Buy it, read it enjoy it; profit from it. It feels as if it has been well tested out on students and will work straight away. Probabilistic analysis of algorithms, randomized algorithms and probabilistic combinatorial constructions have become fundamental tools for computer science and applied mathematics. This book provides a thorough grounding in discrete probability and its applications in computing, at a level accessible to advanced undergraduates in the computational, mathematical and engineering sciences. Karp, University of California, Berkeley "The structure and pace of this book are well matched to the intended audience.
The authors consistently maintain a good balance between theory and applications Good students will be challenged and yet average students will find the text very readable. This is a very attractive textbook.
Probabilistic Analysis of the Simplex Method
I am pleased to say that Probability and Computing Michael Miztenmacher is a John L. Having written nearly articles on a variety of topics in computer science, his research focuses on randomized algorithms and networks. Sloan Research Fellowship. He has published more than papers in refereed journals and professional conferences, and is the inventor of more than ten patents. His main research interests are randomized computation and probabilistic analysis of algorithms, with applications to optimization algorithms, communication networks, parallel and distributed computing and computational biology.
Probabilistic analysis of power assignments
Randomization and probabilistic techniques play an important role in modern computer science, with applications ranging from combinatorial optimization and machine learning to communication networks and secure protocols. This textbook is designed to accompany a one- or two-semester course for advanced undergraduates or beginning graduate students in computer science and applied mathematics.
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It gives an excellent introduction to the probabilistic techniques and paradigms used in the development of probabilistic algorithms and analyses. It assumes only an elementary background in discrete mathematics and gives a rigorous yet accessible treatment of the material, with numerous examples and applications. The first half of the book covers core material, including random sampling, expectations, Markov's inequality, Chevyshev's inequality, Chernoff bounds, the probabilistic method and Markov chains. The second half covers more advanced topics such as continuous probability, applications of limited independence, entropy, Markov chain Monte Carlo methods and balanced allocations.
With its comprehensive selection of topics, along with many examples and exercises, this book is an indispensable teaching tool. Read more Read less. A Probabilistic Analysis. This book is a summary and extension of the prize winning research of the author Lanchester Prize on linear programming. Among the main topics are: Why is the Simplex Method so efficient? How can the large gap between worst-case and empirically observed performance of the Simplex Method be explained? The author was the first to answer these questions - challenging open problems for more than thirty years.
His results were obtained by analyzing the Simplex Method from a probabilistic point of view. Remark 3. Namely, we obtain. But similar properties typically hold for random point sets, namely smoothness in mean Definition 3. In the following, let. Recall that are drawn uniformly and independently from. Before proving smoothness in mean, we need a statement about the longest edge in an optimal PA graph and boundary PA graph.
The bound is asymptotically equal to the bound for the longest edge in an MST 19 , 14 , 7. To prove our bound for the longest edge in optimal PA graphs Lemma 3. Variants of both lemmas are known 25 , 20 , 19 , 7 , but, for completeness, we state and prove both lemmas in the forms that we need. For every , there exists a such that, with a probability of at least , every hyperball of radius and with center in contains at least one point of X in its interior.
The Simplex Method. A Probabilistic Analysis
We sketch the simple proof. Fix arbitrarily. We cover with hypercubes of side length such that every hyperball of radius — even if its center is in a corner for a point on the boundary, still at least a fraction is within — fully contains at least one box. The probability that such a box does not contain a point, which is necessary for a ball to be empty, is at most by independence of the points in X and the definition of.
The rest of the proof follows by a union bound over all boxes. We also need the following lemma, which essentially states that if z and are sufficiently far away, then there is — with high probability according to Lemma 3. Assume that every hyperball of radius with center in contains at least one point of X. Then the following holds: For every choice of with , there exists a point with the properties and.
The set of candidates for y contains a ball of radius , namely a ball of this radius whose center is at a distance of from z on the line between z and. For every , there exists a such that, with a probability of at least , every edge of an optimal PA graph and an optimal boundary PA graph is of length at most. We restrict ourselves to considering PA graphs.
The proof for boundary PA graphs is almost identical.
Let T be any PA graph. Let , where k is an upper bound for the number of vertices without a pairwise connection at a distance between r and for arbitrary r. It follows from Lemma 3. Note that. We are going to show that the following holds: Assume that every hyperball of radius with center in contains at least one point this is likely according to Lemma 3. Then for every PA graph T that contains an edge that is longer than , we can find a better PA graph, which shows that T is not optimal. Since the probability of the assumption is at least by Lemma 3.
Now assume that every ball of radius contains at least one point. This implies that the conclusion of Lemma 3. Let T be any PA graph that contains an edge of length at least. Let v be a vertex incident to the longest edge of T , and let be the length of a longest edge. The longest edge is unique with a probability of 1. The node v is not unique as the longest edge connects two nodes. We decrease the power of v to. This implies that v loses contact to some points — otherwise, the power assignment was clearly not optimal. Let with be the points that were connected to v but are in different connected components than v after decreasing v 's power.
This is because the only nodes that might lose their connection to v are within a distance between and , and there are at most k such nodes without a pairwise connection. Consider x 1. Iteratively for , we distinguish three cases until this process stops: i z i belongs to the same component as v. The process continues, and we can apply Lemma 3. We increase z i 's power such that z i is able to reach. This stops the process. In this case, we increase the energy of z i such that z i and x j are connected.
