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ACCU 2016 Sessions

Sponsored by:
Undo Software
Mosaic Financial Markets
Skills Matter
Organized by:
Conference Chair:
  Russel Winder
Conference Committee:
  Jon Jagger
  Francis Glassborow
  Olve Maudal
  Roger Orr
  Ewan Milne
  Charles Bailey
  Dirk Haun
Event Manager:
Archer Yates Associates Ltd
Threshers Yard, West Street
Kingham, Oxon. OX7 6YF
Phone: +44 (0) 1608 659900
Fax: +44 (0) 1608 659911
Email: julie at
Conference 2016

"Where xDD went wrong", "Some more of xDD's greatest mistakes", and "What is this xDD thing anyway?"

In this session we’ll take a tour through the emergence and development of the TLA (3-letter-acronym) techniques ending in DD. We’ll consider how they have affected the software development landscape (for good and ill) and explore why they have often fallen short of their stated goals.

There will, of necessity, be copious references to The Hitchhiker’s Guide To The Galaxy.

Opinions stated in this session are Seb’s and are subject to change.

ACCU Issues

Members of the ACCU committee will be available at this session to discuss the issues facing ACCU in a somewhat less formal atmosphere than, of necessity, prevails in the AGM. Topics covered will include local groups, writing for ACCU publications, and ACCU input into the ongoing UK government attempts to improve computer education.

A Day of Deliberate Practice

Knowledge. Skill. Expertise, the skill in applying knowledge. These form the backbone of effective software development. Oh, and fun — with that you get really effective software development.

And that’s what we aim to do in A Day of Deliberate Practice.

Deliberate practice involves careful repetition and reflection to master, explore and understand a technique, to know its boundaries, to make it second nature. We are going to have a day where we discuss and practice software craftsmanship, communication and creativity, focusing on TDD, pair programming, trying out new things and revisiting old ones.

If you code everyday and were thinking of taking a break during the conference, keep in mind that a change is as good as a rest — yes, there will be coding, but it’s not your workaday coding. We will be using cyber-dojo (, an innovative, collaborative, open source, browser-based environment (so bring a laptop). We are going to have fun — join us!

A Glimpse of Trygve: From Class-oriented Programming to Real OO

Though it’s called "object-oriented," C++ programming tends to be rooted in classes rather than objects. And while you can do OO programming in C++ if you work hard enough, some languages like Java make it almost impossible. While it’s likely that Dahl and Nygaard understood real OO, their Simula 67 language was limited in its expression of those ideas. Alan Kay later made the OO vision more concrete, named it, and even reduced much of it to practice around 1970. However, as Smalltalk evolved it became increasingly class-oriented. At one point Kay said that they should burn all the Smalltalk tapes and move on, but the world had fallen in love with itself and its preoccupation with classes. While a few object-oriented languages like JavaScript survived, most languages took the class direction.

Kay’s Vivarium started to take OO in the direction of emergent system behavior. While suitable for social phenomenæ like the Internet, it gives pause when considering Tony Hoare’s admonition: "I conclude that there are two ways of conntructing a software design: 1. Make it so simple that there are obviously no deficiencies 2. Make it so complicated that there are no obvious deficiencies. The first method is far more difficult.” We’re still stuck with writing programs to deliver to the mental models of businesses and their stakeholders. While Kay took the emergent path, MVC took a human-centric path.

The open sourced trygve language is the world’s first attempt to create a language that faithfully implements the Data-Context-and-Interaction (DCI) paradigm pioneered by Trygve Reenskaug (inventor of MVC, too) and Jim Coplien (who proposed a bit of OO thinking in his Advanced C++ 25 years ago). In this talk we’ll give a glimpse of what OO is all about and talk a bit about how trygve supports it.

A Meta-pipeline for Generating Continuous Delivery Pipelines for Microservices

At SpringerNature the development group is adopting microservices. They found that having developers set up build pipelines by hand for each service was time-consuming and led to inconsistencies as our environment changed, so they automated the process.

The team developed a meta-pipeline that will generate a continuous delivery pipeline for any of their repositories that follow a set of conventions – their Meta-Pipeline Protocol.

This will have been presented at SoftwareCircus (Amsterdam), and Agile Cambridge.

Standardising their pipeline definition has greatly reduced the team programmers' effort and allowed them to safely evolve their build environment. They’re starting to exploit this meta information to improve their overall environment, for example: to visualise relationships, to manage the running of client contract tests, and to profile build timings.

A Practical Introduction to User Story Mapping

Jeff Patton introduced user story mapping as an analysis and planning technique a decade ago, and documented through blog posts and conference talks. Last year, he published a book that goes into much greater detail, but organisations often encounter difficulties when trying to apply the techniques.

In this workshop, Seb will give you a thorough understanding of what user story mapping is, what contexts it is useful in, and what problems it helps to solve. You will also learn what it is not – and when it is not helpful.

Through a combination of slides, discussions and in-depth, hands-on exercises, you will finish the day with the knowledge and experience to try user story mapping for real.

A Taste of Julia

Julia is a recent programming language developed at MIT and sold as a high level, high performance dynamic language for scientific computing. One of the co-authors of Julia has a Scheme background, and in fact, it appears that Julia borrows a lot from Scheme, Common Lisp and Dylan. This is to the point that Julia may even be considered as a new Lisp dialect. This is enough, already, to catch our attention, but there’s more. Julia also seems to benefit from modern optimization techniques for dynamic languages, notably through its LLVM based JIT compiler. In this talk, we will give a tour of the language’s most prominent features, with a slight focus on what makes it a Lisp, sometimes (not always) an even better one that the existing alternatives.

Algorithmic Architecture: Performant Architecture in Evolving Regulatory Environments

In complex, highly regulated (and therefore constrained) environments it is a continual struggle to develop high performance systems and adapt them as constraints evolve. Typical architectures stagnate and performance improvements are focused more and more on known pain points with considerable (even heroic) effort employed to address them. Eventually that too is not enough and systems need to be re-architected and re-written. Ultimately leading to costly 3-5 year regeneration programs.

With the sweeping regulatory changes brought on by the 2008 Financial Crisis and the 2010 Flash Crash as a backdrop, the talk explores regulations, and problems, and their impact on architecture. Such regulatory changes only add to the already huge pressure on system implementors to provide high performance, ultra-low latency, throughput-scalable and highly available systems.

