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• Primary reasons why programming language runtimes use stacks?

  - by manuel aldana

  Many programming language runtime environments use stacks as their primary storage structure (e.g. see JVM bytecode to runtime example). Quickly recalling I see following advantages: Simple structure (pop/push), trivial to implement Most processors are anyway optimized for stack operations, so it is very fast Less problems with memory fragmentation, it is always about moving memory-pointer up and down for allocation and freeing complete blocks of memory by resetting the pointer to the last entry offset. Is the list complete or did I miss something? Are there programming language runtime environments which are not using stacks for storage at all?

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• Teaching a kid to type in order to start programming

  - by at

  My 5 year old wants to start programming, but he doesn't yet know how to type without looking for each letter 1 at a time. I know it's going to frustrate him to go so slow because of his typing speed. And it's not going to be fun looking for all the letters constantly... So what's the best way to get him to type fast? Clearly he'll need to type a lot of punctuation like semicolons, colons and symbols. So his little hands will have to get used to spreading over the keyboard... I did some google searches and found some very poor looking apps that focused on the letters.

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• efficient way to detect if an image is empty

  - by Jos

  Hi, I need a very fast method to detect if an image is empty. Im my case then all pixels are white and transparant. The images are png's. My current method is to load them in a memory bitmap and check each pixel value, but this is way to slow. Is there a more efficient way? This is my current code: 'Lock the bitmap bits. Dim bmpData As System.Drawing.Imaging.BitmapData = bmp.LockBits(rectBmp, _ Drawing.Imaging.ImageLockMode.ReadOnly, bmp.PixelFormat) Try Dim x As Integer Dim y As Integer For y = 0 To bmpData.Height - 1 For x = 0 To bmpData.Width - 1 If System.Runtime.InteropServices.Marshal.ReadByte(bmpData.Scan0, (bmpData.Stride * y) + (4 * x) + 3) <> 0 Then Return True Exit For End If Next Next Finally bmp.UnlockBits(bmpData) End Try

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• SQL Server 2008 Insert performance issue

  - by mithiya

  is there any way to increase performance of SQL server inserts, as you can see below i have used below sql 2005, 2008 and oracle. i am moving data from ORACLe to SQL. while inserting data to SQL i am using a procedure. insert to Oracles is very fast in compare to SQL, is there any way increase performance. or a better way to move data from Oracle to SQL (data size approx 100000 records an hour) please find below stats as i gathered, RUN1 and RUN2 time is in millisecond.

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• caching in memory on server

  - by zaharpopov

  I want to write web app with client Javascript and back-end server (Python). Client needs data from server frequently in AJAX way. Data in DB, and expensive to load for each request. However, in desktop app I would just load data from DB once to memory and then access it. In web app - the server code runs each time for request so I can't do it (each run has to load from DB to memory again). How can this work? Can a single process run on server or do I have to use something different here? An example is like auto-complete here on stackoverflow for tags - how is it implemented in the server for fast caching/loading?

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• Whats the best data-structure for storing 2-tuple (a, b) which support adding, deleting tuples and c

  - by bhups

  Hi So here is my problem. I want to store 2-tuple (key, val) and want to perform following operations: - keys are strings and values are Integers - multiple keys can have same value - adding new tuples - updating any key with new value (any new value or updated value is greater than the previous one, like timestamps) - fetching all the keys with values less than or greater than given value - deleting tuples. Hash seems to be the obvious choice for updating the key's value but then lookups via values will be going to take longer (O(n)). The other option is balanced binary search tree with key and value switched. So now lookups via values will be fast (O(lg(n))) but updating a key will take (O(n)). So is there any data-structure which can be used to address these issues? Thanks.

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• What's the cross-browser way to capture all single clicks on a button?

  - by sany

  What's the best way to execute a function exactly once every time a button is clicked, regardless of click speed and browser? Simply binding a "click" handler works perfectly in all browsers except IE. In IE, when the user clicks too fast, only "dblclick" fires, so the "click" handler is never executed. Other browsers trigger both events so it's not a problem for them. The obvious solution/hack (to me at least) is to attach a dblclick handler in IE that triggers my click handler twice. Another idea is to track clicks myself with mousedown/mouseup, which seems pretty primitive and probably belongs in a framework rather than my application. So, what's the best/usual/right way of handling this? (pure javascript or jQuery preferred)

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• Need help on nested loop of queries in php and mysql?

