ONNX Runtime Training Guidelines

1. Installation and Configuration

Be noted: this mainly demonstrates set up steps for development, check Torch-ORT for end user set up experience.

Refer https://onnxruntime.ai/ to download training wheel. Or build from source:

export CUDA_HOME=/usr/local/cuda
export CUDNN_HOME=/usr/local/cuda
export CUDACXX=$CUDA_HOME/bin/nvcc

./build.sh --config RelWithDebInfo --use_cuda --enable_training --build_wheel --skip_tests --cuda_version=11.8 --parallel 8 --use_mpi

Install the Python wheel.

Configure ORTModule torch cpp extensions (avoid doing this in ORT code repo root directory):

python -m onnxruntime.training.ortmodule.torch_cpp_extensions.install

2. Use `ORTModule` to Accelerate Forward/Backward

Plug in your torch.nn.Module model with ORTModule to leverage ONNX Runtime fast training backend.

Sample usage as below:

	model = build_model()

+	from onnxruntime.training.ortmodule import ORTModule
+	model = ORTModule(model)

It is strongly recommended to wrap model with ORTModule before other module wrapper (for example, DeepSpeed, torch.nn.parallel.DistributedDataParallel, etc), which is validated in more scenarios.

Be also noticed that, ORTModule is NOT compatible with torch.nn.DataParallel (not recommended to use in PyTorch usage). Please use torch.nn.parallel.DistributedDataParallel instead.

More options for developers.

	model = build_model()

+	from onnxruntime.training.ortmodule import ORTModule, DebugOptions, LogLevel
+	model = ORTModule(model, DebugOptions(save_onnx=True, log_level=LogLevel.VERBOSE, onnx_prefix="model_name"))

Check DebugOptions implementation for more details.

Log Level Explanations

Log Level	Description
`FATAL` \| `ERROR` \| `WARNING` (For Users) ^{WARNING is the default and recommended level for users.}	ONNX Runtime backend log level - `FATAL` \| `ERROR` \| `WARNING`. ORTModule log level - `FATAL` \| `ERROR` \| `WARNING`. Rank-0 log filtering is `ON` (e.g. logging on rank-0-only). PyTorch exporter export logs filtering is `ON`. PyTorch exporter verbose logs (including tracing graph) filtering is `ON`.
`INFO` (For Users \| ORT Developers) ^{INFO is used for collecting experimental feature stats, or a little bit more error messages.}	ONNX Runtime backend log level - `WARNING`. ORTModule log level - `INFO`. Rank-0 log filtering is `ON` (e.g. logging on rank-0-only). PyTorch exporter export logs filtering is `ON`. PyTorch exporter verbose logs (including tracing graph) filtering is `OFF`.
`DEVINFO` (For ORT Developers) ^{DEVINFO is the recommended level for debugging purposes.}	ONNX Runtime backend log level - `INFO`. ORTModule log level - `INFO`. Rank-0 log filtering is `OFF` (e.g. logging on all ranks). PyTorch exporter export logs filtering is `OFF`. PyTorch exporter verbose logs (including tracing graph) filtering is `OFF`.
`VERBOSE` (For ORT Developers) ^{VERBOSE is the last resort for debugging hard problems.}	ONNX Runtime backend log level - `VERBOSE`. ORTModule log level - `VERBOSE`. Rank-0 log filtering is `OFF` (e.g. logging on all ranks). PyTorch exporter export logs filtering is `OFF`. PyTorch exporter verbose logs (including tracing graph) filtering is `OFF`.

2.1 Environment Variables

ORTModule provides environment variables targeting different use cases.

