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启动后调用 cudaGetLastError

捕获无效的启动配置

启动后调用 cudaGetLastError 是 CoddyKit 上的免费 CUDA Academy 课时。这是第 2 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 CUDA Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 CUDA 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。

Catching the Silent Launch

Since a kernel launch returns nothing, you need a helper to ask the GPU what just happened. That helper is cudaGetLastError. 🔎

What It Returns

cudaGetLastError hands back the most recent error code recorded by the runtime, or cudaSuccess if everything is fine so far.

myKernel<<<g, b>>>(d);
cudaError_t e = cudaGetLastError();

Call It Right After Launch

Place the check on the very next line after the launch. That captures configuration mistakes before any other call overwrites the state.

kernel<<<g, b>>>();
if (cudaGetLastError() != cudaSuccess) abort();

It Catches Launch Config Errors

This catches the configuration stage: too many threads per block, zero blocks, or a grid that the device simply cannot accept.

kernel<<<g, 99999>>>(); // invalid thread count

It Clears the Error

Reading the error also resets it to cudaSuccess. The runtime keeps only the last error, so checking it wipes the slate clean.

Peek Without Clearing

Want to look without resetting? Use cudaPeekAtLastError. It returns the same code but leaves the error state untouched.

cudaError_t e = cudaPeekAtLastError();

It Does Not Catch Runtime Faults

By itself, this only sees the launch, not the execution. An out-of-bounds access inside the kernel still slips past it.

Pair It With a Sync

To catch runtime faults, follow up with cudaDeviceSynchronize. The launch check plus a sync covers both stages of failure.

kernel<<<g, b>>>();
cudaGetLastError();
cudaDeviceSynchronize();

Why Two Checks Help

The launch check tells you the config was valid; the sync tells you the kernel actually finished without crashing. You learn which stage broke.

Wrap It in a Macro

Typing this after every launch gets old. Most projects wrap the launch check in a tidy macro so it is one short line.

kernel<<<g, b>>>();
CHECK_LAUNCH();

A Debugging Lifesaver

When a kernel mysteriously does nothing, a quick cudaGetLastError often reveals an invalid launch you would never have spotted otherwise.

Quick Check

Test your grasp of cudaGetLastError.

Recap: Check the Launch

Call cudaGetLastError right after a launch to catch config errors, then sync for runtime faults. Two checks reveal where things broke. 🎉

常见问题解答

「启动后调用 cudaGetLastError」课时是免费的吗？

是的 — 「启动后调用 cudaGetLastError」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 CUDA Academy 课程的其余内容，请升级到 CoddyKit PRO。 CUDA Academy 课程共包含 4 节课。

「启动后调用 cudaGetLastError」这节课中我会学到什么？

捕获无效的启动配置你通过在浏览器中直接运行的动手代码来练习 CUDA 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 CUDA Academy 需要有经验吗？

无需任何先前经验。CoddyKit 上的 CUDA 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 2 节课，共 4 节。

「启动后调用 cudaGetLastError」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 CUDA Academy 课中编写并运行代码吗？

能。每节 CUDA 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。

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