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  • How do I import large sql file to local LAMP (xampp) environment

    - by mraslton
    I have used Linux to import a large mysql dump file (into a new database), but am new to how the process works in a local LAMP environment using xampp, as xampp does not support SSH. I've dowloaded the large_dump_file.sql from the Linux server to my local system. I'm using Windows XP and have used xampp to setup LAMP. I am able to access the local_database via phpMyAdmin, but the dump file is too large to import using that app. I'm trying to import the file via the command prompt, but so far with no success. At the prompt: cd .. cd .. cd xampp cd mysql cd bin I've found that mysqlimport is used to import .csv and .txt files, and mysql is used to import .sql files, but can't find documentation as to whether or not to use the -u -p options so I've tried many variations of the command with no luck. What would be the proper command? I've modified the hosts, virtual-hosts conf, and apache config files. Do I need to change any other config files on my local system? Thanks.

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  • Error importing large MySQL dump file which includes binary BLOBs in Windows

    - by Daniel Magliola
    I'm trying to import a MySQL dump file, which I got from my hosting company, into my Windows dev machine, and i'm running into problems. I'm importing this from the command line, and i'm getting a very weird error: ERROR 2005 (HY000) at line 3118: Unknown MySQL server host '+?*á±dÆ-N+Æ·h^ye"p-i+ Z+-$?P+Y.8+|?+l8/l¦¦î7æ¦X¦XE.ºG[ ;-ï?éµ?º+¦¦].?+f9d릦'+ÿG?-0à¡úè?-?ù??¥'+NÑ' (11004) I'm attaching the screenshot because i'm assuming the binary data will get lost... I'm not exactly sure what the problem is, but two potential issues are the size of the file (2 Gb) which is not insanely large, but it's not trivially small either, and the other is the fact that many of these tables have JPG images in them (which is why the file is 2Gb large, for the most part). Also, the dump was taken in a Linux machine and I'm importing this into Windows, not sure if that could add to the problems (I understand it shouldn't) Now, that binary garbage is why I think the images in the file might be a problem, but i've been able to import similar dumps from the same hosting company in the past, so i'm not sure what might be the issue. Also, trying to look into this file (and line 3118 in particular) is kind of impossible given its size (i'm not really handy with Linux command line tools like grep, sed, etc). The file might be corrupted, but i'm not exactly sure how to check it. What I downloaded was a .gz file, which I "tested" with WinRar and it says it looks OK (i'm assuming gz has some kind of CRC). If you can think of a better way to test it, I'd love to try that. Any ideas what could be going on / how to get past this error? I'm not very attached to the data in particular, since I just want this as a copy for dev, so if I have to lose a few records, i'm fine with that, as long as the schema remains perfectly sound. Thanks! Daniel

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  • How to configure a large mtu (linux)

    - by Somejan
    I have a gigabit ethernet connection from my laptop to my router, and a working ipv6 connection to the internet. I can receive very large packets from sites on the internet, with sizes up to at least 10000 bytes (according to wireshark). (edit: turns out to be linux's 'generic receive offload') However, when trying to send anything, my local computer fragments at just below 1500 bytes for ipv6. (On ipv4, I can send tcp packets to the internet of at least 1514 bytes, I can ping with packets up to the configured mtu of 6128 but they are blackholed.) I'm on ubuntu 12.04. I have configured an mtu for my eth0 of 6128 (the maximum it accepts), both using ip link set dev eth0 mtu 6128 and in the NetworkManager applet gui, and restarted the connection. ip link show eth0 shows the 6128 mtu is indeed set. ip -6 route shows that none of the paths the kernel knows about have an mtu set. I can ping over ipv4 with packets up to 6128 bytes (though I don't get responses), but when I do ping6 myrouter -c3 -s1500 -Mdo I get error replies from my own computer saying that the packets are too large and the mtu is 1480. I have confirmed with Wireshark that nothing is put on the wire, and the replies are indeed generated by my own computer. So, how do I get my computer to use the larger mtu?

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  • Export-Mailbox - fails with large folders

    - by grojo
    I am trying to move messages from a rather large mailbox to an archive mailbox. However I run into errors all the time. the command I am executing is Export-Mailbox -Identity MAILBOX_FROM -TargetMailbox ARCHIVE -TargetFolder ARCHIVE_FOLDER -StartDate 2009-02-01 -EndDate 2009-02-28 -DeleteContent -Confirm:$false I can copy/move some messages, but run into frequent "an unknown error has occurred" (statuscode -1056749164) I run the console as administrative user, and all permissions are set right, as far as I can tell. I've restricted the start and end dates in case the number of messages moved/deleted should create problems. Anything I am missing in my setup? Corrupted messages? Over-limit message sizes? Update: What I've learnt so far, is that folder with more than approx 3000 messages will generate errors. If mail retention is set (default 30 days), Export-Mailbox will scan all messages whether these were deleted in previous runs or not, and date restriction to limit number of messages will not work. To avoid errors, I've switched off deleted message retention for the mailbox, and moved the messages from one large folder to multiple folders, and moved these one by one...