The talk looks at how these competing forces ― the desire for optimal performance coupled with a need to adapt to an ever changing regulatory environment, or indeed changing constraints in general ― have catalysed our work at to adopt an “algorithmic architecture” approach. This has allowed us to maintain agility while also facilitating the development of optimal systems based on solid architecture. It also turns out that C++ is a language is well suited to supporting the approach though the techniques are themselves language agnostic.

Balancing Bias in Software Development

Despite increasingly sophisticated tools, methods, and environments, many software projects still fail. One way to address this is to focus on developers, rather than just on tools. This talk will draw on psychological theory and evidence concerning ‘cognitive biases’ – mental behaviours that prejudice decision quality – in order to consider the influence of cognitive biases on software development. The talk will identify particular biases that seem to be particularly relevant (such as confirmation biases and inertia biases), and then draw insights from empirical studies of professional software developers to illustrate how expert practices can ‘balance’ bias during development.

Become a GDB Power User

If you’re writing C++ for anything other than Windows, chances are that you occasionally break out GDB. This session presents some of the lesser known features of GDB that can change the way you debug. GDB has come a long way in the last few years and does so much more than break, print, step and continue. Reversible debugging; Non-Stop Mode; Multi-process Debugging; and Dynamic Printf are but some of its best features, and its built-in Python scripting is particularly powerful. Join Undo Software co-founder and CEO, Greg Law, as he takes you through a series of demos to show some amazing tricks with GDB, and powerful new (and not-so-new) features that you may not have heard of.

Benchmarking in C++

A commonplace among talks on benchmarking is the assumption that a stopwatch - a time measuring mechanism already exists. While this may seem a mundane endeavour it is of great importance to have a reliable, cross platform, easy to use framework for performing "benchmarking experiments".

In this talk we’ll walk through the proper use of <chrono> to create such a framework, having the following features:

  • Parametrizable time and clock type per benchmark.

  • Multiple experiments can run on the same benchmark (hence we can group and compare results as we wish).

  • User adjustable sampling size (number of times each experiment will run).

  • Auto detectable sampling (number of times the experiment has to run until we "trust" its results)

  • Benchmarks printable and serializable in a “Python friendly” form.

  • A Python script to read the output of a serialization and make graphs using matplotlib.

Big Data Analytics – A Primer for the Adventurous

This talk is about big data analytics. Big data has been talked about for a number of years now. You know it’s important when it’s the topic of conversation around many water coolers, snack and coffee machines around coding frenzy places. Above all Dilbert talks about it and so that should be the cue to take interest. Hence the reason for talking about this.

During the talk we will be addressing the following:

  • What is Big Data?

  • Why Big Data?

  • What is new?

  • Where is it being applied?

Considering the battle hardened code warriors ever present at ACCU we will be doing a deep dive into a real world application using Apache Spark in two domains: biomedical and financial reporting.

C++ Concepts "Lite" in Practice

One of the features that did not make the C++11 standard was concepts, but a revised proposal has now been published as a Technical Specification for Concepts (the so-called "Concepts-Lite").

Concepts were designed to help with improved compiler diagnostics and to allow programmers better tools to expresses formal requirements for templates.

An implementation of Concepts is available in the trunk of gcc, so we now have a mainstream compiler we can experiment with.

The talk is designed to help people understand what problems the concepts proposal is designed for and demonstrate how this works in practice. It will require knowledge of C++, but no prior exposure to concepts is required.

I will look at some of the background of concepts as well as producing and working through various examples of concepts in action.

C++ Pub Quiz

Join us for a pub quiz on C++! You will be working in groups where I present interesting code snippets in C++ and you will discuss, reason about and sometimes need to guess what the code snippet will print out. There will be many educational snippets where we elaborate on the basics of C++, but some of the snippets will be really hard with surprising answers and where we explore the dark and dusty corners of the language.

Code History Analysis and Visualization

In software development industry most projects have quite detailed history of changes stored in version control systems. It is relatively easy to access change history but we mostly focus on changes in specific areas (e.g. when particular line of code was added) and rarely look at project history as a whole.

This session is a demo of code history analysis and interactive visualizations for some well-known projects like JUnit and IntelliJ IDEA. The idea is that it can be used to get an overview of unfamiliar project or get insight into project you are currently working on. The main goal of the session is to showcase ways in which history can analysed and inspire audience to try these techniques on their own projects.

Some of the visualizations:

  • Code churn (commits/files/lines of code in codebase per day/week/month).

  • Number of unique committers per day/week/month. The idea is to see the number of people contributing to the project and trend of the project.

  • Average amount of files in commit per day/week/month. Assuming that commit is a finished unit of work, the idea is to see how its size changes over time.

  • Files changed in the same commit several times.

Comfort Zone

We all have our comfort zones – probably lots of them! Conversely, there are many things that make us feel uncomfortable (and sometimes, very uncomfortable). These can affect anything from the types of foods we eat and the way we interact with each other in our day to day lives to the way we work and the type of environments we prefer to work in.

What those comfort zones are varies dramatically from one person to another, but what isn’t in doubt is that although some can help us, some will hinder us – sometimes massively.

So why do we have comfort zones? And how can we make use of them to improve the way we do things?

Concurrent Thinking

One of the most difficult issues around designing software with multiple threads of execution is synchronizing data.

Whether you use actors, active objects, futures and continuations or mutable shared state, every non-trivial system with multiple threads needs to transfer data between them. This means thinking about which data needs to be processed by which thread, and ensuring that the right data gets to the right threads in the right order. It also means thinking about API design to avoid race conditions.

In this presentation I’ll describe techniques we can use when doing this "thinking", as well as the tools we have available to help us describe our requirements and enforce them in code.

All examples will use C++, but the thought processes are widely applicable.

Constant Fun

This presentation discusses why it is useful to move some of the processing to compile time and shows some applications of doing so. In particular it shows how to create associative containers created at compile time and what is needed from the types involved to make it possible. The presentation also does some analysis to estimate the costs in terms for compile-time and object file size.

Specifically, the presentation discusses:

  • implications of static and dynamic initialization – the C++ language rules for implementing constexpr functions and classes supporting constexpr objects.

  • differences in error handling with constant expressions.

  • sorting sequences at compile time and the needed infrastructure – creating constant associative containers with compile-time and run-time look-up.

