Ben FrantzDale

iPhone time

2009-12-05T04:45:33Z

So after a long saga with Sprint became the final ~~straw~~ haycart (including someone hijacking my account, me notifying Sprint within an hour of that, hours on the phone that Friday instead of a nice dinner out, a bill for over $5,000 of calls to Cuba, all but a few dollars of which happened after my first call to them, them disconnecting my phone without telling me (they told me by leaving a voicemail I could have listened to if they hadn't disconnected my phone), calling them and manually resetting the phone's unique ID, then actually getting the bill for over $5,000, then asking them if I had to pay it, then being told that my account has been credited, but they just wait on their lazy asses and send out $5,500+ bills for the fun of it and wait for the customer to get in touch with them, then realizing that they credited the long distance, but not the US airtime, leaving $45 more unaccounted for, then my sprint.com account got disconnected from my phone account, then when I fixed that I couldn't download the bill PDF 'cause I couldn't find the link, then finding a help entry for downloading the PDF of the bill, but then the instructions didn't agree with the actual page, then having the dude on the phone not be able to help with the PDF download, then having him not understand that me adding up my valid daytime minutes that aren't to Cuba gives me 200-something which is a lot less than my 450-minute plan and also a lot less than the 700 they wanted me to pay for, him getting confused, then throwing up his hands and just crediting me the $45 I was asking for because I was a loyal customer), it's time to switch.

Two questions:

16GB at $200 or 32GB at $300?
What's the process for transfering a phone number? Does it Just Work or is it one of those pain-in-the-ass media-company interactions?

warning: comparison between signed and unsigned integer expressions

2009-11-17T17:43:49Z

Dear Lazyweb,

Philosophically, why is it a warning to test equality between signed and unsigned integer expressions in C++? Is it a performance issue (i.e., u==i would become bitwise_equal(u, i) && i >= 0)? Is it just that it thinks mixing signedness is a bad idea?

VS Update

2009-11-10T12:06:29Z

Previously I mentioned that Mudders had fun putting Mudd at #1 on VSPink.com, followed by spelling WIBSTER (loosely the Mudd equivalent of IHTFP). If you go there now, the top 25 no longer contains any Ws. It does, however, spell: Harvey Mudd rocks boo Cal Tech. (Using Cal Tech as the C, no less).

While it seems a little less than first-rate to keep perpetuating a one-sided rivalry, that is pretty cool.

B Movies

2009-11-01T02:47:55Z

Speaking of B movies, we watched Runaway could have been better, despite all it had going for it: Tom Selleck, Gene Simmons, robots, Tom Selleck's moustache, Gene Simmons's tongue (which got very little screen time). It was interesting to see the future as seen from 1984, complete with CRTs, analog video, huge telephones, and robots that fly and cook you dinner.

Where's my dinner-cooking robot? Stupid AI-complete problems.

WIBSTR

2009-10-16T01:47:55Z

Mudders not only stuff Victoria's proverbial ballot box, they also made slots 2–7 spell WIBSTR (it's a Mudd thing described in the following article). Awesome.

Harvey Mudd 1, Victoria's Secret 0.

Also blogged here.

Fabulous Furniture

2009-10-14T11:18:18Z

This weekend's trip to the Catskills included a trip to Steve Heller's Fabulous Furniture. He has a thing for using '50s car parts in furniture, lighting, and sculpture. We came home with this lamp, which he appears to have beamed down from the future:

The conical light is a '59 Cadillac tail light; above that is a '65 Buick Riviera hub cap center. Points for who can guess where the plastic dome came from.

iPhone? GPhone? otherPhone?

2009-10-03T16:43:39Z

We are starting to consider phones. The iPhone and Google Phone are in the running... thoughts?

References for Statistics on Manifolds and such?

2009-10-02T02:12:27Z

For work and for fun, I've started thinking hard about statistics in non-Euclidean spaces. For example, how do you average angles or find the MLE of a point in SE(3)ⁿ given a collection of relative rigid-body transformations or a generalized median of several homographies?

I've found some interesting papers, but no great references... do you have any recommendations? I'd like to know more about Remannian geometry, to understand affine connections, and statistics in these spaces. Any book references would be appreciated.

Yay math!

Roof painting: Good advertizing in the days of barnstorming and of Google Maps

2009-09-24T11:33:39Z

While looking for a Qdoba, I discovered where a possibly convenient Target is.

View Larger Map

Traffic and Pricing

2009-08-20T11:44:34Z

Great quote from Traffic by Tom Vanderbilt:

When Costco discounts televisions during its Christmas shopping promotions, pricing them so low that stores do not make a profit, what happens? There are huge lines at the door at five a.m. When cities provide roads that are priced so low that they lose money on them, what happens? There are huge lines on the highway at five a.m.

