40 lines
1.2 KiB
Python
40 lines
1.2 KiB
Python
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#!/usr/bin/env python
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# Copyright 2020 the V8 project authors. All rights reserved.
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# Use of this source code is governed by a BSD-style license that can be
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# found in the LICENSE file.
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import heapq
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import random
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class FixedSizeTopList():
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"""Utility collection for gathering a fixed number of elements with the
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biggest value for the given key. It employs a heap from which we pop the
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smallest element when the collection is 'full'.
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If you need a reversed behaviour (collect min values) just provide an
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inverse key."""
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def __init__(self, size, key=None):
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self.size = size
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self.key = key or (lambda x: x)
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self.data = []
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self.discriminator = 0
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def add(self, elem):
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elem_k = self.key(elem)
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heapq.heappush(self.data, (elem_k, self.extra_key(), elem))
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if len(self.data) > self.size:
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heapq.heappop(self.data)
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def extra_key(self):
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# Avoid key clash in tuples sent to the heap.
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# We want to avoid comparisons on the last element of the tuple
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# since those elements might not be comparable.
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self.discriminator += 1
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return self.discriminator
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def as_list(self):
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original_data = [rec for (_, _, rec) in self.data]
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return sorted(original_data, key=self.key, reverse=True)
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