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K3/tests/kernels/test_triton_bwd.py
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dela 584f7e9e73 Initial K3 snapshot: 0.5B KDA/MLA/MoE train path
Standalone tree split from LLMRL/projects/kda. Includes Triton dt_bias
backward fix, train_k3 --preset 0.5b, SFT, Docker runtime, and tests.
2026-08-25 14:43:17 +08:00

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2.5 KiB
Python

"""L4: vendored FLA Triton bwd vs naive chunked.
Triton kernels run in fp32, so this checks VJP vs L2 rather than fp64 gradcheck.
Inputs L2-normalize q/k like the trained KDA path.
"""
import pytest
import torch
import torch.nn.functional as F
from kda.ops.reference.chunkwise import naive_chunk_kda
from kda.ops.triton.chunk_fwd import chunk_kda_fwd
pytestmark = pytest.mark.skipif(not torch.cuda.is_available(), reason="CUDA required")
def test_bwd_matches_naive():
B, T, H, HV, K, V = 2, 64, 4, 8, 32, 32
torch.manual_seed(5)
dev = "cuda"
q = F.normalize(torch.randn(B, T, H, K, device=dev), dim=-1).requires_grad_()
k = F.normalize(torch.randn(B, T, H, K, device=dev), dim=-1).requires_grad_()
v = torch.randn(B, T, HV, V, device=dev, requires_grad=True)
g = (-torch.rand(B, T, HV, K, device=dev) * 2).requires_grad_()
beta = torch.rand(B, T, HV, device=dev, requires_grad=True)
o_na, _ = naive_chunk_kda(q, k, v, g, beta, chunk_size=64)
o_na.sum().backward()
dq_na, dk_na = q.grad.clone(), k.grad.clone()
dv_na, dg_na, db_na = v.grad.clone(), g.grad.clone(), beta.grad.clone()
q.grad = k.grad = v.grad = g.grad = beta.grad = None
o_tr, _ = chunk_kda_fwd(q, k, v, g, beta, chunk_size=64)
o_tr.sum().backward()
dq_tr, dk_tr = q.grad.clone(), k.grad.clone()
dv_tr, dg_tr, db_tr = v.grad.clone(), g.grad.clone(), beta.grad.clone()
torch.testing.assert_close(dq_tr, dq_na, rtol=2e-2, atol=2e-3)
torch.testing.assert_close(dk_tr, dk_na, rtol=2e-2, atol=2e-3)
torch.testing.assert_close(dv_tr, dv_na, rtol=2e-2, atol=2e-3)
torch.testing.assert_close(dg_tr, dg_na, rtol=2e-2, atol=2e-3)
torch.testing.assert_close(db_tr, db_na, rtol=2e-2, atol=2e-3)
def test_triton_kda_attention_backward_dt_bias_rank2():
"""Layer stores dt_bias as [HV, K]; Triton bwd used to return a flat [HV*K]."""
from kda.layers.kda_attn import KDAAttention
torch.manual_seed(0)
model = KDAAttention(
hidden_size=64,
num_heads=4,
num_value_heads=8,
head_dim=16,
chunk_size=64,
kda_backend="triton",
).cuda()
x = torch.randn(2, 64, 64, device="cuda")
model(x).sum().backward()
assert model.dt_bias.grad is not None
assert model.dt_bias.grad.shape == model.dt_bias.shape
assert model.A_log.grad is not None
assert torch.isfinite(model.dt_bias.grad).all()
if __name__ == "__main__":
test_bwd_matches_naive()
test_triton_kda_attention_backward_dt_bias_rank2()