在pytorch的DDP原生代码使用的基础上，ray和accelerate两个库对于pytorch并行训练的代码使用做了更加友好的封装。

以下为极简的代码示例。

ray

ray.py

#coding=utf-8
import os
import sys
import time
import numpy as np
import torch
from torch import nn
import torch.utils.data as Data
import ray
from ray.train.torch import TorchTrainer
from ray.air.config import ScalingConfig
import onnxruntime# bellow code use AI model to simulate linear regression, formula is: y = x1 * w1 + x2 * w2 + b
# --- DDP RAY --- # # model structure
class LinearNet(nn.Module):def __init__(self, n_feature):super(LinearNet, self).__init__()self.linear = nn.Linear(n_feature, 1)def forward(self, x):y = self.linear(x)return y# whole train task
def train_task():print("--- train_task, pid: ", os.getpid())# device settingdevice = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")print("device:", device)device_ids = torch._utils._get_all_device_indices()print("device_ids:", device_ids)if len(device_ids) <= 0:print("invalid device_ids, exit")return# prepare datanum_inputs = 2num_examples = 1000true_w = [2, -3.5]true_b = 3.7features = torch.tensor(np.random.normal(0, 1, (num_examples, num_inputs)), dtype=torch.float)labels = true_w[0] * features[:, 0] + true_w[1] * features[:, 1] + true_b + torch.tensor(np.random.normal(0, 0.01, size=num_examples), dtype=torch.float)# load databatch_size = 10dataset = Data.TensorDataset(features, labels)data_iter = Data.DataLoader(dataset, batch_size, shuffle=True)for X, y in data_iter:print(X, y)breakdata_iter = ray.train.torch.prepare_data_loader(data_iter)# model define and initmodel = LinearNet(num_inputs)ddp_model = ray.train.torch.prepare_model(model)print(ddp_model)# cost functionloss = nn.MSELoss()# optimizeroptimizer = torch.optim.SGD(ddp_model.parameters(), lr=0.03)# trainnum_epochs = 6for epoch in range(1, num_epochs + 1):batch_count = 0sum_loss = 0.0for X, y in data_iter:output = ddp_model(X)l = loss(output, y.view(-1, 1))optimizer.zero_grad()l.backward()optimizer.step()batch_count += 1sum_loss += l.item()print('epoch %d, avg_loss: %f' % (epoch, sum_loss / batch_count))# save modelprint("save model, pid: ", os.getpid())torch.save(ddp_model.module.state_dict(), "ddp_ray_model.pt")def ray_launch_task():num_workers = 2scaling_config = ScalingConfig(num_workers=num_workers, use_gpu=True)trainer = TorchTrainer(train_loop_per_worker=train_task, scaling_config=scaling_config)results = trainer.fit()def predict_task():print("--- predict_task")# prepare datanum_inputs = 2num_examples = 20true_w = [2, -3.5]true_b = 3.7features = torch.tensor(np.random.normal(0, 1, (num_examples, num_inputs)), dtype=torch.float)labels = true_w[0] * features[:, 0] + true_w[1] * features[:, 1] + true_b + torch.tensor(np.random.normal(0, 0.01, size=num_examples), dtype=torch.float)model = LinearNet(num_inputs)model.load_state_dict(torch.load("ddp_ray_model.pt"))model.eval()x, y = features[6], labels[6]pred_y = model(x)print("x:", x)print("y:", y)print("pred_y:", y)if __name__ == "__main__":print("==== task begin ====")print("python version:", sys.version)print("torch version:", torch.__version__)print("model name:", LinearNet.__name__)ray_launch_task()# predict_task()print("==== task end ====")

accelerate

acc.py

#coding=utf-8
import os
import sys
import time
import numpy as np
from accelerate import Accelerator
import torch
from torch import nn
import torch.utils.data as Data
import onnxruntime# bellow code use AI model to simulate linear regression, formula is: y = x1 * w1 + x2 * w2 + b
# --- accelerate --- # # model structure
class LinearNet(nn.Module):def __init__(self, n_feature):super(LinearNet, self).__init__()self.linear = nn.Linear(n_feature, 1)def forward(self, x):y = self.linear(x)return y# whole train task
def train_task():print("--- train_task, pid: ", os.getpid())# device settingdevice = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")print("device:", device)device_ids = torch._utils._get_all_device_indices()print("device_ids:", device_ids)if len(device_ids) <= 0:print("invalid device_ids, exit")return# prepare datanum_inputs = 2num_examples = 1000true_w = [2, -3.5]true_b = 3.7features = torch.tensor(np.random.normal(0, 1, (num_examples, num_inputs)), dtype=torch.float)labels = true_w[0] * features[:, 0] + true_w[1] * features[:, 1] + true_b + torch.tensor(np.random.normal(0, 0.01, size=num_examples), dtype=torch.float)# load databatch_size = 10dataset = Data.TensorDataset(features, labels)data_iter = Data.DataLoader(dataset, batch_size, shuffle=True)for X, y in data_iter:print(X, y)break# model define and initmodel = LinearNet(num_inputs)# cost functionloss = nn.MSELoss()# optimizeroptimizer = torch.optim.SGD(model.parameters(), lr=0.03)accelerator = Accelerator()model, optimizer, data_iter = accelerator.prepare(model, optimizer, data_iter) # automatically move model and data to gpu as config# trainnum_epochs = 3for epoch in range(1, num_epochs + 1):batch_count = 0sum_loss = 0.0for X, y in data_iter:output = model(X)l = loss(output, y.view(-1, 1))optimizer.zero_grad()accelerator.backward(l)optimizer.step()batch_count += 1sum_loss += l.item()print('epoch %d, avg_loss: %f' % (epoch, sum_loss / batch_count))# save modeltorch.save(model, "acc_model.pt")def predict_task():print("--- predict_task")# prepare datanum_inputs = 2num_examples = 20true_w = [2, -3.5]true_b = 3.7features = torch.tensor(np.random.normal(0, 1, (num_examples, num_inputs)), dtype=torch.float)labels = true_w[0] * features[:, 0] + true_w[1] * features[:, 1] + true_b + torch.tensor(np.random.normal(0, 0.01, size=num_examples), dtype=torch.float)model = torch.load("acc_model.pt")model.eval()x, y = features[6], labels[6]pred_y = model(x)print("x:", x)print("y:", y)print("pred_y:", y)if __name__ == "__main__":# launch method: use command line# for example# accelerate launch ACC.py print("python version:", sys.version)print("torch version:", torch.__version__)print("model name:", LinearNet.__name__)train_task()predict_task()print("==== task end ====")