Support deterministic inference with triton backend (#10694)

python/sglang/environ.py

@@ -201,6 +201,8 @@ class Envs:
     SGLANG_ENABLE_DETERMINISTIC_INFERENCE = EnvBool(False)
     SGLANG_FLASHINFER_PREFILL_SPLIT_TILE_SIZE = EnvInt(4096)
     SGLANG_FLASHINFER_DECODE_SPLIT_TILE_SIZE = EnvInt(2048)
+    SGLANG_TRITON_PREFILL_TRUNCATION_ALIGN_SIZE = EnvInt(4096)
+    SGLANG_TRITON_DECODE_SPLIT_TILE_SIZE = EnvInt(256)
 
     # fmt: on
 

python/sglang/srt/layers/attention/triton_backend.py

@@ -12,7 +12,12 @@ from sglang.srt.layers.attention.utils import create_flashinfer_kv_indices_trito
 from sglang.srt.layers.dp_attention import get_attention_tp_size
 from sglang.srt.layers.radix_attention import AttentionType
 from sglang.srt.model_executor.forward_batch_info import ForwardBatch, ForwardMode
-from sglang.srt.utils import get_bool_env_var, get_device_core_count, next_power_of_2
+from sglang.srt.utils import (
+    get_bool_env_var,
+    get_device_core_count,
+    get_int_env_var,
+    next_power_of_2,
+)
 
 if TYPE_CHECKING:
     from sglang.srt.layers.radix_attention import RadixAttention
@@ -94,7 +99,25 @@ class TritonAttnBackend(AttentionBackend):
             "SGLANG_TRITON_DECODE_ATTN_STATIC_KV_SPLITS", "false"
         )
         self.max_kv_splits = model_runner.server_args.triton_attention_num_kv_splits
-        self.split_tile_size = model_runner.server_args.triton_attention_split_tile_size
+
+        # Decide whether enable deterministic inference with batch-invariant operations
+        self.enable_deterministic = (
+            model_runner.server_args.enable_deterministic_inference
+        )
+
+        # Configure deterministic inference settings
+        if self.enable_deterministic:
+            # Use fixed split tile size for batch invariance
+            self.split_tile_size = get_int_env_var(
+                "SGLANG_TRITON_DECODE_SPLIT_TILE_SIZE", 256
+            )
+            # Set static_kv_splits to False to use deterministic logic instead
+            self.static_kv_splits = False
+        else:
+            self.split_tile_size = (
+                model_runner.server_args.triton_attention_split_tile_size
+            )
+
         if self.split_tile_size is not None:
             self.max_kv_splits = (
                 self.max_context_len + self.split_tile_size - 1
@@ -154,13 +177,23 @@ class TritonAttnBackend(AttentionBackend):
             num_group * num_seq == num_token
         ), f"num_seq({num_seq}), num_token({num_token}), something goes wrong!"
 
-        if self.static_kv_splits or self.device_core_count <= 0:
+        # Legacy dynamic splitting logic (non-deterministic)
+        if (
+            self.static_kv_splits or self.device_core_count <= 0
+        ) and not self.enable_deterministic:
             num_kv_splits.fill_(self.max_kv_splits)
             return
 
-        if self.split_tile_size is not None:
+        # deterministic
+        if self.split_tile_size is not None and self.enable_deterministic:
+            # expand seq_lens to match num_token
+            if num_group > 1:
+                expanded_seq_lens = seq_lens.repeat_interleave(num_group)
+            else:
+                expanded_seq_lens = seq_lens
+
             num_kv_splits[:] = (
-                seq_lens + self.split_tile_size - 1
+                expanded_seq_lens + self.split_tile_size - 1
             ) // self.split_tile_size
             return
 

python/sglang/srt/managers/scheduler.py

@@ -565,16 +565,8 @@ class Scheduler(
         if get_bool_env_var("SGLANG_GC_LOG"):
             configure_gc_logger()
 
-        # Init prefill kv split size when deterministic inference is enabled with flashinfer attention backend
+        # Init prefill kv split size when deterministic inference is enabled with various attention backends
-        if (
+        self.init_deterministic_inference_config()
-            self.server_args.enable_deterministic_inference
-            and self.server_args.attention_backend == "flashinfer"
-        ):
-            self.truncation_align_size = get_int_env_var(
-                "SGLANG_FLASHINFER_PREFILL_SPLIT_TILE_SIZE", 4096
-            )
-        else:
-            self.truncation_align_size = None
 
         # Init request dispatcher
         self._request_dispatcher = TypeBasedDispatcher(
@@ -621,6 +613,23 @@ class Scheduler(
             ]
         )
 
+    def init_deterministic_inference_config(self):
+        """Initialize deterministic inference configuration for different attention backends."""
+        if not self.server_args.enable_deterministic_inference:
+            self.truncation_align_size = None
+            return
+
+        backend_sizes = {
+            "flashinfer": ("SGLANG_FLASHINFER_PREFILL_SPLIT_TILE_SIZE", 4096),
+            "triton": ("SGLANG_TRITON_PREFILL_TRUNCATION_ALIGN_SIZE", 4096),
+        }
+        env_var, default_size = backend_sizes.get(
+            self.server_args.attention_backend, (None, None)
+        )
+        self.truncation_align_size = (
+            get_int_env_var(env_var, default_size) if env_var else None
+        )
+
     def init_tokenizer(self):
         server_args = self.server_args
         self.is_generation = self.model_config.is_generation

python/sglang/srt/server_args.py

@@ -118,7 +118,7 @@ DISAGG_TRANSFER_BACKEND_CHOICES = ["mooncake", "nixl", "ascend", "fake"]
 
 GRAMMAR_BACKEND_CHOICES = ["xgrammar", "outlines", "llguidance", "none"]
 
-DETERMINISTIC_ATTENTION_BACKEND_CHOICES = ["flashinfer", "fa3"]
+DETERMINISTIC_ATTENTION_BACKEND_CHOICES = ["flashinfer", "fa3", "triton"]
 
 
 # Allow external code to add more choices