  - by mysqllearner

  Hi, I am trying to get do this: <?php $good_customer = 0; $q = mysql_query("SELECT user FROM users WHERE activated = '1'"); // this gives me about 40k users while($r = mysql_fetch_assoc($q)){ $money_spent = 0; $user = $r['user']; // Do queries on another 20 tables for($i = 1; $i<=20 ; $i++){ $tbl_name = 'data' . $i; $q2 = mysql_query("SELECT money_spent FROM $tbl_name WHERE user = '{$user}'"); while($r2 = mysql_fetch_assoc($q2)){ $money_spend += $r2['money_spent']; } if($money_spend > 1000000){ $good_customer += 1; } } } This is just an example. I am testing on localhost, for single user, it returns very fast. But when I try 1000, it takes forever, not even mentioned 40k users. Anyway to optimise/improve this code? EDIT: By the way, each of the others 20 tables has ~20 - 40k records

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• Operations on bytes in C#

  - by Hooch

  Hello. I'm writing application to control LEDS on LPT. I have everything working except this. This is one small function. I have sth like that: I want to build function that will take two argument and return one number: In actual code those binary numers will be in hex. I put them there like that so that it's easier for you to visualize it. Example1: arg1 = 1100 1100 arg2 = 1001 0001 retu = 0100 1100 Example2: arg1 = 1111 1111 arg2 = 0001 0010 retu = 1110 1101 Example3: arg1 = 1111 0000 arg2 = 0010 0010 retu = 1101 0000 I have no idea how this function should look like. I want it to be as fast as possible. I'll call this function 200 times per second.

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• How do you make Python wait so that you can read the output?

  - by anonnoir

  I've always been a heavy user of Notepad2, as it is fast, feature-rich, and supports syntax highlighting. Recently I've been using it for Python. My problem: when I finish editing a certain Python source code, and try to launch it, the screen disappears before I can see the output pop up. Is there any way for me to make the results wait so that I can read it, short of using an input() or time-delay function? Otherwise I'd have to use IDLE, because of the output that stops for you to read. (My apologies if this question is a silly one, but I'm very new at Python and programming in general.)

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• Recommendations for C# controls that can be used to create a hierarchical list of prioritised items?

  - by Mendokusai

  I need to be able to display and edit a hierarchical list of tasks in a C# app. It can either be a Windows form app, or ASP.NET. Basically, I want similar behaviour to the way Microsoft Project handles tasks. The control would need to: 1) Maintain a list of items made up of several fields 2) Each item can have a number of children (at least 3 levels of nesting) 3) It needs to be very easy to change the parents/children of an item 4) It needs to be very easy to edit the fields (as fast as changing cells in Excel) 5) It needs to be very easy to reorder the items by dragging and dropping or cut and paste 6) If I can easily connect the control to a database, even better Anyone got any recommendations for controls for me to look at?

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• Anyone Know a Great Sparse One Dimensional Array Library in Python?

  - by TheJacobTaylor

  I am working on an algorithm in Python that uses arrays heavily. The arrays are typically sparse and are read from and written to constantly. I am currently using relatively large native arrays and the performance is good but the memory usage is high (as expected). I would like to be able to have the array implementation not waste space for values that are not used and allow an index offset other than zero. As an example, if my numbers start at 1,000,000 I would like to be able to index my array starting at 1,000,000 and not be required to waste memory with a million unused values. Array reads and writes needs to be fast. Expanding into new territory can be a small delay but reads and writes should be O(1) if possible. Does anybody know of a library that can do it? Thanks!

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• Retrieving data from database. Retrieve only when needed or get everything?

