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• Must .aspx files have a page directive?

  - by Keith Bloom

  Around 90% of the pages for our websites have no .Net code embedded in them yet are published as .aspx files. I want these to render as fast as possible so I'm removing as much as I can. Does the .Net page directive have an impact on performance? I am thinking about two factors; the page speed for each GET and what happens when the file changes. The CMS system re-creates each page daily and I'm wondering if this triggers the ASP.Net compilation process.

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• Best way to provide software settings?

  - by claws

  I'm using C# .NET. In my software I'm providing settings dialog through which user can set the application settings which I want to save to a file. Requirements (typical): Every class I defined uses some part of these settings. So, these should be global to all classes. These should be loaded while software is started. When ever user changes settings and clicks 'save'/'apply'. Current settings should change. I am wondering what is the best way to do this? Also, what is the best way to save these settings to disk? I mean should I create a Settings class object and serializing it to 'settings.dat' or provide an structured file like XML/JSON

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• Having encoding problems in Aptana Studio

  - by keune

  A few months ago, I was working on a PHP project in Aptana Studio. It was version 1.5 or something. Later I installed Aptana 2.0 and created a new project with the same files. Back then it was UTF-8 so I chose UTF-8 for the project's text file encoding. When I make changes in any PHP file using Aptana, it gives the error: Warning: Cannot modify header information - headers already sent... I know it's a problem related to encoding. What can I do?

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• What signing method to use for public open-source projects?

  - by Irchi

  I'm publishing an open-source library on CodePlex, and want the dll files to have strong names so that they can be added to GAC. What's the best option for signing? Should I use SNK? If so, everyone have access to the key. I don't have a problem with everyone having access, but is it a good approach? Should I use PFX? If so, does it mean that other people downloading the source code are not able to build the solution? What I like to do is that I am the only one person to have access to the key, so that the signed assemblies also have a level of authenticity, but meanwhile don't prevent other developers to download, build, or change the source code for themselves, and be able to post changes for the main project.

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• flex List Size not updating when itemRenderer resizes itself

  - by duder

  I've got a list with a custom itemRenderer that's just a rectangle of specific size. The list <s:List id="thelist" width="100%" dataProvider="{thelistdata}" itemRenderer="ListItem" borderVisible="true" /> Note the list's border is visible to help with debugging The itemRenderer <s:Rect id="box" width="50" height="50"> <s:fill> <s:SolidColor color="blue"/> </s:fill> </s:Rect> When the itemRenderer receives an event, it changes its size to half box.width = 25; box.height = 25; I see the itemRenderers are resizing themselves correctly, but the list itself stays the same size and the border stays where it is. Anyone knows how to fix this bug. Basically the list should refresh its size too to fit the smaller boxes.

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• Change DIV background color for all inputs in form

  - by Erik

  I have a form with 20 input fields. Each input field is inside a DIV I have a script that changes the background color of the DIV via keyup function along with two other DIV tags. Rather than duplicating the script 20 times for each DIV and Input, is it possible to re-write the script to do all DIV's and their Inputs? <script> $(document).ready(function(){ $("#id").keyup(function() { if($("#id").val().length > 0) $("#in1, #nu1, #lw1, #id").css("background-color", "#2F2F2F").css("color", "#FFF"); else { if($("#id").val().length == 0) $("#in1, #nu1, #lw1, #id").css("background-color", "#E8E8E8").css("color", "#000"); } }); }); </script>

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• Difference between Popup's IsOpen and Visibility properties?

  - by cfouche

  I've played around with the WPF Popup Control and as far as I can see, the Visibility property is superfluous. If you have a Popup with IsOpen = True, it will be visible even if its Visibility = Collapsed. If you have a Popup with IsOpen = False, then its Visibility will be Collapsed, and will remain "Collapsed" when IsOpen changes to true, and it will appear. (i.e. you'll have something that appears on your screen, even though Snoop says it is Collapsed.) Why does the Popup control have both these properties? Am I missing something here?

