Add precompute_ref_log_probs to config schema (#3555) [skip ci]

* Add precompute_ref_log_probs to config schema

* chore: add description for config

* Add test for precompute_ref_log_probs and move to training args

* useing precompute logprobs as the default slows down CI as it has to precompute

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Co-authored-by: NanoCode012 <nano@axolotl.ai>
Co-authored-by: Wing Lian <wing@axolotl.ai>

tests/core/test_builders.py

@@ -289,6 +289,7 @@ class TestHFRLTrainerBuilder:
         # assert training_arguments.gradient_checkpointing is True
 
     def test_dpo_training_arguments(self, dpo_cfg, model, tokenizer):
+        dpo_cfg["precompute_ref_log_probs"] = True
         builder = HFRLTrainerBuilder(dpo_cfg, model, tokenizer)
         training_arguments, _ = builder._build_training_arguments(100)
 
@@ -298,6 +299,7 @@ class TestHFRLTrainerBuilder:
         assert hasattr(training_arguments, "use_weighting")
         assert training_arguments.use_weighting is True
         assert training_arguments.label_smoothing == 0.1
+        assert training_arguments.precompute_ref_log_probs is True
 
     def test_orpo_training_arguments(self, orpo_cfg, model, tokenizer):
         builder = HFRLTrainerBuilder(orpo_cfg, model, tokenizer)