ORTMODULE_ONNX_OPSET_VERSION

Feature Area: ORTMODULE/ONNXOPSET
Description: By default, as ONNX Runtime released, the ONNX OPSET version to use will be updated periodically. For some customers, they want to stick to fixed OPSET where both performance and accuracy are well validated, this env variable can be used to control that.
```
 export ORTMODULE_ONNX_OPSET_VERSION=14
```

ORTMODULE_FALLBACK_POLICY

Feature Area: ORTMODULE/FallbackToPytorch
Description: By default, if ORTModule fails to run the model using ONNX Runtime backend, it will fallback to use PyTorch to continue the training. At some point developers are optimizing the models and doing benchmarking, we want explicitly let ORT backend to run the model. The way we disable the retry:
```
 export ORTMODULE_FALLBACK_POLICY="FALLBACK_DISABLE"
```

ORTMODULE_LOG_LEVEL

Feature Area: ORTMODULE/DebugOptions
Description: Configure ORTModule log level. Defaults to LogLevel.WARNING, can be set one of "VERBOSE", "INFO", "WARNING", "ERROR", "FATAL". The environment variable takes precedence if DebugOptions also sets log_level.

ORTMODULE_SAVE_ONNX_PATH

Feature Area: ORTMODULE/DebugOptions
Description: Configure ORTModule to save onnx models. Defaults to False. The output directory of the onnx models by default is set to the current working directory. To change the output directory, the environment variable "ORTMODULE_SAVE_ONNX_PATH" can be set to the destination directory path.

ORTMODULE_ALLOW_AUTOGRAD_CHECKPOINT

Feature Area: ORTMODULE/PythonOp (torch.autograd.Function)
Description: By default ORTModule will fail with exception when handling PythonOp export for some 'autograd.Function's (One example is torch CheckpointFunction). Set this env variable to be 1 to explicitly allow it.
```
 export ORTMODULE_ALLOW_AUTOGRAD_CHECKPOINT=1
```
Take the example of torch.utils.checkpoint.CheckpointFunction, if it is exported as PythonOp, the checkpointed computation may be computed by PyTorch, not ORT. This situation is especially important for big models such as GPT-2 where every few layers are wrapped to do re-computation, large number of computations are done by PyTorch. Currently a failure is reported to notify users it is possible ORTModule has less opportunities to optimize further.

On the other hand, if the wrapped computation graph is small, it is reasonable to allow it. Overall users should be aware that ORT performance boost might be trivial when they explicitly allow it.

ORTMODULE_ENABLE_CUSTOM_AUTOGRAD

Feature Area: ORTMODULE/PythonOp (torch.autograd.Function)
Description: By default, all torch.autograd.Function classes will be exported to ORT PythonOp. There are some cases where you might consider disable it. For example, if you confirmed those torch.autograd.Function classes defined computations that could be inline exported by PyTorch, and it is safe to use the inline exported ONNX graph to train, then you can disable it, as a result, ORT has more opportunities to optimize more.
```
 export ORTMODULE_ENABLE_CUSTOM_AUTOGRAD=1 # Enable
 export ORTMODULE_ENABLE_CUSTOM_AUTOGRAD=0 # Disable
```
An alternative to disable without using environment variable:
```
 from onnxruntime.training.ortmodule._custom_autograd_function import enable_custom_autograd_support
 enable_custom_autograd_support(False)
```

ORTMODULE_ENABLE_COMPUTE_OPTIMIZER

Feature Area: ORTMODULE/Optimizations
Description: By default, this is enabled then some computation can be saved. This env var can be used for disabling the optimization to guarantee exactly same compute with baseline (for example PyTorch, when doing convergence parity debugging).
```
 export ORTMODULE_ENABLE_COMPUTE_OPTIMIZER=1 # Enable
 export ORTMODULE_ENABLE_COMPUTE_OPTIMIZER=0 # Disable
```

ORTMODULE_PRINT_INPUT_DENSITY

Feature Area: ORTMODULE/RuntimeInspector
Description: By default, this is disabled. This env var can be used for printing the input data sparsity inspection results to standard outputs.
```
 export ORTMODULE_PRINT_INPUT_DENSITY=1 # Enable
 export ORTMODULE_PRINT_INPUT_DENSITY=0 # Disable
```

ORTMODULE_PRINT_MEMORY_STATS

Feature Area: ORTMODULE/RuntimeInspector
Description: By default, this is disabled. This env var can be used for printing the memory inspection results to standard outputs.
```
 export ORTMODULE_PRINT_MEMORY_STATS=1 # Enable
 export ORTMODULE_PRINT_MEMORY_STATS=0 # Disable
```

