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  • Are +=, |=, &= etc atomic?

    - by SF.
    Are the "modify" operators like +=, |=, &= etc atomic? I know ++ is atomic (if you perform x++; in two different threads "simultaneously", you will always end up with x increased by 2, as opposed to x=x+1 with optimization switched off.) What I wonder is whether variable |= constant, and the likes are thread-safe or do I have to protect them with a mutex? (...or is it CPU-dependent? In this case, how is it on ARM?)

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  • [objective C] IPhone question about UIImageView memory menagement

    - by BQuadra
    Hi, i have a UIImageView of 1024x768 (the room of my game) and other various UIIMageView on it (the object of my game). The iPhone screen is smaller than the room (UIImageView 1024x768) .. i want to understand if the iPhone's system automatically intercepts the graphic elements outside the visible area of Room (the player's view) and unload temporarily (for memory optimization) or i must do this by hand?? thanks

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  • Which programming language to choose? (for a specific problem/domain, details inside)

    - by Bijan
    I am building a trading portfolio management system that is responsible for production, optimization, and simulation of non-high frequency trading portfolios (dealing with 1min or 3min bars of data, not tick data). I plan on employing Amazon web services to take on the entire load of the application. I have four choices that I am considering as language. a) Java b) C++ c) C# d) Python Here is the scope of the extremes of the project scope. This isn't how it will be, maybe ever, but it's within the scope of the requirements: Weekly simulation of 10,000,000 trading systems. (Each trading system is expected to have its own data mining methods, including feature selection algorithms which are extremely computationally-expensive. Imagine 500-5000 features using wrappers. These are not run often by any means, but it's still a consideration) Real-time production of portfolio w/ 100,000 trading strategies Taking in 1 min or 3 min data from every stock/futures market around the globe (approx 100,000) Portfolio optimization of portfolios with up to 100,000 strategies. (rather intensive algorithm) Speed is a concern, but I believe that Java can handle the load. I just want to make sure that Java CAN handle the above requirements comfortably. I don't want to do the project in C++, but I will if it's required. The reason C# is on there is because I thought it was a good alternative to Java, even though I don't like Windows at all and would prefer Java if all things are the same. Python - I've read somethings on PyPy and pyscho that claim python can be optimized with JIT compiling to run at near C-like speeds.... That's pretty much the only reason it is on this list, besides that fact that Python is a great language and would probably be the most enjoyable language to code in, which is not a factor at all for this project, but a perk. To sum up: - real time production - weekly simulations of a large number of systems - weekly/monthly optimizations of portfolios - large numbers of connections to collect data from There is no dealing with millisecond or even second based trades. The only consideration is if Java can possibly deal with this kind of load when spread out of a necessary amount of EC2 servers. Thank you guys so much for your wisdom.

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  • Travelling Salesman Problem Constraint Representation

    - by alex25
    Hey! I read a couple of articles and sample code about how to solve TSP with Genetic Algorithms and Ant Colony Optimization etc. But everything I found didn't include time (window) constraints, eg. "I have to be at customer x before 12am)" and assumed symmetry. Can somebody point me into the direction of some sample code or articles that explain how I can add constraints to TSP and how I can represent those in code. Thanks!

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  • JVM performance test suite

    - by pierr
    Hi, I have just ported phoneME to our MIPS platform. I feel it runs not that fast; however, is there any performance test suite I can run against to get some quantitative measurement of the performance? I might need to pick some weak points for optimization. In addition, what are common criterions used to evalute a JVM ?

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  • Linq Queries converting to lambda expressions ?

    - by Freshblood
    Hello from item in range where item % 2 ==0 select i ; is converting to lamda expressions as below range.where(item % 2 ==0).select(x=>x). I feel that first way of linq is translating next one and if it is ,so is there any optimization like this range.where(item & 2 == 0) instead of other one ?

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  • Optimizing python link matching regular expression

    - by Matt
    I have a regular expression, links = re.compile('<a(.+?)href=(?:"|\')?((?:https?://|/)[^\'"]+)(?:"|\')?(.*?)>(.+?)</a>',re.I).findall(data) to find links in some html, it is taking a long time on certain html, any optimization advice? One that it chokes on is http://freeyourmindonline.net/Blog/

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  • What's the good of IDE's auto generated @override annotation ?

    - by Tony
    I am using eclipse , when I use shortcut to generate override implementations , there is an override annotation up there , I am using JDK 6 , this is all right , but under JDK 5 this annotation will cause an error, so I want to ask , if this annotation is completely useless ? Will compiler do some kind of optimization using this annotation ?

