⚡️ Speed up method ReadInstruction.to_spec by 22%

[codeflash-ai]

📄 22% (0.22x) speedup for ReadInstruction.to_spec in src/datasets/arrow_reader.py

⏱️ Runtime : 590 microseconds → 482 microseconds (best of 11 runs)

📝 Explanation and details

The optimized code achieves a 22% runtime improvement (from 590μs to 482μs) through three key optimizations:

1. Early Exit for Simple Cases (Most Impactful)

The original code always performed attribute lookups for splitname, then checked slicing conditions. The optimized version:

• Extracts from_ and to once at the start
• Immediately returns just the split name when both are None, avoiding all subsequent operations
• This benefits the common case where no slicing is specified (see test results: some simple cases show minimal change, but complex cases show 20-30% gains)

2. Reduced Attribute Lookups

The original code accessed rel_instr.from_, rel_instr.to, rel_instr.unit, and rel_instr.rounding multiple times within the loop. The optimized version:

• Caches from_ and to immediately
• Only accesses unit and rounding when needed (inside the else block)
• Line profiler shows these attribute accesses consumed ~14% of total time in the original

3. Streamlined String Building

Instead of building strings incrementally with multiple concatenations (rel_instr_spec += slice_str + rounding_str), the optimized version:

• Uses conditional f-string formatting to build complete strings in one operation
• Pre-computes the is_percent boolean to avoid repeated unit == "%" checks
• Directly appends to the result list within conditional branches

Performance Pattern

Test results show the optimization excels when:

• Multiple slicing parameters are present (20-35% faster): test_to_spec_absolute_unit_from_and_to_and_partial_cases
• Percent-based slicing with rounding (26-31% faster): test_to_spec_percent_unit_with_and_without_rounding
• Large-scale operations with many relative instructions (30.7% faster): 200 instructions processed more efficiently

The optimization has minimal impact on the simplest cases (split name only), which makes sense since those hit the early-exit path with similar efficiency in both versions.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	✅ 48 Passed
🌀 Generated Regression Tests	✅ 931 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	100.0%

⚙️ Click to see Existing Unit Tests

Test File::Test Function	Original ⏱️	Optimized ⏱️	Speedup
test_arrow_reader.py::test_read_instruction_spec	16.0μs	13.2μs	20.6%✅

🌀 Click to see Generated Regression Tests

import pytest  # used for our unit tests
from src.datasets.arrow_reader import ReadInstruction

# function to test

# The following is the original ReadInstruction implementation as provided.
# We include a minimal _RelativeInstruction helper so that ReadInstruction can be instantiated
# and exercised by the tests below. This helper matches the attribute layout used by
# ReadInstruction.to_spec and the other methods under test.
class _RelativeInstruction:
    """Minimal supporting class to mirror the original internal structure expected by ReadInstruction.

    It only stores the attributes that ReadInstruction uses: splitname, from_, to, unit, rounding.
    """
    def __init__(self, splitname, from_, to, unit, rounding):
        self.splitname = splitname
        self.from_ = from_
        self.to = to
        self.unit = unit
        self.rounding = rounding

    def __repr__(self):
        return f"_RelativeInstruction(splitname={self.splitname!r}, from_={self.from_!r}, to={self.to!r}, unit={self.unit!r}, rounding={self.rounding!r})"

def test_to_spec_without_slicing_returns_split_name_and_str_matches():
    # Basic case: no slicing information provided; should return just the split name.
    ri = ReadInstruction("train")  # instantiate with only split_name
    codeflash_output = ri.to_spec() # 1.75μs -> 1.86μs (6.18% slower)

def test_to_spec_absolute_unit_from_and_to_and_partial_cases():
    # Absolute indices: unit other than '%' should not append any unit symbol.
    ri = ReadInstruction("validation", from_=1, to=10, unit="abs")
    # Expect '[1:10]' appended to split name and no rounding string.
    codeflash_output = ri.to_spec() # 3.24μs -> 2.69μs (20.2% faster)

    # Only from_ provided (to is None)
    ri2 = ReadInstruction("subset", from_=5, unit="abs")
    codeflash_output = ri2.to_spec() # 1.55μs -> 1.36μs (13.6% faster)

