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  • Misconceptions about purely functional languages?

    - by Giorgio
    I often encounter the following statements / arguments: Pure functional programming languages do not allow side effects (and are therefore of little use in practice because any useful program does have side effects, e.g. when it interacts with the external world). Pure functional programming languages do not allow to write a program that maintains state (which makes programming very awkward because in many application you do need state). I am not an expert in functional languages but here is what I have understood about these topics until now. Regarding point 1, you can interact with the environment in purely functional languages but you have to explicitly mark the code (functions) that introduces them (e.g. in Haskell by means of monadic types). Also, AFAIK computing by side effects (destructively updating data) should also be possible (using monadic types?) but is not the preferred way of working. Regarding point 2, AFAIK you can represent state by threading values through several computation steps (in Haskell, again, using monadic types) but I have no practical experience doing this and my understanding is rather vague. So, are the two statements above correct in any sense or are they just misconceptions about purely functional languages? If they are misconceptions, how did they come about? Could you write a (possibly small) code snippet illustrating the Haskell idiomatic way to (1) implement side effects and (2) implement a computation with state?

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  • Requesting quality analysis test cases up front of implementation/change

    - by arin
    Recently I have been assigned to work on a major requirement that falls between a change request and an improvement. The previous implementation was done (badly) by a senior developer that left the company and did so without leaving a trace of documentation. Here were my initial steps to approach this problem: Considering that the release date was fast approaching and there was no time for slip-ups, I initially asked if the requirement was a "must have". Since the requirement helped the product significantly in terms of usability, the answer was "If possible, yes". Knowing the wide-spread use and affects of this requirement, had it come to a point where the requirement could not be finished prior to release, I asked if it would be a viable option to thrash the current state and revert back to the state prior to the ex-senior implementation. The answer was "Most likely: no". Understanding that the requirement was coming from the higher management, and due to the complexity of it, I asked all usability test cases to be written prior to the implementation (by QA) and given to me, to aid me in the comprehension of this task. This was a big no-no for the folks at the management as they failed to understand this approach. Knowing that I had to insist on my request and the responsibility of this requirement, I insisted and have fallen out of favor with some of the folks, leaving me in a state of "baffledness". Basically, I was trying a test-driven approach to a high-risk, high-complexity and must-have requirement and trying to be safe rather than sorry. Is this approach wrong or have I approached it incorrectly? P.S.: The change request/improvement was cancelled and the implementation was reverted back to the prior state due to the complexity of the problem and lack of time. This only happened after a 2 hour long meeting with other seniors in order to convince the aforementioned folks.

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  • Collision within a poly

    - by G1i1ch
    For an html5 engine I'm making, for speed I'm using a path poly. I'm having trouble trying to find ways to get collision with the walls of the poly. To make it simple I just have a vector for the object and an array of vectors for the poly. I'm using Cartesian vectors and they're 2d. Say poly = [[550,0],[169,523],[-444,323],[-444,-323],[169,-523]], it's just a pentagon I generated. The object that will collide is object, object.pos is it's position and object.vel is it's velocity. They're both 2d vectors too. I've had some success to get it to find a collision, but it's just black box code I ripped from a c++ example. It's very obscure inside and all it does though is return true/false and doesn't return what vertices are collided or collision point, I'd really like to be able to understand this and make my own so I can have more meaningful collision. I'll tackle that later though. Again the question is just how does one find a collision to walls of a poly given you know the poly vertices and the object's position + velocity? If more info is needed please let me know. And if all anyone can do is point me to the right direction that's great.

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  • Microeconomical simulation: coordination/planning between self-interested trading agents

    - by Milton Manfried
    In a typical perfect-information strategy game like Chess, an agent can calculate its best move by searching the state tree for the best possible move, while assuming that the opponent will also make the best possible move (i.e. Mini-max). I would like to use this approach in a "game" modeling economic activity, where the possible "moves" would be to buy or sell for a given price, and the goal, rather than a specific class of states (e.g. Checkmate), would be to maximize some function F of the agent's state (e.g. F(money, widget) = 10*money + widget). How to handle buy/sell actions that require coordination between both parties, at the very least agreement upon a price? The cheap way out would be to set the price beforehand, maybe based upon the current supply -- but the idea of this simulation is to examine how prices emerge when freely determined by "perfectly rational" agents. A great example of what I do not want is the trading algorithm in SugarScape -- paraphrasing from Growing Artificial Societies p101-102: when a pair of agents interact to trade, they each compute their internal valuations of the goods, then a bargaining process is conducted and a price is agreed to. If this price makes both agents better off, they complete the transaction The protocol itself is beautiful, but what it cannot capture (as far as I can tell) is the ability for an agent to pay more than it might otherwise for a good, because it knows that it can sell it for even more at a later date -- what appears to be called "strategic thinking" in this pape at Google Books Multi-Agent-Based Simulation III: 4th International Workshop, MABS 2003... to get realistic behavior like that, it seems one would either (1) have to build an outrageously-complex internal valuation system which could at best only cover situations that were planned for at compile-time, or otherwise (2) have some mechanism to search the state tree... which would require some way of planning future trades. Note: The chess analogy only works as far as the state-space search goes; the simulation isn't intended to be "zero sum", so a literal mini-max search wouldn't be appropriate -- and ideally, it should work with more than two agents.

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  • How can I use a script to control a VirtualBox guest?

