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• asynchronous calls in asp.net

  - by lockedscope

  in this sample, two threads created; a worker thread created by BeginInvoke and an I/O completion thread created by SendAsync method. but another author in his UnsafeQueueNativeOverlapped example, don't recommend this. i want to use SendAsync or ...Async in an asp.net page and i want to use PageAsyncTask. however, its BeginEventHandler requires AsyncResult to be returned which SendAsync does not return. afaik, event based async pattern is the most recommended way so how could we call SendAsync or any ...Async methods without creating two threads and hurting the performance?

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• Keeping Computer Science Writing Accessible and Eloquent

  - by Federer

  This question is particularly aimed at descriptions and explanations of what is happening in a computer program, as well as any general advice or approaches for undertaking technical reports in Computer Science at both undergraduate and graduate levels. You see, I am having particular difficulty in the best way to explain what is happening. As in, given any given program from a multi-agent system to a standard webservice, the best and most eloquent way to say exactly what is going on, the logic behind it and it's respective justifications. Should I avoid saying class names? Avoid specifying methods? Keep referring to class variables and any particular references? I'm banging my head against the wall at trying to keep a solid technical foundation and making it accessible to people of all backgrounds. Apologies for the rather vague question. Cheers.

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• How to I count key collisions when using boost::unordered_map?

  - by Nikhil

  I have a data structure with 15 unsigned longs, I have defined a hash function using hash_combine as follows: friend std::size_t hash_value(const TUPLE15& given) { std::size_t seed = 0; boost::hash_combine(seed, val1); boost::hash_combine(seed, val2); ... return seed; } I insert a large number of values into a boost::unordered_map but the performance is not good enough. Probably, I could do better with an alternative hashing function. To confirm this, I need to check how many collisions I am getting. How do I do this?

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• m:n relationship must have properties?

  - by nax

  I'm doing a E/R model for a project. I finished the ER model and, for me, all is okay. Maybe not perfect, but it's okay. When I gave the ER model to my teacher, he told me this: "the m:n relations MUST HAVE some properties" He said if the m:n relationship doesn't have the properties it will be wrong. In my opinion m:n doesn't need forcer attributes to the relationship, but if you have someone that can fit in it, just put there. What do you think? Who is wrong in this, me, or my teacher? NOTE: Reading again, it seems what he said was not due to my ER diagram, but was a general statement. The diagram I gave him doesn't have relations yet, so there where just entities and atributes.

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• What factors could cause the scalability issue on a 10-core CPU?

  - by JackWM

  I am tuning the performance of parallel Java programs. And want to check the impacts from the Architecture. I'm look into the Intel 10-core CPU, Intel(R) Xeon(R) CPU E7-L8867. I found my program only scales up to 5 cores. What could be the causes? I'm considering the Architecture effects. e.g. memory contention? More specifically, Are the 10 cores symmetric to each other? How many memory controllers does it have?

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• ImageView source scaling done right. How?

  - by Aleksey Malevaniy

  Scope Image bitmap have to be shown as imageView.setImageBitmap(bitmap) and scaled to fit UI. This could be done via: bitmap = Bitmap.createScaledBitmap(bitmap, newWidth, newHeight, true); xml's ImageView attributes such as android:layout_width="newWidth" android:layout_height="newHeight" android:adjustViewBounds="true" android:scaleType="fitCenter" Problem Which way is better for performance? I prefer xml 'cause this is UI specific problem and I prefer to use xmls for UI definition. Also we set width/height values in dp, it means we have the same UI for different screens. Thanks!