It is expected that attendees have a working knowledge of C++ but no prior knowledge of using constexpr is required. The code samples will contain lots of templates and sometimes unusual uses of the language.

Continuous Delivery with Docker Containers

This full day workshop will introduce you to docker and give you hands-on experience with setting up a continuous delivery pipeline with docker containers. You will learn to define images for build and runtime, use them as part of your continuous integration setup, and deploy them automatically.

This will all be done in a lab environment and you are expected to bring a laptop. Prepare to get your hands dirty!

Attendees will learn and understand:

  • What docker is and how to use it in software development

  • An understanding of how to build docker images

  • How to use docker images in a jenkins CI server

  • How to share your images with docker hub and docker registry

  • How to spin up a continuous delivery environment using docker containers

Declarative Thinking, Declarative Practice

Do this, do that. Coding from assembler to shell scripting, from the mainstream languages of the last century to the mainstream languages now, is dominated by an imperative style. From how we teach variables – they vary, right? – to how we talk about databases, we are constantly looking at state as a thing to be changed and programming languages are structured in terms of the mechanics of change – assignment, loops and how code can be threaded (cautiously) with concurrency.

Functional programming, mark-up languages, schemas, persistent data structures and more are all based around a more declarative approach to code, where instead of reasoning in terms of who does what to whom and what the consequences are, relationships and uses are described, and the flow of execution follows from how functions, data and other structures are composed. This talk will look at the differences between imperative and declarative approaches, offering lessons, habits and techniques that are applicable from requirements through to code and tests in mainstream languages.

Design Patterns in Modern C++

The original Design Patterns book was written in the early days of C++ when none of the modern constructs were available and the current issues (such as parallelism) weren’t so pressing. A lot of time has passed since then, with Design Patterns being adopted in all OOP languages that have come since then. In this talk, we’ll take a look at some of the ways to adapt the patterns, which are as relevant as ever, to use Modern C++.

Distributed Mutual Exclusion using Proposed Boost.AFIO (asynchronous filesystem and file io)

Developing from the surprisingly popular CppCon 2015 tutorial “Racing the filesystem” ( on the concurrency fundamentals of the file system, this workshop takes the audience from the fundamental first principles of the file system through to a working and high performance distributed mutual exclusion implementation exclusively using atomic file append messaging based on a modified Maekawa-Suzuki-Kasami distributed voting and mutual consensus algorithm.

Along the way the portable asynchronous file system model supplied by proposed Boost.AFIO will be explained and how such a standardised programming model makes implementing write-once run-anywhere file system algorithms much more tractable. Empirical benchmarks will be shown comparing the scalability of our algorithm to other forms of file system based mutual exclusion such as lock files and byte range locking across Microsoft Windows (NTFS and ReFS), Linux (ext4) and FreeBSD (ZFS). One of the major advantages of our algorithm is that it works perfectly over SMB networked file systems, including mixed POSIX and Microsoft Windows endpoints, and it will be explained how this is not always the case with other mutual exclusion techniques.

With a live demonstration of the working algorithm, the likely audience for this workshop would be similar to that for lock free programming using memory atomics, however the file system exposes a much richer suite of fundamental primitive operations – and unexpected surprises!

Efficient and Accessible? Addressing New Architectures in C++

Moore’s law is failing, as many have observed. Physical limits on the design of processors mean that it is no longer true that CPUs will simply scale in performance from year to year. Processor designers have attempted to address these limitations using deep cache hierarchies, vector pipelines and increasing core counts but exploiting these capabilities tends to need changes in algorithms and data structures.

I will discuss the nature of this challenge, the reasons behind it and what can be done to address it and most importantly, if this can be achieved while maintaining, or even improving, the expressiveness of code.  While the abstract machine model underlying C is a thing of the past, I’ll include working examples of what can be achieved in C++.

Elegant Filesystem Interactions in Python using pathlib

Anyone who has written python code to manipulate files and directories, will be familiar with the os and os.path modules. Starting with Python v3.4, there’s a new kid on the block - pathlib - which provides a fresh interface to querying and manipulating the filesystem.

This short session will introduce pathlib, and demonstrate how it can be used to avoid littering your code with calls to os.path.* functions. We will go through examples of how rewriting code to use pathlib makes it shorter and more readable.

Finally, we will conclude with a look ahead, noting where pathlib still has some ways to go before it has become a fully integrated part of Python.

Extending and Wrapping C and C++ with Python

C and C++ languages are paramount of efficiency, and probably have the largest quota on the market, implementing the backbone of all of the existing computing infraestructure, including other programming languages. On the other hand, python is in rise, with its amazing simplicity is being adopted as the generic language for learning and many other tasks ranging from BigData and systems to web sites.

This talk will introduce how both languages can work together. It will explore different ways in which C and C++ libraries can be wrapped and used by python programs, but also how python code can be embedded and called from C and C++ applications.

Especial focus will be put on portability,  how to handle different types of libraries, as static and dynamic libraries, and how the final result can be distributed.

The talk will provide simple and fully operational examples and demostrations, that can be useful as a starting point for the interested audience, and that will show how to get the best of both (C/C++ and python) worlds as a powerful programming environment for real use cases.


To some extent, optimization is to our industry what sexual intercourse is to teenagers. There’s a veil of awesomeness surrounding it; everybody thinks it’s cool, has an angle on it, and talks about it a great deal; yet in spite of ample folklore, few get to do it well, meaningfully, or at all.

Improving the ordeals of teenage years being too large a project, the next best thing to do is teaching how to write fast code. So Andrei set out to write a book about it.

This talk is a sneak preview into some of the book’s material.

Finding Bugs with Clang at Compile and Run Time

Code-Analysis and Verification gains more and more importance within programming and quality assurance of software projects. Especially in languages like C/C++ undefined behaviour and memory leaks can cause great problems. Static analysis tools help a lot but often hard to detect problems happen at runtime.

In this session we will use clang’s features to find bugs at compile time (via static analysis) and runtime (via sanitizers). The combination of both approaches can improve software quality a lot. First we will look how clang is able to detect common C/C++ traps and pitfalls via static analysis. Additionally we will write our own code checker to implement one of Scott Meyers Effective C++ rules. So expect to see an editor
code and not only slides ;-)

Second, we will look at sanitizers which enable code instrumentation and detection of problems which happen at runtime. Problems like undefined behaviour, memory leaks, data races and un-initialized read from memory can be found by special sanitizers and we will look how each of them works. I will do some coding during the session and show how the static analysis and sanitizers help to catch bugs. We will also talk about experiences applying this technique to a large C++ project.

