Advogato blog for hypatia

2008 Federal Budget: Laptops

Thu, 15 May 2008 03:05:05 GMT

The one single non-standard tax 'thing' that many people I know do is to salary sacrifice for a new laptop. Quick review of how this works: normally, you are discouraged from buying yourself stuff out of pre-tax income, because otherwise a sensible financial strategy would go something like: pay for everything, declare small remainder to government, be taxed only on small remainder. The way the government puts a stop to this is by charging Fringe Benefits Tax on things bought from pre-tax income. FBT is a huge amount of money, you'll pay an insane amount of tax on fringe benefits: better to buy things from your wages after tax was taken out.

There are a few exceptions or partial exceptions to FBT, and one is laptops, at present, more info here (written from an employer's point of view). Given how many people I know get their employer to let them salary sacrifice for their 'yearly laptop', I am surprised to see less commentary on this aspect of the Federal Budget for 2008/2009:

FBT improves tax fairness by taxing non-cash remuneration. Tax planning arrangements and changes in technology have eroded the fairness and integrity of the FBT system, which will be addressed by:

...

removing the FBT exemption for work-related items used mainly for private purposes such as laptops

removing the double benefit from employee depreciation deductions on FBT exempt items used mainly for work purposes

Budget Overview 2008–2009 [706K], page 5

What does this mean for you? I am not a tax professional (or financial professional) but my interpretation is:

if you are buying yourself a new laptop and it won't be used mostly for work, you buy it out of post-tax income from now on (and you don't claim depreciation on it either, you've never been allowed to depreciate private possessions like that anyway); or
if you are buying yourself a new laptop and it will be used mostly for work, you can either buy it out of pre-tax income, or you can claim depreciation, but not both as you may have done previously.

I assume this applies from July 1 2008 on.

Safe diving practices

Wed, 30 Apr 2008 05:04:56 GMT

Background: I had mild to moderate shoulder pain after SCUBA diving a month ago. I was treated for Decompression Sickness (DCS, the bends) although it's impossible to confirm the diagnosis for moderate pain, because it feels exactly like a sprain or strain.

I just had my followup appointment about safe diving practices (there's an Australian standard, in fact). Since these are enormously different to diving practices pretty much anywhere, I thought they'd be of interest. These are the ones they wish they could give to everyone, by the way, not the ones that are only for people who have had DCS. Take the ones that are actually taught in training — slow ascents, safety stops — plus:

dive the DCIEM tables with a square profile assumption (no multi-level, no computer algorithms);
never do more than 2 dives in a day;
never dive more than 4 days in a row; and
the fact that everyone do repeated dives on the President Coolidge and in the Truk Lagoon to 50 or 60 metres breathing air and without decompression stops doesn't mean that everyone isn't an idiot.

OK, that last one comes up in dive training too I admit. But only in the context of your instructor sheepishly admitting to their idiotic profiles. (The relevance of breathing air at 60 metres is that's a lot of nitrogen, over 5 atmospheres of partial pressure, and nitrogen not only gives you DCS, it makes you rather drunk starting from about 25 metres and steadily getting worse from there.)

In my case there is one extra restriction: take a 3 metre depth penalty and a 3 minute time penalty reading the table. Which is pretty conservative. For reference, I could dive to 27 metres for a grand total of 11 minutes bottom time on that reading of the table. (30 metres for 14 minutes is the standard reading.) Unless I decompress of course, but that has its own risks (equipment failures mean I'm stuck with failed equipment AND a missed compulsory decompression stop). The reason for the penalty is that the scar tissue from the DCS injury to my shoulder (actually, we suspect two, plus the damage from subluxating it six times previously) renders me somewhat more vulnerable again.

For non-divers, to contrast this with diving as it is actually done by pretty much everyone ever, imagine that you are going to a dance party, but need to tell the organisers that for medical reasons you'd really appreciate it if they'd keep the music no louder than 40dB. Cheers, thanks.