Fun with infoviz

2009-08-14T02:25:11Z

NY Times infoviz on how people spend their days

As featured at Black Hat

2009-08-01T23:40:04Z

Thanks to jldugger for pointing me to K. Chen's Black Hat presentation, Reversing and Exploiting
an Apple Firmware Update, which made use of (and cited) my Creative-Commons-licensed pictures of the insides of an Apple slim keybaord.

I thought taking clear pictures of the chips would be useful to the world. They mean nothing to me, but the presentation at least describes what many of them are and what they do.

Total derivatives and spring systems

2009-07-29T04:06:55Z

My wife is at a conference, so my mind turns to... linear algebra.

Suppose you have a spring system... like a horizontal yardstick bolted to the table at one end, flat side facing the table (not standing on edge). You can move the tip up and down and it will resist, springing back into place. You can also bend it horizontally, but it's much stiffer in that direction due to its shape. (For the sake of simplicity, let's give each element two degrees of freedom—no crazy axial motion or buckling or twisting modes; this is a toy example.)

Suppose I'm curious what happens to the shape of the yardstick when I move the end in either of those directions. This winds up being a differential equation and you can solve for it numerically or using FEA.

I'm interested in better understanding the FEA part of it. Considering just the tip of the yardstick, and assuming small deflection (so assuming no geometric nonlinearity), I expect the restoring force to be proportional to the displacement of the tip, and so

f=−Kx

where f is the restoring force, K is the spring constant (a 2×2 matrix), and x is a 2×1 vector describing the horizontal and vertical displacement of that tip. Similarly the energy would be

u=½ x^TKx

Now, FEA can give me a system stiffness matrix, a matrix relating the forces to the displacements of every little piece of the yardstick. That's all well and good, but how do we go from that to the 2×2 black box system matrix describing the displacement of the tip only?

My feeling is that it works like this: Intuitively, if you push the end of the yardstick up, it'll go up, and the rest of the yardstick will go along with it in what is clearly the first bending mode (the eigenmode of K corresponding to the smallest nonzero eigenvalue). Similarly if you push it horizontally, it'll move that way (and not deflect up). This is the second eigenmode. So if we want to know what happens to the shape when we push the end around, it looks like we just want to find enough low-eigenvalue eigenmodes to span the space we want to explore (tip goes up or down, tip goes side-to-side), then fit those to the prescribed deflection.

If that's right, I'm not sure exactly what basis make sense. If we eigendecompose the K for the full system so you have

VDV^T=K

with the eigenvalues in ascending order, then can we could just say we'll use the first n eigenvectors with nonzero eigenvalues. But what if those don't span the space in which we are interested? Unless we have repeated eigenvalues (let's assume we don't), we could just keep adding eigenvectors until we do span the space, but if we wind up with more than n eigenvectors then we don't have a unique solution. On the other hand, the only other thing I can think of is to build a basis by adding eigenvectors in increasing order, but skipping those that aren't linearly independent within the space of prescribed degrees of freedom. That seems most likely, but also seems totally kludgy.

So...

What's the right way to do it?
Is there an elegant way to solve this that I'm just missing
Can you describe this black boxing as finding a total derivative of the system energy with respect to the degrees of freedom you want to prescribe, constrained by minimum system energy?

3D Fetuses!

2009-07-24T02:11:58Z

Back when our nephiews were in utero about 15 months ago or more, we asked their parents to get the data set from the 3D ultrasound so we could have it 3D printed. But noo.... the ultrasound tech didn't understand what they asked for and just gave 2D pictures from the 3D ultrasound.

Apparently now, 15 months later, someone has gone and done this.

Tensegrity Cake (Patent Pending)

2009-07-16T05:21:07Z

The design criterion for our cake was that it be taller than the bride. At seven tiers and 5'7", it was. Using precision-engineering principles, it is remarkably sturdy and goes together without adhesives or complex locking mechanisms: it uses only kinematic couplings to connect the 39 ends of the 21 copper tubes to the 13 sides of the 7 tiers of cake.

The design could be used to produce cakes with more-conventional pillars, but why?

If you are interested in licensing, contact me.

[More photos]

Photo: Pamela Helme; fisheye added by the groom

Photo: Joanne Clapp Fullagar

Photo sequence: Joanne Clapp Fullagar

RIP WBCN

2009-07-16T04:02:34Z

It appears that the station that introduced me to the music of my generation, WBCN, is closing its doors. I guess WAAF wins after all these years.

