019f8fd211
git-subtree-dir: users/wpcarro git-subtree-mainline:464bbcb15cgit-subtree-split:24f5a642afChange-Id: I6105b3762b79126b3488359c95978cadb3efa789
60 lines
1.4 KiB
Python
60 lines
1.4 KiB
Python
import time
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import random
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from heapq import heappush, heappop
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class Memo(object):
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def __init__(self, size=1):
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"""
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Create a key-value data-structure that will never exceed `size`
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members. Memo evicts the least-recently-accessed elements from itself
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before adding inserting new key-value pairs.
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"""
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if size <= 0:
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raise Exception("We do not support an empty memo")
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self.xs = {}
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self.heap = [(0, None)] * size
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def contains(self, k):
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"""
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Return true if key `k` exists in the Memo.
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"""
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return k in self.xs
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def get(self, k):
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"""
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Return the memoized item at key `k`.
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"""
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# "touch" the element in the heap
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return self.xs[k]
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def set(self, k, v):
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"""
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Memoize value `v` at key `k`.
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"""
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_, to_evict = heappop(self.heap)
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if to_evict != None:
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del self.xs[to_evict]
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heappush(self.heap, (time.time(), k))
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self.xs[k] = v
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memo = Memo(size=10)
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def f(x):
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"""
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Compute some mysterious, expensive function.
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"""
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if memo.contains(x):
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print("Hit.\t\tf({})".format(x))
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return memo.get(x)
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else:
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print("Computing...\tf({})".format(x))
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time.sleep(0.25)
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res = random.randint(0, 10)
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memo.set(x, res)
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return res
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[f(random.randint(0, 10)) for _ in range(10)]
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