| 1. |
- Sweidan, Dirar, et al.
(författare)
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Predicting Customer Churn in Retailing
- 2022
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Ingår i: Proceedings 21st IEEE International Conference on Machine Learning and Applications ICMLA 2022. - : IEEE. - 9781665462839 - 9781665462846 ; , s. 635-640
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Konferensbidrag (refereegranskat)abstract
- Customer churn is one of the most challenging problems for digital retailers. With significantly higher costs for acquiring new customers than retaining existing ones, knowledge about which customers are likely to churn becomes essential. This paper reports a case study where a data-driven approach to churn prediction is used for predicting churners and gaining insights about the problem domain. The real-world data set used contains approximately 200 000 customers, describing each customer using more than 50 features. In the pre-processing, exploration, modeling and analysis, attributes related to recency, frequency, and monetary concepts are identified and utilized. In addition, correlations and feature importance are used to discover and understand churn indicators. One important finding is that the churn rate highly depends on the number of previous purchases. In the segment consisting of customers with only one previous purchase, more than 75% will churn, i.e., not make another purchase in the coming year. For customers with at least four previous purchases, the corresponding churn rate is around 25%. Further analysis shows that churning customers in general, and as expected, make smaller purchases and visit the online store less often. In the experimentation, three modeling techniques are evaluated, and the results show that, in particular, Gradient Boosting models can predict churners with relatively high accuracy while obtaining a good balance between precision and recall.
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| 2. |
- Sundell, Håkan, 1968, et al.
(författare)
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NOBLE: non-blocking programming support via lock-free shared abstract data types
- 2009
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Ingår i: SIGARCH Computer Architecture News. - : ACM, Association for Computing Machinery, Inc.. - 0163-5964 .- 1943-5851. ; 36:5, s. 80-87
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Tidskriftsartikel (refereegranskat)abstract
- An essential part of programming for multi-core and multi-processor includes ef cient and reliable means for sharing data. Lock-free data structures are known as very suitable for this purpose, although experienced to be very complex to design. In this paper, we present a software library of non-blocking abstract data types that have been designed to facilitate lock-free programming for non-experts. The system provides: i) ef cient implementations of the most commonly used data types in concurrent and sequential software design, ii) a lock-free memory management system, and iii) a run time-system. The library provides clear semantics that are at least as strong as those of corresponding lock-based implementations of the respective data types. Our software library can be used for facilitating lockfree programming; its design enables the programmer to: i) replace lock-based components of sequential or parallel code easily and ef ciently , ii) use well-tuned concurrent algorithms inside a software or hardware transactional system. In the paper we describe the design and functionality of the system. We also provide experimental results that show that the library can considerably improve the performance of software systems.
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| 3. |
- Wilhelmsson, Kenneth
(författare)
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Automatic Question Generation from Swedish Documents as a Tool for Information Extraction
- 2011
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Ingår i: Proceedings of the 18th Nordic Conference of Computational Linguistics NODALIDA 2011. ; , s. 323-326
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Konferensbidrag (refereegranskat)abstract
- An implementation of automatic question generation (QG) from raw Swedish text is presented. QG is here chosen as an alternative to natural query systems where any query can be posed and no indication is given of whether the current text database includes the information sought for. The program builds on parsing with grammatical functions from which corresponding questions are generated and it incorporates the article database of Swedish Wikipedia. The pilot system is meant to work with a text shown in the GUI and auto-completes user input to help find available questions. The act of question generation is here described together with early test results regarding the current produced questions.
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| 4. |
- Gidenstam, Anders, et al.
(författare)
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Cache-Aware Lock-Free Queues for Multiple Producers/Consumers and Weak Memory Consistency
- 2010
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Ingår i: Proceedings of the 14th International Conference on Principles of Distributed Systems (OPODIS) 2010. - Berlin, Heidelberg : Springer. - 9783642176524 - 3642176526 ; 6490, s. 302-317
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Konferensbidrag (refereegranskat)abstract
- A lock-free FIFO queue data structure is presented in this paper. The algorithm supports multiple producers and multiple consumers and weak memory models. It has been designed to be cache-aware and work directly on weak memory models. It utilizes the cache behavior in concert with lazy updates of shared data, and a dynamic lock-free memory management scheme to decrease unnecessary synchronization and increase performance. Experiments on an 8-way multi-core platform show significantly better performance for the new algorithm compared to previous fast lock-free algorithms.
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| 5. |
- Gidenstam, Anders, 1977, et al.
(författare)
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Efficient and Reliable Lock-Free Memory Reclamation Based on Reference Counting
- 2009
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Ingår i: IEEE Transactions on Parallel and Distributed Systems. - : IEEE. - 1558-2183 .- 1045-9219. ; 20:8, s. 1173-1187
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Tidskriftsartikel (refereegranskat)abstract
- We present an efficient and practical lock-free method for semiautomatic (application-guided) memory reclamation based on reference counting, aimed for use with arbitrary lock-free dynamic data structures. The method guarantees the safety of local as well as global references, supports arbitrary memory reuse, uses atomic primitives that are available in modern computer systems, and provides an upper bound on the amount of memory waiting to be reclaimed. To the best of our knowledge, this is the first lock-free method that provides all of these properties. We provide analytical and experimental study of the method. The experiments conducted have shown that the method can also provide significant performance improvements for lock-free algorithms of dynamic data structures that require strong memory management.
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| 6. |
- Linnusson, Henrik, et al.
