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  • C Programming: malloc and free within a loop

    - by kouei
    Hi all, I just started out with C and have very little knowledge about performance issues with malloc() and free(). My question is as such: if I were to call malloc() followed by free() in a while-loop that loops for, say, 20 times, would it run slower compared to if I were to call free() outside the loop? I am actually using the first method to allocate memory to a buffer, read a string of variable length in a file, perform some string operation, and then clear the buffer after every iteration. If my method results in a lot of overhead then I'd like to ask for a better way for me to achieve the same results. Sorry for my bad English. Thanks and regards, K

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  • how to automate upsizing from Access to SQL Server?

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

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  • Version Control for developers new to source control

    - by Daisetsu
    I've been writing code for a few years now and our backup strategy has been to zip the entire code directory up every few days and put it somewhere else on your hard drive, or occasionally upload it to some online file hosting service. Unfortunately the file hosting service got canceled without telling me and we lost years of backups. It's come down to the point where I finally have to learn to use version control. The only problems are My boss really doesn't like SVN, he tried it and it had a high learning curve (at least his client). We need a reliable place to host it (we can pay a reasonable amount). Can someone suggest what may be the best version control system and client for a newbie which won't be too annoying. Second what is a good remote version control service?

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  • How to avoid this very heavy query that slows down the application?

    - by Juan Paredes
    Hi, We have a web application running in a production enviroment and at some point the client complained about how slow the application got. When we checked what was going on with the application and the database we discover this "precious" query that was being executed by several users at the same time (thus inflicting an extremely high load on the database server): SELECT NULL AS table_cat, o.owner AS table_schem, o.object_name AS table_name, o.object_type AS table_type, NULL AS remarks FROM all_objects o WHERE o.owner LIKE :1 ESCAPE :"SYS_B_0" AND o.object_name LIKE :2 ESCAPE :"SYS_B_1" AND o.object_type IN(:"SYS_B_2", :"SYS_B_3") ORDER BY table_type, table_schem, table_name Our application does not execute this query, I believe it is an Hibernate internal query. I've found little information on why Hibernate does this extremely heavy query, so any help in how to avoid it very much appreciated! The production enviroment information: Red Hat Enterprise Linux 5.3 (Tikanga), JDK 1.5, web container OC4J (whitin Oracle Application Server), Oracle Database 10.1.0.4, JDBC Driver for JDK 1.2 and 1.3, Hibernate version 3.2.6.ga, connection pool library C3P0 version 0.9.1. Thank you.

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  • Compiler optimization of repeated accessor calls

    - by apocalypse9
    I've found recently that for some types of financial calculations that the following pattern is much easier to follow and test especially in situations where we may need to get numbers from various stages of the computation. public class nonsensical_calculator { ... double _rate; int _term; int _days; double monthlyRate { get { return _rate / 12; }} public double days { get { return (1 - i); }} double ar { get { return (1+ days) /(monthlyRate * days) double bleh { get { return Math.Pow(ar - days, _term) public double raar { get { return bleh * ar/2 * ar / days; }} .... } Obviously this often results in multiple calls to the same accessor within a given formula. I was curious as to whether or not the compiler is smart enough to optimize away these repeated calls with no intervening change in state, or whether this style is causing a decent performance hit. Further reading suggestions are always appreciated

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  • May a NSManagedObjectContext re-fault objects automatically?

    - by frenetisch applaudierend
    I am trying to create an application which allows background threads to update core data objects while the user might be reading the same data. My approach to this would be to use multiple NSManagedObjectContexts and then before a background thread does a -save: operation, I fetch the object the user is currently working on and fire the fault for all its properties and relationships recursively. This way I have all objects the user could act with in my NSManagedObjectContext without seeing the already updated values. But this can only work if the NSManagedObjectContext cannot decide himself that e.g. memory usage is too high, and starts faulting objects which I do not explicitly reference (other than through the NSManagedObject relationship). So the question is, can the NSManagedObjectContext decide that an object needs to be re-faulted, without intervention from my side? Thanks for your effort, Markus

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  • 640 enterprise library caching threads - how?

