Re: [boost] interest in structure of arrays container?

16 Oct 2016


      On 10/16/2016 3:28 AM, Andreas Schäfer wrote:
...
Hey,
On 00:36 Sun 16 Oct     , Michael Marcin wrote:
...
Indeed this works well for a fixed sized dataset.
It doesn't have the wasted duplicated information that a tuple of
std::vectors has.
It still doesn't provide an interface to query the soa directly for an
iterator or size etc.
Both a fixed-sized and dynamic-growth container are useful.
Although I tend to need dynamic growth more often.
I've implemented your example using the soa_grid from LibFlatArray:
================================= 8< ============================
#include 
class citizen
{
public:
    std::string first_name;
    std::string last_name;
    int salary;
    int age;
};
LIBFLATARRAY_REGISTER_SOA(
    citizen,
    ((std::string)(first_name))
    ((std::string)(last_name))
    ((int)(salary))
    ((int)(age)))
int main()
{
    LibFlatArray::soa_grid<citizen> citizens(300, 1, 1);
    long accumulator = 0;
citizens.callback([&citizens, &accumulator](auto i) {
            for (; i.index() < citizens.dim_x(); ++i) {
                accumulator += i.salary();
            }
        });
    int average = accumulator / citizens.dim_x();
return 0;
}
================================= 8< ============================
The size of the soa_grid can be chose at runtime, but it might not be
a good match for the use case you describe: it's essentially 3D and
hence doesn't support push_back() and friends. On the other hand,
LibFlatArray::soa_array is 1D and behaves much more like std::vector,
but it also has a maximum size that's fixated at compile time.
Thanks for clarifying.
...
Would something like an soa_vector, that's resizable at runtime and
behaves much like a std::vector better suit your needs?
Yes exactly that.
I would also strongly prefer a tuple-like variadic template interface to 
a macro interface.