tensorboard

TensorBoard：机器学习可视化工具包

何时使用本技能

在以下情况使用 TensorBoard：

• 可视化训练指标，如随时间变化的损失和准确率
• 调试模型，借助直方图和分布
• 比较实验，跨多次运行
• 可视化模型图和架构
• 投影嵌入到更低维度（t-SNE、PCA）
• 追踪超参数实验
• 分析性能并识别瓶颈
• 可视化图像和文本在训练过程中

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安装

# Install TensorBoard
pip install tensorboard

# PyTorch integration
pip install torch torchvision tensorboard

# TensorFlow integration (TensorBoard included)
pip install tensorflow

# Launch TensorBoard
tensorboard --logdir=runs
# Access at http://localhost:6006

快速开始

PyTorch

from torch.utils.tensorboard import SummaryWriter

# Create writer
writer = SummaryWriter('runs/experiment_1')

# Training loop
for epoch in range(10):
    train_loss = train_epoch()
    val_acc = validate()

    # Log metrics
    writer.add_scalar('Loss/train', train_loss, epoch)
    writer.add_scalar('Accuracy/val', val_acc, epoch)

# Close writer
writer.close()

# Launch: tensorboard --logdir=runs

TensorFlow/Keras

import tensorflow as tf

# Create callback
tensorboard_callback = tf.keras.callbacks.TensorBoard(
    log_dir='logs/fit',
    histogram_freq=1
)

# Train model
model.fit(
    x_train, y_train,
    epochs=10,
    validation_data=(x_val, y_val),
    callbacks=[tensorboard_callback]
)

# Launch: tensorboard --logdir=logs

核心概念

1. SummaryWriter（PyTorch）

from torch.utils.tensorboard import SummaryWriter

# Default directory: runs/CURRENT_DATETIME
writer = SummaryWriter()

# Custom directory
writer = SummaryWriter('runs/experiment_1')

# Custom comment (appended to default directory)
writer = SummaryWriter(comment='baseline')

# Log data
writer.add_scalar('Loss/train', 0.5, step=0)
writer.add_scalar('Loss/train', 0.3, step=1)

# Flush and close
writer.flush()
writer.close()

2. 记录标量

# PyTorch
from torch.utils.tensorboard import SummaryWriter
writer = SummaryWriter()

for epoch in range(100):
    train_loss = train()
    val_loss = validate()

    # Log individual metrics
    writer.add_scalar('Loss/train', train_loss, epoch)
    writer.add_scalar('Loss/val', val_loss, epoch)
    writer.add_scalar('Accuracy/train', train_acc, epoch)
    writer.add_scalar('Accuracy/val', val_acc, epoch)

    # Learning rate
    lr = optimizer.param_groups[0]['lr']
    writer.add_scalar('Learning_rate', lr, epoch)

writer.close()

# TensorFlow
import tensorflow as tf

train_summary_writer = tf.summary.create_file_writer('logs/train')
val_summary_writer = tf.summary.create_file_writer('logs/val')

for epoch in range(100):
    with train_summary_writer.as_default():
        tf.summary.scalar('loss', train_loss, step=epoch)
        tf.summary.scalar('accuracy', train_acc, step=epoch)

    with val_summary_writer.as_default():
        tf.summary.scalar('loss', val_loss, step=epoch)
        tf.summary.scalar('accuracy', val_acc, step=epoch)

3. 记录多个标量

# PyTorch: Group related metrics
writer.add_scalars('Loss', {
    'train': train_loss,
    'validation': val_loss,
    'test': test_loss
}, epoch)

writer.add_scalars('Metrics', {
    'accuracy': accuracy,
    'precision': precision,
    'recall': recall,
    'f1': f1_score
}, epoch)

4. 记录图像

# PyTorch
import torch
from torchvision.utils import make_grid

# Single image
writer.add_image('Input/sample', img_tensor, epoch)

# Multiple images as grid
img_grid = make_grid(images[:64], nrow=8)
writer.add_image('Batch/inputs', img_grid, epoch)

# Predictions visualization
pred_grid = make_grid(predictions[:16], nrow=4)
writer.add_image('Predictions', pred_grid, epoch)

# TensorFlow
import tensorflow as tf

with file_writer.as_default():
    # Encode images as PNG
    tf.summary.image('Training samples', images, step=epoch, max_outputs=25)

5. 记录直方图

# PyTorch: Track weight distributions
for name, param in model.named_parameters():
    writer.add_histogram(name, param, epoch)

    # Track gradients
    if param.grad is not None:
        writer.add_histogram(f'{name}.grad', param.grad, epoch)

# Track activations
writer.add_histogram('Activations/relu1', activations, epoch)

# TensorFlow
with file_writer.as_default():
    tf.summary.histogram('weights/layer1', layer1.kernel, step=epoch)
    tf.summary.histogram('activations/relu1', activations, step=epoch)

6. 记录模型图

# PyTorch
import torch

model = MyModel()
dummy_input = torch.randn(1, 3, 224, 224)

writer.add_graph(model, dummy_input)
writer.close()

