Mojo dictionary benchmarks

This repository contains programs to benchmark different dictionary implementations in Mojo, with comparisons to other languages (currently Python and Rust). The main goal is to evaluate the performance of Mojo's dictionary implementations and set up a simple framework for future evaluations.

Overview

The programs benchmark the following operations:

1. Dictionary Initialization: Creating and populating a dictionary-like data structure with a large number of items.
2. Value Modification: Modifying values for keys in the dictionary.
3. Summation: Calculating a sum based on the dictionary's values.

...
var keys = List[String](capacity=NUM)
for i in range(NUM):
    keys[i] = "k" + str(i)

var start = now()

var dic = Dict[String, Int]()
for i in range(NUM):
    dic[keys[i]] = i % 7
for i in range(0, NUM, 2):
    dic[keys[i]] *= 2
var sum_val = 0
for i in range(NUM):
    sum_val += dic[keys[i]]

var elapsed = (now() - start) / 1e9
...

Programs benchmarked

• Mojo: (compiled with Mojo 24.5 and 25.5)

  • stdlib_dict.mojo: Uses Mojo's standard dictionary.
  • compact_dict.mojo: Uses compact-dict.
  • python_dict.mojo: Uses Python's dictionary via Mojo s Python integration.

• Python:

  • stdlib_dict.py: Implements the same operations as in Mojo using Python's standard dictionary.

• Rust:

  • hashmap.rs: Benchmarks Rust's HashMap, both in standard mode and with -C opt-level=3 for optimization. (Suggestions on how to improve the performance of this basic implementation are most welcome.)

Requirements

• Install the pixi command line tool by following the instructions in the Mojo Documentation.
• Ensure that both Rust and Python are installed on your system.

Running the Benchmarks

To run the benchmarks, use the provided shell script:

bash ./benchmarks.sh

After running the benchmarks, you can view the performance comparison in results/benchmarks.md and a plot in results/benchmark.png.

Benchmarks

Benchmark	Mojo 24.5	Mojo 25.5
Measured at	11 Oct 2024	19 Jul 2025
---------------------	-------------	--------------
compact_dict.mojo	0.084032 sec	0.079602 sec
hashmap.rs (optimized)	0.143373 sec	0.174457 sec
stdlib_dict.py	0.264387 sec	0.233545 sec
hashmap.rs	0.470244 sec	0.398161 sec
stdlib_dict.mojo	2.523637 sec	0.214174 sec
python_dict.mojo	10.352229 sec	0.958389 sec

Contributing

Contributions are welcome! If you'd like to add new benchmarks, enhance the current ones, or any suggestions, please open an issue or submit a pull request.

Changelog

• 2025.07.19
  • Code updated to reflect changes in mojo spec
• 2024.10.12
  • Reimplemented based on feedback provided by the community on the Modular Discord server.
• 2024.10.11
  • Initial commit

License

This project is licensed under the MIT License.