Or, to make this about diving, imagine that you are on a dive boat travelling to some great dive site several hours from shore. Your air consumption isn't amazing, you can't keep up with the suntanned French couple or the hoary old guys who are coming back after 60 minutes with half a tank left and cursing their computer time limits. But the guy running the boat who has done 1500 dives and your group's friendly English backpacker dive guide have come up with a plan for your group that gives you 35 minutes of good solid diving to see all kinds of cool things. Now imagine I'm in your dive group. I'm the one whose medical advice is to do a 18 minute dive at the absolute maximum (the clock stops at the beginning of the ascent by the way, so probably about 24 minutes in the water total). The upside of this last scenario, I suppose, is that firstly my air consumption is rather good, so I can always loan the group my tank, and also that because I'm doing 2 dives a day and most liveaboards allow 4 at the very least, it won't happen every dive because I'll be on the boat sulking for most of them.

Or, let's face it, never doing liveaboard trips again.

For divers the obvious question is what about nitrox? (For non-divers still reading, nitrox or enriched air is a tank with less nitrogen and more oxygen than the standard atmospheric ratio.) Well, it doesn't thrill the dive doctors. They agree that it is much safer on air tables. They don't so much like the use of separate tables to extend your dive time which, let's face it, is why I'd want to use nitrox. It also comes with separate risks: the mix can vary wildly from what they claim it is, and you have one more factor to manage, which is oxygen toxicity. (High partial pressures of oxygen are toxic to cells. The first you know of the cell damage is a sudden seizure. So the solution is not to breathe those partial pressures, from about 1.4–1.6 atmospheres up. You shouldn't go much past 20 metres on 36% oxygen.)

There's nothing to stop me learning technical diving (adding helium to the mix to offset the risks of high pressures of nitrogen and oxygen) or adding decompression stops to my time, except that no dive boat I've ever been on is set up for the latter. (And they're both complex.) The Pacific is choppy: you can't really stay at 5.5 metres easily for 5 minutes without a good reference line. And the boats move all the time without warning, taking their good reference line with them.

Tax calculator for PAYG employees

Mon, 28 Apr 2008 06:05:19 GMT

Since I am only of the very few Australian residents I know who haven't had an employer stuff up their tax withholding, a useful link: the ATO tax withheld calculator for PAYG employees.

It's in the 'for employers' part of the ATO site, but employees can use this to check whether each pay packet they receive has had the correct amount of tax taken out. It doesn't rule out the possibility of tax refunds or debts because it doesn't take into account a mountain of stuff, the major one being non-employment income but also private health insurance stuff, deductions, blah blah. But it does mean you can catch the most common payroll mistakes, the big one being an employer forgetting to take out a HELP payment. If a payroll mistake results in you having a tax debt, you're just as liable for it as in any other circumstances (assuming that the extra money turned up in your pay, which is what a mistake usually means) so unfortunately it is a good idea to double check that your after-tax amounts match the tax table whenever you get a new job or a pay rise.

Lucky I don't have to take the Driver Qualification Test

Thu, 24 Apr 2008 10:09:32 GMT

In a couple of weeks Andrew will make his first and I hope only attempt at the NSW Driver Qualification Test, the computer exam that separates provisional drivers from fully licenced drivers. (Here's the NSW car licence pathway.) And may I say that it's a good thing that I got a full licence back when there was only one test (I did the on-road driving test in 1998, held what is now the P1 licence for twelve months and then just got handed the full licence when it expired) because although it did take me four attempts to pass the on-road test that's nothing on what it would take to get me through the DQT.

Why? Well, the problem would be that the DQT asks a lot of questions based on the test handbook, and I wouldn't be able to read the test handbook without smashing a wall down. With my teeth.

Let's have a look. First we have some dodgy handwaving in which the authors of the handbook are astonished that 90% of their data fits into only five categories:

About 90 per cent of all crashes in NSW involving full licence drivers in their first year fall within only five crash types...

What's that only doing there, huh? How many crash types are there? Six? Three hundred and twelve? For reference the five crash common types are: rear-ending someone, colliding with a vehicle travelling perpendicular to you (at an intersection), colliding with a vehicle coming from the opposite direction, running off a straight section of road and running off a bend. That does seem to cover a lot of possibilities doesn't it? Don't divide your population into five obvious segments plus a catch-all and then act all surprised that most of the population ends up in the five categories.

