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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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• Streaming multiple TObjects to a TMemoryStream

  - by Altar

  I need to store multiple objects (most of them are TObject/non persistent) to a TMemoryStream, save the stream to disk and load it back. The objects need to be streamed one after each other. Some kind of universal container. I started to make several functions that store stuff to stream - for example function StreamReadString(CONST MemStream: TMemoryStream): string; StreamWriteString(CONST MemStream: TMemoryStream; s: string); However, it seems that I need to rewrite a lot of code. One of the many examples is TStringList.LoadFromStream that will not work so it needs to be rewritten. This is because TStringList needs to be the last object in the stream (it reads from current position to the end of the stream). Anybody knows a library that provide basic functionality like this? I am using Delphi 7 so RTTI won't help too much.

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• Will .NET 4.0 apps work on Win 2008 R2 Server Core?

  - by markus

  When Windows Server 2008 R2 was launched, the "server core" edition started to become useful to me, because it lets me deploy .NET background applications isolated on their own virtual machine instance with only a small fraction of all the disk space overhead of a default Windows Server installation, and very few Windows Updates. It comes with a subset of .NET 3.5 SP1 integrated (as an optional feature). Now that .NET 4.0 is released, the redistributables explicitly state that it's not support on Server Core. Any chance that there will be a separate download available for Server Core (e. g. without WPF) any time soon, has anybody heard about it?

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• Managing Data Prefetching and Dependencies with .NET Typed Datasets

  - by Derek Morrison

  I'm using .NET typed datasets on a project, and I often get into situations where I prefetch data from several tables into a dataset and then pass that dataset to several methods for processing. It seems cleaner to let each method decide exactly which data it needs and then load the data itself. However, several of the methods work with the same data, and I want the performance benefit of loading data in the beginning only once. My problem is that I don't know of a good way or pattern to use for managing dependencies (I want to be sure I load all the data that I'm going to need for each class/method that will use the dataset). Currently, I just end up looking through the code for the various classes that will use the dataset to make sure I'm loading everything appropriately. What are good approaches or patterns to use in this situation? Am I doing something fundamentally wrong? Although I'm using typed datasets, this seems like it would be a common situation where prefetching data is used. Thanks!

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• Java data structure to use with Hibernate to store unknown number of parameters?

  - by Lunikon

  Following problem: I want to render a news stream of short messages based on localized texts. In various places of these messages I have to insert parameters to "customize" them. I guess you know what I mean ;) My question probably falls into the "Which is the best style to do it?" category: How would you store these parameters (they may be Strings and Numbers that need to be formatted according to Locale) in the database? I'm using Hibernate to do the ORM and I can think of the following solutions: build a combined String and save it as such (ugly and hard to maintain I think) do some kind of fancy normalization and and make every parameter a single row on the database (clean I guess, but a performance nightmare) Put the params into an Array, Map or other Java data structure and save it in binary format (probably causes a lot of overhead size-wise) I tend towards option #3 but I'm afraid that it might be to costly in terms of size in the database. What do you think?

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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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• 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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• 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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• Storing Instances of Classes in Flex Shared Objects

  - by babyangel86

  Is it possible to store instances of a class in a cookie or in shared objects. Basically in my application I have an object "Diagram" that the user can create. If they hit save, I want to store the current instance as a cookie and allows them to reload it later. Alternatively, I could see about getting them to store the saved version on the hard disk. But even then, all I want to save and retreive is my actionscript object. Is this possible? I've tried storing the object to SharedObject.data.diag, but when I try to retrieve the object from the cookie doing SharedObject.data.diag as Diag returns null.

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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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• Running multiple jvms for different applications in same machine

  - by Rajesh

  We are getting frequent out of memory errors in our dev. machines We are running webshpere, eclipse, soap UI and maven in it. Our server gets down due to this "out of memory errors" when we restart our applications in websphere 2/3 times, We already increased the virtual memory setting in wesphere to 1GB. So what i did was copied the jre we use in eclipse and maven folders so that each of these uses individual jvms. But the performance of websphere is same. 2/3 restarts and out of memory errors. Is there any may of making eclipse and maven use different jvms other than websphere's?

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• Available options for hosting FTP server in .NET application

  - by duane

  I need to implement an FTP service inside my .NET application (running as a Windows Service) and have not had much luck finding good/current source code or vendors. Ideally it needs to be able to respond to the basic FTP Protocol and accept the data stream from an upload via a stream, enabling me to process the data as it is being received (think on the fly hashing). I need to be able to integrate it into my service because it will stack on top of our current code base with an existing custom TCP/IP communication protocol. I don't want to write (and then spend time debugging and performance testing) my own protocol, or implementation. I have already found plenty of ftp client implementations, I just need an acceptable server solution.

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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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• Determine if a decimal can be stored as int32

  - by anchandra

  I am doing some custom serializing, and in order to save some space, i want to serialize the decimals as int, if possible value wise. Performance is a concern, since i am dealing with a high volume of data. The current method i use is: if ((value > Int32.MinValue) && (value < Int32.MaxValue) && ((valueAsInt = Decimal.ToInt32(value)) == value)) { return true; } Can this be improved?

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• Is there an additional runtime cost for using named parameters?

  - by Jurily

  Consider the following struct: public struct vip { string email; string name; int category; public vip(string email, int category, string name = "") { this.email = email; this.name = name; this.category = category; } } Is there a performance difference between the following two calls? var e = new vip(email: "foo", name: "bar", category: 32); var e = new vip("foo", 32, "bar"); Is there a difference if there are no optional parameters defined?

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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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• Keeping track of dirty blocks on a block device

  - by mikeY

  I'm looking for a way to keep track of what blocks on a block device are modified after a point in time. How I eventually want to use this for is to keep two 2TB disks in sync, one which only comes online (connected through USB) once a month. Without knowing what blocks have been modified, I have to go through the whole 2TB every time. I'm using a recent GNU/Linux OS and have C and Python experience. I'm hoping to avoid writing kernel level code as I don't have any experience in that area whatsoever. My current theory is that there should be some hooks somewhere where my code can get called when a disk flush is performed. Any ideas?

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• Using the windows api and C++, how could I load an exe from the hard drive and run it in its own thread?

  - by returneax

  For the sake of learning I'm trying to do what the OS does when launching a program ie. parsing a PE file and giving it a thread of execution. If I have two exe's one called foo.exe and the other bar.exe, how could I have foo.exe load the contents of bar.exe into memory then have it execute from there in its own thread? I know how to get it into memory using MapViewOfFile or by simple loading the contents on the hard drive into a buffer. I'm assuming simply copying the contents of bar.exe on disk into its own suspended thread and running it wouldn't work. I am semi-familiar with PE file internals. All help is very much appreciated, of course :)

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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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• 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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• 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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• Conceptually, how does replay work in a game?

  - by SnOrfus

  I was kind of curious as to how replay might be implemented in a game. Initially, I thought that there would be just a command list of every player/ai action that was taken in the game, and it then 're-plays' the game and lets the engine render as usual. However, I have looked at replays in FPS/RTS games, and upon careful inspection even things like the particles and graphical/audible glitches are consistent (and those glitches are generally *in*consistent). So How does this happen. In fixed camera angle games I though it might just write every frame of the whole scene to a stream that gets stored and then just replays the stream back, but that doesn't seem like enough for games that allow you to pause and move the camera around. You'd have to store the locations of everything in the scene at all points in time (No?). So for things like particles, that's a lot of data to push which seems like a significant draw on the game's performance whilst playing.

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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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• 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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• 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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