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  • How to avoid Memory "Hard Fault/sec"

    - by Flavio Oliveira
    i've a problem on my windows 2008 server x64, and i cannot understand how can i solve it. i'm looking to Resource Monitor and see about 100 to 200 hard faults/sec. and generally the machine is slow. As i've readed a bit it is caused by a "memory Page" that is no longer available on physical memory and causes a io operations (disk) and it is a problem. The current hardware is a intel core2duo E8400 (3.0GHz) with 6GB RAM on a Windows Server Web 64-bit. Actually the machine have about 2GB Ram used what having 4Gb available to use, Why is the machine requires that high level of Disk operations? what can i do to increase the performance? Im experiencing a memory issues? what should be my starting point?

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  • How to protect compiled Java classes?

    - by Registered User
    I know, many similar questions has been asked here. I am not asking if I can protect my compiled Java class - because obviously you will say 'no you can't'. I am asking what is the best known method of protecting Java classes against de-compiling? If you aware of any research or academic paper in this field please do let me know. Also if you have used some methods or software please share you experience? Any kind of information will be very useful. Thank you.

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  • How can I hide tracing code in Visual Studio IDE C# ?

    - by Mark
    As I'm starting to put more tracing in my code, i'm realizing it adds a lot of clutter. I know Visual Studio allows you to hide and reveal code, however, i'd like to be able group code into "tracing" code and then hide it and reveal at will as i'm reading the code. I suppose it could do this either per file or per class or per function. Is there any way to do this? What do you guys do? Adding some clarification The hide current feature kind of allows you to do this except that when the code is hidden, you can't tell if its tracing or not. You also can't say "hide all tracing code" and "reveal all tracing code" which is useful when reading a function depending on what you are trying to do.

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  • Using Entity Framework (code first) migrations in production

    - by devdigital
    I'm just looking into using EF migrations for our project, and in particular for performing schema changes in production between releases. I can see that generating SQL (delta) script files is an option, but is there no way of running the migrations programmatically on app start up? Will I instead need to add each delta script to the solution and write my own framework to apply them in order (from the current version to the latest) on bootstrap?

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  • SQL server peformance, virtual memory usage

    - by user45641
    Hello, I have a very large DB used mostly for analytics. The performance overall is very sluggish. I just noticed that when running the query below, the amount of virtual memory used greatly exceeds the amount of physical memory available. Currently, physical memory is 10GB (10238 MB) whereas the virtual memory returns significantly more - 8388607 MB. That seems really wrong, but I'm at a bit of a loss on how to proceed. USE [master]; GO select cpu_count , hyperthread_ratio , physical_memory_in_bytes / 1048576 as 'mem_MB' , virtual_memory_in_bytes / 1048576 as 'virtual_mem_MB' , max_workers_count , os_error_mode , os_priority_class from sys.dm_os_sys_info

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  • Benchmarking Java programs

    - by stefan-ock
    For university, I perform bytecode modifications and analyze their influence on performance of Java programs. Therefore, I need Java programs---in best case used in production---and appropriate benchmarks. For instance, I already got HyperSQL and measure its performance by the benchmark program PolePosition. The Java programs running on a JVM without JIT compiler. Thanks for your help! P.S.: I cannot use programs to benchmark the performance of the JVM or of the Java language itself (such as Wide Finder).

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  • Ideas for my MSc project and Google Summer of Code 2011

    - by Chris Wilson
    I'm currently putting together ideas for my master's project which I'll be working on over the summer, and I would like to be able to use this time to help Ubuntu in some way. I have the freedom to come up with pretty much any project in the field of software development/engineering provided it Is a substantial piece of software (for reference, I will be working on it for five full months) Solves a problem for more people than just myself I was hoping to use this project as an opportunity to get some experience with the underbelly of Linux, so that I can mention on my CV that I have 'experience in developing for *NIX in C++', which I'm noticing more and more companies are looking for these days, probably because stuff's moving to cloud servers and that's where Linux rules the roost. My problem is that, since I don't have the experience to begin with, I'm not sure what to do for such a project, and I was wondering if anyone could help me with this. I've noticed from Daniel Holbach's blog that Ubuntu participated in the Google Summer of Code 2010, and that project ideas for that can be found here. However, I have not been able to find anything related to Ubuntu and GSoC 2011, but I have noticed from the GSoC timeline that the list of mentoring organisations will not be published until March 18th. I have two questions here. Has Ubuntu applied to be a part of Summer of Code 2011, and what is the status of the 2010 project list linked to earlier. Were they all implemented or are there still some that can be picked up now, should I not participate in GSoC? I'd like to do something for Ubuntu, but I'd rather not spend my time reinventing the wheel.

