spn_tinvariants.h

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/*
 * Copyright (c) 2012-2026, QORE Lab, Imperial College London
 * All rights reserved.
 */
#ifndef LINE_API_SPN_SPN_TINVARIANTS_H
#define LINE_API_SPN_SPN_TINVARIANTS_H
 
/**
 * @file
 * @ingroup api_spn
 * Minimal-support T-invariants of a stochastic Petri net (Murata 1989, sec. V;
 * Haverkort 1998, sec. 14.2): the non-negative integer firing-count vectors x
 * with C x = 0, by the same Farkas elimination as spn_sinvariants run on C'.
 * Each row of X is a firing-count vector over the (transition, mode) events.
 * A T-invariant is a structural property: inhibitor arcs, priorities and the
 * timed/immediate split do not enter C and are ignored. MATLAB twin:
 * matlab/src/api/spn/spn_tinvariants.m.
 */
 
#include <cstddef>
#include <vector>
 
#include "line/api/spn/spn_net.h"
 
namespace line {
namespace spn {
 
struct SpnTInvariants {
    std::vector<std::size_t> transitions;  ///< 1-based node index of each event
    std::vector<std::size_t> modes;        ///< 0-based mode index of each event
    std::vector<std::vector<long long>> X; ///< one minimal-support T-invariant per row
};
 
template <class T>
SpnTInvariants spn_tinvariants(const qn::NetworkStruct<T>& sn) {
    const detail::SpnNet net = detail::spn_build_net(sn, "spn_tinvariants");
    SpnTInvariants out;
    out.transitions = net.transitions;
    out.modes = net.modes;
    out.X = detail::spn_farkas(detail::spn_transpose(net.C, net.E), net.n);
    return out;
}
 
}  // namespace spn
}  // namespace line
 
#endif  // LINE_API_SPN_SPN_TINVARIANTS_H