Month: October 2013

Who is a senior developer anyway?

On By David GreenIn Software development4 Comments

What makes you a “senior developer”? Everyone and their dog calls themselves a senior developer these days. From fresh graduates to the CTO, everyone is a senior developer. But what the hell does it even mean?

Technologists

Some developers are avid technologists. They got into programming really because they like tinkering. If it hadn’t been 7 languages in 7 weeks, it would have been a box of meccano or they’d be in their shed busy inventing the battery operated self-tieing tie. These people are great to have on your team, they’ll be the ones continually bombarding you with the latest and greatest shiny. If you ever want to know if there’s an off the shelf solution to your problem, they’ll know the options, have tried two of them, and currently have a modified version of a third running on their raspberry pi.

The trouble with technologists is more technology is always the answer. Why have a HTTP listener when you can have a full stack application server? Why use plain old TCP when you can introduce an asynchronous messaging backbone? Why bother trying to deliver software when there’s all these toys to play with!

Toolsmiths

Some developers naturally gravitate towards providing tools for the rest of the developers on the team. Not for them the humdrum world of building some boring commercial website, instead they’ll build a massively flexible website creation framework that through the magic of code generation will immediately fill source control with a gazillion lines of unmaintainable garbage. Of course, that’s assuming it works, or that they even finish it – which is never guaranteed.

There’s a certain kudos to being the tools guy on the team: you don’t want the most junior member of the team creating tools that everyone else uses. If he screws up, his screw up will be amplified by the size of the team. Instead one of the smart developers will see a problem and start sharpening his tools; the trouble is you can spend an awful long time creating really sharp shears and somehow never get round to shaving the yak.

Backend Boys (and Girls)

Another common pull for a lot of developers is to get further down the stack, away from those messy, annoying users and nearer to the data. Here you can make problems more pure, really express your true artistry as a developer and an architect. It’s true: as you move down the stack you tend to find the real architectural meat of a system, where you want the developers who can see the big picture of how everything interacts. The seasoned professionals that understand scalability, availability and job-security.

It’s pretty easy to put off outsiders (project managers, customers, sniveling little front end developers) – you start drawing diagrams with lots of boxes and talk of enterprise grade messaging middleware and HATEOAS service infrastructure, before you know it their eyes have glazed over and they’ve forgotten what they were going to ask you: like perhaps why this has taken six months to build instead of six days?

GTD

Some developers just Get Things Done. Sure their methods might be a little… slapdash. But when you’re in a crunch (when aren’t you?) and you need something done yesterday, these are the people you want on your team. They won’t waste time designing a big complex architecture; they won’t even waste time writing automated tests. They’ll just hammer out some code and boom! problem solved.

Sometimes they can come across as heroes: they love nothing better than wading into a tough battle to show how fast they can turn things around. Of course, that also lets them quickly move from battlefield to battlefield, leaving others to clean up the dead and wounded they’ve left behind.

Front End Developers

For some reason Front End developers never seem to be considered the most senior. As though hacking WPF or HTML/CSS was somehow less worthy. In fact, I think the front end is the most important part – it’s where all your wonderful n-tier architecture and multiple redundant geegaws finally meets users. And without users, everything else is just intellectual masturbation.

The front end developers are responsible for the user experience. If they make a mess, the product looks like crap, works like crap: it’s crap. But if the front end developers create a compelling, easy to use application – it’s the great, scalable architecture underneath that made it all possible. Obviously.

Team Lead

Your team lead probably isn’t a senior developer. Sorry, bro: if you’re not coding you can’t call yourself anything developer. Go easy on your team lead though: the poor sod probably wrote code once. He probably enjoyed it, too. Then some suit decided that because he was good at one job, he should stop doing that and instead spend his life in meetings, explaining to people in suits why the product he’s not writing code for is late.

Architect

Your architect probably isn’t a senior developer either. Unless he’s actually writing code. In which case, why does he need the label “architect”? Architecture is a team responsibility. Sure, the most senior guy on the team is likely to have loads of experience and opinions to share with the team – but it doesn’t mean his pronouncements should be followed like scripture. But if instead of writing code you spend your time drawing pretty pictures of your scalable messaging middleware one more time, I will shove it up your enterprise service bus.