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  • Large, high performance object or key/value store for HTTP serving on Linux

    - by Tommy
    I have a service that serves images to end users at a very high rate using plain HTTP. The images vary between 4 and 64kbytes, and there are 1.300.000.000 of them in total. The dataset is about 30TiB in size and changes (new objects, updates, deletes) make out less than 1% of the requests. The number of requests pr. second vary from 240 to 9000 and is dispersed pretty much all over, with few objects being especially "hot". As of now, these images are files on a ext3 filesystem distributed read only across a large amount of mid range servers. This poses several problems: Using a fileysystem is very inefficient since the metadata size is large, the inode/dentry cache is volatile on linux and some daemons tend to stat()/readdir() it's way through the directory structure, which in my case becomes very expensive. Updating the dataset is very time consuming and requires remounting between set A and B. The only reasonable handling is operating on the block device for backup, copying, etc. What I would like is a deamon that: speaks HTTP (get, put, delete and perhaps update) stores data it in an efficient structure. The index should remain in memory, and considering the amount of objects, the overhead must be small. The software should be able to handle massive connections with slow (if any) time needed to ramp up. Index should be read in memory at startup. Statistics would be nice, but not mandatory. I have experimented a bit with riak, redis, mongodb, kyoto and varnish with persistent storage, but I haven't had the chance to dig in really deep yet.

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  • File corruption (bad checksums) in large files copied to VMware guest

    - by AllanA
    In setting up a development lab, I've got a desktop system running ESXi 4.1.0 (free license) on SATA RAID 0 (already purchased and configured when I started this job; I'm open to hardware input as it pertains to my problem.) Its guests so far include two Win2008 Server R2 64-bit VMs and on Ubuntu 10.04 64-bit VM. I'm installing onto the Windows servers. We've been copying off some fairly large files (over a gigabyte) for an installation, hoping to install more quickly from a (virtual) hard drive than from the network for from BD-ROM. The problem is that they keep coming up with different checksums from the originals. The file sizes are the same, but md5sum reports different numbers (and so does the installer, as it refuses to continue when the checksums don't match.) I've tried copying directly from the BD-ROM (attaching the OS drive to the host system's physical drive). I've tried copying the large files onto a co-worker's Windows machine from his Blu-Ray drive; when I do that, the checksums match. But when I copy from his machine to the VM guest over a network share, the checksums no longer match. Thinking this meant a corrupt destination drive, I deleted it in vSphere and added another freshly created drive. The problem persists. I'm not sure what to try next.

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  • Copy past speed very slow for a large number of files on Windows [closed]

    - by Arno2501
    I've run the following test I've created a folder containing 15'000 files of 400 bytes using this batch : @ECHO off SET times=15000 FOR /L %%i IN (1,1,%times%) DO ( fsutil file createnew filename%%i.txt 400 ) then I copy past it on my Windows Computer using this command : robocopy LargeNumberOfFiles\ LargeNumberOfFiles2\ After it has completed I can see that the transfer rate was 915810 Bytes/sec this is less than 1 MB/s. It took me several seconds to copy 7 MBytes Please note that this is very slow. I've tried the same with a folder with a single file of 50 Mbytes and the transfer rate is 1219512195 Bytes/sec. (yeah GB/s) instantaneous. Why copying large number of files take so much time - ressources on a windows filesystem ? Please note that I've tried to do the same on a linux system which runs on the same computer in a virtual machine (vmware player) with ext3 filesystem. I use the cp command and the copy is instantaneous ! Please also note the following : no antivirus I've tested that behaviour on multiple windows computers (always ntfs) i always get comparable results (transfer rate under 1MB/s avg 7-8 seconds to copy 7 MBytes) I've tested on multiple linux ext3 system the copy is always instantaneous for that amount (15000 files of 400 bytes) The question is about understanding what makes windows filesystem so slow to copy large number of files compared to a linux one for instance.

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  • Can I switch the Visual C++ runtime to another heap?

    - by sharptooth
    My program uses a third party dynamic link library that has huge memory leaks inside. Both my program and the library are Visual C++ native code. Both link to the Visual C++ runtime dynamically. I'd like to force the library into another heap so that all allocations that are done through the Visual C++ runtime while the library code is running are done on that heap. I can call HeapCreate() and later HeapDestroy(). If I somehow ensure that all allocations are done in the new heap I don't care of the leaks anymore - they all go when I destroy the second heap. Is it possible to force the Visual C++ runtime to make all allocations on a specified heap?

