power_cone.hpp

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/*
 * Copyright © 2025-2026 Akreon LLC
 * SPDX-License-Identifier: Apache-2.0
 */
 
#pragma once
 
#include "cone.hpp"
 
namespace conic {
 
template <linalg::VectorContainer Slack>
struct PowerCone : public Cone<Slack, PowerCone<Slack>, ConeType::ASYMMETRIC> {
  using ConeBase = Cone<Slack, PowerCone<Slack>, ConeType::ASYMMETRIC>;
 
  using ConeBase::M;
  using typename ConeBase::T;
 
  using AlphaVec = linalg::Vector<T, M - 1>;
 
  constexpr explicit PowerCone(const AlphaVec& alphas_in) : alphas(alphas_in) {}
 
  constexpr Slack x0_impl() const {
    Slack s{};
    for (std::size_t i = 0; i < M - 1; ++i) s(i) = T(1);
    return s;
  }
 
  constexpr bool in_cone_impl(const Slack& x) const {
    if (T(x(M - 1)) == T(0)) {
      for (std::size_t i = 0; i < M - 1; ++i)
        if (x(i) < T(0)) return false;
      return true;
    } else {
      T res{};
      for (std::size_t i = 0; i < M - 1; ++i) {
        if (!(x(i) > T(0))) return false;
        res += alphas(i) * linalg::constexpr_ln_safe(x(i));
      }
      const auto rhs =
          linalg::constexpr_ln_safe(linalg::constexpr_abs(x(M - 1)));
      return res > rhs;
    }
  }
 
  constexpr T alpha_max_impl(const Slack& x,
                             const linalg::Vector<T, M>& p) const {
    (void)x, (void)p;
    return T(0);
  }
 
  AlphaVec alphas;
};
 
} // namespace conic