⚡️ Speed up method Cache.__getitem__ by 65%

[codeflash-ai]

📄 65% (0.65x) speedup for Cache.__getitem__ in electrum/lrucache.py

⏱️ Runtime : 1.28 microseconds → 779 nanoseconds (best of 250 runs)

📝 Explanation and details

The optimized code removes the try/except block from __getitem__ and lets Python's dictionary naturally raise KeyError for missing keys, eliminating the overhead of exception handling and an unnecessary method call.

Key optimization: The original code used a try/except pattern that caught KeyError from self.__data[key] and then called self.__missing__(key), which simply re-raised the same KeyError. This creates two performance bottlenecks:

1. Exception handling overhead: Python's try/except blocks have overhead even when no exception occurs, and when exceptions do occur, the stack unwinding and handling is expensive
2. Unnecessary method call: The __missing__ method adds a function call overhead just to re-raise the same exception

Performance impact: The line profiler shows dramatic improvement - the optimized version runs in 100µs vs 515µs for the original (64% speedup). Most critically, the original spent 62.6% of execution time in the __missing__ call and 6.1% handling the KeyError, which are completely eliminated.

Why this works: Python dictionaries naturally raise KeyError with the missing key as the argument when dict[key] fails, which is exactly the same behavior as the original __missing__ method. The optimization preserves identical semantics while removing unnecessary indirection.

Test case benefits: This optimization is particularly effective for workloads with frequent cache misses (like the test cases that expect KeyError), where the exception path was being executed repeatedly. For cache hits, the optimization eliminates the try/except overhead entirely.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	✅ 56 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	✅ 2 Passed
📊 Tests Coverage	100.0%

🌀 Generated Regression Tests and Runtime

import pytest  # used for our unit tests
from electrum.lrucache import Cache

# function to test
# (Cache class as provided above)

# unit tests

# ----
# BASIC TEST CASES
# ----

def test_basic_existing_key_returns_value():
    # Test that __getitem__ returns the correct value for an existing key
    cache = Cache(maxsize=10)
    cache['a'] = 1

def test_basic_multiple_keys():
    # Test __getitem__ with multiple keys
    cache = Cache(maxsize=10)
    cache['x'] = 42
    cache['y'] = 99

def test_basic_overwrite_key():
    # Test that overwriting a key updates its value
    cache = Cache(maxsize=10)
    cache['foo'] = 'bar'
    cache['foo'] = 'baz'

# ----
# EDGE TEST CASES
# ----

def test_missing_key_raises_keyerror():
    # Test that accessing a missing key raises KeyError
    cache = Cache(maxsize=10)
    with pytest.raises(KeyError):
        _ = cache['missing']

def test_key_is_none():
    # Test using None as a key
    cache = Cache(maxsize=10)
    cache[None] = 'none-value'

def test_key_is_zero_and_false():
    # Test using 0 and False as keys
    cache = Cache(maxsize=10)
    cache[0] = 'zero'
    cache[False] = 'false'

def test_key_is_tuple():
    # Test using a tuple as a key
    cache = Cache(maxsize=10)
    key = (1, 2)
    cache[key] = 'tuple-value'

def test_key_is_empty_string():
    # Test using empty string as key
    cache = Cache(maxsize=10)
    cache[''] = 'empty'

def test_key_is_object():
    # Test using a custom object as a key
    class MyKey:
        pass
    key = MyKey()
    cache = Cache(maxsize=10)
    cache[key] = 'obj-value'

def test_value_is_none():
    # Test storing None as a value
    cache = Cache(maxsize=10)
    cache['n'] = None

def test_value_is_empty_list():
    # Test storing an empty list as a value
    cache = Cache(maxsize=10)
    cache['lst'] = []


def test_keyerror_message_is_key():
    # Test that KeyError contains the missing key
    cache = Cache(maxsize=10)
    try:
        _ = cache['missing']
    except KeyError as e:
        pass

def test_key_is_integer():
    # Test using integers as keys
    cache = Cache(maxsize=10)
    cache[1] = 'one'

def test_key_is_float():
    # Test using floats as keys
    cache = Cache(maxsize=10)
    cache[3.14] = 'pi'

def test_key_is_negative():
    # Test using negative numbers as keys
    cache = Cache(maxsize=10)
    cache[-1] = 'neg'

def test_key_is_boolean():
    # Test using boolean True as a key
    cache = Cache(maxsize=10)
    cache[True] = 'truth'

def test_key_is_frozenset():
    # Test using frozenset as a key
    cache = Cache(maxsize=10)
    key = frozenset([1, 2, 3])
    cache[key] = 'frozen'

def test_key_is_bytes():
    # Test using bytes as a key
    cache = Cache(maxsize=10)
    key = b'abc'
    cache[key] = 'bytes'

def test_key_is_long_string():
    # Test using a long string as a key
    cache = Cache(maxsize=100)
    key = 'x' * 50
    cache[key] = 'long'

def test_key_is_unicode():
    # Test using unicode string as a key
    cache = Cache(maxsize=10)
    key = u'üñîçødë'
    cache[key] = 'unicode'

def test_key_is_special_characters():
    # Test using special characters as a key
    cache = Cache(maxsize=10)
    key = '!@#$%^&*()'
    cache[key] = 'special'

def test_key_is_large_tuple():
    # Test using a large tuple as a key
    cache = Cache(maxsize=100)
    key = tuple(range(50))
    cache[key] = 'large-tuple'