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  • Collision Detection Code Structure with Sloped Tiles

    - by ProgrammerGuy123
    Im making a 2D tile based game with slopes, and I need help on the collision detection. This question is not about determining the vertical position of the player given the horizontal position when on a slope, but rather the structure of the code. Here is my pseudocode for the collision detection: void Player::handleTileCollisions() { int left = //find tile that's left of player int right = //find tile that's right of player int top = //find tile that's above player int bottom = //find tile that's below player for(int x = left; x <= right; x++) { for(int y = top; y <= bottom; y++) { switch(getTileType(x, y)) { case 1: //solid tile { //resolve collisions break; } case 2: //sloped tile { //resolve collisions break; } default: //air tile or whatever else break; } } } } When the player is on a sloped tile, he is actually inside the tile itself horizontally, that way the player doesn't look like he is floating. This creates a problem because when there is a sloped tile next to a solid square tile, the player can't move passed it because this algorithm resolves any collisions with the solid tile. Here is a gif showing this problem: So what is a good way to structure my code so that when the player is inside a sloped tile, solid tiles get ignored?

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  • Is a code review which uses only code comments a good idea?

    - by gaRex
    Preconditions Team uses DVCS IDE supports comments parsing (like TODO and etc.) Tools like CodeCollaborator are expensive for budget Tools like gerrit are too complex for install or not usable Workflow Author publishes somewhere on central repo feature branch Reviewer fetch it and start review In case of some question/issue reviewer create comment with special label, like "REV". Such label MUST not be in production code -- only on review stage: $somevar = 123; // REV Why do echo this here? echo $somevar; When reviewer finish post comments -- it just commits with stupid message "comments" and pushes back Author pulls feature branch back and answer comments in similar way or improve code and push it back When "REV" comments have gone we can think, that review has successfully finished. Author interactively rebases feature branch, squashes it to remove those "comment" commits and now is ready to merge feature to develop or make any action that usualy could be after successful internal review IDE support I know, that custom comment tags are possible in eclipse & netbeans. Sure it also should be in blablaStorm family. Questions Do you think this methodology is viable? Do you know something similar? What can be improved in it?

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  • Macedonian Code Camp 2011

    - by hajan
    Autumn was filled with lot of conferences, events, speaking engagements and many interesting happenings in Skopje, Macedonia. First at October 20, I was speaking at Microsoft Vizija 9 on topic ASP.NET MVC3 and Razor. One week ago, November 15 I was speaking for first time on topic not related to web development (but still deployment of web apps was part of the demos) on topic “Cloud Computing – Windows Azure” at Microsoft BizSpark Bootcamp. The next event, which is the biggest event by the number of visitors and number of tracks is the Code Camp 2011 event. After we opened the registrations for the event, we sold out (free) 600 tickets in the first 15 hours! We all got astonished by the extremely big number of responses we’ve got… In this event, I can freely say that we expect about 700 attendees to come, and we already have 900+ registered. The event will be held at Saturday, 26 November 2011. At Code Camp 2011, I will speak on topic ASP.NET MVC Best Practices. There are many interesting things to say on this presentation, I will mainly focus on Tips, Tricks, Guidelines and other Practices that I have been using in real-life projects developed by using ASP.NET MVC Framework, with special focus on ASP.NET MVC3 and the next release, ASP.NET MVC4 Developer Preview. There are big number of known local and regional speakers, including 7 MVPs. You can find more info about this event at the official event website: http://codecamp.mkdot.net As for my session, if you have some interesting trick or good practice you have been using in your ASP.NET MVC projects, you can freely share it with me… If I find it interesting and if it’s not part of the current practices I have included for the presentation (I can’t tell you which ones for now… *secret* ;))… I will consider including it in the presentation. Stay tuned for more info soon… Regards, Hajan

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  • How to turn on/off code modules?

