Function getDisceteFourierTransform

tests/utils/linalg.cpp:160–176

qvector getDisceteFourierTransform(qvector in) {
    DEMAND( in.size() > 0 );
    
    size_t dim = in.size();
    qvector out = getZeroVector(dim);

    // PI must be accurate here
    qreal pi = 3.14159265358979323846;
    qreal a = 1 / std::sqrt(dim);
    qreal b = 2 * pi / dim;
    
    for (size_t x=0; x<dim; x++)
        for (size_t y=0; y<dim; y++)
            out[x] += a * std::exp(b * x * y * 1_i) * in[y];

    return out;
}


qvector getDisceteFourierTransform(qvector in, vector<int> targs) {