Ivan and Sam’s New Year Party (by sarah)

For this New Year we headed down to my cousins house for a party, as always we got lost on the very last bit of the journey and Ivan had to come out and find us - I was navigating but the map didn't go down to a fine enough detial ok!

There was lots of food and lots of kids! Jean had a great time as there was basically a room full of children throwing balls and things at each other and there was a mirade of pepper pig videos and the like. Ivan and Sam also have a fish tank 🙂 Jean loves fish we take to the garden centres locally just to look at 'Nemo's' (Becca and Olly have a lot to answer for!).

At mid night there was the the popping of party poppers and as always I ended up with a wig of the paper strings - this time Jean put it on my head 🙂 We all had an attempt at Auld Langs ey and by the end Jean was the only on of the 'babies' still running about full of energy but then she had had a nice long sleep all the way from Gloucestershire to Essex!

Jean was shy at first but cheered up when we changed her into her satin pink party dress - all the other kiddies were dressed up and she felt abit out of place I think - she had her sparkly silver shoes and all would have been well if she hadn't tried to walk away from me whilst I was trying to tie the bow around the waste - I stepped after her and trod on the belt and she kept going and there was an ominous ripping noise and so she ended up with her belt ribbon tied as a braclet around her wrist instead.

'Mummy you broke my dress!'

'Yes well if you won't keep still when I say things like that will happen.'

It was a good party and we even got warm mugs of tea as we stayed to help tidy up - they offered for us to stay the night but Al wanted to get back to Highgate.

(hopefully at some point I'll get the photos on here:/)

Happy New Year 2009 (by sarah)

This year sees lots of exciting things - its the International Year of Astronomy and so I have set up a specific Astronomy blog - the spellings all need sorting and alot of the stuff on there is from things I've written up on here.

I know its another blog but other wise I have too much to go on here and its nice to have a specific theme and things. Plus I now have a specific career goal which is to be a popular science writer - I want to bring science to the front, so kids find it interesting, explain it to the lay person etc...

I want to rekindle the flame that the victorians lit - a flame that is in the danger of blowing out leaving our culture with just recipies for current technology but no inovation or advancement.

I wanted to do alot of Astronomy stuff last year but with everything that happened it just got swept aside 🙁

Other goals for this year are to carry on with the Prince's Trust and MRes both of which are giving me valuable skills. Get Web-Empire fully up and running but more on that later 🙂 Enter the Young Science Writer of the Year compatition and just generally get our lives back on track.

Jeany will also be starting school in September! She'll be the youngest in her year - I feel this will be a good thing.

I hope you all have good New Years and lets hope this one will be better than the last!

Backup system progress (by alaric)

I mentioned an intent to build a backup system this Christmas. Well, I've not had two days to work on it yet; I've just had an hour and a half one evening, in which I've written the local-filesystem backend...

But last night I had a dream about it. In particular, I dreampt of visiting an old friend I've neglected to keep in touch with lately; and at her house she had a rather snazzy little mini-laptop, like an EeePC or something, which had an eSATA connector into which she plugged some humungous (in terms of gibibytes; it was the size of a double CD case, physically) external hard disk upon which she had a filesystem that seemed to work very much like Fossil/Venti, the original inspiration for my backup system - or perhaps like a giant personal Git repository.

In particular, one feature that cropped up in the dream was that the filesystem had a magic file on it which was an RSS feed of recent changes to files.

Which got me thinking about features for version 2 of my backup system (if I get to finish version 1, that is!). My focus is on offline use, for batched backups, but the filesystem in my dream was being used online.

For a start, we could have a log of changes to tags, as in my system tags are the "roots" of the archive system. The creation of new tags, the deletion of tags, or the updating of a tag to point to a new snapshot would all be logged. This could then be used to create the RSS feed.

Secondly, it shouldn't be too hard to write a FUSE interface to the thing for read-only access, presenting a root directory containing an RSS file generated from the log, along with a directory for each tag, which in turn contains a current subdirectory containing the current value of the tag as well as dated subdirectories containing all the past contents of the tag, in ISO date format so they sort correctly. And perhaps an RSS file just listing the history of that tag.

But then the next cool thing would be to allow write access, by using a local disk directory as a staging area, so the current subdirectory can be written to (with the changes being spooled to the local disk). Then when a commit command is given, those changes are merged into current. Which would require a new underlying operation to merge changes in, rather than taking a new snapshot; the difference being that any files or directories missing in the directory tree being snapshotted are 'inherited' from a previous snapshot already in the system, with some mechanism to reflect deletions.

Anyway, unrelated to the dream, it also occurred to me that it'll be neat to support replicated archives; my implementation of the backend architecture will make it easy to take a set of backend instances and merge them into one, with every write going to all of them and reads serviced from the first one that succeeds. It'll also be easy to support staged archives, where a number of read-only backends are checked for existing blocks, but all new blocks go to a nominated writable backend, with another backend adapter. That will allow for generational backup systems, where a local disk is filled up with backups until it reaches a size limit, whereupon its contents are shipped off to a DVD writer (keeping a local cache of what blocks where on there, so the DVD need not be put in unless the contents of blocks are actually needed).

