减少 GPU 内存使用
使用检查点与更智能的张量处理
减少 GPU 内存使用 是 CoddyKit 上的免费 Deep Learning Academy 课时。 这是第 4 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Deep Learning Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Deep Learning Academy 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
The Dreaded OOM
Run out of GPU memory and training crashes with an out-of-memory error. The good news is several simple tactics free up space fast.
Where Memory Goes
Your GPU holds the model weights, the gradients, the optimizer state, and the activations saved for backward. Activations are often the biggest.
Shrink the Batch
The fastest fix is a smaller batch size. Fewer samples per step means fewer activations to store, and accumulation can recover the effective size.
No Grad for Inference
During evaluation you do not need gradients. Wrapping inference in torch.no_grad skips storing activations and saves a lot of memory.
with torch.no_grad():
preds = model(x)Mixed Precision Helps Here Too
Half-precision tensors are simply smaller. Turning on autocast cuts activation and weight memory roughly in half during training.
with torch.autocast(device_type='cuda'):
out = model(x)Gradient Checkpointing
Checkpointing trades compute for memory: it drops most activations and recomputes them during backward instead of keeping them all.
from torch.utils.checkpoint import checkpointApply Checkpointing
Wrap a heavy block in checkpoint so its activations are rebuilt on the backward pass. You save memory at the cost of extra recompute.
out = checkpoint(heavy_block, x)Detach What You Log
Keeping a loss tensor around holds its whole graph in memory. Call .item() to log just the number and let the graph be freed.
running_loss += loss.item()Use set_to_none
Pass set_to_none to zero_grad so gradient tensors are released instead of merely filled with zeros, freeing their memory between steps.
optimizer.zero_grad(set_to_none=True)Clear the Cache
PyTorch caches freed blocks for reuse. When you truly need space back, empty_cache returns it to the GPU, though it rarely fixes real leaks.
torch.cuda.empty_cache()Inspect Your Usage
Check how much you hold with memory_allocated. Watching this number while you tune confirms which change actually freed space.
print(torch.cuda.memory_allocated())Quick Check
Which technique saves memory by recomputing activations during backward?
Recap
Beat out-of-memory by shrinking batches, using no_grad for inference, autocast, gradient checkpointing, and set_to_none. Measure with memory_allocated. 🧹
常见问题解答
「减少 GPU 内存使用」课时是免费的吗？
是的 — 「减少 GPU 内存使用」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Deep Learning Academy 课程的其余内容，请升级到 CoddyKit PRO。 Deep Learning Academy 课程共包含 4 节课。
「减少 GPU 内存使用」这节课中我会学到什么？
使用检查点与更智能的张量处理 你通过在浏览器中直接运行的动手代码来练习 Deep Learning Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Deep Learning Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Deep Learning Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 4 节课，共 4 节。
「减少 GPU 内存使用」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Deep Learning Academy 课中编写并运行代码吗？
能。每节 Deep Learning Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。