rust-demo

Hands-on demo of the Rust programming language.

History of Rust

• Originally designed by Graydon Hoare at Mozilla Research, with contributions from Dave Herman, Brendan Eich, and others.
• Mozilla began sponsoring the project in 2009.
• Announced 2010: http://venge.net/graydon/talks/intro-talk-2.pdf
• Rust 1.0, the first stable release, released in 2015.
• Since 2011 rustc is compiled using rustc.
• rustc uses LLVM as its back end.
• The History of Rust: https://www.youtube.com/watch?v=79PSagCD_AY
• Firefox (components Servo and Quantum) written in Rust.
• Ad block engine in Brave.
• exa, ripgrep, bat, and fd written in Rust (you really want these tools!).
• Great overview of tools written in Rust: https://www.wezm.net/v2/posts/2020/100-rust-binaries/
• Discord uses Rust for some of its backed.

Why Rust

• "A language empowering everyone to build reliable and efficient software." (https://www.rust-lang.org)
• Fast but also safe
• Zero cost abstractions
• Type system
• Compiler catches most errors (if it compiles, it often just works)
• Compiler provides helpful error messages
• Memory safety
• Thread safety
• Private and immutable by default
• Great tooling (testing, documentation, auto-formatter, dependency management, package registry, no makefiles needed)
• Community
• Most-loved programming language in the 2016, 2017, 2018, 2019, and 2020 Stack Overflow annual surveys

Great resources

• Rust by Example
• The Rust Programming Language
• The Rustonomicon
• Rust Cookbook
• Why try Rust for scientific computing?
• Rust in Action
• The Rust FFI Omnibus

Memory model

• No explicit allocation and deallocation.
• No garbage collector either.
• Each value in Rust has an owner and there can only be one owner at a time.
• When the owner goes out of scope, the value is dropped.
• Rust knows the size of all stack allocations at compile time.

This does not compile:

let s1 = String::from("hello");
let s2 = s1;

println!("{}, world!", s1);

• Rust's memory is managed a bit like money: one owner, it can be borrowed.
• We can borrow references: https://doc.rust-lang.org/book/ch04-02-references-and-borrowing.html#references-and-borrowing
• At any given time, you can have either one mutable reference or any number of immutable references.

Installing Rust

Preferred way to install Rust for most developers: https://www.rust-lang.org/tools/install

Verify your installations of cargo and rustc:

$ cargo --version
cargo 1.47.0 (f3c7e066a 2020-08-28)

$ rustc --version
rustc 1.47.0 (18bf6b4f0 2020-10-07)

Hands-on demo

In this demo we will approximate pi by generating random points and computing their distance to origin:¹

Tasks/discussion points:

• Show how to bootstrap a project with cargo new
• Step out of the newly bootstrapped project
• Clone the code (this repository)
• Browse and discuss the sources
• Compile the sources with cargo check
• Compare cargo check and cargo build
• Discuss cargo run
• Experiment with cargo fmt
• Run the tests with cargo test
• Generate optimized version with cargo build --release
• Generate the documentation with cargo doc
• Discuss cargo publish and https://crates.io (the Rust package registry)

Interfacing with C, C++, Fortran, and Python

C calling Rust and Fortran calling Rust

cargo build --release

gfortran -L target/release/ -lpi examples/fortran/example.f90 -o fortran-example.x
gcc -L target/release/ -lpi examples/c/example.c -o c-example.x

env LD_LIBRARY_PATH=target/release/ ./fortran-example.x
env LD_LIBRARY_PATH=target/release/ ./c-example.x

Python calling Rust

Using PyO3 and Maturin:

cargo build --release
maturin develop --release
python -c "import pi; print(pi.pi_approximation(1000000))"

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1: GIF from https://www.soroushjp.com/2015/02/07/go-concurrency-is-not-parallelism-real-world-lessons-with-monte-carlo-simulations/