[diffusion] Ideogram 4: fuse RMSNorm modulate/gate chains via the Z-Image Triton suite behind quality=high (H200 e2e -2.9%/-3.4%) (#33822)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

test/registered/kernels/ops/diffusion/test_fused_gate_rmsnorm.py

@@ -0,0 +1,54 @@
+"""Core checks for the quality-gated fused gate-RMSNorm (Z-Image suite reuse)."""
+
+import sys
+
+import pytest
+import torch
+import torch.nn as nn
+import torch.nn.functional as F
+
+from sglang.kernels.ops.diffusion import fused_gate_rmsnorm as fgn
+from sglang.test.ci.ci_register import register_cuda_ci
+
+register_cuda_ci(est_time=4, stage="base-b-kernel-unit", runner_config="1-gpu-large")
+pytestmark = pytest.mark.skipif(not torch.cuda.is_available(), reason="CUDA required")
+DIM, EPS = 4608, 1e-5  # Ideogram 4 hidden size / norm_eps
+
+
+class _Site(nn.Module):
+    def __init__(self, dtype=torch.bfloat16):
+        super().__init__()
+        self.norm = nn.RMSNorm(DIM, eps=EPS, device="cuda", dtype=dtype)
+        fgn.mark_fused_gate_rmsnorm_site(self, ("norm",))
+
+
+def test_fused_matches_ideogram_reference():
+    torch.manual_seed(0)
+    site = _Site()
+    w = site.norm.weight.data
+    x = torch.randn(1, 64, DIM, device="cuda", dtype=torch.bfloat16)
+    residual = torch.randn_like(x)
+    # adaln-style strided chunks, as produced by Ideogram's modulation .chunk()
+    mods = torch.randn(1, 1, 2 * DIM, device="cuda", dtype=torch.bfloat16)
+    scale, gate = mods.chunk(2, dim=-1)
+    assert fgn.mount_fused_gate_rmsnorm(site)
+    got_scale = fgn.fused_rmsnorm_scale(x, w, 1.0 + scale, EPS)
+    got_gate = fgn.fused_rmsnorm_tanh_residual(x, gate, residual, w, EPS)
+    ref_scale = F.rms_norm(x, (DIM,), w, EPS) * (1.0 + scale)
+    ref_gate = residual + torch.tanh(gate) * F.rms_norm(x, (DIM,), w, EPS)
+    # fused path uses bf16-native norm statistics: close, not bit-exact
+    torch.testing.assert_close(got_scale, ref_scale, atol=8e-2, rtol=4e-2)
+    torch.testing.assert_close(got_gate, ref_gate, atol=8e-2, rtol=4e-2)
+
+
+def test_mount_guards_all_or_nothing():
+    good, bad = _Site(), _Site(torch.float32)
+    assert not fgn.mount_fused_gate_rmsnorm(nn.ModuleList([good, bad]))
+    assert not good._sgl_fused_gate_rmsnorm_enabled
+    assert fgn.mount_fused_gate_rmsnorm(good)
+    fgn.unmount_fused_gate_rmsnorm(good)
+    assert not good._sgl_fused_gate_rmsnorm_enabled
+
+
+if __name__ == "__main__":
+    sys.exit(pytest.main([__file__]))