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• Linux periodically "losing" ability to connect to server via SSH?

  - by gct

  I know this isn't exactly a programming question, but it popped up in my use of git for programming projects at least. I've got a web server that I use to host my git repos on, but my ubuntu box seems to "lose" the ability to connect to it via SSH. I'll get a "connection refused" error when I try to ssh or use git. Rebooting my local machine will fix the problem, but only temporarily. I can still connect to the web interface just fine, and the problem manifests with other servers as well. I've been working around it by pulling my changes over to my laptop and pushing from there, but that's sub-optimal as you can imagine. Has anyone seen something like this? I'd be tempted to say it's some kind of IP caching problem, but I can't connect even using the IP address of the server directly... Running Ubuntu 9.04

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• How to Change the url of the page when jquery ui tabs is clicked

  - by Aakash Chakravarthy

  Hello, I have jquery tabs list like <ul id="tabsList"> <li><a href="#tab-1">TAB 1</a></li> <li><a href="#tab-2">TAB 2</a></li> <li><a href="#tab-3">TAB 3</a></li> </ul> and contents for it like <div id="tab-1">...</div>, <div id="tab-2">...</div>, <div id="tab-3">...</div> When the tab is clicked, the tab changes correctly. But i want the id of the tabs be in the url. i.e when tab 2 is clicked, the URL should change to http://example.com/index.htm#tab-2 when tab 1 is clicked, the URL should change to http://example.com/index.htm#tab-1 How to do this ?

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• "No architectures" error when compiling objective flickr for iphone device

  - by user176723

  I'm getting the following error when I attempt to compile my XCode project to debug on my device. No architectures to compile for (ARCHS=x86_64, VALID_ARCHS=armv6 armv7). I've included ObjectiveFlickr in my project just as the readme describes. I've gone through the process several times and redownloaded objectiveFlickr a few times to start over. I've gotten objectiveFlickr to work on devices in the past. I don't know why I am suddenly having trouble. Can anybody point me to something that might hold the clue I need? Any other info I need to provide? I made only changes to my project that are specified by the OF documentation. I also get this error when compiling the included snap-n-run example project provided with OF. So I must be missing something beneath my project. Thanks, Charlie

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• Change element class without using css animation

  - by Akshat

  I have a class with the following type of css animaton .cssanimation { -webkit-transition: 0.2s all ease-in-out -o-transition: 0.2s all ease-in-out -moz-transition: 0.2s all ease-in-out transition: 0.2s all ease-in-out .. some other changes in position } I have the div <div id="thediv"> ... </div> $('#thediv').addClass('cssanimation') //animates the object I do use this animation at some point but sometimes I'd like to add it without invoking the animation Does Jquery have a way in which I can add classes without invoking their css animations?

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• how to get the camera data

  - by beof

  Hello ,guys, My app needs to get the camera data from Iphone. In my ImagePickerController, there is overlayView drawing realtime indications. I use UIGetScreenImage() to get the screenshot, and I also dump overlayview to image, then I can restore the original Image based on these two images. if the overlayView is still, it works quite well, but if the overlayView keeps changing, UIGetScreenImage() can not keep up with it. For example,if the overlayView changes from a rectangle to a circle, then calling UIGetScreenImage() returns with a rectangle on top of it. Is there a way to get the realtime camera data? I really appreciate if someone could help.

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• Embedding mercurial revision information in Visual Studio c# projects automatically

