keep_list_matches_gpu_indices(self):
from sglang.srt.speculative.dflash_info_v2 import DFlashDraftInputV2
def make():
info = DFlashDraftInputV2.create_idle_input(device=torch.device("cpu"))
info.nxt_kv_lens_cpu = torch.tensor([10, 20, 30, 40], dtype=torch.int32)
info.nxt_kv_lens_sum = 100
info.future_indices = torch.tensor([5, 6, 7, 8])
return info
keep = [0, 2]
a, b = make(), make()
a.filter_batch(new_indices=torch.tensor(keep))
b.filter_batch(
new_indices=torch.tensor(keep),
new_indices_cpu=keep,
)
torch.testing.assert_close(a.nxt_kv_lens_cpu, b.nxt_kv_lens_cpu)
self.assertEqual(a.nxt_kv_lens_sum, b.nxt_kv_lens_sum)
torch.testing.assert_close(a.future_indices, b.future_indices)
if __name__ == "__main__":
unittest.main()