# TensorFlow (automatic with Keras)
tensorboard_callback = tf.keras.callbacks.TensorBoard(
    log_dir='logs',
    write_graph=True
)

model.fit(x, y, callbacks=[tensorboard_callback])

高级功能

嵌入投影器

在 2D/3D 中可视化高维数据（嵌入、特征）。

import torch
from torch.utils.tensorboard import SummaryWriter

# Get embeddings (e.g., word embeddings, image features)
embeddings = model.get_embeddings(data)  # Shape: (N, embedding_dim)

# Metadata (labels for each point)
metadata = ['class_1', 'class_2', 'class_1', ...]

# Images (optional, for image embeddings)
label_images = torch.stack([img1, img2, img3, ...])

# Log to TensorBoard
writer.add_embedding(
    embeddings,
    metadata=metadata,
    label_img=label_images,
    global_step=epoch
)

在 TensorBoard 中：

• 导航到 "Projector" 标签页
• 选择 PCA、t-SNE 或 UMAP 可视化
• 搜索、筛选并探索聚类

超参数调优

from torch.utils.tensorboard import SummaryWriter

# Try different hyperparameters
for lr in [0.001, 0.01, 0.1]:
    for batch_size in [16, 32, 64]:
        # Create unique run directory
        writer = SummaryWriter(f'runs/lr{lr}_bs{batch_size}')

        # Log hyperparameters
        writer.add_hparams(
            {'lr': lr, 'batch_size': batch_size},
            {'hparam/accuracy': final_acc, 'hparam/loss': final_loss}
        )

        # Train and log
        for epoch in range(10):
            loss = train(lr, batch_size)
            writer.add_scalar('Loss/train', loss, epoch)

        writer.close()

# Compare in TensorBoard's "HParams" tab

文本记录

# PyTorch: Log text (e.g., model predictions, summaries)
writer.add_text('Predictions', f'Epoch {epoch}: {predictions}', epoch)
writer.add_text('Config', str(config), 0)

# Log markdown tables
markdown_table = """
| Metric | Value |
|--------|-------|
| Accuracy | 0.95 |
| F1 Score | 0.93 |
"""
writer.add_text('Results', markdown_table, epoch)

PR 曲线

用于分类的精确率-召回率曲线。

from torch.utils.tensorboard import SummaryWriter

# Get predictions and labels
predictions = model(test_data)  # Shape: (N, num_classes)
labels = test_labels  # Shape: (N,)

# Log PR curve for each class
for i in range(num_classes):
    writer.add_pr_curve(
        f'PR_curve/class_{i}',
        labels == i,
        predictions[:, i],
        global_step=epoch
    )

集成示例

PyTorch 训练循环

import torch
import torch.nn as nn
from torch.utils.tensorboard import SummaryWriter

# Setup
writer = SummaryWriter('runs/resnet_experiment')
model = ResNet50()
optimizer = torch.optim.Adam(model.parameters(), lr=0.001)
criterion = nn.CrossEntropyLoss()

# Log model graph
dummy_input = torch.randn(1, 3, 224, 224)
writer.add_graph(model, dummy_input)

# Training loop
for epoch in range(50):
    model.train()
    train_loss = 0.0
    train_correct = 0

    for batch_idx, (data, target) in enumerate(train_loader):
        optimizer.zero_grad()
        output = model(data)
        loss = criterion(output, target)
        loss.backward()
        optimizer.step()

        train_loss += loss.item()
        pred = output.argmax(dim=1)
        train_correct += pred.eq(target).sum().item()

        # Log batch metrics (every 100 batches)
        if batch_idx % 100 == 0:
            global_step = epoch * len(train_loader) + batch_idx
            writer.add_scalar('Loss/train_batch', loss.item(), global_step)

    # Epoch metrics
    train_loss /= len(train_loader)
    train_acc = train_correct / len(train_loader.dataset)

    # Validation
    model.eval()
    val_loss = 0.0
    val_correct = 0

    with torch.no_grad():
        for data, target in val_loader:
            output = model(data)
            val_loss += criterion(output, target).item()
            pred = output.argmax(dim=1)
            val_correct += pred.eq(target).sum().item()

    val_loss /= len(val_loader)
    val_acc = val_correct / len(val_loader.dataset)

    # Log epoch metrics
    writer.add_scalars('Loss', {'train': train_loss, 'val': val_loss}, epoch)
    writer.add_scalars('Accuracy', {'train': train_acc, 'val': val_acc}, epoch)

    # Log learning rate
    writer.add_scalar('Learning_rate', optimizer.param_groups[0]['lr'], epoch)

    # Log histograms (every 5 epochs)
    if epoch % 5 == 0:
        for name, param in model.named_parameters():
            writer.add_histogram(name, param, epoch)

    # Log sample predictions
    if epoch % 10 == 0:
        sample_images = data[:8]
        writer.add_image('Sample_inputs', make_grid(sample_images), epoch)

writer.close()

