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• MySQL index cardinality - performance vs storage efficiency

  - by Sean

  Say you have a MySQL 5.0 MyISAM table with 100 million rows, with one index (other than primary key) on two integer columns. From my admittedly poor understanding of B-tree structure, I believe that a lower cardinality means the storage efficiency of the index is better, because there are less parent nodes. Whereas a higher cardinality means less efficient storage, but faster read performance, because it has to navigate through less branches to get to whatever data it is looking for to narrow down the rows for the query. (Note - by "low" vs "high", I don't mean e.g. 1 million vs 99 million for a 100 million row table. I mean more like 90 million vs 95 million) Is my understanding correct? Related question - How does cardinality affect write performance?

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• Wpf: Tips for better performance

  - by viky

  I am working on a wpf application. In which I am working with a TreeView, each node represents different datatypes, these datatypes are having properties defined and using data template to show their properties. My application reads from xml and create tree accordingly. My problem is that when I load it, it is too slow, I want to know about the tricks that will help me to improve performance of my(any) wpf application. Edit: Please provide me some tips for better performance in wpf!! I am using wpf Profiler but it is not much helpful for me.

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• Performance Improvement: Alternative for array_flip function.

  - by Rachel

  Is there any way I can avoid using array_flip to optimize performance. I am doing a select statement from database, preparing the query and executing it and storing data as an associative array in $resultCollection and than I have array op and for each element in $resultCollection am storing its outputId in op[] as evident from the code. I have explained code and so my question is how can I achieve an similar alternative for array_flip with using array_flip as I want to improve performance. $resultCollection = $statement->fetchAll(PDO::FETCH_ASSOC); $op = array(); //Looping through result collection and storing unicaOfferId into op array. foreach ($resultCollection as $output) { $op[] = $output['outputId']; } //Here op array has key as 0, 1, 2...and value as id {which I am interested in} //Flip op array to get unica offer ids as key $op = array_flip($op); //Doing a flip to get id as key. foreach ($ft as $Id => $Off) { $ft[$Id]['is_set'] = isset($op[$Id]); }

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• oracle database performance tuning

  - by sunil

  hi all, Any one have complete database performance script please post Thanks for your time. sunil

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• Performance logging tips

  - by Germstorm

  I am developing large data collecting ASP.Net/Windows service application-pair that uses Microsoft SQL Server 2005 through LINQ2Sql. Performance is always the issue. Currently the application is divided into multiple larger processing parts, each logging the duration of their work. This is not detailed and does not help us with anything. It would be nice to have some database tables that contain statistics that the application itself collected from its own behavior. What logging tips and data structures do you recommend to spot the parts that cause performance problems?

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• Declarative JDOQL vs Single-String JDOQL : performance

  - by DrDro

  When querying with JDOQL is there a performance difference between using the declarative version and the Single-String version: Example from the JDOQL doc: //Declarative JDOQL : Query q = pm.newQuery(org.jpox.Person.class, "lastName == \"Jones\" && age < age_limit"); q.declareParameters("double age_limit"); List results = (List)q.execute(20.0); //Single-String JDOQL : Query q = pm.newQuery("SELECT FROM org.jpox.Person WHERE lastName == \"Jones\"" + " && age < :age_limit PARAMETERS double age_limit"); List results = (List)q.execute(20.0); Other then performance, are there any reasons for which one is better to use then the other or is it just about the one with which we feel more comfortable.

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• Can GPU capabilities impact virtual machine performance?

