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  • For what purpose does java have a float primitive type?

    - by Roman
    I heard plenty times different claims about float type in java. The most popular issues typicaly regard to converting float value to double and vice versa. I read (rather long time ago and not sure that it's actual now with new JVM) that float gives much worse performance then double. And it's also not recommended to use float in scientific applications which should have certain accuracy. I also remember that when I worked with AWT and Swing I had some problems with using float or double (like using Point2D.Float or Point2D.Double). So, I see only 2 advantages of float over double: it needs only 4 bytes while double needs 8 bytes JMM garantees that assignment operation is atomic with float variables while it's not atomic with double's. Are there any other cases where float is better then double? Do you use float's in your applications? It seems to me that the only valuable reason java has float is backward compatibility.

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  • What is the standard way to parse floats at runtime in C?

    - by Joel J. Adamson
    Hello, I have a scientific application for which I want to input initial values at runtime. I have an option to get them from the command line, or to get them from an input file. Either of these options are input to a generic parser that uses strtod to return a linked list of initial values for each simulation run. I either use the command-line argument or getline() to read the values. The question is, should I be rolling my own parser, or should I be using a parser-generator or some library? What is the standard method? This is the only data I will read at runtime, and everything else is set at compile time (except for output files and a few other totally simple things). Thanks, Joel

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  • Should I bundle C libraries with my Python application?

    - by oceanhug
    If I have a Python package that depends on some C libraries (like say the Gnu Scientific Library (GSL) for numerical computations), is it a good idea to bundle the library with my code? I'd like to make my package as easy to install as possible for users and I don't want them to have to download C libraries by hand and supply include-paths. Also I could always ensure that the version of the library that I ship is compatible with my code. However, is it possible that there are clashes if the user has the library installed already, or ar there any other reasons why I shouldn't do this? I know that I can make it easier for users by just providing a binary distribution, but I'd like to avoid having to maintain binary distributions for all possible OSs. So, I'd like to stick to a source distribution, but for the user (who proudly owns a C compiler) installation should be as easy as python setup.py install.

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  • Python Library installation

    - by MacPython
    Hi everybody I have two questions regarding python libraries: I would like to know if there is something like a "super" python library which lets me install ALL or at least all scientific useful python libraries, which I can install once and then I have all I need. There is a number of annoying problems when installing different libraries (pythonpath, cant import because it is not installed BUT it is installed). Is there any good documentation about common installation errors and how to avoid them. If there is no total solution I would be interested in numpy, scipy, matplotlib, PIL Thanks a lot for the attention and help Best Z

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  • Confusion between numpy, scipy, matplotlib and pylab

    - by goFrendiAsgard
    Numpy, scipy, matplotlib, and pylab are common terms among they who use python for scientific computation. I just learn a bit about pylab, and I got a lot of confusion. Whenever I want to import numpy, I can always do: import numpy as np I just consider, that once I do from pylab import * The numpy will be imported as well (with np alias). So basically the second one do more things compared to the first one. There are few things I want to ask. Is it right that pylab is just a wrapper for numpy, scipy and matplotlib? As np is the numpy alias, what is the scipy and matplotlib alias? (as far as I know, plt is alias of matplotlib.pyplot, but I don't know the alias for the matplotlib itself) Thanks in advance.

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  • Search Result displaying-like google php

    - by Ramesh
    i have an paragraph and user will search inside that and if the search term has 3 matches inside but all are in 3 different places ex World War II, or the Second World War[1] (often abbreviated WWII or WW2), was a global military conflict lasting from 1939 to 1945 which involved most of the world's nations, including all of the great powers, organised into two opposing military alliances: the Allies and the Axis. It was the most widespread war in history, with more than 100 million military personnel mobilised. In a state of "total war," the major participants placed their entire economic, industrial, and scientific capabilities at the service of the war effort, erasing the distinction between civilian and military resources. Marked by significant action against civilians, including the Holocaust and the only use of nuclear weapons in warfare, it was the deadliest conflict in human history,[2] with over seventy million casualties. i have to search "war" so that it should display like World War II, or the Second World War[1].....In a state of "totalwar,".... some thing like this ///

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  • Whats the deal with python?

