Author Archives: Open Source Programs Office

Why I contribute to Chromium

This is a guest post by Yoav Weiss who was recently recognized through the Google Open Source Peer Bonus Program for his work on the Chromium project. We invited Yoav to share about his work on our blog.

I was recently recognized by Google for my contributions to Chromium and wanted to write a few words on why I contribute to the project, other rendering engines and the web platform in general. I also wanted to share how it helped me evolve as a developer and why more people should contribute to the web platform for their own benefit.

The web platform

I’ve written before about why I think the web platform is an extremely important asset for humanity and why we should make sure it'll thrive for years to come. It enables the distribution of knowledge to the corners of the earth and has fundamentally changed our world. Yet, compared to the amount of users (billions!) and web developers (millions), there are only a few hundred engineers working on maintaining and improving the platform itself.

That means that there are many aspects of the platform that are not as well maintained as they should be. We're at a real risk of a "tragedy of the commons" scenario, where despite usage and utility, the platform will collapse under its own weight because maintaining it is nobody's exclusive problem.

How I got started

Personally, I had been working on web performance for well over a decade before I decided to get more involved and lend my hand in building the platform. For a large part of my professional life, browsers were black boxes. They were given to us by the browser gods and that's what we had to work with for the next few years. Their undocumented bugs and quirks became gospel, passed from senior engineers to their juniors.

Then at some point, that situation changed. Slowly but surely, open source browsers started picking up market share. No longer black boxes, we can actually see what happens on the inside!

I first got involved by joining the responsive images discussions and the Responsive Images Community Group. Then, I saw a tweet from RICG's chair calling to develop a prototype of the current proposal to prove its feasibility and value. And I jumped in.

I created a prototype using Chromium and WebKit, demoed it to anyone that was interested, worked on the proposals and argued the viability of the proposals' approach on the various mailing lists. Eventually, we were able to get some browser folks on board, improve the proposals and their fit to the rest of the platform, and I started working on an implementation.

The amount of work this required was larger than I expected. Eventually I managed to ship the feature in Blink and Chromium, and complete large parts of the implementation in WebKit as well. WOOT!

Success! Now what?

After that project was done, I started looking into what I should do next. I was determined to continue working on browsers and find a gig that would let me do that. So I searched for an employer with a vested interest in the web and in making it faster, who would be happy to let me work on the platform's client - the web browser.

I found such an employer in Akamai, where I have been working as a Principal Architect ever since. As part of my job I'm working on our performance optimization features as well as performance-related browser features, making sure they make it into browsers in a timely fashion.

Why you should contribute, too

Now, chances are that if you're reading this, you're also relying on the web platform for your job in one way or another. Which means that there's a chance that it also makes sense for your organization to contribute to the web platform. Let’s explore the reasons:

1. Make sure work is done on features you care about

If you're like me, you love the web platform and the reach it provides you, but you're not necessarily happy with all of it. The web is great, but not perfect. Since browsers and web standards are no longer black boxes, you can help change that.

You can work on standards and browsers to change them to include your use-case. That's immense power at your fingertips: put in the work and the platform evolves for all the billions of users out there.

And you don’t have to wait years before new features can be used in production like with yesteryear's browser changes. With today’s browser update rates and progressive enhancement, you’ll probably be able to use changes in production within a few months.

2. Gain expertise that can help you do your job better

Knowing browser internals better can also give you superpowers in other parts of your job. Whenever questions about browser behavior arrive, you can take a peek into the source code and have concrete answers rather than speculation.

Keeping track of standards discussions give you visibility into new browser APIs that are coming along, so that you can opt to use those rather than settle for sub-optimal alternatives that are currently available.

3. Grow as an engineer

Working on browsers teaches you a lot about how things work under the surface and enables you to understand the internals of modern browsers, which are extremely complex machines. Further, this work allows you to get code reviews from the world's leading experts on these subjects. What better way to grow than to interact with the experts?

4. It's a fun and welcoming community

Contributing to the web platform has been a great experience for me. Working with the Chromium project, in particular, is always great fun. The project is Google backed, but there are many external contributors and the majority of work and decisions are being done in the open. The people I've worked with are super friendly and happy to help. All in all, it's really fun!