    - by TheWickerman666
    Refer to : Launch an application in Windows from the Ubuntu desktop I was wondering if Takkat could elaborate on the actual execution i.e. howto in the script file. This will be greatly helpful. Thanks in advance my script file InternetExplorerVM.sh looks like this, execution is /path/to/InternetExplorerVM.sh "C:\Program Files\Internet Explorer\iexplore.exe" #!/bin/bash # start Internet Explorer inside of a Windows7 Ultimate VM echo "Starting 'Internet Explorer' browser inside Windows7 virtual machine" echo "" sleep 1 echo "Please be patient" VBoxManage startvm b307622e-6b5e-4e47-a427-84760cf2312b sleep 15 echo "" echo "Now starting 'Internet Explorer'" ##VBoxManage --nologo guestcontrol b307622e-6b5e-4e47-a427-84760cf2312b execute --image "$1" --username RailroadGuest --password bnsf1234 VBoxManage --nologo guestcontrol b307622e-6b5e-4e47-a427-84760cf2312b execute --image "C:\\Program/ Files\\Internet/ Explorer\\iexplore.exe" --username RailroadGuest --password bnsf1234 --wait-exit --wait-stdout echo "" echo "Saving the VM's state now" VBoxManage controlvm b307622e-6b5e-4e47-a427-84760cf2312b savestate sleep 2 #Check VM state echo "" echo "Check the VM state" VBoxManage showvminfo b307622e-6b5e-4e47-a427-84760cf2312b | grep State exit My apologies for any mistakes, this is my first time posting on askubuntu.Thanks a ton in advance. This has been very helpful. Need this for BNSF guests, their Mainframe emulator works exclusively on Java enabled Internet Explorer.

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  • whats the name of this pattern?

    - by Wes
    I see this a lot in frameworks. You have a master class which other classes register with. The master class then decides which of the registered classes to delegate the request to. An example based passed in class may be something this. public interface Processor { public boolean canHandle(Object objectToHandle); public void handle(Object objectToHandle); } public class EvenNumberProcessor extends Processor { public boolean canHandle(Object objectToHandle) { if (!isNumeric(objectToHandle)){ return false } return isEven(objectToHandle); } public void handle(objectToHandle) { //Optionally call canHandleAgain to ensure the calling class is fufilling its contract doSomething(); } } public class OddNumberProcessor extends Processor { public boolean canHandle(Object objectToHandle) { if (!isNumeric(objectToHandle)){ return false } return isOdd(objectToHandle); } public void handle(objectToHandle) { //Optionally call canHandleAgain to ensure the calling class is fufilling its contract doSomething(); } } //Can optionally implement processor interface public class processorDelegator { private List processors; public void addProcessor(Processor processor) { processors.add(processor); } public void process(Object objectToProcess) { //Lookup relevant processor either by keeping a list of what they can process //Or query each one to see if it can process the object. chosenProcessor=chooseProcessor(objectToProcess); chosenProcessor.handle(objectToProcess); } } Note there are a few variations I see on this. In one variation the sub classes provide a list of things they can process which the ProcessorDelegator understands. The other variation which is listed above in fake code is where each is queried in turn. This is similar to chain of command but I don't think its the same as chain of command means that the processor needs to pass to other processors. The other variation is where the ProcessorDelegator itself implements the interface which means you can get trees of ProcessorDelegators which specialise further. In the above example you could have a numeric processor delegator which delegates to an even/odd processor and a string processordelegator which delegates to different strings. My question is does this pattern have a name.

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  • Abstract Factory Method and Polymorphism

    - by Scotty C.
    Being a PHP programmer for the last couple of years, I'm just starting to get into advanced programming styles and using polymorphic patterns. I was watching a video on polymorphism the other day, and the guy giving the lecture said that if at all possible, you should get rid of if statements in your code, and that a switch is almost always a sign that polymorphism is needed. At this point I was quite inspired and immediately went off to try out these new concepts, so I decided to make a small caching module using a factory method. Of course the very first thing I have to do is create a switch to decide what file encoding to choose. DANG! class Main { public static function methodA($parameter='') { switch ($parameter) { case 'a': $object = new \name\space\object1(); break; case 'b': $object = new \name\space\object2(); break; case 'c': $object = new \name\space\object3(); break; default: $object = new \name\space\object1(); } return (sekretInterface $object); } } At this point I'm not really sure what to do. As far as I can tell, I either have to use a different pattern and have separate methods for each object instance, or accept that a switch is necessary to "switch" between them. What do you guys think?

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  • dpkg in uninterruptible sleep

    - by Khaled
    I have several Ubuntu servers 10.04. Today, I tried to upgrade some packages on one of these servers and the process got stuck. I logged in using another SSH session and I found that dpkg is in D state (uninterruptible sleep). According to what I have read, this state results generally from I/O waiting like waiting for NFS share. I can not understand why dpkg will block in this state. I can not see any obvious problems other than this. Here is the output of ps to show the blocking process: $ ps axo pid,cmd,s,wchan | grep dpkg 22571 /usr/bin/dpkg --status-fd 2 D call_rwsem_down_read_failed This process can not be killed even with kill -9. So, I will not be able to install/upgrade any package unless I reboot the server. What makes it worse is that the remote reboot does not succeed in such a case (having processes in D state). Can anyone help with this? How can I avoid this in the future.

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  • 3d Picking under reticle

    - by Wolftousen
    i'm currently trying to work out some 3d picking code that I started years ago, but then lost interested the assignment was completed (this part wasn't actually part of the assignment). I am not using the mouse coords for picking, i'm just using the position in 3d space and a ray directly out from there. A small hitch though is that I want to use a cone and not a ray. Here are the variables i'm using: float iReticleSlope = 95/3000; //inverse reticle slope float baseReticle = 1; //radius of the reticle at z = 0 float maxRange = 3000; //max range to target Quaternion orientation; //the cameras orientation Vector3d position; //the cameras position Then I loop through each object in the world: Vector3d transformed; //object position after transformations float d, r; //holder variables for(i = 0; i < objects.length; i++) { transformed = position - objects[i].position; //transform the position relative to camera orientation.multiply(transformed); //orient the object relative to the camera if(transformed.z < 0) { d = sqrt(transformed[0] * transformed[0] + transformed[1] * transformed[1]); r = -transformed[2] * iReticleSlope + objects[i].radius; if(d < r && -transformed[2] - objects[i].radius <= maxRange) { //the object is under the reticle } else { //the object is not under the reticle } } else { //the object is not under the reticle } } Now this all works fine and dandy until the window ratio doesn't match the resolution ratio. Is there any simple way to account for that

