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Add tests for admission policies
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‎tests/test_admission.py‎

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"""
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Test cases for cache admission in libCacheSim Python bindings.
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This module tests the PluginAdmissioner and existing admission policies
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"""
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import pytest
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from libcachesim import (
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SizeAdmissioner,
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ProbAdmissioner,
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SizeProbabilisticAdmissioner,
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BloomFilterAdmissioner,
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PluginAdmissioner,
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LRU
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)
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from libcachesim.libcachesim_python import (
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Request,
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ReqOp
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)
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class TestSizeAdmissioner:
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"""test existing size admissioner policy"""
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def test_default_configuration(self):
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int64_max = (2 ** 63) - 1
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cache = LRU(
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# Cache size must be large enough to fit the object
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cache_size=int64_max,
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admissioner=SizeAdmissioner()
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)
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# We should be able to admit an item which lies underneath
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# the default threshold of INT64_MAX
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req = Request()
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req.obj_id = 0
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req.obj_size = int64_max - 1
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req.op = ReqOp.OP_GET
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assert cache.can_insert(req)
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# Anything equating to the default threshold should fail
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req = Request()
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req.obj_id = 0
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req.obj_size = int64_max
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req.op = ReqOp.OP_GET
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assert not cache.can_insert(req)
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@pytest.mark.parametrize("thresh", [0, 100, 250, 500, 750, 1000])
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def test_custom_configuration(self, thresh):
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cache = LRU(
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cache_size=1000,
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admissioner=SizeAdmissioner(size_threshold=thresh)
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)
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admits = 0
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# Create 1000 requests of unique sizes and test to see and
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# use `cache_can_insert_default` to run the admissioner
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for i in range(1000):
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req = Request()
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req.obj_id = i
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req.obj_size = i
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req.op = ReqOp.OP_GET
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if cache.can_insert(req):
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admits += 1
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# All items admitted should lie within the size threshold
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assert admits == thresh
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class TestProbAdmissioner:
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"""test existing probabilistic admissioner policy"""
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# Note: The `ProbAdmissioner` does not accept zero as a valid
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# probability, hence we do not test a `admit_nothing` scenario
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def test_admit_all(self):
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cache = LRU(
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# Cache size must be large enough to fit the object
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cache_size=1000,
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admissioner=ProbAdmissioner(prob=1.0)
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)
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# Probability threshold is one, so everything should be
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# admitted unconditionally
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for obj_id in range(1000):
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req = Request()
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req.obj_id = obj_id
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req.obj_size = 1
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req.op = ReqOp.OP_GET
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assert cache.can_insert(req)
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@pytest.mark.parametrize("prob", [0.0001, 0.1, 0.5, 0.9, 0.9999])
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def test_admit_amount(self, prob):
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cache = LRU(
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# Cache size must be large enough to fit the object
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cache_size=1000,
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admissioner=ProbAdmissioner(prob=prob)
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)
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total_requests, admits = 1000, 0
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# Probability threshold is one, so everything should be
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# admitted unconditionally
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for obj_id in range(total_requests):
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req = Request()
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req.obj_id = obj_id
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req.obj_size = 1
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req.op = ReqOp.OP_GET
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if cache.can_insert(req):
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admits += 1
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# This value is not deterministic, hence just perform a
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# basic sanity check to make sure it lies between 0 and 1
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admit_rate = admits / total_requests
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assert 0 <= admit_rate and admit_rate <= 1
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class TestSizeProbabilisticAdmissioner:
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@pytest.mark.parametrize("exponent", [0.0001, 0.1, 0.5, 0.9, 0.9999])
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def test_admit_amount(self, exponent):
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cache = LRU(
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# Cache size must be large enough to fit the object
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cache_size=1000,
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admissioner=SizeProbabilisticAdmissioner(exponent=exponent)
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)
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total_requests, admits = 1000, 0
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# Probability threshold is one, so everything should be
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# admitted unconditionally
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for obj_id in range(total_requests):
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req = Request()
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req.obj_id = obj_id
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req.obj_size = 1
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req.op = ReqOp.OP_GET
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if cache.can_insert(req):
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admits += 1
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# This value is not deterministic, hence just perform a
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# basic sanity check to make sure it lies between 0 and 1
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admit_rate = admits / total_requests
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assert 0 <= admit_rate and admit_rate <= 1
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class TestBloomFilter:
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"""test existing bloomfilter admissioner policy"""
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@pytest.mark.parametrize("visits", [0, 1, 2, 3])
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def test_multi_pass(self, visits):
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cache = LRU(
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cache_size=1000,
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admissioner=BloomFilterAdmissioner()
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)
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admits = 0
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# Here, we try to "see" each item a certain number of times
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# to increment it's "seen_times" count in the bloom filter
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# hash table.
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for _ in range(visits):
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for obj_id in range(1000):
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req = Request()
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req.obj_id = obj_id
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req.obj_size = 1
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req.op = ReqOp.OP_GET
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if cache.can_insert(req):
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cache.insert(req)
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# Next, we check to see if the items were admitted to cache
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for obj_id in range(1000):
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req = Request()
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req.obj_id = obj_id
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req.obj_size = 1
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req.op = ReqOp.OP_GET
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if cache.get(req):
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admits += 1
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# Only if each item is visited more than once should we see
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# that it was admitted to the cache
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expected = 1000 if visits > 1 else 0
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assert admits == expected
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# TODO: Tests crash if we do not explicitly delete the cache object
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class TestPluginAdmissioner:
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"""test PluginAdmissioner using custom simplistic policies"""
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def test_admit_all(self):
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pa = PluginAdmissioner(
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"testAdmissioner",
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lambda: None,
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# Accept all items
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lambda data, req: True,
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lambda: None,
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lambda data, req: None,
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lambda data: None,
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)
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cache = LRU(cache_size=1000, admissioner=pa)
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# Here, we test a basic custom admission policy which
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# should simply accept every single request
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for size in range(1000):
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req = Request()
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req.obj_id = 0
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req.obj_size = size
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req.op = ReqOp.OP_GET
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assert cache.can_insert(req)
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del cache
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def test_admit_nothing(self):
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pa = PluginAdmissioner(
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"testAdmissioner",
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lambda: None,
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# Reject all items
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lambda data, req: False,
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lambda: None,
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lambda data, req: None,
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lambda data: None,
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)
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cache = LRU(cache_size=1000, admissioner=pa)
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# Here, we test a basic custom admission policy which
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# should simply reject every single request
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for size in range(1000):
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req = Request()
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req.obj_id = 0
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req.obj_size = size
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req.op = ReqOp.OP_GET
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assert not cache.can_insert(req)
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del cache
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@pytest.mark.parametrize("thresh", [0, 100, 250, 500, 750, 1000])
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def test_custom_size(self, thresh):
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pa = PluginAdmissioner(
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"testAdmissioner",
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lambda: None,
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# Equivalent to the size admissioner
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lambda data, req: req.obj_size < thresh,
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lambda: None,
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lambda data, req: None,
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lambda data: None,
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)
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cache, admits = LRU(cache_size=1000, admissioner=pa), 0
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# Here, we test a custom implementation of the existing
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# size policy which admits everything under a static size
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# threshold
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for size in range(1000):
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req = Request()
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req.obj_id = 0
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req.obj_size = size
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req.op = ReqOp.OP_GET
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if cache.can_insert(req):
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admits += 1
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# Same correctness criteria as `TestSizeAdmissioner`
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assert admits == thresh
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del cache

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