Join us

The web needs more people working on it, and working on the web platform can be extremely beneficial to you, your career and your business.

If you're interested in getting started with web standards, the Discourse instance of the web Platform Incubator Community Group (or WICG for short) is where it's at (disclaimer: I'm co-chairing that group). For getting started with Chromium development, this is the post for you.

And most important, don't be afraid to ask the community. People on blink-dev and IRC are super friendly and will be happy to point you in the right direction.

So come on over and join the good cause. We'll be happy to have you!

By Yoav Weiss, Chromium contributor

Announcing OSS-Fuzz: Continuous fuzzing for open source software

We are happy to announce OSS-Fuzz, a new Beta program developed over the past years with the Core Infrastructure Initiative community. This program will provide continuous fuzzing for select core open source software.

Open source software is the backbone of the many apps, sites, services, and networked things that make up “the internet.” It is important that the open source foundation be stable, secure, and reliable, as cracks and weaknesses impact all who build on it.

Recent security stories confirm that errors like buffer overflow and use-after-free can have serious, widespread consequences when they occur in critical open source software. These errors are not only serious, but notoriously difficult to find via routine code audits, even for experienced developers. That's where fuzz testing comes in. By generating random inputs to a given program, fuzzing triggers and helps uncover errors quickly and thoroughly.

In recent years, several efficient general purpose fuzzing engines have been implemented (e.g. AFL and libFuzzer), and we use them to fuzz various components of the Chrome browser. These fuzzers, when combined with Sanitizers, can help find security vulnerabilities (e.g. buffer overflows, use-after-free, bad casts, integer overflows, etc), stability bugs (e.g. null dereferences, memory leaks, out-of-memory, assertion failures, etc) and sometimes even logical bugs.

OSS-Fuzz’s goal is to make common software infrastructure more secure and stable by combining modern fuzzing techniques with scalable distributed execution. OSS-Fuzz combines various fuzzing engines (initially, libFuzzer) with Sanitizers (initially, AddressSanitizer) and provides a massive distributed execution environment powered by ClusterFuzz.

Early successes

Our initial trials with OSS-Fuzz have had good results. An example is the FreeType library, which is used on over a billion devices to display text (and which might even be rendering the characters you are reading now). It is important for FreeType to be stable and secure in an age when fonts are loaded over the Internet. Werner Lemberg, one of the FreeType developers, was an early adopter of OSS-Fuzz. Recently the FreeType fuzzer found a new heap buffer overflow only a few hours after the source change:

ERROR: AddressSanitizer: heap-buffer-overflow on address 0x615000000ffa
READ of size 2 at 0x615000000ffa thread T0
SCARINESS: 24 (2-byte-read-heap-buffer-overflow-far-from-bounds)
   #0 0x885e06 in tt_face_vary_cvtsrc/truetype/ttgxvar.c:1556:31

OSS-Fuzz automatically notified the maintainer, who fixed the bug; then OSS-Fuzz automatically confirmed the fix. All in one day! You can see the full list of fixed and disclosed bugs found by OSS-Fuzz so far.

Contributions and feedback are welcome

OSS-Fuzz has already found 150 bugs in several widely used open source projects (and churns ~4 trillion test cases a week). With your help, we can make fuzzing a standard part of open source development, and work with the broader community of developers and security testers to ensure that bugs in critical open source applications, libraries, and APIs are discovered and fixed. We believe that this approach to automated security testing will result in real improvements to the security and stability of open source software.

OSS-Fuzz is launching in Beta right now, and will be accepting suggestions for candidate open source projects. In order for a project to be accepted to OSS-Fuzz, it needs to have a large user base and/or be critical to Global IT infrastructure, a general heuristic that we are intentionally leaving open to interpretation at this early stage. See more details and instructions on how to apply here.

Once a project is signed up for OSS-Fuzz, it is automatically subject to the 90-day disclosure deadline for newly reported bugs in our tracker (see details here). This matches industry’s best practices and improves end-user security and stability by getting patches to users faster.

Help us ensure this program is truly serving the open source community and the internet which relies on this critical software, contribute and leave your feedback on GitHub.

