How to pass structures into CUDA device? - cuda

Question

I've been stuck on this for a while. When I pass my structures into CUDA via kernel parameters, they contain no data and everything is undefined inside of them.
Out in host global space
struct matl1
{
static const double cond;
};
const double matl1::cond = 420.5;
Then inside of main()
matl1 * h_matl1 = (matl1*)malloc(sizeof(matl1));
matl1 * d_matl1;
cudaMalloc((void**)&d_matl1, sizeof(matl1));
cudaMemcpy(d_matl1, h_matl1, sizeof(matl1), cudaMemcpyHostToDevice);
kernel<<<1,1>>>(d_matl1,...);
Then inside of kernel()
__global__ void kernel(matl1* d_matl1,...)
{
double cond = d_matl1->cond;
}
And I get the following error:
error : identifier "matl1::cond" is undefined in device code
As a quick test, if I do the following on the host in main()
cout << h_matl1->cond << endl;
It shows me the correct output of 420.5. I am not sure why this isn't making it into the device.
Here's the rest of my output
uild started: Project: test_struct, Configuration: Debug Win32 ------
Compiling CUDA source file kernel.cu...
C:\Users\User\Documents\Visual Studio 2012\Projects\test_struct\test_struct>"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v5.5\bin\nvcc.exe" -gencode=arch=compute_35,code=\"sm_35,compute_35\" --use-local-env --cl-version 2012 -ccbin "C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\bin" -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v5.5\include" -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v5.5\include" -G --keep-dir Debug -maxrregcount=0 --machine 32 --compile -cudart static -g -DWIN32 -D_DEBUG -D_CONSOLE -D_MBCS -Xcompiler "/EHsc /W3 /nologo /Od /Zi /RTC1 /MDd " -o Debug\kernel.cu.obj "C:\Users\User\Documents\Visual Studio 2012\Projects\test_struct\test_struct\kernel.cu"
1>C:/Users/User/Documents/Visual Studio 2012/Projects/test_struct/test_struct/kernel.cu(15): error : identifier "matl1::cond" is undefined in device code
C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\V110\BuildCustomizations\CUDA 5.5.targets(592,9): error MSB3721: The command ""C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v5.5\bin\nvcc.exe" -gencode=arch=compute_35,code=\"sm_35,compute_35\" --use-local-env --cl-version 2012 -ccbin "C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\bin" -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v5.5\include" -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v5.5\include" -G --keep-dir Debug -maxrregcount=0 --machine 32 --compile -cudart static -g -DWIN32 -D_DEBUG -D_CONSOLE -D_MBCS -Xcompiler "/EHsc /W3 /nologo /Od /Zi /RTC1 /MDd " -o Debug\kernel.cu.obj "C:\Users\User\Documents\Visual Studio 2012\Projects\test_struct\test_struct\kernel.cu"" exited with code 2.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Answer 1

I was able to reproduce your error if I do this:
struct matl1
{
static const double cond;
};
__global__ void kernel(matl1* d_matl1)
{
double cond = d_matl1->cond;
printf("cond = %lf\n", cond);
}
const double matl1::cond = 420.5;
But not if I do this:
struct matl1
{
static const double cond;
};
const double matl1::cond = 420.5;
__global__ void kernel(matl1* d_matl1)
{
double cond = d_matl1->cond;
printf("cond = %lf\n", cond);
}
You need to define the constant initializer before the kernel definition. Here is a complete example that works for me.