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  • Handling null values and missing object properties in Silverlight 4

    - by PeterTweed
    Before Silverlight 4 to bind a data object to the UI and display a message associated with either a null value or if the binding path was wrong, you would need to write a Converter.  In Silverlight 4 we find the addition of the markup extensions TargetNullValue and FallbackValue that allows us to display a value when a null value is found in the bound to property and display a value when the property being bound to is not found. This post will show you how to use both markup extensions. Steps: 1. Create a new Silverlight 4 application 2. In the body of the MainPage.xaml.cs file replace the MainPage class with the following code:     public partial class MainPage : UserControl     {         public MainPage()         {             InitializeComponent();             this.Loaded += new RoutedEventHandler(MainPage_Loaded);         }           void MainPage_Loaded(object sender, RoutedEventArgs e)         {             person p = new person() { NameValue = "Peter Tweed" };             this.DataContext = p;         }     }       public class person     {         public string NameValue { get; set; }         public string TitleValue { get; set; }     } This code defines a class called person with two properties.  A new instance of the class is created, only defining the value for one of the properties and bound to the DataContext of the page. 3.  In the MainPage.xaml file copy the following XAML into the LayoutRoot grid:         <Grid.RowDefinitions>             <RowDefinition Height="60*" />             <RowDefinition Height="28*" />             <RowDefinition Height="28*" />             <RowDefinition Height="30*" />             <RowDefinition Height="154*" />         </Grid.RowDefinitions>         <Grid.ColumnDefinitions>             <ColumnDefinition Width="86*" />             <ColumnDefinition Width="314*" />         </Grid.ColumnDefinitions>         <TextBlock Grid.Row="1" Height="23" HorizontalAlignment="Left" Margin="32,0,0,0" Name="textBlock1" Text="Name Value:" VerticalAlignment="Top" />         <TextBlock Grid.Row="2" Height="23" HorizontalAlignment="Left" Margin="32,0,0,0" Name="textBlock2" Text="Title Value:" VerticalAlignment="Top" />         <TextBlock Grid.Row="3" Height="23" HorizontalAlignment="Left" Margin="32,0,0,0" Name="textBlock3" Text="Non Existant Value:" VerticalAlignment="Top" />         <TextBlock Grid.Column="1" Grid.Row="1" Height="23" HorizontalAlignment="Left" Name="textBlock4" Text="{Binding NameValue, TargetNullValue='No Name!!!!!!!'}" VerticalAlignment="Top" Margin="6,0,0,0" />         <TextBlock Grid.Column="1" Grid.Row="2" Height="23" HorizontalAlignment="Left" Name="textBlock5" Text="{Binding TitleValue, TargetNullValue='No Title!!!!!!!'}" VerticalAlignment="Top" Margin="6,0,0,0" />         <TextBlock Grid.Column="1" Grid.Row="3" Height="23" HorizontalAlignment="Left" Margin="6,0,0,0" Name="textBlock6" Text="{Binding AgeValue, FallbackValue='No such property!'}" VerticalAlignment="Top" />    This XAML defines three textblocks – two of which use the TargetNull and one that uses the FallbackValue markup extensions.  4. Run the application and see the person name displayed as defined for the person object, the expected string displayed for the TargetNullValue when no value exists for the boudn property and the expected string displayed for the FallbackValue when the property bound to is not found on the bound object. It's that easy!

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  • OpenGL Fast-Object Instancing Error

    - by HJ Media Studios
    I have some code that loops through a set of objects and renders instances of those objects. The list of objects that needs to be rendered is stored as a std::map, where an object of class MeshResource contains the vertices and indices with the actual data, and an object of classMeshRenderer defines the point in space the mesh is to be rendered at. My rendering code is as follows: glDisable(GL_BLEND); glEnable(GL_CULL_FACE); glDepthMask(GL_TRUE); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_DEPTH_TEST); for (std::map<MeshResource*, std::vector<MeshRenderer*> >::iterator it = renderables.begin(); it != renderables.end(); it++) { it->first->setupBeforeRendering(); cout << "<"; for (unsigned long i =0; i < it->second.size(); i++) { //Pass in an identity matrix to the vertex shader- used here only for debugging purposes; the real code correctly inputs any matrix. uniformizeModelMatrix(Matrix4::IDENTITY); /** * StartHere fix rendering problem. * Ruled out: * Vertex buffers correctly. * Index buffers correctly. * Matrices correct? */ it->first->render(); } it->first->cleanupAfterRendering(); } geometryPassShader->disable(); glDepthMask(GL_FALSE); glDisable(GL_CULL_FACE); glDisable(GL_DEPTH_TEST); The function in MeshResource that handles setting up the uniforms is as follows: void MeshResource::setupBeforeRendering() { glEnableVertexAttribArray(0); glEnableVertexAttribArray(1); glEnableVertexAttribArray(2); glEnableVertexAttribArray(3); glEnableVertexAttribArray(4); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, iboID); glBindBuffer(GL_ARRAY_BUFFER, vboID); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0); // Vertex position glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 12); // Vertex normal glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 24); // UV layer 0 glVertexAttribPointer(3, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 32); // Vertex color glVertexAttribPointer(4, 1, GL_UNSIGNED_SHORT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 44); //Material index } The code that renders the object is this: void MeshResource::render() { glDrawElements(GL_TRIANGLES, geometry->numIndices, GL_UNSIGNED_SHORT, 0); } And the code that cleans up is this: void MeshResource::cleanupAfterRendering() { glDisableVertexAttribArray(0); glDisableVertexAttribArray(1); glDisableVertexAttribArray(2); glDisableVertexAttribArray(3); glDisableVertexAttribArray(4); } The end result of this is that I get a black screen, although the end of my rendering pipeline after the rendering code (essentially just drawing axes and lines on the screen) works properly, so I'm fairly sure it's not an issue with the passing of uniforms. If, however, I change the code slightly so that the rendering code calls the setup immediately before rendering, like so: void MeshResource::render() { setupBeforeRendering(); glDrawElements(GL_TRIANGLES, geometry->numIndices, GL_UNSIGNED_SHORT, 0); } The program works as desired. I don't want to have to do this, though, as my aim is to set up vertex, material, etc. data once per object type and then render each instance updating only the transformation information. The uniformizeModelMatrix works as follows: void RenderManager::uniformizeModelMatrix(Matrix4 matrix) { glBindBuffer(GL_UNIFORM_BUFFER, globalMatrixUBOID); glBufferSubData(GL_UNIFORM_BUFFER, 0, sizeof(Matrix4), matrix.ptr()); glBindBuffer(GL_UNIFORM_BUFFER, 0); }

