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Closed 11 years ago.
What are good resource to read up on for implementing numerical algorithms in pure java?
I know nothing about the interactions of the JVM & GC, and would love to learn more.
I enjoyed Object Oriented Implementation of Numerical Methods by Didier Besset. To be honest I use C++ almost exclusively but found this book interesting and fun nonetheless. It doesn't always use the best algorithm for the job, however.
I would also point you towards Matrix Computations by Golub & Van Loan. Not about Java by any means, but a mandatory text for anybody working in this area.
Pick up a copy of Numerical Recipes in C++. NR doesn't always contain the best algorithms for the problems it tackles, it's a pedagogical text not a library of optimized code. But the explanations are generally good and the range of topics is wide. By picking up the C++ version you can learn some Java while you translate the code. Also pick up a good book on the basics of floating-point arithmetic and numerical analysis.
Numerics: http://math.nist.gov/javanumerics/
GC intro: http://www.ibm.com/developerworks/java/library/j-jtp11253/
Java Number Cruncher is a good start. I don't think it deals with GC issues, though. Anyway, floating point precision issues are quite likely more relevant in numerical algorithms, usually. The book does demonstrate that doubles can actually be inferior to floats in some cases.
Apache Commons Math has some nice linear algebra libraries, among other things.
Linear algebra is the basis for lots of serious numerical work (e.g., finite difference, finite element, and boundary element formulations for problems in solid and fluid mechanics and heat transfer). AFAIK, most of that work is still done by commercial and in-house packages written in FORTRAN. Java and even C++ and C were not considered performant enough for such things back when I did them for a living. I'd be surprised if that has changed.
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Closed 10 years ago.
I often use the Stack data structure in both Java and C++. This is a standard data structure, very common in implementing many algorithms.
My question is (and the thing that drives me crazy) why does C++ use "top" as a function-name that returns the top-most element value without removing it, and Java uses "peek" as it's method name?
I know there is no standard for data structures, but hasn't computer science come far enough along that there should be a standard? Or am I just too much of a novice to know about a standard...
Do those of you that are professional programmers write your own data-structure libraries that adhere to a common interface across languages? That seems like the best thing to do, in my mind. I write code in C++, Java, Python, C, Perl, and PHP. I just don't see any other way but to write a custom interface for all of these languages. I like "peek", but is there any standard I should be aiming for?
Writing a custom interface just to make method names the same would be a colossal waste of time. What exactly would be the point? You wouldn't be able to easily copy-and-paste most code between the languages you've mentioned even with such a feature.
Personally, I don't like the name of the STL vector method push_back(). I would prefer if it were just called add(), for one thing it'd be less typing. It never occurred to me that I might change it, however. Doing so would just make my code less portable and less readable for others. Now, I suppose this could be done fairly easily with a pre-processor macro, but even that would be a waste of time in my mind.
No there can't be, won't be, and never will be a standard. Anyway, both names are valid, and if you ask me, top makes more sense. Also, as #mimicocotopus says, it's not like having the same method names would let you copy paste code from one language to another. Also, languages like C++ and Java are very distinct, and support different features. If a standard had to use the lowest common denominator, it couldn't take advantage of all of the features of the language it was implemented in.
Anyway, remember what happened last time we standardized something? Cross browser compatibility and porting C code. It gives me shudders just to think of it.
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Closed 11 years ago.
I'm doing some text mining in web pages. Currently I'm working with Java, but maybe there is more appropriate languages to do what I want.
Example of some things I want to do:
Determine the char type of a word based on it parts (letter, digit, symbols, etc.) as Alphabetic, Number, Alphanumeric, Symbol, etc.(there is more types).
Discover stop words based on statistics.
Discover some gramatical class (verb, noun, preposition, conjuntion) based on statistics and some logics.
I was thinking about using Prolog and R (I don't know much about these languages), but I don't know if they are good for this or maybe, another language more appropriate.
Which can I use? Good libs for Java are welcome too.
python.!
They have a HELL-LOTTA libraries in this area.
but, i've got no knowledge about prologue and R.. but definitely py is LOT better than java in text mining, and AI stuff...
I highly recommend Perl. It has a lot of text-processing features, web search and parsing, and a large etc. Take a look at the available modules (>23.000 and growing) at CPAN.
I think Apache Solr and Nutch provides you the framework for that and on top of that you can extend it for your requirements.