Sure I rarely listened to them because they always have stupid drive-time jocks yapping, so my commute is dominated by WBUR (NPR), and sure if I did get music it was from WAAF because they have a commercial-free music-only evening commute, but still, 'BCN... wow. I'm officially recessed.

jpg2mpg howto

2009-07-08T10:47:47Z

After much fumbling, I figured out how to convert a pile of JPGs into a video. The magic line was this:

convert -delay 20 -resize 800x600 IMG_{1840..1922}.JPG ~/foo.mpg

where -delay is a number in centiseconds (so 20 is 5 fps).

The thing is, Ubuntu's install of ImageMagic (which provides convert) doesn't come with mpeg2encode, which is what it uses to make mpg files. I had to do this:

$ wget ftp://ftp.mpegtv.com/pub/mpeg/mssg/mpeg2vidcodec_v12.tar.gz
$ tar xvzf mpeg2vidcodec_v12.tar.gz
$ cd mpeg2
$ make
$ cd mpeg2enc
$ sudo cp mpeg2encode /usr/bin

Then convert it worked happily.

Communal storage and backup

2009-07-07T00:53:51Z

mew0422 and I are trying to sort out our data-storage needs. She has a laptop, I have a desktop. We want some NAS and we want a good backup solution.

It looks like Apple's Time Machine is entirely client-based and so can use any mountable storage, be it a Time Capsule, a USB HDD, or something else.

With that in mind, it seems like we'd be best to get non-Apple NAS—something upgradable and it shouldn't need to be a Wi-Fi server itself. (Recommendations?)

Here's what I'm thinking: I am inclined to use the JWZ Backup Solution for my computer, possibly rsyncing to NAS in addition to swappable drives. mew0422 would use Time Capsule to backup to the NAS box.

The only thing left is how to back up the NAS drive (financial files, shared media, etc.) Any thoughts?

I hate IT.

Capstan Table

2009-07-06T01:19:42Z

From the We should have put it on the registry department. The DB Fletcher Capstan Table:

Ascot!

2009-05-17T01:19:53Z

After a Quixotic goose chase involving many many mensware stores, I finally found someone who sells ascots in person! (Had it gone on much longer, the quest may have needed an ascot mascot.) After asking but finding none at JoS. A. Bank, I was directed to a place called SYMS which is kind of like a wearhouse-sized T.J. Maxx focusing on dress clothes.

Also in this search I found Porta Classica of 1625 Blue Hill Ave. Matapan (no website). If you live in the greater Boston area and want an awesome zoot suit, that's the place to go.

Natural Feet

2009-05-08T01:16:56Z

I've been aware of Vibram Five Fingers Shoes for a little while (thanks to istar and others). I haven't tried them.

Tim Ferris had a very interesting post on the topic which cites a 1905 journal article about what natural human feet aught to look like:

as opposed to

Interesting.

MPI & Python

2009-04-14T01:46:47Z

Dear Lazyweb,

There appear to be more than a few MPI bindings for Python. Which should I use?

In particular, which should I use if I want to use Python to call C++ code that needs to take an MPI_Comm object?

Do any of you have any other experience with using Python with MPI? As one new to Python, I am particularly curious how garbage collection might interact with MPI if you have an object shared across computers.

Matlab is dead. Long live Python

2009-03-31T01:04:21Z

Over the past year and a half I've incorporated Matlab into my daily work. It's a tremendously useful tool for experimenting with image processing and linear algebra. It's got a nice array-slicing syntax, so the second column of a matrix, M is M(:,2), and every other row in reverse order is M(end:-2:1,:). It also has some very useful easy graphing commands, so if you have an array of values sampled at a corresponding array of x and y positions, you can say surf(x,y,A) and get a nice 3D surface plot. It also has other nice language features like the ability to return a list of results from a function and assign those results separately as in [V,D]=eig(A).

However, it's got some serious serious shortcomings. First, it's closed source and expensive, so if you prototype with it, you have to then either port it to another language or kludge together scripts to call Matlab—not cool. Second, unlike any language other than assembly, values returned from functions are magic in that you can't index into them. So while the function eig(A) returns a vector of eigenvalues of A, if you want just the first one, you can do v = eig(A); v = v(1) but you can't do v=eig(A)(1). This is particularly tiresome with a language geared for matrices in which you might want to nest a series of functions indexing each as you go. That is, you couldn't do foo(bar(baz(A)(1:2:end))(:,:,0)), you'd have to assign each result to a temporary. Third, Matlab indexes from 1. Yes that's what everyone expects when they start programming, yes mathematicians index from one, but for twiddling with arrays, zero is just easier.

Finally, Matlab doesn't lend itself to creating functions or data structures. In general each function is in exactly one file, leading to terrible code reuse. You can add more functions to the end of a file but those can only (?) be used as subroutines within that file, leading to a terrible lack of code reuse. Worse, what little support Matlab has for classes is done through a special directory for the class and a separate file for each method(!)

