Phi-3 conversation format, example training script and perplexity metric (#1582)

* phi-3 support and perplexity metric

* phi-3 chat template

* metrics updates

* chore: lint

* fix assertion on Tensor

* fix tests since tokenization happens in the metric

* fix perplexity value of shorter passage

---------

Co-authored-by: Wing Lian <wing.lian@gmail.com>

examples/phi/phi3-ft.yml

@@ -0,0 +1,64 @@
+base_model: microsoft/Phi-3-mini-4k-instruct
+trust_remote_code: true
+model_type: AutoModelForCausalLM
+tokenizer_type: AutoTokenizer
+chat_template: phi_3
+
+load_in_8bit: false
+load_in_4bit: false
+strict: false
+
+datasets:
+  - path: garage-bAInd/Open-Platypus
+    type: alpaca:phi
+
+dataset_prepared_path:
+val_set_size: 0.01
+output_dir: ./out
+
+sequence_len: 4096
+sample_packing: true
+pad_to_sequence_len: true
+
+adapter: lora
+lora_model_dir:
+lora_r: 64
+lora_alpha: 32
+lora_dropout: 0.05
+lora_target_linear: true
+lora_fan_in_fan_out:
+
+gradient_accumulation_steps: 1
+micro_batch_size: 2
+num_epochs: 1
+optimizer: adamw_torch
+adam_beta2: 0.95
+adam_epsilon: 0.00001
+max_grad_norm: 1.0
+lr_scheduler: cosine
+learning_rate: 5.0e-6
+
+train_on_inputs: false
+group_by_length: false
+bf16: auto
+
+gradient_checkpointing: true
+gradient_checkpointing_kwargs:
+  use_reentrant: True
+early_stopping_patience: 3
+logging_steps: 1
+flash_attention: true
+
+eval_steps: 1000
+save_steps: 5000
+eval_table_size: 2
+eval_batch_size: 2
+eval_sample_packing: false
+eval_max_new_tokens: 32
+eval_causal_lm_metrics: ["perplexity"]
+do_causal_lm_eval: true
+
+warmup_ratio: 0.2
+debug: true
+weight_decay: 0.1
+resize_token_embeddings_to_32x: true