    - by Safran Ali
    I am trying to run multiple sites using single code base and code base consist of the following module (i.e. classes) User module Q & A module Faq module and each class works on MVC pattern i.e. it consist of Entity class Helper class (i.e. static class) View (i.e. pages and controls) and let's say I have 2 sites site1.com and site2.com. And I am trying to achieve following functionality site1.com can have User, Q & A and Faq module up and running site2.com can have User and Q & A module live while Faq module is switched off but it can be turned-on if needed, so my query here is what is the best way to achieve such functionality Do I introduce a flag bit that I check on every page and control belonging to that module? It's more like CMS where you can turn on/off different features. I am trying to get my head around it, please provide me with an example or point out if I am taking the wrong approach.

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  • How to ignore certain coding standard errors in PHP CodeSniffer

    - by Tom
    We have a PHP 5 web application and we're currently evaluating PHP CodeSniffer in order to decide whether forcing code standards improves code quality without causing too much of a headache. If it seems good we will add a SVN pre-commit hook to ensure all new files committed on the dev branch are free from coding standard smells. Is there a way to configure PHP codeSniffer to ignore a particular type of error? or get it to treat a certain error as a warning instead? Here an example to demonstrate the issue: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> </head> <body> <div> <?php echo getTabContent('Programming', 1, $numX, $numY); if (isset($msg)) { echo $msg; } ?> </div> </body> </html> And this is the output of PHP_CodeSniffer: > phpcs test.php -------------------------------------------------------------------------------- FOUND 2 ERROR(S) AND 1 WARNING(S) AFFECTING 3 LINE(S) -------------------------------------------------------------------------------- 1 | WARNING | Line exceeds 85 characters; contains 121 characters 9 | ERROR | Missing file doc comment 11 | ERROR | Line indented incorrectly; expected 0 spaces, found 4 -------------------------------------------------------------------------------- I have a issue with the "Line indented incorrectly" error. I guess it happens because I am mixing the PHP indentation with the HTML indentation. But this makes it more readable doesn't it? (taking into account that I don't have the resouces to move to a MVC framework right now). So I'd like to ignore it please.

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  • Are there any actual case studies on rewrites of software success/failure rates?

    - by James Drinkard
    I've seen multiple posts about rewrites of applications being bad, peoples experiences about it here on Programmers, and an article I've ready by Joel Splosky on the subject, but no hard evidence of case studies. Other than the two examples Joel gave and some other posts here, what do you do with a bad codebase and how do you decide what to do with it based on real studies? For the case in point, there are two clients I know of that both have old legacy code. They keep limping along with it because as one of them found out, a rewrite was a disaster, it was expensive and didn't really work to improve the code much. That customer has some very complicated business logic as the rewriters quickly found out. In both cases, these are mission critical applications that brings in a lot of revenue for the company. The one that attempted the rewrite felt that they would hit a brick wall at some point if the legacy software didn't get upgraded at some point in the future. To me, that kind of risk warrants research and analysis to ensure a successful path. My question is have there been actual case studies that have investigated this? I wouldn't want to attempt a major rewrite without knowing some best practices, pitfalls, and successes based on actual studies. Aftermath: okay, I was wrong, I did find one article: Rewrite or Reuse. They did a study on a Cobol app that was converted to Java.

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  • Augmenting functionality of subclasses without code duplication in C++

    - by Rob W
    I have to add common functionality to some classes that share the same superclass, preferably without bloating the superclass. The simplified inheritance chain looks like this: Element -> HTMLElement -> HTMLAnchorElement Element -> SVGElement -> SVGAlement The default doSomething() method on Element is no-op by default, but there are some subclasses that need an actual implementation that requires some extra overridden methods and instance members. I cannot put a full implementation of doSomething() in Element because 1) it is only relevant for some of the subclasses, 2) its implementation has a performance impact and 3) it depends on a method that could be overridden by a class in the inheritance chain between the superclass and a subclass, e.g. SVGElement in my example. Especially because of the third point, I wanted to solve the problem using a template class, as follows (it is a kind of decorator for classes): struct Element { virtual void doSomething() {} }; // T should be an instance of Element template<class T> struct AugmentedElement : public T { // doSomething is expensive and uses T virtual void doSomething() override {} // Used by doSomething virtual bool shouldDoSomething() = 0; }; class SVGElement : public Element { /* ... */ }; class SVGAElement : public AugmentedElement<SVGElement> { // some non-trivial check bool shouldDoSomething() { /* ... */ return true; } }; // Similarly for HTMLAElement and others I looked around (in the existing (huge) codebase and on the internet), but didn't find any similar code snippets, let alone an evaluation of the effectiveness and pitfalls of this approach. Is my design the right way to go, or is there a better way to add common functionality to some subclasses of a given superclass?

