Allow branching of simulations

[holgerbrandl]

To enable different trajectories (with controlled randomization), the user may want to branch simulations at a specific time.

Example

// current API 
val sim  : Environment = createSimulation{ 
// define simulation entities here
}

// run it for 100 ticks
sim.run(100)

// inspect some metric (see https://www.kalasim.org/analysis/)
sim.gatherStatistic()


// Pseudocode/Desired API from here on 
val branches : List<Environment> = sim.branch(100)

val branchStats = branches.forEach { it.run(100) }.map{ it.gatherStatistic() }

To do so we must persist the entire graph including koin, monitors, the environment (including its queue) and process states (which are modelled as kotlin.sequences.Sequence iterators). Naturally - by design of kalasim - user-specific code will also leak into the graph to be persisted.

• The feature would also provide means to have file-format for saving/loading simulations
• Such a feature would also prepare for distributed simulation, where simulations are packed and shipped over the network to other compute nodes

Current state
✔️ Framework evaluation -> kryo it is, see evaluation branch https://github.com/holgerbrandl/kalasim/tree/kryoeval
✔️ Persist koin
✔️ Persist main entities and environment
✔️ Deserialize environment including sequence iterators of process definitions (graph looks good and runs up to

kalasim/modules/persistence/src/main/kotlin/Kryo.kt

Line 77 in 9d383e0

val restored = kryo.readClassAndObject(input) as Environment

)
❌ Run deserialized environment--> Fails to run, which boils to sequence iterators being not serializable as of now in https://github.com/holgerbrandl/kryo-kotlin-sam/blob/master/src/main/kotlin/simpleproc/SimpleProc.kt (see Kotlin/kotlinx.coroutines#76 and EsotericSoftware/kryo#867)

[holgerbrandl]

FYI ^^ @arnaudgiuliani and @theigl to give you some context why I had bothered you earlier this week. Thanks again for your great support.

[holgerbrandl]

Also see https://anylogic.help/anylogic/running/snapshots.html