This page is for various odds and ends, and will be updated periodically...
The Rudeness Index
In large races, runners should line up according to pace: faster runners up front, and slower runners in the back. This common-sense etiquette is far less common than it should be. I analyze the results from a ~2500 participant race in Austin, develop metrics for quantifying how much one violates this etiquette, and do some simple statistical analysis with demographics. Analysis here.
(If you know of a shorter path, another disjoint path, or a particularly interesting path, let me know!)
Here is my academic genealogy, as far back as I can trace it. While Charles Keese led a distinguished career in transportation, I have not yet been able to find out if he held a doctoral degree, and if so from what institution.
Equilibrium: A Sam Walters Story
I wrote this as a prologue and epilogue to a group project when I was a graduate student. I must admit that I was inspired by Bruce Hoppe's brilliant story that bookends his dissertation, and a fit of procrastination. A few names have been changed to protect the innocent.
You've heard the proverbs. "Carpe diem." "Strike while the iron is hot." "Opportunity doesn't knock twice." Well, I've heard them too but I'm just now starting to understand them. I had a chance to save the city, but exchanged it all for loyalty to a woman I hardly knew. I still don't know if I made the right choice, and that's what makes it impossible for me to forgive myself. It all started last night, after the slowest day I'd seen in weeks.
The sounds of a light drizzle filled my office with a dull chatter. From time to time drops of rain would leave streaks across my window, crisscrossing into a mosaic of droplets as the hours passed. Frustrated, I rolled my chair over to the window and gazed onto the street five stories below, lit only by the light of a pale October moon and a flickering streetlight. It was late and the day had been slow, but I had worked this business for years, and I knew I'd get a client before long. It was just that type of day. Oh, I suppose I haven't introduced myself yet. My apologies, I never was much of a gentleman.
My name is Walters, Sam Walters, and I'm a private eye.
Chicago's where I do my work, and 1931 is no easy year to do it in. These days you really have to watch yourself in this town, what between the speakeasies and bordellos that fund the massive crime syndicates. Prohibition be damned, I thought to myself as I took a swig of bourbon.
Thankfully I have three of the best assistants a private eye could ask for, and we get by. Like I said, my name's Sam. My pal Samrat -- I know our names are similar, spare the jokes, we've heard them all -- could get information out of anybody, and was one of the sneakiest people I knew. Except for his roommate, that is. Steve helped me on the forensics end, and Shashank was the muscle of the operation. He had two helpers of his own, Mr. Right Hook and Doc Haymaker, and those who had the pleasure of meeting them never forgot. What a team, I thought, as I stared at the street below and took another drink.
Before long, a rap at the door broke me out of my reverie.
I opened the door and a young woman stepped in. If Helen's face launched a thousand ships, this dame's eyes alone could sink the whole German navy. She was the kind of girl whose picture you could find in the dictionary, right next to "femme fatale." I introduced myself, and she said she needed help.
Boy, was she a looker. She told me her name was Elisabeth -- Elisabeth McDaniels -- and she made sure I knew it was 'Elisabeth' spelled with an 's.' However, I've been in the game a long time, and the only thing her name spelled to me was trouble. Her face was steady, but inside I could tell she was a wreck. The look in her eyes told me it was murder, but I was wrong: it was network theory.
"Tell me, Sam... if I may. When I perform user equilibrium traffic assignment, what really are the differences between MSA and Frank-Wolfe? Practically speaking, I mean. And how does network size affect it all? I'm scared, I need answers soon!"
She was getting hysterical. "Oh, I don't know why I got into this! I... I couldn't pay the rent one month... and this man offered me some money to answer these questions... and I... I just didn't know what to do! Now he's threatening me... and... oh, how was I supposed to know he worked for Montefiore?"
Montefiore. I should have known. At that name my blood ran cold, about as cold as the tuna sandwich in my desk was getting. Yes, I like my tuna sandwiches warm, but my wife tells me that's unusual. His gang was ruthlessly efficient, and they had their paws in more areas of network theory than you could count on both hands and a couple of toes. If you crossed them, chances are you didn't live long enough to tell too many others about it. Right then I swore Elisabeth would be the exception to that rule.
I asked if she felt safe tonight, and she answered that she had rented a room in the Hotel Salinas, two blocks north. She waved goodbye, and I told her to come back in the morning.
