Thursday, 24 April 2014

Buying petrol discounts

If you have to spend $5 in store to get a 4c/L discount on petrol, then you'd better be buying more than 125L of petrol, or else you just got screwed. For example, if your petrol was priced at $1.40 per litre and you filled up with 40 litres, that's a total cost of $56. If you buy $5 worth of chocolates to get the 4c discount, then your petrol is $1.36 per litre and your total cost is $59.40, or $3.40 more than you would have paid without getting the "discount". It's only when 4c per litre adds up to $5 that this becomes worthwhile. $5 divided by 4c/L gives 125 litres.

If you buy items you would have bought anyway, but at the higher petrol station prices, the calculation is more complicated. You only have to count the extra dollars you paid over supermarket prices for milk and bread and convert that into litres. Let's say you buy milk to get your discount, because you are running low at home. You pay $5 for 3L of milk but you would have paid $3 at the supermarket. That's an extra $2 you paid to get your petrol discounted by 4c/L. For that to be worthwhile, divide your $2 by the 4c/L discount and you need to be buying 50L of petrol to hit the break-even point. It's more plausible, but for me, personally, my car only has a 40L tank, so it is never worthwhile for me to spend $5 at the petrol station to get a 4c/L discount, even if it's something I already need.

Mokalus of Borg

PS - Dollars spent for the discount (D) = cents per litre discount (c) times litres bought (L).
PPS - Plug in the two numbers you know and solve for the remaining one to find out whether it's worthwhile.

Wednesday, 23 April 2014

Phone space used by Pocket

I started using Pocket for offline reading on my phone when Instapaper stopped being useful enough. I used to delete articles when I was done, just because the alternative was archiving, and I just didn't see the need for an archive of my read articles. Also, I assumed that Pocket was going to keep that archive to make a profile and sell my data. I still assume they're doing that, but I started using the archive for one very simple reason: it was faster. Archiving an item is one click, deleting is two, because every delete has an "are you sure?" confirmation question. So my archive started building up. Now I'll have to start deleting articles again because, it seems, Pocket stores the archive on my phone, taking up extra space. I currently have 2.2GB - that's 20% of my phone's available storage - taken up with Pocket's cache of article images from alone. There's more than 3GB total, and a good chunk of that will be the archive (assuming my theory is correct). The archive has to go, which should release some space. I'm not sure how much. If I want to release the maximum amount of space that I can, right away, I need to find, read and remove any articles that contain animated GIFs. They are by far the biggest images stored by Pocket which, unfortunately, can't display animated GIFs anyway. Starting this week, I will be aiming to destroy my Pocket archive, because that will save space on my phone and prevent it from being used as a marketing tool against me.

Mokalus of Borg

PS - I used an app called DiskUsage to figure this out.
PPS - It works pretty well.

Tuesday, 22 April 2014

An update on the universal playlist

I've been keeping all of my entertainment in one big playlist for a little while now, allowing me to focus on books, movies, podcasts or TV shows that seem most important to me at the time. I vote for them against each other, deciding which of two items I would most like to be doing at that time. When a few rounds of voting are done, some clear winners emerge, and it's much easier to choose something fun from that smaller list. Incidentally, this is also how I choose which blog posts to make here, out of the huge backlog I have in storage.

The first observation is that, because of the way the list works, new items don't get voted down immediately. They don't have to fight for position against the top performers. This means new items actually have an advantage over older ones that already got voted down. I will often get something brand new come to the top of the list despite only having added it the day before. This is a bit against the ideal I set out to embody with the list, but I don't think it's been too big a deal yet. We'll see.

The second observation is that I really don't have as much time as I thought. I'm not getting through any more entertainment than I used to. I'm just getting more variety and more quality. It's good, but the list does continue to grow. As I write, I have over 400 items on the list. As I add more, they're not going to go away more quickly. It is likely that this list will continue to grow longer as long as I use it, unless I look at the tail end and decide there are some items I will never need to bother with at all. Those I can cut out.

