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  • Performance optimization strategies of last resort?

    - by jerryjvl
    There are plenty of performance questions on this site already, but it occurs to me that almost all are very problem-specific and fairly narrow. And almost all repeat the advice to avoid premature optimization. Let's assume: the code already is working correctly the algorithms chosen are already optimal for the circumstances of the problem the code has been measured, and the offending routines have been isolated all attempts to optimize will also be measured to ensure they do not make matters worse What I am looking for here is strategies and tricks to squeeze out up to the last few percent in a critical algorithm when there is nothing else left to do but whatever it takes. Ideally, try to make answers language agnostic, and indicate any down-sides to the suggested strategies where applicable. I'll add a reply with my own initial suggestions, and look forward to whatever else the SO community can think of.

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  • What software analogies have helped you?

    - by Galwegian
    I have often enjoyed the use of analogies in understanding a software scenario or problem. For example, to understand the concept of public key encryption, the 'locked mailbox' analogy or similar is often used as an aid: An analogy for public-key encryption is that of a locked mailbox with a mail slot. The mail slot is exposed and accessible to the public; its location (the street address) is in essence the public key. Anyone knowing the street address can go to the door and drop a written message through the slot; however, only the person who possesses the key can open the mailbox and read the message. My question is: What analogies have you used or heard of in your career that have given you that "Eureka" moment with a complex concept? EDIT: If you have a good one, don't just state the name, please share with the group!

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  • CodeRush Tricks of the Trade

    - by dr. evil
    I was using CodeRush quite while ago and now I'm planning to use it again. I've install the trial but I forgot all cool features except Alt + Home (drop a marker). And when you don't know some cool tricks it's really like burning money (since it's not cheap for personal use) What do you like about it? What are your best features? My best feature is marker: Alt + Home (and use escape to go back) P.S Dear Devxpress, if you think I helped you by asking this question I can accept some donations, a free license of CodeRush would be nice! Currently What I like most ps/pi etc. shortcut to create properties cc to create constructors pressing tab to navigate between the references F12 to find references in new cool window Ctrl + Shift + . for recent files Ctrl + Shift + Q for jumping to any function / class fe/fi for "for loops"

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  • Hidden Features and Dark Corners of STL?

    - by Andrei
    C++ developers, all know the basics of C++: Declarations, conditionals, loops, operators, etc. Some of us even mastered the stuff like templates, object model, complex I/O, etc. But what are the most hidden features or tricks or dark corners of C++/STL that even C++ fans, addicts, and experts barely know? I am talking about a seasoned C++ programmer (be she/he a developer, student, fan, all three, etc), who thinks (s)he knows something 99% of us never heard or dreamed about. Something that not only makes his/her work easier, but also cool and hackish. After all, C++ is one of the most used programming languages in the world, thus it should have intricacies that only a few privileged know about and want to share with us. Boost is welcome too! One per post with an example please P.S Examples are important for other developers to copy and paste!

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  • Javascript tricks

    - by ayush
    What does the following code mean - <a href="javacsript:;" onClick="addItem(160)">some link</a> My basic doubt is which script is run when we click on the link

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  • What are some programming questions (or mistakes) you get wrong only as you get better?

    - by BlueRaja
    In programming, as many professions, there are mistakes you'll make now that you may not have made as a beginner. For instance, consider pointers: In C++, is there any difference between arrays and pointers? The beginner will say yes, they are two completely different concepts, and treat them as such. The intermediate programmer (having learned that arrays are pointers internally) will tell you no, they are the same thing, and may miss some crucial bugs by interchanging them all willy-nilly. The expert, however, will again say they are different things (ex. see here or here). What other questions/mistakes are like this?

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  • How to Convert arrays or SimpleXML-Objects into an XML-String

