Build a Festival Crowd Flow Simulator - Step 33

JavaScript
1

Tell us what’s happening:

I have a question about the algorithm of the simulation.

When we move overflow attendees to North gates, We move on to the next tick and do not process them. Wouldn’t it be better to move overflow attendees to North gates of the next tick?

Your code so far

const morningGates = [
  { id: "North", capacity: 5, queue: [3, 6, 2, 4] },
  { id: "East", capacity: 3, queue: [2, 4, 3, 5] },
  { id: "South", capacity: 4, queue: [1, 2, 3, 1] },
  { id: "West", capacity: 2, queue: [4, 1, 2, 3] },
];

const nightGates = [
  { id: "North", capacity: 4, queue: [6, 2, 5, 1] },
  { id: "East", capacity: 2, queue: [3, 3, 4, 2] },
  { id: "South", capacity: 5, queue: [2, 1, 2, 3] },
  { id: "West", capacity: 3, queue: [5, 2, 1, 4] },
];

function initializeThroughput(gates) {
  const summary = {};
  for (const gate of gates) {
    summary[gate.id] = 0;
  };
  return summary;
}

function processGateFlow(gate, tickIndex) {
  let currentTickQueue = gate.queue[tickIndex];
  let processed = 0;
  while (currentTickQueue > 0 && processed < gate.capacity) {
    currentTickQueue--;
    processed++;
  }
  return {
    processed: processed,
    overflow: currentTickQueue
  };
}

function rerouteOverflow(gates, currentGate, tickIndex, overflowAmount) {
  const currentIndex = gates.indexOf(currentGate);
  const nextGateIndex = (currentIndex + 1) % gates.length;
  gates[nextGateIndex].queue[tickIndex] += overflowAmount;
  console.log(
    overflowAmount + " attendees rerouted to " +
    gates[nextGateIndex].id
  );
}

function handleGateAtTick(gates, gate, tickIndex, throughputSummary) {
  console.log("\nProcessing " + gate.id + "...");
  console.log(
    gate.queue[tickIndex] + " attendees arriving."
  );
  const result = processGateFlow(gate, tickIndex);
  throughputSummary[gate.id] += result.processed;
  if (result.overflow > 0) {
    console.log(
      "Overflow of " + result.overflow +
      " attendees. Rerouting..."
    );
    rerouteOverflow(gates, gate, tickIndex, result.overflow);
  }
}

function printSummary(summary) {
  console.log("\nThroughput Summary");
  for (const gateId in summary) {
    console.log(
      gateId + ": " + summary[gateId] +
      " attendees processed"
    );
  }
}

function simulateFestival(gates, timeBlock) {
  console.log("\n" + timeBlock + " Simulation");
  const throughputSummary = initializeThroughput(gates);
  const maxTicks = gates[0].queue.length;
  let tickIndex = 0;
  while (tickIndex < maxTicks) {
    console.log("\nTick " + (tickIndex + 1));
    for (const gate of gates) {
      handleGateAtTick(gates, gate, tickIndex, throughputSummary);
    }
    tickIndex++;
  }
  printSummary(throughputSummary);
}

simulateFestival(morningGates, "Morning");

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Challenge Information:

Build a Festival Crowd Flow Simulator - Step 33

2

This has been bugging me too. We’re “losing” 3 attendees in each simulation as they roll over from West to North. We could re-run processGateFlow when that happens, but I think rejigging rerouteOverflow makes more real world sense so that the overflow of West moves in to the next tick of North. We could do that like this:

function rerouteOverflow(gates, currentGate, tickIndex, overflowAmount) {
  const currentIndex = gates.indexOf(currentGate);
  const nextGateIndex = (currentIndex + 1) % gates.length;
//Checks if last gate in the current tick, and adds overflow to next tick of first gate if so
  if ((currentIndex + 1) % gates.length !== 0) {
    gates[nextGateIndex].queue[tickIndex] += overflowAmount;
  } else {
//An attempt to push the final tick overflow to an additional tick in the first gate's queue...
    if (gates[nextGateIndex].queue.length <= (tickIndex + 1)) {
    gates[nextGateIndex].queue[tickIndex + 1] += overflowAmount;
    } else {
      gates[nextGateIndex].queue.push(overflowAmount);
    }
  }
  console.log(
    overflowAmount + " attendees rerouted to " +
    gates[nextGateIndex].id
  );
}

But then we need to run processGateFlow one more time to mop up the overflow from the last tick run and I can’t get my head round that one just yet. I guess we have to change the while loop in simulateFestival…?