    - by JohnW
    We have an application that is undergoing performance testing. Today, I decided to take a dump of w3wp & load it in windbg to see what is going on underneath the covers. Imagine my surprise when I ran !threads and saw that there are 640 background threads, almost all of which seem to say the following: OS Thread Id: 0x1c38 (651) Child-SP RetAddr Call Site 0000000023a9d290 000007ff002320e2 Microsoft.Practices.EnterpriseLibrary.Caching.ProducerConsumerQueue.WaitUntilInterrupted() 0000000023a9d2d0 000007ff00231f7e Microsoft.Practices.EnterpriseLibrary.Caching.ProducerConsumerQueue.Dequeue() 0000000023a9d330 000007fef727c978 Microsoft.Practices.EnterpriseLibrary.Caching.BackgroundScheduler.QueueReader() 0000000023a9d380 000007fef9001552 System.Threading.ExecutionContext.runTryCode(System.Object) 0000000023a9dc30 000007fef72f95fd System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) 0000000023a9dc80 000007fef9001552 System.Threading.ThreadHelper.ThreadStart() If i had to give a guess, I'm thinkign that one of these threads are getting spawned for each run of our app - we have 2 app servers, 20 concurrent users, and ran the test approximately 30 times...it's in the neighborhood. Is this 'expected behavior', or perhaps have we implemented something improperly? The test ran hours ago, so i would have expected any timeouts to have occurred already.

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  • grouping draggable objects with jquery-ui draggable

    - by Jim Robert
    Hello, I want to use jquery draggable/droppable to let the user select a group of objects (each one has a checkbox in the corner) and then drag all the selected objects as a group... I can't figure out for the life of me how to do it haha. Here is what I'm thinking will lead to a usable solution, on each draggable object, use the start() event and somehow grab all the other selected objects and add them to the selection I was also considering just making the dragged object look like a group of objects (they're images, so a pile of photos maybe) for performance reasons. I think using the draggable functionality might fall over if you drag several dozen objects at once, does that sound like a better idea?

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  • How can a Delphi TForm / TPersistent object calculate its own construction and deserialization time?

    - by mjustin
    For performance tests I need a way to measure the time needed for a form to load its definition from the DFM. All existing forms inherit a custom form class. To capture the current time, this base class needs overriden methods as "extension points": start of the deserialization process after the deserialization (can be implemented by overriding the Loaded procedure) the moment just before the execution of the OnFormCreate event So the log for TMyForm.Create(nil) could look like: - 00.000 instance created - 00.010 before deserialization - 01.823 after deserialization - 02.340 before OnFormCreate Which TObject (or TComponent) methods are best suited? Maybe there are other extension points in the form creation process, please feel free to make suggestions. Background: for some of our app forms which have a very basic structure (with some PageControls and QuantumGrids) I realized that it is not database access and other stuff in OnFormShow but the construction which took most of the time (around 2 seconds) which makes me wonder where this time is spent. As a reference object I will also build a mock form which has a similar structure but no code or datamodule connections and measure its creation time.

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  • PHP voting system with sessions?

    - by pingu
    Hi guys, I've been reading up on stackoverflow about creating voting systems in PHP that minimize abuse/multiple voting from the same user, but I haven't come across the answer to my question. I've got an application where users don't need to register to vote or "like" an entry. Obviously, I want to minimize abuse and I don't want to limit votes per IP address because some organisations (mine included) use shared IP addresses. I've never used sessions in a non-authenticated system before, but since this application is centered around entry votes I was wondering if this approach would work and whether there were any disadvantages such as performance implications, and whether it's even possible to use sessions in this way: start a session when the website is loaded allow one vote per item per session If this is a bad idea, my alternative options would be to allow a reasonable number of votes per IP address (say 25), or put a time limit between votes from the same IP address. What do you guys recommend?

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  • reasons to not use typekit?

    - by Haroldo
    I'm launching a new site soon and would like to use one nice font (for headings etc). I've experimented with scripts like cufon and find them very disappointing. The way I see it I have to legal options: create my own font stacks using fonts that are licensed for @font-face (like fontsquirrel) subscribe to typekit use standard font stacks including some of MS Office's nicer fonts (not keen on!) I'm looking for comments from someone with experience here, not speculation please (i can do that myself!). Has anyone used typekit? Have you noticed any performance issues?