But, all idle speculation for now. I still need another day and three quarters to implement the core of the thing...

Design patterns (by alaric)

I'd thought I'd had this little rant before, but as I went to find the post I'd had it in to link to it from a big ranty post I'm working on, I couldn't find it.

So here it is.

My opinion of design patterns.

Design patterns are common structures that appear in computer programs, but that can't themselves be abstracted into a reusable component.

That's fair enough. I have the "gang of four" book of design patterns, that started the craze, and I think they're all good design patterns in mainstream OO languages; things that can't be actually encapsulated as a class or whatever, but that keep cropping up.

However, the problem is that the patterns community has somehow ended up with some dogmatic folks in it. Who take phrases such as "Design patterns are common structures that appear in computer programs, but that can't themselves be abstracted into a reusable component" - and then attack anybody who claims to have encapsulated a design pattern into a reusable component.

Because design patterns are really only valid in relation to a set of languages. For example, in assembly language (or even traditional BASIC with GOSUB), procedure calls are a design pattern. There is no language construct for a procedure; instead, you have a GOSUB or CALL to a given address, that explicitly saves the calling location somewhere and then jumps, and a RETURN to go back to that saved location. The GOSUB...RETURN pairing is put in there by the programmer; it's a design pattern.

But then higher-level languages have explicit procedure abstractions, and all the fun they entail.

Even object orientation is a design pattern in languages like C. "Put function pointers in a struct, and call them with the struct pointer passed as the first argument". Or including a pointer to a struct of function pointers in every data struct (and call it a virtual method table). But go to Java and that's an explicit language abstraction facility.

The gang-of-four book is taken as the authoritative book of common design patterns (although it is, in my opinion, a book of design patterns for mainstream OO languages). And design patterns are things that cannot be expressed as native abstractions in code. THEREFORE, fools think, it's impossible to write a design pattern in code. And anybody who claims to have done so needs shouting at.

Sadly, as demonstrated in Peter Norvig's presentation on design patterns in dynamic languages, more advanced languages can express abstractions that others can't, and there are plenty of more advanced languages than C++ and Java.

In fact, I think that the appearance of design patterns in a language is probably a hint that the language needs to be more powerful - and suggests how to make it so. What sort of abstraction would make it possible to encode your design patterns?

And so, as I read "Modern C++ Design" by Andrei Alexandrescu (a book on doing good things with C++ templates), I come across the following phrase:

Eventually, Andrei turned his attention to the development of template-based implementations of popular language idioms and design patterns, especially the GoF [gang of four] patterns. This led to a brief skirmish within the Patterns community, because one of their fundamental tenets is that patterns cannot be represented in code. Once it became clear that Andrei was automating the generation of pattern implementations rather than trying to encode patterns themselves, the objection was removed...

Bleargh. It sucks when people get all religious about the interpretation of a given piece of "scripture". Even when people manage to work around it by using illogical arguments ("No, no, it's not a representation of the pattern in code, it's a bit of code that automates the creation of implementations of the pattern..."). Sadly, in other realms, this kind of thing can lead to people being burnt at the stake.

Sump plug woes (by alaric)

It's time I changed the oil (and the oil filter) in the van, since it's been over a year now.

So I bought myself some new oil, and a new oil filter, and prepared to do the deed according to the instructions in my Haynes manual.

The first step is removing the plug in the bottom of the oil sump, that lets the oil out. It looks like this:

Naturally, when you remove it, lots of hot oil comes running out (you do this with the engine warm so the oil flows well). So you do it with a bucket underneath!

However, I've not gotten as far as that step yet, because the head of the sump plug (which is hexagonal, like a bolt) is rounded. You can see in the pictures how the corners of the hexagon have all come off. They're shiny where I've been trying to grab them with a spanner, which just rotates when I apply enough force... and it doesn't take very much force.

So I went out and bought a special thing for undoing damaged nuts and bolts. It'll make a mess of the sump plug, so I bought a new sump plug, too. The magical nut remover looks like this:

The spiral grooves inside are rifled so that when you put it onto a nut and turn it (such as with the big adjustable spanner in the background), the points grip into the metal of the nut, and the spiral pulls the socket onto the nut as it twists it out, so that it can't push the socket off. Most stripped nuts and bolt heads are rounded towards the top, so tend to push spanners and sockets off as they are twisted; this thing pulls itself onto the nut with the spiral shape, thus counteracting this.

However, my sump plug bolt head is already far enough gone that the special socket rotates on it (shaving off little curls of shiny metal as it goes) when I turn it, again with surprisingly little force - but the next size of socket down doesn't fit onto it...

Perhaps the sump plug was made out of lead or aluminium or something?!?

I guess the next thing to try would be getting under there with a file and shrinking the head down to the next size by putting new flats on it.

But, since it's freezing outside and I've nowhere inside to work on the van, and we need the van ready to do a long drive in a couple of days (which I'd rather not do with the current black oil in, in this punishing weather), I think I'm going to take it to a garage and ask them to sort it out for me... I can give them the oil, the oil filter and the replacement sump plug I've already bought and just ask them to do the hard part!