Fundamentally, there is a need for an interpreted language capable of being run interactively but that is also a real standard programming language, not some kludgy interpreted dialect of Fortran. That something needs to have mathematical and graphing batteries included.

Fortunately, there is a collection of Python packages that have a very solid chunk of this covered: matplotlib, scipy, and ipython. Not only do they have all of the 2D graphing that Matlab has with a similar syntax, but they use the (awesome) Anti-Grain Geometry library for graphing, so you get plots way better than the aliased 1990s-style plots that Matlab dumps out.

Python has language support for array slicing and for returning tuples, but it is also a Real Programming Language in that you can write a linked list or a graph without having to hack it on top of arrays. It isn't designed with array programming in mind the way Matlab was, so the syntax for arrays is slightly more cluttered, but not by much. The big differences being that Matlab has special element-wise operators and has concise array construction notation, so a.*b in Matlab returns the array formed by multiplying a(i) by b(i).

So give it a try. Install the appropriate packages and start doing your scientific computing in an actual programming language.


ben@endash:~$ ipython -pylab
...
In [1]: x=r_[0:100:0.1] # Generate [0, 0.1, 0.2, ..., 99.9]
In [2]: plot(x, sin(x)/x) # Nice pretty plot.
Out[2]: [<matplotlib.lines.line2d object="object"

at="at" 0xa0ee8cc="0xa0ee8cc">]
In [3]:

Can Matlab rasterize images to look this nice?:

PS
If you want a blast from the past, Python even has a turtle library, giving it the same drawing sematics as Logo.

from turtle import Turtle
t = Turtle()
for in in (0,1,2,3):
    t.forward(100)
    t.right(90)

Not only is Python making programming as fun as it was in my hard-core Logo days, it's doing it in a language that can simultaneously be used for Logo-like simplicity and Matlab and driving high-performance computing. Go Python!

φ!

2009-03-16T23:51:48Z

So I stumbled upon this useful page: list of strange units of measurement and learned a very interesting fact: One mile is within 0.5% of φ kilometers. The golden ratio is 1.61803399; a mile is 1.609344 kilometers. So if you ever forget how many km to a mile, that's a good way to remember (or conversely if you forget the golden ratio or forget the eigenvalues of [1 1; 1 0], but you remember the number of km in a mile, this could come in handy).

And as the above-linked page points out, similar useful facts, see mathematical coincidence for fun facts like π²=10 to within 1.3%, or that sin(666°) = cos(6·6·6°) = −φ/2, exactly(!)

Helvetica

2009-03-12T03:03:25Z

Fifty one years ago, Max Miedinger found the perfect sans-serif typeface, Helvetica. That claim is debatable, and there are certainly some very nice sans-serif faces that have come since then, but Helvetica has gotten a tremendous amount of mileage. Somehow over all those years it has managed to still look cool, hip, slick, and corporate while also being used on perfunctory signs like the NO SOLICITORS sign on the glass door of my apartment. That's a little uncanny.

I hadn't paid much attention to Helvetica until I watched the film about the font that came out recently.

One thing it got me thinking about is infinite-dimensional design optimization (like things do). The shapes of a font can be tweaked, so for any font there are other fonts in some neighborhood of it. Helvetica has horizontal terminals, so the ends of the C, S, s, 2, 3, and the tail of the e, g, etc., are all horizontal. The R has a gentle foot to it, and the t has a flat top and the G has an arrow shape to it. Similar fonts in the neighborhood of Helvetica don't have these features and that arguably makes them hold together less well and come off as less crisp. If you tried to improve such fonts, I suspect you'd get back to Helvetica, like some typographic local-energy minimum. If this weren't the case, then why would Helvetica have stuck so well for 50 years despite its apparent overuse? One person in the film suggested that the horizontal terminals gives the curvy letters a sense that they aren't going anywhere, that the C or the 3 won't spring open and that the R and G won't fall over or roll away. This seems very apt. In the table below, which version says the plane will get there safely, the cars will work, all while also saying the tape will stick, the notes will unstick, the taxes will be OK, and the chocolate-chip cookies will make you feel better? It's a lot for such a simple font, but subtleties go a long way.

For example, Arial (which has an interesting dubious history as a Helvetica knockoff) never quite looks right to me. From a design-optimization standpoint, it seems that Helvetica, with it's characteristic horizontal terminals just looks more solid. Compare various weights of Arial to various weights of Helvetica; one column is Helvetica, the other just looks wrong in some subtle knock-off sort of way.

The big C in Crate&Barrel is drawn slightly differently in their logo, so it's nearly a perfect circle.[cite]

On a typographical note, If you want to know what fonts people are using, try What The Font?. Send it a picture (or a URL for a picture) and it guesses the font. There's even an iPhone app.