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  • Reducing template bloat with inheritance

    - by benoitj
    Does anyone have experience reducing template code bloat using inheritance? i hesitate rewriting our containers this way: class vectorBase { public: int size(); void clear(); int m_size; void *m_rawData; //.... }; template< typename T > class vector : public vectorBase { void push_back( const T& ); //... }; I should keep maximum performance while reducing compile time I'm also wondering why stl implementations do not uses this approach Thanks for your feedbacks

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  • Data Warehouse: One Database or many?

    - by drrollins
    At my new company, they keep all data associated with the data warehouse, including import, staging, audit, dimension and fact tables, together in the same physical database. I've been a database developer for a number of years now and this consolidation of function and form seems counter to everything I know. It seems to make security, backup/restore and performance management issues more manually intensive. Is this something that is done in the industry? Are there substantial reasons for doing or not doing it? The platform is Netezza. The size is in terabytes, hundreds of millions of rows. What I'm looking to get from answers to this question is a solid understanding of how right or wrong this path is. From your experience, what are the issues I should be focused on arguing if this is a path that will cause trouble for us down the road. If it is no big deal, then I'd like to know that as well.

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  • ExtJS Grid slow with 3000+ records

    - by Oliver Watkins
    I am using ExtJS Grid and its getting pretty slow with 3000+ records. Sorting takes about 4 seconds. Compared to other more Javascript tables, this is pretty slow. I am thinking maybe to use pagination in my table. However after reading the documentation, I am still a bit unsure about how pagination works in extjs. Does this pull data from the server each time u turn a page? I would prefer that wasn't the case. I would prefer the 3000 records are saved in the browser and then what is rendered is just a portion of those rows. Also I am using Extjs version 4.2.1. If I upgrade to version 5. will I get some performance improvements?

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  • On Memory Allocation and C++

    - by Arpan
    And I quote from MSDN http://msdn.microsoft.com/en-us/library/aa366533(VS.85).aspx: The malloc function has the disadvantage of being run-time dependent. The new operator has the disadvantage of being compiler dependent and language dependent. Now the questions folks: a) What do we mean that malloc is run-time dependent? What kind of dynamic memory allocation functions can be independent of run-time? This statement sounds real strange. b) new is language dependent? Of course it should be right? Are HeapAlloc, LocalAlloc etc language independent? c) From a pure performance perspective are the MSVC provided routines preferable? Arpan

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  • Excel workbooks produced by POI don't work when linked

    - by Eric Nicolas
    Here is what I'm doing : Create a workbook in memory (book = new HSSFWorkbook(), ...) Save it to disk (book.write(...)) Open in Excel (ok) Create another workbook in Excel, which links to the first one (=PoiWorkbook?xls!A1) Close Excel Then everytime I open the second workbook again, all the links are #N/A, unless I also open the POI-generated workbook at the same time. I never saw this behaviour with standard workbooks created in Excel. Anyone has seen this and found a workaround ? Thanks.

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  • Dealing with Windows line-endings in Python

    - by Adam Nelson
    I've got a 700MB XML file coming from a Windows provider. As one might expect, the line endings are '\r\n' (or ^M in vi). What is the most efficient way to deal with this situation aside from getting the supplier to send over '\n' :-) Use os.linesep Use rstrip() (requiring opening the file ... which seems crazy) Using Universal newline support is not standard on my Mac Snow Leopard - so isn't an option. I'm open to anything that requires Python 2.6+ but it needs to work on Snow Leopard and Ubuntu 9.10 with minimal external requirements. I don't mind a small performance penalty but I am looking for the standard best way to deal with this.

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  • how do copyright permission systems for content hosting sites work?

    - by zebraman
    I am wondering about subscription sites that host content, like recorded performances from concerts. I'm sure there is a tangle of copyright permissions that must be granted for these video/audio files to be hosted. For example, if a band plays a cover of another band's song, permission must be obtained from not only the band that performed, but the band that owns the song. Perhaps even from the venue that hosted the performance, to record the video and post the content. I am curious how websites that host content like this work. How might an automated copyright system work to keep track of who has ownership of certain performances and obtain permission from said owners to record and post their content.

