[Perf] Add a CPU-based training workload (#2116)

ray-operator/config/samples/pytorch-mnist/ray-job.pytorch-mnist.yaml

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+apiVersion: ray.io/v1
+kind: RayJob
+metadata:
+  name: rayjob-pytorch-mnist
+spec:
+  shutdownAfterJobFinishes: false
+  entrypoint: python ray-operator/config/samples/pytorch-mnist/ray_train_pytorch_mnist.py
+  runtimeEnvYAML: |
+    pip:
+      - torch
+      - torchvision
+    working_dir: "https://github.com/ray-project/kuberay/archive/master.zip"
+
+  # rayClusterSpec specifies the RayCluster instance to be created by the RayJob controller.
+  rayClusterSpec:
+    rayVersion: '2.9.0'
+    headGroupSpec:
+      rayStartParams: {}
+      # Pod template
+      template:
+        spec:
+          containers:
+            - name: ray-head
+              image: rayproject/ray:2.9.0
+              ports:
+                - containerPort: 6379
+                  name: gcs-server
+                - containerPort: 8265 # Ray dashboard
+                  name: dashboard
+                - containerPort: 10001
+                  name: client
+              resources:
+                limits:
+                  cpu: "2"
+                  memory: "4Gi"
+                requests:
+                  cpu: "2"
+                  memory: "4Gi"
+    workerGroupSpecs:
+      - replicas: 4
+        minReplicas: 1
+        maxReplicas: 5
+        groupName: small-group
+        rayStartParams: {}
+        # Pod template
+        template:
+          spec:
+            containers:
+              - name: ray-worker
+                image: rayproject/ray:2.9.0
+                resources:
+                  limits:
+                    cpu: "2"
+                    memory: "4Gi"
+                  requests:
+                    cpu: "2"
+                    memory: "4Gi"

ray-operator/config/samples/pytorch-mnist/ray_train_pytorch_mnist.py

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+"""
+Reference: https://docs.ray.io/en/master/train/examples/pytorch/torch_fashion_mnist_example.html
+
+This script is a modified version of the original PyTorch Fashion MNIST
+example. It uses only CPU resources to train the MNIST model. See
+`ScalingConfig` for more details.
+"""
+import os
+from typing import Dict
+
+import torch
+from filelock import FileLock
+from torch import nn
+from torch.utils.data import DataLoader
+from torchvision import datasets, transforms
+from torchvision.transforms import Normalize, ToTensor
+from tqdm import tqdm
+
+import ray.train
+from ray.train import ScalingConfig
+from ray.train.torch import TorchTrainer
+
+
+def get_dataloaders(batch_size):
+    # Transform to normalize the input images
+    transform = transforms.Compose([ToTensor(), Normalize((0.5,), (0.5,))])
+
+    with FileLock(os.path.expanduser("~/data.lock")):
+        # Download training data from open datasets
+        training_data = datasets.FashionMNIST(
+            root="~/data",
+            train=True,
+            download=True,
+            transform=transform,
+        )
+
+        # Download test data from open datasets
+        test_data = datasets.FashionMNIST(
+            root="~/data",
+            train=False,
+            download=True,
+            transform=transform,
+        )
+
+    # Create data loaders
+    train_dataloader = DataLoader(training_data, batch_size=batch_size, shuffle=True)
+    test_dataloader = DataLoader(test_data, batch_size=batch_size)
+
+    return train_dataloader, test_dataloader
+
+
+# Model Definition
+class NeuralNetwork(nn.Module):
+    def __init__(self):
+        super(NeuralNetwork, self).__init__()
+        self.flatten = nn.Flatten()
+        self.linear_relu_stack = nn.Sequential(
+            nn.Linear(28 * 28, 512),
+            nn.ReLU(),
+            nn.Dropout(0.25),
+            nn.Linear(512, 512),
+            nn.ReLU(),
+            nn.Dropout(0.25),
+            nn.Linear(512, 10),
+            nn.ReLU(),
+        )
+
+    def forward(self, x):
+        x = self.flatten(x)
+        logits = self.linear_relu_stack(x)
+        return logits
+
+
+def train_func_per_worker(config: Dict):
+    lr = config["lr"]
+    epochs = config["epochs"]
+    batch_size = config["batch_size_per_worker"]
+
+    # Get dataloaders inside the worker training function
+    train_dataloader, test_dataloader = get_dataloaders(batch_size=batch_size)
+
+    # [1] Prepare Dataloader for distributed training
+    # Shard the datasets among workers and move batches to the correct device
+    # =======================================================================
+    train_dataloader = ray.train.torch.prepare_data_loader(train_dataloader)
+    test_dataloader = ray.train.torch.prepare_data_loader(test_dataloader)
+
+    model = NeuralNetwork()
+
+    # [2] Prepare and wrap your model with DistributedDataParallel
+    # Move the model to the correct GPU/CPU device
+    # ============================================================
+    model = ray.train.torch.prepare_model(model)
+
+    loss_fn = nn.CrossEntropyLoss()
+    optimizer = torch.optim.SGD(model.parameters(), lr=lr, momentum=0.9)
+
+    # Model training loop
+    for epoch in range(epochs):
+        if ray.train.get_context().get_world_size() > 1:
+            # Required for the distributed sampler to shuffle properly across epochs.
+            train_dataloader.sampler.set_epoch(epoch)
+
+        model.train()
+        for X, y in tqdm(train_dataloader, desc=f"Train Epoch {epoch}"):
+            pred = model(X)
+            loss = loss_fn(pred, y)
+
+            optimizer.zero_grad()
+            loss.backward()
+            optimizer.step()
+
+        model.eval()
+        test_loss, num_correct, num_total = 0, 0, 0
+        with torch.no_grad():
+            for X, y in tqdm(test_dataloader, desc=f"Test Epoch {epoch}"):
+                pred = model(X)
+                loss = loss_fn(pred, y)
+
+                test_loss += loss.item()
+                num_total += y.shape[0]
+                num_correct += (pred.argmax(1) == y).sum().item()
+
+        test_loss /= len(test_dataloader)
+        accuracy = num_correct / num_total
+
+        # [3] Report metrics to Ray Train
+        # ===============================
+        ray.train.report(metrics={"loss": test_loss, "accuracy": accuracy})
+
+
+def train_fashion_mnist(num_workers=2, use_gpu=False):
+    global_batch_size = 32
+
+    train_config = {
+        "lr": 1e-3,
+        "epochs": 10,
+        "batch_size_per_worker": global_batch_size // num_workers,
+    }
+
+    # Configure computation resources
+    scaling_config = ScalingConfig(
+        num_workers=num_workers,
+        use_gpu=use_gpu,
+        resources_per_worker={"CPU": 2}
+    )
+
+    # Initialize a Ray TorchTrainer
+    trainer = TorchTrainer(
+        train_loop_per_worker=train_func_per_worker,
+        train_loop_config=train_config,
+        scaling_config=scaling_config,
+    )
+
+    # [4] Start distributed training
+    # Run `train_func_per_worker` on all workers
+    # =============================================
+    result = trainer.fit()
+    print(f"Training result: {result}")
+
+
+if __name__ == "__main__":
+    train_fashion_mnist(num_workers=4)