Writing: Coping With Complexity

The January issue of ACCU's CVu magazine is landing on doormats now. It contains the latest instalment in my Becoming a Better Programmer column. This one's called Coping With Complexity. It an interesting wee treatise on managing (and fighting) complexity in our software.

It's got sticks. And blobs. And people.

I have to say, this month's issue is a bumper one - you never get a feel for this when reviewing the PDF galley proofs. Well done all involved.

Installing Groove Agent 3 (Update from Version 1) on Mac OS Lion

It all seemed so simple. I wanted to install my trusty copy of Groove Agent 3 on a new Mac OS Lion box. The license is on my eLicenser already. So it should just be a quick insert-DVD-and-install job.

Shouldn't it?

Of course not.


#Fail...

I've been using Groove Agent for years now. My version 3 DVD was an upgrade disk from the original version 1. If you run that DVD's installer it says you have to have version 1 installed to upgrade. That seems fair enough.

Except you can't install Version 1 on Lion; it is an old PPC application, and Lion doesn't support Rosetta any more.

It's a deadly circle; I now legitimately own some (not inexpensive) software that I can't install. Pete is not a happy bunny.


Attempt 1: tech support

I sent a tech support email through my Steinberg account. Not with much hope, I have to admit.

That was ages ago. What do you think happened?

Yup, you're right. Not even got a "we've got your message and it's in a queue" reply.

Thanks, Steinberg. Thanks a bunch.

But where there's a will, there's a way...


Attempt 2: Check for updates on the website

The Groove Agent 3 support site has a few update installers available (which, naturally, need the full program installed first to be able to update).

There is also a new "full installer" for the Mac to replace the DVD's installer for first-time users. This shows great promise.

Once downloaded, I run the installer. "Insert the Content DVD" it asks (impolitely). OK, again this is fair enough. The content is enormous, and is on the DVD already so I shouldn't need to download that again. It also proves that I own the product I'm installing.

I insert my Groove Agent 3 DVD into the machine. The installer doesn't recognise it. No message. No hint. No continue button. It just sits there.

Of course, it's looking for the "Groove Agent Installation DVD" not the "Groove Agent Update Installation DVD". Swines.

Absolute swines.

But where there's a will, there's a way...


Attempt 3: Trick the installer

Being a techie I wonder. I wonder how rubbish they really are... Is the installer just looking for a DVD called a certain name?

ln -s "/Volumes/Groove Agent Update DVD"  "/Volumes/Groove Agent DVD"

Run the installer again.

Success!!!

The installer runs, it copies over the content from the DVD and there's my Groove Agent 3 sitting there, ready to run.

Goodliffe: 1, Steinberg: 0, (Steinberg Customer Support: -5)


But, we're not there quite yet

I fire up Cubase, pull in the virtual instrument, and a window pops up asking me to locate the content files. That's the content that the installer just installed. Into a standard place. Didn't it think to look there itself? Sheesh.

That's OK, I'll just use the file browser dialogue that appears to load it. Except that the content is automatically installed into "/Library/Application Support/Steinberg/Groove Agent".

Notice that first bit. Yes, "/Library". The folder that Apple now HIDES from users in Lion so they can't fry in innards of their OS. I physically can't navigate to the content. Genius.

The trick, of course, is to launch Finder, open the "Go" menu, and hold down the Command key. At this point "Library" magically appears in the middle of the menu's list of places you can go to. Select that folder. Navigate to the right directory in the Finder window that appears, and then drag the target directory into the patiently waiting application's file open dialogue.

What a palaver.

But that's it, I now definitely have Groove Agent 3 installed and running.


Whinge

Of course, I have a clue what's going on inside my computer, and was able to engineer this solution based on my experience and a selection of educated guesses. Goodness only knows what the average user would be able to make of this situation.

(Hopefully this blog post will help someone in time. Let me know if it does!)


Endnote

It seems that every time I want to sit down an use my computer to make music, the computer wants some love, wants its nappy changed, or wants feeding first.

 New driver required! Update available! Incompatibility detected!

Technology really can get in the way of being creative.

Speaking: BCS Newcastle

I will be speaking at BCS Newcastle on the 25th January. I'll be giving my iOS development talk; a quick start in developing applications for iPhone, iPad, and iPod Touch.

Here's the synopsis:


The iPhone, iPad and their iOS relatives are becoming an increasingly popular and important platform. More and more developers are looking into what the platform can offer and how to harness its power for their products.


In this presentation, an experienced iOS developer provides a boot-strap in iPhone development. The talk is an overview of how to get started as an iPhone developer. You will gain an understanding of the platform, the tools, and the core technologies, including:

• The main languages: Objective C/C++
• Using the Xcode IDE, and various deployment/testing tools
• Common iPhone/Mac OS design patterns, idioms, and practices
• Becoming a native: how to “think in iPhone”
• An overview of the libraries and facilities that exist
• Limitations of the development environment.