TensorFlow/Keras 训练

import tensorflow as tf

# Define model
model = tf.keras.models.Sequential([
    tf.keras.layers.Conv2D(32, 3, activation='relu', input_shape=(28, 28, 1)),
    tf.keras.layers.MaxPooling2D(),
    tf.keras.layers.Flatten(),
    tf.keras.layers.Dense(128, activation='relu'),
    tf.keras.layers.Dense(10, activation='softmax')
])

model.compile(
    optimizer='adam',
    loss='sparse_categorical_crossentropy',
    metrics=['accuracy']
)

# TensorBoard callback
tensorboard_callback = tf.keras.callbacks.TensorBoard(
    log_dir='logs/fit',
    histogram_freq=1,          # Log histograms every epoch
    write_graph=True,          # Visualize model graph
    write_images=True,         # Visualize weights as images
    update_freq='epoch',       # Log metrics every epoch
    profile_batch='500,520',   # Profile batches 500-520
    embeddings_freq=1          # Log embeddings every epoch
)

# Train
model.fit(
    x_train, y_train,
    epochs=10,
    validation_data=(x_val, y_val),
    callbacks=[tensorboard_callback]
)

比较实验

多次运行

# Run experiments with different configs
python train.py --lr 0.001 --logdir runs/exp1
python train.py --lr 0.01 --logdir runs/exp2
python train.py --lr 0.1 --logdir runs/exp3

# View all runs together
tensorboard --logdir=runs

在 TensorBoard 中：

• 所有运行都出现在同一个仪表盘中
• 开启/关闭运行以进行比较
• 使用正则表达式筛选运行名称
• 叠加图表以比较指标

组织实验

# Hierarchical organization
runs/
├── baseline/
│   ├── run_1/
│   └── run_2/
├── improved/
│   ├── run_1/
│   └── run_2/
└── final/
    └── run_1/

# Log with hierarchy
writer = SummaryWriter('runs/baseline/run_1')

最佳实践

1. 使用描述性的运行名称

# ✅ Good: Descriptive names
from datetime import datetime
timestamp = datetime.now().strftime('%Y%m%d_%H%M%S')
writer = SummaryWriter(f'runs/resnet50_lr0.001_bs32_{timestamp}')

# ❌ Bad: Auto-generated names
writer = SummaryWriter()  # Creates runs/Jan01_12-34-56_hostname

2. 对相关指标进行分组

# ✅ Good: Grouped metrics
writer.add_scalar('Loss/train', train_loss, step)
writer.add_scalar('Loss/val', val_loss, step)
writer.add_scalar('Accuracy/train', train_acc, step)
writer.add_scalar('Accuracy/val', val_acc, step)

# ❌ Bad: Flat namespace
writer.add_scalar('train_loss', train_loss, step)
writer.add_scalar('val_loss', val_loss, step)

3. 定期记录，但不要过于频繁

# ✅ Good: Log epoch metrics always, batch metrics occasionally
for epoch in range(100):
    for batch_idx, (data, target) in enumerate(train_loader):
        loss = train_step(data, target)

        # Log every 100 batches
        if batch_idx % 100 == 0:
            writer.add_scalar('Loss/batch', loss, global_step)

    # Always log epoch metrics
    writer.add_scalar('Loss/epoch', epoch_loss, epoch)

# ❌ Bad: Log every batch (creates huge log files)
for batch in train_loader:
    writer.add_scalar('Loss', loss, step)  # Too frequent

4. 完成后关闭 writer

# ✅ Good: Use context manager
with SummaryWriter('runs/exp1') as writer:
    for epoch in range(10):
        writer.add_scalar('Loss', loss, epoch)
# Automatically closes

# Or manually
writer = SummaryWriter('runs/exp1')
# ... logging ...
writer.close()

5. 为训练/验证使用单独的 writer

# ✅ Good: Separate log directories
train_writer = SummaryWriter('runs/exp1/train')
val_writer = SummaryWriter('runs/exp1/val')

train_writer.add_scalar('loss', train_loss, epoch)
val_writer.add_scalar('loss', val_loss, epoch)

性能分析

TensorFlow Profiler

# Enable profiling
tensorboard_callback = tf.keras.callbacks.TensorBoard(
    log_dir='logs',
    profile_batch='10,20'  # Profile batches 10-20
)

model.fit(x, y, callbacks=[tensorboard_callback])

# View in TensorBoard Profile tab
# Shows: GPU utilization, kernel stats, memory usage, bottlenecks

PyTorch Profiler

import torch.profiler as profiler

with profiler.profile(
    activities=[
        profiler.ProfilerActivity.CPU,
        profiler.ProfilerActivity.CUDA
    ],
    on_trace_ready=torch.profiler.tensorboard_trace_handler('./runs/profiler'),
    record_shapes=True,
    with_stack=True
) as prof:
    for batch in train_loader:
        loss = train_step(batch)
        prof.step()

# View in TensorBoard Profile tab

资源

• 文档：https://www.tensorflow.org/tensorboard
• PyTorch 集成：https://pytorch.org/docs/stable/tensorboard.html
• GitHub：https://github.com/tensorflow/tensorboard（27k+ stars）
• TensorBoard.dev：https://tensorboard.dev（公开分享实验）

另请参阅

• references/visualization.md - 全面的可视化指南
• references/profiling.md - 性能分析模式
• references/integrations.md - 特定框架的集成示例