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• C++ design with static methods

  - by user231536

  I would like to define as class X with a static method: class X { static string get_type () {return "X";} //other virtual methods } I would like to force classes which inherit from X to redefine the get_type() method and return strings different from "X" (I am happy if they just redefine get_type for now). How do I do this? I know that I cannot have virtual static methods. Edit: The question is not about the type_id, but in general about a static method that should be overriden. For example class X { static int getid() {return 1;} }

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• Php getting too many connections error from MySQL

  - by uzioriluzan

  Hello everyone, I am using MySQL and PHP with 2 application servers and 1 database server. With the increase of the number of users (around 1000 by now), I'm getting the following error : SQLSTATE[08004] [1040] Too many connections The parameter "max_connections" is set to "1000" in my.cnf and "mysql.max_persistent" is set to -1 in php.ini. There are at most 1500 apache processes running at a time since the "MaxClients" apache parameter is equal to 750 and we have 2 application servers. Should I raise the "max_connections" to 1500 as indicated in here? Or should I set "mysql.max_persistent" to 750 (we use PDO with persistent connections for performance reasons since the database server is not the same as the application servers)? Or should I try something else? Thanks in advance!

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• Toastr.js notifications as modal notfication

  - by Maxsteel

  I know it's not what toastr (or toast notifs in general) are meant to be used for, but I want to use them as a modal notification. My idea is following. On toast show: toastr.options.onShown = function() { //Create an overlay on the entire page} Overlay: #overlay { background-color: rgba(0, 0, 0, 0.8); z-index: 999; position: absolute; left: 0; top: 0; width: 100%; height: 100%; display: none; } And on toast close: toastr.options.onHidden = function() { //make overlay go away } Also, I'm setting timeout of toast to 0 so it won't disappear by itself. Question: I want the toast notification to stay atop the overlay and not behind it as overlay will cover everything. How can I do it?

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• Should I design the application or model (database) first?

  - by YonahW

  I am getting ready to start building a new web project in my spare time to bring to fruition an idea that has been bouncing around my head for a while. I have never gotten down whether I am better off first building the model and then the consuming application or the other way around. What are the best practices? What would you build first and why? I imagine that in general the application should generally drive the model, however the application like many websites really doesn't do much without the model. For some reason I find it easier at times to think in terms of the model since the application is really just actions on the model. Is this a poor way of thinking about things? What advantages/disadvantages does each option have?

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• In .net, how do I choose between a Decimal and a Double

  - by Ian Ringrose

  We were discussing this the other day at work and I wish there was a Stackoverflow question I would point people at so here goes.) What is the difference between a Double and a Decimal? When (in what cases) should you always use a Double? When (in what cases) should you always use a Decimal? What’s the diver factors to consider in cases that don’t fall into one of the two camps above? (There a lot of questions that overlap this question, but they tend to be asking what someone should do in a given case, not how to decide in the general case)

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• ASP.NET 3.5 Stateless Session Managment and connection pooling?

  - by Norm

  I am designing an ASP.NET (3.5) web application that connects to a Rocket Software UniVerse database. I am in the planning stages right now and need some help in being pointed in the right direction. I am brand new to ASP and C#. I am shooting for a RESTful design and a MVC pattern. Rocket provides a .NET library called UniObjects.NET which handles everything for connecting and retrieving information from the database. What would be the best way to in general to log my users into the database, then use that session via connection pooling? I see that in 3.5 there is the ASP.NET Routing Infrastructure and that looks promising am I in the right direction on this? Also does C# support decorators like Python and Java?

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• How would you create a notification system like on SO or Facebook in RoR?

  - by Justin Meltzer

  I'm thinking that notifications would be it's own resource and have a has_many, through relationship with the user model with a join table representing the associations. A user having many notifications is obvious, and then a notification would have many users because there would be a number of standardized notifications (a commenting notification, a following notification etc.) that would be associated with many users. Beyond this setup, I'm unsure how to trigger the creation of notifications based on certain events in your application. I'm also a little unsure of how I'd need to set up routing - would it be it's own separate resource or nested in the user resource? I'd find it very helpful if someone could expand on this. Lastly, ajax polling would likely improve such a feature. There's probably some things I'm missing, so please fill this out so that it is a good general resource.

