fix bf16 check when preprocessing data (#1140)

src/axolotl/utils/config.py

@@ -182,7 +182,11 @@ def validate_config(cfg):
         if not cfg.bf16 and not cfg.bfloat16:
             LOG.info("bf16 support detected, but not enabled for this configuration.")
     else:
-        if not cfg.merge_lora and (cfg.bf16 or cfg.bfloat16):
+        if (
+            not cfg.merge_lora
+            and not cfg.is_preprocess
+            and (cfg.bf16 is True or cfg.bfloat16 is True)
+        ):
             raise ValueError(
                 "bf16 requested, but AMP is not supported on this GPU. Requires Ampere series or above."
             )