{"title":"Pattern-Matching Problems for Two-Dimensional Images Described by Finite Automata","authors":"J. Karhumäki, Wojciech Plandowski, W. Rytter","doi":"10.1007/BFb0036188","DOIUrl":"https://doi.org/10.1007/BFb0036188","url":null,"abstract":"","PeriodicalId":114503,"journal":{"name":"Nord. J. Comput.","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130340146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-03-01DOI: 10.1007/978-3-642-59623-0_45
Dag I.K. Sjøberg, R. Welland, M. Atkinson, Paul Philbrow, C. Waite, S. Macneill
{"title":"The Persistent Workshop - a Programming Environment for Napier88","authors":"Dag I.K. Sjøberg, R. Welland, M. Atkinson, Paul Philbrow, C. Waite, S. Macneill","doi":"10.1007/978-3-642-59623-0_45","DOIUrl":"https://doi.org/10.1007/978-3-642-59623-0_45","url":null,"abstract":"","PeriodicalId":114503,"journal":{"name":"Nord. J. Comput.","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123008780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1996-07-03DOI: 10.1007/3-540-61422-2_124
Takao Asano, Takao Ono, T. Hirata
{"title":"Approximation Algorithms for the Maximum Satisfiability Problem","authors":"Takao Asano, Takao Ono, T. Hirata","doi":"10.1007/3-540-61422-2_124","DOIUrl":"https://doi.org/10.1007/3-540-61422-2_124","url":null,"abstract":"","PeriodicalId":114503,"journal":{"name":"Nord. J. Comput.","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115459009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1996-01-09DOI: 10.7146/BRICS.V3I9.19972
T. Husfeldt, Theis Rauhe, Søren Skyum
We give a number of new lower bounds in the cell probe model with logarithmic cell size, which entails the same bounds on the random access computer with logarithmic word size and unit cost operations. We study the signed prefix sum problem: given a string of length n of zeroes and signed ones, compute the sum of its ith prefix during updates. We show a lower bound of Omega(log n/log log n) time per operations, even if the prefix sums are bounded by log n/log log n during all updates. We also show that if the update time is bounded by the product of the worst-case update time and the answer to the query, then the update time must be Omega(sqrt(log n/ log log n)). These results allow us to prove lower bounds for a variety of seemingly unrelated dynamic problems. We give a lower bound for the dynamic planar point location in monotone subdivisions of Omega(log n/ log log n) per operation. We give a lower bound for the dynamic transitive closure problem on upward planar graphs with one source and one sink of Omega(log n/(log logn)^2) per operation. We give a lower bound of Omega(sqrt(log n/log log n)) for the dynamic membership problem of any Dyck language with two or more letters. This implies the same lower bound for the dynamic word problem for the free group with k generators. We also give lower bounds for the dynamic prefix majority and prefix equality problems.
{"title":"Lower Bounds for Dynamic Transitive Closure, Planar Point Location, and Parantheses Matching","authors":"T. Husfeldt, Theis Rauhe, Søren Skyum","doi":"10.7146/BRICS.V3I9.19972","DOIUrl":"https://doi.org/10.7146/BRICS.V3I9.19972","url":null,"abstract":"We give a number of new lower bounds in the cell probe model with logarithmic cell size, which entails the same bounds on the random access computer with logarithmic word size and unit cost operations. We study the signed prefix sum problem: given a string of length n of zeroes and signed ones, compute the sum of its ith prefix during updates. We show a lower bound of Omega(log n/log log n) time per operations, even if the prefix sums are bounded by log n/log log n during all updates. We also show that if the update time is bounded by the product of the worst-case update time and the answer to the query, then the update time must be Omega(sqrt(log n/ log log n)). These results allow us to prove lower bounds for a variety of seemingly unrelated dynamic problems. We give a lower bound for the dynamic planar point location in monotone subdivisions of Omega(log n/ log log n) per operation. We give a lower bound for the dynamic transitive closure problem on upward planar graphs with one source and one sink of Omega(log n/(log logn)^2) per operation. We give a lower bound of Omega(sqrt(log n/log log n)) for the dynamic membership problem of any Dyck language with two or more letters. This implies the same lower bound for the dynamic word problem for the free group with k generators. We also give lower bounds for the dynamic prefix majority and prefix equality problems.","PeriodicalId":114503,"journal":{"name":"Nord. J. Comput.","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115046674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-12-10DOI: 10.7146/BRICS.V1I48.21594
Jens Chr. Godskesen, K. Larsen
This paper describes a technique for generating diagnostic information for the timed bisimulation equivalence and the timed simulation preorder. More precisely, given two (parallel) networks of regular real-time processes, the technique will provide a logical formula that differentiates them in case they are not timed (bi)similar. Our method may be seen as an extension of the algorithm by Cerans for deciding timed bisimilarity in that information of time-quantities has been added sufficient for generating distinguishing formulae.