  - by RHaguiuda

  I have a simple application to store Contacts. This application uses a simple relational database to store Contact information, like Name, Address and other data fields. While designing it, I question came to my mind: When designing programs that uses databases, should I retrieve all database records and store them in objects in my program, so I have a very fast performance or I should always gather data only when required? Of course, retrieving all data can only be done if it`s not too many, but do you use this approach when you make sure that the database will be small (< 300 records for example)? I have designed once a similar application that fetches data only when needed, but that was slow (using a Access database). Thanks for all help.

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• Connecting data to a GUI - OOP

  - by tau

  I have an application with several graphs and tables on it. I worked fast and just made classes like Graph and Table that each contained a request object (pseudo-code): class Graph { private request; public function setDateRange(dateRange) { request.setDateRange(dateRange); } public function refresh() { request.getData(function() { //refresh the display }); } } Upon a GUI event (say, someone changes the date range dropdown), I'd just call the setters on the Graph instance and then refresh it. Well, when I added other GUI elements like tables and whatnot, they all basically had similar methods (setDateRange and other things common to the request). What are some more elegant OOP ways of doing this? The application is very simple and I don't want to over-architect it, but I also don't want to have a bunch of classes with basically the same methods that are just routing to a request object. I also don't want to set up each GUI class as inheriting from the request class, but I'm open to any ideas really.

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• How do I Benchmark RESTful Service with Variable Parameters?

  - by Eli

  I'm currently working on benchmarking a RESTful service I've made, and part of that is making sure it runs in a reasonable amount of times for a large array of parameters. For example, let's say I have RESTful API of the form some_site.com/item?item_id=y. In that case to be sure my service is working as fast as I'd like it to work, I'd want to try out many values for y one by one, preferably coming from some text file. I can't figure out any way of doing this in ab or httperf. I'm open to using a different benchmarking program if I have, but would prefer something simple and light. What I want to do seems like something pretty standard, so I'm guessing there must already be a program that let's me do it, but an hour or so of googling hasn't gotten me an answer. Ideas?

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• Trying to find a good javascript function for hmac-sha1

  - by Darxval

  So i have been searching the web for a javascript source for an Hmac-sha1 algorithm. I saw Crypto's but i cant seem to get it to work, mainly because it has no idea what crypto means. (i copied the .js script functions into my script file) http://code.google.com/p/crypto-js/ I have my base64 encoded function already. that i got from here: http://nerds-central.blogspot.com/2007/01/fast-scalable-javascript-and-vbscript.html btw this for a twitter application using the new OAuth system. any help or links to where i can find anything on this would be helpful If you need me to elaborate let me know. thank you!

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• packing fields of a class into a byte array in c#

  - by alex

  Hi all: I am trying to create a fast way to convert c# classes into byte array. I thought of serializing the class directly to a byte array using an example I found: // Convert an object to a byte array private byte[] ObjectToByteArray(Object obj) { if(obj == null) return null; BinaryFormatter bf = new BinaryFormatter(); MemoryStream ms = new MemoryStream(); bf.Serialize(ms, obj); return ms.ToArray(); } But the byte array I got contains some other information that are not related to the fields in the class. I guess it is also converting the Properties of the class. Is there a way to serialize only the fields of the class to a byte array? Thanks

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• Is Sphinx better than LaTex in writing manuals/books?

  - by Masi

  Only a few people recommended to use Sphinx at the beginning of the year. Sphinx has developed rather fast recently. I noted today that Sage has made a change from direct editing with LaTex to Sphinx. This is evident in William Stein's answer on 2nd April about Sage's tutorial The tutorial is not a latex document anymore. It's an entirely different Sphinx document that can output pdf. It suggests me that Sphinx may be at a level such that it is suitable for me. Is Sphinx better than LaTex in writing manuals/books?

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• How to I correctly add brackets to this code

  - by Mohammad

  This code removes whites paces, (fyi: it's credited to be very fast) function wSpaceTrim(s){ var start = -1, end = s.length; while (s.charCodeAt(--end) < 33 ); //here while (s.charCodeAt(++start) < 33 ); //here also return s.slice( start, end + 1 ); } The while loops don't have brackets, how would i correctly add brackets to this code? while(iMean){ like this; } Thank you so much!

