/distributed-training-accelerate

name: huggingface-accelerate
description: Simplest distributed training API. 4 lines to add distributed support to any PyTorch script. Unified API for DeepSpeed/FSDP/Megatron/DDP. Automatic device placement, mixed precision (FP16/BF16/FP8). Interactive config, single launch command. HuggingFace ecosystem standard.
version: 1.0.0
author: Orchestra Research
license: MIT
tags: [Distributed Training, HuggingFace, Accelerate, DeepSpeed, FSDP, Mixed Precision, PyTorch, DDP, Unified API, Simple]
dependencies: [accelerate, torch, transformers]

HuggingFace Accelerate - Unified Distributed Training

Quick start

Accelerate simplifies distributed training to 4 lines of code.

**Installation**:

pip install accelerate

**Convert PyTorch script** (4 lines):

import torch
+ from accelerate import Accelerator

+ accelerator = Accelerator()

  model = torch.nn.Transformer()
  optimizer = torch.optim.Adam(model.parameters())
  dataloader = torch.utils.data.DataLoader(dataset)

+ model, optimizer, dataloader = accelerator.prepare(model, optimizer, dataloader)

  for batch in dataloader:
      optimizer.zero_grad()
      loss = model(batch)
-     loss.backward()
+     accelerator.backward(loss)
      optimizer.step()

**Run** (single command):

accelerate launch train.py

Common workflows

Workflow 1: From single GPU to multi-GPU

**Original script**:

# train.py
import torch

model = torch.nn.Linear(10, 2).to('cuda')
optimizer = torch.optim.Adam(model.parameters())
dataloader = torch.utils.data.DataLoader(dataset, batch_size=32)

for epoch in range(10):
    for batch in dataloader:
        batch = batch.to('cuda')
        optimizer.zero_grad()
        loss = model(batch).mean()
        loss.backward()
        optimizer.step()

**With Accelerate** (4 lines added):

# train.py
import torch
from accelerate import Accelerator  # +1

accelerator = Accelerator()  # +2

model = torch.nn.Linear(10, 2)
optimizer = torch.optim.Adam(model.parameters())
dataloader = torch.utils.data.DataLoader(dataset, batch_size=32)

model, optimizer, dataloader = accelerator.prepare(model, optimizer, dataloader)  # +3

for epoch in range(10):
    for batch in dataloader:
        # No .to('cuda') needed - automatic!
        optimizer.zero_grad()
        loss = model(batch).mean()
        accelerator.backward(loss)  # +4
        optimizer.step()

**Configure** (interactive):

accelerate config

**Questions**:

• Which machine? (single/multi GPU/TPU/CPU)
• How many machines? (1)
• Mixed precision? (no/fp16/bf16/fp8)
• DeepSpeed? (no/yes)

**Launch** (works on any setup):

# Single GPU
accelerate launch train.py

# Multi-GPU (8 GPUs)
accelerate launch --multi_gpu --num_processes 8 train.py

# Multi-node
accelerate launch --multi_gpu --num_processes 16 \
  --num_machines 2 --machine_rank 0 \
  --main_process_ip $MASTER_ADDR \
  train.py

Workflow 2: Mixed precision training

**Enable FP16/BF16**:

from accelerate import Accelerator

# FP16 (with gradient scaling)
accelerator = Accelerator(mixed_precision='fp16')

# BF16 (no scaling, more stable)
accelerator = Accelerator(mixed_precision='bf16')

# FP8 (H100+)
accelerator = Accelerator(mixed_precision='fp8')

model, optimizer, dataloader = accelerator.prepare(model, optimizer, dataloader)

# Everything else is automatic!
for batch in dataloader:
    with accelerator.autocast():  # Optional, done automatically
        loss = model(batch)
    accelerator.backward(loss)

Workflow 3: DeepSpeed ZeRO integration

**Enable DeepSpeed ZeRO-2**:

from accelerate import Accelerator

accelerator = Accelerator(
    mixed_precision='bf16',
    deepspeed_plugin={
        "zero_stage": 2,  # ZeRO-2
        "offload_optimizer": False,
        "gradient_accumulation_steps": 4
    }
)

# Same code as before!
model, optimizer, dataloader = accelerator.prepare(model, optimizer, dataloader)

**Or via config**:

accelerate config
# Select: DeepSpeed → ZeRO-2

**deepspeed_config.json**:

{
    "fp16": {"enabled": false},
    "bf16": {"enabled": true},
    "zero_optimization": {
        "stage": 2,
        "offload_optimizer": {"device": "cpu"},
        "allgather_bucket_size": 5e8,
        "reduce_bucket_size": 5e8
    }
}

**Launch**:

accelerate launch --config_file deepspeed_config.json train.py

Workflow 4: FSDP (Fully Sharded Data Parallel)

**Enable FSDP**:

from accelerate import Accelerator, FullyShardedDataParallelPlugin

fsdp_plugin = FullyShardedDataParallelPlugin(
    sharding_strategy="FULL_SHARD",  # ZeRO-3 equivalent
    auto_wrap_policy="TRANSFORMER_AUTO_WRAP",
    cpu_offload=False
)

accelerator = Accelerator(
    mixed_precision='bf16',
    fsdp_plugin=fsdp_plugin
)

model, optimizer, dataloader = accelerator.prepare(model, optimizer, dataloader)

**Or via config**:

accelerate config
# Select: FSDP → Full Shard → No CPU Offload

Workflow 5: Gradient accumulation

**Accumulate gradients**:

from accelerate import Accelerator

accelerator = Accelerator(gradient_accumulation_steps=4)

model, optimizer, dataloader = accelerator.prepare(model, optimizer, dataloader)

for batch in dataloader:
    with accelerator.accumulate(model):  # Handles accumulation
        optimizer.zero_grad()
        loss = model(batch)
        accelerator.backward(loss)
        optimizer.step()

**Effective batch size**: `batch_size * num_gpus * gradient_accumulation_steps`

When to use vs alternatives

**Use Accelerate when**:

• Want simplest distributed training
• Need single script for any hardware
• Use HuggingFace ecosystem
• Want flexibility (DDP/DeepSpeed/FSDP/Megatron)
• Need quick prototyping

**Key advantages**:

• **4 lines**: Minimal code changes
• **Unified API**: Same code for DDP, DeepSpeed, FSDP, Megatron
• **Automatic**: Device placement, mixed precision, sharding
• **Interactive config**: N