By Mike Aizatsky, Kostya Serebryany (Software Engineers, Dynamic Tools); Oliver Chang, Abhishek Arya (Security Engineers, Google Chrome); and Meredith Whittaker (Open Research Lead).

Docker + Dataflow = happier workflows

When I first saw the Google Cloud Dataflow monitoring UI -- with its visual flow execution graph that updates as your job runs, and convenient links to the log messages -- the idea came to me. What if I could take that UI, and use it for something it was never built for? Could it be connected with open source projects aimed at promoting reproducible scientific analysis, like Common Workflow Language (CWL) or Workflow Definition Language (WDL)?
Screenshot of a Dockerflow workflow for DNA sequence analysis.

In scientific computing, it’s really common to submit jobs to a local high-performance computing (HPC) cluster. There are tools to do that in the cloud, like Elasticluster and Starcluster. They replicate the local way of doing things, which means they require a bunch of infrastructure setup and management that the university IT department would otherwise do. Even after you’re set up, you still have to ssh into the cluster to do anything. And then there are a million different choices for workflow managers, each unsatisfactory in its own special way.

By day, I’m a product manager. I hadn’t done any serious coding in a few years. But I figured it shouldn’t be that hard to create a proof-of-concept, just to show that the Apache Beam API that Dataflow implements can be used for running scientific workflows. Now, Dataflow was created for a different purpose, namely, to support scalable data-parallel processing, like transforming giant data sets, or computing summary statistics, or indexing web pages. To use Dataflow for scientific workflows would require wrapping up shell steps that launch VMs, run some code, and shuttle data back and forth from an object store. It should be easy, right?

It wasn’t so bad. Over the weekend, I downloaded the Dataflow SDK, ran the wordcount examples, and started modifying. I had a “Hello, world” proof-of-concept in a day.

To really run scientific workflows would require more, of course. Varying VM shapes, a way to pass parameters from one step to the next, graph definition, scattering and gathering, retries. So I shifted into prototyping mode.

I created a new GitHub project called Dockerflow. With Dockerflow, workflows can be defined in YAML files. They can also be written in pretty compact Java code. You can run a batch of workflows at once by providing a CSV file with one row per workflow to define the parameters.

Dataflow and Docker complement each other nicely:

  • Dataflow provides a fully managed service with a nice monitoring interface, retries,  graph optimization and other niceties.
  • Docker provides portability of the tools themselves, and there's a large library of packaged tools already available as Docker images.

While Dockerflow supports a simple YAML workflow definition, a similar approach could be taken to implement a runner for one of the open standards like CWL or WDL.

To get a sense of working with Dockerflow, here’s “Hello, World” written in YAML:

defn:
  name: HelloWorkflow
steps:
- defn:
    name: Hello
    inputParameters:
      name: message
      defaultValue: Hello, World!
    docker:
      imageName: ubuntu
      cmd: echo $message

And here’s the same example written in Java:

public class HelloWorkflow implements WorkflowDefn {
  @Override
  public Workflow createWorkflow(String[] args) throws IOException {
    Task hello =
        TaskBuilder.named("Hello").input("message", “Hello, World!”).docker(“ubuntu”).script("echo $message").build();
    return TaskBuilder.named("HelloWorkflow").steps(hello).args(args).build();
  }
}

Dockerflow is just a prototype at this stage, though it can run real workflows and includes many nice features, like dry runs, resuming failed runs from mid-workflow, and, of course, the nice UI. It uses Cloud Dataflow in a way that was never intended -- to run scientific batch workflows rather than large-scale data-parallel workloads. I wish I’d written it in Python rather than Java. The Dataflow Python SDK wasn’t quite as mature when I started.

Which is all to say, it’s been a great 20% project, and the future really depends on whether it solves a problem people have, and if others are interested in improving on it. We welcome your contributions and comments! How do you run and monitor scientific workflows today?

By Jonathan Bingham, Google Genomics and Verily Life Sciences

Google Summer of Code 2016 wrap-up: STE||AR

This is part of a series of guest posts from students, mentors and organization administrators who participated in Google Summer of Code (GSoC) 2016. GSoC is an annual program which pairs university students with mentors to work on open source software.


This summer the STE||AR Group was proud to mentor four students through Google Summer of Code. These students worked on a variety of projects which helped improve our software, HPX. This library is a distributed C++ runtime system which supports a standards compliant API and helps users scale their applications across thousands of machines.