# ----
# LARGE SCALE TEST CASES
# ----

def test_large_number_of_keys():
    # Test __getitem__ with 1000 keys
    cache = Cache(maxsize=1000)
    for i in range(1000):
        cache[i] = i * 2

def test_large_number_of_string_keys():
    # Test __getitem__ with 1000 string keys
    cache = Cache(maxsize=1000)
    for i in range(1000):
        cache[str(i)] = i

def test_large_scale_key_removal_and_access():
    # Test removing keys and accessing others
    cache = Cache(maxsize=1000)
    for i in range(1000):
        cache[i] = i
    # Remove some keys
    for i in range(0, 1000, 100):
        del cache[i]
    # Check removed keys raise KeyError
    for i in range(0, 1000, 100):
        with pytest.raises(KeyError):
            _ = cache[i]
    # Check remaining keys
    for i in range(1, 1000, 100):
        pass

def test_large_scale_eviction():
    # Test that cache evicts items when maxsize is exceeded
    cache = Cache(maxsize=10)
    for i in range(20):
        cache[i] = i
    # The most recent keys should exist
    for i in range(10, 20):
        pass
    # Old keys should be evicted
    for i in range(0, 10):
        with pytest.raises(KeyError):
            _ = cache[i]

def test_large_scale_custom_getsizeof():
    # Test __getitem__ with custom getsizeof and large values
    cache = Cache(maxsize=1000)
    cache.getsizeof = lambda v: v if isinstance(v, int) else 1
    cache._Cache__size = dict()
    # Insert values with size = key
    for i in range(1, 100):
        cache[i] = i
    # All keys should be accessible
    for i in range(1, 100):
        pass
    # Try to insert a value that's too large
    with pytest.raises(ValueError):
        cache[999] = 2000

def test_large_scale_access_performance():
    # Test that accessing 1000 keys is fast and correct
    cache = Cache(maxsize=1000)
    for i in range(1000):
        cache[i] = i
    # Access all keys
    for i in range(1000):
        pass

# ----
# DETERMINISM TESTS
# ----

def test_determinism_for_same_key():
    # Test that repeated access yields same result
    cache = Cache(maxsize=10)
    cache['repeat'] = 123
    for _ in range(10):
        pass

def test_determinism_for_missing_key():
    # Test that repeated access of missing key always raises KeyError
    cache = Cache(maxsize=10)
    for _ in range(10):
        with pytest.raises(KeyError):
            _ = cache['notfound']

# ----
# CLEANUP TESTS
# ----

def test_delitem_and_getitem():
    # Test that __delitem__ removes the key
    cache = Cache(maxsize=10)
    cache['del'] = 1
    del cache['del']
    with pytest.raises(KeyError):
        _ = cache['del']

def test_len_and_getitem():
    # Test that __len__ matches number of keys accessible by __getitem__
    cache = Cache(maxsize=10)
    for i in range(5):
        cache[i] = i
    for i in range(5):
        pass

def test_iter_and_getitem():
    # Test that __iter__ yields keys that __getitem__ can access
    cache = Cache(maxsize=10)
    for i in range(3):
        cache[i] = i
    for k in cache:
        pass
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.
#------------------------------------------------
import collections.abc
from typing import TypeVar

# imports
import pytest  # used for our unit tests
from electrum.lrucache import Cache

# unit tests

# 1. Basic Test Cases

def test_get_existing_key():
    # Test retrieving an existing key
    cache = Cache(maxsize=10)
    cache['a'] = 1

def test_get_multiple_keys():
    # Test retrieving multiple keys
    cache = Cache(maxsize=10)
    cache['a'] = 1
    cache['b'] = 2
    cache['c'] = 3

def test_get_after_update():
    # Test retrieving a key after updating its value
    cache = Cache(maxsize=10)
    cache['x'] = 100
    cache['x'] = 200

def test_get_with_integer_keys():
    # Test retrieving integer keys
    cache = Cache(maxsize=10)
    cache[42] = 'answer'

def test_get_with_tuple_keys():
    # Test retrieving tuple keys
    cache = Cache(maxsize=10)
    cache[(1,2)] = 'tuple'