Go! Steady. Ready?

I am a C++ and a Python programmer. My team ships products written in C++. We’re all proficient at C++. Despite this, we use Python whenever we can. We use Python for internal tools: system tests, web applications to present information stored in a database, scripts to automate tasks, and so on. We even use Python to prototype new features for the products we ship.

Despite their differences, Python and C++ have much in common. Both languages have their roots in C, which they extend in similar ways. Both add support for object-oriented programming, generic programming, functional programming, exceptions, standard containers and so on. But both omit key features from their predecessor. C++ is complicated. Python is slow.

For these reasons, I’ve been following the development of Go with interest. It’s a new language based on some old ideas. It can be seen as a modern reinvention of C. If C succeeded – and continues to succeed – because it models the basic operation of a digital computer, then Go pitches itself at the distributed, concurrent world.

Go promises the simplicity, safety and convenience of a language like Python, and adds solid performance, unobtrusive static typing and language-level support for concurrent programming. I’ve been experimenting with Go. This talk reports back on my experience.

I’ll attempt to answer the question: does Go deliver on its promises?

How I Went from C++ Programmer to Running My Own Software Product Company (and you can too)

Many software developers dream of escaping bosses, cubicles and TPS reports to start their own software product business. But they are put off the distorted 'Google or bust' image of starting your a software business portrayed by the media. I will discuss what it is really like to make a living selling your own software product online. I will be covering topics including:

  • how much money do you need to start your own business?

  • do you need a co-founder?

  • do you need employees?

  • how much red tape is involved in running a company?

  • how do you know if there is a market for your product?

  • choosing a platform: desktop, web or mobile?

  • how do you promote your product?

  • how painful is it to do support for non-technical people?

  • can you make more money than working for other people?

  • how do you take a holiday?

I hope to keep it interactive and am happy to answer questions on anything to do with starting your own software business.

How to Apply Engineering Practices to Embedded Software Development

A steadily increasing number of things for everyday use have more and more software embedded. If that software is not carefully crafted then we may be facing a dystopian future where we’ll be enslaved by dysfunctional technology.

Over the last few decades various engineering practices have been introduced to support the development of functional software. Unfortunately the field of embedded software struggles with applying these practices.

In this session I demonstrate an example of a walking skeleton for an embedded software project. By studying the example we discuss some of the engineering practices and we will see that these can be applied to embedded software development as well.

We will talk a lot about growing software guided by tests. Other topics include for example how to maintain a cross toolchain for reproducible builds.

How to Evolve Your Way Out of a Paper Bag

Machine learning is all the rage. We usually find, however that machines don’t learn. We have to give them some hints or actual code in order to get anything done. Furthermore, we are often told many people can’t program their way out of a paper bag. Frances Buontempo can. She will explore evolutionary algorithms, a type of machine learning, including genetic algorithms (ga) and cell automata (ca) in the simple context of programming one’s way out of a paper bag. The audience will understand the basics of evolutionary computing by the end of the talk, and be knowledgeable enough to try the ideas against other problems. Frances promises to keep it simple and have some moving pictures to show off during the session.

Improving Performance and Maintainability in Modern C++

In this talk I will provide additional details on the article recently posted to "Improving performance and maintainability through refactoring in C++11" (please, see as well as updates on recent findings.

Abstraction based programming has been traditionally seen as an approach that improves software quality at the cost of losing performance. However, we explored the cost of abstraction by transforming an application of the PARSEC benchmark (namely fluidanimate application) from low-level, hand-optimized C to a higher-level and more general C++ version that is a more direct representation of the algorithms. We eliminated global variables and constants, used vectors of a user-defined particle type rather than arrays of built-in types, and separated the concurrency model from the application model. The result is a C++ program that is smaller, less complex, and measurably faster than the original.

The fluidanimate application was chosen to be representative of many applications and our transformations are systematic and based on principles. Consequently, our techniques can be used to improve the performance, flexibility, and maintainability of a large class of programs. The handling of concurrency issues has been collected into a small new library, YAPL.

Although the main focus of the talk will be the design principles and techniques that are generally applicable, we will also provide evaluation information on multiple architectures showing the impact on performance.

Keeping Your CI–CD Pipeline as Fast as it Needs to Be

First, you automated your build. Then your build grew out of control, it took so long that you couldn’t afford to run the whole thing after each commit, so you decided to split it into modules that trigger each other as needed. Now you have a large chain of builds, each of them taking a short amount of time (brilliant!), but each time you commit you don’t just build one thing, you build and rebuild so many modules that it, again, takes for ever to clear up every time you commit a change. In this talk I’ll show you what information you need to gather from your CI/CD pipeline, and how you can gather such information, in order to re-shape the architecture of your systems so as to optimise your build time.

Leaving the Dark Side

A story with code about 5 years learning: developing a c++ based medical device, successful again.

Let's Not Repeat the Mistakes of SOA: 'Micro' Services, Macro Organisational, Architectural and Operational Challenges

The technology changes required when implementing a microservice-based application are only one part of the equation. The business and organisation will also most likely have to fundamentally change. In an ideal world, this shouldn’t be a problem - what with the rise of agile, lean and DevOps - but this is not always the situation Daniel encounters in his consulting travels. He would like to share with you some stories of successful (and not so successful) strategies and tactics he has used over the past four years when introducing service-oriented architecture into organisations.

Join Daniel for a whistle-stop tour of the business and people challenges that he has experienced first hand when implementing a greenfield microservice project, and also breaking down a monolith. You will discover ‘divided companies’ vs ‘connected companies’, determine the actual impact of conway’s law, briefly touch on the lean startup/enterprise mindset, dive into change management without the management double-speak, and look at the lightweight processes needed to ensure the technical success of a microservices implementation.

