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export function FlickeringMitigation () {
/////// Inputs ///////
this.growthChangesLength = DEFAULT_LENGTH;
this.totalAvailableArea = NaN;
//begin: internals
this.lastAreaError = NaN;
this.lastGrowth = NaN;
this.growthChanges = [];
this.growthChangeWeights = generateGrowthChangeWeights(this.growthChangesLength); //used to make recent changes weighter than older changes
this.growthChangeWeightsSum = computeGrowthChangeWeightsSum(this.growthChangeWeights);
//end: internals
}
var DEFAULT_LENGTH = 10;
function direction(h0, h1) {
return (h0 >= h1)? 1 : -1;
}
function generateGrowthChangeWeights(length) {
var initialWeight = 3; // a magic number
var weightDecrement = 1; // a magic number
var minWeight = 1;
var weightedCount = initialWeight;
var growthChangeWeights = [];
for (var i=0; i<length; i++) {
growthChangeWeights.push(weightedCount);
weightedCount -= weightDecrement;
if (weightedCount<minWeight) { weightedCount = minWeight; }
}
return growthChangeWeights;
}
function computeGrowthChangeWeightsSum (growthChangeWeights) {
var growthChangeWeightsSum = 0;
for (var i=0; i<growthChangeWeights.length; i++) {
growthChangeWeightsSum += growthChangeWeights[i];
}
return growthChangeWeightsSum;
}
///////////////////////
///////// API /////////
///////////////////////
FlickeringMitigation.prototype.reset = function () {
this.lastAreaError = NaN;
this.lastGrowth = NaN;
this.growthChanges = [];
this.growthChangesLength = DEFAULT_LENGTH;
this.growthChangeWeights = generateGrowthChangeWeights(this.growthChangesLength);
this.growthChangeWeightsSum = computeGrowthChangeWeightsSum(this.growthChangeWeights);
this.totalAvailableArea = NaN;
return this;
};
FlickeringMitigation.prototype.clear = function () {
this.lastAreaError = NaN;
this.lastGrowth = NaN;
this.growthChanges = [];
return this;
};
FlickeringMitigation.prototype.length = function (_) {
if (!arguments.length) { return this.growthChangesLength; }
if (parseInt(_)>0) {
this.growthChangesLength = Math.floor(parseInt(_));
this.growthChangeWeights = generateGrowthChangeWeights(this.growthChangesLength);
this.growthChangeWeightsSum = computeGrowthChangeWeightsSum(this.growthChangeWeights);
} else {
console.warn("FlickeringMitigation.length() accepts only positive integers; unable to handle "+_);
}
return this;
};
FlickeringMitigation.prototype.totalArea = function (_) {
if (!arguments.length) { return this.totalAvailableArea; }
if (parseFloat(_)>0) {
this.totalAvailableArea = parseFloat(_);
} else {
console.warn("FlickeringMitigation.totalArea() accepts only positive numbers; unable to handle "+_);
}
return this;
};
FlickeringMitigation.prototype.add = function (areaError) {
var secondToLastAreaError, secondToLastGrowth;
secondToLastAreaError = this.lastAreaError;
this.lastAreaError = areaError;
if (!isNaN(secondToLastAreaError)) {
secondToLastGrowth = this.lastGrowth;
this.lastGrowth = direction(this.lastAreaError, secondToLastAreaError);
}
if (!isNaN(secondToLastGrowth)) {
this.growthChanges.unshift(this.lastGrowth!=secondToLastGrowth);
}
if (this.growthChanges.length>this.growthChangesLength) {
this.growthChanges.pop();
}
return this;
};
FlickeringMitigation.prototype.ratio = function () {
var weightedChangeCount = 0;
var ratio;
if (this.growthChanges.length < this.growthChangesLength) { return 0; }
if (this.lastAreaError > this.totalAvailableArea/10) { return 0; }
for(var i=0; i<this.growthChangesLength; i++) {
if (this.growthChanges[i]) {
weightedChangeCount += this.growthChangeWeights[i];
}
}
ratio = weightedChangeCount/this.growthChangeWeightsSum;
/*
if (ratio>0) {
console.log("flickering mitigation ratio: "+Math.floor(ratio*1000)/1000);
}
*/
return ratio;
};