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• Best method of Zend Framework caching

  - by iamthejeff

  I have a blog built using Zend Framework, which I realize might be a bit overkill for a blog alone, but I am planning on adding other features in the future. Nevertheless, I've noticed pages could be a little speedier. I've done a basic caching method that basically captures everything in index.php (Core frontend and File backend), which works great, but unfortunately it also prevents dynamic page contents from updating (messages like "this was posted 5 minutes ago", etc) until the cache period expires. So my question is what would be the best method of caching to improve performance? I am doing fairly basic queries which are mostly simple selects, not many joins or anything fancy (using Zend_Db_Table), and even on a small database page loads are a little sluggish. Is it worth it to cache queries or should I focus my time elsewhere?

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• Rewriting .each() loop as for loop to optimize, how to replicate $(this).attr()

  - by John B

  I running into some performance issues with a jquery script i wrote when running in ie so I'm going through it trying to optimize any way possible. Apparently using for loops is way faster than using the jQuery .each method. This has led me to a question regarding the equivalent of $(this) inside a for loop. I'm simplifying what I'm doing in my loop down to just using an attr() function as it gets across my main underlying question. Im doing this with each(simplified) var existing = $('#existing'); existing.each(function(){ console.log($(this).attr('id')); }); And I've tried rewriting it as a for loop as such: var existing = $('#existing'); for(var i = 0;i < existing.length;i++) { console.log(existing[i].attr('id')); } Its throwing an error saying: Uncaught TypeError: Object #<HTMLDivElement> has no method 'attr' Thanks.

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• storing huge amount of records into classic asp cache object is SLOW

  - by aspm

  we have some nasty legacy asp that is performing like a dog and i narrowed it down to because we are trying to store 15K+ records into the application cache object. but that's not the killer. before it stores it, it converts the ADO stream to XML then stores it. this conversion of the huge record set to XML spikes the CPU and causes all kinds of havoc on users when it's happening. and unfortunately we do this XML conversion to read the cache a lot, causing site wide performance problems. i don't have the resources to convert everything to .net. so that's out. but i need to obviously use caching, but int his case the caching is hurting instead of helping. is there a more effecient way to store this data instead of doing this xml conversion to/from every time we read/update the cache?

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• How does Core Data determine if an NSObjects data can be dropped?

  - by Kevin

  In the app I am working on now I was storing about 500 images in Core Data. I have since pulled those images out and store them in the file system now, but in the process I found that the app would crash on the device if I had an array of 500 objects with image data in them. An array with 500 object ids with the image data in those objects worked fine. The 500 objects without the image data also worked fine. I found that I got the best performance with both an array of object ids and image data stored on the filesystem instead of in core data. The conclusion I came to was that if I had an object in an array that told Core Data I was "using" that object and Core Data would hold on to the data. Is this correct?

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• C++: Why don't I need to check if references are invalid/null?

  - by jbu

  Hi all, Reading http://www.cprogramming.com/tutorial/references.html, it says: In general, references should always be valid because you must always initialize a reference. This means that barring some bizarre circumstances (see below), you can be certain that using a reference is just like using a plain old non-reference variable. You don't need to check to make sure that a reference isn't pointing to NULL, and you won't get bitten by an uninitialized reference that you forgot to allocate memory for. My question is how do I know that the object's memory hasn't been freed/deleted AFTER you've initialized the reference. What it comes down to is that I can't take this advice on faith and I need a better explanation. Can anyone shed some light? Thanks, jbu

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• C++ Header Guard issues

  - by JP

  I am making a small C++ framework, which contains many .h and .cpp. I have created a general include which include all my .h file such as: framework.h #include "A.h" #include "B.h" #include "C.h" each .h header are protected with include guard such as #ifndef A_HEADER #define A_HEADER ... #endif The issues is, I would like to be able to include "framework.h" inside all the sub .h such as, but it cause lots of compiler error: #ifndef A_HEADER #define A_HEADER #include "framework.h" ... #endif If instead I use the real header file for each sub header, and the framework.h for what ever use my framework it works fine.. I would just like to include the main header inside all my sub .h so I dont need to include all the dependency everytime. Thanks :)