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• PHP / javascript live chat using too much bandwidth

  - by David

  So I am learning about javascript, so I am making a live chat system with PHP and javascript. I have it so the javascript refreshes the log (each message gets logged in a file on the server), and it refreshes every second. Im using firebug to monitor the resource usage, and I see under the net tab each times its updated, and the bytes add up really fast. I know I can change it to update less, but is there a way that when a user on the other end I'm talking to, when the send a message, it gets sent to the server, then an alert gets sent to me saying that the chatlog needs to update somehow. That way it only updates when the log is updated. let me know, thanks

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• Multiple indexes for a Java Collection - most basic solution?

  - by chris_l

  Hi, I'm looking for the most basic solution to create multiple indexes on a Java Collection. Required functionality: When a Value is removed, all index entries associated with that value must be removed. Index lookup must be faster than linear search (at least as fast as a TreeMap). Side conditions: It should ideally work with JavaSE (6.0) alone - no extra libraries, if possible. If necessary, then only small (not something like Lucene), common and well tested libraries. No database! Of course, I could write a class that manages multiple Maps myself. But I'd like to know, if it can be done without - while still getting a simple usage similar to using a single indexed java.util.Map. Thanks, Chris

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• jquery change function into code for plugin

  - by jaap Klevering

  Help would be greatly appreciated. What is the correct markup that would change this function into a plugin. I tried, but cant make it to work. $(document).ready(function(){ $('ul.tabNav a').click(function() { var curChildIndex = $(this).parent().prevAll().length + 1; $(this).parent().parent().children('.current').removeClass('current'); $(this).parent().addClass('current'); $(this).parent().parent().next('.tabContainer').children('.current').slideUp('fast',function() { $(this).removeClass('current'); $(this).parent().children('div:nth-child('+curChildIndex+')').slideDown('normal',function() { $(this).addClass('current'); }); }); return true; }); });

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• C: Pointers to any type?

  - by dragme

  I hear that C isn't so type-safe and I think that I could use that as an advantage for my current project. I'm designing an interpreter with the goal for the VM to be extremely fast, much faster than Ruby and Python, for example. Now I know that premature optimization "is the root of all evil" but this is rather a conceptual problem. I have to use some sort of struct to represent all values in my language (from number over string to list and map) Would the following be possible? struct Value { ValueType type; void* value; } I would store the actual values elsewhere, e.g: a separate array for strings and integers, value* would then point to some member in this table. I would always know the type of the value via the type variable, so there wouldn't be any problems with type errors. Now: Is this even possible in terms of syntax and typing?

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• Treating a fat webservice in .net 3.5 c#

  - by Chris M

  I'm dealing with an obese 3rd party webservice that returns about 3mb of data for a simple search results, about 50% of the data in that response is junk. Would it make sense then to remap this data to my own result object and ditch the response so I'm storing 1-2 mb in memory for filtering and sorting rather than using the web-responses own object and using 2-4 or am I missing a point? So far I've been accessing the webservice from a separate project and using a new class to provide the interaction and to handle the persistence so my project looks like this |- Web (mvc2 proj) |- DAL (database/storage fluent-nhibernate) |- SVCGateway (interaction layer + webservice related models) |- Services -------------- |- Tests |- Specs I'm trying to make the application behave fast and I also need to store the result set temporarily in case a customer goes to view the product and wants to go back to the results. (Service returns only 500 of possible 14K results). So basically I'm looking for confirmation that I'm doing the right thing in pushing the results into my own objects or if I'm breaking some rule or even if there's a better way of handling it. Thanks

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• Advanced queries in HBase

  - by Teflon Ted

  Given the following HBase schema scenario (from the official FAQ)... How would you design an Hbase table for many-to-many association between two entities, for example Student and Course? I would define two tables: Student: student id student data (name, address, ...) courses (use course ids as column qualifiers here) Course: course id course data (name, syllabus, ...) students (use student ids as column qualifiers here) This schema gives you fast access to the queries, show all classes for a student (student table, courses family), or all students for a class (courses table, students family). How would you satisfy the request: "Give me all the students that share at least two courses in common"? Can you build a "query" in HBase that will return that set, or do you have to retrieve all the pertinent data and crunch it yourself in code?

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