  - by Dave White

  While this many not seem like a programming question directly, it impacts my development activities and so it seems like it belongs here. It seems that more and more developers are turning to virtual environments for development activities on their computers, SharePoint development being a prime example. Also, as a trainer, I have virtual training environments for all of the classes that I teach. I recently purchased a new Dell E6510 to travel around with. It has the i7 620M (Dual core, HyperThreaded cpu running at 2.66GHz) and 8 GB of memory. Reading the spec sheet, it sounded like it would be a great laptop to carry around and run virtual machines on. Getting the laptop though, I've been pretty disappointed with the user experience of developing in a virtual machine. Giving the Virtual Machine 4 GB of memory, it was slow and I could type complete sentences and watch the VM "catchup". My company has training laptops that we provide for our classes. They are Dell Precision M6400 Intel Core 2 Duo P8700 running at 2.54Ghz with 8 GB of memory and the experience on this laptops is night and day compared to the E6510. They are crisp and you barely aware that you are running in a virtual environment. Since the E6510 should be faster in all categories than the M6400, I couldn't understand why the new laptop was slower, so I did a component by component comparison and the only place where the E6510 is less performant than the M6400 is the graphics department. The M6400 is running a nVidia FX 2700m GPU and the E6510 is running a nVidia 3100M GPU. Looking at benchmarks of the two GPUs suggest that the FX 2700M is twice as fast as the 3100M. http://www.notebookcheck.net/Mobile-Graphics-Cards-Benchmark-List.844.0.html 3100M = 111th (E6510) FX 2700m = 47th (Precision M6400) Radeon HD 5870 = 8th (Alienware) The host OS is Windows 7 64bit as is the guest OS, running in Virtual Box 3.1.8 with Guest Additions installed on the guest. The IDE being used in the virtual environment is VS 2010 Premium. So after that long setup, my question is: Is the GPU significantly impacting the virtual machine's performance or are there other factors that I'm not looking at that I can use to boost the vm's performance? Do we now have to consider GPU performance when purchasing laptops where we expect to use virtualized development environments? Thanks in advance. Cheers, Dave

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• Performance concern when using LINQ "everywhere"?

  - by stiank81

  After upgrading to ReSharper5 it gives me even more useful tips on code improvements. One I see everywhere now is a tip to replace foreach-statements with LINQ queries. Take this example: private Ninja FindNinjaById(int ninjaId) { foreach (var ninja in Ninjas) { if (ninja.Id == ninjaId) return ninja; } return null; } This is suggested replaced with the following using LINQ: private Ninja FindNinjaById(int ninjaId) { return Ninjas.FirstOrDefault(ninja => ninja.Id == ninjaId); } This looks all fine, and I'm sure it's no problem regarding performance to replace this one foreach. But is it something I should do in general? Or might I run into performance problems with all these LINQ queries everywhere?

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• MYSQL Convert rows to columns performance problem

  - by Tarski

  I am doing a query that converts rows to columns similar to this post but have encountered a performance problem. Here is the query:- SELECT Info.Customer, Answers.Answer, Answers.AnswerDescription, Details.Code1, Details.Code2, Details.Code3 FROM Info LEFT OUTER JOIN Answers ON Info.AnswerID = Answers.AnswerID LEFT OUTER JOIN (SELECT ReferenceNo, MAX(CASE DetailsIndicator WHEN 'cde1' THEN DetailsCode ELSE NULL END ) Code1, MAX(CASE DetailsIndicator WHEN 'cde2' THEN DetailsCode ELSE NULL END ) Code2, MAX(CASE DetailsIndicator WHEN 'cde3' THEN DetailsCode ELSE NULL END ) Code3 FROM DetailsData GROUP BY ReferenceNo) Details ON Info.ReferenceNo = Details.ReferenceNo There are less than 300 rows returned, but the Details table is about 180 thousand rows. The query takes 45 seconds to run and needs to take only a few seconds. When I type show processlist; into MYSQL it is hanging on "Sending Data". Any thoughts as to what the performance problem might be?

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• Performance of .NET ILMerged assemblies

  - by matt

  I have two .NET libraries: "Foo.Bar" and "Foo.Baz". "Foo.Bar" is self-contained, while "Foo.Baz" references "Foo.Bar". Assuming I do the following: Use ILMerge to merge "Foo.Bar.dll" with "Foo.Baz.dll" into "Foo1.dll". Create a new solution containing the entirity of both "Foo.Bar" and "Foo.Baz" (since I have access to their source code), and compile this into "Foo2.dll". Will there be any differences in the performance of Foo1.dll and Foo2.dll when using their functionality from an external project? If so, how significant is this performance difference, and is it a once-off (on load?) or ongoing difference? Are there any other pros or cons with either approach?

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• performance monitoring tools for multi-tenant web application

  - by Anton

  We have a need to monitor performance of our java web app. We are looking for some tolls which can help us with this task. The major difficulty is that we are SaaS provider with multi-tenant server architecture with hundreds of customers running on the same hardware. So far we tried commercial products like DynaTrace and Coradinat but unfortunately they don't get the job done so far. What we need is a simple report which would tell us if we had performance problems on each customer site in a specified period of time. Mostly it will be response time per customer but also we will need some more specifics based on the URLs. please let me know if someone had any experience with setting up such monitoring. Thanks!

