In the job shop scheduling problem -units-, there are machines and each machine has an integer processing time of at most time units. Each job consists of a permutation of tasks corresponding to all machines and thus all jobs have an identical dilation . The contribution of this paper are the following results; (i) for jobs and every fixed , the makespan of an optimal schedule is at most , which extends the result of [3] for ; (ii) a randomized on-line approximation algorithm for -units- is presented. This is the on-line algorithm with the best known competitive ratio against an oblivious adversary for and ; (iii) different processing times yield harder instances than identical processing times. There is no competitive deterministic on-line algorithm for -units-, whereas the competitive ratio of the randomized on-line algorithm of (ii) still tends to 1 for .
@article{ITA_2009__43_2_189_0, author = {M\"omke, Tobias}, title = {On the power of randomization for job shop scheduling with $k$-units length tasks}, journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications}, volume = {43}, year = {2009}, pages = {189-207}, doi = {10.1051/ita:2008024}, mrnumber = {2512254}, zbl = {1166.68041}, language = {en}, url = {http://dml.mathdoc.fr/item/ITA_2009__43_2_189_0} }
Mömke, Tobias. On the power of randomization for job shop scheduling with $k$-units length tasks. RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications, Tome 43 (2009) pp. 189-207. doi : 10.1051/ita:2008024. http://gdmltest.u-ga.fr/item/ITA_2009__43_2_189_0/
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