⚡️ Speed up function get_bbox_thickness by 1,267%

[misrasaurabh1]

📄 1,267% (12.67x) speedup for get_bbox_thickness in unstructured/partition/pdf_image/analysis/bbox_visualisation.py

⏱️ Runtime : 5.01 milliseconds → 367 microseconds (best of 250 runs)

📝 Explanation and details

The optimization replaces np.polyfit with direct linear interpolation, achieving a 13x speedup by eliminating unnecessary computational overhead.

Key Optimization:

• Removed np.polyfit: The original code used NumPy's polynomial fitting for a simple linear interpolation between two points, which is computationally expensive
• Direct linear interpolation: Replaced with manual slope calculation: slope = (max_value - min_value) / (ratio_for_max_value - ratio_for_min_value)

Why This is Faster:

• np.polyfit performs general polynomial regression using least squares, involving matrix operations and SVD decomposition - overkill for two points
• Direct slope calculation requires only basic arithmetic operations (subtraction and division)
• Line profiler shows the np.polyfit line consumed 91.7% of execution time (10.67ms out of 11.64ms total)

Performance Impact:
The function is called from draw_bbox_on_image which processes bounding boxes for PDF image visualization. Since this appears to be in a rendering pipeline that could process many bounding boxes per page, the 13x speedup significantly improves visualization performance. Test results show consistent 12-13x improvements across all scenarios, from single bbox calls (~25μs → ~2μs) to batch processing of 100 random bboxes (1.6ms → 116μs).

Optimization Benefits:

• Small bboxes: 1329% faster (basic cases)
• Large bboxes: 1283% faster
• Batch processing: 1297% faster for 100 random bboxes
• Scale-intensive workloads: 1341% faster for processing 1000+ bboxes

This optimization is particularly valuable for PDF processing workflows where many bounding boxes need thickness calculations for visualization.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	✅ 8 Passed
🌀 Generated Regression Tests	✅ 285 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	100.0%

⚙️ Existing Unit Tests and Runtime

Test File::Test Function	Original ⏱️	Optimized ⏱️	Speedup
partition/pdf_image/test_analysis.py::test_get_bbox_thickness	75.5μs	5.58μs	1252%✅

🌀 Generated Regression Tests and Runtime

# imports
import pytest  # used for our unit tests

from unstructured.partition.pdf_image.analysis.bbox_visualisation import get_bbox_thickness

# unit tests

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


def test_basic_small_bbox_returns_min_thickness():
    # Small bbox on a normal page should return min_thickness
    bbox = (10, 10, 20, 20)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    result = codeflash_output  # 30.4μs -> 2.12μs (1329% faster)


def test_basic_large_bbox_returns_max_thickness():
    # Large bbox close to page size should return max_thickness
    bbox = (0, 0, 950, 950)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    result = codeflash_output  # 27.1μs -> 1.96μs (1283% faster)


def test_basic_medium_bbox_returns_intermediate_thickness():
    # Medium bbox should return a value between min and max
    bbox = (100, 100, 500, 500)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    result = codeflash_output  # 25.4μs -> 1.88μs (1256% faster)


def test_basic_custom_min_max_thickness():
    # Test with custom min and max thickness
    bbox = (0, 0, 500, 500)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size, min_thickness=2, max_thickness=8)
    result = codeflash_output  # 25.5μs -> 2.00μs (1175% faster)


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


def test_zero_area_bbox():
    # Bbox with zero area (x1==x2 and y1==y2) should return min_thickness
    bbox = (100, 100, 100, 100)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    result = codeflash_output  # 25.2μs -> 1.92μs (1214% faster)


def test_bbox_exceeds_page_size():
    # Bbox larger than page should still clamp to max_thickness
    bbox = (-100, -100, 1200, 1200)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    result = codeflash_output  # 25.0μs -> 1.83μs (1264% faster)


def test_negative_coordinates_bbox():
    # Bbox with negative coordinates should still work
    bbox = (-10, -10, 20, 20)
    page_size = (100, 100)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    result = codeflash_output  # 25.0μs -> 1.92μs (1205% faster)


def test_min_equals_max_thickness():
    # If min_thickness == max_thickness, always return that value
    bbox = (0, 0, 1000, 1000)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size, min_thickness=3, max_thickness=3)
    result = codeflash_output  # 24.9μs -> 2.04μs (1119% faster)


def test_page_size_zero_raises():
    # Page size of zero should raise ZeroDivisionError
    bbox = (0, 0, 10, 10)
    page_size = (0, 0)
    with pytest.raises(ZeroDivisionError):
        get_bbox_thickness(bbox, page_size)  # 1.96μs -> 1.88μs (4.43% faster)


def test_bbox_on_line():
    # Bbox that's a line (x1==x2 or y1==y2) should return min_thickness
    bbox = (10, 10, 10, 100)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    result = codeflash_output  # 25.4μs -> 2.04μs (1143% faster)


def test_min_thickness_greater_than_max_thickness():
    # If min_thickness > max_thickness, function should clamp to min_thickness
    bbox = (0, 0, 1000, 1000)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size, min_thickness=5, max_thickness=2)
    result = codeflash_output  # 24.9μs -> 2.00μs (1146% faster)