The improvements to the code base will help our team and users of HPX around the world. A summary of our students’ projects:

Parsa Amini – HPX Debugger

Developing a better distributed debugging tool is essential to increase the programmability of HPX. Parsa’s project, Scimitar, aims to facilitate the debugging process for HPX programmers by extending the features of GDB, an existing debugger. The project then complements it with new commands for easier switching between localities across clusters, HPX thread debugging, awareness of internal HPX data structures, and semi-automated preparation for distributed debugging sessions. Additional functionality such as locating an object and viewing the queue information on each core is provided through using API provided by HPX itself. His work can be found on GitHub.

Aalekh Nigam – Implement a Map/Reduce Framework

This project aimed to expose a Map/Reduce programming model over HPX. During the summer, Aalekh was able to develop a single node implementation of HPXflow (map/reduce programming model) and laid the groundwork for the further multi-node version with database support. Although the initial task was limited to implementing the Map/Reduce model, he was also able to implement an improved dataflow model as well.

Minh-Khanh Do - Working on Parallel Algorithms for HPX::Vector

Minh-Khanh’s task was to take the parallel algorithms and add the functionality required to work on the segmented hpx::vector. Under his mentor John Biddscombe, he implemented the segmented_fill algorithm, which was successfully merged into the main codebase. Additionally, Minh-Khanh implemented the segmented_scan algorithm which includes inclusive and exclusive_scan. These changes are included in a pull request and have been merged. Using the segmented scan algorithm it is possible to perform tasks such as evaluating polynomials and to implement other algorithms such as quicksort.

Satyaki Upadhyay - Plugin Mechanism for thread schedulers in HPX

In HPX, schedulers are statically linked and must be built at compile-time. Satyaki’s project involved converting this statically linked scheme into a plugin system which would allow arbitrary schedulers to be dynamically loaded. These changes bring several benefits. They provide a layer of abstraction and follow the open/closed principle of software design as well as allowing developers to write their own custom schedulers while conforming to a uniform API. The project proceeded in two steps. The first involved the creation of plugin modules of the schedulers and registering them with HPX. The second step was to implement the loading and subsequent use of the chosen scheduler.

We would like to thank our students and mentors for the time that they have contributed to HPX this summer. In addition, we would like to thank Google for the opportunity that they provided the STE||AR Group to work with developers around the globe as well as the ability for students to interact with vibrant open source projects worldwide.

By Adrian Serio, Organization Administrator for The STE||AR Group

It’s that time again: Google Code-in starts today!

Today marks the start of the 7th year of Google Code-in (GCI), our pre-university contest introducing students to open source development. GCI takes place entirely online and is open to students between the ages of 13 and 17 around the globe.
The concept is simple: complete bite-sized tasks (at your own pace) created by 17 participating open source organizations on topic areas you find interesting:

  • Coding
  • Documentation/Training
  • Outreach/Research
  • Quality Assurance
  • User Interface

Tasks take an average of 3-5 hours to complete and include the guidance of a mentor to help along the way. Complete one task? Get a digital certificate. Three tasks? Get a sweet Google t-shirt. Finalists get a hoodie. Grand Prize winners get a trip to Google headquarters in California.

Over the last 6 years, 3213 students from 99 countries have successfully completed tasks in GCI. Intrigued? Learn more about GCI by checking out our rules and FAQs. And please visit our contest site and read the Getting Started Guide.

Teachers, if you are interested in getting your students involved in Google Code-in you can find resources here to help you get started.

By Mary Radomile, Open Source Programs Office

Stories from Google Code-in: Sugar Labs and Systers

Google Code-in (GCI) is our annual contest that gives students age 13 to 17 experience in computer science through contributions to open source projects. This blog post is the final installment in our series reflecting on the experiences of Google Code-in 2015 grand prize winners. Be sure to check out the first three posts.

The Google Code-in contest begins on Monday, November 28th at 9am PT for students. Right now you can learn more about the 17 mentoring organizations that students will be able to work with by going to the contest site. To get students excited for GCI 2016, we’re sharing three more stories from GCI 2015 grand prize winners. These stories illustrate how global the competition is, the challenges students face and the valuable skills they learn working with these open source organizations.