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  • Breaking up classes and methods into smaller units

    - by micahhoover
    During code reviews a couple devs have recommended I break up my methods into smaller methods. Their justification was (1) increased readability and (2) the back trace that comes back from production showing the method name is more specific to the line of code that failed. There may have also been some colorful words about functional programming. Additionally I think I may have failed an interview a while back because I didn't give an acceptable answer about when to break things up. My inclination is that when I see a bunch of methods in a class or across a bunch of files, it isn't clear to me how they flow together, and how many times each one gets called. I don't really have a good feel for the linearity of it as quickly just by eye-balling it. The other thing is a lot of people seem to place a premium of organization over content (e.g. 'Look at how organized my sock drawer is!' Me: 'Overall, I think I can get to my socks faster if you count the time it took to organize them'). Our business requirements are not very stable. I'm afraid that if the classes/methods are very granular it will take longer to refactor to requirement changes. I'm not sure how much of a factor this should be. Anyway, computer science is part art / part science, but I'm not sure how much this applies to this issue.

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  • Can compressing Program Files save space *and* give a significant boost to SSD performance?

    - by Christopher Galpin
    Considering solid-state disk space is still an expensive resource, compressing large folders has appeal. Thanks to VirtualStore, could Program Files be a case where it might even improve performance? Discovery In particular I have been reading: SSD and NTFS Compression Speed Increase? Does NTFS compression slow SSD/flash performance? Will somebody benchmark whole disk compression (HD,SSD) please? (may have to scroll up) The first link is particularly dreamy, but maybe head a little too far in the clouds. The third link has this sexy semi-log graph (logarithmic scale!). Quote (with notes): Using highly compressable data (IOmeter), you get at most a 30x performance increase [for reads], and at least a 49x performance DECREASE [for writes]. Assuming I interpreted and clarified that sentence correctly, this single user's benchmark has me incredibly interested. Although write performance tanks wretchedly, read performance still soars. It gave me an idea. Idea: VirtualStore It so happens that thanks to sanity saving security features introduced in Windows Vista, write access to certain folders such as Program Files is virtualized for non-administrator processes. Which means, in normal (non-elevated) usage, a program or game's attempt to write data to its install location in Program Files (which is perhaps a poor location) is redirected to %UserProfile%\AppData\Local\VirtualStore, somewhere entirely different. Thus, to my understanding, writes to Program Files should primarily only occur when installing an application. This makes compressing it not only a huge source of space gain, but also a potential candidate for performance gain. Testing The beginning of this post has me a bit timid, it suggests benchmarking NTFS compression on a whole drive is difficult because turning it off "doesn't decompress the objects". However it seems to me the compact command is perfectly capable of doing so for both drives and individual folders. Could it be only marking them for decompression the next time the OS reads from them? I need to find the answer before I begin my own testing.

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  • Performance question: Inverting an array of pointers in-place vs array of values

    - by Anders
    The background for asking this question is that I am solving a linearized equation system (Ax=b), where A is a matrix (typically of dimension less than 100x100) and x and b are vectors. I am using a direct method, meaning that I first invert A, then find the solution by x=A^(-1)b. This step is repated in an iterative process until convergence. The way I'm doing it now, using a matrix library (MTL4): For every iteration I copy all coeffiecients of A (values) in to the matrix object, then invert. This the easiest and safest option. Using an array of pointers instead: For my particular case, the coefficients of A happen to be updated between each iteration. These coefficients are stored in different variables (some are arrays, some are not). Would there be a potential for performance gain if I set up A as an array containing pointers to these coefficient variables, then inverting A in-place? The nice thing about the last option is that once I have set up the pointers in A before the first iteration, I would not need to copy any values between successive iterations. The values which are pointed to in A would automatically be updated between iterations. So the performance question boils down to this, as I see it: - The matrix inversion process takes roughly the same amount of time, assuming de-referencing of pointers is non-expensive. - The array of pointers does not need the extra memory for matrix A containing values. - The array of pointers option does not have to copy all NxN values of A between each iteration. - The values that are pointed to the array of pointers option are generally NOT ordered in memory. Hopefully, all values lie relatively close in memory, but *A[0][1] is generally not next to *A[0][0] etc. Any comments to this? Will the last remark affect performance negatively, thus weighing up for the positive performance effects?

