C and CUDA

Programming language:

• static codes st-wslda: C99 standard
• time dependent codes td-wslda: mixture of C99 and CUDA.

In general CUDA is compatible with C99. Thus, in practice when editing files (predefines.h, problem-definition.h or logger.h) you can use C language irrespectively to code variants (st or td). There is only one exception related to function delta_ext in problem-definition.h file. It declaration is

• static codes st-wslda:

double complex delta_ext(int ix, int iy, int iz, int it, double complex delta, double *params, size_t extra_data_size, void *extra_data)

• time dependent codes td-wslda:

__device__ Complex delta_ext(int ix, int iy, int iz, int it, Complex delta, double *params, size_t extra_data_size, void *extra_data)

The change arises from incompatibility of complex type in C99 and CUDA. Namely:

• st-wslda: return type must be C99 double complex
• td-wslda: return type must be compatible with CUDA Complex

Below we provide example of the same code written in both standards:

• C99

double complex delta_ext(int ix, int iy, int iz, int it, double complex delta, double *params, size_t extra_data_size, void *extra_data)
{
    double complex D = 1.0 + I*2.0; // assign value
    double complex Dc = conj(D); // complex conjugate
    double absolute_value = cabs(D);
    double phase = carg(D);
    double real_part = creal(D);
    double imginary_part = cimag(D);
    double complex exponentiation = cexp(D);
    double complex power = cpow(D, 2);
    // ...
    
    return D; 
}

• CUDA

__device__ Complex delta_ext(int ix, int iy, int iz, int it, Complex delta, double *params, size_t extra_data_size, void *extra_data)
{
    Complex D = Complex(1.0,2.0); // assign value
    Complex Dc = thrust::conj(D); // complex conjugate
    double absolute_value = thrust::abs(D);
    double phase = thrust::arg(D);
    double real_part = D.real();
    double imginary_part = D.imag();
    Complex exponentiation = thrust::exp(D);
    Complex power = thrust::pow(D, 2);
    // ...
    
    return D; 
}