IMG_20160614_152138.jpg
A group of Google Code-in 2015 mentors joined grand prize winners for a day of exploring
San Francisco including the iconic Golden Gate Bridge.
First up is the story of Ezequiel Pereira, a student from Uruguay who worked with Sugar Labs. Sugar Labs is the organization behind Sugar, the operating system for the OLPC XO-1 which the Uruguayan government has distributed to public primary schools. The XO-1 was Ezequiel’s first computer.

Ezequiel’s curiosity in computer science was piqued when a technician came to his school to solve a simple bug that was affecting most XO’s. The technician used the command line which, up to that point, Ezequiel thought was useless. Realizing that the command line offered him a lot of power, Ezequiel began his exploration.

He discovered Google Code-in by reading about another Uruguayan teenager, one who was a grand prize winner in Google Code-in 2012. Ezequiel jumped into the contest and participated for several years expanding his skills before finishing as a grand prize winner of Google Code-in 2015. Along the way Ezequiel got comfortable with IRC and began helping other students, even finding new friends among along the way.


Next we have Sara Du from the United States. Sara had been coding for six months when she discovered Google Code-in on Christmas Eve, halfway through the competition. She found lots of interesting tasks, but had trouble finding the right organization to focus on before selecting Systers.

Like many students, Sara was able to quickly jump into code but spent a couple days just getting acquainted with Git and GitHub. This is something we hear from a lot of students and it’s just one of the skills that they pick up by working on real-world projects, along with testing and communication.

Another challenge Sara faced was working with a mentor 16 time zones away from her, which meant that correspondence would often take a day or two. While this was a challenge, she found the long feedback loop encouraged her to get on the Slack channel and reach out to other contributors for help. Ultimately, this made her even more a part of the Systers community.

Sara said Google Code-in was one of the most awesome experiences she’s had and has this advice to offer future participants: “The organization you end up working with has a vibrant community of hackers from everywhere; try to interact with them and you will be sure to learn from others as they will from you!”


Last, but certainly not least, we have Ahmed Sabie, a student from Canada who also worked with Systers. Ahmed started coding competitively several years ago, focusing on graph theory, dynamic programming and data structures. He loved the problem solving, but knew that these competitions took place in a sandbox. To grow, Ahmed would need to explore.

Enter Google Code-in. Ahmed was most comfortable with Python and saw that the Systers Volunteer Management System used that language, so that’s where he started.

Ahmed, like many students and even professional developers, spent much of his first week setting up his development environment. It was a grueling process but with the help of search and the people in the Systers Slack channel he was finally able to see the project’s login screen.

As he completed easy tasks, Ahmed moved on to more difficult tasks and began to help other students, many who got stuck on the same issues he had encountered earlier. Ahmed found that each task provided an opportunity to stretch his skills a little bit more. He was excited about how quickly he was learning. Though Ahmed learned a lot on his own, he says the vast majority of what he learned was through the help of other people -- students, mentors and other project contributors -- and that he felt like he was truly a part of the Systers community by the end of the process. 

Ahmed’s favorite task was an appropriate finale for the competition: he added multilingual support to an application he had worked on and added the French translation.
“Overall, Google Code-in was the experience of a lifetime. It set me up for the future, by teaching me relevant and critical skills necessary in software development. I have contributed to a good cause, and met fantastic mentors and friends along the way. Open source development is not a onetime thing, it is an ongoing process. I hope to continue to be part of it, and to me it is a form of volunteering and giving back to the community.” - Ahmed Sabie

With that, we conclude our series of posts reflecting on Google Code-in 2015. We thank Ezequiel, Sara, Ahmed and all the other participants for sharing their stories and contributing to the software we all rely on. We hope you will join us in carrying on the tradition with Google Code-in 2016!

By Josh Simmons, Open Source Programs Office

Google Summer of Code 2016 wrap-up: Linux XIA

We're sharing guest posts from students, mentors and organization administrators who participated in Google Summer of Code 2016. This is the fifth post in that series and there are more on the way.