Managing C++ Build Complexity Using Cuppa: A SCons-based Build System

Building C++ projects is often a complex task with some team members becoming "build" specialists holding the arcane knowledge required to manage a convoluted collection of scripts and make files (including bjam and cmake). SCons, like bjam is a true make replacement but unlike bjam does not require developers to learn yet-another-make-syntax. However, just like make and bjam SCons is a low level tool to help reason about dependencies. Cuppa was written to leverage the extensibility of SCons but to make it easy to solve common build problems in a consistent way. It offers the familiarity of make-like usage but with the very simple, declarative SConscript files.

Key goals of Cuppa are to provide a consistent model for describing what and how things are to be built, in a simple declarative manner, as well as making it easy to encapsulate complex or remote dependencies so that they can be made available automatically during the build process. This makes it trivial to build multiple build variants for multiple toolchains to exactly the specifications required. Being "just Python" there is no need to learn another language and cooperative build ownership becomes much simpler.

This tutorial will introduce Cuppa along with examples of its use. We will also introduce concepts like Cuppa dependencies and show how it is possible to make larger more complex dependencies like boost available for use. In fact boost and Qt are pre-defined dependencies that can be used out-of-the-box with your C++ projects with no, or minimal, fuss. Lastly we will discuss the Cuppa location model that allows dependencies to be expressed as source locations (perhaps in remote version control) so that you can control which specific versions or revisions a given project is to be built against.

Monitor Your Services

Service monitoring is much more than checking that your service is running. Monitoring helps you understand how your service is behaving, help tuning for best performance, understand your customers. Monitoring helps you understand why your service crashed or didn’t survive the last DOS attack. Monitoring helps you identify bottlenecks and predict future hardware needs.

This talk will describe what monitoring can do for your service and your business. I will give examples of things to monitor and some interesting  findings that monitoring has revealed. I will go through different classes of metrics and event logs and how to make sense of large volumes of them.

What monitoring systems are available or do you need to build your own? This depends on what metrics you have and need. I will go through some examples and what metrics they need and how available monitoring systems would support and present them.

Moving your Grid to the Cloud – or "Hardware, Who Needs Hardware?" or "Architecture Revisited"

In a previous life, I built a large (for the time) compute cluster for an Investment bank. It took a team of up to 20, full time, a year just to build the software. On top of that there was huge upfront investment in data centre rackspace, hardware, etc. The implementation language wasn’t ideal, nor was the platform, but it worked.

I’ve revisited this problem more recently to see how this problem can be solved 10 years later. The short answer is: Building custom compute grids has become much easier, and much much cheaper. I will discuss how we arrived at the architecture, what forces were driving it, and how it fares in the modern world. Can the same architecture work in such a different environment?

Presentation time permitting, I will address different cloud platforms, as well as go into detail how, for specific sub problems, specialised hardware can replace whole racks of machines.

Mutation Testing in Python

Mutation testing is a technique for systematically mutating source code in order to validate test suites. It operates by making small changes to a program’s source code and then running a test suite; if the test suite ever succeeds on mutated code then a flag is raised. The goal is to check that a system’s test suite is sufficiently powerful to detect a large class of functionality-affecting changes, thereby helping ensure that the system functions as expected. While not in widespread use, mutation testing is a fascinating topic with great potential that has valuable lessons for the broader software development community.

I’ll begin this talk with a description of the theory behind mutation testing. We’ll look at how it works and the benefits it can provide. We’ll also consider some of the practical difficulties associated with the technique, including long runtimes and certain difficult classes of mutants. I’ll then move into an analysis of Cosmic Ray, a tool for mutation testing in Python. While some of the details of this talk will necessarily be Python-specific, the concepts and lessons are broadly applicable and should be interesting to anyone involved in producing software.

Predictive Models of Development Teams and the Systems they Build

It’s awkward to perform science experiments on developers, so let’s simulate them instead! The emerging field of software process dynamics applies systems thinking and simulated experiments of software development teams and the systems they build, to inform decisions on projects, process and architecture.

In 1968 Melvin Conway pointed out a seemingly inevitable symmetry between organisations and the software systems they construct. Organisations today are more fluid than 40 years ago, with short developer tenure, and frequent migration of individuals between projects and employers. In this slot we’ll examine – and perhaps collect – data on the tenure and productivity of programmers and use this to gain insight into codebases, by simulating their growth with simple stochastic models. From such models, we can make important predictions about the maintainability and long-term viability of software systems, with implications for how we approach software design, documentation and how we assemble teams.

In the second part of the talk we’ll build a software dynamics model simulating the growth of a system, and the flow of code change, before concluding with the remarks on the nature of modelling and the basics of making your own models.

Proper Inheritance

All essential behavior of our software must be documented, and yet there are important advantages, with respect to development, verification and testing, performance, and stability, for leaving the behavior for some combinations of inputs and initial conditions undefined. What is and is not defined behavior should therefore be readily discernible from the contract, especially when creating contracts that must span classes related by inheritance.

In Part 1 of this talk, we review components, interfaces and contracts in general, and the significance of narrow versus wide contracts in particular. In Part 2, we explore three kinds of inheritance: (1) Interface Inheritance resulting from pure-virtual functions; (2) Structural Inheritance resulting from non-virtual functions; and (3) Implementation Inheritance resulting from non-pure virtual functions. Proper contracts involving each of these distinct forms have different criteria that must be addressed. The three kinds of inheritance are compared, and their relative utility is explained. What’s more, several common uses of inheritance that are probably improper are summarily debunked.

Property Based Testing Hands-on in Haskell or Javascript

Most unit/integration testing as we know it is example-based: we describe examples of how the code under test behaves in our favourite testing framework.

Property based testing is a new and promising approach to automated unit testing. It is very different from example-based approaches: in property based testing, you don’t write examples but you describe properties of the code under test (statements about the outputs based on the inputs). Based on this, a property-based test framework generates many different inputs and checks if the code under test satisfies everything.

It started in QuickCheck in the functional programming language Haskell and currently frameworks are available for many languages, from Java/Scala to C++.

Property based testing forces you to think carefully about specifications: what are the preconditions, postconditions, invariants? It looks like a useful new tool for the crafts(wo)man’s tool chest. This session will give you a good impression of how it works and what possible applications could be.

You’ll get written instructions for a language of your choice, either javascript (jsverify) or haskell (quickcheck) and hands-on coaching.

Reduce: From Functional and Heterogeneous Programming to C++17 Fold Expressions

In its simplest form, reduce turns into summing the contents of a sequence but in functional programming, reduce refers to a family of higher-order functions that analyze a recursive data structure and through use of a given combining operation, recombine the results of recursively processing its constituent parts, building up a return value.

