DEV Community: Christian Köberl

Beating C with 33 Lines of Java

Christian Köberl — Mon, 29 Jun 2020 00:00:00 +0000

This article was published originally on derkoe.dev.

After reading the "Beating C with X lines of Y" ¹ last year I immediately thought about trying this in my go-to language: Java. Now you might ask: "Java? Isn't Java known to have a slow startup and heavy memory footprint?" But let's see how Java performs - especially with its latest incarnation GraalVM.

Benchmarking

I will be using GNU time for the time and memory comparison (same as the Go version):

$ /usr/bin/time -f "%es %MKB" wc lorem_ipsum.txt
  17023  782992 4830478 lorem_ipsum.txt
0.05s 2064KB

All results are from runs on my Laptop:

Intel Core i7-8550U (4 cores, 8 threads)
16 GB RAM
WSL2 running Arch Linux on Windows 10 (2004)

The "standard" approach

The initial version I came up with used the obvious way in Java - reading the file using a BufferedReader:

InputStream in = Files.newInputStream(Paths.get(fileName));
try (BufferedReader reader = new BufferedReader(new InputStreamReader())) {
  ...
}

(full code on GitHub)

Running some first tests with this code shows that it can't compete with the native wc:

Implementation	Input file	Time	Max memory
wc	4.6MB	0.05s	2,064KB
wc-br.java	4.6MB	0.24s	40,188KB
wc	100MB	0.43s	2,188KB
wc-br.java	100MB	1.21s	45,036KB

Manual buffering

So let's try a more direct approach with manual buffering (inspired by the Go version):

class wc {
  public static void main(String[] args) throws IOException {
    int lineCount = 0, wordCount = 0, charCount = 0, count;
    char[] cbuf = new char[16 * 1024];
    InputStream is = args.length == 0 ? System.in : Files.newInputStream(Paths.get(args[0]));
    try (Reader reader = new InputStreamReader(is)) {
      boolean prevWhitespace = true;
      while ((count = reader.read(cbuf)) >= 0) {
        for (int i = 0; i < count; i++) {
          char charVal = cbuf[i];
          charCount++;
          if (charVal == '\n') {
            lineCount++;
            prevWhitespace = true;
          } else if (isWhitespace(charVal)) {
            prevWhitespace = true;
          } else if (prevWhitespace) {
            wordCount++;
            prevWhitespace = false;
          }
        }
      }
    }
    // printing
  }
}

(full code on GitHub - 33 lines of code according to tokei)

Let's try this version:

Implementation	Input file	Time	Max memory
wc	4.6MB	0.05s	2,064KB
wc.java	4.6MB	0.18s	39,844KB
wc	100MB	0.43s	2,188KB
wc.java	100MB	0.46s	42,840KB

Looking a lot better for big files (almost the same time) but still not that good for small ones. And the used memory is more than an order of magnitude higher: ~40MB vs 2MB.

Enter GraalVM

GraalVM is a new ecosystem and platform for running Java and other programming languages (like JavaScript, Ruby or Python). One of main benefits for Java programs is to compile them to a native executable which reduces startup-time and memory usage.

Let's give it a try - after installing GraalVM and native-image simply compile the Java class to a native binary with:

javac wc.java && native-image wc

which results in a native binary wc (or wc.exe) for your platform (currently cross-compilation is not supported).

When running the same code above with the native binary there are major improvements - here are the results plus a test with a 1GB file:

Implementation	Input file	Time	Max memory
wc	4.6MB	0.05s	2,064KB
wc.java (native)	4.6MB	0.03s	7,172KB
wc	100MB	0.43s	2,188KB
wc.java (native)	100MB	0.39s	7,524KB
wc	1GB	4.20s	2,120KB
wc.java (native)	1GB	3.57s	10,968KB

Memory usage is down to 7MB for file up to 100 MB and we now easily beat the time of the C implementation. Still, the memory consumption is 3-5 time higher than the "real" native program.

Summary

Java has come a long way - from Applets to enterprise server application and now microservices. Because of the J2EE/enterprise era it is known for heavy memory usage and slow startup times but in recent years Java has changed and adapted to the cloud native boom. With GraalVM and native images Java can now even compete with system languages like C, Go or Rust. With native image Java is now also a viable solution for building CLIs.

Ada, Go, Haskell, Rust ↩

Development Environment in WSL2

Christian Köberl — Mon, 25 May 2020 00:00:00 +0000

This article was published originally on derkoe.dev.

This guide shows how to setup a full development environment including UI apps (X11) in WSL2 on Windows 10. WSL2 enables a "full" Linux development environment in Windows.

Why?

The first thing you might ask is: why? First, we have to run Windows on our machines - so the all-in Linux does not work. Second, Linux is a lot faster for building software than Windows - our biggest app compiles in 13 minutes under Windows and in just 2 minutes under WSL on my machine which is a massive improvement.

