Older blog entries for lloydwood (starting at number 94)

21 Jan 2011 (updated 21 Jan 2011 at 16:19 UTC) »

Radio astronomy

We've been doing some work for radio astronomy -- not on the astronomy as such, but on the computing and networking that will needed to support the new generation of high-end astronomy arrays that are being designed and built, such as the Square Kilometre Array.

The idea is to be able to use existing Internet technologies -- fibre, Ethernet, IP -- but engineer their use to support very high speeds, using a transport protocol that we've designed, called Saratoga, that is in use to transfer imaging data from IP-enabled remote-sensing satellites.

So, here's Taking Saratoga from space-based ground sensors to ground-based space sensors.

Human interfaces

For years radios had been operated by means of pressing buttons and turning dials; then as the technology became more sophisticated the controls were made touch-sensitive -- you merely had to brush the panels with your fingers; now all you had to do was wave your hand in the general direction of the components and hope. It saved a lot of muscular expenditure, of course, but meant that you had to sit infuriatingly still if you wanted to keep listening to the same program.

-- Douglas Adams, The Hitchhiker's Guide to the Galaxy, ch. 11, 1979.

"Rather than bending down, leaning forward or picking it up you can use larger movements a little bit further away to do things like volume up or next song without changing modality.”

-- Stian Aldrin, CEO of Elliptic Labs, quoted in Kinect-like technology for iPad to wave through CES, Fabrizio Pilato, Mobile Magazine, 21 December 2010.

(I haven't touched SaVi at all this Christmas.)

22 Sep 2010 (updated 27 Feb 2011 at 00:27 UTC) »

SourceForge use

Interesting viewing Sourceforge download statistics for my SaVi satellite constellation visualization software. Most downloads are from the United States - no surprises there - but from Windows. Is everyone really installing Cygwin to use SaVi?

I grumbled previously about SourceForge project rankings; I see SaVi is still ranked 4000th or so out of around 240,000 registered projects. Which is about top 2%. And yet I have very few users or user activity - but 236,000 or so projects must have even less. Perhaps this lack of activity and lack of related advertising revenue helps explain why Sourceforge are laying people off? Geeknet, the parent of Sourceforge, recently announced losses, the departure of their CEO, and that they were changing their NASDAQ ticker symbol from LNUX.

In an idle vacation moment I did a redesign of the iPod shuffle. In, for my sins, Powerpoint...

Tcl/Tk on Mac OS X still broken

I've previously written about Mac OS X Tcl/Tk menu problems, which prevented SaVi from using the Mac menubar on 10.5 Leopard. That was fixed only by upgrading to 10.6 Snow Leopard. (Okay, downgrading to 10.4 Tiger also works, if your hardware supports it - but who wants to do that?)

I've just added accelerator key (menu shortcut) support in a SaVi development update. This is not straightforward - the Tk commands and binding are a bit arcane, not easy to get right, and you have to do things like bind both the upper- and lowercase keypresses - and it's even less straightforward if you're crossplatform, as I am.

Imagine my joy on discovering that pressing a newly-implemented menu shortcut on the Mac - and only on the Mac - froze the application. (This is on 10.6. Remember that in 10.5, you can't even use the menubar, and have to use my workaround popup menus, where accelerators work.) So now there's a workaround to turn off menu shortcuts on the Mac, except when you're using the workaround for 10.5, where the menu shortcuts work, but the menubar itself doesn't. Clear?

As usual, Tcl/Tk on other platforms Just Doesn't Have These Problems. I think Mac Tcl/Tk's problems are due to being over a decade less mature and stable than on other platforms (Tcl/Tk on the original Mac OS never went very far, as far as I know), with perhaps Apple selecting versions of Mac Tcl/Tk to ship in OS releases without communicating with Mac Tcl developers about what might be best to ship also being a factor.

I bought a MacBook in 2007. I ported my application to it, but couldn't get a Mac menubar. I worked around that and a bunch of other Mac-specific problems, and bought Snow Leopard in 2009. Now I have a menubar, but not with menu shortcuts.

Do I want to be a Mac developer? Well, have you seen what happens when I put the work in to try to get a reasonable Mac interface for my crossplatform application? It's just not worth it.

1 Aug 2010 (updated 1 Aug 2010 at 15:16 UTC) »

Playing with SaVi again

I've added a simulation of the NeLS constellation to my SaVi satellite visualization software . This was prompted by stumbling across papers that used NeLS as the basis for analysing the effects of overlap of satellite coverage areas on the use of intersatellite links in a mesh constellation -- papers based on the work in Chapter 7 of my PhD thesis and my 2001 AIAA diversity paper.

As I never got around to fleshing out that work with a journal paper, it was pleasing to eventually discover that someone else had done so, copying my simulation method and validating my results.

(My PhD thesis has been cited fifty times now, which is either a reflection of being useful to others, or of just being on the web.)

More fun with MIL3 Opnet

I previously described problems using MIL3's Opnet simulator under linux.

I've just discovered that the Opnet error log in ~/op_admin/err_log is 128 MEGABYTES in size. Silently created, stealthily lurking.

Remember, kids, it's all about application and network performance.

9 Jun 2010 (updated 11 Jun 2010 at 10:56 UTC) »

Fun with MIL3 Opnet

MIL3's Opnet 16.0 was installed on a local network today, so I thought I'd try it out.