  - by Mark Booth

  Original Problem In building our projects, I want the mercurial id of each repository to be embedded within the product(s) of that repository (the library, application or test application). I find it makes it so much easier to debug an application ebing run by custiomers 8 timezones away if you know precisely what went into building the particular version of the application they are using. As such, every project (application or library) in our systems implement a way of getting at the associated revision information. I also find it very useful to be able to see if an application has been compiled with clean (un-modified) changesets from the repository. 'Hg id' usefully appends a + to the changeset id when there are uncommitted changes in a repository, so this allows is to easily see if people are running a clean or a modified version of the code. My current solution is detailed below, and fulfills the basic requirements, but there are a number of problems with it. Current Solution At the moment, to each and every Visual Studio solution, I add the following "Pre-build event command line" commands: cd $(ProjectDir) HgID I also add an HgID.bat file to the Project directory: @echo off type HgId.pre > HgId.cs For /F "delims=" %%a in ('hg id') Do <nul >>HgID.cs set /p = @"%%a" echo ; >> HgId.cs echo } >> HgId.cs echo } >> HgId.cs along with an HgId.pre file, which is defined as: namespace My.Namespace { /// <summary> Auto generated Mercurial ID class. </summary> internal class HgID { /// <summary> Mercurial version ID [+ is modified] [Named branch]</summary> public const string Version = When I build my application, the pre-build event is triggered on all libraries, creating a new HgId.cs file (which is not kept under revision control) and causing the library to be re-compiled with with the new 'hg id' string in 'Version'. Problems with the current solution The main problem is that since the HgId.cs is re-created at each pre-build, every time we need to compile anything, all projects in the current solution are re-compiled. Since we want to be able to easily debug into our libraries, we usually keep many libraries referenced in our main application solution. This can result in build times which are significantly longer than I would like. Ideally I would like the libraries to compile only if the contents of the HgId.cs file has actually changed, as opposed to having been re-created with exactly the same contents. The second problem with this method is it's dependence on specific behaviour of the windows shell. I've already had to modify the batch file several times, since the original worked under XP but not Vista, the next version worked under Vista but not XP and finally I managed to make it work with both. Whether it will work with Windows 7 however is anyones guess and as time goes on, I see it more likely that contractors will expect to be able to build our apps on their Windows 7 boxen. Finally, I have an aesthetic problem with this solution, batch files and bodged together template files feel like the wrong way to do this. My actual questions How would you solve/how are you solving the problem I'm trying to solve? What better options are out there than what I'm currently doing? Rejected Solutions to these problems Before I implemented the current solution, I looked at Mercurials Keyword extension, since it seemed like the obvious solution. However the more I looked at it and read peoples opinions, the more that I came to the conclusion that it wasn't the right thing to do. I also remember the problems that keyword substitution has caused me in projects at previous companies (just the thought of ever having to use Source Safe again fills me with a feeling of dread *8'). Also, I don't particularly want to have to enable Mercurial extensions to get the build to complete. I want the solution to be self contained, so that it isn't easy for the application to be accidentally compiled without the embedded version information just because an extension isn't enabled or the right helper software hasn't been installed. I also thought of writing this in a better scripting language, one where I would only write HgId.cs file if the content had actually changed, but all of the options I could think of would require my co-workers, contractors and possibly customers to have to install software they might not otherwise want (for example cygwin). Any other options people can think of would be appreciated. Update Partial solution Having played around with it for a while, I've managed to get the HgId.bat file to only overwrite the HgId.cs file if it changes: @echo off type HgId.pre > HgId.cst For /F "delims=" %%a in ('hg id') Do <nul >>HgId.cst set /p = @"%%a" echo ; >> HgId.cst echo } >> HgId.cst echo } >> HgId.cst fc HgId.cs HgId.cst >NUL if %errorlevel%==0 goto :ok copy HgId.cst HgId.cs :ok del HgId.cst Problems with this solution Even though HgId.cs is no longer being re-created every time, Visual Studio still insists on compiling everything every time. I've tried looking for solutions and tried checking "Only build startup projects and dependencies on Run" in Tools|Options|Projects and Solutions|Build and Run but it makes no difference. The second problem also remains, and now I have no way to test if it will work with Vista, since that contractor is no longer with us. If anyone can test this batch file on a Windows 7 and/or Vista box, I would appreciate hearing how it went. Finally, my aesthetic problem with this solution, is even strnger than it was before, since the batch file is more complex and this there is now more to go wrong. If you can think of any better solution, I would love to hear about them.