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  • Basic Mouse Features in Silverlight

    - by Sayre Collado
    Hi Guys, I have basic sample on how to use some features of mouse events in Silverlight. The picture. The Mouse Activity Log is to record the all activity done on the projects. My simple snippets on how to add on the textbox is:         protected void MessageLog(string msg)         {             txtMouseLog.Text += msg;         }   For the Mouse Wheel sample this is the snippets:         private void chkMouseWheel_Checked(object sender, RoutedEventArgs e)         {             image1.MouseWheel += new MouseWheelEventHandler(image1_MouseWheel);         }           void image1_MouseWheel(object sender, MouseWheelEventArgs e)         {             ImgScale.ScaleX = e.Delta > 0 ? ImgScale.ScaleX * 1.5 : ImgScale.ScaleX * 0.8;             ImgScale.ScaleY = e.Delta > 0 ? ImgScale.ScaleY * 1.5 : ImgScale.ScaleY * 0.8;               e.Handled = true;         }    And the XAML:        <Image Height="139" Name="image1" Stretch="Fill" Width="178" Source="/GBLOgs1;component/Images/Sunset.jpg">            <Image.RenderTransform>                 <ScaleTransform x:Name="ImgScale"></ScaleTransform>            </Image.RenderTransform>        </Image     I have also the showing of mouse position:           private void Mouse_MouseMove(object sender, MouseEventArgs e)         {             Point point = e.GetPosition(this);             lblMouseLocation.Content = "X: " + point.X + "and Y: " + point.Y;         }           private void checkBox1_Checked(object sender, RoutedEventArgs e)         {             lblMouseLocation.Visibility = Visibility.Visible;             MessageLog("Mouse Location Visible\n");         }           private void checkBox1_Unchecked(object sender, RoutedEventArgs e)         {             lblMouseLocation.Visibility = Visibility.Collapsed;             MessageLog("Mouse Location Collapsed\n");            And even the counting of clicked event:           int clicked = 0;         private void LayoutRoot_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)         {             Point point = e.GetPosition(this);             clicked++;               string msg = "Mouse Clicked " + clicked.ToString() + " time(s) " +                                     "Mouse Location X and Y: " + point.X + " " + point.Y + "\n";               MessageLog(msg);         }     And now the result of above snippets. Happy Programming.

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  • Persisting simple tree with (Fluent-)NHibernate leads to System.InvalidCastException

    - by fudge
    Hi there, there seems to be a problem with recursive data structures and (Fluent-)NHibernate or its just me, being a complete moron... here's the tree: public class SimpleNode { public SimpleNode () { this.Children = new List<SimpleNode> (); } public virtual SimpleNode Parent { get; private set; } public virtual List<SimpleNode> Children { get; private set; } public virtual void setParent (SimpleNode parent) { parent.AddChild (this); Parent = parent; } public virtual void AddChild (SimpleNode child) { this.Children.Add (child); } public virtual void AddChildren (IEnumerable<SimpleNode> children) { foreach (var child in children) { AddChild (child); } } } the mapping: public class SimpleNodeEntity : ClassMap<SimpleNode> { public SimpleNodeEntity () { Id (x => x.Id); References (x => x.Parent).Nullable (); HasMany (x => x.Children).Not.LazyLoad ().Inverse ().Cascade.All ().KeyNullable (); } } now, whenever I try to save a node, I get this: System.InvalidCastException: Cannot cast from source type to destination type. at (wrapper dynamic-method) SimpleNode. (object,object[],NHibernate.Bytecode.Lightweight.SetterCallback) at NHibernate.Bytecode.Lightweight.AccessOptimizer.SetPropertyValues (object,object[]) at NHibernate.Tuple.Entity.PocoEntityTuplizer.SetPropertyValuesWithOptimizer (object,object[]) My setup: Mono 2.8.1 (on OSX), NHibernate 2.1.2, FluentNHibernate 1.1.0

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  • XNA Windows Phone 7 Sprite movement

    - by Darren Gaughan
    I'm working on a Windows phone game and I'm having difficulty with the sprite movement. What I want to do is make the sprite gradually move to the position that is touched on screen, when there is only one quick touch and release. At the minute all I can do is either make the sprite jump instantly to the touch location or move along to the touch location when the touch is held down. Code for jumping to touch location: TouchCollection touchCollection = TouchPanel.GetState(); foreach (TouchLocation tl in touchCollection) { if ((tl.State == TouchLocationState.Pressed) || (tl.State == TouchLocationState.Moved)) { Vector2 newPos = new Vector2(tl.Position.X,tl.Position.Y); if (position != newPos) { while (position.X < newPos.X) { position.X += (float)theGameTime.ElapsedGameTime.Milliseconds / 10.0f * spriteDirectionRight; } } } } Code to gradually move along while touch is held: TouchCollection touchCollection = TouchPanel.GetState(); foreach (TouchLocation tl in touchCollection) { if ((tl.State == TouchLocationState.Pressed) || (tl.State == TouchLocationState.Moved)) { Vector2 newPos = new Vector2(tl.Position.X,tl.Position.Y); if (position != newPos) { position.X += (float)theGameTime.ElapsedGameTime.Milliseconds / 10.0f * spriteDirectionRight; } } } These are in the Update() method of the Sprite class.

