使用CUDA和犰狳

Question

I have a .cu file in a 64x VS2010 project. This project is configured to extract a .mexw64 file. Bellow there is the example I run. Inside the mex function I want to use some functions of the Armadillo linear algebra library. So When the #include "armaMex.hpp" is used the compiler return some errors:

1. error C3203: 'fixed' : unspecialized class template can't be used as a template argument for template parameter 'T1', expected a real type c:....\\armadillo-4.200.0\\include\\armadillo_bits\\Mat_meat.hpp
2. error C2955: 'arma::Mat::fixed' : use of class template requires template argument list c:\\ ....\\armadillo-4.200.0\\include\\armadillo_bits\\Mat_meat.hpp
3. error C1903: unable to recover from previous error(s); stopping compilation c:\\ ....\\armadillo-4.200.0\\include\\armadillo_bits\\Mat_meat.hpp

I can not figure out what is causing these errors. Could you please give an explanation?

#include "mex.h" 
#include "armaMex.hpp"
void
    mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
    mexPrintf("hello!\n");
}

PS: CUDA SDK 5.5 64x, VS2010

Answer 1

This is a known limitation of nvcc (technically cudafe++, I think). nvcc uses file extension to determine whether a given source file should be processed for device code or passed to the CUDA preprocessors and then the device compiler. It looks like that compilation trajectory can't correctly parse some of the very complex declarations that Armadillo contains, and the compile fails. This is known to happen with Boost, Eigen and QT. I guess Armadillo is in the same boat.

The solution is to not import Armadillo headers inside a .cu file. Put your host boost code in a .cc file, device code and kernel launches in a separate .cu file and make some thin wrappers to access the kernel calls from the .cc file. You can still pass all the source to nvcc to compile into a single object file, but separating the Armadillo imports from the device code eliminates the problem of the front end choking on the complex template declarations Armadillo contains.