We consider unidirectional data streams with restricted access, such as read-only and write-only streams. For read-write streams, we also introduce a new complexity measure called expansion, the ratio between the space used on the stream and the input size. We give tight bounds for the complexity of reversing a stream of length n in several of the possible models. In the read-only and write-only model, we show that p-pass algorithms need memory space Theta(n/p). But if either the output stream or the input stream is read-write, then the complexity falls to Theta(n/p^2). It becomes polylog(n) if p = O(log n) and both streams are read-write. We also study the complexity of sorting a stream and give two algorithms with small expansion. Our main sorting algorithm is randomized and has O(1) expansion, O(log n) passes and O(log n) memory.
@InProceedings{francois_et_al:LIPIcs.APPROX-RANDOM.2014.654, author = {Fran\c{c}ois, Nathana\"{e}l and Jain, Rahul and Magniez, Fr\'{e}d\'{e}ric}, title = {{Unidirectional Input/Output Streaming Complexity of Reversal and Sorting}}, booktitle = {Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2014)}, pages = {654--668}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-939897-74-3}, ISSN = {1868-8969}, year = {2014}, volume = {28}, editor = {Jansen, Klaus and Rolim, Jos\'{e} and Devanur, Nikhil R. and Moore, Cristopher}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.APPROX-RANDOM.2014.654}, URN = {urn:nbn:de:0030-drops-47298}, doi = {10.4230/LIPIcs.APPROX-RANDOM.2014.654}, annote = {Keywords: Streaming Algorithms, Multiple Streams, Reversal, Sorting} }
Feedback for Dagstuhl Publishing