⚡️ Speed up function _cached_joined by 8%

[codeflash-ai]

📄 8% (0.08x) speedup for _cached_joined in code_to_optimize/code_directories/simple_tracer_e2e/workload.py

⏱️ Runtime : 112 milliseconds → 104 milliseconds (best of 42 runs)

📝 Explanation and details

Here’s an optimized version of your program.

Key improvements:

• Replace map(str, range(number)) with a list comprehension and use " ".join(str(i) for i in range(number)). In CPython 3.11, both are close in speed, but since you want maximum speed and minimal memory per call, it actually pays off to use a preallocated list of strings (avoiding the generator overhead).
• Switching the cache from functools.lru_cache to a simple fixed-size array cache (since the range is known and contiguous) yields a major speedup—O(1) lookup with no hashing.
• Avoid all global per-call function overheads by not using decorators.
• If you want to preserve the exact signature and decorator-based cache, skip the array cache.

Here’s the faster version:

Notes:

• This eliminates LRU cache overhead (hashing, dict lookup, reference management).
• For all subsequent calls, lookup is instant: O(1) list access.
• List comprehension is slightly faster than map due to the avoidance of Python-level function calls per element.

If you must preserve the use of @lru_cache for API compatibility:
Your code is already quite optimal. Minor tweak (list comprehension).

But the first method above is substantially faster/more memory efficient if your input domain is tightly bounded as assumed.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	✅ 3072 Passed
⏪ Replay Tests	✅ 3 Passed
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	100.0%

🌀 Generated Regression Tests and Runtime

from functools import lru_cache

# imports
import pytest  # used for our unit tests
from workload import _cached_joined

# unit tests

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

def test_zero_returns_empty_string():
    """Test that input 0 returns an empty string (no numbers to join)."""
    codeflash_output = _cached_joined(0) # 2.05μs -> 1.87μs (9.66% faster)

def test_one_returns_zero():
    """Test that input 1 returns '0' (range(1) == [0])."""
    codeflash_output = _cached_joined(1) # 2.34μs -> 2.15μs (8.87% faster)

def test_two_returns_zero_one():
    """Test that input 2 returns '0 1'."""
    codeflash_output = _cached_joined(2) # 2.36μs -> 2.20μs (7.26% faster)

def test_small_number():
    """Test a small number, e.g., 5."""
    codeflash_output = _cached_joined(5) # 2.43μs -> 2.44μs (0.409% slower)

def test_typical_number():
    """Test a typical number, e.g., 10."""
    codeflash_output = _cached_joined(10) # 2.88μs -> 2.77μs (3.64% faster)

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

def test_negative_number_raises():
    """Test that negative input raises ValueError (range(-1) is empty, but let's enforce positive numbers)."""
    # The original function does not raise, but we want to ensure the test suite would catch mutation.
    # However, since the function as written does not raise, let's test for correct output (empty string).
    codeflash_output = _cached_joined(-1) # 1.91μs -> 1.48μs (29.0% faster)

def test_large_number_near_cache_limit():
    """Test the function near the cache size limit."""
    n = 1000
    codeflash_output = _cached_joined(n); result = codeflash_output # 77.7μs -> 72.5μs (7.10% faster)

def test_input_is_float():
    """Test that float input raises TypeError."""
    with pytest.raises(TypeError):
        _cached_joined(5.5)

def test_input_is_string():
    """Test that string input raises TypeError."""
    with pytest.raises(TypeError):
        _cached_joined("10")

def test_input_is_none():
    """Test that None input raises TypeError."""
    with pytest.raises(TypeError):
        _cached_joined(None)

def test_input_is_bool():
    """Test that boolean input acts as integer (False=0, True=1)."""
    codeflash_output = _cached_joined(False) # 2.21μs -> 1.77μs (24.9% faster)
    codeflash_output = _cached_joined(True) # 1.51μs -> 1.46μs (3.42% faster)

def test_cache_eviction():
    """Test that the cache does not grow unbounded (LRU)."""
    # Fill the cache with 1001 unique values
    for i in range(1000):
        _cached_joined(i)
    # The next call should evict the oldest cache entry
    _cached_joined(1001)

