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• Why is thread local storage so slow?

  - by dsimcha

  I'm working on a custom mark-release style memory allocator for the D programming language that works by allocating from thread-local regions. It seems that the thread local storage bottleneck is causing a huge (~50%) slowdown in allocating memory from these regions compared to an otherwise identical single threaded version of the code, even after designing my code to have only one TLS lookup per allocation/deallocation. This is based on allocating/freeing memory a large number of times in a loop, and I'm trying to figure out if it's an artifact of my benchmarking method. My understanding is that thread local storage should basically just involve accessing something through an extra layer of indirection, similar to accessing a variable via a pointer. Is this incorrect? How much overhead does thread-local storage typically have? Note: Although I mention D, I'm also interested in general answers that aren't specific to D, since D's implementation of thread-local storage will likely improve if it is slower than the best implementations.

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• sqlce in Xenocode

  - by user184204

  Please direct answers to : http://stackoverflow.com/questions/1518867/sqlce-in-xenocode This question is an accidental duplicate I'm using Xenocode in my application so that it works without a .NET framework. I'm using Xenocode Virtual Application Studio(version 6.1). Everything works fine except the .sdf file which I have embedded inside the application directory. actually in the application the instead of SQL server i have used SQL Compact edition(3.5) and i have included the reqired dll . All the files are working except the ".sdf" file. Any idea y is that so? Is it because the ".sdf" file is being used when the xenocode after snapshot was taken? if so what is the solution for that? i cannot avoid using it because Xenocode's after snapshot will not recognise the application if it's not running and if I run the application ".sdf" file will be used. Anyway to solve this?

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• MVC - Calling Controller Methods

  - by JT703

  Hello, My application is following the MVC design pattern. The problem I keep running into is needing to call methods inside a Controller class from outside that Controller class (ex. A View class wants to call a Controller method, or a Manager class wants to call a Controller method). Is calling Controller methods in this way allowed in MVC? If it's allowed, what's the proper way to do it? According to the version of MVC that I am following (there seems to be so many different versions out there), the View knows of the Model, and the Controller knows of the View. Doing it this way, I can't access the controller. Here's the best site I've found and the one describing the version of MVC I'm following: http://leepoint.net/notes-java/GUI/structure/40mvc.html. The Main Program code block really shows how this works. Thanks for any answers.

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• R heatmaps - non-text labels?

  - by Carl

  I am making a heatmap plot; currently the axes are labeled by index number. However, the index number corresponds to a series of 1/0s, which my group typically represents with a row of filled(1) or unfilled(0) boxes (think chessboard, though not strictly alternating colors). I'd like to use that representation instead of the index numbers. Any suggestions? I've considered simply making the labels as a plot, and positioning that adjacent to the heatmap, but I'm not finding a convenient way to do that either. I will also appreciate answers that are more generically applicable. edit - current code: map <- data.matrix(read.csv("./heatmap.out", header=F, sep=" ")) # ...some clean-up p<-heatmap(map, Rowv=NA, Colv=NA, col=grey(10:0 / 10)) this simply labels the heatmap rows/cols by index number. heatmap.out is raw numeric data.

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• Comparison of Code Review Tools/Systems

  - by SytS

  There are a number of tools/systems available aimed at streamlining and enhancing the code review process, including: CodeStriker Review Board, code review system in use at VMWare Code Collaborator, commercial product by SmartBear Rietveld, based on Modrian, the code review system in use at Google Crucible, commercial product by Atlassian These systems all have varying feature sets, and differ in degrees of maturity and polish; the selection is a little bewildering for someone who is evaluating code review systems for the frist time. Some of these tools have already been mentioned in other questions/answers on StackOverflow, but I would like to see a more comprehensive comparison of the more popular systems, especially with respect to: integration with source control systems integration with bug tracking systems supported workflow (reviews pre/post commit, review or contiguous/non-contigous revision ranges, etc) deployment/maintenance requirements

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• how to automate upsizing from Access to SQL Server?