In this talk we present the concepts behind reduce using Python and check the ways we’ve always had in C++ to express the same ideas. Then a presentation of "Folds" is given, which is the modern C++ "reducer". Building on the language features we already have, we explain why "reduce" is more general than "filter" or "map" and how it can be used to implement them.

These ideas are further extended to transducers, a modern concept that first appeared in closure, and has implementations both in Python and C++. Using the tools provided from transducers we demonstrate how to implement fold expressions for any binary operators. We finally address the importance of "reduce" in parallel and  heterogenous programming and talk about the "parallel reduction problem".

Algorithms like the "parallel prefix sum" and "map reduce" are showcased in CUDA C++ and C++ respectively.

Refactoring: 25 Years On

It’s been some 25 years since ‘refactoring’ was suggested and is now central to programming practice. But how is refactoring conducted today compared to its original notions? After a quick recap on the original ideas of refactoring, this workshop explores the intent and principles of refactoring in contemporary practice, and also considers the robustness and (semi-) automated support provided by refactoring tools. This workshop is highly interactive, and highly driven by participants. The workshop begins with a short overview of how refactoring came about in the 1990s. Central to the impact of refactoring was tool support during development, and the suggestion that (semi-) automation could take away (at least) some of the tedium of repetitious restructuring.The workshop then forms small breakout groups to consider what the intent and principles of refactoring might be in a contemporary context. For example, the original intent of refactoring was to bring out design-level restructuring e.g. duplication avoidance. But is it now the case that refactoring relates to more fine-grained (code) changes? Moreover, the fundamental principle of refactoring is that restructuring is semantic preserving. But is this strictly necessary at a fine grained code level? Might minor changes in program behavior be tolerated for the sake of improved elegance in design and code? Findings are shared and discussed around the workshop. Next, the role of the automated tool support for refactoring is explored. For example, how robust is contemporary tool support? Are refactoring tools error free? Do they even introduce errors in design and code? After refactoring, is a simple syntax check sufficient? Also, how proactive are refactoring tools in their support? Should they be present in development IDEs, possibly as recommendation engines, or might they work offline from a command line, for example. For a second time, building on the ideas discussed, participants form into small breakout groups. Finally, the workshop brings together the findings of the participants for analysis and reflection.

Refactoring to Streams

Learn how to express your algorithms in Java 8 Streams

The streams and lambda expressions introduced in Java 8 give programmers access to some advanced functional abstractions. In this tutorial we look at how to refactor imperative code to take advantage of this style. We start by removing for-loops and work our way through mapping and reducing to advanced parallelism.

The format of this session is a group tutorial. We have a number of exercises that we attempt as a mob-programming session, so that everyone can participate and no-one is left behind. The exercises and solutions are available on GitHub for those who want to try them in their own time.

Whilst the exercises are in Java, the techniques would suit C#, Python, Ruby, etc.


Analyzing objects, rewriting history and migrating your team to a healthier repository.

Many people have heard that Git does not handle large files or binary files very well and that it needs extensions to do things properly. But how true is this, how large is large, and what is special about "binary" files?

In this talk I’ll show how to use a new option to 'git cat-file' to analyse what is taking up the space in your repository and how effective Git’s delta compression is in your repository.

There are many tools and lots of information available on how to rewrite a repository’s history, should you decide that this is necessary. I shall demonstrate one way to rewrite history and talk about the merits of a number of the other options including erasing objects, replacing objects and migrating objects to alternative storage, including migrating to a solution such as git-lfs.

Rewrite without Rewriting

We have an application based on a 20 year old proprietary product, a graphics library and scripting language, now both well past their sell-by date and a serious concern as we try to position it for the next 10 years. A ground-up rewrite is impossible for several business reasons.

This is the story of how we’re trying to transition to Python and Qt piece-by-piece, running both languages and graphics libraries side-by-side in the same executable. If it’s been a while since you saw a Motif dialog, come and refresh your memory.

STL Algorithms – How to Use Them and How to Write Your Own

The STL contains a collection of containers, which everyone knows about, and a collection of algorithms, which are less well known. In this session, I will talk about the algorithms that are in the STL, how they are designed, and talk about writing your own algorithms that work in the same style as existing ones.

Seven Languages in 90 Minutes


Broaden your horizons by looking at solutions to common problems in different languages.


Inspired by the book 'Seven languages in seven weeks': You should learn a programming language every year, as recommended by The Pragmatic Programmer. But if one per year is good, how about Seven Languages in 90 minutes? In this session you’ll get a hands-on tour of a few programming languages. Whether or not your favorite language is on that list, you’ll broaden your perspective of programming by examining these languages side-by-side.

Small Steps towards Better Technical Presentations

Have you ever had that nagging feeling that your presentations could be "better" but you just didn’t know how exactly? You’ve read recommendations in books and articles but they require too much time and they just don’t seem to be written with technical presentations in mind. And so you continue doing presentations the way you always did them. After all, nobody ever really complained about them, so they can’t be that bad.

If you’ve ever had thoughts like that, then this is the workshop for you. We’re going to look not so much at "why" you should change the way you’re doing presentations but at the "how". The aim is to get you started on your way towards better, more effective presentations that are more focussed on your audience’s needs. You’ll be getting tips on improving what you already have and learn how to approach your next presentation.

This is a workshop, so please bring a presentation you want to work on, in whatever stage it currently is – an idea, a set of notes, or a finished slide deck – and we’ll see what could be improved.

Snowden and the Snoopers – a.k.a. One persons's surveillance state is another's sensible precaution

The technology we create intimately influences every individual’s life. "Without software – nothing works" (Uncle Bob).

This puts our profession in a position of great responsibility:

We collect huge amounts of data on people and have big choices to make, both personally and as a society about who controls access to this data, and what uses are, and aren’t, ethical.

Is there really a trade off between privacy and security, or is that a false premise?

What are the ethical choices in our professional life? What duty do we, as computing professionals, have in informing public opinion and government policies?

This talk will take the form of – hopefully – animated discussions.

Software Architecture: Living Structure, Art or Just Hopeful Arrangements of Bytes?