Java has some basic support, but nothing like the above two products, they are awesome!
HTML Unit might give you some good APIs for fetching web pages, and traversing over elements in DOM by XPath. I have used it for sometime to perform simple to more complex operations.
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Closed 11 years ago.
I am new to this kind of computing. I don't know what are the existing distance functions that are helpful to calculate the distance between to double sets(arrays). Can some one suggest me at-least 10 distance functions so that i can select few among them which suits best for my problem domain. I just want to calculate the distance between two sets for my scientific approach to the problem domain. I also want to know whether i have to implement them manually or any java API that covers most distance functions? Suggestions can help me to minimize my effort and save my time..:)
Providing you with code is not really going to help. What you need to do is to read up on the mathematics of the the various measures of distance, and figure out which is most appropriate based on that knowledge.
You could start by reading the Wikipedia page on Distance and the linked pages and resources.
Only when you've decide on an appropriate measure do you need to go looking for code. In a lot of cases, it is probably simplest to implement the measure yourself.
Alternatively, if you want us to provide sensible suggestions of measures that are appropriate to your problem domain, tell us what the problem domain is.
Are we talking about statistical distance between two samples? If so, there is an abundance of methods, each one suiting a different problem.
If your problem domain is simple, subtracting the sample means (averages) could suffice. For more complex data, the Earth Movers' Distance is common, though newer and more robust methods (such as kernel functions) are available.
Coding is the least of your problems. You must provide a more accurate definition of your problem before I can further assist you.
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Closed 12 years ago.
I know that is Collections.sort() method in Java but I think quicksort is worth to remember and try.
My work target is general Java: web, database access, integration, not game developer, scientific application or another one that depends on advanced algorithms.
Which algorithms should I learn to pass without stress Java developer interview?
Fizz Buzz
I usually don't care, if a developer knows the basic algorithms by heart. I do care, if he is capabale of understanding requirements and translating them in correct, testable and understandable pieces of code.
Ah, and I do care if he knows how to implement the most common design patterns. And he should know when and how to use collections, threads and - String#split - it's amazing how many "developers" don't know how to read and process a simple csv file.
Although I fully agree with Joachim comment, I would go for : collection selection. This is not an algorithm per se, but rather a good view of which collection is good for which purpose :
sorted content with constant lookup time ? TreeSet !
mapped data with memorization of insertion order ? LinkedHashMap !
using that, and some knowledge of design patterns behind collections, you will far too often reply to algorithms questions using the knuth answer (or the subtle variation : as long as Sun developpers implemented it correctly, I only have to choose wisely).
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Closed 12 years ago.
This is a subjective question just to get a general impression. As Java is the most popular programming language right now it is used as a benchmark.
Lets say I have to spend T amount of time/effort to learn/master Java. By what factor should I multiply T to get a time/effort needed to learn/master other language instead, say C, C++, C#, python, perl, Lisp, Haskel, PHP?
My guess is:
0.5T PHP
0.9T python
1.1T C#
2.0T C++
3.0T C
What do you think?
Personally, I'd suggest Brainfuck. It's my favourite language for beginners. Don't worry, the name is joke!
Dartmouth BASIC was designed to be easy to learn and easy to use. For what it did, it was a howling success on both counts.
MIT used Scheme (dialect of LISP) in course 6.001 for many years, and concluded that it was a lot easier to learn, at least initially, because there was essentially no syntax to trip students up.
Back in the late Steam Era, when mainframe dinosaurs still ruled the Earth, the UT Austin Computer Science Department did side-by-side tests, teaching FORTRAN to some of the freshman and PASCAL to others. Their conclusion was that PASCAL's pickier syntax was INITIALLY harder to learn, but the PASCAL students consistently spent less computer time, and less runs (batch processing, punched cards), getting their homework running, even though their homework assignments were typically harder.
C and C++ have very, very similar core languages. 90% of the code you write will be identical in all four languages, after allowing for personal taste in design and naming conventions. C doesn't really have anything above the core language, while C++ adds classes and templates. I'm not familiar with C# or Java, beyond a rudimentary feeling that they both started with C and went from there.
Ada was, in my personal experience, not difficult to learn, and the compilers were picky enough that syntactically-correct code generally worked as intended on the first try. Other people have also noticed that property of Ada.
This is so subjective that it cannot be answered. It totally depends on what you need to do with the language.