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


def test_many_bboxes_scaling():
    # Test with 1000 bboxes of increasing size
    page_size = (1000, 1000)
    min_thickness, max_thickness = 1, 8
    for i in range(1, 1001, 100):  # 10 steps to keep runtime reasonable
        bbox = (0, 0, i, i)
        codeflash_output = get_bbox_thickness(bbox, page_size, min_thickness, max_thickness)
        result = codeflash_output  # 181μs -> 12.9μs (1307% faster)


def test_large_page_and_bbox():
    # Test with large page and bbox values
    bbox = (0, 0, 999_999, 999_999)
    page_size = (1_000_000, 1_000_000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    result = codeflash_output  # 24.2μs -> 2.08μs (1064% faster)


def test_randomized_bboxes():
    # Test with random bboxes within a page, ensure all results in bounds
    import random

    page_size = (1000, 1000)
    min_thickness, max_thickness = 1, 4
    for _ in range(100):
        x1 = random.randint(0, 900)
        y1 = random.randint(0, 900)
        x2 = random.randint(x1, 1000)
        y2 = random.randint(y1, 1000)
        bbox = (x1, y1, x2, y2)
        codeflash_output = get_bbox_thickness(bbox, page_size, min_thickness, max_thickness)
        result = codeflash_output  # 1.64ms -> 117μs (1297% faster)


def test_performance_large_number_of_calls():
    # Ensure function does not degrade with many calls (not a timing test, just functional)
    page_size = (500, 500)
    for i in range(1, 1001, 100):  # 10 steps
        bbox = (0, 0, i, i)
        codeflash_output = get_bbox_thickness(bbox, page_size)
        result = codeflash_output  # 173μs -> 12.7μs (1264% faster)


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


def test_bbox_with_float_coordinates():
    # Non-integer coordinates should still work (since function expects int, but let's see)
    bbox = (0.0, 0.0, 500.0, 500.0)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(tuple(map(int, bbox)), page_size)
    result = codeflash_output  # 24.0μs -> 1.88μs (1178% faster)


def test_bbox_equal_to_page():
    # Bbox exactly same as page should return max_thickness
    bbox = (0, 0, 1000, 1000)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    result = codeflash_output  # 23.8μs -> 1.83μs (1200% faster)


def test_bbox_minimal_size():
    # Bbox of size 1x1 should return min_thickness
    bbox = (10, 10, 11, 11)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    result = codeflash_output  # 23.9μs -> 1.88μs (1176% faster)


# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

# imports
import pytest  # used for our unit tests

from unstructured.partition.pdf_image.analysis.bbox_visualisation import get_bbox_thickness

# unit tests

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


def test_basic_small_bbox_min_thickness():
    # Very small bbox compared to page, should get min_thickness
    bbox = (10, 10, 20, 20)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)  # 24.1μs -> 1.88μs (1184% faster)


def test_basic_large_bbox_max_thickness():
    # Very large bbox, nearly the page size, should get max_thickness
    bbox = (0, 0, 900, 900)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)  # 23.9μs -> 1.79μs (1235% faster)


def test_basic_middle_bbox():
    # Bbox size between min and max, should interpolate
    bbox = (100, 100, 500, 500)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    thickness = codeflash_output  # 23.9μs -> 1.83μs (1205% faster)


def test_basic_non_square_bbox():
    # Non-square bbox, checks diagonal calculation
    bbox = (10, 10, 110, 410)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    thickness = codeflash_output  # 24.0μs -> 1.83μs (1207% faster)


def test_basic_custom_thickness_range():
    # Custom min/max thickness values
    bbox = (0, 0, 500, 500)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(
        bbox, page_size, min_thickness=2, max_thickness=8
    )  # 24.0μs -> 1.92μs (1155% faster)