    - by gmatt
    My interests in programming lie mainly in algorithms, and lately I have seen many reputable researchers write a lot of their code in python. How easy and convenient is python for scientific computing? Does it have a library of algorithms that compares to matlab's? Is Python a scripting language or does it compile? Is it a great language for prototyping an algorithm? How long would it take me to learn enough of it to be productive provided I know C well and OO programming somewhat? Is it OO based? Sorry for the condensed format of questions, but I'm very curious and was hoping a more experienced programmer could help me out.

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  • JSF (and friends) tags vs. traditional html tags

    - by H3wh0s33ks
    So this question came up today and I didn't have a specific or scientific answer. What are the costs associated with using jsf (or tomahawk, faclets, etc., etc.) tags in place of traditional html tags. My gut reaction is that you should use jsf tags in situations where you need the additional functionality they provide, and use traditional tags when you don't. Also I feel like jsf tags would require more resources (since the server has to take them and rerender them as html anyways) than html. Does anybody know what the cost actually is (as far as time and memory)? Also useful information is what is the convention that is in use, pure jsf or a mixture of the two?

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  • Looking for a list of free data api's and web services

    - by darren
    I'm wondering if anybody has come across a comprehensive list of free sources for data (as a web api) or web services. I'm looking to start a new project to tinker with in my spare time and I am wondering what interesting data is available to play with. It seems like many api services such as last.fm or google search don't exist or are no longer free. Possible examples of what I am looking for information about a given ip address mapping api's information about books, movies, music information about places, businesses, attractions meteorological, financial or other scientific data shopping, products I would appreciate any suggestions you may have about interesting data freely available through the web. thanks

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  • Tips for measuring the parallelism speed-up in multi-core development.

    - by fnCzar
    I have read many of the good questions and answers around multi-core programming how-tos etc. I am familiar with concurrency, IPC, MPI etc but what I need is advice on how to measure speed-up which will help in making a business case of spending the time to write such code. Please don't answer with "well run it with single-core code then multi-core code and figure out the difference". This is neither a scientific nor a reliable way to measure performance improvement. If you know of tools that will do some of the heavy lifting please mention them. Answers pertaining to methodology will be more fitting but listing tools is ok as well.

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  • Project hosting vs. my own SVN

    - by BigG
    I'm working on different projects with some small teams (2-3 people for each). Those projects are about some scientific stuff, most (probably all) the code will be released under GPL after the publication of some results and we don't want to spend money for this. My first question is: should i keep my local SVN server or you know some good service for this? Both of them have some disadvantages and services like xp-dev.com looks pretty interesting but should i trust them? [i'll get only the free plan] Online services give you some tools for project management, what do you think about them?

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  • Faking a Single Address Space

    - by dsimcha
    I have a large scientific computing task that parallelizes very well with SMP, but at too fine grained a level to be easily parallelized via explicit message passing. I'd like to parallelize it across address spaces and physical machines. Is it feasible to create a scheduler that would parallelize already multithreaded code across multiple physical computers under the following conditions: The code is already multithreaded and can scale pretty well on SMP configurations. The fact that not all of the threads are running in the same address space or on the same physical machine must be transparent to the program, even if this comes at a significant performance penalty in some use cases. You may assume that all of the physical machines involved are running operating systems and CPU architectures that are binary compatible. Things like locks and atomic operations may be slow (having network latency to deal with and all) but must "just work".

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  • What is the term(s) used to describe programming language syntax?

    - by Mr Roys
    Is there an exact/correct term to describe this difference between the syntax/constructs of programming langauges e.g VB6 with its (if ... else ... endif) and C# with its curly braces for conditional statements. I'm using VB6 syntax and C# as examples since I'm more familiar with their syntax. For example, Visual Basic 6's syntax uses a more verbose, natural language like structure. If (id = 0) Then id = MyObject.Add(Me) Else Call MyObject.Update(Me) End If while C# has more concise syntax like: if (id == 0) { id = MyObject.Add(this); } else { MyObject.Update(this); } Conciseness? Natural languageness? Or is there a more "scientific" word for describing syntax?

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  • Partially parse C++ for a domain-specific language

    - by PierreBdR
    I would like to create a domain specific language as an augmented-C++ language. I will need mostly two types of contructs: Top-level constructs for specialized types or declarations In-code constructs, i.e. to add primitives to make functions calls or idiom easier The language will be used for scientific computing purposes, and will ultimately be translated into plain C++. C++ has been chosen as it seems to offer a good compromise between: ease of use, efficiency and availability of a wide range of libraries. A previous attempt using flex and bison failed due to the complexity of the C++ syntax. The existing parser can still fail on some constructs. So we want to start over, but on better bases. Do you know about similar projects? And if you attempted to do so, what tools would you use? What would be the main pitfalls? Would you have recommendations in term of syntax?