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• How do I best run a search on Date when it is not a :has_many association?

  - by Angela

  I have a number of activities that have a calculated scheduled date. The activities, for example, Email, have a email.days method which is the days from a Contact.start_date on which it should be sent. This means contact.start_date + email.days yields a date on which email is sent to contact. I would like to use link_to around the date, so I can see all the emails and associated contacts that are to be scheduled on that date. However, this "date" is not an attribute or an associate, so I'm not linking to a model's view. It's calculated. So: 1) What should the actual "format" of the date that gets passed in the URl be? What is the method to do the consistent conversion? 2) How do I (find) all instances, because this "date" is not an actual attribute, is it a calculated value which changes depending on the two associated models of Contact and Email. Thanks.

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• Can I programatically determine if a PNG is animated?

  - by alex

  I have PNG (as well as JPEG) images uploaded to my site. They should be static (i.e. one frame). There is such thing as APNG. (it will be animated in Firefox). According to the Wikipedia article... APNG hides the subsequent frames in PNG ancillary chunks in such a way that APNG-unaware applications would ignore them, but there are otherwise no changes to the format to allow software to distinguish between animated and non-animated images. Does this mean it is impossible to determine if a PNG is animated with code? If it is possible, can you please point me in the right direction PHP wise (GD, ImageMagick)?

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• Hitting a memory limit slows down the .Net application

  - by derdo

  We have a 64bit C#/.Net3.0 application that runs on a 64bit Windows server. From time to time the app can use large amount of memory which is available. In some instances the application stops allocating additional memory and slows down significantly (500+ times slower).When I check the memory from the task manager the amount of the memory used barely changes. The application keeps on running very slowly and never gives an out of memory exception. Any ideas? Let me know if more data is needed.

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• MS Access (2010) Enable Design View

  - by Tim GONELLA

  I downloaded the Access template below for doing a home inventory: http://office.microsoft.com/en-us/templates/results.aspx?qu=home%20inventory&ex=1&queryid=0d245f2a%2Dacdc%2D4161%2D92c8%2D8ba16a52ab32&AxInstalled=1&c=0#ai:TC101918100| The design view is not visible, which is a bit of a nuisance. Things I've tried: 1) In options/options/current database/ the check boxes (enable layout view & enable design changes for tables in Datasheet view) are both greyed out. 2) I've unblocked the file using Right-Click-Properties. 3) I've tried copying/exporting the objects to another database. But can only copy/export the tables. 4) I've tried holding shift when opening the DB. 5) Enabling all trust permissions etc. None of these work Does anybody have any suggestions. (I'm using Office 2010) Thanks

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• umbraco front end site stopped working suddenly

  - by Srilakshmi

  Hi All, I created one webapplication and placed the default.aspx page in the root folder of the umbraco (i.e., httpdocs folder) and the application dll into the bin folder. I used the name “Default.aspx” as the other names are not working. Now the issue is all the pages are redirecting to the default.aspx page (I haven’t made any config changes anywhere in the umbraco setup) I found this root cause and removed the default.aspx page and its respective dll from the bin folder. The resource cannot be found. Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable. Please review the following URL and make sure that it is spelled correctly. Requested URL: /default.aspx I stuck up here and struggling to resolve it.Please help me out on this THanks, Srilakshmi

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• Subclipse CollabNet Myster Icon

  - by Rares Saftoiu

  The scenario is that I'm merging a series of cherry picked revisions from on SVN branch into trunk. I'm using the subclipse CollabNet client to do the merge. Everything works great, except for in addition to the files I picked to merge, my working directory shows a series of changes that svn thinks have changed but that I haven't chosen to merge. If I do a diff on the files in question it tells me there's no differences. If I do a commit, I get the screenshot below, with the mystery icon I haven't been able to find document anywhere. Here's a link to the screenshot: http://i.imgur.com/1a92j.png

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• Password reset by email without a database table