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  • Creating packages in code - Package Configurations

    Continuing my theme of building various types of packages in code, this example shows how to building a package with package configurations. Incidentally it shows you how to add a variable, and a connection too. It covers the five most common configurations: Configuration File Indirect Configuration File SQL Server Indirect SQL Server Environment Variable  For a general overview try the SQL Server Books Online Package Configurations topic. The sample uses a a simple helper function ApplyConfig to create or update a configuration, although in the example we will only ever create. The most useful knowledge is the configuration string (Configuration.ConfigurationString) that you need to set. Configuration Type Configuration String Description Configuration File The full path and file name of an XML configuration file. The file can contain one or more configuration and includes the target path and new value to set. Indirect Configuration File An environment variable the value of which contains full path and file name of an XML configuration file as per the Configuration File type described above. SQL Server A three part configuration string, with each part being quote delimited and separated by a semi-colon. -- The first part is the connection manager name. The connection tells you which server and database to look for the configuration table. -- The second part is the name of the configuration table. The table is of a standard format, use the Package Configuration Wizard to help create an example, or see the sample script files below. The table contains one or more rows or configuration items each with a target path and new value. -- The third and final part is the optional filter name. A configuration table can contain multiple configurations, and the filter is  literal value that can be used to group items together and act as a filter clause when configurations are being read. If you do not need a filter, just leave the value empty. Indirect SQL Server An environment variable the value of which is the three part configuration string as per the SQL Server type described above. Environment Variable An environment variable the value of which is the value to set in the package. This is slightly different to the other examples as the configuration definition in the package also includes the target information. In our ApplyConfig function this is the only example that actually supplies a target value for the Configuration.PackagePath property. The path is an XPath style path for the target property, \Package.Variables[User::Variable].Properties[Value], the equivalent of which can be seen in the screenshot below, with the object being our variable called Variable, and the property to set is the Value property of that variable object. The configurations as seen when opening the generated package in BIDS: The sample code creates the package, adds a variable and connection manager, enables configurations, and then adds our example configurations. The package is then saved to disk, useful for checking the package and testing, before finally executing, just to prove it is valid. There are some external resources used here, namely some environment variables and a table, see below for more details. namespace Konesans.Dts.Samples { using System; using Microsoft.SqlServer.Dts.Runtime; public class PackageConfigurations { public void CreatePackage() { // Create a new package Package package = new Package(); package.Name = "ConfigurationSample"; // Add a variable, the target for our configurations package.Variables.Add("Variable", false, "User", 0); // Add a connection, for SQL configurations // Add the SQL OLE-DB connection ConnectionManager connectionManagerOleDb = package.Connections.Add("OLEDB"); connectionManagerOleDb.Name = "SQLConnection"; connectionManagerOleDb.ConnectionString = "Provider=SQLOLEDB.1;Data Source=(local);Initial Catalog=master;Integrated Security=SSPI;"; // Add our example configurations, first must enable package setting package.EnableConfigurations = true; // Direct configuration file, see sample file this.ApplyConfig(package, "Configuration File", DTSConfigurationType.ConfigFile, "C:\\Temp\\XmlConfig.dtsConfig", string.Empty); // Indirect configuration file, the emvironment variable XmlConfigFileEnvironmentVariable // contains the path to the configuration file, e.g. C:\Temp\XmlConfig.dtsConfig this.ApplyConfig(package, "Indirect Configuration File", DTSConfigurationType.IConfigFile, "XmlConfigFileEnvironmentVariable", string.Empty); // Direct SQL Server configuration, uses the SQLConnection package connection to read // configurations from the [dbo].[SSIS Configurations] table, with a filter of "SampleFilter" this.ApplyConfig(package, "SQL Server", DTSConfigurationType.SqlServer, "\"SQLConnection\";\"[dbo].[SSIS Configurations]\";\"SampleFilter\";", string.Empty); // Indirect SQL Server configuration, the environment variable "SQLServerEnvironmentVariable" // contains the configuration string e.g. "SQLConnection";"[dbo].[SSIS Configurations]";"SampleFilter"; this.ApplyConfig(package, "Indirect SQL Server", DTSConfigurationType.ISqlServer, "SQLServerEnvironmentVariable", string.Empty); // Direct environment variable, the value of the EnvironmentVariable environment variable is // applied to the target property, the value of the "User::Variable" package variable this.ApplyConfig(package, "EnvironmentVariable", DTSConfigurationType.EnvVariable, "EnvironmentVariable", "\\Package.Variables[User::Variable].Properties[Value]"); #if DEBUG // Save package to disk, DEBUG only new Application().SaveToXml(String.Format(@"C:\Temp\{0}.dtsx", package.Name), package, null); Console.WriteLine(@"C:\Temp\{0}.dtsx", package.Name); #endif // Execute package package.Execute(); // Basic check for warnings foreach (DtsWarning warning in package.Warnings) { Console.WriteLine("WarningCode : {0}", warning.WarningCode); Console.WriteLine(" SubComponent : {0}", warning.SubComponent); Console.WriteLine(" Description : {0}", warning.Description); Console.WriteLine(); } // Basic check for errors foreach (DtsError error in package.Errors) { Console.WriteLine("ErrorCode : {0}", error.ErrorCode); Console.WriteLine(" SubComponent : {0}", error.SubComponent); Console.WriteLine(" Description : {0}", error.Description); Console.WriteLine(); } package.Dispose(); } /// <summary> /// Add or update an package configuration. /// </summary> /// <param name="package">The package.</param> /// <param name="name">The configuration name.</param> /// <param name="type">The type of configuration</param> /// <param name="setting">The configuration setting.</param> /// <param name="target">The target of the configuration, leave blank if not required.</param> internal void ApplyConfig(Package package, string name, DTSConfigurationType type, string setting, string target) { Configurations configurations = package.Configurations; Configuration configuration; if (configurations.Contains(name)) { configuration = configurations[name]; } else { configuration = configurations.Add(); } configuration.Name = name; configuration.ConfigurationType = type; configuration.ConfigurationString = setting; configuration.PackagePath = target; } } } The following table lists the environment variables required for the full example to work along with some sample values. Variable Sample value EnvironmentVariable 1 SQLServerEnvironmentVariable "SQLConnection";"[dbo].[SSIS Configurations]";"SampleFilter"; XmlConfigFileEnvironmentVariable C:\Temp\XmlConfig.dtsConfig Sample code, package and configuration file. ConfigurationApplication.cs ConfigurationSample.dtsx XmlConfig.dtsConfig

