field_set.hpp

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// core — named registry of structured cell/face fields (the multiphysics field container).
//
// A method code (flow, and later coupling) accumulates an open-ended set of per-cell fields:
// velocity components, pressure, the SDF, transported scalars (temperature, concentration, phase
// fractions), and material-property fields (density, viscosity). Rather than hard-code each as a
// named member and hand-list them wherever the full set matters (halo exchange, load-balance
// redistribution), the FieldSet keeps them in one place keyed by name.
//
// It is a *directory*, not an owner of policy: it holds the device buffer, its ghost width and
// centering, and whether the FieldSet allocated it (add) or merely aliases a member the solver
// already owns (adopt). It carries NO halo objects — exchange stays per-call on the caller's
// topology (docs/INTERFACES.md: the Field concept is duck-typed on the exchanger side).
//
// Header-only, Kokkos-required (pulls in common/view.hpp). Payload type is fixed to double:
// Eulerian field state is double per docs/CONVENTIONS.md (§ precision policy).
#ifndef PECLET_CORE_FIELD_FIELD_SET_HPP
#define PECLET_CORE_FIELD_FIELD_SET_HPP
 
#include <algorithm>
#include <stdexcept>
#include <string>
#include <unordered_map>
#include <vector>
 
#include "peclet/core/common/view.hpp"
 
namespace peclet::core {
 
enum class Centering { Cell, FaceX, FaceY, FaceZ };
 
struct FieldRec {
  View<double> data;
  int ghost = 0;
  Centering centering = Centering::Cell;
  bool ownStorage = false;
};
 
class FieldSet {
 public:
  FieldRec& add(const std::string& name, std::size_t n, int ghost, Centering c = Centering::Cell) {
    recs_[name] = FieldRec{View<double>(name, n), ghost, c, true};
    return recs_.at(name);
  }
 
  FieldRec& adopt(const std::string& name, View<double> v, int ghost,
                  Centering c = Centering::Cell) {
    recs_[name] = FieldRec{std::move(v), ghost, c, false};
    return recs_.at(name);
  }
 
  bool has(const std::string& name) const { return recs_.find(name) != recs_.end(); }
 
  FieldRec& at(const std::string& name) {
    auto it = recs_.find(name);
    if (it == recs_.end())
      throw std::out_of_range("FieldSet: no field named '" + name + "'");
    return it->second;
  }
  const FieldRec& at(const std::string& name) const {
    auto it = recs_.find(name);
    if (it == recs_.end())
      throw std::out_of_range("FieldSet: no field named '" + name + "'");
    return it->second;
  }
 
  std::size_t size() const { return recs_.size(); }
 
  std::vector<std::string> names() const {
    std::vector<std::string> out;
    out.reserve(recs_.size());
    for (const auto& kv : recs_)
      out.push_back(kv.first);
    std::sort(out.begin(), out.end());
    return out;
  }
 
 private:
  std::unordered_map<std::string, FieldRec> recs_;
};
 
}  // namespace peclet::core
 
#endif  // PECLET_CORE_FIELD_FIELD_SET_HPP