  - by Arne

  Hi, I need to automate the migration from an Access (2003) to an SQL Server DB (2005 or 2008). The upsizing should be done automatically as part of a build process. I need that because there are 2 versions of the software, a single user rich client and a web version. Access DB is used for single user to minimize setup effort, SQL Server to improve performance and scaling with many simultanious users. Access should be the "leading" DB, meaning devs do changes in Access DB and those are propagated to the SQL server within the build process. Many changes will occur, so doing it manually is not an option. I am new to the Microsoft world, so I dont know appropriate tools for that. What tools can I use and how? I know how to do it (by clicking) with the upsizing assistant. Perhaps I can automate that somehow? Thanks in advance for your answers. Cheers, Arne

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• .NET WF4: Should it be in the middle of everything?

  - by stimpy77

  I am aware that WF4 (Windows Workflow 4.0, part of .NET 4.0) is a significant rework and redesign of WF3, where much of what made WF3 a poor technology choice has been cleaned up in WF4. For example, as far as I can tell, WF4 (Windows Workflow 4.0) activities are more or less testable with [TestMethod] and mocking. This among other things, like improved performance, has grabbed my attention about the technology again, whereas I had previously pooh-poohed WF3. I'm working on a new architecture for essentially an n-tier collaborative application (not enterprise-class, just a smallish project with potential to grow significantly) where I'm already trying to discipline myself to use IoC and, to some extent, TDD, and I'm wondering, in general terms, whether it is wiser to just hand-code workflow logic or if I should delve into learning and integrating WF4 so that WF becomes literally the controller of the entire application, i.e. the practical C in "MVC" (not ASP.NET MVC but rather the pattern). So should workflow activities in WF4 be the primary controller for a highly expandable/growable web-based collaborative application? Or am I asking entirely the wrong question? This is a vague question, I'm sure, so abstract answers are as welcome as specific ones.

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• Array Vs. Linked List

  - by Onorio Catenacci

  I apologize--this question may be a bit open-ended but I think there are probably definite, quantifiable answers to it so I'll post it anyway. A person I know is trying to learn C++ and software development (+1 to him) and he asked me why someone would want to use a linked list in preference to an array. Coding a linked list is, no doubt, a bit more work than using an array and he wondered what would justify the additional effort. I gave him the answer I know: insertion of new elements is trivial in linked list but it's a major chore in an array. But then I got to thinking about it a bit more. Besides the ease of insertion of a new element into a linked list are there other advantages to using a linked list to store a set of data vs. storing it in an array? As I said, I'm not meaning to start a long and drawn-out discussion. I'm just looking for other reasons that a developer might prefer a linked list to an array.

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• How do you mock a Sealed class?

  - by Brett Veenstra

  Mocking sealed classes can be quite a pain. I currently favor an Adapter pattern to handle this, but something about just keeps feels weird. So, What is the best way you mock sealed classes? Java answers are more than welcome. In fact, I would anticipate that the Java community has been dealing with this longer and has a great deal to offer. But here are some of the .NET opinions: Why Duck Typing Matters for C# Develoepers Creating wrappers for sealed and other types for mocking Unit tests for WCF (and Moq)

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• Is there any good programming books forum out there?

  - by prosseek

  I always feel the internet forums are a good way to gain knowledge - asking questions and get some answers from everybody, and SO is a great example. But when I get questions reading some programming books, I wonder to whom can I ask the questions. O'Reilly and PragProg have their own book forums, and some authors open their own forums. Or, we might be able to send an email to the author if that is absolutely necessary. Is there any good forum on programming books? Can you share any good programming book forums on the web? Or, is SO the best place to ask some questions in programming books? I found some book reading forums, but not programming books.

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• Sanitizing incoming XML via WCF

  - by Clark

  I am consuming a Java webservice from .net using WCF. I am getting an error on deserialization of a response from the Java service The byte 0x00 is not valid at this location. Line 1, position 725. I know from some research that this is an incorrectly encoded null, but I am unlikely to get the provider to change it, so I would like to sanitize the null out before WCF deserializes the return message. Any Ideas? I am using c#, but answers in any CLR language will do.