ORTMODULE_ENABLE_EMBEDDING_SPARSE_OPTIMIZER

Feature Area: ORTMODULE/Optimizations
Description: By default, this is enabled. This env var can be used for enabling or disabling the embedding input data sparsity based performance optimizations.
```
 export ORTMODULE_ENABLE_EMBEDDING_SPARSE_OPTIMIZER=1 # Enable
 export ORTMODULE_ENABLE_EMBEDDING_SPARSE_OPTIMIZER=0 # Disable
```

ORTMODULE_ENABLE_LABEL_SPARSE_OPTIMIZER

Feature Area: ORTMODULE/Optimizations
Description: By default, this is enabled. This env var can be used for enabling or disabling the label input data sparsity based performance optimizations.
```
 export ORTMODULE_ENABLE_LABEL_SPARSE_OPTIMIZER=1 # Enable
 export ORTMODULE_ENABLE_LABEL_SPARSE_OPTIMIZER=0 # Disable
```

ORTMODULE_CACHE_DIR

Feature Area: ORTMODULE/RuntimeOptions
Description: By default, this is disabled. This env vars can be used to cache the exported model for future runs. This optimization is intended to reduce experimentation time by re-using the PyTorch->ONNX exported model architecture when available.
```
 export ORTMODULE_CACHE_DIR="/path/to/cache_dir" # Enable
 unset ORTMODULE_CACHE_DIR # Disable
```

ORTMODULE_USE_EFFICIENT_ATTENTION

Feature Area: ORTMODULE/Optimizations
Description: By default, this is disabled. This env var can be used for enabling attention fusion and falling back to PyTorch's efficient_attention ATen kernel for execution. NOTE that it requires torch's version is 2.1.1 or above. There are some build-in patterns for attention fusion, if none of the patterns works for your model, you can add a custom one in your user script manually.
```
export ORTMODULE_USE_EFFICIENT_ATTENTION=1
```

ORTMODULE_DEEPCOPY_BEFORE_MODEL_EXPORT

Feature Area: ORTMODULE/Optimizations
Description: By default, this is enabled. This env var can be used for enabling or disabling the module deep copy when preparing output data which will be used by ONNX export. A classical usage of disabling the deep copy: when the deep copy before module export bring the memory peak, then we should disable it and have a try.
```
 export ORTMODULE_DEEPCOPY_BEFORE_MODEL_EXPORT=1 # Enable
 export ORTMODULE_DEEPCOPY_BEFORE_MODEL_EXPORT=0 # Disable
```

ORTMODULE_MEMORY_OPT_LEVEL

Feature Area: ORTMODULE/Optimizations
Description: By default, the level is 0. This env var can be used for enabling recomputation for reducing memory peak requirement.
- Setting the level to be 1 means all detected recomputable subgraphs (NOT including compromised recomputable graphs) with each transformer-based model layer generating stashed activations will be recomputed. This is conceptually equivalent to PyTorch's gradient checkpoint.
- Setting the level to be 2 means all detected recomputable subgraphs (including compromised recomputable graphs) with each transformer-based model layer generating stashed activations will be recomputed. This is conceptually equivalent to PyTorch's gradient checkpoint.
- When the level is 0, check Check Memory Optimizer for ONNX Runtime Training for more details.
```
export ORTMODULE_MEMORY_OPT_LEVEL=0
```

ORTMODULE_ENABLE_MEM_EFFICIENT_GRAD_MGMT

Feature Area: ORTMODULE/Optimizations
Description: By default, the memory-efficient gradient management is turned off. The gradient after it is computed in ONNX Runtime, will trigger the corresponding parameter's backward function through PythonOpGrad operator. This would help release the gradient buffer managed in ONNX Runtime, which originally is released once all backward computation finishes.
```
 export ORTMODULE_ENABLE_MEM_EFFICIENT_GRAD_MGMT=1 # Enable
 export ORTMODULE_ENABLE_MEM_EFFICIENT_GRAD_MGMT=0 # Disable
```

2.2 Memory Optimization

Q: Want to run a bigger batch size?

Q: The model training hits OOM, even with minimum required batch size?

Check Memory Optimizer for ONNX Runtime Training for how to leverage ORT's recomputation techniques.