    - by streetparade
    I want to create a xml from a given string, i have a function but i didn't wrote it.It seems a bit cryptical too. Can please some one review it and give me some Ideas, how it could be written clearer for everybody? /** * Converts arrays or SimpleXML-Objects into an XML-String * @params mixed Accepts an array or xml string with data to Post * @params integer DO NOT PROVIDE. Internal Usage for recursion only */ private function mixedDataToXML($data, $level = 1) { if(!$data){ return FALSE; } if(is_array($data)) { $xml = ''; if ($level==1) { $xml .= '<?xml version="1.0" encoding="ISO-8859-1"?>'."\n"; } foreach ($data as $key => $value) { $key = strtolower($key); if (is_array($value)) { $multi_tags = false; foreach($value as $key2=>$value2) { if (is_array($value2)) { $xml .= str_repeat("\t",$level)."<$key>\n"; $xml .= $this->mixedDataToXML($value2, $level+1); $xml .= str_repeat("\t",$level)."</$key>\n"; $multi_tags = true; } else { if (trim($value2)!='') { if (htmlspecialchars($value2)!=$value2) { $xml .= str_repeat("\t",$level). "<$key><![CDATA[$value2]]>". "</$key>\n"; } else { $xml .= str_repeat("\t",$level). "<$key>$value2</$key>\n"; } } $multi_tags = true; } } if (!$multi_tags and count($value)>0) { $xml .= str_repeat("\t",$level)."<$key>\n"; $xml .= $this->mixedDataToXML($value, $level+1); $xml .= str_repeat("\t",$level)."</$key>\n"; } } else { if (trim($value)!='') { if (htmlspecialchars($value)!=$value) { $xml .= str_repeat("\t",$level)."<$key>". "<![CDATA[$value]]></$key>\n"; } else { $xml .= str_repeat("\t",$level). "<$key>$value</$key>\n"; } } } } return $xml; }else{ return (string)$data; } }

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  • Fast dot product for a very special case

    - by psihodelia
    Given a vector X of size L, where every scalar element of X is from a binary set {0,1}, it is to find a dot product z=dot(X,Y) if vector Y of size L consists of the integer-valued elements. I suggest, there must exist a very fast way to do it. Let's say we have L=4; X[L]={1, 0, 0, 1}; Y[L]={-4, 2, 1, 0} and we have to find z=X[0]*Y[0] + X[1]*Y[1] + X[2]*Y[2] + X[3]*Y[3] (which in this case will give us -4). It is obvious that X can be represented using binary digits, e.g. an integer type int32 for L=32. Then, all what we have to do is to find a dot product of this integer with an array of 32 integers. Do you have any idea or suggestions how to do it very fast?

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  • Navigating through code with keyboard shortcuts

    - by MarceloRamires
    I'm starting to feel the need to run fastly through code with keyboard shortcuts, to arrive faster where I want to make any changes (avoiding use of mouse or long times holding [up], [left], [right] and [down]). I'm already using some: [home] - first position in current line [end] - last position in current line [ctrl] + [home] - first line of the entire code [ctrl] + [end] - last line of the entire code [pageup] - same vertical position, one screen above [pagedown] - same vertical position, one screen below [ctrl] + [pageup] - first line in current screen [ctrl] + [end] - last line in current screen [ctrl] + [left/right] - skipping word per word What have you got ? I use Visual Studio. (but I'm open to any answer, as I maybe can use others soon) obs: I've searched through stackoverflow and didn't find a nice question with this content, nor a list of keyboard code searching. If it's repeated, I'm sorry for not finding it, I'm here in my best intentions. This question is NOT about any shortcuts, and not only about visual studio, it's about running through code with shortcuts. Answers that suit the question so far: [Ctrl] + [-] - jumps to last cursor position [Ctrl] + [F3] - Jumps to next occurance of the word the curson is in [Shift] + [F3] - Same as the above, backwards. [F12] - Goes to definition of method/variable the cursor is in [Ctrl] + [ ] ] - Jumps to matching brace and select I'll ad more as there are answers.

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  • C++: select argmax over vector of classes w.r.t. arbitrary expression

    - by karpathy
    Hello, I have trouble describing my problem so I'll give an example: I have a class description that has a couple of variables in it, for example: class A{ float a, b, c, d; } Now, I maintain a vector<A> that contains many of these classes. What I need to do very very often is to find the object inside this vector that satisfies that one of it's parameters is maximal w.r.t to the others. i.e code looks something like: int maxi=-1; float maxa=-1000; for(int i=0;i<vec.size();i++){ res= vec[i].a; if(res > maxa) { maxa= res; maxi=i; } } return vec[maxi]; However, sometimes I need to find class with maximal a, sometimes with maximal b, sometimes the class with maximal 0.8*a + 0.2*b, sometimes I want a maximal a*VAR + b, where VAR is some variable that is assigned in front, etc. In other words, I need to evaluate an expression for every class, and take the max. I find myself copy-pasting this everywhere, and only changing the single line that defines res. What makes it even more complicated is that even the name of the vector changes. Sometimes it's vec, sometimes it can be something else. I have many vectors that contain A's. This could be changed if this makes the problem too hard. Is there some nice way to avoid this insanity in C++? What's the neatest way to handle this? Thank you!

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  • Best anti boss tricks to hide your private page navigation from your desktop.