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• Is it possible to implement an infinite IEnumerable without using yield with only C# code?

  - by sinelaw

  Edit: Apparently off topic...moving to Programmers.StackExchange.com. This isn't a practical problem, it's more of a riddle. Problem I'm curious to know if there's a way to implement something equivalent to the following, but without using yield: IEnumerable<T> Infinite<T>() { while (true) { yield return default(T); } } Rules You can't use the yield keyword Use only C# itself directly - no IL code, no constructing dynamic assemblies etc. You can only use the basic .NET lib (only mscorlib.dll, System.Core.dll? not sure what else to include). However if you find a solution with some of the other .NET assemblies (WPF?!), I'm also interested. Don't implement IEnumerable or IEnumerator. Notes The closest I've come yet: IEnumerable<int> infinite = null; infinite = new int[1].SelectMany(x => new int[1].Concat(infinite)); This is "correct" but hits a StackOverflowException after 14399 iterations through the enumerable (not quite infinite). I'm thinking there might be no way to do this due to the CLR's lack of tail recursion optimization. A proof would be nice :)

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• White (Light) vs. Black (Dark) Backgrounds: Health Effects

  - by Hosam Aly

  I am adding a bounty to this question, hoping for some scientific research results. Thank you everybody! I have recently tried working on dark backgrounds, and it seemed (to me) to be easier on the eye. However, today I read Gerrie Schenck's comment on this answer, in which he said that mainframe developers were advised to use white backgrounds instead of black, as it is said that white is easier on the eye. So which one is actually better for the eyes in the long run? I would be thankful for any (scientific) references about the subject, as my eyes really need some relaxation. I wanted to make this question a community wiki, but I think that the least I can do to thank people is to reward their answers, so I'm leaving it as a normal question. Many, many thanks for your help. P.S. I don't know which tags would be appropriate for this question, so I'd be grateful if you could tag it in a better way than I did.

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• Big-O of PHP functions?

  - by Kendall Hopkins

  After using PHP for a while now, I've noticed that not all PHP built in functions as fast as expected. Consider the below two possible implementations of a function that finds if a number is prime using a cached array of primes. //very slow for large $prime_array $prime_array = array( 2, 3, 5, 7, 11, 13, .... 104729, ... ); $result_array = array(); foreach( $array_of_number => $number ) { $result_array[$number] = in_array( $number, $large_prime_array ); } //still decent performance for large $prime_array $prime_array => array( 2 => NULL, 3 => NULL, 5 => NULL, 7 => NULL, 11 => NULL, 13 => NULL, .... 104729 => NULL, ... ); foreach( $array_of_number => $number ) { $result_array[$number] = array_key_exists( $number, $large_prime_array ); } This is because in_array is implemented with a linear search O(n) which will linearly slow down as $prime_array grows. Where the array_key_exists function is implemented with a hash lookup O(1) which will not slow down unless the hash table gets extremely populated (in which case it's only O(logn)). So far I've had to discover the big-O's via trial and error, and occasionally looking at the source code. Now for the question... I was wondering if there was a list of the theoretical (or practical) big O times for all* the PHP built in functions. *or at least the interesting ones For example find it very hard to predict what the big O of functions listed because the possible implementation depends on unknown core data structures of PHP: array_merge, array_merge_recursive, array_reverse, array_intersect, array_combine, str_replace (with array inputs), etc.