  - by jpatokal

  The normal flow for resetting a user's password by mail is this: Generate a random string and store it in a database table Email string to user User clicks on link containing string String is validated against database; if it matches, user's pw is reset However, maintaining a table and expiring old strings etc seems like a bit of an unnecessary hassle. Are there any obvious flaws in this alternative approach? Generate a MD5 hash of the user's existing password Email hash string to user User clicks on link containing string String is validated by hashing existing pw again; if it matches, user's pw is reset Note that the user's password is already stored in a hashed and salted form, and I'm just hashing it once more to get a unique but repeatable string. And yes, there is one obvious "flaw": the reset link thus generated will not expire until the user changes their password (clicks the link). I don't really see why this would be a problem though -- if the mailbox is compromised, the user is screwed anyway.

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• Format number as I type Expand this post

  - by conorhiggins

  Hi I am working on an app at the moment that requires number input to be formatted as the textfield changes as well as perform a calculation. I have the text fields set up so that as the user types notifications are passed out and a calculation is performed. However what I need to do now is format the text to be in this style: €1,000,000 rather than 1000000. I have this working for the output of the calculation already but everytime I try to apply it to the input text the simulator seems to crash or at least freezes for a while. I'd imagine its a simple enough fix.

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• .NET Code Evolution

  - by Alois Kraus

  Originally posted on: http://geekswithblogs.net/akraus1/archive/2013/07/24/153504.aspxAt my day job I do look at a lot of code written by other people. Most of the code is quite good and some is even a masterpiece. And there is also code which makes you think WTF… oh it was written by me. Hm not so bad after all. There are many excuses reasons for bad code. Most often it is time pressure followed by not enough ambition (who cares) or insufficient training. Normally I do care about code quality quite a lot which makes me a (perceived) slow worker who does write many tests and refines the code quite a lot because of the design deficiencies. Most of the deficiencies I do find by putting my design under stress while checking for invariants. It does also help a lot to step into the code with a debugger (sometimes also Windbg). I do this much more often when my tests are red. That way I do get a much better understanding what my code really does and not what I think it should be doing. This time I do want to show you how code can evolve over the years with different .NET Framework versions. Once there was  time where .NET 1.1 was new and many C++ programmers did switch over to get rid of not initialized pointers and memory leaks. There were also nice new data structures available such as the Hashtable which is fast lookup table with O(1) time complexity. All was good and much code was written since then. At 2005 a new version of the .NET Framework did arrive which did bring many new things like generics and new data structures. The “old” fashioned way of Hashtable were coming to an end and everyone used the new Dictionary<xx,xx> type instead which was type safe and faster because the object to type conversion (aka boxing) was no longer necessary. I think 95% of all Hashtables and dictionaries use string as key. Often it is convenient to ignore casing to make it easy to look up values which the user did enter. An often followed route is to convert the string to upper case before putting it into the Hashtable. Hashtable Table = new Hashtable(); void Add(string key, string value) { Table.Add(key.ToUpper(), value); } This is valid and working code but it has problems. First we can pass to the Hashtable a custom IEqualityComparer to do the string matching case insensitive. Second we can switch over to the now also old Dictionary type to become a little faster and we can keep the the original keys (not upper cased) in the dictionary. Dictionary<string, string> DictTable = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase); void AddDict(string key, string value) { DictTable.Add(key, value); } Many people do not user the other ctors of Dictionary because they do shy away from the overhead of writing their own comparer. They do not know that .NET has for strings already predefined comparers at hand which you can directly use. Today in the many core area we do use threads all over the place. Sometimes things break in subtle ways but most of the time it is sufficient to place a lock around the offender. Threading has become so mainstream that it may sound weird that in the year 2000 some guy got a huge incentive for the idea to reduce the time to process calibration data from 12 hours to 6 hours by using two threads on a dual core machine. Threading does make it easy to become faster at the expense of correctness. Correct and scalable multithreading can be arbitrarily hard to achieve depending on the problem you are trying to solve. Lets suppose we want to process millions of items with two threads and count the processed items processed by all threads. A typical beginners code might look like this: int Counter; void IJustLearnedToUseThreads() { var t1 = new Thread(ThreadWorkMethod); t1.Start(); var t2 = new Thread(ThreadWorkMethod); t2.Start(); t1.Join(); t2.Join(); if (Counter != 2 * Increments) throw new Exception("Hmm " + Counter + " != " + 2 * Increments); } const int Increments = 10 * 1000 * 1000; void ThreadWorkMethod() { for (int i = 0; i < Increments; i++) { Counter++; } } It does throw an exception with the message e.g. “Hmm 10.222.287 != 20.000.000” and does never finish. The code does fail because the assumption that Counter++ is an atomic operation is wrong. The ++ operator is just a shortcut for Counter = Counter + 1 This does involve reading the counter from a memory location into the CPU, incrementing value on the CPU and writing the new value back to the memory location. When we do look at the generated assembly code we will see only inc dword ptr [ecx+10h] which is only one instruction. Yes it is one instruction but it is not atomic. All modern CPUs have several layers of caches (L1,L2,L3) which try to hide the fact how slow actual main memory accesses are. Since cache is just another word for redundant copy it can happen that one CPU does read a value from main memory into the cache, modifies it and write it back to the main memory. The problem is that at least the L1 cache is not shared between CPUs so it can happen that one CPU does make changes to values which did change in meantime in the main memory. From the exception you can see we did increment the value 20 million times but half of the changes were lost because we did overwrite the already changed value from the other thread. This is a very common case and people do learn to protect their  data with proper locking.   