But the much more annoying problem is this. They note that 25% of provisional driver accidents are rear-enders, 34% of first year full licence accidents are rear-enders and 40% of experienced full licence accidents ('experienced' is drivers in the fifth and all subsequent years) are rear-enders. From these numbers they draw this conclusion:

Researchers think that these differences are due to novice drivers getting better at staying on the road but also getting into the habit of driving too close behind other vehicles in traffic. This bad habit seems to continue for full licence holders. As you can see from [a colourful pie chart], full licence drivers with more than five years’ experience have even more rear end crashes. However, they are much less likely to run off the road and hit an object.

Uh-huh. And what an interesting conclusion that would be, if they had first established that they were all having the same number of accidents. If they've done this, they do not indicate it, it's all percentages of crashes within each population. ('The same number of accidents' is a little hard to define, but I believe it's usually number of accidents per driver, number of accidents per driven kilometre, or number of accidents per passenger kilometre. For various reasons, mostly because of a subsequent section about how women have less accidents partly because they drive about half the kilometres men do — half! — I think this booklet is measuring on a per driver basis.) If they're not, the higher proportion of rear-end accidents among experienced drivers doesn't suggest that they're risk-taking: only a higher absolute number of accidents does that. It could be, for example, that rear-end accidents are harder for even experienced drivers to avoid, and thus rise as a proportion of their total accidents just because they don't drop as much.

In fact, we certainly hope that the same-number-of-accidents premise is false here, because the whole point of the insanely complicated and steadily getting worse NSW licencing system (in which learner drivers now must log one hundred and twenty supervised driving hours before taking the on road test, ie, about twenty minutes every single day for a year) is to reduce the number of accidents among novice solo drivers by making them less novice (and also older and less prone to risk-taking, although NSW hasn't made this as obvious as in, say, Queensland where novice drivers over 24 get to skip a significant part of the pathway).

So far so good. That brings us to page 12 of the 94 page Driver qualification handbook. I think it's fairly clear that I'd struggle to get through it. Especially since I can't argue with a computer examiner.

My X pain

Wed, 23 Apr 2008 00:05:21 GMT

Since it's very unlikely that I will see an improved X.org a for me in Ubuntu Hardy (only showstopper bugs will be fixed now that the CD images are building and in any case, 4 days seems like an unreasonable timeframe) and Bryce Harrington wrote about filing good X bugs the other day, I thought I'd make some notes on why mine is a pain. Note that Harrington's timing is good, but he's not talking directly to me. And none of this will be surprising to people who regularly work with bugs. There's often one that can only be triggered on a rainy night after moon rise by a user with malaria, and you only have this one guy saying it happens all the time for him and completely and uselessly fails to mention that he lives near a swamp in a tropical country, and besides he can't see moon rise through the clouds. Plus, the fevers confuse him.

It's not very good form to blog about a bug without reporting it, but this one does not meet my 'reportable' threshold, which is that if someone says does blah fix it? I need to be able to answer in a fashion other than I have no idea.

The form that my bug takes is similar to bug 194214 except that it does not prevent me from using Ctrl+Alt+Backspace to restart X. My system will get into a state where various things happen on some desktops and different things on others (sometimes or perhaps always actually in different windows, since I run them maximised it's difficult to tell). On one, often the Shift key will be always pressed and the mouse not usable. On another, clicks on the window that appears to be in front will actually go to the window behind it. On one, Alt-Tab will switch windows and it won't work on another. All of these may happen simulataneously. Normality is restored only by restarting X.

The major problem is that I have no real way of deliberately triggering it. I have the impression that it is something to do with using the mouse and the keyboard together, but I do that all the time and my brain does not appear to be set up to recreate my muscle memory hand movements, not even immediately after. For example, it took me ages to realise that the occasional sudden and annoying appearance of GNOME Help Centres is due to accidently pressing F1. Unusual keyboard triggered events on my system are almost always accompanied by help, what did I press, what did I press?! and frantic peering at my keyboard. (Being a touch typist except for my right little finger sucks here.) I don't have a chance in hell of intentionally recreating whatever scenario is going on here unless I get Andrew to stand beside me while I type and do nothing but watch. He does have that kind of patience but he chooses when.

