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-rw-r--r-- | main.tex | 34 |
1 files changed, 23 insertions, 11 deletions
@@ -304,7 +304,7 @@ We have implemented \emph{Gale-Shapley} and an instance set creation script to t | |||
304 | \section{Stable Matching Variation}% | 304 | \section{Stable Matching Variation}% |
305 | \label{sec:stable_matching_variation} | 305 | \label{sec:stable_matching_variation} |
306 | 306 | ||
307 | % stable matching question ALMOST {{{1 % | 307 | % stable matching question ✅ {{{1 % |
308 | 308 | ||
309 | \begin{question} | 309 | \begin{question} |
310 | Consider a Stable Matching problem with men and women. | 310 | Consider a Stable Matching problem with men and women. |
@@ -313,12 +313,15 @@ We have implemented \emph{Gale-Shapley} and an instance set creation script to t | |||
313 | Either give a proof that shows such an improvement is impossible, or give an example preference list for which an improvement for $w$ is possible. | 313 | Either give a proof that shows such an improvement is impossible, or give an example preference list for which an improvement for $w$ is possible. |
314 | \end{question} | 314 | \end{question} |
315 | 315 | ||
316 | Example preference list for men; $M = {x,y,z}$ and women: $W = {a,b,c}$. | 316 | We will give an example instance. |
317 | Let's take the example preference list for men; $M = {x,y,z}$ and women: $W = {a,b,c}$. | ||
317 | 318 | ||
318 | \begin{table}[!htb] | 319 | \begin{table}[!htb] |
319 | \caption{Preference lists of women.} | 320 | \caption{Preference lists of women}% |
321 | \label{table:2_general} | ||
320 | \begin{minipage}{.5\linewidth} | 322 | \begin{minipage}{.5\linewidth} |
321 | \caption{Everyone is being truthful} | 323 | \caption{Everyone is being truthful}% |
324 | \label{table:2_true} | ||
322 | \centering | 325 | \centering |
323 | \begin{tabular}{l|lll} | 326 | \begin{tabular}{l|lll} |
324 | \textbf{a} & y & x & z \\ | 327 | \textbf{a} & y & x & z \\ |
@@ -328,19 +331,22 @@ Example preference list for men; $M = {x,y,z}$ and women: $W = {a,b,c}$. | |||
328 | \end{minipage}% | 331 | \end{minipage}% |
329 | \begin{minipage}{.5\linewidth} | 332 | \begin{minipage}{.5\linewidth} |
330 | \centering | 333 | \centering |
331 | \caption{a is lying about their preference} | 334 | \caption{a is lying about their preference}% |
335 | \label{table:2_lie} | ||
332 | \begin{tabular}{l|lll} | 336 | \begin{tabular}{l|lll} |
333 | \textbf{a} & y & z & x \\ | 337 | \textbf{a} & y & z & x \\ |
334 | \textbf{b} & x & y & z \\ | 338 | \textbf{b} & x & y & z \\ |
335 | \textbf{c} & x & y & z | 339 | \textbf{c} & x & y & z |
336 | \end{tabular} | 340 | \end{tabular} |
337 | \begin{tikzpicture}[overlay] | 341 | \begin{tikzpicture}[overlay] |
338 | \draw[red, line width=1pt] (-0.72,0.52) ellipse (0.70cm and 0.2cm); | 342 | \draw[red, line width=1pt] (-0.72,0.52) ellipse (0.70cm and 0.2cm); |
339 | \end{tikzpicture} | 343 | \end{tikzpicture} |
340 | \end{minipage} | 344 | \end{minipage} |
341 | \end{table} | 345 | \end{table} |
342 | 346 | ||
343 | % TODO: final polish, highlight the lies <06-11-20, yigit> % | 347 | In the example given above in Table~\ref{table:2_general}, we have two cases for women, Table~\ref{table:2_true} where everyone has given their actual preference list and Table~\ref{table:2_lie} where $a$ has lied about their \nth{2} and \nth{3} preferences. |