Linux XIA is the native implementation of XIA, a meta network architecture that supports evolution of all of its components, which we call “principals,” and promotes interoperability between these principals. It is the second year that our organization, Boston University / XIA, has participated in Google Summer of Code (GSoC), and this year we received 31 proposals from 8 countries.

Our ideas list this year focused on upgrading key forwarding data structures to their best known versions. Our group chose the most deserving students for each of the following projects:

Accelerating the forwarding speed of the LPM principal with poptrie

Student André Ferreira Eleuterio and mentor Cody Doucette implemented the first version of the LPM principal in Linux XIA for GSoC 2015. The LPM principal enables Linux XIA to leverage routing tables derived from BGP, OSPF, IS-IS and any other IP routing protocol to forward XIA packets natively, that is, without encapsulation in IP. For GSoC 2016, student Vaibhav Raj Gupta from India partnered with mentor Cody Doucette to speed up the LPM principal by employing a state-of-the-art data structure to find the longest prefix matching using general purpose processors: poptrie.

Upgrading the FIB hash table of principals to the relativistic hash table

Principals that rely on routing flat names have used a resizable hash table that supports lockless readers since 2011. While this data structure was unique in 2011, in the same year, relativistic hash tables were published. The appeal to upgrade to relativistic hash tables was twofold: reduced memory footprint per hashed element, and the fact they were implemented in the Linux kernel in 2014. Student Sachin Paryani, also from India, worked with mentor Qiaobin Fu to replace our resizable hash table with the relativistic hash table.

Google Summer of Code nurtures a brighter future. Thanks to GSoC, our project has received important code contributions, and our community has been enlarged. It was rewarding to learn that two of our GSoC students have decided to pursue graduate school after their GSoC experience with us: Pranav Goswami (2015) and Sachin Paryani (2016). We hope these examples will motivate other students to do their best because the world is what we make of it.

By Michel Machado, Boston University / XIA organization administrator

Google Summer of Code 2016 wrap-up: Debian

This is the fourth post in our series of wrap-ups and guest posts from participants reflecting on Google Summer of Code (GSoC) 2016. Explore the first three posts and stay tuned for more wrap-ups and announcements.



Debian, founded in 1993, is a project aimed at building a 100% free and open source “Universal Operating System.” It’s a volunteer-driven project based on Linux, FreeBSD
and Hurd kernels for devices ranging from mobile phones to large clusters.

Being a wide umbrella project, Debian offered a diverse array of opportunities for Google Summer of Code (GSoC) students. For example, students worked on making our distribution more trustworthy (reproducible builds), porting our OS to Android devices and improving infrastructure for developers. This year I joined the Debian Real-Time Communications (RTC) mentoring team which engaged 13 students to improve voice, video and chat communication with free software.

WebRTC, an open standard enabling real-time video and audio communication in the browser, is central to this work. It was used to create JSCommunicator, an embeddable WebRTC phone developed in HTML, CSS and JavaScript, supporting voice, video and chat using SIP over WebSockets. A GSoC 2014 student, Juliana Louback, significantly enhanced JSCommunicator during her summer with Debian.

JSCommunicator is now being adapted for use with content management systems (CMS) and blogging platforms, making it easy to embed rich communication features in existing systems. It was this work that our current GSoC students built on.

This year I mentored GSoC student Mesut Can Gurle who used DruCall, a Drupal module for integrating JSCommunicator, as inspiration for building WPCall for WordPress. With this new plug-in, standards-based voice, video and chat is now available on the world’s two most popular CMS without the need for browser plugins.

The way WPCall was extrapolated from the DruCall plugin provides a pattern that other communities can follow to rapidly create WebRTC plugins for their own web frameworks. The JSCommunicator Integration Guide provides step-by-step instructions that developers and future students can follow. If you’re interested in learning more about significant developments in this space, please subscribe to the Free-RTC Announce mailing list and follow planet.freertc.org.

This was my first year as a GSoC mentor and I had such a great experience. It was rewarding working with Mesut on achieving his goals and we learned a lot along the way. Despite some setbacks (he narrowly missed a bombing as his country experienced an attempted coup), Mesut has made valuable contributions to free software.

As the summer wound down, I received an invitation to participate in a t-shirt design contest for the annual Mentor Summit. I thought it would be fun to try and put together a design focusing on GSoC’s key values.