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  • Faster 2D Collision detection

    - by eShredder
    Recently I've been working on a fast-paced 2d shooter and I came across a mighty problem. Collision detection. Sure, it is working, but it is very slow. My goal is: Have lots of enemies on screen and have them to not touch each other. All of the enemies are chasing the player entity. Most of them have the same speed so sooner or later they all end up taking the same space while chasing the player. This really drops the fun factor since, for the player, it looks like you are being chased by one enemy only. To prevent them to take the same space I added a collision detection (a very basic 2D detection, the only method I know of) which is. Enemy class update method Loop through all enemies (continue; if the loop points at this object) If enemy object intersects with this object Push enemy object away from this enemy object This works fine. As long as I only have <200 enemy entities that is. When I get closer to 300-350 enemy entities my frame rate begins to drop heavily. First I thought it was bad rendering so I removed their draw call. This did not help at all so of course I realised it was the update method. The only heavy part in their update method is this each-enemy-loops-through-every-enemy part. When I get closer to 300 enemies the game does a 90000 (300x300) step itteration. My my~ I'm sure there must be another way to aproach this collision detection. Though I have no idea how. The pages I find is about how to actually do the collision between two objects or how to check collision between an object and a tile. I already know those two things. tl;dr? How do I aproach collision detection between LOTS of entities? Quick edit: If it is to any help, I'm using C# XNA.

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  • Are Java's public fields just a tragic historical design flaw at this point?

    - by Avi Flax
    It seems to be Java orthodoxy at this point that one should basically never use public fields for object state. (I don't necessarily agree, but that's not relevant to my question.) Given that, would it be right to say that from where we are today, it's clear that Java's public fields were a mistake/flaw of the language design? Or is there a rational argument that they're a useful and important part of the language, even today? Thanks! Update: I know about the more elegant approaches, such as in C#, Python, Groovy, etc. I'm not directly looking for those examples. I'm really just wondering if there's still someone deep in a bunker, muttering about how wonderful public fields really are, and how the masses are all just sheep, etc. Update 2: Clearly static final public fields are the standard way to create public constants. I was referring more to using public fields for object state (even immutable state). I'm thinking that it does seem like a design flaw that one should use public fields for constants, but not for state… a language's rules should be enforced naturally, by syntax, not by guidelines.

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  • Laptop battery charging capacity reduced to 52%

    - by omjaijagdish
    I have been using Ubuntu 11.04 on DELL Inspiron 14R (N5010) laptop for last three months. Before I switch to ubuntu my laptop battery used to give 2.5 hrs to 3 hrs back-up. But since I have been using ubuntu, it has been reduced to 1hr to 1.5 hrs at max. I tried following commands: $ cat /proc/acpi/battery/BAT0/state which gave result as present: yes capacity state: ok charging state: charged present rate: 1 mA remaining capacity: 4400 mAh present voltage: 12407 mV then I tried $ acpi -b the result was.. Battery 0: Unknown, 100% when I gave command as $ upower -i /org/freedesktop/UPower/devices/battery_BAT0 the result was.. native-path: /sys/devices/LNXSYSTM:00/device:00/PNP0C0A:00/power_supply/BAT0 model: DELL W7H3N08 serial: 7114 power supply: yes updated: Sat Nov 24 11:25:34 2012 (21 seconds ago) has history: yes has statistics: yes battery present: yes rechargeable: yes state: fully-charged energy: 48.4748 Wh energy-empty: 0 Wh energy-full: 48.4748 Wh energy-full-design: 48.9595 Wh energy-rate: 0.011017 W voltage: 12.408 V percentage: 100% **capacity: 52.9253%** technology: lithium-ion Someone please let me know, what is going wrong with my laptop? How can I get charging with full capacity?

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  • Question about modeling with MVC (the pattern, not the MS stuff / non web)

    - by paul
    I'm working on an application in which I'm looking to employ the MVC pattern, but I've come up against a design decision point I could use some help with. My application is going to deal with the design of state-machines. Currently the MVC model holds information about the machine's states, inputs, outputs, etc. The view is going to show a diagram for the machine, graphically allowing the user to add new states, establish transitions, and put the states in a pleasing arrangement, among other things. I would like to store part of the diagram's state (e.g. the x and y state positions) when the machine information is stored for later retrieval, and am wondering how best to go about structuring the model(s?) for this. It seems like this UI information is more closely related to the view than to the state-machine model, so I was thinking that a secondary model might be in order, but I am reluctant to pursue this route because of the added complexity. Adding this information to the current model doesn't seem the right way to go about it either. This is the my first time using the MVC pattern so I'm still figuring things out. Any input would be appreciated.

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  • How to implement string matching based on a pattern

    - by Vincent Rischmann
    I was asked to build a tool that can identify if a string match a pattern. Example: {1:20} stuff t(x) {a,b,c} would match: 1 stuff tx a 20 stuff t c It is a sort of regex but with a different syntax Parentheses indicate an optional value {1:20} is a interval; I will have to check if the token is a number and if it is between 1 and 20 {a,b,c} is just an enumeration; it can be either a or b or c Right now I implemented this with a regex, and the interval stuff was a pain to do. On my own time I tried implementing some kind of matcher by hand, but it turns out it's not that easy to do. By experimenting I ended up with a function that generates a state table from the pattern and a state machine. It worked well until I tried to implement the optional value, and I got stuck and how to generate the state table. After that I searched how I could do this, and that led me to stuff like LL parser, LALR parser, recursive-descent parser, context-free grammars, etc. I never studied any of this so it's hard to know what is relevant here, but I think this is what I need: A grammar A parser which generates states from the grammar and a pattern A state machine to see if a string match the states So my first question is: Is this right ? And second question, what do you recommend I read/study to be able to implement this ?

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  • How should I structure the implementation of turn-based board game rules?

    - by Setzer22
    I'm trying to create a turn-based strategy game on a tilemap. I'm using design by component so far, but I can't find a nice way to fit components into the part I want to ask. I'm struggling with the "game rules" logic. That is, the code that displays the menu, allows the player to select units, and command them, then tells the unit game objects what to do given the player input. The best way I could thing of handling this was using a big state machine, so everything that could be done in a "turn" is handled by this state machine, and the update code of this state machine does different things depending on the state. However, this approach leads to a large amount of code (anything not model-related) going into a big class. Of course I can subdivide this big class into more classes, but it doesn't feel modular and upgradable enough. I'd like to know of better systems to handle this in order to be able to upgrade the game with new rules without having a monstruous if/else chain (or switch / case, for that matter). Any ideas? What specific design pattern other than MVC should I be using?

