Parallel Simulation: to run multiple simulations and leverage multiple CPUs

To provide a better performance in simulation, SimQN provides a method to create multiple processes and make full use of multiple CPUs. To do so, users needs to create a sub-class of MPSimulations and overwrite run method to tell SimQN how to perform a single experiment.

The input parameter of run method, is a directory that contains all input variables, e.g., {"nodes_number": 5, "delay": 0.05, "memory_capacity": 10, "send_rate": 10}, and the output is another directory containing all experiment results, e.g., {"throughput": 10, "fidelity": 0.88}. Here is an example of how to build a MPSimulations:

from qns.utils.multiprocess import MPSimulations
from import DijkstraRouteAlgorithm
from import ClassicTopology
from qns.simulator.simulator import Simulator
from import QuantumNetwork
from import LineTopology
from import EntanglementDistributionApp

class EPRDistributionSimulation(MPSimulations):
    def run(self, setting):

        # get input variables
        nodes_number = setting["nodes_number"]
        delay = setting["delay"]
        memory_capacity = setting["memory_capacity"]
        send_rate = setting["send_rate"]

        # do the experiments
        s = Simulator(0, 10, accuracy=10000000)
        topo = LineTopology(nodes_number=nodes_number,
                            qchannel_args={"delay": delay, "drop_rate": 0.3},
                            cchannel_args={"delay": delay},
                                "capacity": memory_capacity,
                                "store_error_model_args": {"a": 0.2}},

        net = QuantumNetwork(
            topo=topo, classic_topo=ClassicTopology.All, route=DijkstraRouteAlgorithm())

        src = net.get_node("n1")
        dst = net.get_node(f"n{nodes_number}")
        net.add_request(src=src, dest=dst, attr={"send_rate": send_rate})

        # form the result
        return {"count": src.apps[0].success_count}

Now, the EPRDistributionSimulation can be initiated by the following input parameters:

  • settings, a directory that contains all simulation variables. For example:

    "nodes_number": [5, 10, 15, 20],
    "delay": [0.05],
    "memory_capacity": [10, 20],
    "send_rate": [10, 20]

It contains are four input variables, and the input parameter of each simulation will be the combination of all these four variables, e.g., {"nodes_number": 5, "delay": 0.05, "memory_capacity": 10, "send_rate": 10}.

  • iter_count, the number of repeat experiments for each setting. If iter_count is 10, it means that the experiments will run for 10 times for each input variable combination.

  • aggregate, it is a boolean indicates whether to aggregate the results for the repeated simulations in a same input variable. If iter_count > 1, and aggregate is True, SimQN will aggregate the 10 results for each setting, and calculate the mean and std for every outputs.

  • cores, the number of processes. By default, SimQN will use all CPUs in this machine. For example, if cores = 1, SimQN will run in a single process mode.

  • name, the name of this simulation.

For example:

ss = EPRDistributionSimulation(settings={
    "nodes_number": [5, 10, 15, 20],
    "delay": [0.05],
    "memory_capacity": [10, 20],
    "send_rate": [10, 20]
}, aggregate=True, iter_count=10, cores=4)

Finally, users can start the simulation and get the experiment results:

# start the simulation

# get the aggregated result (calculate the mean and std for every output variables).

# get the raw data