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  • Identifying idle state on a windows machine

    - by SaM
    I know about the GetLastInputInfo method but that would only give me the duration since last user input - keyboard or mouse. If a user input was last received 10 minutes ago, that wouldn't mean the system has been idle for 10 minutes - scans, downloads, movies - lots of reasons. So how can we identify whether the system is truly idle or not? Does anyone know what Window's definition of "idle" is? Must be a combination of thresholds - like less than 5% cpu util, less than 3% disk util etc. - along with the user input parameter...anyone knows the exact definition?

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  • write image file larger than 4096

    - by ntan
    Hi, *************EDIT********** i am using ODBC and found that can not read more than 4096 for a field Any suggestions *************EDIT************ i am reading an image from db $image=$row["image-contents"]; Now try to write the file to disk $image_name="test.jpg"; $file = fopen( "images/".$image_name, "w" ); fwrite( $file, $image); fclose( $file ); The problem is that the file created is only 4096 bytes and the image file is corrupt because $image is larger than 4096. I now that fwrite use blocks for write but i dont know how do it. Help plz!

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  • CakePHP repeats same queries

    - by Rytis
    I have a model structure: Category hasMany Product hasMany Stockitem belongsTo Warehouse, Manufacturer. I fetch data with this code, using containable to be able to filter deeper in the associated models: $this->Category->find('all', array( 'conditions' => array('Category.id' => $category_id), 'contain' => array( 'Product' => array( 'Stockitem' => array( 'conditions' => array('Stockitem.warehouse_id' => $warehouse_id), 'Warehouse', 'Manufacturer', ) ) ), ) ); Data structure is returned just fine, however, I get multiple repeating queries like, sometimes hundreds of such queries in a row, based on dataset. SELECT `Warehouse`.`id`, `Warehouse`.`title` FROM `beta_warehouses` AS `Warehouse` WHERE `Warehouse`.`id` = 2 Basically, when building data structure Cake is fetching data from mysql over and over again, for each row. We have datasets of several thousand rows, and I have a feeling that it's going to impact performance. Is it possible to make it cache results and not repeat same queries?

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  • OpenGL and layouts

    - by Hnefi
    I'm using OpenGL to render a game view in my android application. The game is turn based and I wish to add some buttons to the interface. I'd prefer to use standard Android widgets, structured in an XML-generated layout (or, if I have to, a hardcoded layout) and put the OpenGL view in its own window as part of that layout. So in regards to this, I have 3 questions: 1: Is such a thing possible? I've done a few half-hearted tries, but have had no luck so far. 2: Is such a thing advisable? Does it carry a significant performance penalty, for example, over using OpenGL-based homebrew widgetry? 3: Is it possible to pass particular arguments to instances created in XML layouts? For example, my current OpenGL view has three arguments in its constructor; is it somehow possible for me to invoke that particular constructor with particular parameters when it's part of a layout?

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  • Emulating a transaction-safe SEQUENCE in MySQL

    - by Michael Pliskin
    We're using MySQL with InnoDB storage engine and transactions a lot, and we've run into a problem: we need a nice way to emulate Oracle's SEQUENCEs in MySQL. The requirements are: - concurrency support - transaction safety - max performance (meaning minimizing locks and deadlocks) We don't care if some of the values won't be used, i.e. gaps in sequence are ok. There is an easy way to archieve that by creating a separate InnoDB table with a counter, however this means it will take part in transaction and will introduce locks and waiting. I am thinking to try a MyISAM table with manual locks, any other ideas or best practices?

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  • How to transfer large files from desktop to server ( .NET)

    - by rahulchandran
    I am writing a .NET 2.0 based desktop client that will send large files ( well largish under 2GB) to a server. Need to develop the server as well. Server can be on any technology It should be secure so an underlying SSL stream is needed What are my options. Any obvious caveats etc I should be aware of To my mind the simplest solution is to open a tcp\ip connection over SSL to the server and send n packets each of size M bytes and then have the server append the chunks to the file and finally send an EOF packet as well IS this horrible. Will the perf suck on the server with all these disk writes What are any other clever options. I am limited to .NET 2.0 on the client if I did move to a WCF client will it buy be something magical and cool for this scenario Thanks

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  • Does Python Django support custom SQL and denormalized databases with no Foreign Key relationships?

