So the other day a collegue of mine shown me the 3dview of Firefox's inspector tool. It's seriously awesome.
Firefox -> Inspect element (Q) -> 3dview
This is just an update to synchronize what I have with devkitPro's distribution of grit. This includes updates to the makefile, and turning back the way the size-constant was defined back to a #define. Apparently, consts aren't constanty enough for C compilers for use in array declarations. Shame, I would have liked to get rid of macros as much as possible :(.
In any case, the two versions should be identical again (with one small exception, namely that my version emits a .size directive for assembly, but that's a minor something that should not affect anyone.)
Okay, so it's been a while, but there's finally a new version for grit.
First of all, the vector::insert should finally be fixed. And there was much rejoicing. I've also added an option for forcing the map palette-index (-mp <num>, which should help with NDS backgrounds that use ext-palettes.
Also – and this one is pretty big – I've completely replaced the tile-mapping routines for something more general. The new method should be able to handle variable-sized tiles (-tw <n> and -th <n>) and is mostly independent of bitdepth. Specifically, bitdepths over 8 bpp can be handled as well, at least in principle. It also means that the external tileset can be a metatile-set as well now, which is good if you're using metatiles.
With this new method also comes a way to create a custom bitformat for maps (-mB flag). I'm not entirely sure how this can be used yet, but using more than 10 bits for the tile-index, or a 1bpp collision map should be possible now.
Since this is a fairly major change, I kinda expect there's still some bugs in the system. I have tested it for a number of options, but you know how it is with multi-platform stuff. In particular, if any of you big-endian-system users have trouble now, this will probably be the cause.
And now I will leave you with a …
Random trivia: today is January 2nd, 2010. Or, in the One True Date Formatting, 20100102 : a symmetrical date. The next one won't be November next year.
I think too much. Or so people keep telling me. And they may have a point.
Anyway, so I'm working on this assembly version of
toncset
for, well, just because I guess. A fill
routine has 3 parts: a head, a main run and a tail. The main part
fills 32-bit chunks (words) when there's more than 4 bytes left and
when the destination is word-aligned. This part is easy, because
you can just dump words with stmia or str.
For an example of this, see my older
memset16 post.
The tail is for the remaining bytes after the main part. Under normal circumstances you could do this byte for byte, but some sections of GBA/NDS memory do not take kindly to byte-writes, so you'd have to read the word, mask the appropriate bytes out/in and then write it back. This is mostly just annoying, but still very doable.
The head part, however, is both annoying and tricky. It consist of filling the unaligned bytes in the first word of a run so that the main part can do its thing. This is similar to the tail part, in that it requires bitmasks. However, it's also possible that both the beginning and and of a run occur in the same word, effectively making the head the tail as well, so you'd have to apply a double mask … somehow. In C, it looks something like this:
This bit of C translates roughly into the following ARM code:
The main thing I thought when I'd written this down was “meh”.
You will note that registers r4 and r5 are
used here, which means stack-work (omitted here for brevity). The
positioning of pushing and popping makes everything a little awkward,
so I was off looking for something else.
The essence of the problem here is that you can only use five registers
without touching the stack: r0-r3 and ip
(r12). Now, r0-r2 are taken
by the destination, fill and size, so I can't do anything with those.
I also need one to store the left-edge (r3 in this case),
leaving us with one for the right edge, the left and right shift
intermediaries, and the left and right masks. Right! Crap -_-.
So; strategies. Well, one of the reasons I need to use so many
registers is because the lifetimes overlap. For example, I still need
left for a while because shifting the mask up comes last
here. I can't use r2 for multiple purposes either because
I'll need it for the size. Now, I could free up r3 by
making the left-mask first, but then I might get in trouble when creating
the right-mask. Also, right-4 is actually
what size wants to be when it grows up in the long-run
case, so I can use that there as well. I'd just have to undo that
for the short case, or perhaps even create the right-mask from
negative numbers.
At this point I figured it would be helpful to take a look at the
various ways of creating the masks I needed. The standard form for a
0x000000FF-style bitmask is (1<<x)-1, but there are
others as well. The following list holds a few examples.
All of these use +1 or −1 as their base, and all but one is
a two-instruction affair. The left-mask looks like 0xFFFFFF00, so
the most obvious one to pick here is -1<<x.
Technically, the right-mask is 0x000000FF, using
x = 8*right = 8*(left+size).