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• Apache modules: C module vs mod_wsgi python module - Performance

  - by Gopal

  Hi A client of ours is asking us to implement a module in C in Apache webserver for performance reasons. This module should handle RESTful uri's, access a database and return results in json format. Many people here have recommended python mod_wsgi instead - but for simplicity of programming reasons. Can anyone tell me if there is a significant difference in performance between the mod_wsgi python solution vs. the Apache + C.module. Any anecdotes? Pointers to some study posted online?

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• Visual Studio add-in for performance benchmarking

  - by chiccodoro

  I'd like to measure the performance of some code blocks in my c# winforms application. In particular I want to measure performance regression/improvement after some restructuring of the code. So long I've seen the System.Diagnostics.Stopwatch. However, I want to avoid writing measuring code into my classes, I would rather prefer to separate measuring from actual code. As for debugging, you can set breakpoints on several code lines and "jump" from one to the next by "Continue Execution", I imagine something similar for measuring: Mark to lines of code and make Visual Studio display the time elapsing from one to the next. Is there any feature/add-in in that direction?

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• What's the performance penalty of weak_ptr?

  - by Kornel Kisielewicz

  I'm currently designing a object structure for a game, and the most natural organization in my case became a tree. Being a great fan of smart pointers I use shared_ptr's exclusively. However, in this case, the children in the tree will need access to it's parent (example -- beings on map need to be able to access map data -- ergo the data of their parents. The direction of owning is of course that a map owns it's beings, so holds shared pointers to them. To access the map data from within a being we however need a pointer to the parent -- the smart pointer way is to use a reference, ergo a weak_ptr. However, I once read that locking a weak_ptr is a expensive operation -- maybe that's not true anymore -- but considering that the weak_ptr will be locked very often, I'm concerned that this design is doomed with poor performance. Hence the question: What is the performance penalty of locking a weak_ptr? How significant is it?

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• Performance of Managed C++ Vs UnManaged/native C++

  - by bsobaid

  I am writing a very high performance application that handles and processes hundreds of events every millisecond. Is Unmanaged C++ faster than managed c++? and why? Managed C++ deals with CLR instead of OS and CLR takes care of memory management, which simplifies the code and is probably also more efficient than code written by "a programmer" in unmanaged C++? or there is some other reason? When using managed, how can one then avoid dynamic memory allocation, which causes a performance hit, if it is all transparent to the programmer and handled by CLR? So coming back to my question, Is managed C++ more efficient in terms of speed than unmanaged C++ and why?

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• Approximate timings for various operations on a "typical desktop PC" anno 2010

  - by knorv

  In the article "Teach Yourself Programming in Ten Years" Peter Norvig (Director of Research, Google) gives the following approximate timings for various operations on a typical 1GHz PC back in 2001: execute single instruction = 1 nanosec = (1/1,000,000,000) sec fetch word from L1 cache memory = 2 nanosec fetch word from main memory = 10 nanosec fetch word from consecutive disk location = 200 nanosec fetch word from new disk location (seek) = 8,000,000 nanosec = 8 millisec What would the corresponding timings be for your definition of a typical PC desktop anno 2010?

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• which toString() method can be used performance wise??

  - by Mrityunjay

  hi, I am working on one project for performance enhancement. I had one doubt, while we are during a process, we tend to trace the current state of the DTO and entity used. So, for this we have included toString() method in all POJOs for the same. I have now implemented toString() in three different ways which are following :- public String toString() { return "POJO :" + this.class.getName() + " RollNo :" + this.rollNo + " Name :" + this.name; } public String toString() { StringBuffer buff = new StringBuffer("POJO :").append(this.class.getName()).append(" RollNo :").append(this.rollNo).append(" Name :").append(this.name); return buff.toString(); } public String toString() { StringBuilder builder = new StringBuilder("POJO :").append(this.class.getName()).append(" RollNo :").append(this.rollNo).append(" Name :").append(this.name); return builder .toString(); } can anyone please help me to find out which one is best and should be used for enhancing performance.

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• What are some good code optimization methods?