void Intermediate() { var time = Stopwatch.StartNew(); Action acc = ThreadWorkMethod_Intermediate; var ar1 = acc.BeginInvoke(null, null); var ar2 = acc.BeginInvoke(null, null); ar1.AsyncWaitHandle.WaitOne(); ar2.AsyncWaitHandle.WaitOne(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Intermediate did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Intermediate() { for (int i = 0; i < Increments; i++) { lock (this) { Counter++; } } } This is better and does use the .NET Threadpool to get rid of manual thread management. It does give the expected result but it can result in deadlocks because you do lock on this. This is in general a bad idea since it can lead to deadlocks when other threads use your class instance as lock object. It is therefore recommended to create a private object as lock object to ensure that nobody else can lock your lock object. When you read more about threading you will read about lock free algorithms. They are nice and can improve performance quite a lot but you need to pay close attention to the CLR memory model. It does make quite weak guarantees in general but it can still work because your CPU architecture does give you more invariants than the CLR memory model. For a simple counter there is an easy lock free alternative present with the Interlocked class in .NET. As a general rule you should not try to write lock free algos since most likely you will fail to get it right on all CPU architectures. void Experienced() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); t1.Wait(); t2.Wait(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Experienced did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Experienced() { for (int i = 0; i < Increments; i++) { Interlocked.Increment(ref Counter); } } Since time does move forward we do not use threads explicitly anymore but the much nicer Task abstraction which was introduced with .NET 4 at 2010. It is educational to look at the generated assembly code. The Interlocked.Increment method must be called which does wondrous things right? Lets see: lock inc dword ptr [eax] The first thing to note that there is no method call at all. Why? Because the JIT compiler does know very well about CPU intrinsic functions. Atomic operations which do lock the memory bus to prevent other processors to read stale values are such things. Second: This is the same increment call prefixed with a lock instruction. The only reason for the existence of the Interlocked class is that the JIT compiler can compile it to the matching CPU intrinsic functions which can not only increment by one but can also do an add, exchange and a combined compare and exchange operation. But be warned that the correct usage of its methods can be tricky. If you try to be clever and look a the generated IL code and try to reason about its efficiency you will fail. Only the generated machine code counts. Is this the best code we can write? Perhaps. It is nice and clean. But can we make it any faster? Lets see how good we are doing currently. Level Time in s IJustLearnedToUseThreads Flawed Code Intermediate 1,5 (lock) Experienced 0,3 (Interlocked.Increment) Master 0,1 (1,0 for int[2]) That lock free thing is really a nice thing. But if you read more about CPU cache, cache coherency, false sharing you can do even better. int[] Counters = new int[12]; // Cache line size is 64 bytes on my machine with an 8 way associative cache try for yourself e.g. 64 on more modern CPUs void Master() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Master, 0); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Master, Counters.Length - 1); t1.Wait(); t2.Wait(); Counter = Counters[0] + Counters[Counters.Length - 1]; if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Master did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Master(object number) { int index = (int) number; for (int i = 0; i < Increments; i++) { Counters[index]++; } } The key insight here is to use for each core its own value. But if you simply use simply an integer array of two items, one for each core and add the items at the end you will be much slower than the lock free version (factor 3). Each CPU core has its own cache line size which is something in the range of 16-256 bytes. When you do access a value from one location the CPU does not only fetch one value from main memory but a complete cache line (e.g. 16 bytes). This means that you do not pay for the next 15 bytes when you access them. This can lead to dramatic performance improvements and non obvious code which is faster although it does have many more memory reads than another algorithm. So what have we done here? We have started with correct code but it was lacking knowledge how to use the .NET Base Class Libraries optimally. Then we did try to get fancy and used threads for the first time and failed. Our next try was better but it still had non obvious issues (lock object exposed to the outside). Knowledge has increased further and we have found a lock free version of our counter which is a nice and clean way which is a perfectly valid solution. The last example is only here to show you how you can get most out of threading by paying close attention to your used data structures and CPU cache coherency. Although we are working in a virtual execution environment in a high level language with automatic memory management it does pay off to know the details down to the assembly level. Only if you continue to learn and to dig deeper you can come up with solutions no one else was even considering. I have studied particle physics which does help at the digging deeper part. Have you ever tried to solve Quantum Chromodynamics equations? Compared to that the rest must be easy ;-). Although I am no longer working in the Science field I take pride in discovering non obvious things. This can be a very hard to find bug or a new way to restructure data to make something 10 times faster. Now I need to get some sleep ….