    # Only to provided (from_ is None)
    ri3 = ReadInstruction("prefix", to=5, unit="abs")
    codeflash_output = ri3.to_spec() # 1.40μs -> 1.15μs (21.6% faster)

def test_to_spec_percent_unit_with_and_without_rounding():
    # Percent unit with default rounding (None): rounding string omitted.
    ri = ReadInstruction("test", rounding=None, from_=0, to=33, unit="%")
    codeflash_output = ri.to_spec() # 3.23μs -> 2.56μs (26.0% faster)

    # Percent unit with explicit 'closest' rounding: rounding is treated as default => omitted.
    ri_closest = ReadInstruction("test", rounding="closest", from_=10, to=20, unit="%")
    codeflash_output = ri_closest.to_spec() # 1.70μs -> 1.51μs (12.6% faster)

    # Percent unit with a non-default rounding should include the rounding in parentheses.
    ri_round = ReadInstruction("test", rounding="pct1_dropremainder", from_=10, to=20, unit="%")
    codeflash_output = ri_round.to_spec() # 1.76μs -> 1.46μs (20.8% faster)

def test_to_spec_handles_none_unit_and_edge_values():
    # If unit is None it should behave like non-percent (no % sign appended).
    ri = ReadInstruction("edge", from_=2, to=3, unit=None)
    codeflash_output = ri.to_spec() # 3.18μs -> 2.35μs (35.6% faster)

    # If both from_ and to are None for the relative instruction, no slice should be appended.
    # We create an instance and then replace its internal relative instructions with one that has None boundaries.
    ri2 = ReadInstruction("shouldstay")
    # Replace internal list with an explicit _RelativeInstruction having no slicing.
    ri2._init([_RelativeInstruction("shouldstay", None, None, None, None)])
    codeflash_output = ri2.to_spec() # 740ns -> 749ns (1.20% slower)

def test_multiple_relative_instructions_and_joining():
    # Construct two RelativeInstructions and set them on a ReadInstruction using _init.
    # This avoids relying on __add__ (which may call other factory methods not available in this test context).
    r1 = _RelativeInstruction("a", 0, 10, "abs", None)
    r2 = _RelativeInstruction("b", 1, 2, "abs", None)
    ri = ReadInstruction("dummy")  # initial value doesn't matter
    # Use the private _init method to supply multiple relative instructions as the original class would.
    ri._init([r1, r2])
    # to_spec should join the two specs with a plus sign.
    codeflash_output = ri.to_spec() # 4.06μs -> 3.51μs (15.6% faster)

def test_add_raises_type_error_and_value_error_for_invalid_adds():
    # Adding a ReadInstruction and a non-ReadInstruction should raise TypeError.
    r1 = ReadInstruction("x")
    with pytest.raises(TypeError) as excinfo:
        _ = r1 + 5  # adding non ReadInstruction is invalid

    # Adding two ReadInstruction with different percent rounding values should raise ValueError.
    r_percent_closest = ReadInstruction("p1", rounding="closest", from_=0, to=10, unit="%")
    r_percent_other = ReadInstruction("p2", rounding="pct1_dropremainder", from_=10, to=20, unit="%")
    # The check that triggers ValueError happens before any attempt to call other factory methods.
    with pytest.raises(ValueError) as excinfo2:
        _ = r_percent_closest + r_percent_other

def test_to_spec_large_scale_many_relative_instructions():
    # Large-scale scenario: assemble a ReadInstruction with many relative instructions (but < 1000).
    # We'll create 200 small entries to ensure performance and string joining behavior.
    count = 200
    pieces = []
    for i in range(count):
        # Create distinct split names and small absolute slices so resulting string is predictable.
        pieces.append(_RelativeInstruction(f"s{i}", i, i + 1, "abs", None))

    ri = ReadInstruction("unused")  # start with a single element
    ri._init(pieces)  # replace with many relative instructions

    codeflash_output = ri.to_spec(); spec = codeflash_output # 133μs -> 102μs (30.7% faster)

def test_repr_contains_readinstruction_and_shows_contents():
    # __repr__ should include the class name and the underlying relative instructions representation.
    ri = ReadInstruction("reprtest", from_=1, to=2, unit="abs")
    r = repr(ri)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

import pytest
from src.datasets.arrow_reader import ReadInstruction

class TestReadInstructionToSpecBasic:
    """Basic test cases for ReadInstruction.to_spec function."""