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  • Client and Server game update speed

    - by user20686
    I am working on a simple two player networked asteroids game using XNA and the Lidgren networking library. For this set up I have a Lidgren server maintaining what I want to be the true state of the game, and the XNA game is the Lidgren client. The client sends key inputs to the server, and the server process the key inputs against game logic, sending back updates. (This seemed like a better idea then sending local positions to the server.) The client also processes the key inputs on its own, so as to not have any visible lag, and then interpolates between the local position and remote position. Based on what I have been reading this is the correct way to smooth out a networked game. The only thing I don’t get is what value to use as the time deltas. Currently every message the server sends it also sends a delta-time update with it, which is time between the last update. The client then saves this delta time to use for its local position updates, so they can be using roughly the same time deltas to calculate position updates. I know the XNA game update gets called 60 times a second, so I set my server to update the game state at the same speed. This will probably only work as long as the game is working on a fixed time step and will probably cause problems if I want to change that in the future. The server sends updates to clients on another thread, which runs at 10 updates per second to cut down on bandwidth. I do not see noticeable lag in movement and over time if no user input is received the local and remote positions converge on each other as they should. I am also not currently calculating for any latency as I am trying to go one step at a time. So my question is should the XNA client be using its current game time to update the local game state and not being using time deltas sent by the server? If I should be using the clients time delta between updates how do I keep it in-line with how fast the server is updating its game state?

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  • I cannot install wine 1.5 on ubuntu 12.04 x64

    - by user26286
    I tried: $ sudo add-apt-repository ppa:ubuntu-wine/ppa $ sudo apt-get update $ sudo apt-get install wine1.5 result was: $ sudo apt-get install wine1.5 Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: wine1.5 : Depends: wine1.5-i386 (= 1.5.6-0ubuntu1~pulse17) E: Unable to correct problems, you have held broken packages. than I tried: $ sudo dpkg --configure -a $ sudo apt-get install -f result was: $ sudo apt-get install -f Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. after all I tried: $ sudo apt-get build-dep wine1.5 Reading package lists... Done Building dependency tree Reading state information... Done The following packages have unmet dependencies: libgnutls-dev : Depends: libgnutls26 (= 2.12.14-5ubuntu3) but 2.12.19-1 is to be installed Depends: libgnutlsxx27 (= 2.12.14-5ubuntu3) but it is not going to be installed Depends: libgnutls-openssl27 (= 2.12.14-5ubuntu3) but it is not going to be installed E: Build-dependencies for wine1.5 could not be satisfied. also tried: $ sudo apt-get install -y ia32-libs Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: ia32-libs : Depends: ia32-libs-multiarch E: Unable to correct problems, you have held broken packages. Somebody can help me? Thanks.

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  • Using Subdomains for Newly Regional Company

    - by Taylord22
    The company I work for is expanding their business to new territories. I've got a lot of stabilization to do in the region/state where we're one of the most well known companies of our kind. Currently, we have 3 distinct product lines which are currently distinguished by 3 separate URLS. This is affecting the user flow of our site, so we'd like to clean it up before launching our products into the various regions. The business has decided to grow into 5 new states (one state consisting of one county only) — none of which will feature all 3 products. Our homebase state is the only one that will have all 3 products this year. My initial thought was to use subdomains to separate out the regions, that way we could use a canonical tag to stabilize the root domain (which would feature home state content, and support content for all regions), and remove us from potential duplicate content penalization. Our product content will be nearly identical across the regions for the first year. I second guessed myself by thinking that it was perhaps better to use a "[product].root/region" URL instead. And I'm currently stuck by wondering if it was not better to build out subdomains for products and regions...using one modifier or the other as a funnel/branding page into the other. For instance, user lands on "region.root.com" and sees exactly what products we offer in that region. Basically, a tailored landing page. Meanwhile the bulk of the product content would actually live under "product.root.com/region/page". My head is spinning. And while searching for similar questions I also bumped into reference of another tag meant to be used in some similar cases to mine. I feel like there's a lot of risks involved in this subdomain strategy, but I also can't help but see the benefits in the user flow.

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  • How best to construct our test subjects in unit tests?

    - by Liath
    Some of our business logic classes require quite a few dependencies (in our case 7-10). As such when we come to unit test these the creation become quite complex. In most tests these dependencies are often not required (only some dependencies are required for particular methods). As a result unit tests often require a significant number of lines of code to mock up these useless dependencies (which can't be null because of null checks). For example: [Test] public void TestMethodA() { var dependency5 = new Mock<IDependency1>(); dependency5.Setup(x => x. // some setup var sut = new Sut(new Mock<IDependency1>().Object, new Mock<IDependency2>().Object, new Mock<IDependency3>().Object, new Mock<IDependency4>().Object, dependency5); Assert.SomeAssert(sut.MethodA()); } In this example almost half the test is taken up creating dependencies which aren't used. I've investigated an approach where I have a helper method. [Test] public void TestMethodA() { var dependency5 = new Mock<IDependency1>(); dependency5.Setup(x => x. // some setup var sut = CreateSut(null, null, null, null, dependency5); Assert.SomeAssert(sut.MethodA()); } private Sut CreateSut(IDependency1 d1, IDependency2 d2...) { return new Sut(d1 ?? new Mock<IDependency1>().Object, d2 ?? new Mock<IDependency2>().Object, } But these often grow very complicated very quickly. What is the best way to create these BLL classes in test classes to reduce complexity and simplify tests?