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  • What is the value in hiding the details through abstractions? Isn't there value in transparency?

    - by user606723
    Background I am not a big fan of abstraction. I will admit that one can benefit from adaptability, portability and re-usability of interfaces etc. There is real benefit there, and I don't wish to question that, so let's ignore it. There is the other major "benefit" of abstraction, which is to hide implementation logic and details from users of this abstraction. The argument is that you don't need to know the details, and that one should concentrate on their own logic at this point. Makes sense in theory. However, whenever I've been maintaining large enterprise applications, I always need to know more details. It becomes a huge hassle digging deeper and deeper into the abstraction at every turn just to find out exactly what something does; i.e. having to do "open declaration" about 12 times before finding the stored procedure used. This 'hide the details' mentality seems to just get in the way. I'm always wishing for more transparent interfaces and less abstraction. I can read high level source code and know what it does, but I'll never know how it does it, when how it does it, is what I really need to know. What's going on here? Has every system I've ever worked on just been badly designed (from this perspective at least)? My philosophy When I develop software, I feel like I try to follow a philosophy I feel is closely related to the ArchLinux philosophy: Arch Linux retains the inherent complexities of a GNU/Linux system, while keeping them well organized and transparent. Arch Linux developers and users believe that trying to hide the complexities of a system actually results in an even more complex system, and is therefore to be avoided. And therefore, I never try to hide complexity of my software behind abstraction layers. I try to abuse abstraction, not become a slave to it. Question at heart Is there real value in hiding the details? Aren't we sacrificing transparency? Isn't this transparency valuable?

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  • Is comparing an OO compiler to a SQL compiler/optimizer valid?

    - by Brad
    I'm now doing a lot of SQL development at my new job where as before I was doing Object Oriented desktop app stuff. I keep running across very large scripts (thousands of lines) and wanting to refactor in some way. I am seeing that SQL is a different sort of beast and it's probably fine to have these big scripts for the most part but while explaining this to me people are also insisting that the whole idea of refactoring is bad. That stuff like the .NET compiler are actually burdened by refactored code and that a big wall of code is more efficient and better design than code designed for reuse, readability and scalability. The other argument is that OO compilers are almost dangerously inefficient and don't have efficient memory management or runs too many CPU instructions compared to older "simpler" compilers and compared to SQL. Are these valid complaints? Even if some compiler like a C compiler is modestly more "efficient" (whatever that means on this high of a level without seeing code) would you want to write applications in C over C# or Java? Is comparing an OO compiler to a SQL compiler/optimizer even valid?

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  • Understanding Visitor Pattern

    - by Nezreli
    I have a hierarchy of classes that represents GUI controls. Something like this: Control-ContainerControl-Form I have to implement a series of algoritms that work with objects doing various stuff and I'm thinking that Visitor pattern would be the cleanest solution. Let take for example an algorithm which creates a Xml representaion of a hierarchy of objects. Using 'classic' approach I would do this: public abstract class Control { public virtual XmlElement ToXML(XmlDocument document) { XmlElement xml = document.CreateElement(this.GetType().Name); // Create element, fill it with attributes declared with control return xml; } } public abstract class ContainerControl : Control { public override XmlElement ToXML(XmlDocument document) { XmlElement xml = base.ToXML(document); // Use forech to fill XmlElement with child XmlElements return xml; } } public class Form : ContainerControl { public override XmlElement ToXML(XmlDocument document) { XmlElement xml = base.ToXML(document); // Fill remaining elements declared in Form class return xml; } } But I'm not sure how to do this with visitor pattern. This is the basic implementation: public class ToXmlVisitor : IVisitor { public void Visit(Form form) { } } Since even the abstract classes help with implementation I'm not sure how to do that properly in ToXmlVisitor. Perhaps there is a better solution to this problem. The reason that I'm considering Visitor pattern is that some algorithms will need references not available in project where the classes are implemented and there is a number of different algorithms so I'm avoiding large classes. Any thoughts are welcome.

