Explanation of CUDA C and C++

Question

Can anyone give me a good explanation as to the nature of CUDA C and C++? As I understand it, CUDA is supposed to be C with NVIDIA's GPU libraries. As of right now CUDA C supports some C++ features but not others.

What is NVIDIA's plan? Are they going to build upon C and add their own libraries (e.g. Thrust vs. STL) that parallel those of C++? Are they eventually going to support all of C++? Is it bad to use C++ headers in a .cu file?

Answer 1

CUDA is a platform (architecture, programming model, assembly virtual machine, compilation tools, etc.), not just a single programming language. CUDA C is just one of a number of language systems built on this platform (CUDA C, C++, CUDA Fortran, PyCUDA, are others.)

CUDA C++

Currently CUDA C++ supports the subset of C++ described in Appendix D ("C/C++ Language Support") of the CUDA C Programming Guide.

To name a few:

• Classes
• __device__ member functions (including constructors and destructors)
• Inheritance / derived classes
• virtual functions
• class and function templates
• operators and overloading
• functor classes

Edit: As of CUDA 7.0, CUDA C++ includes support for most language features of the C++11 standard in __device__ code (code that runs on the GPU), including auto, lambda expressions, range-based for loops, initializer lists, static assert, and more.

Examples and specific limitations are also detailed in the same appendix linked above. As a very mature example of C++ usage with CUDA, I recommend checking out Thrust.

Future Plans

(Disclosure: I work for NVIDIA.)

I can't be explicit about future releases and timing, but I can illustrate the trend that almost every release of CUDA has added additional language features to get CUDA C++ support to its current (In my opinion very useful) state. We plan to continue this trend in improving support for C++, but naturally we prioritize features that are useful and performant on a massively parallel computational architecture (GPU).