3. Use `FusedAdam` to Accelerate Parameter Update

Parameter update is done by optimizers (for example AdamW) with many elementwise operations. FusedAdam launches the elementwise update kernels with multi-tensor apply, allowing batches of gradients applied to corresponding parameters for each time kernel launch.

Here is a sample switch from torch AdamW optimizer to FusedAdam.

	model = build_model()

-	optimizer = AdamW(model.parameters(), lr=1)
+	from onnxruntime.training.optim import FusedAdam
+	optimizer = FusedAdam(model.parameters(), lr=1)

Check FusedAdam implementation for more details.

4. Use `FP16_Optimizer` to Complement DeepSpeed/APEX

If user models utilize DeepSpeed or Apex libraries, ORT's FP16_Optimizer can be used to complement some inefficiencies introduced by them.

Use FP16_Optimizer with DeepSpeed ZeRO Optimizer:

	optimizer = AdamW(model.parameters(), lr=1)
	model, optimizer, _, lr_scheduler = deepspeed.initialize(
			model=model,
			optimizer=optimizer,
			args=args,
			lr_scheduler=lr_scheduler,
			mpu=mpu,
			dist_init_required=False)

+	from onnxruntime.training.optim.fp16_optimizer import FP16_Optimizer
+	optimizer = FP16_Optimizer(optimizer)

Use FP16_Optimizer with Apex Optimizer:

	optimizer = torch.optim.SGD(model.parameters(), lr=1e-3)
	model, optimizer = amp.initialize(model, optimizer, opt_level="O2")

+	from onnxruntime.training.optim.fp16_optimizer import FP16_Optimizer as ORT_FP16_Optimizer
+	optimizer = ORT_FP16_Optimizer(optimizer)

Check FP16_Optimizer implementation for more details.

5. Putting All Together `ORTModule` + `FusedAdam` + `FP16_Optimizer`

	model = build_model()

+	from onnxruntime.training.ortmodule import ORTModule
+	model = ORTModule(model)

-	optimizer = AdamW(model.parameters(), lr=1)
+	from onnxruntime.training.optim import FusedAdam
+	optimizer = FusedAdam(model.parameters(), lr=1)

	model, optimizer, _, lr_scheduler = deepspeed.initialize(
			model=model,
			optimizer=optimizer,
			args=args,
			lr_scheduler=lr_scheduler,
			mpu=mpu,
			dist_init_required=False)

+	from onnxruntime.training.optim.fp16_optimizer import FP16_Optimizer
+	optimizer = FP16_Optimizer(optimizer)

6. Use OpenAI Triton to Compute ONNX Sub-graph

ORTModule provides a way to switch to OpenAI Triton for executing some Ops to further accelerate training.

6.1 Environment Variables

ORTMODULE_USE_TRITON

Feature Area: ORTMODULE/TritonOp
Description: By default, this is disabled. This env var can be used for enabling Triton optimization.
```
export ORTMODULE_USE_TRITON=1
```

ORTMODULE_TRITON_CONFIG_FILE

Feature Area: ORTMODULE/TritonOp
Description: Triton codegen currently supported some Ops such as some elementwise Ops and some reduction Ops. If Triton optimization is enabled, all these supported Ops will be optimized by default if possible. User can provide a customized JSON config file to control which Ops to optimize and how to optimize them. Below is a sample of config JSON. For each Op, Opset version list and domain is needed. Currently "conditions" field can be used to control axis/axes attribute or input, by specify the real value, or "single" means it contains only one dimension, or "constant" means it must be constant tensor. Save the JSON as a file somewhere and assign its path to below env variable to enable the customized config.
```
{
	"ops": {
		"Add": {"versions": [13, 14]},
		"Sub": {"versions": [13, 14]},
		"Identity": {"versions": [13], "is_no_op": True},
		"ReduceSum": {"versions": [13], "conditions": {"axes": "[-1]"}},
		"Softmax": {"versions": [13]},
		"SoftmaxGrad_13": {"domain": "com.microsoft", "versions": [1]}
	},
	"initializer": "scalar",
	"min_nodes": 2
}
```
```
export ORTMODULE_TRITON_CONFIG_FILE=triton_config.json
```