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  • Pattern for a class that does only one thing

    - by Heinzi
    Let's say I have a procedure that does stuff: void doStuff(initalParams) { ... } Now I discover that "doing stuff" is quite a compex operation. The procedure becomes large, I split it up into multiple smaller procedures and soon I realize that having some kind of state would be useful while doing stuff, so that I need to pass less parameters between the small procedures. So, I factor it out into its own class: class StuffDoer { private someInternalState; public Start(initalParams) { ... } // some private helper procedures here ... } And then I call it like this: new StuffDoer().Start(initialParams); or like this: new StuffDoer(initialParams).Start(); And this is what feels wrong. When using the .NET or Java API, I always never call new SomeApiClass().Start(...);, which makes me suspect that I'm doing it wrong. Sure, I could make StuffDoer's constructor private and add a static helper method: public static DoStuff(initalParams) { new StuffDoer().Start(initialParams); } But then I'd have a class whose external interface consists of only one static method, which also feels weird. Hence my question: Is there a well-established pattern for this type of classes that have only one entry point and have no "externally recognizable" state, i.e., instance state is only required during execution of that one entry point?

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  • [C#][XNA] Draw() 20,000 32 by 32 Textures or 1 Large Texture 20,000 Times

    - by Rudi
    The title may be confusing - sorry about that, it's a poor summary. Here's my dilemma. I'm programming in C# using the .NET Framework 4, and aiming to make a tile-based game with XNA. I have one large texture (256 pixels by 4096 pixels). Remember this is a tile-based game, so this texture is so massive only because it contains many tiles, which are each 32 pixels by 32 pixels. I think the experts will definitely know what a tile-based game is like. The orientation is orthogonal (like a chess board), not isometric. In the Game.Draw() method, I have two choices, one of which will be incredibly more efficient than the other. Choice/Method #1: Semi-Pseudocode: public void Draw() { // map tiles are drawn left-to-right, top-to-bottom for (int x = 0; x < mapWidth; x++) { for (int y = 0; y < mapHeight; y++) { SpriteBatch.Draw( MyLargeTexture, // One large 256 x 4096 texture new Rectangle(x, y, 32, 32), // Destination rectangle - ignore this, its ok new Rectangle(x, y, 32, 32), // Notice the source rectangle 'cuts out' 32 by 32 squares from the texture corresponding to the loop Color.White); // No tint - ignore this, its ok } } } Caption: So, effectively, the first method is referencing one large texture many many times, each time using a small rectangle of this large texture to draw the appropriate tile image. Choice/Method #2: Semi-Pseudocode: public void Draw() { // map tiles are drawn left-to-right, top-to-bottom for (int x = 0; x < mapWidth; x++) { for (int y = 0; y < mapHeight; y++) { Texture2D tileTexture = map.GetTileTexture(x, y); // Getting a small 32 by 32 texture (different each iteration of the loop) SpriteBatch.Draw( tileTexture, new Rectangle(x, y, 32, 32), // Destination rectangle - ignore this, its ok new Rectangle(0, 0, tileTexture.Width, tileTexture.Height), // Notice the source rectangle uses the entire texture, because the entire texture IS 32 by 32 Color.White); // No tint - ignore this, its ok } } } Caption: So, effectively, the second method is drawing many small textures many times. The Question: Which method and why? Personally, I would think it would be incredibly more efficient to use the first method. If you think about what that means for the tile array in a map (think of a large map with 2000 by 2000 tiles, let's say), each Tile object would only have to contain 2 integers, for the X and Y positions of the source rectangle in the one large texture - 8 bytes. If you use method #2, however, each Tile object in the tile array of the map would have to store a 32by32 Texture - an image - which has to allocate memory for the R G B A pixels 32 by 32 times - is that 4096 bytes per tile then? So, which method and why? First priority is speed, then memory-load, then efficiency or whatever you experts believe.

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  • Avoiding bloated Domain Objects

    - by djcredo
    We're trying to move data from our bloated Service layer into our Domain layer using a DDD approach. We currently have a lot of business logic in our services, which is spread out all over the place and doesn't benefit from inheritance. We have a central Domain class which is the focus of most of our work - a Trade. The Trade object will know how to price itself, how to estimate risk, validate itself, etc. We can then replace conditionals with polymorphism. Eg: SimpleTrade will price itself one way, but ComplexTrade will price itself another. However, we are worried that this will bloat the Trade class(s). It really should be in charge of its own processing but the class size is going to increase exponentially as more features are added. So we have choices: Put processing logic in Trade class. Processing logic is now polymorphic based on the type of the trade, but Trade class is now has multiple responsibilites (pricing, risk, etc) and is large Put processing logic into other class such as TradePricingService. No longer polymorphic with the Trade inheritance tree, but classes are smaller and easier to test. What would be the suggested approach?