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  • DefaultSchedulerService in ASP.NET application

    - by Samir P
    Hi, My project has a requirement to implement look-ahead caching i.e. triggering another request on invokation of a specific request. The following details in short the implementation - HttpModule parses the SOAPRequest and matches entry in a configuration file for look-ahead candidate. If the request matches, it prepares the Parameters dictionary and starts appropriate workflow. Single workflow runtime is used across all requests is ensured through initializing the runtime instance at Application_Start event and stored in Application Dictionary. Using persistence service and DefaultScheduler service. We can't implement windows service model, as current requirement mandates passing the SOAPRequest parameters as arguments. ManualSchedulerService is not in contention due to synchronous nature of it's actual behaviour. Still the performance is pretty bad and product team is not happy. Can anybody suggest me better solution? Thanks, Samir

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  • Persist an object that is not marked as serializable

    - by lasseeskildsen
    Hi, I need to persist an object that is not marked with the serializable attribute. The object is from a 3rd party library which I cannot change. I need to store it in a persist place, like for example the file system, so the optimal solution would be to serialize the object to a file, but since it isn't marked as serializable, that is not a straight forward solution. It's a pretty complex object, which also holds a collection of other objects. Do you guys have any input on how to solve this? The code will never run in a production environment, so I'm ok with almost any solution and performance.

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  • Good Economics book for developers

    - by Rocket Surgeon
    Joel mentions in several of his blog posts that it is very important for a developer/software entrepreneur to have solid understanding of Economics. Yet the Fog Creek MBA book reading list does not include any Economics books. Is there any good material that people can recommend? Obviously, I am not as concerned about mathematical treatise as foundations and basic principles. For example, I was able to find a very good high-level read on Macroeconomics: Concise Guide to Macroeconomics but I am yet to find anything similar on Microeconomics. Any suggestions and reading pointers would be highly appreciated.

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  • Hiding flash component scrollbars using object/param syntax

    - by Kieran Benton
    Hi all, I'm not sure if this is possible (complete non-flash developer speaking), but we have a 3rd party component that we want to only show a certain topleft hand portion of. I've tried limiting the size of the HTML object container as: <object type="application/x-shockwave-flash" width="600" height="415" data="<url>"> <param name="movie" value="<url>" /> <param name="wmode" value="transparent" /> <param name="allowscriptaccess" value="always" /> <param name="quality" value="high" /> <param name="flashvars" value="<vars>" /> </object> So limiting it to 600x415, but this causes horizontal and vertical scrollbars as part of the flash component to appear. Is there any standard way to override this behaviour? Thanks.

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  • Perfmon on Vista to monitor .Net CLR memory for dutch dummies

    - by Dabblernl
    OK... My managed .Net program is eating memory leading it to crash after a few hours with a OutOfMemoryException. I want to investigate this starting with using perfmon.exe. I found a description on how to do this here However, I have a dutch Vista and the terms used differ widely from the ones used in this blog and I find myself simply unable to set it up. Can someone point me the way by stating "first from the top,second from the left" how to set up a performance monitor for my .Net program?

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  • How to recognize touch events and control a script object inside UIWebView?

    - by Markus S.
    Situation: I have an UIView with an UIWebView in it. When the viewDidLoad the Javascript Object inside the UIWebView is called (Microsoft Seadragon AJAX JS). For your Understanding: Seadragon loads a specified megapixel image(JPEG) and in a Desktop Browser like Firefox i can Zoom into the image and I can drag the crop for example from the middle to the left. In the iPhone Simulator (for iPad) only the Zooming Function is working on one single tap but when i try to drag the crop (with left mouse button click and holding it) I'm dragging the whole UIWebView but not the crop of course! Is that feature which the simulator isn't able to handle or what's yout solutin guys? Special Thanks!! P.S.: It's a bit jiggling when the zooming function of Seadragon is called. Is that authentic to the real performance of the iPad or does the simulator not have the power as the iPad has?

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  • Filtering in E4X

    - by FB55
    This is just a simple question. I'm currently using Mozilla's Rhino to develop a little webapp. As one step, I need to get a webpage and filter all of it's nodes. For doing that, I use E4X. I thought I could do this like that: var pnodes = doc..*(p); But that produces an error. How is it done right? (BTW: this is just a step for increasing performance. The code already does well, it's just a bit slow.)