348 | |||
349 | The following is the men's preference table; | ||
344 | 350 | ||
345 | \begin{table}[htb] | 351 | \begin{table}[htb] |
346 | \centering | 352 | \centering |
@@ -353,7 +359,7 @@ Example preference list for men; $M = {x,y,z}$ and women: $W = {a,b,c}$. | |||
353 | \label{tab:men_pref} | 359 | \label{tab:men_pref} |
354 | \end{table} | 360 | \end{table} |
355 | 361 | ||
356 | The trace of \emph{Gale-Shapley} algorithm for the truth telling case; | 362 | The trace of \emph{Gale-Shapley} algorithm for the truth telling case with Table~\ref{table:2_true} and Table~\ref{tab:men_pref} is below; |
357 | 363 | ||
358 | \begin{enumerate} | 364 | \begin{enumerate} |
359 | \item Matching x with a (a) | 365 | \item Matching x with a (a) |
@@ -363,30 +369,36 @@ The trace of \emph{Gale-Shapley} algorithm for the truth telling case; | |||
363 | \item Matching z with c (a) | 369 | \item Matching z with c (a) |
364 | \end{enumerate} | 370 | \end{enumerate} |
365 | 371 | ||
372 | Which produces the following matching. Note that $a$ is matched with their \nth{2} choice. | ||
373 | |||
366 | \begin{align*} | 374 | \begin{align*} |
367 | x &\rightarrow a \\ | 375 | x &\rightarrow a \\ |
368 | y &\rightarrow b \\ | 376 | y &\rightarrow b \\ |
369 | z &\rightarrow c | 377 | z &\rightarrow c |
370 | \end{align*} | 378 | \end{align*} |
371 | 379 | ||
372 | The trace of \emph{Gale-Shapley} algorithm when \emph{a} lies about their preferences; | 380 | Now let's examine the trace of the algorithm when $a$ lies by providing an altered preference table. The trace below uses Table~\ref{table:2_lie} and Table~\ref{tab:men_pref}; |
373 | 381 | ||
374 | \begin{enumerate} | 382 | \begin{enumerate} |
375 | \item Matching y with b (a) | 383 | \item Matching y with b (a) |
376 | \item Matching z with a (a) | 384 | \item Matching z with a (a) |
377 | \item x proposes to a but gets rejected because a prefers z more (c) | 385 | \item \textbf{x proposes to a but gets rejected because a lies by saying that they like z more (c)} |
378 | \item Matching x with b, y is now free (b) | 386 | \item Matching x with b, y is now free (b) |
379 | \item Matching y with a, z is now free (b) | 387 | \item \textbf{Matching y with a, z is now free (b)} |
380 | \item z proposes to b but gets rejected because b prefers x more (c) | 388 | \item z proposes to b but gets rejected because b prefers x more (c) |
381 | \item Matching z with c (a) | 389 | \item Matching z with c (a) |
382 | \end{enumerate} | 390 | \end{enumerate} |
383 | 391 | ||
392 | The highlighted lines show that $a$ lies when proposed by $x$ and then is able to trade up to $y$. The following it the final matching; | ||
393 | |||
384 | \begin{align*} | 394 | \begin{align*} |
385 | x &\rightarrow b \\ | 395 | x &\rightarrow b \\ |
386 | y &\rightarrow a \\ | 396 | y &\rightarrow a \\ |
387 | z &\rightarrow c | 397 | z &\rightarrow c |
388 | \end{align*} | 398 | \end{align*} |
389 | 399 | ||
400 | Woman $a$ was able to get their highest preferred option $y$ by telling a lie. We have proved that an improvement is possible. | ||
401 | |||
390 | % 1}}} % | 402 | % 1}}} % |
391 | 403 | ||
392 | \section{Asymptotics}% | 404 | \section{Asymptotics}% |