{"title":"Synthesizing Distinguishing Formulae for Real Time Systems","authors":"Jens Chr. Godskesen, K. Larsen","doi":"10.7146/BRICS.V1I48.21594","DOIUrl":"https://doi.org/10.7146/BRICS.V1I48.21594","url":null,"abstract":"This paper describes a technique for generating diagnostic information for the timed bisimulation equivalence and the timed simulation preorder. More precisely, given two (parallel) networks of regular real-time processes, the technique will provide a logical formula that differentiates them in case they are not timed (bi)similar. Our method may be seen as an extension of the algorithm by Cerans for deciding timed bisimilarity in that information of time-quantities has been added sufficient for generating distinguishing formulae.","PeriodicalId":114503,"journal":{"name":"Nord. J. Comput.","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121406985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-11-30DOI: 10.7146/BRICS.V1I35.21608
G. Brodal
The problem of making bounded in-degree and out-degree data structures partially persistent is considered. The node copying method of Driscoll et al. is extended so that updates can be performed in worst-case constant time on the pointer machine model. Previously it was only known to be possible in amortised constant time.The result is presented in terms of a new strategy for Dietz and Raman's dynamic two player pebble game on graphs.It is shown how to implement the strategy and the upper bound on the required number of pebbles is improved from 2b+2d+O(√b) to d+2b. where b is the bound of the in-degree and d the bound of the out-degree. We also give a lower bound that shows that the number of pebbles depends on the out-degree d.
{"title":"Partially Persistent Data Structures of Bounded Degree with Constant Update Time","authors":"G. Brodal","doi":"10.7146/BRICS.V1I35.21608","DOIUrl":"https://doi.org/10.7146/BRICS.V1I35.21608","url":null,"abstract":"The problem of making bounded in-degree and out-degree data structures partially persistent is considered. The node copying method of Driscoll et al. is extended so that updates can be performed in worst-case constant time on the pointer machine model. Previously it was only known to be possible in amortised constant time.The result is presented in terms of a new strategy for Dietz and Raman's dynamic two player pebble game on graphs.It is shown how to implement the strategy and the upper bound on the required number of pebbles is improved from 2b+2d+O(√b) to d+2b. where b is the bound of the in-degree and d the bound of the out-degree. We also give a lower bound that shows that the number of pebbles depends on the out-degree d.","PeriodicalId":114503,"journal":{"name":"Nord. J. Comput.","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130269005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-09-01DOI: 10.1007/3-540-56939-1_88
Bogdan S. Chlebus, K. Diks, A. Pelc
{"title":"Sparse Networks Supporting Efficient Reliable Broadcasting","authors":"Bogdan S. Chlebus, K. Diks, A. Pelc","doi":"10.1007/3-540-56939-1_88","DOIUrl":"https://doi.org/10.1007/3-540-56939-1_88","url":null,"abstract":"","PeriodicalId":114503,"journal":{"name":"Nord. J. Comput.","volume":"81 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114527156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-07-06DOI: 10.1007/3-540-58218-5_18
M. Halldórsson, J. Radhakrishnan
{"title":"Improved Approximations of Independent Sets in Bounded-Degree Graphs via Subgraph Removal","authors":"M. Halldórsson, J. Radhakrishnan","doi":"10.1007/3-540-58218-5_18","DOIUrl":"https://doi.org/10.1007/3-540-58218-5_18","url":null,"abstract":"","PeriodicalId":114503,"journal":{"name":"Nord. J. Comput.","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115409885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-07-06DOI: 10.1007/3-540-58218-5_28
Eric Schenk
{"title":"Parallel Dynamic Lowest Common Ancestors","authors":"Eric Schenk","doi":"10.1007/3-540-58218-5_28","DOIUrl":"https://doi.org/10.1007/3-540-58218-5_28","url":null,"abstract":"","PeriodicalId":114503,"journal":{"name":"Nord. J. Comput.","volume":"04 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128500351","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A clique-tree representation of a chordal graph often reduces the size of the data structure needed to store the graph, permitting the use of extremely efficient algorithms that take advantage of the compactness of the representation. Since some chordal graphs have many distinct clique-tree representations, it is interesting to consider which one is most desirable under various circumstances. A clique tree of minimum diameter (or height) is sometimes a natural candidate when choosing clique trees to be processed in a parallel-computing environment. This paper introduces a linear-time algorithm for computing a minimum-diameter clique tree.
{"title":"On Finding Minimum-Diameter Clique Trees","authors":"J. Blair, B. Peyton","doi":"10.2172/5217041","DOIUrl":"https://doi.org/10.2172/5217041","url":null,"abstract":"A clique-tree representation of a chordal graph often reduces the size of the data structure needed to store the graph, permitting the use of extremely efficient algorithms that take advantage of the compactness of the representation. Since some chordal graphs have many distinct clique-tree representations, it is interesting to consider which one is most desirable under various circumstances. A clique tree of minimum diameter (or height) is sometimes a natural candidate when choosing clique trees to be processed in a parallel-computing environment. This paper introduces a linear-time algorithm for computing a minimum-diameter clique tree.","PeriodicalId":114503,"journal":{"name":"Nord. J. Comput.","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115555020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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