    - by Jay
    I've just started learning Python Django and have a lot of experience building high traffic websites using PHP and MySQL. What worries me so far is Python's overly optimistic approach that you will never need to write custom SQL and that it automatically creates all these Foreign Key relationships in your database. The one thing I've learned in the last few years of building Chess.com is that its impossible to NOT write custom SQL when you're dealing with something like MySQL that frequently needs to be told what indexes it should use (or avoid), and that Foreign Keys are a death sentence. Percona's strongest recommendation was for us to remove all FKs for optimal performance. Is there a way in Django to do this in the models file? create relationships without creating actual DB FKs? Or is there a way to start at the database level, design/create my database, and then have Django reverse engineer the models file?

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  • storing huge amount of records into classic asp cache object is SLOW

    - by aspm
    we have some nasty legacy asp that is performing like a dog and i narrowed it down to because we are trying to store 15K+ records into the application cache object. but that's not the killer. before it stores it, it converts the ADO stream to XML then stores it. this conversion of the huge record set to XML spikes the CPU and causes all kinds of havoc on users when it's happening. and unfortunately we do this XML conversion to read the cache a lot, causing site wide performance problems. i don't have the resources to convert everything to .net. so that's out. but i need to obviously use caching, but int his case the caching is hurting instead of helping. is there a more effecient way to store this data instead of doing this xml conversion to/from every time we read/update the cache?

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  • PostgreSQL: How to index all foreign keys?

    - by biggusjimmus
    I am working with a large PostgreSQL database, and I are trying to tune it to get more performance. Our queries and updates seem to be doing a lot of lookups using foreign keys. What I would like is a relatively simple way to add Indexes to all of our foreign keys without having to go through every table (~140) and doing it manually. In researching this, I've come to find that there is no way to have Postgres do this for you automatically (like MySQL does), but I would be happy to hear otherwise there, too.

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  • When does it make sense to use a map?

    - by kiwicptn
    I am trying to round up cases when it makes sense to use a map (set of key-value entries). So far I have two categories (see below). Assuming more exist, what are they? Please limit each answer to one unique category and put up an example. Property values (like a bean) age -> 30 sex -> male loc -> calgary Presence, with O(1) performance peter -> 1 john -> 1 paul -> 1

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  • Rails: getting logic to run at end of request, regardless of filter chain aborts?

    - by JSW
    Is there a reliable mechanism discussed in rails documentation for calling a function at the end of the request, regardless of filter chain aborts? It's not after filters, because after filters don't get called if any prior filter redirected or rendered. For context, I'm trying to put some structured profiling/reporting information into the app log at the end of every request. This information is collected throughought the request lifetime via instance variables wrapped in custom controller accessors, and dumped at the end in a JSON blob for use by a post-processing script. My end goal is to generate reports about my application's logical query distribution (things that depend on controller logic, not just request URIs and parameters), performance profile (time spent in specific DB queries or blocked on webservices), failure rates (including invalid incoming requests that get rejected by before_filter validation rules), and a slew of other things that cannot really be parsed from the basic information in the application and apache logs. At a higher level, is there a different "rails way" that solves my app profiling goal?

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  • Which is the best API/Library to use when accessing a WebCam in .Net?

    - by Doctor Jones
    Which is the best API to use when accessing a WebCam in .Net? (I know they can be webcam specific, I am willing to buy a new webcam if it means better results). I want to write a desktop application that will take video from a webcam and store it in MPEG4 formats (DivX, Xvid, etc...). I would also like to access bitmap stills from the device so I can do image comparison between frames. I have tried various libraries, and none have really been a great fit (some have performance issues (very inconsistent framerates), some have image quality limitations, some just crash out for seemingly no reason. I want to get high quality video (as high as I can get) and a decent framerate. My webcam is more than up to the job and I was hoping that there would be a nice Managed .Net library around that would help my cause. Are webcam APIs all just incredibly bad?

