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Showing posts from April, 2011

This Blog Has Moved!

Right, so yes, five years ago I moved to github pages, and never bothered to redirect any of these pages there. Now I've moved on from there, and... Finally I am using my real domain, trishagee.com . My blog is now at trishagee.com/blog .  See you there!
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Cyclist tribes

Living and working in central London, you quickly learn that the fastest way around town is to cycle. My extensive research into this activity has shown there are a number of different cycling tribes. Of course, I have split them into the two groups that are most appropriate to me: 1) slower than me and 2) faster than me. You can probably tell what sort of a cyclist I am by my attitude to the two groups. 1. Slower than me: Wicker shopping basket. Doesn't matter what the rest of the bike looks like, or the biker, I will always try to get ahead of these.  The extra scary ones are the women in flowing dresses who might be university professors. Boris Bikes .  When there's a tube strike, Avoid At All Costs.  These people probably haven't been on a bike since they were in school, and it shows. Hoody (always a male) on a BMX-style bike with the seat far too low, riding in too low a gear, with baggy jeans that show their... well... everything. Never have lights on th...
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TradeTech 2011 - Not like a developer conference

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I attended TradeTech last week, an annual event about Equities and Derivatives trading. I assumed from the title that there would be a reasonable focus on technology, but I found it was more “Trade” and less “Tech”. The fascinating thing to me was how different this is from the sorts of technology conferences I've been to. For example, I popped into JAX this week (albeit in the evening for drinks). At technology conferences (<gross-generalisation>) people tend to subscribe to a variety of dress codes and fashion clans, usually from jeans through the range of business casual, including your fair share of goths and alternatives. Suits would be unusual (</gross-generalisation>). At this place, people were scarily conformist. A few years back, the suits at least would be different colours – navy, greys and black – and may or may not include pin stripes. On Thuresday, almost everyone was wearing a particular shade of tasteful dark grey. I was also pretty shocked ...
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CSS for Developers: Horizontal and Vertical Centring

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First, an apology.  I will be using the British spelling for "centre", because, well, I'm British.  But it gets really confusing because you have to use the American spelling in the code.  And doesn't "Centring" just look wrong? Part Five: Horizontal and Vertical Centring One of the most common things you want to do with blocks of content is to centre it.  In particular, you would think that vertically centring content would be straightforward, but it turns out that in HTML/CSS it just isn't. 5.1 Horizontal Centring Centring a paragraph of text is clearly easy - all you need is text-align: center .  However, sometimes you want to centre a block, something like a div, without having all the text centred as well.  This is slightly trickier than you might expect, because the only CSS attributes you have are for centring text. <html> <head> <title>Horizontal Centering</title> <style type="text/css"> ...
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How to show your employees how much you hate them

Due to a combination of my restlessness, my consulting experience, and employers that insist on moving offices frequently, I've had the dubious honour of working in a variety of environments. Today I will teach you, the employer, how to show your staff just how much you hate them. The Kitchen Is Not For Eating In Since eating and drinking is unfortunately a fundamental part of being human and staying alive, you will need to provide your staff with a space that pretends to address these needs. The best example I have seen so far has been a "kitchen" with: no sink; no kettle; no microwave; a tiny under-counter fridge for employee food (for approx 50 employees); nowhere to sit and a maximum capacity of 3 people standing. You're probably wondering how I knew it was a kitchen.  Well, it had a counter top. And a coffee machine which also dispensed slightly warmed water.  And The Largest Drinking Water Dispenser In The World 1 . The most important thing to remember...
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Popular posts from this blog

Dissecting the Disruptor: What's so special about a ring buffer?

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Recently we open sourced the LMAX Disruptor , the key to what makes our exchange so fast.  Why did we open source it?  Well, we've realised that conventional wisdom around high performance programming is... a bit wrong. We've come up with a better, faster way to share data between threads, and it would be selfish not to share it with the world.  Plus it makes us look dead clever. On the site you can download a technical article explaining what the Disruptor is and why it's so clever and fast.  I even get a writing credit on it, which is gratifying when all I really did is insert commas and re-phrase sentences I didn't understand. However I find the whole thing a bit much to digest all at once, so I'm going to explain it in smaller pieces, as suits my  NADD audience. First up - the ring buffer.  Initially I was under the impression the Disruptor was just the ring buffer.  But I've come to realise that while this data structure is at the hea...
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Dissecting the Disruptor: Writing to the ring buffer

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This is the missing piece in the end-to-end view of the Disruptor.  Brace yourselves, it's quite long.  But I decided to keep it in a single blog so you could have the context in one place. The important areas are: not wrapping the ring; informing the consumers; batching for producers; and how multiple producers work. ProducerBarriers The Disruptor code has interfaces and helper classes for the Consumer s, but there's no interface for your producer, the thing that writes to the ring buffer.  That's because nothing else needs to access your producer, only you need to know about it.  However, like the consuming side, a ProducerBarrier is created by the ring buffer and your producer will use this to write to it. Writing to the ring buffer involves a two-phase commit.  First, your producer has to claim the next slot on the buffer.  Then, when the producer has finished writing to the slot, it will call commit on the ProducerBarrier . So let's look at...
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Dissecting the Disruptor: How do I read from the ring buffer?

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The next in the series of understanding the Disruptor pattern developed at LMAX . After the last post we all understand ring buffers and how awesome they are.  Unfortunately for you, I have not said anything about how to actually populate them or read from them when you're using the Disruptor. ConsumerBarriers and Consumers I'm going to approach this slightly backwards, because it's probably easier to understand in the long run.  Assuming that some magic has populated it: how do you read something from the ring buffer? (OK, I'm starting to regret using Paint/ Gimp .  Although it's an excellent excuse to purchase a graphics tablet if I do continue down this road.  Also UML gurus are probably cursing my name right now.) Your Consumer is the thread that wants to get something off the buffer.  It has access to a ConsumerBarrier , which is created by the RingBuffer and interacts with it on behalf of the Consumer .  While the ring buffer obviously n...
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