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  • Java Program help [migrated]

    - by georgetheevilman
    Okay I have a really annoying error. Its coming from my retainAll method. The problem is that I am outputting 1,3,5 in ints at the end, but I need 1,3,5,7,9. Here is the code below for the MySet and driver classes public class MySetTester { public static void main(String[]args) { MySet<String> strings = new MySet<String>(); strings.add("Hey!"); strings.add("Hey!"); strings.add("Hey!"); strings.add("Hey!"); strings.add("Hey!"); strings.add("Listen!"); strings.add("Listen!"); strings.add("Sorry, I couldn't resist."); strings.add("Sorry, I couldn't resist."); strings.add("(you know you would if you could)"); System.out.println("Testing add:\n"); System.out.println("Your size: " + strings.size() + ", contains(Sorry): " + strings.contains("Sorry, I couldn't resist.")); System.out.println("Exp. size: 4, contains(Sorry): true\n"); MySet<String> moreStrings = new MySet<String>(); moreStrings.add("Sorry, I couldn't resist."); moreStrings.add("(you know you would if you could)"); strings.removeAll(moreStrings); System.out.println("Testing remove and removeAll:\n"); System.out.println("Your size: " + strings.size() + ", contains(Sorry): " + strings.contains("Sorry, I couldn't resist.")); System.out.println("Exp. size: 2, contains(Sorry): false\n"); MySet<Integer> ints = new MySet<Integer>(); for (int i = 0; i < 100; i++) { ints.add(i); } System.out.println("Your size: " + ints.size()); System.out.println("Exp. size: 100\n"); for (int i = 0; i < 100; i += 2) { ints.remove(i); } System.out.println("Your size: " + ints.size()); System.out.println("Exp. size: 50\n"); MySet<Integer> zeroThroughNine = new MySet<Integer>(); for (int i = 0; i < 10; i++) { zeroThroughNine.add(i); } ints.retainAll(zeroThroughNine); System.out.println("ints should now only retain odd numbers" + " 0 through 10\n"); System.out.println("Testing your iterator:\n"); for (Integer i : ints) { System.out.println(i); } System.out.println("\nExpected: \n\n1 \n3 \n5 \n7 \n9\n"); System.out.println("Yours:"); for (String s : strings) { System.out.println(s); } System.out.println("\nExpected: \nHey! \nListen!"); strings.clear(); System.out.println("\nClearing your set...\n"); System.out.println("Your set is empty: " + strings.isEmpty()); System.out.println("Exp. set is empty: true"); } } And here is the main code. But still read the top part because that's where my examples are. import java.util.Set; import java.util.Collection; import java.lang.Iterable; import java.util.Iterator; import java.util.Arrays; import java.lang.reflect.Array; public class MySet implements Set, Iterable { // instance variables - replace the example below with your own private E[] backingArray; private int numElements; /** * Constructor for objects of class MySet */ public MySet() { backingArray=(E[]) new Object[5]; numElements=0; } public boolean add(E e){ for(Object elem:backingArray){ if (elem==null ? e==null : elem.equals(e)){ return false; } } if(numElements==backingArray.length){ E[] newArray=Arrays.copyOf(backingArray,backingArray.length*2); newArray[numElements]=e; numElements=numElements+1; backingArray=newArray; return true; } else{ backingArray[numElements]=e; numElements=numElements+1; return true; } } public boolean addAll(Collection<? extends E> c){ for(E elem:c){ this.add(elem); } return true; } public void clear(){ E[] newArray=(E[])new Object[backingArray.length]; numElements=0; backingArray=newArray; } public boolean equals(Object o){ if(o instanceof Set &&(((Set)o).size()==numElements)){ for(E elem:(Set<E>)o){ if (this.contains(o)==false){ return false; } return true; } } return false; } public boolean contains(Object o){ for(E backingElem:backingArray){ if (o!=null && o.equals(backingElem)){ return true; } } return false; } public boolean containsAll(Collection<?> c){ for(E elem:(Set<E>)c){ if(!(this.contains(elem))){ return false; } } return true; } public int hashCode(){ int sum=0; for(E elem:backingArray){ if(elem!=null){ sum=sum+elem.hashCode(); } } return sum; } public boolean isEmpty(){ if(numElements==0){ return true; } else{ return false; } } public boolean remove(Object o){ int i=0; for(Object elem:backingArray){ if(o!=null && o.equals(elem)){ backingArray[i]=null; numElements=numElements-1; E[] newArray=Arrays.copyOf(backingArray,backingArray.length-1); return true; } i=i+1; } return false; } public boolean removeAll(Collection<?> c){ for(Object elem:c){ this.remove(elem); } return true; } public boolean retainAll(Collection<?> c){ MySet<E> removalArray=new MySet<E>(); for(E arrayElem:backingArray){ if(arrayElem!= null && !(c.contains(arrayElem))){ this.remove(arrayElem); } } return false; } public int size(){ return numElements; } public <T> T[] toArray(T[] a) throws ArrayStoreException,NullPointerException{ for(int i=0;i<numElements;i++){ a[i]=(T)backingArray[i]; } for(int j=numElements;j<a.length;j++){ a[j]=null; } return a; } public Object[] toArray(){ Object[] newArray=new Object[numElements]; for(int i=0;i<numElements;i++){ newArray[i]=backingArray[i]; } return newArray; } public Iterator<E> iterator(){ setIterator iterator=new setIterator(); return iterator; } private class setIterator implements Iterator<E>{ private int currIndex; private E lastElement; public setIterator(){ currIndex=0; lastElement=null; } public boolean hasNext(){ while(currIndex<=numElements && backingArray[currIndex]==null){ currIndex=currIndex+1; } if (currIndex<=numElements){ return true; } return false; } public E next(){ E element=backingArray[currIndex]; currIndex=currIndex+1; lastElement=element; return element; } public void remove() throws UnsupportedOperationException,IllegalStateException{ if(lastElement!=null){ MySet.this.remove((Object)lastElement); numElements=numElements-1; } else{ throw new IllegalStateException(); } } } } I've been able to reduce the problems, but otherwise this thing is still causing problems.