Using git-bisect or similar from Harrington's entry is thus going to be extraordinarily tiresome. I used version such and such for 5 days, and there weren't problems, so on the balance of probabilities, this version doesn't have the bug in question, seems unscientific. Well, unless I work out the frequency a little better and where my 95% confidence margin is. Which means I might also want the distribution of the occurences. A slightly better method probably consists of sitting down with the X.org codebase and looking at the diff for each revision for likely looking changes. (Comments like 'and this is the bit that definitely for sure makes clicks go to the window with focus. FOR SURE!' would be helpful there.)

PS Standard 'not really looking for advice' disclaimer applies. Unless you happen to have an Ubuntu or X.org bug number to hand. Or well, if you happen to know a lot about reproducing input problems in X.

Working with code

Mon, 21 Apr 2008 08:05:11 GMT

Riffing off Jonathan Lange on writing good (and reviewable) code (by the way, the filenames are a bit obscure, as in I didn't know review comments tended to be passed around in .diff files, but here's the 121kB review in question), a point I've been meaning to make somewhere, anywhere, for a while now: making large codebases grep-friendly is important to me. Specifically, when I enter a large codebase without any intention of becoming familiar with it (ie I'm fixing a bug) I really really really like to be able to grep for function names I'm coming across. (Really, I should probably use slightly more sophisticated tools, but they work on more or less the same principle.)

I was digging around in the Nevow codebase a couple of years for goodness-knows-what (actually, I think I know, and I really should look for it again, but that's not relevant here) and there were factories, factory-factories and factory-factory-factories, or something like that. It was very difficult to find the implementation of any of the many many objects that were slipping around my hands, because they were implemented with a totally different class name, or several of them, and then sort of assembled from pieces. Damn it's hard to fix bugs in code like that.

Ubuntu 8.04, status of

Fri, 18 Apr 2008 04:04:08 GMT

I felt a little bad writing this, because, well, Andrew tells me Ubuntu 8.04 (Hardy Heron, release candidate due very shortly and public release on April 24th) is very nice for him and in general I'm not much in the mood to stomp on people's work. However.

Ubuntu Hardy is really not looking like it will be a good release for me. It contains several serious regressions over the previous release on my hardware. Some of them are likely to make this the least usable Ubuntu release for me ever, on my Dell Latitude 630M. (On my university desktop it's fine, but I don't place as many demands on that.)

Major problems:

As with the beta, every few days when I am using X, particularly when using my trackpad mouse at the same time as my keyboard, the Ctrl key gets virtually 'stuck down' and I have to restart X wtih Ctrl+Alt+Backspace to be able to use my machine again. (There's not a lot of useful things you can do in X when it thinks that you're holding Ctrl down.) I thought this was bug 194214 but it probably isn't, since 194214 is (a) fixed and (b) much more hardcore than my weeny bug. I look for it on Launchpad occasionally, but it's discouraging because I have no idea what the correct search terms are, and also all bugs about keys getting stuck get marked duplicates of 194214 anyway.
The new wireless driver, iwl3945, for Intel 3945 is Free Software, but that seems to be the single good thing that can be said for it. Most of the regressions over the ipw3945 driver have slowly disappeared (although you need to install linux-modules-backports): the LED works again and I can finally use the kill switch. But it's not very stable. It causes some woes shutting the machine down and it just caused the first ever kernel panic I've had on my day-to-day machine. (I didn't file the bug on this as Andrew thought that probably the details would end up in syslog. They didn't, and so now I have no details.)
Resuming from suspend is broken for me at one time in thirty (thus more than once a week forcing a full reboot, as I suspend like its going out of fashion), which is about ten times worse than Gutsy on this hardware. I reported this as bug 217461 and now I'm trying to find out what the cause is by saving pm_state. (Wow, it's an annoying debugging process on a user machine: my system really does not like having its time reset to random things a lot. I am not sure I have the constitution to be a kernel hacker, but I guess if I was I wouldn't be usually debugging kernels on my work machine. Much.)