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


def test_edge_bbox_zero_size():
    # Zero-area bbox, should always return min_thickness
    bbox = (100, 100, 100, 100)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)  # 24.0μs -> 1.83μs (1209% faster)


def test_edge_bbox_full_page():
    # Bbox covers the whole page, should return max_thickness
    bbox = (0, 0, 1000, 1000)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)  # 23.9μs -> 1.83μs (1205% faster)


def test_edge_bbox_negative_coordinates():
    # Bbox with negative coordinates, still valid diagonal
    bbox = (-50, -50, 50, 50)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    thickness = codeflash_output  # 23.9μs -> 1.83μs (1203% faster)


def test_edge_bbox_larger_than_page():
    # Bbox larger than page, should clamp to max_thickness
    bbox = (-100, -100, 1200, 1200)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)  # 23.8μs -> 1.79μs (1228% faster)


def test_edge_min_greater_than_max():
    # min_thickness > max_thickness, should always return min_thickness (clamped)
    bbox = (0, 0, 1000, 1000)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(
        bbox, page_size, min_thickness=5, max_thickness=2
    )  # 24.1μs -> 1.92μs (1156% faster)


def test_edge_zero_page_size():
    # Page size zero, should raise ZeroDivisionError
    bbox = (0, 0, 10, 10)
    page_size = (0, 0)
    with pytest.raises(ZeroDivisionError):
        get_bbox_thickness(bbox, page_size)  # 1.88μs -> 1.75μs (7.14% faster)


def test_edge_bbox_on_page_border():
    # Bbox on the edge of the page, not exceeding bounds
    bbox = (0, 0, 1000, 10)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    thickness = codeflash_output  # 24.8μs -> 2.00μs (1138% faster)


def test_edge_non_integer_bbox_and_page():
    # Bbox and page_size with float values, should still work
    bbox = (0.0, 0.0, 500.5, 500.5)
    page_size = (1000.0, 1000.0)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    thickness = codeflash_output  # 23.9μs -> 1.54μs (1448% faster)


def test_edge_bbox_swapped_coordinates():
    # Bbox with x2 < x1 or y2 < y1, negative width/height
    bbox = (100, 100, 50, 50)
    page_size = (1000, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)
    thickness = codeflash_output  # 24.3μs -> 1.96μs (1143% faster)


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


def test_large_scale_many_bboxes():
    # Test many bboxes on a large page
    page_size = (10000, 10000)
    for i in range(1, 1001, 100):  # 10 iterations, up to 1000
        bbox = (i, i, i + 100, i + 100)
        codeflash_output = get_bbox_thickness(bbox, page_size)
        thickness = codeflash_output  # 177μs -> 12.3μs (1341% faster)


def test_large_scale_increasing_bbox_size():
    # Test increasing bbox sizes from tiny to almost page size
    page_size = (1000, 1000)
    for size in range(1, 1001, 100):
        bbox = (0, 0, size, size)
        codeflash_output = get_bbox_thickness(bbox, page_size)
        thickness = codeflash_output  # 173μs -> 12.7μs (1263% faster)
        # Should be monotonic non-decreasing
        if size > 1:
            codeflash_output = get_bbox_thickness((0, 0, size - 100, size - 100), page_size)
            prev_thickness = codeflash_output


def test_large_scale_random_bboxes():
    # Generate 100 random bboxes and check thickness is in range
    import random

    page_size = (1000, 1000)
    for _ in range(100):
        x1 = random.randint(0, 900)
        y1 = random.randint(0, 900)
        x2 = random.randint(x1, 1000)
        y2 = random.randint(y1, 1000)
        bbox = (x1, y1, x2, y2)
        codeflash_output = get_bbox_thickness(bbox, page_size)
        thickness = codeflash_output  # 1.63ms -> 116μs (1296% faster)


def test_large_scale_extreme_aspect_ratios():
    # Very thin or very flat bboxes
    page_size = (1000, 1000)
    # Very thin vertical
    bbox = (500, 0, 501, 1000)
    codeflash_output = get_bbox_thickness(bbox, page_size)  # 23.8μs -> 1.88μs (1167% faster)
    # Very thin horizontal
    bbox = (0, 500, 1000, 501)
    codeflash_output = get_bbox_thickness(bbox, page_size)  # 18.3μs -> 1.38μs (1230% faster)


def test_large_scale_varied_thickness_range():
    # Test with large min/max thickness range
    page_size = (1000, 1000)
    for size in range(1, 1001, 200):
        bbox = (0, 0, size, size)
        codeflash_output = get_bbox_thickness(bbox, page_size, min_thickness=10, max_thickness=100)
        thickness = codeflash_output  # 93.3μs -> 7.17μs (1202% faster)


# 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-get_bbox_thickness-mjdlipbj and push.