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Julia uses multiple dispatch as a paradigm, making it easy to express many object-oriented and functional programming patterns. The talk on the Unreasonable Effectiveness of Multiple Dispatch explains why it works so well.
Julia makes it possible to build complete applications. Write web UIs with Dash.jl or native UIs with QML.jl and GTK.jl. Build shared libraries and executables with PackageCompiler. Deploy on a webserver with HTTP.jl or embedded devices using ARM binaries. Powerful shell integration make it easy to managing other processes.
Julia has foreign function interfaces for C, Fortran, C++, Python, R, Java, and many other languages. Julia can also be embedded in other programs through its embedding API. Specifically, Python programs can call Julia using PyJulia. R programs can do the same with R's JuliaCall, which is demonstrated by calling MixedModels.jl from R.
Julia is designed for parallelism, and provides built-in primitives for parallel computing at every level: instruction level parallelism, multi-threading, GPU computing, and distributed computing. The Celeste.jl project achieved 1.5 PetaFLOP/s on the Cori supercomputer at NERSC using 650,000 cores.
The Julia compiler can also generate native code for GPUs. Packages such as DistributedArrays.jl and Dagger.jl provide higher levels of abstraction for parallelism. Distributed Linear Algebra is provided by packages like Elemental.jl and TSVD.jl. MPI style parallelism is also available through MPI.jl.
The MLJ.jl package provides a unified interface to common machine learning algorithms, which include generalized linear models, decision trees, and clustering. Flux.jl and Knet.jl are powerful packages for Deep Learning. Packages such as Metalhead, ObjectDetector, and TextAnalysis.jl provide ready to use pre-trained models for common tasks. AlphaZero.jl provides a high peformance implementation of the reinforcement learning algorithms from AlphaZero. Turing.jl is a best in class package for probabilistic programming.
Julia is designed from the ground up to be very good at numerical and scientific computing. This can be seen in the abundance of scientific tooling written in Julia, such as the state-of-the-art differential equations ecosystem (DifferentialEquations.jl), optimization tools (JuMP.jl and Optim.jl), iterative linear solvers (IterativeSolvers.jl), Fast Fourier transforms (AbstractFFTs.jl), and much more. General purpose simulation frameworks are available for Scientific Machine Learning, Quantum computing and much more.
Julia also offers a number of domain-specific ecosystems, such as in biology (BioJulia), operations research (JuMP Dev), image processing (JuliaImages), quantum physics (QuantumBFS), nonlinear dynamics (JuliaDynamics), quantitative economics (QuantEcon), astronomy (JuliaAstro) and ecology (EcoJulia). With a set of highly enthusiastic developers and maintainers, the scientific ecosystem in Julia continues to grow rapidly.
The Julia data ecosystem provides DataFrames.jl to work with datasets, and perform common data manipulations. CSV.jl is a fast multi-threaded package to read CSV files and integration with the Arrow ecosystem is in the works with Arrow.jl. Online computations on streaming data can be performed with OnlineStats.jl. The Queryverse provides query, file IO and visualization functionality. In addition to working with tabular data, the JuliaGraphs packages make it easy to work with combinatorial data.
Data visualization has a complicated history. Plotting software makes trade-offs between features and simplicity, speed and beauty, and a static and dynamic interface. Some packages make a display and never change it, while others make updates in real-time.
Plots.jl is a visualization interface and toolset. It provides a common API across various backends, like GR.jl, PyPlot.jl, and PlotlyJS.jl. Makie.jl is a sophisticated package for complex graphics and animations. Users who are used to "grammar of graphics" plotting APIs should take a look at Gadfly.jl. VegaLite.jl provides the Vega-Lite grammar of interactive graphics interface as a Julia package. For those who do not wish to leave the comfort of the terminal, there is also UnicodePlots.jl.
Julia has been downloaded over 17 million times and the Julia community has registered over 4,000 Julia packages for community use. These include various mathematical libraries, data manipulation tools, and packages for general purpose computing. In addition to these, you can easily use libraries from Python, R, C/Fortran, C++, and Java. If you do not find what you are looking for, ask on Discourse, or even better, contribute one!
Tutorial on precompilation
The story of debugging a mysterious Julia segfault.
Within private companies, it can be difficult to smoothly transition internal code into high quality open-source contributions. At JuliaCon 2020, industry Julia users came together to discuss how to maximize their impact in the Julia ecosystem.