Checkpoint User Guide¶
In many cases, Stand-alone training and Distributed training can be aborted by the software problem or hardware problem. More seriously, we waste so much time and the performance of the machine but get nothing, which makes us frustrating and we have to restart it again.
The feature of
Checkpoint can save Intermediate model variables, lookup table variable, and other needs data in checkpoint directory. When the exception occurs, we can load these variables from the checkpoint directory immediately.
Complete Features Currently：¶
The Trainer 0 will save model variables in training.
Each of the Trainer will save its own arguments needed.
Each of the Parameter Server will save
Distribute Lookup Tablevariables in training.
Fluid Checkpoint directory structure：¶
checkpoint_dir (the checkpoint directory user define) ├── checkpoint_0 (the first save directory) │ ├── __lockup_table__ (Distribute Lookup Table directory) │ │ ├── table_pserver_0 (Lookup table's data about Pserver 0) │ │ └── table_pserver_1 │ ├── __model__ (model directory) │ │ └── var.w_1 │ └── trainer_0 (each trainer will save its own data) │ ├── epoch_id │ └── step_id └── checkpoint_1 (the second save directory)
When the user wants to use
Checkpoint feature, the main thing user have to do is declare
CheckpointConfig and construct it.
CheckpointConfig has 4 member variables need to be initialized：
|max_num_checkpoints||int||Maximum number of checkpoint copies|
|epoch_interval||int||epoch interval times|
|step_interval||int||step interval times|
Add Fluid.CheckpointConfig’s declaration in Fluid.Trainer¶
Because the initialization of Trainer needs an instance of
CheckpointConfig., we should declare
config = CheckpointConfig( checkpoint_dir = "/tmp/ckpt", max_num_checkpoints = 2, epoch_interval = 2, step_interval = 10) trainer = Trainer(..., checkpoint_config=config)
After all the things done, the train will save checkpoint at the specified epoch and step, when the train is aborted, the user can restart it, the train will restore from the latest copy.
checkpoint_dironly be used by one train job.
The number of
max_num_checkpointsneed to be adjusted by the disk size and model size.
Too frequently to slow down the train speed, so too
step_intervalare not suitable.
In distributed train, each Trainer will save arguments in its
checkpoint_dir(Only Trainer 0 will save model variables). We need distributed file system (HDFS, etc) to merge all the
checkpoint_dirto get the whole data.