[diffusion] optimize: precompute ideogram4 denoising metadata (#27443)

python/sglang/multimodal_gen/runtime/models/dits/ideogram.py

@@ -393,6 +393,8 @@ class Ideogram4Transformer2DModel(BaseDiT):
         position_ids: torch.Tensor,
         segment_ids: torch.Tensor,
         indicator: torch.Tensor,
+        attn_mask: torch.Tensor | None = None,
+        attn_mask_meta: dict | None = None,
         **kwargs,
     ) -> torch.Tensor:
         param_dtype = self.embed_image_indicator.weight.dtype
@@ -421,8 +423,10 @@ class Ideogram4Transformer2DModel(BaseDiT):
         cos = cos.unsqueeze(2)
         sin = sin.unsqueeze(2)
         # ideogram uses -1 padding; varlen meta enables fa packed attention
-        attn_mask = segment_ids > 0
+        if attn_mask is None:
-        attn_mask_meta = build_varlen_mask_meta(attn_mask)
+            attn_mask = segment_ids > 0
+        if attn_mask_meta is None:
+            attn_mask_meta = build_varlen_mask_meta(attn_mask)
         for layer in self.layers:
             h = layer(
                 h,

python/sglang/multimodal_gen/runtime/pipelines_core/stages/model_specific_stages/ideogram.py

@@ -11,6 +11,7 @@ from sglang.multimodal_gen.configs.pipeline_configs.ideogram import (
 )
 from sglang.multimodal_gen.configs.sample.ideogram import IDEOGRAM4_PRESETS
 from sglang.multimodal_gen.runtime.distributed import get_local_torch_device
+from sglang.multimodal_gen.runtime.layers.attention import build_varlen_mask_meta
 from sglang.multimodal_gen.runtime.managers.forward_context import set_forward_context
 from sglang.multimodal_gen.runtime.managers.memory_managers.component_manager import (
     ComponentUse,
@@ -357,6 +358,8 @@ class Ideogram4DenoisingStage(DenoisingStage):
         guidance_schedule = torch.as_tensor(
             preset_cfg["guidance_schedule"], dtype=torch.float32, device=device
         )
+        schedule_values = schedule(step_intervals)
+        schedule_deltas = schedule_values[:-1] - schedule_values[1:]
 
         self.scheduler.set_timesteps(num_steps, device=device)
         batch.scheduler = self.scheduler
@@ -385,6 +388,8 @@ class Ideogram4DenoisingStage(DenoisingStage):
         neg_position_ids = data["position_ids"][:, max_text_tokens:]
         neg_segment_ids = data["segment_ids"][:, max_text_tokens:]
         neg_indicator = data["indicator"][:, max_text_tokens:]
+        attn_mask = data["segment_ids"] > 0
+        neg_attn_mask = neg_segment_ids > 0
         neg_llm_features = torch.zeros(
             batch_size,
             num_image_tokens,
@@ -395,13 +400,17 @@ class Ideogram4DenoisingStage(DenoisingStage):
         ctx.latents = z
         ctx.extra.update(
             {
-                "ideogram4_schedule": schedule,
+                "ideogram4_schedule_values": schedule_values,
-                "ideogram4_step_intervals": step_intervals,
+                "ideogram4_schedule_deltas": schedule_deltas,
                 "ideogram4_guidance_schedule": guidance_schedule,
                 "ideogram4_text_z_padding": text_z_padding,
+                "ideogram4_attn_mask": attn_mask,
+                "ideogram4_attn_mask_meta": build_varlen_mask_meta(attn_mask),
                 "ideogram4_neg_position_ids": neg_position_ids,
                 "ideogram4_neg_segment_ids": neg_segment_ids,
                 "ideogram4_neg_indicator": neg_indicator,
+                "ideogram4_neg_attn_mask": neg_attn_mask,
+                "ideogram4_neg_attn_mask_meta": build_varlen_mask_meta(neg_attn_mask),
                 "ideogram4_neg_llm_features": neg_llm_features,
             }
         )
@@ -418,14 +427,13 @@ class Ideogram4DenoisingStage(DenoisingStage):
         z = ctx.latents.to(dtype=torch.float32)
         llm_features = batch.prompt_embeds[0]
         max_text_tokens = data["max_text_tokens"]
-        schedule = ctx.extra["ideogram4_schedule"]
+        schedule_values = ctx.extra["ideogram4_schedule_values"]
-        step_intervals = ctx.extra["ideogram4_step_intervals"]
+        schedule_deltas = ctx.extra["ideogram4_schedule_deltas"]
         guidance_schedule = ctx.extra["ideogram4_guidance_schedule"]
         i = step.t_int
 
-        t_val = float(schedule(step_intervals[i + 1].unsqueeze(0)).item())
+        t_val = schedule_values[i + 1]
-        s_val = float(schedule(step_intervals[i].unsqueeze(0)).item())
+        t = t_val.expand(z.shape[0])
-        t = torch.full((z.shape[0],), t_val, dtype=torch.float32, device=z.device)
         pos_z = torch.cat([ctx.extra["ideogram4_text_z_padding"], z], dim=1)
         use_nvtx = self.current_use_nvtx
 
@@ -442,6 +450,8 @@ class Ideogram4DenoisingStage(DenoisingStage):
                     position_ids=data["position_ids"],
                     segment_ids=data["segment_ids"],
                     indicator=data["indicator"],
+                    attn_mask=ctx.extra["ideogram4_attn_mask"],
+                    attn_mask_meta=ctx.extra["ideogram4_attn_mask_meta"],
                 )
                 pos_v = pos_out[:, max_text_tokens:]
 
@@ -458,13 +468,15 @@ class Ideogram4DenoisingStage(DenoisingStage):
                     position_ids=ctx.extra["ideogram4_neg_position_ids"],
                     segment_ids=ctx.extra["ideogram4_neg_segment_ids"],
                     indicator=ctx.extra["ideogram4_neg_indicator"],
+                    attn_mask=ctx.extra["ideogram4_neg_attn_mask"],
+                    attn_mask_meta=ctx.extra["ideogram4_neg_attn_mask_meta"],
                 )
 
         with maybe_nvtx_range("scheduler_step", use_nvtx):
             velocity = (
                 guidance_schedule[i] * pos_v + (1.0 - guidance_schedule[i]) * neg_v
             )
-            ctx.latents = z + velocity * (s_val - t_val)
+            ctx.latents = z + velocity * schedule_deltas[i]
 
 
 class Ideogram4DecodingStage(PipelineStage):