Add automatic NTK-aware alpha scaling to model

* enables automatic calculation of NTK-aware alpha scaling for models if the rope_alpha arg is not passed in the config, using the same formula used for draft models

model.py

@@ -69,10 +69,17 @@ def progress(loaded_modules: int, total_modules: int, loading_draft: bool)
         self.config = ExLlamaV2Config()
         self.config.model_dir = str(model_directory.resolve())
         self.config.prepare()
+
+        base_seq_len = self.config.max_seq_len
 
         if "max_seq_len" in kwargs: self.config.max_seq_len = kwargs["max_seq_len"]
         if "rope_scale" in kwargs: self.config.scale_pos_emb = kwargs["rope_scale"]
-        if "rope_alpha" in kwargs: self.config.scale_alpha_value = kwargs["rope_alpha"]
+        if "rope_alpha" in kwargs:
+            self.config.scale_alpha_value = kwargs["rope_alpha"]
+        else:
+            ratio = self.config.max_seq_len / base_seq_len
+            alpha = -0.13436 + 0.80541 * ratio + 0.28833 * ratio ** 2
+            self.config.scale_alpha_value = alpha
         if "no_flash_attn" in kwargs: self.config.no_flash_attn = kwargs["no_flash_attn"]
 
         if "low_mem" in kwargs and kwargs["low_mem"]:
@@ -102,7 +109,7 @@ def progress(loaded_modules: int, total_modules: int, loading_draft: bool)
             self.draft_config.prepare()
 
             if "draft_rope_alpha" in kwargs:
-                self.draft_config.scale_alpha_value = kwargs.get("draft_rope_alpha") or 1
+                self.draft_config.scale_alpha_value = kwargs.get("draft_rope_alpha")
             else:
                 ratio = self.config.max_seq_len / self.draft_config.max_seq_len
                 alpha = -0.13436 + 0.80541 * ratio + 0.28833 * ratio ** 2