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• Git - tidying up a repo

  - by Simon Woods

  Hi I have got my repo into a bit of a state and want to be able to work my way out of it The repo looks a bit like this (A1, B1, C1 etc are obviously commits) A1 ---- A2 ---- A3 ---- A4 ---- A5 ---- A6 ---- A7 ---- A8 / (from a remote repo) B1 ---- B2 --------------------------------- | \ \ C1 ---------------------------------C2 \ / D1 --- D2 --- D3 --- D4 --- D5 --- D6 Ideally I'd like to be able to remove all the revisions (with rebase?) on the B, C and D lines (I'm loathed to say branches simply because there are now no local branches on these lines except ref branches to the remote repo) and try to merge in the remote repo again, perhaps in a better way. I'd be grateful of any suggestions as to how to get rid of all these commits. Could I ask that any answers use revision SHA1s rather than branch names. I thought that somehow I'd be able to revert the merge into A7 but can't quite work out how to do it I hope that is sufficient information. Many thx Simon

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• How Gridview co-operates with ObjectDataSource?

  - by sanjuro

  Hi, how Gridview co-operates with ObjectDataSource internally? When you set DataSourceID of GridView, assigned ObjectDataSource take care of such things as paging and sorting, but i don't have full control above databinding itself, on the other side when i set datasource of gridview in code-behind: protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { testGridView.DataSource = testObjectDataSource.Select(); testGridView.DataBind(); } } Now i have full control, but i have lost the advantage of comfort sorting and paging. And that co-operation between ObjectDataSource and Gridview became mystery for me. So can anybody explain me in details how ObjectDataSource and Gridview co-operates under the hood? I want to understand it in order to write my own smart code or own gridview that will mimic this co-operation. Many thanks for answers.

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• Why did the aspnet_client folder come back in ASP.NET 4?

  - by rbeier

  I recently upgraded my MVC 1 project (ASP.NET 3.5) to MVC 2 (ASP.NET 4). I noticed there is now a folder "aspnet_client\system_web\4_0_30319" under the site root. This folder is empty... I'm just wondering if anyone knows why it was created. I remember the aspnet_client folder from the days of .NET 1.1, but I thought it was obsoleted when .NET 2.0 came out. For example, see the answers in these two stackoverflow posts: What is the aspnet_client folder in my ASP.NET website? What is the aspnet_client folder for under the IIS structure? So I'm just curious why it's back. Thanks, Richard

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• learning the Lower levels of computing

  - by Ben

  I am a software developer with four years experience in .Net development, I always like to keep up to date with the latest technologies (.net related normally) being released and love learning them. I didn't however go to university and learnt all I know through helpful colleagues, .Net courses, the internet and good old books. I feel that I am a good developer, but without learning the lower levels of a computer as you would in the first year of a computer related Uni course, I get lost when talking to people about a lot of more technical lower level computing. Is there a book(s) that anyone could recommend, that would cover the lower levels of what is going on when I click "Run" in Visual Studio? I feel out of my depth when my boss says to me "Thats running in the CPU cache" or "you're limited by disk reads there", and would like to feel more confident when talking about how the hardware talks to each other (CPU to RAM etc). Apologise if thats a vague question, or has been asked before (i did check and couldn't find anything on here that answers my question).

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• Efficiently Determine if EF 4 POCO Already in ObjectSet

  - by Eric J.

  I'm trying EF 4 with POCO's on a small project for the first time. In my Repository implementation, I want to provide a method AddOrUpdate that will add a passed-in POCO to the repository if it's new, else do nothing (as the updated POCO will be saved when SaveChanges is called). My first thought was to do this: public void AddOrUpdate(Poco p) { if (!Ctx.Pocos.Contains<Poco>(p)) { Ctx.Pocos.AddObject(p); } } However that results in a NotSupportedException as documented under Referencing Non-Scalar Variables Not Supported (bonus question: why would that not be supported?) Just removing the Contains part and always calling AddObject results in an InvalidStateException: An object with the same key already exists in the ObjectStateManager. The existing object is in the Unchanged state. An object can only be added to the ObjectStateManager again if it is in the added state. So clearly EF 4 knows somewhere that this is a duplicate based on the key. What's a clean, efficient way for the Repository to update Pocos for either a new or pre-existing object when AddOrUpdate is called so that the subsequent call to SaveChanges() will do the right thing? I did consider carrying an isNew flag on the object itself, but I'm trying to take persistence ignorance as far as practical.

