SimulationKit

A package for simulating economic models

Architecture

Simulations are modeled using discrete events. Each entity has a corresponding set of events.

Generic Simulation Entities

• Conceptual Model: specifies entities and events
• Simulation: calculates results of a simulation run
• StateGenerator: creates initial state and initial set of events based on plan in conceptual model
• Run: results from a particular simulation calculation
• Simulator: constructs executable model, executes model logic, collects and collates results
• Period: single iteration of the simulators execution of the executable model
• Clock: source of truth for the current period of the currently executing simulation
• Tick: timestamped value of what the current time is
• Step: single iteration of a simulation
• Simulation.State : The state of the simulation at some step
• Simulation.Event: A single event recorded at a particular time period

Domain Specific Entities

• Ledger: consists of one or more accounts and corresponds to an economic entity
• Ledger event: a change in one or more accounts in the ledger
• Bank: an entity that can take deposits and make loans
• Bank event: a change in the bank state
• Accounts
  • Asset: something that has economic value now or in the future
  • Liability: an obligation associated with an economic cost now or in the future
  • Equity: residual value
  • Income: money received through work or investments
  • Expense: money paid out to satisfy an obligation or in exchange for something of value

General Workflows

Simulation Lifecycle

1. Construct Conceptual Model
2. Convert Conceptual Model into Executable Model
3. Generate a Run using Executable Model

2 is a function: ConceptualModel -> ExecutableModel 3 is a function: ExecutableModel -> Run

• A simulation is run over a fixed number of time periods. Each time period is represented by a tick on a simulator Clock.
• Each run gets its own separate clock.
• A clock is used to timestamp a point that goes onto a time series.
• The collected time series are specified by an operational historian

TODOs

• Consistency between Simulation events and Bank/Ledger events
• Allow stochastic simulation results
• Make Simulation construction more generic
  • Generic entities and events
  • Entity identity
• Record simulation statistics
• Support 5 basic account types
  • Assets
  • Liabilities
  • Owners' Equity
  • Revenue
  • Expense
• Bank account openings
• Bank account closures
• Separate ledgers for each bank account
• Deposit interest accrual
• Loan interest accrual
• Bank account withdrawls
• Bank account transfers
• Add CentralBank to set policy risk-free rate
• Compute bank loan interest with spread against risk-free rate
• Per-borrower loan interest spreads
• Add Company economic agent
• Add Household economic agent
• Add utility calculations
• Add intertemporal decision-making