A Simple Discrete-Event Simulation: Part 2

Today I’ve added the ability to retrieve the first item from the future events queue, which is the next item to process and that with the lowest activation time. In this case I just update the item’s time when it’s retrieved, then insert it back into the future events queue wherever it belongs. In the example it goes to the end of the queue with a time of 55.

Note that I’ve updated that state values, though I haven’t defined how they’re going to work yet.

I added an update function to the futureEventItem object. I added the functions getFirstItem and insertExistingItem to the futureEventsQueue object. Finally, I added some calls to exercise the new capabilities down at the bottom.

    //global simulation clock
    var globalSimClock = 0.0;  //starts at zero, units to be specified
    var globalSimUnits = "minutes";
    var globalInsertTime = 0.0;
    //events queue item
    function futureEventItem(time,type,entityID,previousState,nextState) {
      this.activationTime = 0.0;
      if (type == "advance") {
        this.activationTime = globalSimClock + time;  //activate 'time' from now
      } else if (type == "absolute") {
        if (time > globalSimClock) {
          this.activationTime = time;                 //activate at specified absolute time, if in future
        } else {
          alert("Invalid time past time supplied.  Entity ID: "+entityID+" Current Time: "+globalSimClock+" Speficied Time: "+time);  //alert on invalid time
        }
      }
      this.entityID = entityID;
      this.previousState = previousState;
      this.nextState = nextState;
      this.getActivationTime = function() {
        return this.activationTime;
      };
      this.update = function(time,type,previousState,nextState) {
        if (type == "advance") {
          this.activationTime = globalSimClock + time;  //activate 'time' from now
        } else if (type == "absolute") {
          if (time > globalSimClock) {
            this.activationTime = time;                 //activate at specified absolute time, if in future
          } else {
            alert("Invalid time past time supplied.  Entity ID: "+this.entityID+" Current Time: "+globalSimClock+" Speficied Time: "+time);  //alert on invalid time
          }
        }
        this.previousState = previousState;
        this.nextState = nextState;
      };
      this.reportItem = function() {
        console.log("Time: "+this.activationTime+" ID: "+this.entityID+" Prev: "+this.previousState+" Next: "+this.nextState);
      };
    };  //futureEventItem
    function futureEventsQueue() {
      this.feq = new Array();
      this.feqSize = 0;
      this.insertTime = 0.0;
      this.findLaterTime = function(item) {
        globalSimClock = 10.0;
        var a = item.getActivationTime();
        var b = globalInsertTime; //this.insertTime;  why is the scope of "this" messed up here?  window and not queue
        var result = a > b;
        return result;
      };
      this.insertItem = function(time,type,entityID,previousState,nextState) {
        //create futureEventItem
        var feqItem = new futureEventItem(time,type,entityID,previousState,nextState);
        this.insertTime = feqItem.getActivationTime();
        globalInsertTime = this.insertTime;
        if (this.feqSize == 0) {  
          this.feq[0] = feqItem;
          this.feqSize++;
          console.log("Array size: "+this.feq.length);
        } else {
          //find index of feq item to insert before
          var insertIndex = this.feq.findIndex(this.findLaterTime);
          //var insertIndex = this.feq.findIndex(this.findLaterTime1);
          //insert the element
          if (insertIndex < 0) {
            insertIndex = this.feq.length;
          }
          this.feq.splice(insertIndex,0,feqItem);
          this.feqSize++;
          console.log("Array size: "+this.feq.length);
        }
      };
      this.getFirstItem = function() {
        globalSimClock = this.feq[0].getActivationTime();
        var feqItem = this.feq.splice(0,1);
        if (feqItem) {
          this.feqSize--;
          return feqItem;
        } else {
          console.log("no items in FEQ to retrieve "+this.feqSize)
        }
      };
      this.insertExistingItem = function(feqItem) {
        this.insertTime = feqItem.getActivationTime();
        globalInsertTime = this.insertTime;
        if (this.feqSize == 0) {  
          this.feq[0] = feqItem;
          this.feqSize++;
          console.log("Array size: "+this.feq.length);
        } else {
          //find index of feq item to insert before
          var insertIndex = this.feq.findIndex(this.findLaterTime);
          //var insertIndex = this.feq.findIndex(this.findLaterTime1);
          //insert the element
          if (insertIndex < 0) {
            insertIndex = this.feq.length;
          }
          this.feq.splice(insertIndex,0,feqItem);
          this.feqSize++;
          console.log("Array size: "+this.feq.length);
        }
      };
      this.reportSize = function() {
        console.log("Number of events in queue: "+this.feqSize);
      };

    };  //futureEventsQueue
    
    function reportItemInfo(element, index, arr) {
      //globalSimClock = 10.0;    
      console.log("reportItemInfo: element: "+element+" index: "+index+" arr: "+arr);
      element.reportItem();
    }
    function findLaterTime1(item) {
      globalSimClock = 10.0;
      return item.getActivationTime() > globalInsertTime;
    };
    
