Mandelbrot

This repository includes multiple implementations of the Mandelbrot algorithm in Rust, showing how parallelism and SIMD can be used to speed it up.

From fastest to slowest:

• std::simd: Uses the built-in portable SIMD support in Rust, requires unstable compiler.
• pulp SIMD: Use the pulp crate to implement portable SIMD operations. pulp can use the stable compiler.
• wide SIMD: Use the wide crate to implement portable SIMD operations. wide can use the stable compiler.
• Scalar with autovectorization: A scalar version written so the compiler can autovectorize it, i.e. decide to use SIMD automatically.
• Scalar: The standard algorithm, one value at a time.

All implementations use parallelism out of the box, using Rayon.

History

Much of this is based on the mandelbrot benchmark from the benchmarksgame, as implemented in the since-superseded packed_simd project.

Changes from the original implementation:

• Updated to use the newer Rust portable SIMD API (nightly only at the moment).
• Simplified the calculation logic so it's easier to understand.
• Autovectorized implementation contributed by giovannicuccu.
• pulp implementation contributed by sarah quiñones.

Licensed under MIT or Apache 2.0, at your choice, copyrighted by the Rust Project Developers, with minor changes by Itamar Turner-Trauring.

Background

http://mathworld.wolfram.com/MandelbrotSet.html

Usage

It takes four arguments in this order:

• width: width of the image to render
• height: height of the image to render
• algorithm: algorithm to use:
  • scalar: scalar algorithm
  • simd: parallelized SIMD algorithm
  • ispc: ISPC + tasks algorithm
• --color (optional): enables colorized output, which also determines the image format.
  • disabled (default): PBM: Portable BitMap format (black & white output)
  • enabled: PPM: Portable PixMap format (colored output)

The resulting image is piped to stdout.

cargo run --release -- 400 400 --algo simd > output.ppm outputs:

cargo run --release -- 400 400 --algo simd --color > output.ppm outputs:

Performance

Make sure you have hyperfine installed.

Multi-threaded:

$ ./benchmark.sh

Single-threaded:

$ RAYON_NUM_THREADS=1 ./benchmark.sh