kern f

number one

According to Google I'm the most relevant 'Uwe Hoffmann' on the web. Hurry, go check it out before they rebuild the index and correct the mistake. If you go to scholar.google.com and search for 'codemanic' you'll see that Google thinks I'm a scholar too.

edge.org more cool answers

I have a couple more answers that I really like to the question "What do you believe is true even though you cannot prove it ?" given by edge.org to its contributors.

Ian McEwan (well said):

What I believe but cannot prove is that no part of my consciousness will survive my death. I exclude the fact that I will linger, fadingly, in the thoughts of others, or that aspects of my consciousness will survive in writing, or in the positioning of a planted tree or a dent in my old car. I suspect that many contributors to Edge will take this premise as a given—true but not significant. However, it divides the world crucially, and much damage has been done to thought as well as to persons, by those who are certain that there is a life, a better, more important life, elsewhere. That this span is brief, that consciousness is an accidental gift of blind processes, makes our existence all the more precious and our responsibilities for it all the more profound.

Charles Simonyi (his metaphor using cryptography made me laugh out loud even though it suffers a little from oversimplification):

I believe that we are writing software the wrong way. There are sound evolutionary reasons for why we are doing what we are doing—that we can call the "programming the problem in a computer language" paradigm, but the incredible success of Moore's law blinded us to being stuck in what is probably an evolutionary backwater
....

Leonard Susskind (funny):

Conversation With a Slow Student

Student: Hi Prof. I've got a problem. I decided to do a little probability experiment—you know, coin flipping—and check some of the stuff you taught us. But it didn't work.

Professor: Well I'm glad to hear that you're interested. What did you do?
.....

Freeman Dyson (clever jewel):

Since I am a mathematician, I give a precise answer to this question. Thanks to Kurt Gödel, we know that there are true mathematical statements that cannot be proved. But I want a little more than this. I want a statement that is true, unprovable, and simple enough to be understood by people who are not mathematicians. Here it is.

Numbers that are exact powers of two are 2, 4, 8, 16, 32, 64, 128 and so on. Numbers that are exact powers of five are 5, 25, 125, 625 and so on. Given any number such as 131072 (which happens to be a power of two), the reverse of it is 270131, with the same digits taken in the opposite order. Now my statement is: it never happens that the reverse of a power of two is a power of five.

The digits in a big power of two seem to occur in a random way without any regular pattern. If it ever happened that the reverse of a power of two was a power of five, this would be an unlikely accident, and the chance of it happening grows rapidly smaller as the numbers grow bigger. If we assume that the digits occur at random, then the chance of the accident happening for any power of two greater than a billion is less than one in a billion. It is easy to check that it does not happen for powers of two smaller than a billion. So the chance that it ever happens at all is less than one in a billion. That is why I believe the statement is true.

But the assumption that digits in a big power of two occur at random also implies that the statement is unprovable. Any proof of the statement would have to be based on some non-random property of the digits. The assumption of randomness means that the statement is true just because the odds are in its favor. It cannot be proved because there is no deep mathematical reason why it has to be true. (Note for experts: this argument does not work if we use powers of three instead of powers of five. In that case the statement is easy to prove because the reverse of a number divisible by three is also divisible by three. Divisibility by three happens to be a non-random property of the digits).

It is easy to find other examples of statements that are likely to be true but unprovable. The essential trick is to find an infinite sequence of events, each of which might happen by accident, but with a small total probability for even one of them happening. Then the statement that none of the events ever happens is probably true but cannot be proved.

make plans and take pictures

Edge.org gave the following question to its contributors:

What do you believe is true even though you cannot prove it ?

They collected 120 answers, a very diverse and interesting read. My favorite answer so far is from Kai Krause stating he believes that the "Vorfreude" for an experience or a moment and the memory afterwards of that experience/moment is more enjoyable than the experience/moment itself.

Nothing ever is as beautiful as its abstraction through the rose-colored glasses of anticipation...The toddlers hope for Santa Claus on Christmas eve turns out to be a fat guy with a fashion issue. Waiting for the first kiss can give you waves of emotional shivers up your spine, but when it then actually happens, it's a bunch of molecules colliding, a bit of a mess, really. It is not the real moment that matters. In Anticipation the moment will be glorified by innocence, not knowing yet. In Remembrance the moment will be sanctified by memory filters, not knowing any more.

His advice:

Bluntly put: spend your life in the eternal bliss of always having something to hope for, something to wait for, plans not realized, dreams not come true.... Make sure you have new points on the horizon, that you purposely create. And at the same time, relive your memories, uphold and cherish them, keep them alive and share them, talk about them. Make plans and take pictures.

An interesting twist on this is something I believe is also true (and I cannot prove): the anticipation of the everyday routines of dealing with life's mere mechanics creates procrastinators (like me, I'm speaking from experience here).

Holiday season comes and

Holiday season comes and houses in my neighborhood undergo a light transformation.

