Why doesn't debugger break in kernel code

Question

I have Eclipse Nsight 5.0 (CUDA 5.0) installed on a 64 Bit Ubuntu 12.04 Machine with two Graphic Cards: Geforce GT 240 Desktop UI and Geforce GTX 480 for debugging. I can compile and run the Cuda program just fine. However, when I set a breakpoint in the Cuda code and start debugging, the cursor doesn't halt on the line but jumps to the end of the kernel function.

I have set in Debug Configurations the Geforce GTX 480 as the debugger and check the return value of each kernel call. What else can I try? Also, I don't have root permission on this PC.

Breakpoints are not necessarily hit in kernel functions. The code actually executed on the GPU is significantly different from the code you are trying to set breakpoints in since the CUDA compiler usually performs a very aggressive code optimization. — Vitality

Eugene Eugene · Accepted Answer · 2013-10-01T20:36:15

Does your kernel get executed when running under the debugger (e.g. do you see proper values updated)? It may be that your NVIDIA driver is not compatible with the toolkit.

If the kernel is not executing, chances are this is something simple, e.g. your kernel is compiled for architecture that is incompatible with the card you use to debug.

Do you have cudaDeviceSynchronize after your kernel call? Do you check its return value?

Why doesn't debugger break in kernel code

1 Answers