ORTMODULE_ENABLE_TUNING

Feature Area: ORTMODULE/TritonOp
Description: By default, this is disabled. This env var can be used for enabling online Op tuning for those Ops that have multiple implementations on target EP.
```
export ORTMODULE_ENABLE_TUNING=1
```

ORTMODULE_MAX_TUNING_DURATION_MS

Feature Area: ORTMODULE/TritonOp
Description: When ORTMODULE_ENABLE_TUNING is enabled, this env var can be used to set max tuning duration in ms to avoid long tuning time.
```
export ORTMODULE_MAX_TUNING_DURATION_MS=9999
```

ORTMODULE_TUNING_RESULTS_PATH

Feature Area: ORTMODULE/TritonOp
Description: When ORTMODULE_ENABLE_TUNING is enabled, this env var can be used to specify where the online Op tuning results be saved for later use. By default the results will not be saved. When ORTMODULE_ENABLE_TUNING is NOT enabled, this env var can be used to specify where Op tuning results can be fetched as offline tuning results.
```
export ORTMODULE_TUNING_RESULTS_PATH=/tmp/tuning_results
```

ORTMODULE_USE_FLASH_ATTENTION

Feature Area: ORTMODULE/TritonOp
Description: By default, this is disabled. This env var can be used for enabling attention fusion and using Flash Attention's Triton version as the kernel. NOTE that it requires ORTMODULE_USE_TRITON to be enabled, and CUDA device capability is 8.0 or above. There are some build-in patterns for attention fusion, if none of the patterns works for your model, you can add a custom one in your user script manually.
```
export ORTMODULE_USE_FLASH_ATTENTION=1
```

ORTMODULE_TRITON_DEBUG

Feature Area: ORTMODULE/TritonOp
Description: By default, this is disabled. This env var can be used for enabling Triton debug mode. All original and processed sub-graphs and corresponding generated Triton codes will be saved into a triton_debug folder under working directory.
```
export ORTMODULE_TRITON_DEBUG=1
```

7. One More Thing - `LoadBalancingDistributedBatchSampler`

LoadBalancingDistributedBatchSampler balances the data load across workers based on the sample's complexity. This is useful in scenarios like speech and NLP, where each batch has variable length and distributed training suffers from straggler problem. In such scenarios, the complexity function could be defined to return the length of the input sample sequence. The usage is similar to torch.utils.data.DistributedSampler, where each process loads a subset of the original dataset that is exclusive to it.

A sample shown below:

from onnxruntime.training.utils.data import LoadBalancingDistributedSampler, \
    LoadBalancingDistributedBatchSampler
sampler = LoadBalancingDistributedSampler(dataset, complexity_fn=complexity_fn)
batch_sampler = LoadBalancingDistributedBatchSampler(sampler, batch_fn=batch_fn)
loader = torch.utils.data.DataLoader(dataset, batch_sampler=batch_sampler)
for epoch in range(start_epoch, n_epochs):
    batch_sampler.set_epoch(epoch)
    train(loader)

Check LoadBalancingDistributedBatchSampler implementation for more details.

8 Using ORTPipelineModule for Deepspeed Pipeline Parallel

You can use ORTPipelineModule to support Deepspeed Pipeline Parallelism. Here's how you can integrate it into your pipeline:

from onnxruntime.training.ortmodule import DebugOptions
from onnxruntime.training.ortmodule.experimental.pipe import ORTPipelineModule

# Create a debug configuration if needed
# Since we're exporting multiple graphs here, this will generate multiple graphs with their index added as a prefix to differentiate them.

debug_options = DebugOptions(save_onnx=True, log_level=LogLevel.VERBOSE, onnx_prefix="model_name")

# Keep your deepspeed script the same and use ORTPipelineModule instead of PipelineModule
# Initialize the ORTPipelineModule
pipeline_module = ORTPipelineModule(
    layers,
    num_stages=2,  # Set your number of stages
    base_seed=1234,
    partition_method="parameters",
    debug_options=debug_options  # Pass the debug configuration if needed
)

# Keep the rest of the script as it is.

Check ORTPipelineModule implementation for more details.

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ORTModule_Training_Guidelines.md

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