  - by esac

  I would like to understand good code optimization methods and methodology. How do I keep from doing premature optimization if I am thinking about performance already. How do I find the bottlenecks in my code? How do I make sure that over time my program does not become any slower? What are some common performance errors to avoid (e.g.; I know it is bad in some languages to return while inside the catch portion of a try{} catch{} block

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• C# debug vs release performance

  - by sagie

  Hi. I've encountered in the following paragraph: “Debug vs Release setting in the IDE when you compile your code in Visual Studio makes almost no difference to performance… the generated code is almost the same. The C# compiler doesn’t really do any optimisation. The C# compiler just spits out IL… and at the runtime it’s the JITer that does all the optimisation. The JITer does have a Debug/Release mode and that makes a huge difference to performance. But that doesn’t key off whether you run the Debug or Release configuration of your project, that keys off whether a debugger is attached.” The source is here and the podcast is here. Can someone direct me to a microsoft an article that can actualy prove this?

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• OpenGL Performance Questions

  - by Daniel

  This subject, as with any optimisation problem, gets hit on a lot, but I just couldn't find what I (think) I want. A lot of tutorials, and even SO questions have similar tips; generally covering: Use GL face culling (the OpenGL function, not the scene logic) Only send 1 matrix to the GPU (projectionModelView combination), therefore decreasing the MVP calculations from per vertex to once per model (as it should be). Use interleaved Vertices Minimize as many GL calls as possible, batch where appropriate And possibly a few/many others. I am (for curiosity reasons) rendering 28 million triangles in my application using several vertex buffers. I have tried all the above techniques (to the best of my knowledge), and received almost no performance change. Whilst I am receiving around 40FPS in my implementation, which is by no means problematic, I am still curious as to where these optimisation 'tips' actually come into use? My CPU is idling around 20-50% during rendering, therefore I assume I am GPU bound for increasing performance. Note: I am looking into gDEBugger at the moment Cross posted at Game Development

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• server performance: multiple external connections and performance

  - by websiteguru

  I am creating a php script that requires the server to make several cURL requests per run. I'll be running this script through cron every 3 minutes. Im looking to maximize the amount of cURL requests I can make in a 24 hr period. What I am wondering is if it would be better from a performance standpoint to get a dedicated server, or several small shared hosting accounts. With the problem being number of external connections and not system resources I'm wondering which is the best approach.

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• javascript object access performance

  - by youdontmeanmuch

  In Javascript, when your getting a property of an object, is there a performance penalty to getting the whole object vs only getting a property of that object? Also Keep in mind I'm not talking about DOM access these are pure simple Javascript objects. For example: Is there some kind of performance difference between the following code: Assumed to be faster but not sure: var length = some.object[key].length; if(length === condition){ // Do something that doesnt need anything inside of some.object[key] } else{ var object = some.object[key]; // Do something that requires stuff inside of some.object[key] } I think this would be slower but not sure if it matters. var object = some.object[key]; if(object.length === condition){ // Do something that doesnt need anything inside of some.object[key] } else{ // Do something that requires stuff inside of some.object[key] }

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• Performance Testing using xUnit framework

  - by Pavlo Neyman

  Hi all, I wonder if it is possible to run performance testing based on xUnit?

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• Android -- Object Creation/Memory Allocation vs. Performance

  - by borg17of20

  Hello all, This is probably an easy one. I have about 20 TextViews/ImageViews in my current project that I access like this: ((TextView)multiLayout.findViewById(R.id.GameBoard_Multi_Answer1_Text)).setText(""); //or ((ImageView)multiLayout.findViewById(R.id.GameBoard_Multi_Answer1_Right)).setVisibility(View.INVISIBLE); My question is this, am I better off, from a performance standpoint, just assigning these object variables? Further, am I losing some performance to the constant "search" process that goes on as a part of the findViewById(...) method? (i.e. Does findsViewById(...) use some sort of hashtable/hashmap for look-ups or does it implement an iterative search over the view hierarchy?) At present, my program never uses more than 2.5MB of RAM, so will assigning 20 or so more object variables drastically affect this? I don't think so, but I figured I'd ask. Thanks.

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• java statistics collection for performance evaluation

  - by user384706

  What is the most efficient way to collect and report performance statistic analysis from an application? If I have an application that uses a series of network apis, and I want to report statistics at runtime, e.g. Method doA() was called 3 times and consumed on avg 500ms Method doB() was called 5 times and consumed on avg 1200ms etc Then, I thought of using a well defined data structure (of collection) that each thread updates per remote call, and this can be used for the report. But I think that it will make the performance worse, for the time spend for statistics collection. Am I correct? How would I procceed if I used a background thread for this, and the other threads that did the remote calls were unaware of this collection gathering? Thanks

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