> opnet &
[1] 28779
> 
********************************************************
NOTE: Use of 'opnet' as the program name is deprecated,
and will not be supported in future releases. Please use
the actual program name to run the software.
********************************************************

Right, I should have invoked it by typing modeler, with the US spelling. Rather than 'modeller,' as it's spelt in the rest of the world. That was followed by a bunch of warnings indicating that maintenance had expired, i.e. under the educational license (which expires next month and will need to be renewed) I'm on my own.

I tried building a test scenario, including a few things I thought I'd need. IP, Cisco stuff, TDMA... nothing fancy. I've spent the last six hours staring at a 'Please Wait' dialogue (sorry, dialog) alternating between 'Validating Demand Self-Description Database' and 'Validating Node Self-Description Database' while beeping. Eventually, I figured out how to disable the beep in the parent terminal.

Somehow, I don't think I'll be using Opnet Modeler for anything much, much less using Opnet Modeler for anything useful. So it's back to open-source ns; better the devil you know.

Update: It finally died after seven or so hours:


<<< Program Fault >>>


* Time: 17:58:16 Wed Jun 9 2010 * Product: modeler (32-bit) * Function: mmi_msg_tip_show_handler * Error: program abort -- segmentation violation

That's nice.

Update 2: Turns out the modeler binaries don't get along with Ubuntu 9, but are better behaved on Fedora Core. Shame we're switching to Ubuntu, really. The clue was that MIL3 supports Red Hat. Linux binary compatibility? Ha.

29 May 2010 (updated 29 May 2010 at 22:47 UTC) »

Wired goes a bit CD-ROM

Wired Magazine have launched their latest issue as an iPad app costing US$4.99. It's large enough to require a CD-ROM to save a copy on.

The app will fill up 527 mb of your iPad storage space and takes approximately 10 minutes to download. [..] Here are a few issues I found within the app. First was the price. I’m sure I won’t be the only one complaining about the ridiculously high price per issue when you can easily buy a year’s worth of the printed copy for only $10. Also the file size is cause for concern. Not only is the app 527 mb too big, but it takes a long time to download and if you only paid for the 250 mb data plan for your 3G iPad, you’re just sheer out of luck.
-- WIRED Magazine for iPad review, Mary Ann Neder, IPADMODO, 28 May 2010.

You could fit a movie in that app filesize. Or the complete works of the Beatles.

all the fonts on the Wired app were rendered on a desktop platform, and provisioned to the app in the form of flat PNG files. The Wired app does not use the iPad’s rendering software at all.
-- Comment by Jonathan Hoefler to: WIRED on iPad: Just like a Paper Tiger… by Oliver Reichenstein.

Well, that's one reason why the app is so large. The other would be the included advertisements that you buy along with the app.

And how does screen reading or translation software work with flat PNG files?

it all seems a bit CD-ROM.
-- cd-roms and ipads, Danny O'Brien, former Wired journalist, Oblomovka, 1 April 2010.

(It's a pity for his comparison that the Wired app is only available through iTunes, and not included in a CD-ROM on the cover of the printed magazine as well.) How long will Wired's venture into e-publishing for a single platform last? Danny's musing on production costs and comparisons with CD-ROMs, and the demise of Wired UK the first time around suggests not very long at all.

M y opinion of Wired hasn't changed. It's still easier and cheaper to read their articles online with a web browser. Still, iPad early adopters are by definition Wired's target audience, explaining the claims of 24,000 app copies sold with the first edition of the app. There's a sucker docked every minute. Better hope they don't want continued access to back issues; two years' worth of issues this size will fill up the 16GB iPad.

Still, this publishing venture won't last that long in this form.

Apple's developer restrictions

Much fuss of late over Apple's changes to its iPad/iPhone developer agreement banning use of interpreters and translators. It's claimed to be all about preserving battery life and the user experience, or Apple's control of their manifest destiny, depending on who you read.

But what if it's also a way of encouraging use of Xcode and Macs, and (inadvertently?) promotes Xcode/Objective-C development on the Mac? Mandating that iPhone developers use Xcode and Objective-C leads to encouraging Objective-C for Mac development as a side-effect. It promotes not just iPhone/iPad expertise and iPhone/iPad-specific applications, but leads developers towards creating more feature-filled Mac-specific applications - rather than poor ports from Windows or from Unix/X (my SaVi satellite visualisation software is an example of the latter. It's suckily minimal-effort crossplatform.)

Shortterm, this restriction benefits the iPhone/iPad. Longterm, this may lead to compelling Macintosh-only applications; it's been a long time since there have been many of those.

But it's still all about Apple's control of its manifest destiny; no change there.

13 Apr 2010 (updated 13 Apr 2010 at 16:48 UTC) »
I blinked.

Although NTT DoCoMo removed some HTML tags, it also added some new ones. The <blink> tag makes text turn on and off.

-- Andrew S. Tanenbaum, Computer Networks, 4th edition, section 7.3, p. 669, Prentice Hall.

Louis J. Montulli II disagrees about the origins of <blink>, of course. And Tanenbaum follows that with an introduction to WAP.

It's entirely fair to say that the fourth edition of Computer Networks could be better, though it's perhaps not as poor as the third edition. I think the second edition provides a graceful introduction to the importance of networking layering, even if it is somewhat OSI-centric, and that it is much better for learning about fundamental principles of networking. The second edition is timeless. The fourth, not so much. But then it's trying to cover much more ground.

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