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  • What are good design practices when working with Entity Framework

    - by AD
    This will apply mostly for an asp.net application where the data is not accessed via soa. Meaning that you get access to the objects loaded from the framework, not Transfer Objects, although some recommendation still apply. This is a community post, so please add to it as you see fit. Applies to: Entity Framework 1.0 shipped with Visual Studio 2008 sp1. Why pick EF in the first place? Considering it is a young technology with plenty of problems (see below), it may be a hard sell to get on the EF bandwagon for your project. However, it is the technology Microsoft is pushing (at the expense of Linq2Sql, which is a subset of EF). In addition, you may not be satisfied with NHibernate or other solutions out there. Whatever the reasons, there are people out there (including me) working with EF and life is not bad.make you think. EF and inheritance The first big subject is inheritance. EF does support mapping for inherited classes that are persisted in 2 ways: table per class and table the hierarchy. The modeling is easy and there are no programming issues with that part. (The following applies to table per class model as I don't have experience with table per hierarchy, which is, anyway, limited.) The real problem comes when you are trying to run queries that include one or many objects that are part of an inheritance tree: the generated sql is incredibly awful, takes a long time to get parsed by the EF and takes a long time to execute as well. This is a real show stopper. Enough that EF should probably not be used with inheritance or as little as possible. Here is an example of how bad it was. My EF model had ~30 classes, ~10 of which were part of an inheritance tree. On running a query to get one item from the Base class, something as simple as Base.Get(id), the generated SQL was over 50,000 characters. Then when you are trying to return some Associations, it degenerates even more, going as far as throwing SQL exceptions about not being able to query more than 256 tables at once. Ok, this is bad, EF concept is to allow you to create your object structure without (or with as little as possible) consideration on the actual database implementation of your table. It completely fails at this. So, recommendations? Avoid inheritance if you can, the performance will be so much better. Use it sparingly where you have to. In my opinion, this makes EF a glorified sql-generation tool for querying, but there are still advantages to using it. And ways to implement mechanism that are similar to inheritance. Bypassing inheritance with Interfaces First thing to know with trying to get some kind of inheritance going with EF is that you cannot assign a non-EF-modeled class a base class. Don't even try it, it will get overwritten by the modeler. So what to do? You can use interfaces to enforce that classes implement some functionality. For example here is a IEntity interface that allow you to define Associations between EF entities where you don't know at design time what the type of the entity would be. public enum EntityTypes{ Unknown = -1, Dog = 0, Cat } public interface IEntity { int EntityID { get; } string Name { get; } Type EntityType { get; } } public partial class Dog : IEntity { // implement EntityID and Name which could actually be fields // from your EF model Type EntityType{ get{ return EntityTypes.Dog; } } } Using this IEntity, you can then work with undefined associations in other classes // lets take a class that you defined in your model. // that class has a mapping to the columns: PetID, PetType public partial class Person { public IEntity GetPet() { return IEntityController.Get(PetID,PetType); } } which makes use of some extension functions: public class IEntityController { static public IEntity Get(int id, EntityTypes type) { switch (type) { case EntityTypes.Dog: return Dog.Get(id); case EntityTypes.Cat: return Cat.Get(id); default: throw new Exception("Invalid EntityType"); } } } Not as neat as having plain inheritance, particularly considering you have to store the PetType in an extra database field, but considering the performance gains, I would not look back. It also cannot model one-to-many, many-to-many relationship, but with creative uses of 'Union' it could be made to work. Finally, it creates the side effet of loading data in a property/function of the object, which you need to be careful about. Using a clear naming convention like GetXYZ() helps in that regards. Compiled Queries Entity Framework performance is not as good as direct database access with ADO (obviously) or Linq2SQL. There are ways to improve it however, one of which is compiling your queries. The performance of a compiled query is similar to Linq2Sql. What is a compiled query? It is simply a query for which you tell the framework to keep the parsed tree in memory so it doesn't need to be regenerated the next time you run it. So the next run, you will save the time it takes to parse the tree. Do not discount that as it is a very costly operation that gets even worse with more complex queries. There are 2 ways to compile a query: creating an ObjectQuery with EntitySQL and using CompiledQuery.Compile() function. (Note that by using an EntityDataSource in your page, you will in fact be using ObjectQuery with EntitySQL, so that gets compiled and cached). An aside here in case you don't know what EntitySQL is. It is a string-based way of writing queries against the EF. Here is an example: "select value dog from Entities.DogSet as dog where dog.ID = @ID". The syntax is pretty similar to SQL syntax. You can also do pretty complex object manipulation, which is well explained [here][1]. Ok, so here is how to do it using ObjectQuery< string query = "select value dog " + "from Entities.DogSet as dog " + "where dog.ID = @ID"; ObjectQuery<Dog> oQuery = new ObjectQuery<Dog>(query, EntityContext.Instance)); oQuery.Parameters.Add(new ObjectParameter("ID", id)); oQuery.EnablePlanCaching = true; return oQuery.FirstOrDefault(); The first time you run this query, the framework will generate the expression tree and keep it in memory. So the next time it gets executed, you will save on that costly step. In that example EnablePlanCaching = true, which is unnecessary since that is the default option. The other way to compile a query for later use is the CompiledQuery.Compile method. This uses a delegate: static readonly Func<Entities, int, Dog> query_GetDog = CompiledQuery.Compile<Entities, int, Dog>((ctx, id) => ctx.DogSet.FirstOrDefault(it => it.ID == id)); or using linq static readonly Func<Entities, int, Dog> query_GetDog = CompiledQuery.Compile<Entities, int, Dog>((ctx, id) => (from dog in ctx.DogSet where dog.ID == id select dog).FirstOrDefault()); to call the query: query_GetDog.Invoke( YourContext, id ); The advantage of CompiledQuery is that