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  • Low Power Speed Monitoring

    - by user555584
    I am aware of speed detection via gps, however as a background app, I am concerned about high power drain. I am looking to detect speed, say over 5mph, but it does not have to be accurate, say like a speedometer. Is there a low power way to detect if the phone is in motion, say by triangulation, or tracking tower strength and new/recently lost towers? I have an app design that is dependent on running in the background upon launch and knowing if the phone is in a car or not. Thanks!

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  • Django - categories & sub-categories

    - by Bluey
    Some advice needed on how I can structure my models for my site. I have seen this post from Django project but still a little lost. Also come across Django-MPTT - but that's no help and possibly overkill. I'm looking to have categories & subcategories that are shown in the URLs like this: mysite.com/Level1/Maths/Calculations/Addition/ mysite.com/Level3/English/ mysite.com/Level2/English/Storytelling/ In my admin interface I'm looking to have drop downs for each level of category or subcategory. Also at each level I will be querying items (another model) like get all items that have the category 'Level1' AND 'Maths'. There could also be a situation where I have five or more subcategories. How is it best to create my models for best performance? It it worth using tagging instead?

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  • Why does my 64-bit IIS app pool show 3 gigabytes more virtual memory than private memory?

    - by Brett
    I have an ASP.Net application that I am running on 64-bit IIS 6 on Windows XP x64. When I open performance counters after one page hit of a trivial page, I see a Private Bytes of about 88 megs, but a Virtual Bytes of about 3 Gigs. When I try the same thing with a VERY trivial ASP.Net app, I get the same result. We see something similar on Windows Server 2003 in production -- there it is an issue because we recycle when the virtual memory consumed outgrows a limit. Before we make any changes to our recycling settings, we'd like to answer the following questions: Why does the app pool grab such a large hunk of virtual memory? Is the amount of virtual memory headroom the app requests configurable? Thanks! Brett

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  • Spinlocks, How Much Useful Are They?

    - by unknown
    How often do you find yourself actually using spinlocks in your code? How common is it to come across a situation where using a busy loop actually outperforms the usage of locks? Personally, when I write some sort of code that requires thread safety, I tend to benchmark it with different synchronization primitives, and as far as it goes, it seems like using locks gives better performance than using spinlocks. No matter for how little time I actually hold the lock, the amount of contention I receive when using spinlocks is far greater than the amount I get from using locks (of course, I run my tests on a multiprocessor machine). I realize that it's more likely to come across a spinlock in "low-level" code, but I'm interested to know whether you find it useful in even a more high-level kind of programming?

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  • iPhone - Is it ok to override UITableViewCell setSelected:animated

    - by Brian
    I am drawing custom UITableViewCells. My cells are opaque and are completely drawn in the drawRect of the cell to help with performance. I want to handle the look of a selected cell myself. If I don't, then the contents of my cell is covered up by the selectedBackgroundView that is added. Is it common or acceptable to override the setSelected:animated method of my cell so this is done properly. I guess if I did that, then I would not call the super's setSelected method since I would be handling how the cell will show that its selected. I would also have to set the selected property of the cell. Any help would be great. Thanks.

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  • A Simple PHP Array Manipulation

    - by Ygam
    Hi guys! how would you turn this array: array( 0 => Title1, 1 => Title2, 3 => Address1, 4 => Address2, ) to this array: array ( 0 => array( 'title' => 'Title1' 'address' =>'Address1' ), 1 => array( 'title' => 'Title2', 'address' => 'Address2' ) ); when you were initially given $_POST['title'] = array('Title1', 'Title2); $_POST['address'] = array('Address1', 'Address2'); which when merged would give you the first array I have given I was able to solve this via a high level Arr:Rotate function in Kohana framework, along with Arr::merge function but I can't quite understand the implementation. Please help

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  • Tomcat6 MySql JDBC Datasource configuration

    - by Bob
    Hi, I've always used Spring's dependency injection to get datasource objects and use them in my DAOs, but now, I have to write an app without that. With Spring I can write something like this: <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> <property name="driverClassName" value="com.mysql.jdbc.Driver" /> <property name="url" value="jdbc:mysql://127.0.0.1/app?characterEncoding=UTF-8" /> <property name="username" value="u" /> <property name="password" value="p" /> </bean> But how can I use datasource in my DAOs without Spring or anything? I'm using servlets and JSPs only. Performance is very important factor. Thanks in advance!

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