How to initialize OpenCL const vector with C++ array? [Host]

Question

In my class, I have the following declaration:

class OCLState {
    //Irrelevant stuff involving OpenCL contexts and command queues and so on...
    const cl_int16 values;

    OCLState(const std::array<int, 16> & _values);
}

So naturally, I need to initialize the vector when I create this object. Problem is, how do I translate _values into a form that values will accept as an initializer?

OCLState::OCLState(const std::array<int, 16> & _values) : values(
{ _values[0], _values[1], _values[2], _values[3] , _values[4] , _values[5] , _values[6], _values[7],
_values[8], _values[9], _values[10], _values[11] , _values[12] , _values[13] , _values[14], _values[15] }
) {
    //Irrelevant stuff involving setting up contexts and queues and so forth
}

This works, but it is EXTREMELY cumbersome and difficult to read. Is there a better way?

EDIT:

OCLState::OCLState(const std::array<int, 16> & _values) : values(array_to_vector(_values)) {

}

cl_int16 OCLState::array_to_vector(const std::array<int, 16> & in) {
    cl_int16 out;
    for (int i = 0; i < 16; i++) out.s[i] = in[i];
    return out;
}

This also works, but I consider it to be non-ideal. I'm looking for a way that doesn't involve writing helper methods for every single vector I might use when writing these programs.

simpel01 · Accepted Answer · 2015-11-20 20:41:07Z

1

One way to get around this without renouncing to the const-ness is by using the loved/hated reinterpret_cast. You could define your constructor as follows:

OCLState::OCLState(const std::array<int, 16> &_values) : 
    values(*reinterpret_cast<const cl_int16*>(&_values.front())) { }

Which produces the desired behaviour:

int main(int argc, char *argv[]) {
    OCLState S({0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15});
    std::cout << S.values.s[0] << "," << S.values.s[15] << std::endl;
}

prints > 0, 15

answered Nov 20, 2015 at 20:41

simpel01

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1 Comment

Xirema Over a year ago

Hmm. This is ugly, but it adheres to the principle of what I'm trying to do. I'll consider it and decide whether it makes my life easier or not.

FrankM · Accepted Answer · 2015-11-20 18:41:12Z

0

use can use std::copy (include < algorithm >) inside the constructor body

std::copy ( _values.begin(),_values.end(), &values.s[0]);

You'll have to remove the const from values though

Or wrap this code in a template function similar to your helper function

edited Nov 20, 2015 at 18:41

answered Nov 20, 2015 at 18:27

FrankM

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