TAC

A TAC game instance pits 8 autonomous bidding agents against one another. Each TAC agent is a simulated travel agent with 8 clients, each of whom would like to travel from TACtown to Boston and back again during a common 5-day period. Each client is characterized by a random set of preferences for the possible arrival and departure dates; hotel rooms (The Grand Hotel and Le Fleabag Inn); and entertainment tickets (symphony, theater, and baseball). To obtain utility for a client, an agent must construct a travel package for that client by purchasing airline tickets to and from TACtown and securing hotel reservations; it is possible to obtain additional utility by providing entertainment tickets as well. A TAC agent's score in a game instance is the difference between the sum of its clients' utilities for the packages they receive and the agent's total expenditure.

TAC agents buy flights, hotel rooms and entertainment tickets in different types of auctions. The TAC server, running at the University of Michigan, maintains the markets and sends price quotes to the agents. The agents connect over the Internet and send bids to the server that update the markets accordingly and execute transactions.

Each game instance lasts 15 minutes and includes a total of 28 auctions of 3 different types.

Flights (8 auctions):

There is a separate auction for each type of airline ticket: flights to Boston (inflights) on days 1-4 and flights from Boston (outflights) on days 2-5. There is an unlimited supply of airline tickets, and their ask price periodically increases or decreases randomly by from $\$0$ to $\$10$. In all cases, tickets are priced between $\$150$ and $\$600$. When the server receives a bid at or above the ask price, the transaction is cleared immediately at the ask price. No resale of airline tickets is allowed.

Hotel Rooms (8):

There are two different types of hotel rooms--the Boston Grand Hotel (BGH) and Le Fleabag Inn (LFI)--each of which has 16 rooms available on days 1-4. The rooms are sold in a 16th-price ascending (English) auction, meaning that for each of the 8 types of hotel rooms, the 16 highest bidders get the rooms at the 16th highest price. For example, if there are 15 bids for BGH on day 2 at $\$300$, 2 bids at $\$150$, and any number of lower bids, the rooms are sold for $\$150$ to the 15 high bidders plus one of the $\$150$ bidders (earliest received bid). The ask price is the current 16th-highest bid. Thus, agents have no knowledge of, for example, the current highest bid. New bids must be higher than the current ask price. No bid withdrawal and no resale is allowed. Transactions only clear when the auction closes. To prevent agents from all waiting until the end of the game to bid on hotel rooms, hotel auctions can close after an unspecified period (roughly one minute) of inactivity (no new bids received).

Entertainment Tickets (12):

Baseball, symphony, and theater tickets are each sold for days 1-4 in continuous double auctions. Here, agents can buy and sell tickets, with transactions clearing immediately when one agent places a buy bid at a price at least as high as another agent's sell price. Unlike the other auction types in which the goods are sold from a centralized stock, each agent starts with a random endowment of entertainment tickets. The prices sent to agents are the bid-ask spreads, i.e., the highest current bid price and the lowest current ask price (due to immediate clears, ask price is always greater than bid price). When a bid that beats the current bid (ask) price arrives, the sale price is the standing bid (ask) price, as opposed to the arriving ask (bid) price. In this case, bid withdrawal and ticket resale are both permitted.

In addition to unpredictable market prices, other sources of variability from game instance to game instance are the client profiles assigned to the agents and the random initial allotment of entertainment tickets. Each TAC agent has 8 clients with randomly assigned travel preferences. Clients have parameters for ideal arrival day, IAD (1-4); ideal departure day, IDD (2-5); grand hotel value, GHV ($\$50$-$\$150$); and entertainment values, EV ($\$0$-$\$200$) for each type of entertainment ticket.

The utility obtained by a client is determined by the travel package that it is given in combination with its preferences. To obtain a non-zero utility, the client must be assigned a feasible travel package consisting of an arrival day AD with the corresponding inflight, departure day DD with the corresponding outflight, and hotel rooms of the same type (BGH or LFI) for each day d such that $AD \leq d < DD$. At most one entertainment ticket can be assigned for each day $AD \leq d < DD$, and no client can be given more than one of the same entertainment ticket type. Given a feasible package, the client's utility is defined as

$$1000 - \emph{travelPenalty} + \emph{hotelBonus} + \emph{funBonus}$$

where

• travelPenalty = $100(\vert AD - {\it IAD}\vert + \vert DD - {\it IDD}\vert)$
• hotelBonus = GHV if the client is in the GBH, 0 otherwise.
• funBonus = sum of relevant EV's for each entertainment ticket type assigned to the client.

A TAC agent's final score is simply the sum of its clients' utilities minus the agent's expenditures. Throughout the game instance, it must decide what bids to place in each of the 28 auctions. At the end of the game, it must submit a final allocation of purchased goods to its clients.

The client preferences, allocations, and resulting utilities from one particular game from the TAC finals (Game 3070 on the TAC server) are shown in Tables 1 and 2.

 

Table 1: ATTac-2000's client preferences from game 3070. BEV, SEV, and TEV are EVs for baseball, symphony, and theater respectively.

Client	IAD	IDD	GHV	BEV	SEV	TEV
1	Day 2	Day 5	73	175	34	24
2	Day 1	Day 3	125	113	124	57
3	Day 4	Day 5	73	157	12	177
4	Day 1	Day 2	102	50	67	49
5	Day 1	Day 3	75	12	135	110
6	Day 2	Day 4	86	197	8	59
7	Day 1	Day 5	90	56	197	162
8	Day 1	Day 3	50	79	92	136

 

 

Table 2: ATTac-2000's client allocations and utilities from game 3070. Client 1's ``B4'' under ``Ent'ment'' indicates baseball on day 4.

Client	AD	DD	Hotel	Ent'ment	Utility
1	Day 2	Day 5	LFI	B4	1175
2	Day 1	Day 2	BGH	B1	1138
3	Day 3	Day 5	LFI	T3, B4	1234
4	Day 1	Day 2	BGH	None	1102
5	Day 1	Day 2	BGH	S1	1110
6	Day 2	Day 3	BGH	B2	1183
7	Day 1	Day 5	LFI	S2, B3, T4	1415
8	Day 1	Day 2	BGH	T1	1086

 

For full details on the design and mechanisms of the TAC server, see WellmanTAC00 WellmanTAC00.