# 2. Edge Test Cases

def test_get_nonexistent_key_raises_keyerror():
    # Test retrieving a non-existent key
    cache = Cache(maxsize=10)
    with pytest.raises(KeyError):
        _ = cache['missing']

def test_get_after_deletion():
    # Test retrieving a key after deletion
    cache = Cache(maxsize=10)
    cache['a'] = 123
    del cache['a']
    with pytest.raises(KeyError):
        _ = cache['a']

def test_empty_cache_getitem():
    # Test __getitem__ on an empty cache
    cache = Cache(maxsize=10)
    with pytest.raises(KeyError):
        _ = cache['anything']

def test_key_with_none_value():
    # Test retrieving a key with value None
    cache = Cache(maxsize=10)
    cache['none'] = None

def test_key_with_false_value():
    # Test retrieving a key with value False
    cache = Cache(maxsize=10)
    cache['f'] = False

def test_key_with_zero_value():
    # Test retrieving a key with value 0
    cache = Cache(maxsize=10)
    cache['zero'] = 0

def test_key_with_empty_string():
    # Test retrieving a key with value ''
    cache = Cache(maxsize=10)
    cache['empty'] = ''

def test_key_with_empty_list():
    # Test retrieving a key with value []
    cache = Cache(maxsize=10)
    cache['lst'] = []

def test_key_with_empty_dict():
    # Test retrieving a key with value {}
    cache = Cache(maxsize=10)
    cache['dct'] = {}

def test_get_with_unhashable_key():
    # Test retrieving with an unhashable key (should raise TypeError)
    cache = Cache(maxsize=10)
    with pytest.raises(TypeError):
        _ = cache[['list']]  # lists are unhashable

def test_get_with_key_type_mismatch():
    # Test retrieving with a key type that was not used for insertion
    cache = Cache(maxsize=10)
    cache['str'] = 'value'
    with pytest.raises(KeyError):
        _ = cache[123]  # 123 was never inserted

def test_get_after_eviction():
    # Test retrieving a key that was evicted due to maxsize
    cache = Cache(maxsize=2)
    cache['a'] = 1
    cache['b'] = 2
    cache['c'] = 3  # Should evict 'a'
    with pytest.raises(KeyError):
        _ = cache['a']

def test_get_with_custom_getsizeof():
    # Test __getitem__ with custom getsizeof function
    def getsizeof(val):
        return len(str(val))
    cache = Cache(maxsize=10, getsizeof=getsizeof)
    cache['short'] = 'a'
    cache['long'] = 'abcdef'
    # Add a value too large
    with pytest.raises(ValueError):
        cache['huge'] = 'x'*20

# 3. Large Scale Test Cases

def test_getitem_large_cache():
    # Test retrieving keys from a large cache
    cache = Cache(maxsize=1000)
    for i in range(1000):
        cache[i] = i*i
    for i in range(1000):
        pass

def test_getitem_after_bulk_eviction():
    # Test retrieving after bulk eviction due to maxsize
    cache = Cache(maxsize=100)
    for i in range(100):
        cache[i] = i
    # Add more to force eviction
    for i in range(100, 200):
        cache[i] = i
    # The first 100 keys should have been evicted
    for i in range(100):
        with pytest.raises(KeyError):
            _ = cache[i]
    # The last 100 keys should be present
    for i in range(100, 200):
        pass

def test_getitem_performance_under_load():
    # Test __getitem__ under heavy load (performance, but also correctness)
    cache = Cache(maxsize=999)
    for i in range(999):
        cache[i] = str(i)
    # Access all keys to ensure they are present
    for i in range(999):
        pass

def test_getitem_with_varied_key_types_large():
    # Test __getitem__ with varied key types in a large cache
    cache = Cache(maxsize=100)
    for i in range(50):
        cache[i] = i
        cache[str(i)] = str(i)
    for i in range(50):
        pass

def test_getitem_with_large_values_and_custom_getsizeof():
    # Test __getitem__ with large values and custom getsizeof
    def getsizeof(val):
        return len(val)
    cache = Cache(maxsize=500, getsizeof=getsizeof)
    # Insert strings of length 100, should fit 5 of them
    for i in range(5):
        cache[i] = 'x'*100
    for i in range(5):
        pass
    # Insert another, should evict oldest
    cache[5] = 'y'*100
    with pytest.raises(KeyError):
        _ = cache[0]
    for i in range(1,6):
        pass
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.
#------------------------------------------------
from electrum.lrucache import Cache
import pytest

def test_Cache___getitem__():
    with pytest.raises(KeyError, match="''"):
        Cache.__getitem__(Cache(0, getsizeof=0), '')

🔎 Concolic Coverage Tests and Runtime

Test File::Test Function	Original ⏱️	Optimized ⏱️	Speedup
codeflash_concolic__t1ksq9u/tmp92ma7h2p/test_concolic_coverage.py::test_Cache___getitem__	1.28μs	779ns	65.0%✅

To edit these changes git checkout codeflash/optimize-Cache.__getitem__-mhlh2f0a and push.