Structure and Interpretation of Computer Programmers

Bottom of the page, under Media Reviews. I’ve got another couple of review copies sat here, too…

So, they said that Steve Wozniak would be there, and that he’d be signing books. So I took my book to be signed. That wasn’t wrong, was it?

N.B.: yes, I bought a copy of iWoz and had that signed too. But the iBook is cooler ;-)

The people credited with bringing GNUstep support to OCUnit a few versions back (at least one of whom I recognise as a competent programmer who really knows what they’re doing), as the current version just won’t work at all ;-).  It’ll be more future-proof on the Apple platform, as it uses @try/@catch blocks.  However, as I want to use it on the GNU platform, this means a lot of #ifdef __NEXT_RUNTIME__ wrappers and NS_DURING/NS_HANDLER/NS_ENDHANDLER blocks…

In the spirit of My Dream App, I’ve invented my own dream app.  BestAppEvar.app would be able to divine what needs to be done by detecting my brainwaves, and would then do it when I hit the button.  To make it easy for you to implement, I’ve already designed the UI:

So, why hasn’t it been made yet?  Come on, you lazy coders!  The hardest bit would be the brain-computer interface, but there are example I/O Kit projects on the ADC site.

I’m currently having a Vaio VGN-S4M inflicted upon me.  I can’t say I dislike it totally; the X-black screen is rather nice and it has one killer feature in that there’s a (physical) radio kill switch on the front.  However, by and large I do dislike it.  The Centrino wireless jobbery is not fully documented, so only works with a binary blob driver which means it’s useless for most of the operating systems I care about (it doesn’t work in CEntOS, for instance, and I don’t have the luxury of being able to switch to Ubuntu where I’ve heard better results are possible).  It seems to run very hot doing anything (including nothing), so the fan constantly winds up and down.  And it’s a loud little fan.  The whole keyboard seems to bend a little when I press any key (although I’m used to the Tactile Pro, so probably whack a little harder than necessary…)  The only saving grace in the design is that PC manufacturers seem now to be getting over the desire to install legacy ports all over their laptops; but the thing’s still closer to the size of a 14″ iBoko (hi u.c.s.m) than that of its brother, the 13.3″ MacBoko.

So, with a recent cash injection and an ADC hardware discount coupon both burning a hole in my pocket, as well as a desire to crack on with the ObjC 2.0 work on the c.l.o-c FAQ; it seems an Intel Mac and a copy of some virtualisation tech are in order.  The question becomes simple: do I jump now, and get a MacBoko or MacBoko Pro, or do I hold on in case the Core 2 Duo variants are around the corner?  Or I could even combine the two and get an iMac, keeping the Vaio for corridor worrying?  I’m tempted by the “buy now” approach, as I actually need^Wwant a new system now, not in January…

An interesting time if you happen to be an aging startup superserver; Ubuntu are to replace init with Upstart from "Edgy Eft". That’s quite cool, the model in which everything needs to always come up and always in the same order put forward by both styles of init is long dead, and the system V style of init is particularly cumbersome (though someone at Apple clearly liked it, as they had both SystemStarter and watchdog in the past).

I’m actually both surprised and pleased to see a Linux distribution making the jump here, I’ve always considered them fairly conservative (apart from in throwing any old free package into the distribution; I mean from a "core stuff"[*] perspective. I know that FreeBSD attempted something with launchd last Summer, but the latter has too much mach_init magic which can’t cleanly be excised.

[*]now Apple are going to start a CoreStuff API and sue me. Fantastic.

One thing from TFA saddened me (though I really ought to have expected it), and that’s this:

To avoid reinventing the wheel, we first looked at how much effort it would be to use of modify the existing replacements to be able to do this. Sun SMF and Apple launchd were immediately ruled out due to licence issues. It was important for us that the solution be uncontroversially free so that other distributions might adopt it; many had already rejected these for GPL incompatibility reasons.

Yes, it’s the standard "GPL first, utility second" argument. I have a fairly strong opinion here: if something works, and I can see that it works, and it works better than any alternative I have access to, I’ll use it. That’s why I’m posting this from OmniWeb on a Mac, despite [i]there being free web browsers around, [ii]my work involving Linux. I prefer to have access to the source, except where that involves a retrograde step in terms of utility. Anyway, I digress; the point here is that launchd is released under (well, depends which version you look at) the Apache licence, and OpenSolaris under the CDDL; both of which are free software licences, but are incompatible with the GPL on technicalities. That’s nice if you really do want to split hairs, but GNU/Linux (if you like) is supposed to be a usable OS so shouldn’t utility come first? Admit it, how many of you have uninstalled kaffe or gcj and are using the Sun jdk? More to the point, how many of you are using Apache (which is also released under the Apache licence)? It’s time to get over it. I propose that if you want to work on a pure GNU system, you should indeed work on a pure GNU system and hie thineself over to the HURD mailing lists. I fully intend to, if a gobbet of spare time makes itself available soon…but more because I think the HURD’s cool ;-).

You can’t use a java.awt.Color in WebObjects, because to use AWT at all on OS X requires connection to the WindowServer.  And unless you’re mad, you probably aren’t running your WOA as root.  This means I can’t do things like, ooh, I don’t know, making a PDF table have a white border instead of a black one.

Strange things can happen when I get bored.  There’s a great little dashboard widget called WikityWidget, which lets you organise notes like a wiki.  Well, I thought, no point in only having my notes on one computer, why not scrape the wikits out of WW and put them online?

You may be interested in some source code.

tyr:/Library/Parallels root# ls -l
total 16
-rw-rw-rw- 1 root wheel 40 Sep 12 15:52 .dhcp.en2
-rw-rw-rw- 1 root wheel 0 Jul 4 17:10 .dhcpd_configuration
-rw-rw-rw- 1 root wheel 0 Jul 4 17:10 .parallels_common_options
-rw-rw-rw- 1 root wheel 100 Jul 4 22:44 .parallels_license_2.2


I can waste a lot of time if an interesting question gets posed. The most recent culprit was Chris Ridd in uk.comp.sys.mac, wondering aloud if threads ever got shuttled between CPUs on a Mac. Here we go…

It certainly looks like the conditions for doing this through the API can never be met on a real Mac running xnu. All you can do is assign a thread or a task to a processor set, but not a single processor. Unless that processor happens to be the only member of a processor set. Thing is, on xnu there is only one processor set, which encompasses all of the processors. So there’s no way to force your threads onto a particular processor in Mac OS X. The lack of multiple processor sets means that you couldn’t have a box with, for instance, both a G5 and a Xeon running a single kernel, which is kindof sad in a way. It won’t get missed, though.

It doesn’t even look like there’s an API to work out which CPU you’re currently on. What you can do is get the port for the default processor set (the only processor set), then by manually furtling with the structs you can iterate through the CPUs (or you can ask your own mach_host_port for an array of the CPU ports). For each CPU you can get the thread queue, which you could compare with your own thread to see if it’s the same. That’d be tedious, but would get the required information. Once there though, I don’t see any way for the thread to move between any queues except the idle and run queues on its ‘native’ processor; so I think the answer is that no thread ever migrates between CPUs. I may be wrong, and am happy to entertain any information to the contrary.

Unsurprisingly with no API to do what I want, little useful code came out of this exercise. I found out how many cpus the system has, but that’s it really.

Update 2006-09-10 16:25 GMT – I hate this not knowing, so I decided to play the Ask Amit card ;-).