My mind was reeling so fast you'd think it was a movie projector, but the only pictures moving here were the mug shots in the dossiers I was shuffling through. What are the real differences between MSA and Frank-Wolfe? And what's this whole user equilibrium thing anyway? I set to work, calling my buddies at the universities, Dantzig, Dijkstra, Wardrop, the usual suspects, but they just laughed. "You can't expect us to answer that overnight! Call us back in a decade or two, maybe we'll have some answers for you then!"
I gritted my teeth as I slammed down the phone in frustration. Even if they couldn't handle it, I knew my assistants and I could. "Let's go, boys," I called. "We've got ourselves a case to solve."
I donned my trench coat and fedora, and headed out into the rain.
The four of us trudged through the streets. I wasn't exactly sure where we were going, but the other night Samrat got a hot tip about a Montefiore hangout from Snake Eyes Malone. Snake Eyes Malone was the kind of guy who tried to have it both ways, working in the mob for the graft and spilling his guts to the cops often enough that they gave him clemency as an informant. He had no master but himself, and I doubt there was a loyal bone in his body. I trusted him about as much as a share in the Brooklyn Bridge, but we had nothing better to go on.
After an eternity of walking we reached the joint, the dime-a-dozen kind of speakeasy that seems to fill every corner of this town. It was crowded inside, but we made our way to the booths at the back, where junior members of Montefiore's gang passed the nights away. None of my boys saw anything out of the ordinary, so we decided to grab a drink and wait for something to come up. At that moment a hand grabbed my shoulder.
"Well, look what we have here."
It was Muggsy Nelson, one of Montefiore's lieutenants. I've dealt with him before, but he was the type who liked to do the dealing himself, and was feeling generous if he let you shuffle beforehand.
"Sam, Shashank, Samrat, and Steve -- all four of you here together. How cute. Your names go together well. Now go form an ice show or something and get out of here."
Ice show? That gave us all we needed to know, so Shashank introduced him to Mr. Left Cross and we got out of there in a hurry. Without speaking a word to each other, we knew where we had to go.
Twenty minutes later we were outside the abandoned skating rink. It was padlocked but I haven't seen a lock yet that Samrat couldn't pick. I heard a low hum from down the hallway, so we decided to check it out. At the end of the corridor a light shone from behind a door, casting long shadows along the wall. Shashank and Samrat entered first, and Steve and I followed after they motioned that it was clear.
The room was filled with wires and tubes that crackled with electricity. At the other end of the room were reams of paper that had been spit out of this mechanical monstrosity.
We walked over to the stacks of paper and riffled through them, trying to find something of use. I stopped when I found information on the gang's organization. It was all here: names, operations, enough dirt to put Montefiore out of business -- permanently. Shashank came across pages and pages filled with numbers and times, apparently the results of performing user equilibrium traffic assignment: exactly what we needed to save Elisabeth. Unfortunately we couldn't take it all back with us, and once Montefiore discovered our break-in he'd move his headquarters and we'd lose this lead.
So that was my moment of decision: take my stack of documents back and topple Montefiore, or take Shashank's pile and save Elisabeth. It was a pretty pickle, and as much as I wanted to rid Chicago of its greatest threat, I couldn't get Elisabeth's face out of my mind. I couldn't bear the thought of breaking my word to her. Steve murmured something under his breath about the knapsack problem and NP-completeness but I told him to shut up.
I made my decision, and we returned to the office with the traffic assignment results. Shashank and Steve spent the night poring over them, distilling them to the essence that Elisabeth needed, while Samrat typed up a summary for her.
Meanwhile I sat at my window, staring at the street below, contemplating what I had done. I didn't sleep that night. The next morning my secretary told me I looked awful, and she was right. Elisabeth came by right after Shashank left on a flight for India, and right then I wished I could fly away with him. Facing her would only remind me of my choice.
But nothing out of the ordinary happened. It was all by the book. I gave her the summary, she thanked me and paid me. My face never betrayed the price I paid to save her, or at least I hope it didn't. And that was that. She left, and I never heard a word from her again.
It was another slow day, leaving me nothing to do but think, but sure enough by nightfall another dame came by. Something about a life insurance claim, but I knew she was a phony from the moment she opened her mouth. She wanted me to help give her some answers, but all I'd help her get is twenty to life in the slammer.
After she left, I smiled, knowing that Sam Walters would get the job done. I put last night behind me -- hopefully for good -- and once again I stepped out into the night.
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