The front of the t-shirt shows developers from all over the world collaborating on free software, representing the amazing scope and diversity of the projects. On the back, above the clouds, a space shuttle symbolizes what’s achieved through GSoC.

A group of attendees wearing the Google Summer of Code 2016 Mentor Summit t-shirt.

Happily, my design was selected and it was great seeing all the attendees wearing it at the Mentor Summit!

By Bruno Magalhães, Mentor for Debian

ETC2Comp: fast texture compression for games and VR

For mobile game and VR developers the ETC2 texture format has become an increasingly valuable tool for texture compression. It produces good on-GPU sizes (it stays compressed in memory) and higher quality textures (compared to its ETC1 counterpart).

These benefits come with a significant downside, however: ETC2 textures take significantly longer to compress than their ETC1 counterparts. As adoption of the ETC2 format increases in a project, so do build times. As such, developers have had to make the classic choice between quality and time.

We wanted to eliminate the need for developers to make that choice, so we’ve released ETC2Comp, a fast and high quality ETC2 encoder for games and VR developers.

ETC2 takes a long time to compress textures because the format defines a large number of possible combinations for encoding a block in the texture. To find the most perfect, highest quality compressed image means brute-forcing this incredibly large number of combinations, which clearly is not a time efficient option.

We designed ETC2Comp to get the same visual results at much faster speeds by deploying a few optimization techniques:

Directed Block Search. Rather than a brute-force search, ETC2Comp uses a much more limited, targeted search for the best encoding for a given block. ETC2Comp comes with a precomputed set of archetype blocks, where each archetype is associated with a sorted list of the ETC2 block format types that provide its best encodings. During the actual compression of a texture, each block is initially assigned an archetype, and multiple passes are done to test the block against its block format list to find the best encoding. As a result, the best option can be found much quicker than with a brute-force method.

Full effort setting. During each pass of the encoding process, all the blocks of the image are sorted by their visual quality (worst-looking to best-looking). ETC2Comp takes an effort parameter whose value specifies what percentage of the blocks to update during each pass of encoding. An effort value of 25, for instance, means that on each pass, only the 25% worst looking blocks are tested against the next format in their archetypes' format-chains. The result is a tradeoff between optimizing blocks that already look good, and the time it takes to do it.

Highly multi-threaded code. Since blocks can be evaluated independently during each pass, it’s straightforward to apply multithreading to the work. During encoding ETC2comp can take advantage of available parallel threads, and it even accepts a jobs parameter, where you can define exactly the number of threads you’d like it to use... in case you have a 256 core machine.

Check out the code on GitHub to get started with ETC2Comp and let us know what you think. You can use the tool from the command line or embed the C++ library in your project. If you want to know more about what’s going on under the hood, check out this blog post.

By Colt McAnlis, Developer Advocate

Open source visualization of GPS displacements for earthquake cycle physics

The Earth’s surface is moving, ever so slightly, all the time. This slow, small, but persistent movement of the Earth's crust is responsible for the formation of mountain ranges, sudden earthquakes, and even the positions of the continents. Scientists around the world measure these almost imperceptible movements using arrays of Global Navigation Satellite System (GNSS) receivers to better understand all phases of an earthquake cycle—both how the surface responds after an earthquake, and the storage of strain energy between earthquakes.

To help researchers explore this data and better understand the Earthquake cycle, we are releasing a new, interactive data visualization which draws geodetic velocity lines on top of a relief map by amplifying position estimates relative to their true positions. Unlike existing approaches, which focus on small time slices or individual stations, our visualization can show all the data for a whole array of stations at once. Open sourced under an Apache 2 license, and available on GitHub, this visualization technique is a collaboration between Harvard’s Department of Earth and Planetary Sciences and Google's Machine Perception and Big Picture teams.

Our approach helps scientists quickly assess deformations across all phases of the earthquake cycle—both during earthquakes (coseismic) and the time between (interseismic). For example, we can see azimuth (direction) reversals of stations as they relate to topographic structures and active faults. Digging into these movements will help scientists vet their models and their data, both of which are crucial for developing accurate computer representations that may help predict future earthquakes.

