Why Docling is SO slow when converting PDF with images

[MingLin-home]

We benchmarked the conversion speed of Docling with PDF files containing images. The benchmarking code is provided below:

import logging
import time
from pathlib import Path
from docling_core.types.doc import ImageRefMode, PictureItem, TableItem
from docling.datamodel.base_models import InputFormat
from docling.datamodel.pipeline_options import PdfPipelineOptions
from docling.document_converter import DocumentConverter, PdfFormatOption
IMAGE_RESOLUTION_SCALE = 2.0
_log = logging.getLogger(__name__)

def main():
    logging.basicConfig(level=logging.INFO)
    input_doc_path = Path('./test.pdf')
    output_dir = Path("./test_output")
    pipeline_options = PdfPipelineOptions()
    pipeline_options.images_scale = IMAGE_RESOLUTION_SCALE
    pipeline_options.generate_page_images = True
    pipeline_options.generate_picture_images = True
    pipeline_options.do_ocr = False
    pipeline_options.do_table_structure = False
    pipeline_options.do_code_enrichment = False
    pipeline_options.do_formula_enrichment = False
    pipeline_options.do_picture_classification = False
    pipeline_options.do_picture_description = False
    doc_converter = DocumentConverter(
        format_options={
            InputFormat.PDF: PdfFormatOption(pipeline_options=pipeline_options,)
        }
    )
    start_time = time.time()
    conv_res = doc_converter.convert(input_doc_path)
    end_time = time.time() - start_time
    _log.info(f"Document converted and figures exported in {end_time:.2f} seconds.")
    
if __name__ == "__main__":
    main()

All unnecessary features, such as OCR, were disabled during the tests.

We compared the processing times (in seconds) of Docling and PyMuPDF using a set of PDF files. The results are shown in the following table:

PDF	pages	Docling	Tika (docker)	PyMuPDF
Text-only	20	9.70	0.69	0.07
Small PDF	5	2.60	5.82	0.30
Medium PDF	20	15.23	1.89	0.18
Large PDF	50	34.0	8.60	1.11

In the above test, Docling is 30~80 times slower than PyMuPDF.

Any reason for the slowness? Any plan to improve the speed?

Benchmark environment:
MacBook Pro M2 Pro, Memory 32 GB. Docling 2.34.0, Python 3.11.