checkpoint model on first step callback (#2906)

* checkpoint model on first step callback

* remove debug

* add test cases; update existing tests not to save on first step

* move test out of solo

* delete

* default to False

* typo

examples/deepseek-v2/fft-fsdp-16b.yaml

@@ -55,3 +55,5 @@ fsdp_config:
   fsdp_transformer_layer_cls_to_wrap: DeepseekV2DecoderLayer
   fsdp_state_dict_type: FULL_STATE_DICT
   fsdp_sharding_strategy: FULL_SHARD
+
+# save_first_step: true  # uncomment this to validate checkpoint saving works with your config

examples/deepseek-v2/qlora-fsdp-2_5.yaml

@@ -79,3 +79,5 @@ fsdp_config:
   fsdp_transformer_layer_cls_to_wrap: DeepseekV2DecoderLayer
   fsdp_state_dict_type: FULL_STATE_DICT
   fsdp_sharding_strategy: FULL_SHARD
+
+# save_first_step: true  # uncomment this to validate checkpoint saving works with your config