Classical approaches to visualizing these data have fallen into two general categories: 1) a map view of velocity/displacement vectors over a fixed time interval and 2) time versus position plots of each GNSS component (longitude, latitude and altitude).

Examples of classical approaches. On the left is a map view showing average velocity vectors over the period from 1997 to 2001[1]. On the right you can see a time versus eastward (longitudinal) position plot for a single station.

Each of these approaches have proved to be informative ways to understand the spatial distribution of crustal movements and the time evolution of solid earth deformation. However, because geodetic shifts happen in almost imperceptible distances (mm) and over long timescales, both approaches can only show a small subset of the data at any time—a condensed average velocity per station, or a detailed view of a single station, respectively. Our visualization enables a scientist to see all the data at once, then interactively drill down to a specific subset of interest.

Our visualization approach is straightforward; by magnifying the daily longitude and latitude position changes, we show tracks of the evolution of the position of each station. These magnified position tracks are shown as trails on top of a shaded relief topography to provide a sense of position evolution in geographic context.

To see how it works in practice, let’s step through an an example. Consider this tiny set of longitude/latitude pairs for a single GNSS station, with the differing digits shown in bold:


Day IndexLongitudeLatitude
0139.0699040734.949757897
1139.0699040034.949757882
2139.0699041334.949757941
3139.0699040934.949757921
4139.0699041334.949757904

If we were to draw line segments between these points directly on a map, they’d be much too small to see at any reasonable scale. So we take these minute differences and multiply them by a user-controlled scaling factor. By default this factor is 105.5 (about 316,000x).


To help the user identify which end is the start of the line, we give the start and end points different colors and interpolate between them. Blue and red are the default colors, but they’re user-configurable. Although day-to-day movement of stations may seem erratic, by using this method, one can make out a general trend in the relative motion of a station.
Close-up of a single station’s movement during the three year period from 2003 to 2006.
However, static renderings of this sort suffer from the same problem that velocity vector images do; in regions with a high density of GNSS stations, tracks overlap significantly with one another, obscuring details. To solve this problem, our visualization lets the user interactively control the time range of interest, the amount of amplification and other settings. In addition, by animating the lines from start to finish, the user gets a real sense of motion that’s difficult to achieve in a static image.

We’ve applied our new visualization to the ~20 years of data from the GEONET array in Japan. Through it, we can see small but coherent changes in direction before and after the great 2011 Tohoku earthquake.
GPS data sets (in .json format) for both the GEONET data in Japan and the Plate Boundary Observatory (PBO) data in the western US are available at earthquake.rc.fas.harvard.edu.
This short animation shows many of the visualization’s interactive features. In order:
  1. Modifying the multiplier adjusts how significantly the movements are magnified.
  2. We can adjust the time slider nubs to select a particular time range of interest.
  3. Using the map controls provided by the Google Maps JavaScript API, we can zoom into a tiny region of the map.
  4. By enabling map markers, we can see information about individual GNSS stations.
By focusing on a stations of interest, we can even see curvature changes in the time periods before and after the event.
Station designate 960601 of Japan’s GEONET array during the period from 2006 to 2012. Movement magnified 105.1 times (126,000x).
To achieve fast rendering of the line segments, we created a custom overlay using THREE.js to render the lines in WebGL. Data for the GNSS stations is passed to the GPU in a data texture, which allows our vertex shader to position each point on-screen dynamically based on user settings and animation.

We’re excited to continue this productive collaboration between Harvard and Google as we explore opportunities for groundbreaking, new earthquake visualizations. If you’d like to try out the visualization yourself, follow the instructions at earthquake.rc.fas.harvard.edu. It will walk you through the setup steps, including how to download the available data sets. If you’d like to report issues, great! Please submit them through the GitHub project page.

Acknowledgments

We wish to thank Bill Freeman, a researcher on Machine Perception, who hatched the idea and developed the initial prototypes, and Fernanda Viégas and Martin Wattenberg of the Big Picture team for their visualization design guidance.

References

[1] Loveless, J. P., and Meade, B. J. (2010). Geodetic imaging of plate motions, slip rates, and partitioning of deformation in Japan, Journal of Geophysical Research.

By Jimbo Wilson, Software Engineer, Big Picture Team and Brendan Meade, Professor, Harvard Department of Earth and Planetary Sciences