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• how to compare/validate sql schema

  - by Ron Harlev

  I'm looking for a way to validate the SQL schema on a production DB after updating an application version. If the application does not match the DB schema version, there should be a way to warn the user and list the changes needed. Is there a tool or a framework (to use programatically) with built-in features to do that? Or is there some simple algorithm to run this comparison? Update: Red gate lists "from $395". Anything free? Or more foolproof than just keeping the version number?

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• Can you use Github App with Beanstalk?

  - by mikemick

  Being new to Git, I wanted to use a GUI (Windows based) and preferred the Github App. However, I would like to integrate this site with a Beanstalkapp account. I'm pretty sure this is possible, but I can't figure it out. Inside of the Github app, I navigate to my repository. When I choose "Tools Settings...", I place the Git Clone URL for the repository provided by Beanstalk into the "Primary Remote (origin)" field in my Github app. Now when I click "Publish" (which says "Click to publish this branch to server" when I hover over it) it changes to "Publishing...". After a few seconds, I get this error: server failure The remote server disconnected. Try again later, or if this persists, contact [email protected] I am pretty sure I set the SSH keys up properly (never done this before). I added the key to both the Beanstalkapp and my Github web account.

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• Preventing spam bots on site?

  - by Mike

  We're having an issue on one of our fairly large websites with spam bots. It appears the bots are creating user accounts and then posting journal entries which lead to various spam links. It appears they are bypassing our captcha somehow -- either it's been cracked or they're using another method to create accounts. We're looking to do email activation for the accounts, but we're about a week away from implementing such changes (due to busy schedules). However, I don't feel like this will be enough if they're using an SQL exploit somewhere on the site and doing the whole cross site scripting thing. So my question to you: If they are using some kind of XSS exploit, how can I find it? I'm securing statements where I can but, again, its a fairly large site and it'd take me awhile to actively clean up SQL statements to prevent XSS. Can you recommend anything to help our situation?

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