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  • My proposed design is usually worse than my colleague's - how do I get better?

    - by user151193
    I have been programming for couple of years and am generally good when it comes to fixing problems and creating small-to-medium scripts, however, I'm generally not good at designing large scale programs in object oriented way. Few questions Recently, a colleague who has same number of years of experience as me and I were working on a problem. I was working on a problem longer than him, however, he came up with a better solution and in the end we're going to use his design. This really affected me. I admit his design is better, but I wanted to come up with a design as good as his. I'm even contemplating quitting the job. Not sure why but suddenly I feel under some pressure e.g. what would juniors think of me and etc? Is it normal? Or I'm thinking a little too much into this? My job involves programming in Python. I try to read source code but how do you think I can improve me design skills? Are there any good books or software that I should study? Please enlighten me. I will really appreciate your help.

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  • Design suggestions needed to create a MathBuilder framework

    - by Darf Zon
    Let explain what I'm trying to create. I'm creating a framework, the idea is to provide base classes to generate a math problem. Why do I need this framework? Because at first time, I realized when I create a new math problem I always do the same steps. Configuration settings such range numbers. For example if I'm developing multiplications, in beginner level only generate the first number between 2-5 or in advanced level, the first number will be between 6- 9, for example. Generate problem method. All the time I need to invoke a method like this to generate the problem. This one receives the configuration settings and generate the number according to them. And generate the object with the respective data. Validate the problem. Sometimes the problem generated is not valid. For example, supposed I'm creating fractions in most simplified, if I receive 2/4, the program should detect that this is not valid and must generate another like this one, 1/4. Load the view. All of them, have a custom view (please watch below the images). All of the problems must know how to CHECK if the user result is correct. All of this problems has answers. Some of them just require one answer, anothers may require more than one, so I guess a way to maintain flexibility to the developer has all the answers he wanna used. At the beginning I started using PRISM. Generate modules for each math problem was the idea and load it in the main system. I guess are the most important things of this idea. Let me showing some problems which I create in a WPF standalone program. Here I have a math problem about areas. When I generate the problem a set to the view the object and it draw it. In beginner level, I set in the configuration settings that just load square types. But in advance level, can load triangles and squares randomly. In this another, generate a binary problem like addition, subtraction, multiplication or division. Above just generate a single problem. The idea of this is to show a test o quiz, I mean get a worksheet (this I call as a collection of problems) where the user can answer it. I hope gets the idea with my ugly drawing. How to load this math problems? As I said above, I started using PRISM, and each module contains a math problem kind. This is a snapshot of my first demo. Below show the modules loaded, and center the respective configurations or levels. Until momment, I have no idea to start creating this software. I just know that I need a question | problem class, response class, user class. But I get lost about what properties should have to contain in it. Please give a little hand of this framework. I put much effort on this question, so if any isn't clear, let me know to clarify it.

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  • Starting to create a MathBuilder framework, help to start creating the design

    - by Darf Zon
    Let explain what I'm trying to create. I'm creating a framework, the idea is to provide base classes to generate a math problem. Why do I need this framework? Because at first time, I realized when I create a new math problem I always do the same steps. Configuration settings such range numbers. For example if I'm developing multiplications, in beginner level only generate the first number between 2-5 or in advanced level, the first number will be between 6- 9, for example. Generate problem method. All the time I need to invoke a method like this to generate the problem. This one receives the configuration settings and generate the number according to them. And generate the object with the respective data. Validate the problem. Sometimes the problem generated is not valid. For example, supposed I'm creating fractions in most simplified, if I receive 2/4, the program should detect that this is not valid and must generate another like this one, 1/4. Load the view. All of them, have a custom view (please watch below the images). All of the problems must know how to CHECK if the user result is correct. All of this problems has answers. Some of them just require one answer, anothers may require more than one, so I guess a way to maintain flexibility to the developer has all the answers he wanna used. At the beginning I started using PRISM. Generate modules for each math problem was the idea and load it in the main system. I guess are the most important things of this idea. Let me showing some problems which I create in a WPF standalone program. Here I have a math problem about areas. When I generate the problem a set to the view the object and it draw it. In beginner level, I set in the configuration settings that just load square types. But in advance level, can load triangles and squares randomly. In this another, generate a binary problem like addition, subtraction, multiplication or division. Above just generate a single problem. The idea of this is to show a test o quiz, I mean get a worksheet (this I call as a collection of problems) where the user can answer it. I hope gets the idea with my ugly drawing. How to load this math problems? As I said above, I started using PRISM, and each module contains a math problem kind. This is a snapshot of my first demo. Below show the modules loaded, and center the respective configurations or levels. Until momment, I have no idea to start creating this software. I just know that I need a question | problem class, response class, user class. But I get lost about what properties should have to contain in it. Please give a little hand of this framework. I put much effort on this question, so if any isn't clear, let me know to clarify it.