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  • How do "modern JVMs" differ from older JVMs?

    - by Lord Torgamus
    Here's a phrase that I heard a lot throughout high school and university computer science classes: "That's not an issue for modern JVMs." Usually this would come up in discussions about overall performance or optimization strategies. It was always treated as a kind of magical final answer, though, as if it makes issues no longer worth thinking about. And that just leads me to wonder: what are the differences between the prototypical "modern JVM" and older JVMs, really?

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  • Improve long mysql query

    - by John Adawan
    I have a php mysql query like this $query = "SELECT * FROM articles FORCE INDEX (articleindex) WHERE category='$thiscat' and did>'$thisdid' and mid!='$thismid' and status='1' and group='$thisgroup' and pid>'$thispid' LIMIT 10"; As optimization, I've indexed all the parameters in articleindex and I use force index to force mysql to use the index, supposedly for faster processing. But it seems that this query is still quite slow and it's causing a jam and maxing out the max mysql connection limit. Let's discuss how we can improve on such long query.

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  • Improve long mysql query

    - by John Adawan
    I have a php mysql query like this $query = "SELECT * FROM articles FORCE INDEX (articleindex) WHERE category='$thiscat' and did>'$thisdid' and mid!='$thismid' and status='1' and group='$thisgroup' and pid>'$thispid' LIMIT 10"; As optimization, I've indexed all the parameters in articleindex and I use force index to force mysql to use the index, supposedly for faster processing. But it seems that this query is still quite slow and it's causing a jam and maxing out the max mysql connection limit. Let's discuss how we can improve on such long query.

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  • Ray-triangle intersetion

    - by gamemaker
    Hello! How can I test intersesion ray and triangle, and if it exist how to get distance from ray origin to intersection point?? What optimization I can use, if in my program I've got to check 1 ray to ~10000 triangles ??

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  • C: performance of assignments, binary operations, et cetera...

    - by Shinka
    I've heard many things about performance in C; casting is slow compared to normal assignments, functional call is slow, binary operation are much faster than normal operations, et cetera... I'm sure some of those things are specific to the architecture, and compiler optimization might make a huge difference, but I would like to see a chart to get a general idea what I should do and what I should avoid to write high-performance programs. Is there such a chart (or a website, a book, anything) ?

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  • faster strlen ?

    - by Jack
    Typical strlen() traverse from first character till it finds \0. This requires you to traverse each and every character. In algorithm sense, its O(N). Is there any faster way to do this where input is vaguely defined. Like: length would be less than 50, or length would be around 200 characters. I thought of lookup blocks and all but didn't get any optimization.

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  • Does acos, atan functions in stl uses lots of cpu cycles

    - by jan
    Hi all, I wanted to calculate the angle between two vectors but I have seen these inverse trig operations such as acos and atan uses lots of cpu cycles. Is there a way where I can get this calculation done without using these functions? Also, does these really hit you when you in your optimization?

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  • How I can Optimize this mySQL transaction within java code?

    - by worldpython
    Dear All, I am new to MySql database. I've large table(ID,...). I select ID frequently with java code and.And that make a heavy load on transaction select from tableName where ID=someID notes: 1.Database could be 100,000 records 2.I can't cache result 3.ID is a primary key 4.I try to optimize time needed to return result from query. Any ideas for optimization ? thanks in advance

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  • Does Microsoft make available the .obj files for its CRT versions to enable whole program optimizati

    - by Leeks and Leaks
    Given the potential performance improvements from LTCG (link time code generation, or whole program optimization), which requires the availability of .obj files, does Microsoft make available the .obj files for the various flavors of its MSVCRT releases? One would think this would be a good place for some potential gain. Not sure what they have to lose since the IL that is generated in the .obj files is not documented and processor specific.

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  • Database: Pipelined Functions

    - by Rachel
    I am new to the concept of Pipeline Functions. I have some questions regarding From Database point of view: What actually is Pipeline function ? What is the advantage of using Pipeline Function ? What challenges are solved using Pipeline Function ? Are the any optimization advantages of using Pipeline Function ? Thanks.

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  • C++[MSVC2010]: How does switch compile and how optimized and fast is it?

    - by ekul
    As I found out that I can use only numerical values in C++'s switch statements, I thought that there then must be some deeper difference between it and a bunch of if-else's. Therefore I asked myself: (How) does switch differ from if-elseif-elseif in terms of runtime speed, compile time optimization and general compilation? I'm mainly speaking of MSVC here.

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