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  • Performance impact: What is the optimal payload for SqlBulkCopy.WriteToServer()?

    - by Linchi Shea
    For many years, I have been using a C# program to generate the TPC-C compliant data for testing. The program relies on the SqlBulkCopy class to load the data generated by the program into the SQL Server tables. In general, the performance of this C# data loader is satisfactory. Lately however, I found myself in a situation where I needed to generate a much larger amount of data than I typically do and the data needed to be loaded within a confined time frame. So I was driven to look into the code...(read more)

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  • Should you use "internal abbreviations" in code comments?

    - by Anto
    Should you use "internal abbreviations/slang" inside comments, that is, abbreviations and slang people outside the project could have trouble understanding, for instance, using something like //NYI instead of //Not Yet Implemented? There are advantages of this, such as there is less "code" to type (though you could use autocomplete on the abbreviations) and you can read something like NYE faster than something like Not Yet Implemented, assuming you are aware of the abbreviation and its (unabbreviated) meaning. Myself, I would be careful with this as long as it is not a project on which I for sure will be the only developer.

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  • When does 'optimizing code' == 'structuring data'?

    - by NewAlexandria
    A recent article by ycombinator lists a comment with principles of a great programmer. #7. Good programmer: I optimize code. Better programmer: I structure data. Best programmer: What's the difference? Acknowledging subjective and contentious concepts - does anyone have a position on what this means? I do, but I'd like to edit this question later with my thoughts so-as not to predispose the answers.

