控制记忆的门
了解 LSTM 如何决定保留什么
控制记忆的门 是 CoddyKit 上的免费 NLP Academy 课时。 这是第 1 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 NLP Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 NLP 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。
Plain RNNs Forget
A simple RNN struggles to remember things from far back. The LSTM was built to fix that by carefully managing what it keeps and forgets. 🧠
The Cell State
An LSTM carries a special cell state, a memory line that runs straight through every step so important signals survive long sequences.
Gates Are the Trick
The magic is in the gates: tiny learned switches that decide what to add, keep, or drop from memory at each time step.
How a Gate Works
Each gate uses a sigmoid to output values from 0 to 1, acting like a dimmer that lets some information through and blocks the rest.
gate = sigmoid(W @ x + U @ h + b) # values in [0, 1]The Forget Gate
The forget gate looks at the new input and decides how much of the old memory to erase. A 0 wipes it; a 1 keeps it fully.
The Input Gate
The input gate controls how much fresh information gets written into the cell state, so only useful new signals are stored.
The Candidate Values
A candidate vector proposes what new content could enter memory. The input gate then scales how much of it actually gets added.
candidate = tanh(W @ x + U @ h + b)Updating Memory
The new cell state blends old memory kept by the forget gate with fresh candidate values let in by the input gate.
c = forget * c_prev + input * candidateThe Output Gate
The output gate decides what part of the cell state becomes the visible hidden state passed to the next step and the layer above.
Why Gates Beat Forgetting
Because gates keep the cell state mostly additive, gradients flow back many steps without vanishing. That is how an LSTM remembers long context.
Three Gates, One Cell
So an LSTM has three gates guarding one memory line: forget, input, and output, each learned from data during training.
Quick Check
Test your grip on LSTM gates.
Recap
An LSTM protects a cell state with forget, input, and output gates. Those switches keep long-range memory alive where plain RNNs fail. ✅
常见问题解答
「控制记忆的门」课时是免费的吗？
是的 — 「控制记忆的门」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 NLP Academy 课程的其余内容，请升级到 CoddyKit PRO。 NLP Academy 课程共包含 4 节课。
「控制记忆的门」这节课中我会学到什么？
了解 LSTM 如何决定保留什么 你通过在浏览器中直接运行的动手代码来练习 NLP 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 NLP Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 NLP 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 1 节课，共 4 节。
「控制记忆的门」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 NLP Academy 课中编写并运行代码吗？
能。每节 NLP 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。