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  • Does anyone use AMPL anymore

    - by steven
    I took a class on "Intelligent Decision Making" (which was mostly an Problem Optimization class). In the class we learned about AMPL and how to extend the solvers. I haven't heard much about it lately, nor have I seen job listings for it. My question is: Is AMPL still in use anymore? If so what is it being used for? Yes, I do understand that AMPL can be replaced with Matlab, however AMPL is free and Matlab isn't even close.

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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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  • mysql query optimisation

    - by Bharanikumar
    i have around (1,049,906 total, Query took 0.0005 sec) in my x table , If i simply retrieve trying to retrive the particular field records , Its tooks hardly 6 mins , This is my query SELECT CUSTOMER_CODE FROM X_TBL ; CUSTOMER_CODE = UNIQUE THE ABOVE QUERY TOOK 6MIN , Tel me optimization tips for this , Also in some situation to search customer , i used the CUSTOMER_CODE in like , select CUSTOMER_CODE from X_TBL WHERE CUSTOMER_CODE LIKE "$KEY_WORD%" Regards Bharanikumar

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  • What are the DB smells?

    - by Jonas Byström
    We all know 'code smells', but what are the fundamental 'database smells'? I'm a DB n00b, but I'll give an example of something that I find fishy. It seems to me like when I have to join 6-8 tables together to optimize our loading that we have a DB smell? Or would that be a pretty 'normal' database layout? (Sure, early optimization is the root of all evil, but this seems to me like early pessimisation, not to mention the cumbersomeness?)

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  • When should I use temporary variables?

    - by Kyle
    Specifically, I'm wondering which of these I should write: shared_ptr<GuiContextMenu> subMenu = items[j].subMenu.lock(); if (subMenu) subMenu->setVisible(false); or: if (items[j].subMenu.lock() items[j].subMenu.lock()->setVisible(false); I am not required to follow any style guidelines. After optimization, I don't think either choice makes a difference in performance. What is generally the preferred style and why?

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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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  • MonoTouch - foreach vs for loops (performance)

    - by ifwdev
    Normally I'm well aware that a consideration like this is premature optimization. Right now I have some event handlers being attached inside a foreach loop. I am wondering if this style might be prone to leaks or inefficient memory use due to closures being created. Is there any validity to this thinking?

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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