The energy of x j is sufficiently large anyhow. Running this process once decreases the number of connected components by one and costs at most additional power.
We run this process times, thus spending at most of additional power. In this way, we obtain a valid PA graph. We have to show that the new PA graph indeed saves power. By decreasing v 's power, we save an amount of. By the choice of , the saved amount of energy exceeds the additional amount of. This contradicts the optimality of the PA graph T with the edge of length. Since the longest edge has length at most with high probability, i.
Yukich gave two different notions of smoothness in mean 27 , 4. We use the stronger notion, which implies the other. Definition 3. A Euclidean functional is called smooth in mean if, for every constant , there exists a constant such that the following holds with a probability of at least : and for all. Thus, we can connect any of the k new vertices with costs of to the optimal PA graph for the n nodes. Let us now show the reverse inequality.
To do this, we show that with a probability of at least for some , we have 1. The proof of 1 is similar to the analogous inequality in Yukich's proof 27 , Lemma 4. The only difference is that we first have to redistribute the power of the point to its closest neighbors as in the proof of Lemma 3. In this way, removing results in a constant number of connected components. The longest edge incident to has a length of with a probability of at least.
Thus, we can connect these constant number of components with extra power of at most. The proof of and the statement for the boundary functional are almost identical. A Euclidean functional is close in mean to its boundary functional if. It is clear that for all X. Thus, in what follows, we prove that holds with a probability of at least for every. This implies closeness in mean.
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With a probability of at least for some sufficiently large constant , the longest edge in the graph that realizes has a length of with Lemma 3. Thus, with a probability of at least for any constant , only vertices within a distance of at most of the boundary are connected to the boundary. With a probability of at least , this number is exceeded by no more than a constant factor because of Chernoff's bound.
By Remark 3. Thus, removing the vertices close to the boundary as described above causes the boundary PA graph to fall apart into at most components. We choose one vertex of every component and start the process described in the proof of Lemma 3. The costs per connection is bounded from above by with a probability of for any constant. Thus, the total costs are bounded from above by with a probability of at least for any constant.
Our findings of Sections 3. Together with the probabilistic properties of Section 3. In Sections 4. Theorem 4. For all d and p with , there exists a constant such that converges completely to. This follows from the results in Section 3. For all and , there exists a constant equal to the constant of Theorem 4. This follows from the results in Sections 3. If we consider smoothness in mean see Lemma 3.
Simplex Method : A Probabilistic Analysis
Fortunately, Warnke 26 proved a generalization specifically for the case that the influence of single variables is typically bounded and fulfills a weaker bound in the worst case. The following theorem is a simplified version of a result by Lutz Warnke 26 , Theorem 1. Warnke 26 , Theorem 1. Then, for any and and , we have 3. Next, we introduce typical smoothness , which means that, with high probability, a single point does not have a significant influence on the value of , and we apply Theorem 4. The bound of in Definition 4.
This bound is also essentially the smallest possible, as there can be regions of diameter for some small constant that contain no or only a single point. It might be possible to obtain convergence results for other functionals by using a larger in the following definition. Definition 4. A Euclidean functional is typically smooth if, for every , there exists a constant such that with a probability of at least and. Assume that is typically smooth. We use Theorem 4. Thus, and. This only influences the constant c in the definition of in Definition 4. In the notation of Theorem 4.
Using the conclusion of Theorem 4. The following corollary is an immediate consequence of the theorem above. It suffices to prove complete convergence of typically smooth Euclidean functionals. Corollary 4. This follows immediately from Theorem 4. In this section, we prove that typical smoothness Definition 4. This implies complete convergence of and by Lemma 4. Assume that is typically smooth and converges in mean to. Then converges completely to. Fix any. Since there exists an n 0 such that for all.
Furthermore, there exists an n 1 such that, for all , the probability that the random variable deviates by more than from its expected value is smaller than for all. To see this, we use Corollary 4. The former only makes a statement about adding and removing several points at random positions. However, the proofs of smoothness in mean for and do not exploit this, and we can adapt them to yield typical smoothness.
Lemma 4. We first consider. We observe that, in the proof of smoothness in mean Lemma 3. Also the other way around, i. Thus, is typically smooth. Closely examining Yukich's proof of smoothness in mean for 27 , Lemma 4. For all d and p with , and converge completely to constants and , respectively. Both and are typically smooth and converge in mean. Thus, the corollary follows from Theorem 4. Thus, we only have to show that the lighter half of the edges of the MST contributes to the value of the MST in expectation. For simplicity, we assume that the number of points is odd. The case of even n is similar but slightly more technical.
We draw points as described above. Let denote the power required in the power assignment obtained from the MST. We omit the parameter X since it is clear from the context. Then, by the reasoning above, we have 5. For distances raised to the power p , the expected value of is. If we can prove that the lightest m edges of the MST are of weight , then it follows that the MST power assignment is strictly less than twice the optimal power assignment. Let denote the weight of these m lightest edges of the whole graph. Note that both and take edge lengths to the power p , and we have.
Let c be a small constant to be specified later on.