Conclusion

There are lots of different types of senior developer. That’s probably why the term has got so devalued. Once you’ve been in the industry for a few years, you’ll have found yourself in at least one of these roles and can immediately call yourself senior. The truth is you spend your whole life learning, only in an industry this young and naive could someone with 3 years experience be called “senior”. I’ve been programming professionally for 13 years and I’m only just starting to think I’m getting my head around it. I’m sure next year I’ll realise I’m an idiot and there’s a whole new level to learn.

So, go ahead, call yourself senior developer. Just make sure you keep on learning. Change jobs, wear a different hat. Be the tools guy. Meet like-minded developers. Play with different technologies. Become a middle tier developer. Then switch to work on user experience.

Senior developer: it’s just a job title, after all.

Matlab Performance Testing

On By David GreenIn Software developmentLeave a comment

Where I work we have an unusual split: although the developers use C#, we also work with engineers who use Matlab. This allows the engineers to work in a simple, mathematics friendly environment where working with volumes of data in matrices is normal. Whereas the developers work with real computer code in a proper language. We get to look after all the data lifting, creating a compelling user interface and all the requisite plumbing. Overall it creates a good split. Algorithms are better developed in a language that makes it easy to prototype and express complex algorithms; while dealing with databases, networks and users is best done in a proper object oriented language with support for a compile time checked type system.

As part of a recent project for the first time we had a lot of data flowing through Matlab. This led to us have to verify that our matlab code, and our integration with it from C#, was going to perform in a reasonable time. Once we had a basic working integrated system, we began performance testing. The initial results weren’t great: we were feeding the system with data at something approximating a realistic rate (call it 100 blocks/second). But the code wasn’t executing fast enough, we were falling behind at a rate of about 3 blocks/second. This was all getting buffered in memory, so it was manageable but creates a memory impact over time.

So we began scaling back the load: we tried putting 10 blocks/second through. But the strangest thing: now we were only averaging 9.5 blocks/second being processed. WTF? So we scaled back further, 1 block/second. Now we were only processing 0.9 blocks / second. What in the hell was going on?

MatlabPerf

Let’s plot time to process batches of each of the three sizes we tried (blue line), and a “typical” estimate based on linear scaling (orange line). I.e. normally you expect twice the data to take twice as long to process. But what we were seeing was nearly constant time processing. As we increased the amount of data, the time to process it didn’t seem to change?!

We checked and double checked. This was a hand-rolled performance test framework (always a bad idea, but due to some technical limitations it was a necessary compromise). We unpicked everything. It had to be a problem in our code. It had to be a problem in our measurements. There was no way this could be realistic – you can’t put 1% of the load through a piece of code and it perform at, basically, 1% of the speed. What were we missing?

Then the engineers spotted a performance tweak to optimise how memory is allocated in Matlab, which massively speeded things up. Suddenly it all started to become clear: what we were seeing was genuine, the more data we passed into Matlab, the faster it processed each item. The elapsed time to process one block of data was nearly the same as the elapsed time to process 100 blocks of data.

Partly this is because the cost of the transition into Matlab from C# isn’t cheap, these “fixed costs” don’t change depending whether you have a batch size of 1 or 100. We reckon that accounted for no more than 300ms of every 1 second of processing. But what about the rest? It seems that because of the way Matlab is designed to work on matrices of data: the elapsed time to process one matrix is roughly the same, regardless of size. No doubt this is due to Matlab’s ability to use multiple cores to process in parallel and other such jiggery pokery. But the conclusion, for me, was incredibly counter intuitive: the runtime performance of matlab code does not appreciably vary based on the size of the data set!

Then the really counter intuitive conclusion: if we can process 100 blocks of data in 500ms (twice as fast as we expect them to arrive), we could instead buffer and wait and process 1000 blocks of data in 550ms. To maximize our throughput, it actually makes sense to buffer more data so that each call processes more data. I’ve never worked with code where you could increase throughput by waiting.

Matlab: it’s weird stuff.