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

def test_large_scale_output_correctness():
    """Test correctness for a large n (n=999)."""
    n = 999
    codeflash_output = _cached_joined(n); result = codeflash_output # 81.9μs -> 76.0μs (7.71% faster)
    # Check that the result has the correct number of numbers
    numbers = result.split(" ")

def test_performance_large_input(monkeypatch):
    """Test that the function completes quickly for n=999."""
    import time
    n = 999
    start = time.time()
    _cached_joined(n)
    duration = time.time() - start

def test_cache_performance():
    """Test that repeated calls for the same input use the cache."""
    n = 500
    _cached_joined.cache_clear()
    # First call (not cached)
    import time
    start = time.time()
    _cached_joined(n)
    uncached_duration = time.time() - start
    # Second call (should be cached)
    start = time.time()
    _cached_joined(n)
    cached_duration = time.time() - start

def test_all_outputs_unique():
    """Test that outputs for different n are unique and correct."""
    seen = set()
    for n in range(10):
        codeflash_output = _cached_joined(n); output = codeflash_output
        seen.add(output)
        # Check that output is correct
        expected = " ".join(str(i) for i in range(n))

def test_output_no_trailing_space():
    """Test that output does not have trailing or leading spaces."""
    for n in [0, 1, 10, 100]:
        codeflash_output = _cached_joined(n); output = codeflash_output

# --------------------
# ADDITIONAL EDGE CASES
# --------------------

def test_large_input_string_length():
    """Test that the output string length is as expected for large n."""
    n = 1000
    codeflash_output = _cached_joined(n); result = codeflash_output # 81.6μs -> 76.2μs (7.09% faster)
    # The length should be sum of len(str(i)) for i in range(n) plus n-1 spaces
    expected_length = sum(len(str(i)) for i in range(n)) + (n - 1 if n > 0 else 0)

def test_mutation_detection():
    """Test that mutation (e.g., off-by-one error) is detected."""
    # If the function returns ' '.join(str(i) for i in range(number+1)), this will fail
    n = 5
    codeflash_output = _cached_joined(n) # 2.52μs -> 2.52μs (0.000% faster)
    codeflash_output = _cached_joined(n+1) # 1.20μs -> 1.37μs (12.5% slower)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

from functools import lru_cache

# imports
import pytest  # used for our unit tests
from workload import _cached_joined

# unit tests

# ----------------
# Basic Test Cases
# ----------------

def test_zero():
    # 0 should return an empty string (no numbers to join)
    codeflash_output = _cached_joined(0) # 1.90μs -> 1.56μs (21.8% faster)

def test_one():
    # 1 should return just "0"
    codeflash_output = _cached_joined(1) # 2.15μs -> 1.99μs (8.02% faster)

def test_two():
    # 2 should return "0 1"
    codeflash_output = _cached_joined(2) # 2.27μs -> 2.16μs (5.13% faster)

def test_small_number():
    # 5 should return "0 1 2 3 4"
    codeflash_output = _cached_joined(5) # 2.52μs -> 2.38μs (5.45% faster)

def test_typical_number():
    # 10 should return "0 1 2 3 4 5 6 7 8 9"
    codeflash_output = _cached_joined(10) # 3.04μs -> 2.81μs (8.20% faster)

# ----------------
# Edge Test Cases
# ----------------

def test_negative_number():
    # Negative numbers should return an empty string (range is empty)
    codeflash_output = _cached_joined(-1) # 1.73μs -> 1.49μs (16.1% faster)
    codeflash_output = _cached_joined(-100) # 932ns -> 801ns (16.4% faster)

def test_large_single_digit():
    # 9 should return "0 1 2 3 4 5 6 7 8"
    codeflash_output = _cached_joined(9) # 2.88μs -> 2.73μs (5.12% faster)

def test_number_is_string():
    # Should raise TypeError if input is not an integer
    with pytest.raises(TypeError):
        _cached_joined("10")
    with pytest.raises(TypeError):
        _cached_joined(None)
    with pytest.raises(TypeError):
        _cached_joined(5.5)

def test_number_is_bool():
    # True is 1, False is 0 in Python
    codeflash_output = _cached_joined(True) # 2.38μs -> 2.17μs (9.20% faster)
    codeflash_output = _cached_joined(False) # 1.17μs -> 982ns (19.3% faster)

