__CUDACC__

Accelerated Computing CUDA CUDA Programming and Performance
1

Hi,

I’m trying to compile a piece of .cu code for both device and host using the CUDACC preprocessor variable. With the code below my error message tells me that blockDim is an undeclared identifier. I have tried inserting this code also into some cuda examples (incase it is my project settings), but no luck. Am I barking up the wrong tree, or should I hopefully be able to get such a technique to work?

Thanks,

Paul

__device__ __host__ int test_both() {

	int x = 1234567;

#ifdef __CUDACC__

	x = blockDim.x;

#endif

	return x;

}
2

Well it’s true this question has been asked before (defines, automatically defined by NVCC?), and the answer was NO; but I’m still convinced that somehow it must be possible. I’ve now tried CUDACC,WIN32, and CUDAFE, plus my own macros with -D and -U, here and there, before and after -Xcompiler, but with no luck.

Surely there’s a way. Perhaps a sneaky undocumented macro that pops up just at the right moment?

A single function, with one name, can accept device and host together, so why truly can’t this be done?

Humbly,
Paul

3

Maybe it’s the CUDABE (“CUDA Back End”) macro you have to check against. (Check file <crt/func_macro.h> for an example.)

/Pyry

4

Thanks, but unfortunately CUDABE is the same as the others. If I test there that it is defined, it compiles (because it’s not defined). Then when I run the program, the results show that the conditional section has been omitted.
Paul

5

Hi,

I do this and it works fine. I just pass a preprocessor define to nvcc using -D. I use the command line nvcc.exe -cubin -DMYPREPROC …
I am using the driver API so maybe it won’t work with the runtime API?

EDIT: I should also mention that in my code I don’t use blockDim or host, device. Maybe there is a problem there.

-DevMike

6

Hi DevMike,

I’m not using the driver API, so I can’t comment there; it’s not an option for me in any case. And I also define my own macros like that. But yes, it’s the built-in variables which are the problem - with non-emulator builds anyway.

Paul