class Indicator(object):
def __init__(self):
self.cms = CMS(5000)
self.hinter_sum = 0
self.hinter_count = 0
self.freqs = Counter() # Alternatively use SpaceSaving
def record(self, key):
hint = self.cms.frequancy(key)
self.hinter_sum += hint
self.hinter_count += 1
self.cms.increment(key)
self.freqs[key] += 1
def get_hint(self):
return self.hinter_sum / self.hinter_count
def est_skew(self):
top_k = [(i, log(k[1]))
for i, k in zip(range(1, 71), self.freqs.most_common(70))]
return -stats.linregress(top_k)[0]
def get_indicator(self):
skew = self.est_skew()
return (self.get_hint() * ((1 - skew**3) if skew < 1 else 0)) / 15.0
def reset(self):
self.hinter_sum = 0
self.hinter_count = 0
self.freqs.clear()
class WTinyLFU(Policy):
def __init__(self, maximum_size, window_percentage=1):
super().__init__(maximum_size)
self.data = {}
self.cms = CMS(maximum_size)
self.sentinel_window = Node() # LRU
self.sentinel_probation = Node() # SLRU
self.sentinel_protected = Node() # SLRU
self.max_window_size = (self.maximum_size * window_percentage) // 100
max_main = self.maximum_size - self.max_window_size
self.max_protected = max_main * 4 // 5
self.size_window = 0
self.size_protected = 0
def record(self, key, size=1):
self.cms.increment(key)
node = self.data.get(key)
if not node:
self.misses += 1
new_node = Node(key, Node.Status.Window)
new_node.append_to_tail(self.sentinel_window)
self.data[key] = new_node
self.size_window += 1
if self.size_window > self.max_window_size:
self.evict()
return False
else:
self.hits += 1
node.remove()
if node.status == Node.Status.Window:
node.append_to_tail(self.sentinel_window)
elif node.status == Node.Status.Probation:
node.status = Node.Status.Protected
node.append_to_tail(self.sentinel_protected)
self.size_protected += 1
self.demote_protected()
elif node.status == Node.Status.Protected:
node.append_to_tail(self.sentinel_protected)
return True
def demote_protected(self):
if self.size_protected > self.max_protected:
demote = self.sentinel_protected.next_node
demote.remove()
demote.status = Node.Status.Probation
demote.append_to_tail(self.sentinel_probation)
self.size_protected -= 1
def evict(self):
candidate = self.sentinel_window.next_node
candidate.remove()
self.size_window -= 1
candidate.status = Node.Status.Probation
candidate.append_to_tail(self.sentinel_probation)
if len(self.data) > self.maximum_size:
victim = self.sentinel_probation.next_node
evicted = victim if self.cms.frequancy(
candidate.data) > self.cms.frequancy(
victim.data) else candidate
del self.data[evicted.data]
evicted.remove()