Regular Expression Search on Compressed Text

We present an algorithm for searching regular expression matches in compressed text. The algorithm reports the number of matching lines in the uncompressed text in time linear in the size of its compressed version. We define efficient data structures that yield nearly optimal complexity bounds and provide a sequential implementation --zearch-- that requires up to 25% less time than the state of the art.Comment: 10 pages, published in Data Compression Conference (DCC'19

Approximating Petri Net Reachability Along Context-free Traces

We investigate the problem asking whether the intersection of a context-free language (CFL) and a Petri net language (PNL) is empty. Our contribution to solve this long-standing problem which relates, for instance, to the reachability analysis of recursive programs over unbounded data domain, is to identify a class of CFLs called the finite-index CFLs for which the problem is decidable. The k-index approximation of a CFL can be obtained by discarding all the words that cannot be derived within a budget k on the number of occurrences of non-terminals. A finite-index CFL is thus a CFL which coincides with its k-index approximation for some k. We decide whether the intersection of a finite-index CFL and a PNL is empty by reducing it to the reachability problem of Petri nets with weak inhibitor arcs, a class of systems with infinitely many states for which reachability is known to be decidable. Conversely, we show that the reachability problem for a Petri net with weak inhibitor arcs reduces to the emptiness problem of a finite-index CFL intersected with a PNL.Comment: 16 page

Underapproximation of Procedure Summaries for Integer Programs

We show how to underapproximate the procedure summaries of recursive programs over the integers using off-the-shelf analyzers for non-recursive programs. The novelty of our approach is that the non-recursive program we compute may capture unboundedly many behaviors of the original recursive program for which stack usage cannot be bounded. Moreover, we identify a class of recursive programs on which our method terminates and returns the precise summary relations without underapproximation. Doing so, we generalize a similar result for non-recursive programs to the recursive case. Finally, we present experimental results of an implementation of our method applied on a number of examples.Comment: 35 pages, 3 figures (this report supersedes the STTT version which in turn supersedes the TACAS'13 version

Perbedaan Angka Kejadian Ulkus Diabetika Pada Penderita DM Tipe 2 Dengan Hiperkolesterolemia Dan Normokolesterolemia

Latar belakang : Pasien DM dengan kelainan makrovaskular dapat memberikan gambaran kelainan pada tungkai bawah berupa ulkus diabetika.Pasien dengan ulkus diabetika ditemukan lebih dari 25% pada penderita diabetes melitus. Faktor risiko terjadinya ulkus diabetika pada penderita diabetes melitus meliputi usia, lamanya menderita DM, obesitas, kadar glukosa darah tidak terkontrol, dislipidemia, merokok, dan hipertensi. Diabetes melitus dengan hiperkolesterolemia memungkinkan peningkatan 100 kali lipat risiko gangren akibat aterosklerosis di ekstremitas bawah. Tujuan : Untuk mengetahui adanya perbedaan angka kejadian ulkus diabetika pada penderita diabetes melitus tipe 2 dengan hiperkolesterolemia dan normokolesterolemia Metode : Penelitian ini menggunakan rancangan cross sectional. Sampel penelitian ini adalah penderita DM tipe 2 yang menjalani perawatan di RSUD Dr. Moewardi periode Januari 2008 – Desember 2010. Subyek penelitian sebanyak 120 penderita DM tipe yaitu 60 pasien DM tipe 2 dengan hiperkolesterolemia dan 60 pasien DM tipe 2 dengan normokolesterolemia. Data diperoleh dari rekam medis dengan menggunakan teknik purposive sampling. Untuk mengetahui signifikansi perbedaan angka kejadian ulkus diabetika pada penderita DM Tipe 2 dengan hiperkolesterolemia dan normokolesterolemia digunakan uji chi square dengan α=0,05. Hasil : Didapatkan 44 pasien hiperkolesterolemia (73,3%) dengan ulkus diabetika dan 21(35%) pasien normokolesterolemia dengan ulkus diabetika. Analisis Chi square didapatkan nilai p = 0,000<α = 0,05 (bermakna) Kesimpulan : Terdapat perbedaan angka kejadian ulkus diabetika pada penderita diabetes melitus tipe 2 dengan hiperkolesterolemia dan normokolesterolemia (angka kejadian ulkus diabetika pada penderita DM hiperkolesterolemia lebih tinggi daripada penderita DM normokolesterolemia)

The Parikh Property for Weighted Context-Free Grammars

Parikh\u27s Theorem states that every context-free grammar (CFG) is equivalent to some regular CFG when the ordering of symbols in the words is ignored. The same is not true for the so-called weighted CFGs, which additionally assign a weight to each grammar rule. If the result holds for a given weighted CFG G, we say that G satisfies the Parikh property. We prove constructively that the Parikh property holds for every weighted nonexpansive CFG. We also give a decision procedure for the property when the weights are over the rationals

A Quasiorder-Based Perspective on Residual Automata

In this work, we define a framework of automata constructions based on quasiorders over words to provide new insights on the class of residual automata. We present a new residualization operation and a generalized double-reversal method for building the canonical residual automaton for a given language. Finally, we use our framework to offer a quasiorder-based perspective on NL^*, an online learning algorithm for residual automata. We conclude that quasiorders are fundamental to residual automata as congruences are to deterministic automata

A Congruence-based Perspective on Automata Minimization Algorithms

In this work we use a framework of finite-state automata constructions based on equivalences over words to provide new insights on the relation between well-known methods for computing the minimal deterministic automaton of a language