    //initialize future events queue
    feq = new futureEventsQueue();
    feq.reportSize();  //should be zero;
    
    feq.insertItem(40.0,"absolute",333,"prev1","next1");
    feq.feq.forEach(reportItemInfo); 
    feq.reportSize();  //should be 1
    
    globalSimClock = 10.0;
    feq.insertItem(20.0,"advance",444,"prev2","next2");
    feq.feq.forEach(reportItemInfo); 
    feq.reportSize();  //should be 2

    feq.insertItem(50.0,"absolute",555,"prev3","next3");
    feq.feq.forEach(reportItemInfo); 
    feq.reportSize();  //should be 3
    
    //get the first item to process
    var item = feq.getFirstItem();
    feq.feq.forEach(reportItemInfo); 
    feq.reportSize();  //should be 2
    
    //do something to it
    item[0].update(25.0,"advance","prev1a","next1a");
    
    //put it back in the queue
    feq.insertExistingItem(item[0]);
    feq.feq.forEach(reportItemInfo); 
    feq.reportSize();  //should be 3

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//global simulation clock

var globalSimClock = 0.0; //starts at zero, units to be specified

var globalSimUnits = "minutes";

var globalInsertTime = 0.0;

//events queue item

function futureEventItem(time,type,entityID,previousState,nextState) {

this.activationTime = 0.0;

if (type == "advance") {

this.activationTime = globalSimClock + time; //activate 'time' from now

} else if (type == "absolute") {

if (time > globalSimClock) {

this.activationTime = time; //activate at specified absolute time, if in future

} else {

alert("Invalid time past time supplied. Entity ID: "+entityID+" Current Time: "+globalSimClock+" Speficied Time: "+time); //alert on invalid time

}

this.entityID = entityID;

this.previousState = previousState;

this.nextState = nextState;

this.getActivationTime = function() {

return this.activationTime;

};

this.update = function(time,type,previousState,nextState) {

if (type == "advance") {

this.activationTime = globalSimClock + time; //activate 'time' from now

} else if (type == "absolute") {

if (time > globalSimClock) {

this.activationTime = time; //activate at specified absolute time, if in future

} else {

alert("Invalid time past time supplied. Entity ID: "+this.entityID+" Current Time: "+globalSimClock+" Speficied Time: "+time); //alert on invalid time

}

this.previousState = previousState;

this.nextState = nextState;

};

this.reportItem = function() {

console.log("Time: "+this.activationTime+" ID: "+this.entityID+" Prev: "+this.previousState+" Next: "+this.nextState);

};

}; //futureEventItem

function futureEventsQueue() {

this.feq = new Array();

this.feqSize = 0;

this.insertTime = 0.0;

this.findLaterTime = function(item) {

globalSimClock = 10.0;

var a = item.getActivationTime();

var b = globalInsertTime; //this.insertTime; why is the scope of "this" messed up here? window and not queue

var result = a > b;

return result;

};

this.insertItem = function(time,type,entityID,previousState,nextState) {

//create futureEventItem

var feqItem = new futureEventItem(time,type,entityID,previousState,nextState);

this.insertTime = feqItem.getActivationTime();

globalInsertTime = this.insertTime;

if (this.feqSize == 0) {

this.feq[0] = feqItem;

this.feqSize++;

console.log("Array size: "+this.feq.length);

} else {

//find index of feq item to insert before

var insertIndex = this.feq.findIndex(this.findLaterTime);

//var insertIndex = this.feq.findIndex(this.findLaterTime1);

//insert the element

if (insertIndex < 0) {

insertIndex = this.feq.length;

}

this.feq.splice(insertIndex,0,feqItem);

this.feqSize++;

console.log("Array size: "+this.feq.length);

}

};

this.getFirstItem = function() {

globalSimClock = this.feq[0].getActivationTime();

var feqItem = this.feq.splice(0,1);

if (feqItem) {

this.feqSize--;

return feqItem;

} else {

console.log("no items in FEQ to retrieve "+this.feqSize)

}

};

this.insertExistingItem = function(feqItem) {

this.insertTime = feqItem.getActivationTime();

globalInsertTime = this.insertTime;

if (this.feqSize == 0) {

this.feq[0] = feqItem;

this.feqSize++;

console.log("Array size: "+this.feq.length);

} else {

//find index of feq item to insert before

var insertIndex = this.feq.findIndex(this.findLaterTime);

//var insertIndex = this.feq.findIndex(this.findLaterTime1);

//insert the element

if (insertIndex < 0) {

insertIndex = this.feq.length;

}

this.feq.splice(insertIndex,0,feqItem);

this.feqSize++;

console.log("Array size: "+this.feq.length);

}

};

this.reportSize = function() {

console.log("Number of events in queue: "+this.feqSize);

};

}; //futureEventsQueue

function reportItemInfo(element, index, arr) {

//globalSimClock = 10.0;

console.log("reportItemInfo: element: "+element+" index: "+index+" arr: "+arr);

element.reportItem();

}

function findLaterTime1(item) {

globalSimClock = 10.0;

return item.getActivationTime() > globalInsertTime;

};

//initialize future events queue

feq = new futureEventsQueue();

feq.reportSize(); //should be zero;

feq.insertItem(40.0,"absolute",333,"prev1","next1");