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  • Preserving NULL values in a Double Variable

    - by Sam
    Hi, I'm working on a vb.net application which imports from an Excel spreadsheet. If rdr.HasRows Then Do While rdr.Read() If rdr.GetValue(0).Equals(System.DBNull.Value) Then Return Nothing Else Return rdr.GetValue(0) End If Loop Else I was using string value to store the double values and when preparing the database statement I'd use this code: If (LastDayAverage = Nothing) Then command.Parameters.AddWithValue("@WF_LAST_DAY_TAG", System.DBNull.Value) Else command.Parameters.AddWithValue("@WF_LAST_DAY_TAG", Convert.ToDecimal(LastDayAverage)) End If I now have some data with quite a few decimal places and the data was put into the string variable in scientific notation, so this seems to be the wrong approach. It didn't seem right using the string variable to begin with. If I use a double or decimal type variable, the blank excel values come across as 0.0. How can I preserve the blank values? Thanks

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  • CouchDB: How to change view function via javascript?

    - by osti
    Hello Guys, I am playing around with CouchDB to test if it is "possible" [1] to store scientific data (simulated and experimental raw data + metadata). A big pro is the schema-less approach of CouchDB: we have to be very flexible with the metadata, as the set of parameters changes very often. Up to now I have some code to feed raw data, plots (both as attachments), and hierarchical metadata (as JSON) into CouchDB documents, and have written some prototype Javascript for filtering and showing. But the filtering is done on the client side (a.k.a. browser): The map function simply returns everything. How could I change the (or push a second) map function of a specific _design-document with simple browser-JS? I do not think that a temporary view would yield any performance gain... Thanks for your time and answers. [1]: of course it is possible, but is it also useful? feasible? reasonable?

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  • Image manipulation

    - by portoalet
    Hi, I am just wondering what kind of computing/programming language/frameworks are needed to produce images such as the one in http://www.erdas.com/ ? Programmatically, how does one produce the general spatial analysis images ? ps: I use java most of the time. Thanks

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  • Eye candy in OpenGL

    - by anon
    I'm interested in creating realtime visual special effects. I am limited to OpenGL (in particular, computing power of a MacBook Pro). I want to learn more about doing cool UI/special effects (think the "computers/displays" in Iron Man / Avatar). What are good books/resources for this? Thanks!

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  • Do you guys recommend any business magazine? [closed]

    - by kunjaan
    I want to get a birds eye view of the computing industry, read about company profiles, management decisions, new upcoming software companies, learn more about our industry and about the business aspect of my profession. Do you guys read recommend any good business magazines for me to increase my business acumen?

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  • Algorithm putting point into square with maximal minimum distance

    - by Mikulas Dite
    I'm stuck on this: Have a square. Put n points into this square so the minimal distance (not necessary the average distance) is the highest possible. I'm looking for an algorithm which would be able to generate the coordinates of all points given the count of them. Example results for n=4;5;6: Please don't mention computing-power based stuff such as trying a lot of combination and then nitpicking the right one and similar ideas.

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  • What parts of this book are outdated? "Design of the UNIX Operating System" by Maurice Bach, 1986

    - by blee
    I learned programming on the job via high-level languages. I'm trying to gain a better understanding of the lower-level workings of computing and picked up "Design of the UNIX Operating System" by Maurice Bach. What do I need to know in terms of which topics in this book may not be relevant to understanding Linux nuts and bolts? Is there a newer book or Linux-specific book that I should read instead? I really like the clarity of this particular book, though.

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  • selecting the pixels from an image in opencv

    - by ajith
    hi everyone, this is refined version of my previous question http://stackoverflow.com/questions/2602628/computing-matting-laplacian-matrix-of-an-image actually i want to do following operation... summation for all k|(i,j)?wk [(Ii-µk)*(Ij-µk)]...where wk is 3X3 window & µk is mean of wk...here i dont know how to select Ii & Ij separately from an image which is 2 dimensional[Iij]...or does the eqn means anything else??please someone help me..

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