In a recent chat with a friend I looked back on my career of over 35 years as a programmer. It was disheartening to realize that it took me more than 15 of those years before I was happy enough with the software structures I was producing. Subsequently it has been a frustrating process to try and find software developers who have such a structural or architectural awareness.

Why is this? Are there better ways to develop such awareness? Or must we accept the negative view that you either get it or you don’t? Along with its jaded corollary: If you don’t get it – you never will?

Having presented in previous ACCU conferences on the links between software development and phenomenology, the presentation will be based upon my interest in this experiential approach of knowledge development, and will draw on Christopher Alexander’s ideas of living structure, as well as a few of my own experiences with watercolour painting!

I hope to show how these seemingly disparate domains relate to developing sustainable software architectures, and will give ourselves time to share insights about how we could develop better architectural awareness in less than 15 years!

Swift for the Curious

At less than two years old, Swift – Apple’s new programming language – is already at Version 2, has undergone significant development, and has now been fully open-sourced! It’s had one of the fastest adoptions of any new language ever (for reasons we’ll discuss) and has been turning the world of Apple development on its head.

But what’s different about it? How does it fit in with other modern languages? Is it a functional language, as some rumours have suggested? Does it have any unique features? Should you care about it at all if you are not in the Apple eco-system (or even if you are)? We’ll look at answers to at all these questions and get a flavour of the language itself.



Teaching Modern Software Engineering Practices in an Academic Environment

Many university degree programmes provide students with a solid grounding in the theoretical basis of computing, but it is difficult in a university environment to provide training in the types of software engineering techniques and practices, such as agile methods, that are commonly used in industrial development projects. There is typically a large gap between theoretical knowledge and practical experience.

In this session we will first present how we have developed a programme that aims to bridge this gap, providing students with practical experience of relevant skills for industrial software engineering careers. We will give examples from courses at both Imperial College and Oxford. We are aiming to create courses that are practical and industrially relevant, but built on the fundamentals of computer science and rigorous engineering.

Then we will introduce the technique of Reverse Instructional Design, and change to a workshop phase. We will draw on the expertise and experience in the room to discuss what are the most important things for students to learn before they start working in software development, and then try to design new possible course structures to address these.

We will also discuss applying agile techniques and systems thinking to the design of the educational experience itself.

Test Driven Specification – A Gentle Introduction to TLA+ (finding concurrency bugs before you write code)

This is an introduction to the Temporal Logic of Actions (TLA+), the system for specifying concurrent systems invented by Turing Award winner Leslie Lamport.

In this session I will demonstrate the use of TLA+ and TLC (the TLA+ model checker) to develop a specification for, and explore the properties of, a concurrent system.

I will show how an interactive test driven approach can be used both to learn TLA+, and to incrementally build a specification for a concurrent system.

You will see how the development of a specification can be guided in simple steps by tests, whilst the TLA+ tools expose flaws that violate requirements or cause the system to deadlock.

TLA+ and the TLA+ Tools, including TLC, are available from Microsoft Research under an MIT license.

The material developed in the tutorial will be available on GitHub.

The D Language, or The Art of Going Meta

By day, the D language is a mild-mannered language with an emphasis on efficiency and safety. By night, D dons a superhero cape and goes meta. Quite literally. D features compile-time introspection, compile-time evaluation, and compile-time code generation – see the pattern? D’s unique features combine into a powerful mix that enables new ways of designing programs.

This tutorial, conceived and taught by D architect Andrei Alexandrescu, is an introduction to the D language with an emphasis on its distinguishing metaprogramming facilities. Along the way, learn about Design by Introspection, the next level of generic programming.

The Distributed Version Control Revolution

The revolution is over; distributed version control has won.

But what makes a version control system "distributed" and why are such systems considered desirable?

In this session we take a look back through the history of version control and ways in which the essential features of version control have been provided.

We examine the assumptions and myths surrounding version control and how they have shaped products over time.

We also look at the features and innovations that have been developed over the history of version control, learning from some of the most influential products.

Finally, we make an attempt to determine what current "truths" about version control are actually myths and what might be holding us back from the next revolution in version control.

The Plural of Anecdote is not Test Suite

A test suite should constrain the behaviour of your program to be as close to correct as possible. The best test suites are a kind of executable specification of your code’s behaviour.

Most test suites are instead a series of anecdotes about this thing that happened that one time.

We try to fix this problem by adding more anecdotes, because we don’t have the tools to turn our test suites into full specifications.

In property-based testing we work in partnership with the computer: We write the tests but the computer supplies the examples to check them. So instead of writing about that thing that happened we get to specify what should happen for every example we’ve been provided.

So why don’t we do this? Property-based testing tools have existed for years, in the form of property-based testing libraries like QuickCheck. Instead of testing like it’s 1989, why don’t we test like it’s the year 2000? Or maybe even later?

Unfortunately, the tools to do so have been stuck in functional programming land - if you’re writing Haskell, Erlang, Scala, Clojure or one of a number of others, your life is great. If you’re like the rest of us, not so much. This is what Hypothesis and Conjecture aim to fix.

In this session we’ll explore property-based testing in mainstream languages – mostly Python through the medium of Hypothesis, but we’ll also look at it in other languages. This will be a mix of high level talk about the whys, some detailed walkthroughs of examples, and a whole bunch of live demos where you can put me on the spot and ask me to test things.

Beginner friendly, but intermediate and above will probably get more out of it. Some Python familiarity would be helpful, but there will be examples in a variety of languages (TBD, but most likely Python, Java and C++).

The Story of CyberDojo (so far) is an innovative, browser based, open-source, environment for practising programming, conceived, designed, and implemented by Jon Jagger. It had one of it’s first outings at the 2010 ACCU conference. It’s come a long way since then and has hosted over 30,000 practice sessions. In this talk I will recount the origins of cyber-dojo, describe the value system that influences it’s design, explain some early design decisions, reveal some of the hacks to make it work, recount some of the bugs that escaped testing, show how the design has evolved, present some statistics on most common languages, etc, etc.

Tough Stuff in Modern C++

Most new features in C++11/14 are simple and straightforward. This tutorial doesn’t deal with those features. Instead we examine the difficult, the strange, the frustrating. In detail. Expect to revel in reference collapsing, weirdness related to lambdas’ reaching scope and how different lambdas actually are from function objects, initializer_list idiosyncrasies, transparent function objects, variadic template details, and more.

