Question

I know that there is the restriction to call only __device__ functions in the kernel. This prevents me from calling standard functions like strcmp() and so on in the kernel.
At this point I am not able to understand/find the reasons for this. Could not the compiler just follow each includes in strings.h and so on while inlining the calls to strcmp() in the kernel? I guess the reason I am looking for is easy and I am missing something here.
Is it the only way to reimplement all the functions and datatypes I need in kernel computation? Is there a codebase with such reimplementations?

Answer 1

Yes, the only way to use stdlib’s functions from kernel is to reimplement them. But I strongly advice you to reconsider this idea, since it’s highly unlikely you would need to run code that uses strcmp() on GPU. Please, add additional details about your problem, so a better solution could be proposed (I highly doubt that serial string comparison on GPU is what you really need).

It’s barely possible to simply recompile all stdlib for GPU, since it depends a lot on some system calls (like memory allocation), which could not be used on GPU (well, in recent versions of CUDA toolkit you can allocate device memory from kernel, but it’s not “cuda-way”, is supported only by newest hardware and is very bad for performance).
Besides, CPU versions of most functions is far from being “good” for GPUs. So, in vast majority of cases compiling your ordinary CPU functions for GPU would lead to no good, so the compiler doesn’t even try it.