It's funny how the size of the list still plays on my mind. I know I don't have to get it all done. That's why I use it in the first place. If I can't do everything, I'd better do what's important or most fun. Perhaps this means I just haven't accepted my own mortality.

Sometimes the voting is hard. Two items that I'd really like to do come up against each other, just at random, and I have to choose between them. Or two really bad ones. That's just as difficult.

Mokalus of Borg

PS - On the whole, though, it's working pretty well.
PPS - I've changed software once since I started. I wrote both myself.

Monday, 21 April 2014

Facebook doesn't do news well

For me, at least lately, Facebook is a terrible way to get official news. It's buried under cat videos and Candy Crush invitations and I'll often skim right over special-interest news I would otherwise very much like to read. For companies looking to get the word out, Facebook is terrible in a different way. When you post something to your company Facebook page, it only goes out to 5% of your followers - people who have deliberately sought you out and linked their profile to your page because they want news from you. Apparently, if you pay Facebook a gatekeeper tax, they'll bump that number up to 10%. So, basically, Facebook is terrible as an official news channel.

Mokalus of Borg

PS - I'm also not on Facebook every day, so I miss news that way, too.
PPS - And I don't always read my whole news feed when I'm there.

Friday, 18 April 2014

Faith in large primes

I saw Adam Spencer give basically this same talk at Tech Ed 2011 in Queensland. He talks about prime numbers, the ongoing search for larger primes, the discovery of Mersenne primes and one particular number, known as M48, that is simply too large to show on a slide, let alone to comprehend its massiveness.
Because it has been proven prime, and it being the largest known prime so far discovered, Adam says that he knows, with the same deep-down certainty as he knows anything else, that this number is prime - it has no factors but 1 and itself.

The thing is, what he's talking about isn't knowledge as such. Rather, he has faith that this number is prime. He has faith in the computers and software that performed the proof. He has faith in the people who created that hardware and that software - that they did not make mistakes in creating them, nor in running them. That no unforseen errors occurred and were accidentally buried. That no deliberate fraud was committed in order to claim the title of the discoverer of M48 (though I'm also pretty sure that's not the case). Because unless he performed these calculations himself, Adam cannot really know that M48 is prime. He is trusting that judgment to others. Trust and faith in maths too big to do for himself. That's what Adam has. It might not seem like a significant distinction, but it makes a significant difference when discussing science.

I don't, personally, know any forensic science, archaeology, anthropology or molecular biology. I trust my understanding of those topics to trained people or, more accurately, to popular journalism of those topics, filtered through all the news channels and brains that stand between me and the scientists doing that work. There are a lot of layers to trust there - a lot of translation and assumptions of honesty or even just accuracy. The point is, a lot of what you "know" about science is based on faith in a lot of people doing their jobs honestly and accurately. That is trust or faith, but it is not knowledge.

Mokalus of Borg

PS - Faith that computer hardware works as designed is pretty well-founded these days.
PPS - There are plenty of places where the story could go wrong, though.

Thursday, 17 April 2014

Browser security

When websites are more like apps, we need to be able to grant or deny permissions to them like we do any other software. A firewall or whitelist that allows or denies code full permissions based on its origin is too coarse, and most people aren't even doing that much with their desktops, let alone their browsers. Browser security is probably the next big battleground.

Mokalus of Borg

PS - Actually, it's probably the big current battleground.
PPS - It is, after all, the biggest sector of computer use right now.

Wednesday, 16 April 2014

Clock vs timepiece

I learned something recently. In a couple of TV shows I've watched - specifically Heroes and Grimm - there is a character who works with clocks, though they are careful to use the term "timepiece". I thought this was just weird professional terminology pedantry, but then I read the Wikipedia article on clocks. It turns out that the word "clock" is derived from a word that means "bell", so a device that tells time but has no bells has a different name, "timepiece". So that's why your wristwatch or cheap wall clock is technically a timepiece. It also means that the name "Big Ben" for the Clock Tower in London is slightly more accurate than you might think after hearing that bit of trivia that Big Ben is actually the bell, not the tower.

Mokalus of Borg

PS - This also might make sense of the word "glockenspiel".
PPS - Though maybe not.