Between all of those, well, gar. Using Hardy will equate to sudden and necessary reboots more than once a week for me. And I need to muck around with hdparm again to try and sort out my system's version of bug 59695.

Stuff that's been or going to be fixed for release (at least enough for me): the wireless kill switch, the ignoring of many fsck errors, the insane timezone selection by the GNOME clock, the incompatibility of Java 1.4 and Gecko (although this was solved by just removing Java, which bothers someone), misnaming some wireless interfaces (this stopped wireless working after suspend for a lot of people) and the wireless LED.

One thing that possibly won't be: sound problems with programs that do/don't use PulseAudio, but that is more of a nuisance than a real problem for me, since I mostly use my Squeezebox for sound.

Finding out about locked LiveJournal (InsaneJournal etc) posts in your normal feed reader

Fri, 28 Mar 2008 23:05:27 GMT

This feature is rather old but I just found out about it. If you have a LiveJournal or SimilarJournal (InsaneJournal at least) and you have access to 'friends-locked' posts but you'd like to be able to pick them up in your normal feed reader, you can very likely use a URL like this:

http://YOURUSERNAME:PASSWORD@THEIRUSERNAME.livejournal.com/data/atom?auth=digest

For communities use the community URL followed by /data/atom?auth=digest. Similarly for LJ-like sites with their own URLs. You can also replace atom with rss if you are that way inclined.

This is described in FAQ 149 on LiveJournal.

If using a reader that is implemented in Python (eg Planet and Venus, rss2email) you will probably need to make sure you are using Python 2.5 underneath rather than any earlier version of Python, as Python's urllib2 did not work with LiveJournal's Digest-Auth implementation until just after Python 2.4 was released.

If this doesn't work in your reader, the feature you want them to add and test is called 'HTTP digest authentication'. There may also be some alternative way they want you to put in 'YOURUSERNAME' and 'PASSWORD'.

Ubuntu 8.04 (Hardy) Beta bugs wrap-up

Tue, 25 Mar 2008 23:07:32 GMT

This is in my usual tradition of going over the bugs before an Ubuntu release. It's a good time for Ubuntu, if I'd done this even last week I would have been more annoyed.

The most annoying bug of all has been around for quite some time, and may not be an Ubuntu bug at all, but rather a BIOS power management or disk firmware bug: bug 59695. This would be what cost me my last hard drive, which failed at a reported 1.7 million load cycles. The new drive is already at 2257, which is a bit high as well although I've tried various workarounds. The trouble with this one is that firstly the power saving settings of the drive appear to be totally opaque. Just try some numbers! Watch for high temperatures, although we don't know what 'high' is for your particular drive, nor can we tell you how to work it out! My drive will probably last longer now, but the laptop is painful to touch after a while. Great.

Bug 194214 is quite seriously annoying too. For me (and I don't use Compiz) it manifests as my Ctrl key being virtually 'stuck' down, so that if I press 'q' applications terminate, 'd' closes my shell, 'Page Up' switches tabs, 'c' sends SIGINT etc. An X restart is required to restore normality. The community is on this though, the report is quite impressive and git bisect has been used.

Bug 193970 is a regression from a user's point of view, if not a programmer's (for the latter, the important distinction is that it's not actually the same software). The problem is that Ubuntu is now using the Free driver for the Intel 3945 wireless chipset (iwl3945), rather than the other one (ipw3945). iwl3945 doesn't really support the 'wireless off' switch, well, at all, unless you consider rebooting after using it an acceptable solution. This isn't bugging me much at the moment because I've learned to leave wireless on all the time, but it is annoying when I take my laptop on trains and similar and the battery drains needlessly fast. It looks like this will probably survive to the release, I will likely switch back to ipw3945 for the duration of Hardy's lifetime.