Clear winner this year:

Watch out, Vegas!

pro cycling tour in sf

The US Pro Cycling tour descended on SF today for one of the toughest races on the tour, the course actually goes up on Fillmore Street. We watched on Embarcadero in front of the Ferry Building near the start and finish line. Here's pictures (some heavily cropped).

singularity

A couple of days ago slashdot had an article with a link to a short story by Vernor Vinge. I read the story and I liked it. Having never heard of Vernor Vinge before, I got curious and I googled him.

His paper about a technological singularity is interesting and thought-provoking. It is now more than ten years old. I think we can say for sure that one part of his prediction is correct: the singularity won't happen before 2005. The upper bound of 2030 for its arrival sounds very ambitious. From my point of view as an outsider and observer of the field of AI it looks like progress is slow and the problems to solve really hard.

That's not to say that it won't happen. Eventually (in the far more distant future) we will get there.

Quote:

Shortly after, the human era will be ended.

I don't know about that. If we learn how to build a superhuman intelligence we probably learn enough about thinking and mind processes that we can build in emotions ("rules") that let it coexist with us. Maybe we could build parent-child emotions into it, after all humans would be the parents of that little monster. Or we could build in cuteness feelings, humans could become the Pandas of the superhuman world, regarded as cute and worth protecting by the superhuman intelligence. In a way that would make for a much funnier plot than what I'm afraid "I, Robot" the movie will serve us.

golf cart parade

We spent the Fourth of July on Catalina Island, a mediterranean paradise off the coast of Los Angeles, about an hour away with a ferry from Long Beach. There are very few cars on the island, everybody uses golf carts, so the Fourth of July parade was a parade of golf carts.

Here are some snapshots.

where to start with a startup

Two really inspirational papers hit the web the last couple of weeks:

Cory Doctorow's Microsoft Research DRM talk

and

Tim O'Reilly's Open Source Paradigm Shift.

Both authors are astute observers of the technology world and both present in these papers interesting and compelling new ways to look at certain aspects of this industry.

What I realized reading them was that both papers are basically guides to discover new business opportunities. So if you want to do a startup but you don't have any ideas yet, these papers can help you find an orientation in the space.

Cory: "If thou build product without DRM then users will flock to you."

Tim: "If thou know the three C's thou will be successful."

comments are open again

I upgraded this blog to Movable Type 3.0D and turned comments back on. They were off for a long time after a spammer polluted most of my entries. To prevent this from happening again I require a registration with TypeKey. If this is too much trouble you can also send your comments to blog at this domain.

garageband

I bought iLife 04 the other day and started experimenting with Garageband. It is a fascinating app. I have zero musical education and still, sitting in front of it, fiddling around with loops made me feel that maybe I can come up with something halfway decent.

But really, what is the probability that I will hit it big ? Come up with the next great sound ?

Honestly I think Apple is secretly using us musical amateurs for a great scientific experiment: the musical version of the Monkey Shakespeare Simulator.

Maybe GarageBand should be renamed to MobyMonkey.

On the other hand, there are differences. The monkeys only get a typewriter. This does restrict their output to valid characters and prevents random scribblings on paper. But it doesn't even constrain the monkey output to valid English words. Would the probability of Shakespearian text emerging increase with such a constraint ?

GarageBand is actually very clever. It has intelligence built into it that lets it sync up loops that I almost randomly throw at it and makes them work together (of course within limits, nothing it can do about "Rural Banjo" and "Emotional Piano 01" thrown together). It has constraints and smarts that maybe increase the probability for that chart-topping sound.

Sorry, gotta go. More fiddling and further investigations are needed. Monkey business. That nice gentleman in the white lab coat with an Apple logo on it is feeding me another banana.

pink house

This entry falls in the "I got nothing smart or useful to say so I post something silly" category.

Here's a house in our neighborhood with a unique color choice:

eurobeat

On the flight back from Europe I was flipping through the audio channels and I got hooked on some eurobeat tracks. In fact I liked them so much that later I went hunting for them in the iTunes Music Store:

tunnel - dining rooms

la citta nuda - dining rooms

afterwards@the bar - caia

magic love - bent

so long without you - bent

blue monday - flunk

moonbeams - bent

chagall

We went to see the Marc Chagall Exhibit at SF Moma today. The guy is good, I really like him. You can tell he enjoyed his life, he enjoyed being married, he enjoyed being with his wife. He liked the circus, parties and celebrations. His paintings have a very distinct style, escaping the trap of too much abstraction, making them accessible to people like me.

The collection is unique, it's the first time so many of his paintings are together in an exhibition and it will end Nov. 4th. I recommend buying the tickets online to avoid long lines.

apple rocks

Apple never ceases to amaze me. They just "get" things, they know how to do it right. iTunes and the iTunes Music Store are the latest example. One cool thing with the second generation of the Store is that music becomes addressable. You can refer to it by URL just like books became addressable when Amazon showed up.