    - by systempuntoout
    This question is slightly related to programming and it's kinda lame, i know; but i saw many funny things in these years and i'm looking for new tricks from you. I'm talking about methods to fast-hide\camouflage not job related web pages on your desktop when boss arrives like a ghost\ninja behind your shoulders. I know how much can be frustrating, programming hard for ten hours and then been caught by your boss watching XKCD during a 2 minutes break. I think the most common anti boss trick is the evergreen CTRL+TAB, but you have to be fast and your left hand has to be near the keyboard. I saw pitch black brightness on Lcd (how can you pretend to program on that?) or custom sized browser to fit a little space just below the IDE. My favourite one at the moment is using fire gesture plugin with FF; with a micro gesture you can hide FF to your tray in a blink of an eye. Do you have any trick to share?

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  • Looking for good Lisp code to read

    - by fl3x
    I'm currently trying to get proficient in Common Lisp and to learn some of the tricks for writing compact, clear and beautiful code in it. So, I want to know if you have any sources of good Common Lisp, preferably free and online but books are also OK.

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  • Should I use my models in a library?

    - by Piers
    I've got my auth library in codeigniter which accesses the database to check to see if the email/password combination is correct. If I'm sticking to the MVC practice, should I move the function that interacts with the database to my model, or is it best practice to leave it where it is so I can use it in the future? Doesn't make much difference to me, other than the fact I'd have to re-write the library and create the function in my model, but if that's the way it should be then so be it.

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  • Can I use SQL to update multiple rows with multiple values from another table?

    - by stu
    I've got a one to many table with ids and traits for those users. I want to copy one user's settings to another. userid trait onoff ------ ----- ----- 1 1 on 1 2 on 1 3 on 1 4 on 2 1 off 2 2 off 2 3 off 2 4 off So I want to copy the onoff values from user 1 to 2, so that user2 has everything on when I'm done. update table set onoff = (select onoff from table where userid=1) where userid=2 that's the basic idea, but obviously doesn't work. I imagine I want the server to think in terms of a correlated subquery, but the outer part isn't a query, it's an update. Is this even possible in one step?

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  • what's wrong in File.Exist() method?

    - by Arseny
    Reading some answers with code samples I notice that those where this method mentioned are subjected to criticism. I'm using this method in my code. So I'd like to know if someone give me detailed response whuy this method is not recomemnded and what alternative approaches are?

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  • Things in .NET Framework 4 that every programmer should know

    - by Faruz
    I recently moved to Visual Studio 2010 and upgraded my website to work with .NET Framework 4. (From VS 2008 - Framework 3.5) What are things I need to know to improve site speed, readability or memory use? For example, I found out that when I use AJAX ScriptManager, one of it's new properties is EnableCDN which enables me to load AJAX .js files from Microsoft CDN.

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  • Catch access to undefined property in JavaScript

    - by avri
    The Spider-Monkey JavaScript engine implements the noSuchMethod callback function for JavaScript Objects. This function is called whenever JavaScript tries to execute an undefined method of an Object. I would like to set a callback function to an Object that will be called whenever an undefined property in the Object is accessed or assigned to. I haven't found a noSuchProperty function implemented for JavaScript Objects and I am curios if there is any workaround that will achieve the same result. Consider the following code: var a = {}; a.__defineGetter__("bla", function(){alert(1);return 2;}); alert(a.bla); It is equivalent to [alert(1);alert(2)] - even though a.bla is undefined. I would like to achieve the same result but to unknown properties (i.e. without knowing in advance that a."bla" will be the property accessed)

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  • What is the most under-valued part of .NET?

    - by Jan Bannister
    The .NET framework is massive. I've used it for years and I've still not used most of it. I'd like to expand my knowledge of the Framework's backwaters but just reading thought it seems daunting. So I thought I'd tap up the Stack Overflow community first. What part have you found to be the most surprisingly useful? What's your favourite obscure namespace? And conversely are there any shiny bits that are best avoided?

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  • what are the limitations of mobile phones and web development

    - by Kieran
    simple really.. I am have been asked to do a mobile site (straight html + css (+ maybe jquery mobile later on)). The site will need to support the new type smart phone and the old type Nokia/(Symbian OS) with the web browser. Doubts and reservations aside as to anyone without a smart phone would bother visiting this site it still needs to support it. My first question is do older phones support PNG images and transparancey... But this has led me to a much broader question of what are some of the limitations of developing for older phone platforms is there anything that has caught mobile web devs out and had them scratching their head for an afternoon.. what are the limitations of mobile phones?

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