Understanding CUDA

Accelerated Computing CUDA CUDA Programming and Performance
1

Hi,

I.ve been going through the CUDA Toolkit documentation and came across this in the CUDA video decoder section:

// Called by the video parser to decode a single picture. Since the parser will // deliver data as fast as it can, we need to make sure that the picture index // we're attempting to use for decode is no longer used for display.
static int CUDAAPI HandlePictureDecode(void *pUserData, CUVIDPICPARAMS *pPicParams);

I’m just wondering, in the above code, what is CUDAAPI? i.e. is it a typename or a macro etc. I’m struggling to find references to it anywhere else.

Thanks in advance.

2

Anyone able to help?

3

CUDAAPI represents the calling convention. Some operating system platforms, notably Windows, offer multiple calling conventions. My memory is a bit hazy, but I think on Windows CUDAAPI resolves to __stdcall, which is stack-based. You could search the CUDA header files to confirm if you have a need to know this detail. Presumably there is an OS-specific #define for CUDAAPI somewhere in the header files.

4

A small bit of grep-ing on the CUDA header files (in /usr/local/cuda/include on linxu) will show you that CUDAAPI is defined in cuda.h:

#ifdef _WIN32
#define CUDAAPI __stdcall
#else
#define CUDAAPI
#endif

So now your question becomes “what is the meaning of __stdcall” as a function qualifier on the windows platform ?

And that is not a CUDA specific question.

http://stackoverflow.com/questions/297654/what-is-stdcall
https://msdn.microsoft.com/en-us/library/zxk0tw93.aspx

5

Great, thanks very much!