Model: Add override base seq len

Some models (such as mistral and mixtral) set their base sequence
length to 32k due to assumptions of support for sliding window
attention.

Therefore, add this parameter to override the base sequence length
of a model which helps with auto-calculation of rope alpha.

If auto-calculation of rope alpha isn't being used, the max_seq_len
parameter works fine as is.

Signed-off-by: kingbri <bdashore3@proton.me>

OAI/types/model.py

@@ -34,8 +34,9 @@ class DraftModelLoadRequest(BaseModel):
 class ModelLoadRequest(BaseModel):
     name: str
 
-    # Max seq len is defaulted when loading the model itself
-    max_seq_len: Optional[int] = None
+    # Max seq len is fetched from config.json of the model by default
+    max_seq_len: Optional[int] = Field(description = "Leave this blank to use the model's base sequence length", default = None)
+    override_base_seq_len: Optional[int] = Field(description = "Overrides the model's base sequence length. Leave blank if unsure", default = None)
     gpu_split_auto: Optional[bool] = True
     gpu_split: Optional[List[float]] = Field(default_factory=list)
     rope_scale: Optional[float] = 1.0

config_sample.yml

@@ -37,9 +37,15 @@ model:
 
   # The below parameters apply only if model_name is set
 
-  # Override maximum model context length (default: None)
+  # Max sequence length (default: None)
+  # Fetched from the model's base sequence length in config.json by default
   max_seq_len:
 
+  # Overrides base model context length (default: None)
+  # WARNING: Don't set this unless you know what you're doing!
+  # Only use this if the model's base sequence length in config.json is incorrect (ex. Mistral/Mixtral models)
+  override_base_seq_len:
+
   # Automatically allocate resources to GPUs (default: True)
   gpu_split_auto: True
 

model.py

@@ -85,14 +85,19 @@ class ModelContainer:
         self.config.max_seq_len = 4096
         self.config.prepare()
 
-        # Then override the max_seq_len if present
-        override_max_seq_len = kwargs.get("max_seq_len")
-        if override_max_seq_len:
-            self.config.max_seq_len = kwargs.get("max_seq_len")
+        # Then override the base_seq_len if present
+        override_base_seq_len = kwargs.get("override_base_seq_len")
+        if override_base_seq_len:
+            self.config.max_seq_len = override_base_seq_len
 
         # Grab the base model's sequence length before overrides for rope calculations
         base_seq_len = self.config.max_seq_len
 
+        # Set the target seq len if present
+        target_max_seq_len = kwargs.get("max_seq_len")
+        if target_max_seq_len:
+            self.config.max_seq_len = target_max_seq_len
+
         # Set the rope scale
         self.config.scale_pos_emb = unwrap(kwargs.get("rope_scale"), 1.0)