cujson

Parse JSON and JSON Lines on an NVIDIA GPU from Python, using the cuJSON parser (ASPLOS '26) packaged by cuJSON-rs.

pip install cujson

Requirements

• Linux x86_64, Python 3.10 or newer
• An NVIDIA GPU of compute capability 7.5 or newer (Turing onwards)
• An NVIDIA driver that supports CUDA 13 (R580 or newer)

The wheel links the CUDA runtime statically, so the driver is the only CUDA component you need to install. On a CUDA 12 system, build from a checkout with pip install ./crates/cujson-py.

Usage

import cujson

doc = cujson.parse('{"user": {"name": "Ada", "langs": ["en", "fr"]}}')
doc.to_python()                  # {'user': {'name': 'Ada', 'langs': ['en', 'fr']}}
doc.pointer("/user/langs/1")     # 'fr'  (RFC 6901 JSON Pointer)

lines = cujson.parse_lines('{"id": 1}\n{"id": 2}\n')
lines.to_python()                # [{'id': 1}, {'id': 2}]
lines.pointer("/1/id")           # 2  (the first token selects the line)
len(lines)                       # 2

cujson.parse_file("data.json")   # read and parse a file
cujson.cuda_info()               # runtime, driver, compiled architectures, devices
cujson.trim_pinned_cache()       # release the pinned buffer kept between parses

parse and parse_lines accept str, bytes, bytearray or memoryview. The GIL is released while the GPU parses.

Errors

All exceptions derive from cujson.CujsonError:

Limitations

• cuJSON checks UTF-8 validity and bracket balance, not the full JSON grammar: malformed scalars such as 1.2.3 are not rejected.
• Inputs are limited to just under 2 GiB (cuJSON uses 32-bit sizes).
• Parses are serialised within a process: cuJSON uses the default CUDA stream.
• After a parse, dropping its Document keeps at most one tape-sized pinned host buffer (roughly a third of the input size) allocated so the next parse can reuse it. It is released by cujson.trim_pinned_cache() or when the process exits.

Credits

cuJSON is by Ashkan Vedadi Gargary, Soroosh Safari Loaliyan and Zhijia Zhao (MIT licensed). If you use it in research, cite CuJSON: A Highly Parallel JSON Parser for GPUs (ASPLOS '26). cuJSON-rs is MIT licensed.