Enable WSL2 and Install Ubuntu

For WSL2 to work you will need a Windows 10 build 19041 (aka 20H1) or higher (any edition will work, even Home). Then simply follow the guide from Microsoft.

TL;DR:

Enable the features WSL and VM-Platform in Powershell as Admin:

   dism.exe /online /enable-feature /featurename:Microsoft-Windows-Subsystem-Linux /all /norestart
   dism.exe /online /enable-feature /featurename:VirtualMachinePlatform /all /norestart

Restart Windows
Set WSL2 as default:

   wsl --set-default-version 2

Go to the Microsoft Store and install "Ubuntu"
Launch Ubuntu from Start menu (this will ask you for a user account)

You can now re-launch a shell in your Ubuntu instance with "Ubuntu" from the Start menu or execute wsl from the command line. The WSL command line tool has many options which you can find with wsl --help or in the Command Reference.

Update and Install Software

Inside your Ubuntu Linux update all packages:

sudo apt update
sudo apt upgrade

Then install packages you need for your development - in my case it is Java 11, Maven, Node.js/NPM and git:

sudo apt install openjdk-11-jdk openjdk-11-source maven nodejs npm git

Do not install Docker CLI or Docker Compose because these are provided by Docker Desktop (see next section).

Install Docker (optional)

Most developers need Docker for their local setup - the newest Docker Desktop version supports WSL2 out of the box (even on Windows Home).

GUI Apps

Currently there is no support for GUI apps for WSL - Microsoft has announced that they are working on GUI support using Wayland and that it should ship in 2020. So you have to use X11 forwarding or other tricks to enable this - I have tried all of them and there are some issues with any of the solutions:

X11 server on Windows (VcXsrv or X410) and setting the DISPLAY variable in Linux (export DISPLAY=ip route show | grep 'default via' | awk '{print $3}':0.0 in your .bashrc).
- Works quite well - good performance, shortcuts work, even mouse back/forward buttons work as expected
- The main problem is that when you go to standby or hibernate the connection between Windows and WSL breaks and all your apps stop. If you can live with that go with this solution!
Running xrdp on Linux and using Remote Desktop to connect
- In this case you are running a full desktop - that means you have to install Xfce (Gnome does not seem to work).
- With this solution the whole UI feels a bit laggy and slow - I tried to tune the xrdp params without success.
Xpra - a virtual X11 server to connect via a client on Windows (or other platforms)
- The solution works but there are many issues like crashes, window positions are completely wrong, extra mouse buttons do not work, etc.
X2Go - also a virtual X11 server with an Windows client
- This seems to be the most promising solution
- As with plain X11: good performance, shortcuts work, even mouse back/forward buttons work as expected, plus the reconnect feature
- The only drawback is the quirky Windows client (but I got used to it)

X2Go

Here is the X2Go setup in more details (since it worked best for me).

Initial setup

Fix SSH host keys

   sudo apt-get remove --purge openssh-server
   sudo apt-get install openssh-server
   sudo service ssh --full-restart

Install X2Go on your Linux distribution

   apt install x2goserver

Download and install the client for Windows.
Configure the
- Host: localhost
- Login: <your user>
- Session type: Published Applications

After each WSL/Windows restart

Launch ssh in Linux (if not started yet): sudo service ssh start
Launch "X2Go Client" on Windows ad connect to the server with user/password
Now you can launch X11 apps via the tray icon (see X2Go Published Applications)

Editors/IDEs

Visual Studio Code

Simply install VSCode and then you can open it from the Linux shell with code or code <path> - most of the time it will be:

code .

IntelliJ IDEA

On a normal Ubuntu you could install IntelliJ IDEA via Snap but Snap does not work on WSL2 (there is a hacky workaround).

So, the easiest way is to install it manually:

Get the latest tar.gz from the downloads page
Extract it an create a symlink (so you can easily switch versions):

   cd /opt
   sudo tar xzf /mnt/c/Users/$USER/Downloads/idea-{edition-version}.tar.gz
   sudo ln -s /opt/idea-{edition-version} /opt/idea

To easily launch the app via the X2Go context menu create an app desktop entry /usr/share/applications/intellij-idea.desktop with the following contents:

   [Desktop Entry]
   Name=Intellij IDEA
   Comment=JetBrains Intellij IDEA Java IDE
   Categories=Development
   Keywords=java;ide
   Exec=/opt/idea/bin/idea.sh
   Type=Application
   Icon=/opt/idea/bin/idea.png

Open Issues

There are still many issues with WSL2 - the biggest problems are:

Systemd is not running - the official issue is Blockers for systemd?. Seems like Microsoft is working with the Systemd team on this problem. Anyway withoud Systemd you cannot run any services and things like Snap packages do not work. There are some workarounds like genie or this instructions.
GUI apps are a pain (in the a..) - like alrady mentioned above.
There are many troubles with VPN solutions: CISCO AnyConnect, Checkpoint VPN.