We’ll see the pros and cons of iPhone development. You will leave with an understanding of how to deploy your applications on the device, and whether it is the right platform for you to target.

Speaking: ACCU 2012

I will be speaking at the ACCU 2012 conference in Oxford, UK this April.

I'm giving two presentations this year, both this year on version control:

• Version Control Done Right, and
• Getting into Git

Version control is never a laugh a minute topic, but I plan on these talks being interesting as well as informative. There will be the requisite amount of jumping, tomfoolery and general barefooted nonsense that regular attendees have come to expect.

This year's ACCU conference programme looks very strong, with understandable focus on C++ since the ink is still drying on the newest version of the language standard. But it still covers a broad range of topics, so there's something for everyone.

If you care about programming and live in proximity of Englandshire, I strongly suggest you check out this conference. It's one of the highlights of my programming year.

Skip Lists: A C++ STL-style implementation

Recently someone mentioned an interesting container type to me, the skip list. It piqued my interest and so, naturally, I wanted to play around with it. It's been a while since I last wrote an STL-style container, so I thought I'd attempt to write an STL-compatible skip list implementation. Fun times.

And so I present to you my latest code offering, the C++ STL-style skip_list container. Grab it from the GitHub project here. Or read on for further information...


Skipping the list

The skip list is an interesting data structure. You could (simplistically) consider it a hybrid of a std::list and a std::set; it's a list-like data structure than provides good insertion, removal and search performance. As ever, the trick to good search speed is to trade off some memory to improve traversal performance.

Traditionally the skip list is an extension of a standard forwards-only linked list. Wikipedia has a pretty good page on the structure. Check it out if you want more gory details.

Atop a standard linked it, it maintains a set of higher-order linked lists that act as indexes into the main structure below. These provide faster access to the middle of the list. This provides efficiency on a par with a balanced binary tree (i.e. what a std::set is usually implemented in terms of). Insertion, removal and search operations are typically O(log N). Remember: a standard linked list (which you'd have to manually keep in order) would have all those operations take O(N).

The particularly interesting detail about the skip list implementation is the algorithm used to determine the allocation of nodes to higher-order lists. Rather than use a fixed balancing scheme, or inspecting the data as it's added and comparing against the existing structure, we assign nodes to levels probabilistically - always adding them to the main list, and then (with decreasing levels of probability) adding them to the high levels lists, too.


My implementation

I chose to implement a bi-directional skip list, so each node in my version retains a back-pointer to the previous node. This makes the list more useful in general, and ensures that it's a drop-in replacement for std::list.

Like std::set, my version takes a template Comparison functor (typically std::less) so you can tailor the ordering of data in your container. I also, naturally, support custom allocators, and provide all "the usual" STL container operations.

I have tested the code on:

• Mac OS using Xcode 4.2
  
• Windows usigin Visual Studio 2008
  
• Linux using gcc 4.4

I have benchmarked the performance of my skip_list container. Because of the probabilistic nature of the container, sometimes it will perform better than other times when given random test data.

The memory consumption is almost exactly the same as std::set in general, and it tends to allow faster forwards and reverse iteration. Depending on the way the wind is blowing, large node insertion/removal operations can be dramatically faster (taking a little as 25% of the time of std::set for the same data) or a bit slower (I've seen up to ~110%).

The source archive contains my benchmarking code, so feel free to try it yourself.

The GitHub project for skip_list is https://github.com/petegoodliffe/skip_list.


Future plans

I have not yet provided C++11 "move" or initialiser_list operations, so that would be an interesting addition.

I could extend the data structure to provide O(log N) random access (e.g. indexing and random access iteration), too, at the expense of one more integer value in each node. That would be an interesting extension to consider - probably as a parallel variant of the existing container.


Future writings

If there's enough interest, I might start a new blog series on writing an STL-like container based on this implementation. There was a lot of interest in my previous series describing an STL-style circular buffer. Since this is a meatier data structure, the case study would be more useful.

Let me know if you'd like this!

PGMidi moved and updated

My popular PGMidi library for MIDI input/output on iOS has moved from Gitorious to a new location on GitHub. (This was requested many times, and who am I to disappoint?)

Please update your repos accordingly.

Over the next few days, I'll also be adding a few new tweaks and features to the project, so stay tuned.

Thanks for all the kind comments and feedback about the code - I'm really glad it's useful. Please do let me know if you've incorporated it in your own project.

Writing: How To Pick Your Programming Language

The November issue of ACCU's C Vu magazine is out now. It contains the latest instalment in my Becoming a Better Programmer column. This one's called How To Pick Your Programming Language.

It's a masterwork that uses ancient dark arts (and frivolous flow chart technology) to help you select the programming language that best suits you.

Best read with a pinch of salt!

I quite like the artwork I produced for this month's cover, and have finally remembered to align the {cvu} drop shadow correctly, something that's been bugging me for months. (I doubt anyone else would even have noticed it)