public void SizeIncrementsIfYouAddItemsToCacheThatIsNotFull()
{
var capacity = 100;
var cache = new PseudoLRUCache <string>(capacity);
Assert.AreEqual(0, cache.Size);
cache.Add("item1");
Assert.AreEqual(1, cache.Size);
cache.Add("item2");
Assert.AreEqual(2, cache.Size);
}
public void CacheHitRatioCase(int n, double cacheSizePercentage, double alpha, double expectedHitRate, int maxTrials)
{
var zipf = new ZipfDistribution(n, alpha, 10, 0.0001);
var capacity = (int)(n * cacheSizePercentage / 100);
var cache = new PseudoLRUCache <string>(capacity);
var allItems = new PseudoLRUCache <string> .CacheItem[n + 1];
var rankHistogram = new int[n + 1];
for (var trial = 0; trial < maxTrials; trial++)
{
var rank = zipf.NextRandomRank();
if (allItems[rank] == null)
{
allItems[rank] = cache.Add(rank.ToString());
}
else
{
allItems[rank].GetOrCreate(() => rank.ToString());
}
rankHistogram[rank]++;
}
Console.WriteLine($"The Hit Ratio is {cache.HitRatio}; hoped for {expectedHitRate}");
var histogram = "Rank Histogram for first 100 items\n";
var cumePct = 0.0;
for (var rank = 1; rank <= 100; rank++)
{
var pct = 100.0 * rankHistogram[rank] / (double)maxTrials;
cumePct += pct;
histogram += $"{rank} chosen {rankHistogram[rank]} times ({pct}%, {cumePct}% cume)\n";
}
Console.WriteLine(histogram);
Assert.GreaterOrEqual(cache.HitRatio, expectedHitRate, $"Cache Hit Ratio is lower than expected: {cache.HitRatio} < {expectedHitRate}");
}
public void NoItemsEvictedWhenAddingToCacheThatsNotNotFull()
{
var capacity = 100;
var cache = new PseudoLRUCache <string>(capacity);
var items = new List <PseudoLRUCache <string> .CacheItem>();
for (var i = 1; i <= capacity; i++)
{
items.Add(cache.Add(i.ToString()));
var notCachedCount = items.Count(item => !item.IsCached);
Assert.IsTrue(notCachedCount == 0, $"{notCachedCount} items are not cached after adding {i}.");
}
}
public void ResizingFullCacheAboveSizeEvictsNoItems()
{
var capacity = 100;
var cache = new PseudoLRUCache <string>(capacity);
var items = new List <PseudoLRUCache <string> .CacheItem>();
for (var i = 1; i <= capacity; i++)
{
items.Add(cache.Add(i.ToString()));
}
Assert.IsTrue(cache.IsFull, "Before Resize, cache should be full");
cache.Resize(110);
Assert.IsFalse(cache.IsFull, "After Resize, cache should NOT be full");
var actualEjectedCount = items.Count(i => !i.IsCached);
var expectedEjectedCount = 0;
Assert.AreEqual(expectedEjectedCount, actualEjectedCount, $"Should have ejected {expectedEjectedCount}, instead {actualEjectedCount}");
}
public void OneItemEvictedWhenAddingToFullCache()
{
var capacity = 100;
var cache = new PseudoLRUCache <string>(capacity);
var items = new List <PseudoLRUCache <string> .CacheItem>();
for (var i = 1; i <= capacity + 1; i++)
{
items.Add(cache.Add(i.ToString()));
var notCachedCount = items.Count(item => !item.IsCached);
if (i <= capacity)
{
Assert.IsFalse(cache.IsEmpty, $"Cache thinks it is empty when it is not, for i = {i}.");
Assert.AreEqual(i >= capacity, cache.IsFull, $"Cache IsFull = {cache.IsFull} for i = {i}.");
Assert.IsTrue(notCachedCount == 0, $"{notCachedCount} items are not cached after adding {i} when cache is NOT FULL.");
}
else
{
Assert.IsTrue(cache.IsFull, $"Cache thinks it is not full when i = {i}.");
Assert.IsTrue(notCachedCount == 1, $"{notCachedCount} items are not cached after adding {i} when cache IS FULL.");
}
}
}