    def test_simple_split_name_only(self):
        """Test that a simple split name without slicing returns just the split name."""
        instr = ReadInstruction('train')
        codeflash_output = instr.to_spec() # 1.47μs -> 1.52μs (3.55% slower)

    def test_simple_split_name_test(self):
        """Test different split names are correctly returned."""
        instr = ReadInstruction('test')
        codeflash_output = instr.to_spec() # 1.46μs -> 1.36μs (7.52% faster)

    def test_simple_split_name_validation(self):
        """Test various standard split names."""
        for split in ['train', 'test', 'validation', 'val']:
            instr = ReadInstruction(split)
            codeflash_output = instr.to_spec() # 3.18μs -> 3.13μs (1.56% faster)

    def test_absolute_slicing_from_only(self):
        """Test absolute slicing with only 'from_' parameter."""
        instr = ReadInstruction('train', from_=10, unit='abs')
        codeflash_output = instr.to_spec() # 2.60μs -> 2.18μs (19.3% faster)

    def test_absolute_slicing_to_only(self):
        """Test absolute slicing with only 'to' parameter."""
        instr = ReadInstruction('train', to=100, unit='abs')
        codeflash_output = instr.to_spec() # 2.71μs -> 2.24μs (21.3% faster)

    def test_absolute_slicing_from_and_to(self):
        """Test absolute slicing with both 'from_' and 'to' parameters."""
        instr = ReadInstruction('train', from_=10, to=100, unit='abs')
        codeflash_output = instr.to_spec() # 2.88μs -> 2.34μs (23.5% faster)

    def test_percent_slicing_from_only(self):
        """Test percentage slicing with only 'from_' parameter."""
        instr = ReadInstruction('train', from_=10, unit='%')
        codeflash_output = instr.to_spec() # 2.88μs -> 2.39μs (20.9% faster)

    def test_percent_slicing_to_only(self):
        """Test percentage slicing with only 'to' parameter."""
        instr = ReadInstruction('train', to=50, unit='%')
        codeflash_output = instr.to_spec() # 2.87μs -> 2.33μs (23.1% faster)

    def test_percent_slicing_from_and_to(self):
        """Test percentage slicing with both 'from_' and 'to' parameters."""
        instr = ReadInstruction('train', from_=10, to=50, unit='%')
        codeflash_output = instr.to_spec() # 3.08μs -> 2.36μs (30.5% faster)

    def test_percent_slicing_with_closest_rounding(self):
        """Test percentage slicing with 'closest' rounding (default, should not be shown)."""
        instr = ReadInstruction('train', from_=10, to=50, unit='%', rounding='closest')
        codeflash_output = instr.to_spec() # 3.00μs -> 2.50μs (20.4% faster)

    def test_percent_slicing_with_pct1_dropremainder_rounding(self):
        """Test percentage slicing with 'pct1_dropremainder' rounding."""
        instr = ReadInstruction('train', from_=10, to=50, unit='%', rounding='pct1_dropremainder')
        codeflash_output = instr.to_spec() # 3.30μs -> 2.51μs (31.3% faster)

    def test_percent_slicing_with_rounding_from_only(self):
        """Test percentage slicing from only with rounding."""
        instr = ReadInstruction('train', from_=25, unit='%', rounding='pct1_dropremainder')
        codeflash_output = instr.to_spec() # 3.16μs -> 2.47μs (28.1% faster)

    def test_percent_slicing_with_rounding_to_only(self):
        """Test percentage slicing to only with rounding."""
        instr = ReadInstruction('train', to=75, unit='%', rounding='pct1_dropremainder')
        codeflash_output = instr.to_spec() # 3.13μs -> 2.41μs (30.1% faster)

    

To edit these changes git checkout codeflash/optimize-ReadInstruction.to_spec-mlcd4lrz and push.