(författare)
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Efficient conformal predictor ensembles
- 2020
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Ingår i: Neurocomputing. - : Elsevier BV. - 0925-2312 .- 1872-8286. ; 397, s. 266-278
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we study a generalization of a recently developed strategy for generating conformal predictor ensembles: out-of-bag calibration. The ensemble strategy is evaluated, both theoretically and empirically, against a commonly used alternative ensemble strategy, bootstrap conformal prediction, as well as common non-ensemble strategies. A thorough analysis is provided of out-of-bag calibration, with respect to theoretical validity, empirical validity (error rate), efficiency (prediction region size) and p-value stability (the degree of variance observed over multiple predictions for the same object). Empirical results show that out-of-bag calibration displays favorable characteristics with regard to these criteria, and we propose that out-of-bag calibration be adopted as a standard method for constructing conformal predictor ensembles.
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| 7. |
- Nguyen, Dang Nhan, 1983, et al.
(författare)
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Brief Announcement: ParMarkSplit: A Parallel Mark-Split Garbage Collector Based on a Lock-Free Skip-List
- 2013
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Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - : Springer. - 1611-3349 .- 0302-9743. - 9783642415265 ; 8205, s. 557-558
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Konferensbidrag (refereegranskat)abstract
- This brief announcement provides a high level overview of a parallel mark-split garbage collector. Our parallel design introduces and makes use of an efficient concurrency control mechanism based on a lock-free skip-list design for handling the list of free memory intervals. We have implemented the parallel mark-split garbage collector in OpenJDK HotSpot as a parallel and concurrent garbage collector for the old generation. We experimentally evaluate the collector and compare it with the default concurrent mark-sweep garbage collector in OpenJDK HotSpot, using the DaCapo benchmarks.
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| 8. |
- Nguyen, Dang Nhan, 1983, et al.
(författare)
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ParMarkSplit : A Parallel Mark-Split Garbage Collector Based on a Lock-Free Skip-List
- 2014
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Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - Cham : Springer. - 1611-3349 .- 0302-9743. - 9783319144719 - 9783319144726 ; 8878, s. 372-387
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Konferensbidrag (refereegranskat)abstract
- Mark-split is a garbage collection algorithm that combines advantages of both the mark-sweep and the copying collection algorithms. In this paper, we present a parallel mark-split garbage collector (GC). Our parallel design introduces and makes use of an efficient concurrency control mechanism for handling the list of free memory intervals. This mechanism is based on a lock-free skip-list design which supports an extended set of operations. Beside basic operations, it can perform a composite one that can search and remove and also insert two elements atomically. We have implemented the parallel mark-split GC in OpenJDK’s HotSpot virtual machine. We experimentally evaluate our collector and compare it with the default concurrent mark-sweep GC in HotSpot, using the DaCapo benchmarks, on two contemporary multiprocessor systems; one has 12 Intel Nehalem cores with HyperThreading and the other has 48 AMD Bulldozer cores. The evaluation shows that our parallel mark-split keeps the characteristics of the sequential mark-split, that it performs better than the concurrent mark-sweep in applications that have low live/garbage ratio, and have live objects locating contiguously, therefore being marked consecutively. Our parallel mark-split performs significantly better than a trivial parallelization based on locks in terms of both collection time and scalability.
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| 9. |
- Sundell, Håkan, 1968, et al.
(författare)
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A Lock-Free Algorithm for Concurrent Bags
- 2011
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Ingår i: 23rd ACM Symposium on Parallelism in Algorithms and Architectures, SPAA'11.San Jose, 4-6 June 2011. - New York, NY, USA : ACM. - 9781450307437 ; , s. 335-344
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A lock-free bag data structure supporting unordered buffering is presented in this paper. The algorithmsupports multiple producers and multiple consumers, as well as dynamic collection sizes. To handle concurrencyefficiently, the algorithm was designed to thrive for disjoint-access-parallelism for the supportedsemantics. Therefore, the algorithm exploits a distributed design combined with novel techniques for handlingconcurrent modifications of linked lists using double marks, detection of total emptiness, and efficientmemory management. Experiments on a 24-way multi-core platform show significantly better performancefor the new algorithm compared to previous algorithms of relevance.Keywords: concurrent; data structure; non-blocking; shared memory;
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| 10. |
- Sundell, Håkan, 1968, et al.
(författare)
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Brushing the Locks out of the Fur: A Lock-Free Work Stealing Library
- 2009
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Ingår i: econd Swedish Workshop on Multi-Core Computing, (MCC '09).
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Konferensbidrag (refereegranskat)abstract
- We present a lock-free version of the light-weight userleveltask management library called Wool, in an aim toshow that even extremely well tuned, in terms of synchronization,applications can benefit from lock-free programming.Explicit multi-threading is an efficient way to exploitthe offered parallelism of multi-core and multi-processorbased systems. However, it can sometimes be hard to expressthe inherited parallelism in programs using a limitednumber of long lived threads. Often it can be more straightforwardto dynamically create a large number of small tasksthat in turn automatically execute on the available threads.Wool is a promising and efficient library and frameworkthat allows the programmer to create user tasks in C witha very low overhead. The library automatically executestasks and balances the load evenly on a given number ofthreads by utilizing work stealing techniques. However, thesynchronization for stealing tasks is based on mutual exclusionwhich is known to limit parallelism and efficiency. Wehave designed and implemented a new lock-free algorithmfor synchronization of stealing tasks in Wool. Experimentsshow similar or significantly improved performance on a setof benchmarks executed on a multi-core platform.
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