cost_function_phys_phys

auto syten::T3N::BasisTransformation::cost_function_phys_phys

Initial value:

= [](STensor const& t1t2,
                                        SBasisId const& root,
                                        SBasisId const& p1,
                                        SRDef initial_costs,
                                        Truncation const& trunc) {
        auto [fused, fp] = merge(t1t2,
                                 root,
                                 p1);
        auto fused_norm = snorm(fused);
        auto [err, u, s, v, us_basis, sv_basis] = svd(std::move(fused),
                                                      fp,
                                                      Truncation(1.e-14).scaled(fused_norm));
        return trace(s)/initial_costs;
      }