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#pragma once
#include <array>
#include <functional>
#include <eigen3/unsupported/Eigen/CXX11/Tensor>
template <class Scalar, int p, std::size_t... Indices>
Eigen::Tensor<Scalar, p> initializeJHelper(unsigned N, std::index_sequence<Indices...>) {
std::array<unsigned, p> Ns;
std::fill_n(Ns.begin(), p, N);
return Eigen::Tensor<Scalar, p>(std::get<Indices>(Ns)...);
}
template <class Scalar, int p>
Eigen::Tensor<Scalar, p> initializeJ(unsigned N) {
return initializeJHelper<Scalar, p>(N, std::make_index_sequence<p>());
}
template <class Scalar, int p, std::size_t... Indices>
void setJHelper(Eigen::Tensor<Scalar, p>& J, const std::array<unsigned, p>& ind, Scalar val, std::index_sequence<Indices...>) {
J(std::get<Indices>(ind)...) = val;
}
template <class Scalar, int p>
void setJ(Eigen::Tensor<Scalar, p>& J, std::array<unsigned, p> ind, Scalar val) {
do {
setJHelper<Scalar, p>(J, ind, val, std::make_index_sequence<p>());
} while (std::next_permutation(ind.begin(), ind.end()));
}
template <class Scalar, int p, std::size_t... Indices>
Scalar getJHelper(const Eigen::Tensor<Scalar, p>& J, const std::array<unsigned, p>& ind, std::index_sequence<Indices...>) {
return J(std::get<Indices>(ind)...);
}
template <class Scalar, int p>
Scalar getJ(const Eigen::Tensor<Scalar, p>& J, const std::array<unsigned, p>& ind) {
return getJHelper<Scalar, p>(J, ind, std::make_index_sequence<p>());
}
template <class Scalar, int p>
void iterateOverHelper(Eigen::Tensor<Scalar, p>& J,
std::function<void(Eigen::Tensor<Scalar, p>&, std::array<unsigned, p>)>& f,
unsigned l, std::array<unsigned, p> is) {
if (l == 0) {
f(J, is);
} else {
unsigned iMin;
if (l == p) {
iMin = 0;
} else {
iMin = is[p - l - 1];
}
for (unsigned i = iMin; i < J.dimension(p - 1); i++) {
std::array<unsigned, p> js = is;
js[p - l] = i;
iterateOverHelper<Scalar, p>(J, f, l - 1, js);
}
}
}
template <class Scalar, int p>
void iterateOver(Eigen::Tensor<Scalar, p>& J, std::function<void(Eigen::Tensor<Scalar, p>&, std::array<unsigned, p>)>& f) {
std::array<unsigned, p> is;
iterateOverHelper<Scalar, p>(J, f, p, is);
}
template <class Scalar, int p, class Distribution, class Generator>
Eigen::Tensor<Scalar, p> generateCouplings(unsigned N, Distribution d, Generator& r) {
Eigen::Tensor<Scalar, p> J = initializeJ<Scalar, p>(N);
std::function<void(Eigen::Tensor<Scalar, p>&, std::array<unsigned, p>)> setRandom =
[&d, &r] (Eigen::Tensor<Scalar, p>& JJ, std::array<unsigned, p> ind) {
setJ<Scalar, p>(JJ, ind, d(r));
};
iterateOver<Scalar, p>(J, setRandom);
return J;
}
template <class Scalar>
Eigen::Matrix<Scalar, Eigen::Dynamic, Eigen::Dynamic>
contractDown(const Eigen::Tensor<Scalar, 2>& J, const Eigen::Matrix<Scalar, Eigen::Dynamic, 1>& z) {
return Eigen::Map<const Eigen::Matrix<Scalar, Eigen::Dynamic, Eigen::Dynamic>>(J.data(), z.size(), z.size());
}
const std::array<Eigen::IndexPair<int>, 1> ip00 = {Eigen::IndexPair<int>(0, 0)};
template <class Scalar, int r>
Eigen::Matrix<Scalar, Eigen::Dynamic, Eigen::Dynamic>
contractDown(const Eigen::Tensor<Scalar, r>& J, const Eigen::Matrix<Scalar, Eigen::Dynamic, 1>& z) {
Eigen::Tensor<Scalar, 1> zT = Eigen::TensorMap<Eigen::Tensor<const Scalar, 1>>(z.data(), {z.size()});
Eigen::Tensor<Scalar, r - 1> Jz = J.contract(zT, ip00);
return contractDown(Jz, z);
}
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