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- Philipp Woelfel
- MFCS
- 2003

We present a symbolic OBDD algorithm for topological sorting which requires O(log 2 N) OBDD operations. Then we analyze its true runtime for the directed grid graph and show an upper bound of O(log 4 N). This is the first true runtime analysis of a symbolic OBDD algorithm for a fundamental graph problem, and it demonstrates that one can hope that the… (More)

- Martin Dietzfelbinger, Philipp Woelfel
- STOC
- 2003

We describe a simple randomized construction for generating pairs of hash functions <i>h<inf>1</inf>,h<inf>2</inf></i> from a universe U to ranges V = [m] = (0,1,...,m-1) and W = [m] so that for every key set S ⊆ U with n = |S| ≤ m/(1 + ε) the (random) bipartite (multi)graph with node set V ∪ W and edge set… (More)

- Philipp Woelfel
- Electronic Colloquium on Computational Complexity
- 2000

Bryant [5] has shown that any OBDD for the function MUL n−1,n , i.e. the middle bit of the n-bit multiplication, requires at least 2 n/8 nodes. In this paper a stronger lower bound of essentially 2 n/2 /61 is proven by a new technique, using a universal family of hash functions. As a consequence, one cannot hope anymore to verify e.g. 128-bit multiplication… (More)

- George Giakkoupis, Philipp Woelfel
- PODC
- 2012

We study the time and space complexity of randomized Test-And-Set (TAS) implementations from atomic read/write registers in asynchronous shared memory models with <i>n</i> processes. We present an adaptive TAS algorithm with an expected (individual) step complexity of <i>O</i>(log<sup>*</sup> <i>k</i>), for contention <i>k</i>, against the oblivious… (More)

- Beate Bollig, Philipp Woelfel
- STOC
- 2001

Branching programs (BPs) are a well-established computation and representation model for Boolean functions. Especially read-once branching programs (BP1s) have been studied intensively. Exponential lower bounds on the BP1 complexity of explicit functions have been known for a long time. Nevertheless, the proof of exponential lower bounds on the read-once… (More)

- Martin Sauerhoff, Philipp Woelfel
- STOC
- 2003

We prove exponential size lower bounds for nondeterministic and randomized read-<i>k</i> BPs as well as a time-space tradeoff lower bound for unrestricted, deterministic multi-way BPs computing the middle bit of integer multiplication. The lower bound for randomized read-<i>k</i> BPs is superpolynomial as long as the error probability is superpolynomially… (More)

- Paul Beame, Matei David, Toniann Pitassi, Philipp Woelfel
- ICALP
- 2007

We solve some fundamental problems in the number-on-forehead (NOF) k-party communication model. We show that there exists a function which has at most logarithmic communication complexity for randomized protocols with a one-sided error probability of 1/3 but which has linear communication complexity for deterministic protocols. The result is true for k = n… (More)

- Martin Aumüller, Martin Dietzfelbinger, Philipp Woelfel
- Algorithmica
- 2012

It is shown that for cuckoo hashing with a stash as proposed by Kirsch et al. (Proc. 16th European Symposium on Algorithms (ESA), pp. 611–622, Springer, Berlin, 2008) families of very simple hash functions can be used, maintaining the favorable performance guarantees: with constant stash size s the probability of a rehash is O(1/n s+1), the lookup time and… (More)

- Robin Nunkesser, Philipp Woelfel
- ISAAC
- 2005

In this paper, the space requirements for the OBDD representation of certain graph classes, specifically cographs, several types of graphs with few P4s, unit interval graphs, interval graphs and bipartite graphs are investigated. Upper and lower bounds are proven for all these graph classes and it is shown that in most (but not all) cases a representation… (More)

- Danny Hendler, Philipp Woelfel
- PODC
- 2009

<i>Mutual exclusion</i> is a fundamental distributed coordination problem. Shared-memory mutual exclusion research focuses on <i>local-spin</i> algorithms and uses the <i>remote memory references</i> (RMRs) metric. A recent proof [9] established an Ω(log <i>N</i>) lower bound on the number of RMRs incurred by processes as they enter and exit the… (More)