def test_number_is_large_negative():
    # Very large negative number should return empty string
    codeflash_output = _cached_joined(-999) # 1.68μs -> 1.41μs (19.1% faster)

def test_number_is_zero_again():
    # Check repeated call for caching and correctness
    codeflash_output = _cached_joined(0) # 1.70μs -> 1.40μs (21.5% faster)

def test_mutation_detection():
    # Ensure that the output is correct and not off-by-one or reversed
    codeflash_output = _cached_joined(3) # 2.36μs -> 2.28μs (3.50% faster)
    # Should not be "1 2 3" or "2 1 0"
    codeflash_output = _cached_joined(3) # 280ns -> 250ns (12.0% faster)
    codeflash_output = _cached_joined(3) # 161ns -> 160ns (0.625% faster)

def test_cache_eviction():
    # Test that the cache works for boundary values (not strictly testable, but call a lot of distinct inputs)
    for i in range(1000):
        codeflash_output = _cached_joined(i); result = codeflash_output
        # The result should always be the numbers from 0 to i-1, joined by spaces
        expected = " ".join(str(x) for x in range(i))

# ----------------------
# Large Scale Test Cases
# ----------------------

def test_large_number_just_under_limit():
    # Test the function with a large number (999)
    n = 999
    codeflash_output = _cached_joined(n); result = codeflash_output # 78.1μs -> 72.9μs (7.19% faster)
    expected = " ".join(str(x) for x in range(n))

def test_large_number_at_limit():
    # Test the function with the maximum cache size (1000)
    n = 1000
    codeflash_output = _cached_joined(n); result = codeflash_output # 78.1μs -> 73.4μs (6.43% faster)
    expected = " ".join(str(x) for x in range(n))

def test_large_number_performance():
    # This test checks that the function can handle large input efficiently
    n = 1000
    codeflash_output = _cached_joined(n); result = codeflash_output # 81.3μs -> 74.6μs (8.94% faster)
    # The first and last elements should be "0" and "999"
    split_result = result.split()

def test_cache_reuse():
    # Test that repeated calls with the same argument return the same result (cache hit)
    codeflash_output = _cached_joined(100); r1 = codeflash_output # 9.94μs -> 9.75μs (1.94% faster)
    codeflash_output = _cached_joined(100); r2 = codeflash_output # 280ns -> 231ns (21.2% faster)

def test_non_mutating_output():
    # Ensure the output is not mutated by subsequent calls
    codeflash_output = _cached_joined(10); s1 = codeflash_output # 2.75μs -> 2.83μs (2.83% slower)
    codeflash_output = _cached_joined(5); s2 = codeflash_output # 1.27μs -> 1.25μs (1.52% faster)

def test_all_numbers_unique():
    # For a given n, the output should contain all unique numbers from 0 to n-1
    n = 100
    codeflash_output = _cached_joined(n); result = codeflash_output # 9.87μs -> 9.52μs (3.70% faster)
    numbers = result.split()

def test_no_trailing_space():
    # The output should not have a trailing space
    for n in [1, 10, 100, 1000]:
        codeflash_output = _cached_joined(n); result = codeflash_output

def test_no_leading_space():
    # The output should not have a leading space
    for n in [1, 10, 100, 1000]:
        codeflash_output = _cached_joined(n); result = codeflash_output

def test_empty_string_for_zero_and_negative():
    # Both zero and negative numbers should return an empty string
    codeflash_output = _cached_joined(0) # 1.72μs -> 1.55μs (10.9% faster)
    codeflash_output = _cached_joined(-1) # 871ns -> 811ns (7.40% faster)
    codeflash_output = _cached_joined(-1000) # 661ns -> 601ns (9.98% faster)

def test_cache_size_limit():
    # Fill the cache with maxsize+1 distinct inputs and ensure all results are correct
    for n in range(1000):
        codeflash_output = _cached_joined(n); result = codeflash_output # 74.9μs -> 68.9μs (8.60% faster)
        expected = " ".join(str(x) for x in range(n))
    # Now call with a new value (1001) and check correctness
    codeflash_output = _cached_joined(1001); result = codeflash_output
    expected = " ".join(str(x) for x in range(1000))
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

To edit these changes git checkout codeflash/optimize-_cached_joined-mccv8qo4 and push.