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• Pagination For SMS in Android specifically

  - by Priyank

  Hi. I had a pagination related question posted earlier. Here I went through the posted answers and suggested choices and I realized that to implement pagination in an application I could still write db level queries and ensure that I could implement pagination, even if in a crude form. However I have few follow up questions now: I am trying to show SMS from a content provider. Suppose I don't want to use content provider; can I access SMS table in database through my application. Aoes android's security framework allow that? How do people generally handle pagination problems in android, related to content that they are not storing but instead are fetching through content providers. (Android's own or custom) Isn't this a bigger problem. I am surprised to find so little text online about it.

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• What non-programming books should programmers read?

  - by Charles Roper

  This is a poll asking the Stackoverflow community what non-programming books they would recommend to fellow programmers. Please read the following before posting: Please post only ONE BOOK PER ANSWER. Please search for your recommendation on this page before posting (there are over NINE PAGES so it is advisable to check them all). Many books have already been suggested and we want to avoid duplicates. If you find your recommendation is already present, vote it up or add some commentary. Please elaborate on why you think a given book is worth reading from a programmer's perspective. This poll is now community editable, so you can edit this question or any of the answers. Note: this article is similar and contains other useful suggestions.

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• How to draw a smooth/dithered gradient on a canvas in Android

  - by André

  Several answers mention to use GradientDrawable.setDither(true) to draw smooth gradients in Android. That has no effect in my code. Any idea what I have to change to get a well looking gradient in my live wallpaper? GradientDrawable gradient = new GradientDrawable(Orientation.TL_BR, colors); gradient.setGradientType(GradientDrawable.RADIAL_GRADIENT); gradient.setGradientRadius(canvas.getWidth() * 2); gradient.setDither(true);g gradient.setGradientCenter(-0.1f, -0.1f); gradient.setBounds(cb); gradient.draw(canvas);

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• How to create SSIS package to update from one database to another database within same server

  - by Pavan Kumar

  My query is related to the answers i got for questions i had posted earlier in the same forum. I have a copy of a client database which is attached to SQL Server where the Central Database exists. The copy already contains the updated data. I just want to update from that copy to Central Database both holding same schema and are present in the same server using C# .NET. One of the solution i got was to create SSIS package and run it from the UI. I want to know as how i can create SSIS Package to achieve this. I am new to SSIS. I am using SQL Server 2005 Standard Edition and Visual Studio 2008 SP1 installed. I learnt that BIDS 2005 is used to create packages which comes by default with SQL Server 2005. Can someone please give me a example as i am new to this.

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• What are some interesting fringe programming topics that might have hands-on training?

  - by hal10001

  Whenever training topic questions are asked, the answers are fairly typical, and involve a pretty limited subset of topics like OO, design patterns, algorithms, web services, SQL, etc., but I wonder if there are some fringe topics that are still applicable to the programming field and would give me a more rounded approach to development. When I think of "fringe", I think of 2600: The Hacker Quarterly articles that discuss how to use real world (sometimes obscure) exploits, or something like Maker Faire that demonstrates embedded systems programming using Arduino. I have around $1500-2000 to spend, and my job entails Java technologies, but that does not limit my options.

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• Return a pointer to a char array in C

  - by snitko

  I've seen a lot of questions on that on StackOverflow, but reading the answers did not clear that up for me, probably because I'm a total newbie in C programming. Here's the code: #include <stdio.h> char* squeeze(char s[], char c); main() { printf("%s", squeeze("hello", 'o')); } char* squeeze(char s[], char c) { int i, j; for(i = j = 0; s[i] != '\0'; i++) if(s[i] != c) s[j++] = s[i]; s[j] = '\0'; return s; } It compiles and I get segmentation fault when I run it. I've read this faq about about returning arrays and tried the 'static' technique that is suggested there, but still could not get the program working. Could anyone point out exactly what's wrong with it and what should I be paying attention in the future?

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