modelverse/integration/code/pn_simulate.alc

include "primitives.alh"
include "modelling.alh"
include "random.alh"

Element function simulate(inputs : Element):
    Element outputs
    outputs = create_node()

    // Copy over the model to the output dictionary
    dict_add(outputs, "models/PetriNets_Runtime", model_copy(inputs["models/PetriNets_Runtime"))

    // Do a single simulation step
    Element model
    model = outputs["models/PetriNets_Runtime"]

    // Find enabled transitions
    Element all_transitions
    Element enabled_transitions
    String under_study
    Boolean enabled
    Element in_arcs

    all_transitions = allInstances(model, "Transition")
    enabled_transitions = create_node()

    while (0 < read_nr_out(all_transitions)):
        under_study = set_pop(all_transitions)
        enabled = True

        // Find all incoming transitions
        in_arcs = allIncomingAssociationInstances(model, under_study, "P2T")

        while (0 < read_nr_out(in_arcs)):
            arc_under_study = set_pop(in_arcs)

            Integer present_tokens
            Integer required_tokens
            required_tokens = read_attribute(model, arc_under_study, "weight")
            log("Weight: " + cast_i2s(required_tokens))
            present_tokens = read_attribute(model, reverseKeyLookup(model["model"], read_edge_src(model["model"][arc_under_study])), "tokens")
            log("Tokens: " + cast_i2s(present_tokens))
            if (present_tokens < required_tokens):
                // Less tokens than required, so disable the transition completely
                enabled = False

        if (enabled):
            set_add(enabled_transitions, under_study)

    // Pick random enabled transition
    String transition

    transition = random_choice(enabled_transitions)

    // Consume tokens
    Element workset
    String working_arc
    String working_place
    Integer new_value

    workset = allIncomingAssociationInstances(model, transition, "P2T")
    while (0 < read_nr_out(workset)):
        working_arc = set_pop(workset)
        working_place = reverseKeyLookup(model["model"], read_edge_src(model["model"][working_arc]))
        new_value = integer_subtraction(read_attribute(model, working_place, "tokens"), read_attribute(model, working_arc, "weight"))
        instantiate_attribute(model, working_place, "tokens", new_value)

    // Add tokens
    workset = allOutgoingAssociationInstances(model, transition, "T2P")
    while (0 < read_nr_out(workset)):
        working_arc = set_pop(workset)
        working_place = reverseKeyLookup(model["model"], read_edge_dst(model["model"][working_arc]))
        new_value = integer_addition(read_attribute(model, working_place, "tokens"), read_attribute(model, working_arc, "weight"))
        instantiate_attribute(model, working_place, "tokens", new_value)

    // Finish up
    return outputs!