exp_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 ExpCone : public Cone<Slack, ExpCone<Slack>, ConeType::ASYMMETRIC> {
  using ConeBase = Cone<Slack, ExpCone<Slack>, ConeType::ASYMMETRIC>;
 
  using ConeBase::M;
  using typename ConeBase::T;
 
  static_assert(M % 3 == 0, "Exp cone must be a triplet");
 
  constexpr Slack x0_impl() const {
    Slack s{};
    for (std::size_t i = 0; i < M / 3; ++i) s(i) = T(0);
    for (std::size_t i = M / 3; i < 2 * M / 3; ++i) s(i) = T(1);
    for (std::size_t i = 2 * M / 3; i < M; ++i) s(i) = T(2);
    return s;
  }
 
  constexpr bool in_cone_impl(const Slack& x) const {
    for (std::size_t i = 0; i < M / 3; ++i) {
      const auto u = x(i);
      const auto v = x(M / 3 + i);
      const auto w = x(2 * M / 3 + i);
      if (v <= T(0) || v * linalg::constexpr_exp(u / v) >= w) return false;
    }
    return true;
  }
 
  constexpr T alpha_max_impl(const Slack& x,
                             const linalg::Vector<T, M>& p) const {
    (void)x, (void)p;
    return T(0);
  }
};
 
} // namespace conic