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  • Why is there no service-oriented language?

    - by Wolfgang
    Edit: To avoid further confusion: I am not talking about web services and such. I am talking about structuring applications internally, it's not about how computers communicate. It's about programming languages, compilers and how the imperative programming paradigm is extended. Original: In the imperative programming field, we saw two paradigms in the past 20 years (or more): object-oriented (OO), and service-oriented (SO) aka. component-based (CB). Both paradigms extend the imperative programming paradigm by introducing their own notion of modules. OO calls them objects (and classes) and lets them encapsulates both data (fields) and procedures (methods) together. SO, in contrast, separates data (records, beans, ...) from code (components, services). However, only OO has programming languages which natively support its paradigm: Smalltalk, C++, Java and all other JVM-compatibles, C# and all other .NET-compatibles, Python etc. SO has no such native language. It only comes into existence on top of procedural languages or OO languages: COM/DCOM (binary, C, C++), CORBA, EJB, Spring, Guice (all Java), ... These SO frameworks clearly suffer from the missing native language support of their concepts. They start using OO classes to represent services and records. This leads to designs where there is a clear distinction between classes that have methods only (services) and those that have fields only (records). Inheritance between services or records is then simulated by inheritance of classes. Technically, its not kept so strictly but in general programmers are adviced to make classes to play only one of the two roles. They use additional, external languages to represent the missing parts: IDL's, XML configurations, Annotations in Java code, or even embedded DSL like in Guice. This is especially needed, but not limited to, since the composition of services is not part of the service code itself. In OO, objects create other objects so there is no need for such facilities but for SO there is because services don't instantiate or configure other services. They establish an inner-platform effect on top of OO (early EJB, CORBA) where the programmer has to write all the code that is needed to "drive" SO. Classes represent only a part of the nature of a service and lots of classes have to be written to form a service together. All that boiler plate is necessary because there is no SO compiler which would do it for the programmer. This is just like some people did it in C for OO when there was no C++. You just pass the record which holds the data of the object as a first parameter to the procedure which is the method. In a OO language this parameter is implicit and the compiler produces all the code that we need for virtual functions etc. For SO, this is clearly missing. Especially the newer frameworks extensively use AOP or introspection to add the missing parts to a OO language. This doesn't bring the necessary language expressiveness but avoids the boiler platform code described in the previous point. Some frameworks use code generation to produce the boiler plate code. Configuration files in XML or annotations in OO code is the source of information for this. Not all of the phenomena that I mentioned above can be attributed to SO but I hope it clearly shows that there is a need for a SO language. Since this paradigm is so popular: why isn't there one? Or maybe there are some academic ones but at least the industry doesn't use one.

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  • What are the disadvantages of self-encapsulation?

    - by Dave Jarvis
    Background Tony Hoare's billion dollar mistake was the invention of null. Subsequently, a lot of code has become riddled with null pointer exceptions (segfaults) when software developers try to use (dereference) uninitialized variables. In 1989, Wirfs-Brock and Wikerson wrote: Direct references to variables severely limit the ability of programmers to re?ne existing classes. The programming conventions described here structure the use of variables to promote reusable designs. We encourage users of all object-oriented languages to follow these conventions. Additionally, we strongly urge designers of object-oriented languages to consider the effects of unrestricted variable references on reusability. Problem A lot of software, especially in Java, but likely in C# and C++, often uses the following pattern: public class SomeClass { private String someAttribute; public SomeClass() { this.someAttribute = "Some Value"; } public void someMethod() { if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { return this.someAttribute; } } Sometimes a band-aid solution is used by checking for null throughout the code base: public void someMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void anotherMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Default Value" ) ) { // do something... } } The band-aid does not always avoid the null pointer problem: a race condition exists. The race condition is mitigated using: public void anotherMethod() { String someAttribute = this.someAttribute; assert someAttribute != null; if( someAttribute.equals( "Some Default Value" ) ) { // do something... } } Yet that requires two statements (assignment to local copy and check for null) every time a class-scoped variable is used to ensure it is valid. Self-Encapsulation Ken Auer's Reusability Through Self-Encapsulation (Pattern Languages of Program Design, Addison Wesley, New York, pp. 505-516, 1994) advocated self-encapsulation combined with lazy initialization. The result, in Java, would resemble: public class SomeClass { private String someAttribute; public SomeClass() { setAttribute( "Some Value" ); } public void someMethod() { if( getAttribute().equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { String someAttribute = this.someAttribute; if( someAttribute == null ) { setAttribute( createDefaultValue() ); } return someAttribute; } protected String createDefaultValue() { return "Some Default Value"; } } All duplicate checks for null are superfluous: getAttribute() ensures the value is never null at a single location within the containing class. Efficiency arguments should be fairly moot -- modern compilers and virtual machines can inline the code when possible. As long as variables are never referenced directly, this also allows for proper application of the Open-Closed Principle. Question What are the disadvantages of self-encapsulation, if any? (Ideally, I would like to see references to studies that contrast the robustness of similarly complex systems that use and don't use self-encapsulation, as this strikes me as a fairly straightforward testable hypothesis.)