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• config.cache_classes = true in production mode has problems in IE

  - by techno_log

  Hi Dears, In my rails app. I am using link_to_function to bring an ajax tabs in one page.Everything works fine in Moazilla and other browsers. But in IE the tabs are not loading only when the server is started in production mode(doesn't matter whether its webrick or mongrel). In development mode everything is fine. So I figured out that the issue was with one line config.cache_classes = true in app/config/environments/production.rb when i changed the above code to config.cache_classes = false everything works fine. So I assume caching causes problem in rails. When I Googled about this I found many have the issues with caching. So my question is 1) is there any other fix for this? 2) Does this fix (config.cache_classes = false) causes any performance issues. If then how to overcome that? Any comments and suggestions are welcome. Techno_log

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• IOS SDK : first advices for beginners

  - by VdesmedT

  I too often answer the same kind of questions regarding basic topics like memory management, UITableView, Interface Orientation, MVC, etc... I understand very well that everyone starting with that SDK is too exited about getting its hand on it but a few reading would save them hours of debugging and the frustration that come along with the feeling that "We miss something here". I'd like experience users to share the few small articles, white papers, docs, book chapters that helps other save their time and avoid frustration. My first vote would be for : IOS Memory Management Guide View Controller Programming Guide Table View Guide And as a General recommendation, read the Overview section that come along with every class documention in the reference library, they contains most of what you need to know to avoid big traps !

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• Is there a good collection library for C-language?

  - by matti

  We have to maintain and even develop C-code of our legacy system. Is there good collection library that would support Java/C# (new versions) style collections. Hashtable, HashSet, etc. Of course without objects, but with structs. The HashTable key limitations to "strings" and ints is not a problem. It wouldn't be bad if it's free even for commercial use. I'm back to C from C# and I must say i'm depressed using our own libraries and the language in general. We're using VS2005 and MS C-compiler if that has nothing to do with anything. Thanks & BR -Matti

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• How easy would it be to refactor a small JSP/Servlet/JDBC project to SpringMVC/Hibernate

  - by John

  With reference to this post, I am considering starting a new web-based Java project. Since I don't know Spring/Hibernate I was concerned if it's a bad plan to start learning them while creating a new project, especially since it will slow down the early development. One idea I had was to write a prototype using tech I do know, namely JSP/Servlets/JDBC, since I can get this running much quicker with my current knowledge. I could then throw the whole thing away and start over with Spring, etc, but I'd like to consider how easy it would be to refactor a smallish project from JSP/Servlets/JDB to SpringMVC/Hibernate? My DB could of course be re-used but what about other code... would I expect to save most of it plugged into an MVC framework, or is the paradigm shift big enough this would cause more trouble than it avoids? Please use the other question for more general advice on choosing technologies

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• Secure password transmission over unencrypted tcp/ip

  - by academicRobot

  I'm in the designing stages of a custom tcp/ip protocol for mobile client-server communication. When not required (data is not sensitive), I'd like to avoid using SSL for overhead reasons (both in handshake latency and conserving cycles). My question is, what is the best practices way of transmitting authentication information over an unencrypted connection? Currently, I'm liking SRP or J-PAKE (they generate secure session tokens, are hash/salt friendly, and allow kicking into TLS when necessary), which I believe are both implemented in OpenSSL. However, I am a bit wary since I don't see many people using these algorithms for this purpose. Would also appreciate pointers to any materials discussing this topic in general, since I had trouble finding any.

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• Can functions like sin() be redefined, in Fortran, C or Java?

  - by EOL

  Can a mathematical function like sin() be redefined, in Fortran, C or Java code, while preserving the default behavior of other mathematical functions like cos()? Or can another function named sin() but that accepts different argument types be defined in addition to the built-in sin()? I am interested in general features of these languages (I am thinking of applications like the implementation of non-usual number algebras). I tried to define a sin() function in a Fortran 95 program, but the intrinsic sin() function was called instead… Is there a way around this? what about C and Java?

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