Using Units, Qantities, and Dimensions in C++14

The zero-cost abstraction capabilities have the potential to make code computing physical properties much safer by incorporating not only a numerical value, but also its physical dimension into the type system. Instead of providing a comment, like, "this number represents a velocity in km per hour" one can define a variable of dimension velocity and provide units like "meter per second", "kilometer per hour", or "nautical knots" to convert numeric values into a velocity quantity.

Boost::Units as a library has been a long time around but didn’t get the appreciation it might deserve. However, its design is "ancient" and more modern C++ style is asked for. Martin Moene provides a C++11 compile-time units library based on previous design by Michael S. Kenniston. This talk will motivate using units, quantities and dimensions and provides a short C++14 DIY guideline and demonstrates the uses of Boost::Units and Martin Moene’s PhysUnits C++11 (or a slightly modernized C++14 version of it).

After this talk, you will stop using plain double or float for representing physical units and switch to use a units library. My plan is, to suggest standardizing a units library for a future ISO C++ standard, your help is appreciated.

Using the Groovy Ecosystem for Rapid Development on the JVM

There are many languages being born on the JVM. Some of them have become very popular in specific contexts and have grabbed the headlines. Apache Groovy, on the other hand, has silently made inroads into many areas of software development. It’s flexibility and ability to feature both dynamic and static typing makes it possible to combine with other JVM languages and tools and yet speed up development and readability. Some highlights of this session will include

  • Spock Framework for unit testing

  • Geb for Web UI testing

  • Ratpack for webservice development

  • Gradle, the build-deploy pipeline tool

There are a couple of pleasant surprises too, which will only revealed in the session. Beware many code snippets and demonsrations in this session.

Visualize Template Instantiations - Understand your Template Bugs

Many C++ beginners shy away from employing templates in their code, because of the myth of templates being hard. Even seasoned C++ developers can have problems manually interpreting template code correctly as Olve Maudal’s C++ pub quiz demonstrates. Overloads and template specializations make it hard for programmers and also IDEs to show a developer what happens without compiling a program and even with a compile one might not get, what actually happens unless an unintelligible error message from your compiler appears.

My students tried to alleviate that problem by visualizing template instantiation and overload selection in a C++ IDE and allow to navigate through template code in instantiation context that a compiler would only create internally and that is otherwise not available for humans. While still in its nascent state I hope to show what is possible and if things go as planned at the time of the submission you should be able to solve the template pub quiz questions without running the programs.

Templator (will be/is) part of (a future release) of [ Cevelop], expected in Winter 2015/16

WG21-SG14: The Story So Far

WG21-SG14 is, at time of writing, the newest study group to be convened by WG21 chairman Herb Sutter. The purpose of this study group is to standardise improving C++ for low latency, real time requirements and performance/efficiency, especially for games, finance/banking and simulations. The group was convened in June 2015 after several months of lively discussion on an unofficial google group.

Issues which concern the group are:

  • the cost of exceptions, which violate the don’t pay for what you don’t use rule

  • the absence of contiguous-implemented containers in the library such as boost::flat_map and boost::flat_set

  • the provision of unstable_remove algorithms and raw_storage iterators

Other issues are emerging as discussions unfold (when we stop going on about exceptions). Study group stakeholders are interested in writing performant and efficient code by default: at the moment, many developers have to roll their own containers, wrangle the compiler settings and deal with obscure minutiae more than seems necessary. This talk will present the history and work to-date of WG21-SG14. If you are working in games, finance or simulations, or you are writing performance sensitive code, this should be of interest to you. Attendees will take away a deeper understanding of exception implementation and costs among other performance issues, as well as an insight in to how study groups work, how they are run and organised, and why you might want to contribute to one.

Waltzing with Branches

The use of branches within a version control system is a risk management technique. They are commonly used to minimise the risk of unanticipated side-effects when releasing critical changes to production, or to minimise the disruption to developer productivity when making changes to the base product. But branching is not the only means of managing risk and that is what this talk addresses – the forces that drive the use of branches, what are their problems, and what are the alternatives.

Branching during the evolution of a software product, either its over-use or complete avoidance, is just as susceptible to the malaise of the "cargo cult" as many other areas of development. The choice is not always made based on an informed decision with a careful weighing up of the pros and cons and their alternatives, but purely by following what practices the "cool" companies are (seen to be) using.

What is often misunderstood is how the same risks that historically have been mitigated through the use of branches might now be handled via the use of other, non-version-control related practices to ensure stability and productivity remains high in the face of continued change. Whilst there is still a time and a place for the use of branches we will discover when that might be, but equally spend as much time exploring the complimentary practices that help us to avoid their pitfalls.

What Every C++ Programmer Should Know About Modern Compilers

Many C++ programmers (especially beginners) either underestimate or doesn’t actually know the power of modern C++ compilers. In the presentation author goes through all features that everyone should be aware of, discusses tooling ecosystem that grown around compilers, and finally covers topics like architecture or optimizations.

Without Warning: Keeping the Noise Down in Legacy Code Builds

As part of the process of taking the legacy out of a legacy code base, we want to remove all compiler warnings. However: a crude approach of merely switching them off helps no-one; we don’t necessarily have the time to actually fix the warnings (because to do that may break "working" code, and would thus require writing tests); and we want those warnings on and actionable for new code that we write. This short session will present a handful of tools and techniques for getting a quiet compile without losing the warnings we want or introducing changes in code behaviour.

Writing Libraries is Terrible

Libraries are great, right? You need to solve a problem, so you just find the library that solves it for you, download it, and use it. Problem solved.

This is a talk about everything that happened prior to that point.

Libraries look like they’re made out of code, but what they’re mostly made out of is the distilled suffering of their authors. Writing libraries is fun, right up until the point people start using them, at which point you suddenly discover the vast number of requirements that making a useful library puts on you.

I’ll go over some of these requirements that I had to find out the hard way. At the end I’ll briefly talk about a beautiful fantasy land I sometimes like to retreat to where things aren’t quite so terrible, but unfortunately we’re not going to get to live there for a while.

This talk will be a bit Python centric because that’s where most of my experience lies, but much of my pain will be universally shared by library authors of all languages.

Writing Snake in 6 Programming Languages

Andy Balaam shares his encounters with 6 programming languages by writing his favourite game in them: Snake.