However, you can also see it as a 0x00FFFFFF-style mask if you
use 4-right. This solves two problems at once. First,
it is the negative of the new size, so the value is readily available.
Second, this mask is a right-shifted 0xFFFFFFFF, but as the lower bits
are shifted out anyway, it doesn't actually have to be a proper
0xFFFFFFFF; it can be a 0xFFFFFF00 as well, which we have in the form
of the left-mask. In other words, we don't require as many registers
for temps because we already have everything we need. The resulting
code is this:
See? No r4 and r5 anywhere. The
key is toying around with r2 and r3. While
r2 is reserved for the size, it needs to modified anyway
to account for the work done here. In the end, size should be
right−4, which is what points (1a) and (1b) do. Since
right-4 is a right<4 as well, we can use
its result as the condition for the special case; the result
being the negative distance from the word-edge. As explained above,
the right-mask can be constructed from the left-mask by
lmask>>(-8*size), which is done at points (2) and
(3).
It's a little hairy, but it works. And yet, it still evoked a feeling
of “meh” like before. It's the two instructions at point (2) that annoyed me. The reason it's two instructions and not one is because you
can't multiply by −8 in one go. By +8, yes: that's a
shifted-mov; −1, yes: that's
rsb, r2, #0; but the combination is difficult
because the shift only applies to the second operand. A
sub r2, #0, r2, lsl #3 would do it,
but the first operand needs to be a register and I don't have a spare
one with zero in it. I could make one, that just means I have an
extra instruction somewhere else. I do, however, have either
a +1 or −1 in ip, maybe I can use that somehow.
And then it hits me: the carry flag!
There are adc, sbc and rsb
instructions that add C, C−1 and C−1
to the result, respectively. Setting or clearing the carry flag is
easy, so that's not a problem. All I need now is to start the
flag using +1 instead of −1 to cancel out the −1 in sbc or rsc. As it turns out, I can do that
I use this format for the left-mask: -(1<<x). In the
mask overview above I listed thi as a 3-instruction gig, but as it turns
out I can use the carry-trick here to for one instruction less. The final
version (for just the head part) looks like this:
Sweeeet :). I was happy with this, until I realized what I'd been working on: an exception of an exception. This would definitely not be part of the 20% of the code that uses 80% of the runtime, so it's really not something one should worry about. Interesting, yes, and I learned a few new tricks, but perhaps time would have been better spent on getting 5% extra out of the main loop. The only problem there is that that is just boring old unrolling a bit, whereas the head presented a more ‘interesting’ problem so I went for that instead.
So yeah; I think too much >_>
Expelled : No intelligence allowed! Give them a hearty round of scorn and ridicule, folks.
OK, perhaps a bit of backstory is in order here.
There's this strange thing going on in the USA known as the Creation-evolution controversy. In a nutshell, on one side you have the Theory of Evolution, accepted by all but a fraction of the scientists and supported by evidence from multiple fields; and on the other you have groups (usually motivated by their religion or ignorance and frequently both) screaming “nuh-uh!”, backed up by arguments ranging from utterly insane, to fabrications, misunderstandings, red herrings, and “I dunno, Magic Man dun it”. No, I'm not embellishing here: there are long lists of creationists claims that often make no sense at all, but are still used even after being debunked decades ago. As an example how silly these can be, consider the Banana argument. And no, this is not a parody; they're absolutely serious.
After the scientists got so fed up by the constant misrepresentations that they won't even debate anymore and several defeats in courts, the creationists came up with a new strategy: Intelligent Design (ID). They've been quite clever with this, actually. For one, they're leaving the Bible out of it and claiming that life's complexity can only come about through an intelligent, yet unnamed (wink, wink), designer. They also claim that all they want is a fair hearing; that the scientists are being mean with their insistence on evidence and refusal to accept bogus reasoning.
Enter Expelled. You'd have to read the wikipedia page for details, but the idea behind the movie is to highlight this repression by scientists; that the evolutionists are actively ‘expelling’ people critical of evolution. It so happens that they've interviewed a number of evolutionary biologists (under false pretenses) for their views on the subject. This is now widely regarded as a bad move.
You see, one of them happened to be PZ Myers, a vocal critic of creationism and other irrationality on his blog pharyngula. You can see how hostile he is in this video (I'd point to the Expelled trailers with the interview, but they pulled it). Ever since the interview, he and other science-bloggers have been keeping an eye on the movie, pointing out flaws in the producers' arguments whenever they went public with anything.
