how can i execute a host class function in a CUDA kernel - cuda

Question

I have a genetic algorithm and i'm traying to evaluate a population of chromosome on GPU :
class chromosome
{
int fitness;
int gene(int pos) { .... };
};
class eval
{
public :
__global__ doEval(Chromosome *population)
{
....
int jobid = population[tid].gene(X);
population[tid].fitness = Z;
....
}
};
int main()
{
Chromosome *dev_population;
Eval eval;
eval.doEval<<<1,N>>>(dev_population);
}
and i have this errors :
ga3.cu(121): warning: inline qualifier ignored for "global" function
ga3.cu(121): error: illegal combination of memory qualifiers
ga3.cu(323): error: a pointer to a bound function may only be used to call the function
ga3.cu(398): warning: nested comment is not allowed
where are the problems ?
i remove Eval class and left only doEval function , and make device host gene() , like this :
\__device\__ \__host\__ gene()
{....};
\__global\__ doEval(Chromosome *population)
{
....
int jobid = population[tid].gene(X);
population[tid].fitness = Z;
....
}
int main()
{
Chromosome *dev_population;
doEval<<<1,N>>>(dev_population);
}
but now i have have other errors , and it's not compile :
/usr/include/c++/4.6/iomanip(66): error: expected an expression
/usr/include/c++/4.6/iomanip(96): error: expected an expression
/usr/include/c++/4.6/iomanip(127): error: expected an expression
/usr/include/c++/4.6/iomanip(195): error: expected an expression
/usr/include/c++/4.6/iomanip(225): error: expected an expression
5 errors detected in the compilation of "/tmp/tmpxft_00006fe9_00000000-4_ga3.cpp1.ii".

Answer 1

There are two problems here, one soluble, the other one not.
It is illegal in CUDA for a __global__ function (ie. kernel) to be defined as a class member function. So doEval can never be defined as a member of eval. You are free to call a kernel in a structure or class member function, but a kernel cannot be a member function. You will have to redesign this class, there is no work around.
Any function called device code must be explicitly denoted as a device function and be instantiated and compiled for the device. This applies to both regular functions and class member functions. All functions are treated by nvcc as host functions unless identified as otherwise. You can, therefore, fix this error by doing something like the following:
class chromosome
{
int fitness;
__device__ __host__ int gene(int pos) { .... };
};
Note that every function called by gene must also have a valid device definition for the code to successfully compile.