Bug 204097 (which may be a duplicate of something else) probably cost me some data in the hard drive failure. Essentially they've decided to put a nice wrapper around fsck (the filesystem checks) that does not handle a check failure at all. It just reboots and tries it again. And again. And... you get the idea. Nor does it inform you that this is even due to a failure. You have to guess and boot into recovery mode yourself. Of course, this is a hard one to solve correctly, because a typical desktop user is eventually going to be told and now you have to do something very weird and difficult. But the 'just hope it doesn't fail the next boot' thing is weirder.

Bug 185190 is just mystifying. Essentially the GNOME world clock programmer has decided that it is really hard to work out programmatically what timezone a city is actually in (and it is, you try it) and so they'll just guess based on the longitude. Fortunately this only fails for very minor unheard of cities like Beijing and St Petersburg. Oh, and a bunch of major North American cities, which I genuinely am surprised is considered acceptable.

The major fix I've noticed is that bug 153119 (microphone was more or less useless on my laptop due to very soft volume) seems to be gone. This one surprised me since there was no response to the bug itself. update-manager is marginally better too I think. NetworkManager is fine, but I'm not using the Hardy default packages... Suspend and hibernate both work, that's a shock this far out (a month) from a final release.

Building an online shopping site for which I will not kill you

Tue, 25 Mar 2008 11:19:52 GMT

I've done a fair bit of shopping online recently, and I'm just about ready to kill everyone. Here's how to not be on the hit list:

Let me compute shipping costs without having to give you my name, full address, email, phone number and chosen password. If you're an Australian site, you can work it out from my cart and my postcode. If you're international, my cart and my country. I know full well that you make a ludicrous amount of money from 'shipping' and I'm factoring it into my price comparisons. I'm getting to the stage of assuming the worst if you make me sign up before revealing shipping costs and I'm bypassing your site. No really, I am, I'm not buying from you any more, because 5 minutes signing up is 5 minutes too long.
If you sell electronic equipment, be upfront about whether it's grey market and if so, where the warranty holds (ie, in the event of failure, do I have to have it couriered to some other country to be fixed, or is it an Australian warranty?) If it's in any way unclear, I am also assuming the worst.
Ideally, debit my credit card at the time of shipping, rather than at the time of placing the order. (I'm usually not big on waaa waaa doing business is hard, that's why it's hard to buy from us, but you should anyway because capitalism means you have to buy things but I'm kinda sympathetic to avoiding credit card fraud, so often you get a pass here.)
If you only have a web form for customer contacts, make sure damn sure it works. And by works, I mean the mission critical kind of works too, because it sure is annoying if the last POST-PAYMENT phase of the order fails and I can't contact you about it.
When I do file a support request through your web page, how about automatically emailing me a copy of it, ideally with some kind of tracking number? That way I have some reasonable assurance that it at least made it as far as your server. If you put up a generic 'Thank you for your request, we will eventually respond' page, I don't know if my actual request got through. Especially if a payment just failed...
I know you get a lot of dumb support requests. But please, please, don't put up that page, you know, the one that goes man, you guys sure are dumb. This website is infallible and yet all the time waaa waaa waaa customers can't order because customers can't read our info even though they somehow were literate enough to apply for a credit card. Don't blame us if we're cranky about your dumb complaints. You're lucky we even have this non-functioning web support form up at all. Because one day your third party gateway will ACCEPT A CREDIT CARD and your clever clever system will fall over before inserting the associated order into your database and then your contact form will also fail and then you will look rather stupid for talking to the customer about how dumb they are, won't you?

I suppose I should mention some good systems here, shouldn't I? OK. If you buy contact lenses through Net Optical Australia you'll get so much feedback from them about your order status that your mail server might keel over. Glasses Online is fairly good in that respect too (they'll even phone you to double check your weirdo prescription, if you have one). The good people behind the Nine Inch Nails album were very fast with their help despite however many million calls for help they were dealing with.

I should mention the bad system here too, but my understanding of Australian libel laws make it kind of dangerous. How about you guys just take the chargeback on the chin and we'll call it even? (I will say though that unfortunately having clear-cut statements about shipping costs and warranties apparently does not totally correlate with a functional ordering or support system.)