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  • Is my class structure good enough?

    - by Rivten
    So I wanted to try out this challenge on reddit which is mostly about how you structure your data the best you can. I decided to challenge my C++ skills. Here's how I planned this. First, there's the Game class. It deals with time and is the only class main has access to. A game has a Forest. For now, this class does not have a lot of things, only a size and a Factory. Will be put in better use when it will come to SDL-stuff I guess A Factory is the thing that deals with the Game Objects (a.k.a. Trees, Lumberjack and Bears). It has a vector of all GameObjects and a queue of Events which will be managed at the end of one month. A GameObject is an abstract class which can be updated and which can notify the Event Listener The EventListener is a class which handles all the Events of a simulation. It can recieve events from a Game Object and notify the Factory if needed, the latter will manage correctly the event. So, the Tree, Lumberjack and Bear classes all inherits from GameObject. And Sapling and Elder Tree inherits from Tree. Finally, an Event is defined by an event_type enumeration (LUMBERJACK_MAWED, SAPPLING_EVOLUTION, ...) and an event_protagonists union (a GameObject or a pair of GameObject (who killed who ?)). I was quite happy at first with this because it seems quite logic and flexible. But I ended up questionning this structure. Here's why : I dislike the fact that a GameObject need to know about the Factory. Indeed, when a Bear moves somewhere, it needs to know if there's a Lumberjack ! Or it is the Factory which handles places and objects. It would be great if a GameObject could only interact with the EventListener... or maybe it's not that much of a big deal. Wouldn't it be better if I separate the Factory in three vectors ? One for each kind of GameObject. The idea would be to optimize research. If I'm looking do delete a dead lumberjack, I would only have to look in one shorter vector rather than a very long vector. Another problem arises when I want to know if there is any particular object in a given case because I have to look for all the gameObjects and see if they are at the given case. I would tend to think that the other idea would be to use a matrix but then the issue would be that I would have empty cases (and therefore unused space). I don't really know if Sapling and Elder Tree should inherit from Tree. Indeed, a Sapling is a Tree but what about its evolution ? Should I just delete the sapling and say to the factory to create a new Tree at the exact same place ? It doesn't seem natural to me to do so. How could I improve this ? Is the design of an Event quite good ? I've never used unions before in C++ but I didn't have any other ideas about what to use. Well, I hope I have been clear enough. Thank you for taking the time to help me !

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  • Can I set a property on an object that is only declared on the instance type, when I don't know the

    - by WilberBeast
    Let me explain. I have a List into which I am adding various ASP.NET controls. I then wish to loop through the list and set a CssClass, however not every Control supports the property CssClass. What I would like to do is test if the underlying instance type supports the CssClass property and set it, but I'm not sure how to do the conversion prior to setting the property since I don't know the type of each Control object. I know that I can use typeof or x.GetType(), but I'm not sure how to use these to convert the controls back to the instance type in order to test for and then set the property. Actually I seem to have solved this, so I thought that I would post the code here for others. foreach (Control c in controlList) { PropertyInfo pi = c.GetType().GetProperty("CssClass"); if (pi != null) pi.SetValue(c, "desired_css_class", null); } I hope that this helps someone else as I has taken me hours to research these 2 lines of code. Cheers Steve

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  • Why ruby object has two to_s and inspect methods that (looks like) do the same thing?

    - by prosseek
    The p calls inspect, and puts/print calls to_s for representing its object. If I run class Graph def initialize @nodeArray = Array.new @wireArray = Array.new end def to_s # called with print / puts "Graph : #{@nodeArray.size}" end def inspect # called with p "G" end end if __FILE__ == $0 gr = Graph.new p gr print gr puts gr end I get G Graph : 0Graph : 0 Then, why does ruby has two functions do the same thing? What makes the difference between to_s and inspect? And what's the difference between puts/print/p? If I comment out the to_s or inspect function, I get as follows. #<Graph:0x100124b88>#<Graph:0x100124b88>

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  • Java: How do you access a sub-object of an object with no "getXXX" method to that sub-object

    - by Daxon
    I'll explain with pictures from Eclipse Debugger I have an Class called "FieldContext", (I can't edit it, it's compiled in the Java OVal API) Within "FieldContext" on the eclipse variable tab are "CompileTimeType" and "field" Q1 Is there a legend for the icons in the variables tab? like what the red box with the "F" means + yellow diamond boxes? Now I want to access the fields inside the "field" object (RedBox) .. preferably "name" But the "FieldContext" does not have a "getField()" method, yet it has a "getCompileTimeType()" method. Q2 So is there anyway to get that field object being a "SerializableField" Class from the "FieldContext"? If eclipse debugger can see/get/edit them then I hope I can do the same in Java.

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