If web architectures, performance, or scalability are topics you would like to keep on top of (who doesn't!), then chances are, you've heard of Nginx ("engine x"). Originally developed by Igor Sysoev for rambler.ru (second largest Russian web-site), it is
BACKGROUND: Research confirms that physical activity (PA) is irreplaceable in a healthy and physically active lifestyle. One of the key research questions is what the optimal level of everyday PA for health is and how it should be quantified and interpreted. Formal concept analysis is one possible way of how to assess and describe the level of PA as related to personal data. OBJECTIVE: The main goal of this study was to introduce the method of Formal Concept Analysis (FCA) using data from the ANEWS questionnaire and data from the objective monitoring of a number of steps using the YAMAX SW-701 pedometer. A further aim was to adopt the most appropriate method within the FCA. METHODS: A random sample of 273 males aged 18-69 from selected regional centers participated in the study. RESULTS: The example of daily steps allows for the demonstration of how important it is to select a scale in FCA data analysis. It is better to use an ordinal scale for the daily number of steps (in our example); because, in so doing, we create the attributes that can be ordered (a lower number of steps is also insufficient). CONCLUSIONS: A rough scale produces easier lattice with the general scope of the observed attributes. The smoothing of the scale produces more difficult lattice and makes for more difficult analyses, but gives more detailed results. FCA requires more expertise from a researcher than do "classical" testing statistics, but gives us deeper insight into the examination of the problem.
Main Page Data Structures Files libevent Documentation Introduction libevent is an event notification library for developing scalable network servers. The libevent API provides a mechanism to execute a callback function when a specific event occurs on a file descriptor or after a timeout has been reached. Furthermore, libevent also support callbacks due to signals or regular timeouts. libevent is meant to replace the event loop found in event driven network servers. An application just needs to call event_dispatch() and then add or remove events dynamically without having to change the event loop. Currently, libevent supports /dev/poll, kqueue(2), select(2), poll(2) and epoll(4). It also has experimental support for real-time signals. The internal event mechanism is completely independent of the exposed event API, and a simple update of libevent can provide new functionality without having to redesign the applications. As a result, Libevent allows for portable application developmen
Redis is a key-value database. It is similar to memcached but the dataset is not volatile, and keys can be strings, exactly like in memcached, but also lists and sets with atomic operations to push/pop elements. In order to be very fast but at the same time persistent the whole dataset is taken in memory and from time to time and/or when a number of changes to the dataset are performed it is written asynchronously on disk. You may lost the last few queries that is acceptable in many applications but it is as fast as an in memory DB (btw the SVN version of Redis includes support for replication in order to solve this problem by redundancy). Replication and other interesting features are a work in progress (Basic master <-> slave replication implemented in Redis SVN). Redis is written in ANSI C Redis is pretty fast!, 110000 SETs/second, 81000 GETs/second in an entry level Linux box.
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