computer-science

I've recently started a course on data compression at my university. However, I find the use of the term "entropy" as it applies to computer science rather ambiguous. As far as I can tell, it roughly translates to the "randomness" of a system or structure. What is the proper definition of computer science "entropy"? Entropy can mean different things: Computing In computing, entropy is the randomness collected by an operating system or application for use in cryptography or other uses that require random data. This randomness is often collected from hardware sources, either pre-existing ones

Can someone please tell me what a finite state transducer is? I have read the Wikipedia article and don't understand a thing. A finite state transducer (FST) is a finite state automaton (FSA, FA) which produces output as well as reading input, which means it is useful for parsing (while a "bare" FSA can only be used for recognizing, i.e. pattern matching). An FST consists of a finite number of states which are linked by transitions labeled with an input/output pair. The FST starts out in a designated start state and jumps to different states depending on the input, while producing output

I've found that lots of people use the words closure and block interchangeably. Most of these people can't explain what they're talking about. Some Java programmers (even ones from really expensive consultancies) talk about anonymous inner classes as "blocks" and "closures" - but I know this isn't true. (You can't pass mutable variables in from the scope of the method in which they're defined...) I'm looking for: a precise, computer science definition of a block a precise, computer science definition of a closure and clarification on the difference between the two. I'd really like to see links

In BigTable/GFS and Cassandra terminology, what is the definition of a SSTable? Sorted Strings Table (borrowed from google) is a file of key/value string pairs, sorted by keys "An SSTable provides a persistent,ordered immutable map from keys to values, where both keys and values are arbitrary byte strings. Operations are provided to look up the value associated with a specified key, and to iterate over all key/value pairs in a specified key range. Internally, each SSTable contains a sequence of blocks (typically each block is 64KB in size, but this is configurable). A block index (stored at

I am going to start learning Abstract Algebra- Groups, Rings,etc. I am interested to know any programming language, if at all which can help me learn/try the concepts I learn in theory. EDIT: I am not really looking at implementing what I learn. I am interested to know any language which already supports them. jason The text that you want here is Abstract Algebra, A Computational Approach by Chuck Sims. The author will recommend that you use the APL programming language. The book is out of print, but you can probably find it in your library. There is also the GAP Computer Algebra System which

Recently there has been a paper floating around by Vinay Deolalikar at HP Labs which claims to have proved that P != NP . Could someone explain how this proof works for us less mathematically inclined people? Michael Anderson I've only scanned through the paper, but here's a rough summary of how it all hangs together. From page 86 of the paper. ... polynomial time algorithms succeed by successively “breaking up” the problem into smaller subproblems that are joined to each other through conditional independence. Consequently, polynomial time algorithms cannot solve problems in regimes where

I often hear about eventual consistency in different speeches about NoSQL, data grids etc. It seems that definition of eventual consistency varies in many sources (and maybe even depends on a concrete data storage). Can anyone give a simple explanation what Eventual Consistency is in general terms, not related to any concrete data storage? Eventual consistency: I watch the weather report and learn that it's going to rain tomorrow. I tell you that it's going to rain tomorrow. Your neighbor tells his wife that it's going to be sunny tomorrow. You tell your neighbor that it is going to rain

What concepts in Computer Science do you think have made you a better programmer? My degree was in Mechanical Engineering so having ended up as a programmer, I'm a bit lacking in the basics. There are a few standard CS concepts which I've learnt recently that have given me a much deeper understanding of what I'm doing, specifically: Language Features Pointers & Recursion (Thanks Joel!) Data Structures Linked Lists Hashtables Algorithms Bubble Sorts Obviously, the list is a little short at the moment so I was hoping for suggestions as to: What concepts I should understand, Any good resources

From Operating System Concepts In the solution to the first readers–writers problem, the reader processes share the following data structures: semaphore rw mutex = 1; semaphore mutex = 1; int read_count = 0; do { wait(rw_mutex); . . . /* writing is performed */ . . . signal(rw_mutex); } while (true); Figure 5.11 The structure of a writer process. do { wait(mutex); read count++; if (read_count == 1) wait(rw mutex); signal(mutex); . . . /* reading is performed */ . . . wait(mutex); read count--; if (read_count == 0) signal(rw_mutex); signal(mutex); } while (true); Figure 5.12 The structure of a