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  • How to receive HTTP messages using Socket

    - by Poma
    I'm using Socket class for my web client. I can't use HttpWebRequest since it doesn't support socks proxies. So I have to parse headers and handle chunked encoding by myself. The most difficult thing is to determine length of content so I have to read it byte-by-byte. First I have to use ReadByte() to find last header ("\r\n\r\n" combination), then read chunk's size etc. But this approach has very poor performance. Can you suggest better solution? Maybe some open source examples or libraries that handle http request through sockets (not very big and complicated though, I'm a noob)

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  • Php getting too many connections error from MySQL

    - by uzioriluzan
    Hello everyone, I am using MySQL and PHP with 2 application servers and 1 database server. With the increase of the number of users (around 1000 by now), I'm getting the following error : SQLSTATE[08004] [1040] Too many connections The parameter "max_connections" is set to "1000" in my.cnf and "mysql.max_persistent" is set to -1 in php.ini. There are at most 1500 apache processes running at a time since the "MaxClients" apache parameter is equal to 750 and we have 2 application servers. Should I raise the "max_connections" to 1500 as indicated in here? Or should I set "mysql.max_persistent" to 750 (we use PDO with persistent connections for performance reasons since the database server is not the same as the application servers)? Or should I try something else? Thanks in advance!

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  • Can you solve my odd Sharepoint CSS cache / customising problem?

    - by Aidan
    I have a weird situation with my sharepoint css. It is deployed as part of a .wsp solution and up until now everything has been fine. The farm it deploys too has a couple of webfront ends and a single apps server and SQL box. The symptom is that if I deploy the solution, then use a webbrowser to view the page it has no styles, and if I access the .css directly I see the first 100 or so bytes of the .css. However if I go into sharepoint designer and look at the file it is looks fine, and if I check it out and publish it (customising the file but not actually changing anything in it) then the website works fine and the css downloads completely. There is some fairly complex caching on the servers Disk based and object caches. as far as I can tell I have cleared these (and an issreset should clear them anyway... shouldn't it?) I have used this tool to clear the blobcache from the whole farm http://blobcachefarmflush.codeplex.com/

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  • Hit Testing with CALayer using the alpha properties of the CALayer contents.

    - by Charliehorse
    I'm writing a game for Mac using Cocoa. I'm currently implementing hit testing and have founds that CALayer offers hit testing, but does not seem to implement the alpha properties. As I have at times many CALayers stacked on top of each other, I really need to find a way to determine what the user actually meant to click on. I'm thinking if I could somehow get an array that contains pointers to all of the CALayers that contain the click point, I could filter through them some how. However the only way I've got so far to create the array is: NSMutableArray* anArrayOfLayers = [NSMutableArray array]; for (CALayer* aLayer in mapLayer.sublayers) { if ([aLayer containsPoint:mouseCoord]) [anArrayOfLayers addObject:aLayer]; } Then sort the array by the CALayer's z-values then go through checking if the pixel at location is alpha or not. However, between the sort and the alpha check this seems to be an incredible performance hog. (How would you even check the alpha?) Is there any way to do this?

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  • ImageView source scaling done right. How?

    - by Aleksey Malevaniy
    Scope Image bitmap have to be shown as imageView.setImageBitmap(bitmap) and scaled to fit UI. This could be done via: bitmap = Bitmap.createScaledBitmap(bitmap, newWidth, newHeight, true); xml's ImageView attributes such as android:layout_width="newWidth" android:layout_height="newHeight" android:adjustViewBounds="true" android:scaleType="fitCenter" Problem Which way is better for performance? I prefer xml 'cause this is UI specific problem and I prefer to use xmls for UI definition. Also we set width/height values in dp, it means we have the same UI for different screens. Thanks!

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  • [Symfony] Admin generator and i18n

    - by David
    I have read lots of questions about i18n, but I haven't found any about performance. I have a simple backend app listing the contents of an ads table. These ads have a category, that is translated in some languages (it's defined as i18n in the Doctrine schema). So, when I add a "table_method" in my generator.yml to include de Category table, it reduces the number of queries, but there are yet some of them referencing i18n translation tables. So, if I add the category Translation table to the query, it reduces even more the queries BUT it increases the processing time considerably. Why this time penalty? Just because of the translation table? And why isn't the filter using this method to avoid so many translation queries as well? I mean, if I want to filter by category, it is making one query per category to include the translation table. Why??

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