Try for example "First Cool Hive" by Moby

When you drag a song from iTMS into a text area you get its URL and you can also use iTunes link maker to make more sophisticated links that do the smart thing when iTunes is not present.

what's in a name

Maybe it is time to explain the title "kern f" of this blog. I found a great article yesterday describing the attitude of being "enamored with the abstract notion of math and science". I am definitely on the lightweight side of the equation.

You encounter kern f pretty early on if you read any algebra textbook. For group homomorphisms for example it's the subgroup of elements in the domain group that map to the unit element in the image group. It has all sorts of interesting properties, for one thing it is a normal subgroup. And conversely for every normal subgroup of a group there is a group homomorphism for which the subgroup is the kern of that morphism. The factor group built with kern f is isomorph to im f.

So what does this have to do with blogging ? Well, when you create a new blog in mt it asks you for a title and there's this blank textfield staring at you. It's not easy to come up with something cool. The Fishbowl blog for example has this geeky cool subtitle "tail -f /dev/mind > blog". kern f is not in that class but is something. You might be tempted to interpret some metaphor for it like this blog maps ideas to the unit element of publishing or somesuch. Ah, that's up to you. For me it was just this algebra book open on my desk (remember I'm "enamored with the abstract notion of math and science") when mt asked for a title.

Oh, the book btw is this:

"Algebra" by Serge Lang.

cleanup

I realized I have this "Currently Reading" sidebar section and I'm not making much progress on the book I listed there so I took that sidebar section down. The book is

"Prime Obsession: Bernhard Riemann & the Greatest Unsolved Problem" by John Derbyshire,

in case anyone is interested.

It's still a great book but I have other reading interests right now. I'll pick it up later again. I understand now that it's less pressure for me to finish a book if I mention it in a blog entry than it is if I make it a sidebar section "Currently Reading" fixture. Such are the lessons of a lazy reader.

back

A whole month has passed since my last entry. I guess I was Spirited Away (had to sneak this link in, just watched the movie last night and it was magical, can't wait to watch it again tonight). It so happened that during my silence a lot of math/cs problems and puzzles have piled up on my desk so with some luck I will be more active in the next weeks. Most of the problems came from the unlikely fact that our group at work got an open req suddenly and we had to do interviews. Boy were we rusty. We haven't had an open req forever. But it lead to us talking about interviews (btw a good discussion on the web about interviews is here) and what questions to ask. This lead to cs puzzles and then to problems which some of the group members knew and liked (not exactly suited for 1-hour interviews though).

So here are the problems:

1.) Prison cells. A prison has n cells with all cell doors shut initially. The warden is a little weird so he walks the whole row of cells and opens every cell door. Then he walks the whole row again and shuts every other cell door. Then he walks the whole row again and opens every third door then walks the row again and shuts every 4th door etc. You can assume that the doors are numbered 0 to (n - 1) and the warden always starts at 0 and walks them in order. Which doors will stay open when the warden is done ?

2.) 2D bitmask. Given a n x n grid of 0's and 1's find the largest square within the grid that only contains 0's.

3.) 2D grid of integers. Given a n x n grid of integers (not all positive) find the rectangle within the grid with the largest sum.

4.) S and P. Of two unknown integer numbers in the range [2..99] inclusive a person P is told the product and a person S is told the sum. When asked whether they know the numbers, the following dialogue takes place:
P: "I don't know them."
S: "I already knew that."
P: "Then I now know the numbers."
S: "Then I now know them too."
The problem is to determine the two numbers from the above data and to prove that the solution is unique. (this problem is note EWD666 from the delightful website EWD)

5.) Repetition. Given a sequence of comparable items (let's say characters) calculate the maximum number of consecutive equal subsequences (of any length). Consecutive means that when one subsequence ends the next one starts. Example: sequence abababbb has consecutive equal subsequences of length 2 ab ab ab, has consecutive subsequences of length 1 b b b etc.

I'm going to do the usual thing: try solving them and keep you posted in this blog about my progress then do a write-up in TeX for the ones I successfully solved.

witches curse

Watched a fascinating documentary on PBS last night: The Witches Curse. Researcher Linnda Caporael discovered a plausible reason for the terrible witch hunts in the middle ages that killed 40,000 innocent people: a fungus that infected the grain crops and caused food poisoning and LSD-like symptoms.

fort funston

walked by this car parked at fort funston. look at the spare tire holder

introduction

Looks like movable types needs more than one entry for me to test the looks of the blog. I might as well start by introducing myself as this seems like a polite thing to do.

I'm in my thirties, happily married, living near San Francisco, almost with ocean view. I'm originally from Germany, studied computer science there and now I earn a living in a big software company in the Bay Area. I'm a decent basketball player and a walking NBA dictionary.

I just started this blog because I hope blogging will force me into more discipline and will help me make progress with the things I like to accomplish in my spare time. The lofty goal is to slowly re-read the math and cs courses from college I long ago have forgotten. Along the way I also want to pick up Haskell. I'm a recovering Java Junkie and I feel I need a new mindset, an intellectual change of scenery.

first entry

This is the obligatory test entry. I just installed mt and it seems like the css style I chose needs an entry to display the things correctly.