And now it gets interesting. About two weeks ago, there was a screening of the movie in Minneapolis. He reserved a place via their website, went to the theatre … but was barred from entering. To spell it out: here's a movie accusing evolutionists of expelling their critics, expelling their critics. And then lying about it afterwards! Repeatedly! Seriously, you just can't make this stuff up.
Naturally, this is now all over the blogosphere. The original account has well over 1600 comments. Many other science bloggers have commented on it as well. Greg Laden's blog has a list of over 100 links, including to stories from the NY Times and Salon. Another interesting detail is that Myers was accompanied by Richard Dawkins (yes, that Richard Dawkins), who did get in. The two had a nice little discussion afterwards, which can be seen here.
Other interesting links
I use quite a bit of code in my documents. Now, you can't exactly copy code from an editor to an HTML page … at least, not if you want formatting to be maintained. Before now, used my standard text editor to convert it to html, and then post-process to remove excess styles and such. This worked, but it's still a little cumbersome.
After some searching, I found GeSHi, a php package that will convert and highlight code for use on the web and it is very customizable as well. Very nice. Before I had even looked into how I could use this, I found out that there is a WP plugin that uses it as well: IG-syntax hiliter. So now I can do this:
That should be C code. And by golly it works :). Now I just have to make something for ARM asm.
There are some caveats to the plugin and geshi, though.
$geshi->enable_classes(true)' and
`$geshi->set_number_highlighting(true)'.
parse_non_string_part()
use this instead:
[php]
$reg= "#\\b((0[xX][0-9A-Fa-f]+)|([0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?)|([0-9]))\\b#";
$stuff_to_parse= preg_replace($reg, "<|/NUM!/>\\1|>", $stuff_to_parse);
[/php]
Regexp help courtesy of www.regular-expressions.info.
Ever since I started my non-university site, I've been meaning to create a nice DB-driven back-end to manage it all, perhaps with some bells and maybe even whistles. However, I never came round to doing so because, well, I'm not exactly fond of building interfaces and there was other stuff to do as well. It also seemed a bit silly to do all that work myself when there are other packages out there that do everything for you. So in the end I decided to follow in the herd down to wordpress.
It's … nice. Changing styles is easy and you can build your own page templates and text filters to customize everything. One of my worries was that it'd limit me in my post formatting, but I can do everything in HTML just like I always did … once I turned off the visual editor and removed the wpautop and wptexturize filters. Of course, one of the downsides of using someone else's system is that you have to learn how everything works. So at the moment everything's still pretty simplistic. I'm not entirely sure if the stuff I have can really be presented the way I want by wordpress, but I seem to get by so far. At least I'll be able to update a little easier now.
So, this is what my site looks like now. Yeah I know, bland site is bland, but at least it works. There's posts over here ↓ and a navbar over there →. You may notice that there are two links to ‘projects’ there – that's something wordpressy. It makes a division between ‘Posts’, basically journal items with timestamps, and ‘Pages’, which are standalone. Tonc would be an example of Pages. The projects page and documents would be part of that too. Updates on those items, however, would be announced as posts.
Oh, and yes, I have been a little revisionist in the post orders. The past month or so has been a sort of trial run for all this stuff so there are many posts all at once right now. We apologize for the inconvenience.
There is/was a rather annoying bug in wordpress 2.3. Normally when editing pages in the advanced editor, the actual text of the post/page has to be preprocessed to convert things like × to &times; so that it wouldn't show up in the editor as ×, and ditto for angle brackets. The extra ampersands and brackets would then be removed before saving. However, in the 2.3 upgrade a few things in the core structure of post/page retrieval had been changed and the somehow the the page-retrieval didn't do the pre-processing anymore. The upshot was that the amps and brackets got converted to normal ascii and unicode, seriouslycompletely messing up your pages.
I managed to track the problem to get_post() and get_page() in wp-includes/post.php. get_post() did get the upgrade, but get_page() didn't. The latter needs to be updated to carry and use a third parameter, and call sanitize_post() like get_post() does.
Of course, right after doing this I found out that a fix was already present in the SVN. Just update the file with this one. Ain't that always the way.
To see if you are affected as well, make a new page and input the following:
× > entities
Then hit `Save and Continue Editing'. If the text has changed to “× > entities”, you're in trouble: every page you edit in that state will have its entities converted. Get the fixed file as soon as possible.