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  • Using public domain source code from JDK in my application

    - by user2941369
    Can I use source code from ThreadPoolExecutor.java taken from JDK 1.7 considering that the following clausule is at the beginning of the ThreadPoolExecutor.java: /* * Written by Doug Lea with assistance from members of JCP JSR-166 * Expert Group and released to the public domain, as explained at * http://creativecommons.org/licenses/publicdomain */ And just before that there is also: /* * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */

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  • How can i manage my personal notes , code snippets files in one place online [closed]

    - by user1758043
    Whenever i work on any project , then i have so much notes , diagrams files , image s, brainstorming ideas which i want to keep. i want to put them in one place so that i can see the history of my work. Is there any toll whichere i can store this online. my company is using confluence but thats costly for me. I want something for single user but online in clou where i can store Notes Code snippets Diagrams , flowchart Attah files , images Books marks , sites

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  • Performance triage

    - by Dave
    Folks often ask me how to approach a suspected performance issue. My personal strategy is informed by the fact that I work on concurrency issues. (When you have a hammer everything looks like a nail, but I'll try to keep this general). A good starting point is to ask yourself if the observed performance matches your expectations. Expectations might be derived from known system performance limits, prototypes, and other software or environments that are comparable to your particular system-under-test. Some simple comparisons and microbenchmarks can be useful at this stage. It's also useful to write some very simple programs to validate some of the reported or expected system limits. Can that disk controller really tolerate and sustain 500 reads per second? To reduce the number of confounding factors it's better to try to answer that question with a very simple targeted program. And finally, nothing beats having familiarity with the technologies that underlying your particular layer. On the topic of confounding factors, as our technology stacks become deeper and less transparent, we often find our own technology working against us in some unexpected way to choke performance rather than simply running into some fundamental system limit. A good example is the warm-up time needed by just-in-time compilers in Java Virtual Machines. I won't delve too far into that particular hole except to say that it's rare to find good benchmarks and methodology for java code. Another example is power management on x86. Power management is great, but it can take a while for the CPUs to throttle up from low(er) frequencies to full throttle. And while I love "turbo" mode, it makes benchmarking applications with multiple threads a chore as you have to remember to turn it off and then back on otherwise short single-threaded runs may look abnormally fast compared to runs with higher thread counts. In general for performance characterization I disable turbo mode and fix the power governor at "performance" state. Another source of complexity is the scheduler, which I've discussed in prior blog entries. Lets say I have a running application and I want to better understand its behavior and performance. We'll presume it's warmed up, is under load, and is an execution mode representative of what we think the norm would be. It should be in steady-state, if a steady-state mode even exists. On Solaris the very first thing I'll do is take a set of "pstack" samples. Pstack briefly stops the process and walks each of the stacks, reporting symbolic information (if available) for each frame. For Java, pstack has been augmented to understand java frames, and even report inlining. A few pstack samples can provide powerful insight into what's actually going on inside the program. You'll be able to see calling patterns, which threads are blocked on what system calls or synchronization constructs, memory allocation, etc. If your code is CPU-bound then you'll get a good sense where the cycles are being spent. (I should caution that normal C/C++ inlining can diffuse an otherwise "hot" method into other methods. This is a rare instance where pstack sampling might not immediately point to the key problem). At this point you'll need to reconcile what you're seeing with pstack and your mental model of what you think the program should be doing. They're often rather different. And generally if there's a key performance issue, you'll spot it with a moderate number of samples. I'll also use OS-level observability tools to lock for the existence of bottlenecks where threads contend for locks; other situations where threads are blocked; and the distribution of threads over the system. On Solaris some good tools are mpstat and too a lesser degree, vmstat. Try running "mpstat -a 5" in one window while the application program runs concurrently. One key measure is the voluntary context switch rate "vctx" or "csw" which reflects threads descheduling themselves. It's also good to look at the user; system; and idle CPU percentages. This can give a broad but useful understanding if your threads are mostly parked or mostly running. For instance if your program makes heavy use of malloc/free, then it might be the case you're contending on the central malloc lock in the default allocator. In that case you'd see malloc calling lock in the stack traces, observe a high csw/vctx rate as threads block for the malloc lock, and your "usr" time would be less than expected. Solaris dtrace is a wonderful and invaluable performance tool as well, but in a sense you have to frame and articulate a meaningful and specific question to get a useful answer, so I tend not to use it for first-order screening of problems. It's also most effective for OS and software-level performance issues as opposed to HW-level issues. For that reason I recommend mpstat & pstack as my the 1st step in performance triage. If some other OS-level issue is evident then it's good to switch to dtrace to drill more deeply into the problem. Only after I've ruled out OS-level issues do I switch to using hardware performance counters to look for architectural impediments.

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