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This paper presents a parallel algorithm for computing formal concepts. Presented is a sequential version upon which we build the parallel one. We describe the algorithm, its implementation, scalability, and provide an initial experimental evaluation of its efficiency. The algorithm is fast, memory efficient, and can be optimized so that all criticalâ€¦ (More)

- Petr Krajca, Jan Outrata, VilÃ©m Vychodil
- CLA
- 2010

The paper presents a survey of recent advances in algorithms for computing all formal concepts in a given formal context which result as modifications or extensions of CbO. First, we present an extension of CbO, so called FCbO, and an improved canonicity test that significantly reduces the number of formal concepts which are computed multiple times. Second,â€¦ (More)

- Petr Krajca, Jan Outrata, VilÃ©m Vychodil
- Annals of Mathematics and Artificial Intelligence
- 2010

This paper presents a parallel algorithm for computing fixpoints of Galois connections induced by object-attribute relational data. The algorithm results as a parallelization of CbO (Kuznetsov 1999) in which we process disjoint sets of fixpoints simultaneously. One of the distinctive features of the algorithm compared to other parallel algorithms is that itâ€¦ (More)

- Petr Krajca, VilÃ©m Vychodil
- IDA
- 2009

- Petr Krajca, Jan Outrata, VilÃ©m Vychodil
- 2011 IEEE 11th International Conference on Dataâ€¦
- 2011

We address important issues of dimensionality reduction of transactional data sets where the input data consists of lists of transactions, each of them being a finite set of items. The reduction consists in finding a small set of new items, so-called factor-items, which is considerably smaller than the original set of items while comprising full or nearlyâ€¦ (More)

- Petr Krajca, VilÃ©m Vychodil
- SAC
- 2009

We outline new functional programming language and stack-based model of implicit parallel execution of programs. The language, called Schemik, is high-level lexically-scoped implicitly-parallel dialect of Scheme. Schemik is designed as an implicitly parallel language, meaning that the parallel execution of programs is done independently of the programmerâ€¦ (More)

- Petr Krajca, VilÃ©m Vychodil
- SAC
- 2010

During the last decade, software transactional memory (STM) gained wide popularity in many areas of parallel computing. In this paper, we introduce LISP-derived language equipped with automatic parallel execution and mutations based on software transactional memory. The novel idea is that we do not incorporate transactions as a language construct but ratherâ€¦ (More)

- Petr Krajca
- 2013 Federated Conference on Computer Science andâ€¦
- 2013

We present a novel method for automatic parallelization of functional programs which combines interpretation and just-in-time compilation. We propose an execution model for a Lisp-based programming language which involves a runtime environment which is able to identify portions of code worth running in parallel and is able to spawn new threads of execution.â€¦ (More)

- Petr Krajca, VilÃ©m Vychodil
- MDAI
- 2009

Presented is preliminary study of the role of data structures in algorithms for formal concept analysis. Studied is performance of selected algorithms in dependence on chosen data structures and size and density of input object-attribute data. The observations made in the paper can be seen as guidelines on how to select data structures for implementingâ€¦ (More)

- Petr Krajca
- MDAI
- 2015