the syntax of your query is checked at compile time, where as EntitySQL is not. However, there are other consideration... Includes Lets say you want to have the data for the dog owner to be returned by the query to avoid making 2 calls to the database. Easy to do, right? EntitySQL string query = "select value dog " + "from Entities.DogSet as dog " + "where dog.ID = @ID"; ObjectQuery<Dog> oQuery = new ObjectQuery<Dog>(query, EntityContext.Instance)).Include("Owner"); oQuery.Parameters.Add(new ObjectParameter("ID", id)); oQuery.EnablePlanCaching = true; return oQuery.FirstOrDefault(); CompiledQuery static readonly Func<Entities, int, Dog> query_GetDog = CompiledQuery.Compile<Entities, int, Dog>((ctx, id) => (from dog in ctx.DogSet.Include("Owner") where dog.ID == id select dog).FirstOrDefault()); Now, what if you want to have the Include parametrized? What I mean is that you want to have a single Get() function that is called from different pages that care about different relationships for the dog. One cares about the Owner, another about his FavoriteFood, another about his FavotireToy and so on. Basicly, you want to tell the query which associations to load. It is easy to do with EntitySQL public Dog Get(int id, string include) { string query = "select value dog " + "from Entities.DogSet as dog " + "where dog.ID = @ID"; ObjectQuery<Dog> oQuery = new ObjectQuery<Dog>(query, EntityContext.Instance)) .IncludeMany(include); oQuery.Parameters.Add(new ObjectParameter("ID", id)); oQuery.EnablePlanCaching = true; return oQuery.FirstOrDefault(); } The include simply uses the passed string. Easy enough. Note that it is possible to improve on the Include(string) function (that accepts only a single path) with an IncludeMany(string) that will let you pass a string of comma-separated associations to load. Look further in the extension section for this function. If we try to do it with CompiledQuery however, we run into numerous problems: The obvious static readonly Func<Entities, int, string, Dog> query_GetDog = CompiledQuery.Compile<Entities, int, string, Dog>((ctx, id, include) => (from dog in ctx.DogSet.Include(include) where dog.ID == id select dog).FirstOrDefault()); will choke when called with: query_GetDog.Invoke( YourContext, id, "Owner,FavoriteFood" ); Because, as mentionned above, Include() only wants to see a single path in the string and here we are giving it 2: "Owner" and "FavoriteFood" (which is not to be confused with "Owner.FavoriteFood"!). Then, let's use IncludeMany(), which is an extension function static readonly Func<Entities, int, string, Dog> query_GetDog = CompiledQuery.Compile<Entities, int, string, Dog>((ctx, id, include) => (from dog in ctx.DogSet.IncludeMany(include) where dog.ID == id select dog).FirstOrDefault()); Wrong again, this time it is because the EF cannot parse IncludeMany because it is not part of the functions that is recognizes: it is an extension. Ok, so you want to pass an arbitrary number of paths to your function and Includes() only takes a single one. What to do? You could decide that you will never ever need more than, say 20 Includes, and pass each separated strings in a struct to CompiledQuery. But now the query looks like this: from dog in ctx.DogSet.Include(include1).Include(include2).Include(include3) .Include(include4).Include(include5).Include(include6) .[...].Include(include19).Include(include20) where dog.ID == id select dog which is awful as well. Ok, then, but wait a minute. Can't we return an ObjectQuery< with CompiledQuery? Then set the includes on that? Well, that what I would have thought so as well: static readonly Func<Entities, int, ObjectQuery<Dog>> query_GetDog = CompiledQuery.Compile<Entities, int, string, ObjectQuery<Dog>>((ctx, id) => (ObjectQuery<Dog>)(from dog in ctx.DogSet where dog.ID == id select dog)); public Dog GetDog( int id, string include ) { ObjectQuery<Dog> oQuery = query_GetDog(id); oQuery = oQuery.IncludeMany(include); return oQuery.FirstOrDefault; } That should have worked, except that when you call IncludeMany (or Include, Where, OrderBy...) you invalidate the cached compiled query because it is an entirely new one now! So, the expression tree needs to be reparsed and you get that performance hit again. So what is the solution? You simply cannot use CompiledQueries with parametrized Includes. Use EntitySQL instead. This doesn't mean that there aren't uses for CompiledQueries. It is great for localized queries that will always be called in the same context. Ideally CompiledQuery should always be used because the syntax is checked at compile time, but due to limitation, that's not possible. An example of use would be: you may want to have a page that queries which two dogs have the same favorite food, which is a bit narrow for a BusinessLayer function, so you put it in your page and know exactly what type of includes are required. Passing more than 3 parameters to a CompiledQuery Func is limited to 5 parameters, of which the last one is the return type and the first one is your Entities object from the model. So that leaves you with 3 parameters. A pitance, but it can be improved on very easily. public struct MyParams { public string param1; public int param2; public DateTime param3; } static readonly Func<Entities, MyParams, IEnumerable<Dog>> query_GetDog = CompiledQuery.Compile<Entities, MyParams, IEnumerable<Dog>>((ctx, myParams) => from dog in ctx.DogSet where dog.Age == myParams.param2 && dog.Name == myParams.param1 and dog.BirthDate > myParams.param3 select dog); public List<Dog> GetSomeDogs( int age, string Name, DateTime birthDate ) { MyParams myParams = new MyParams(); myParams.param1 = name; myParams.param2 = age; myParams.param3 = birthDate; return query_GetDog(YourContext,myParams).ToList(); } Return Types (this does not apply to EntitySQL queries as they aren't compiled at the same time during execution as the CompiledQuery method) Working with Linq, you usually don't force the execution of the query until the very last moment, in case some other functions downstream wants to change the query in some way: static readonly Func<Entities, int, string, IEnumerable<Dog>> query_GetDog = CompiledQuery.Compile<Entities, int, string, IEnumerable<Dog>>((ctx, age, name) => from dog in ctx.DogSet where dog.Age == age && dog.Name == name select dog); public IEnumerable<Dog> GetSomeDogs( int age, string name ) { return query_GetDog(YourContext,age,name); } public void DataBindStuff() { IEnumerable<Dog> dogs = GetSomeDogs(4,"Bud"); // but I want the dogs ordered by BirthDate gridView.DataSource = dogs.OrderBy( it => it.BirthDate ); } What is going to happen here? By still playing with the original ObjectQuery (that is the actual return type of the Linq statement, which implements IEnumerable), it will invalidate the compiled query and be force to re-parse. So, the rule of thumb is to return a List< of objects instead. static readonly Func<Entities, int, string, IEnumerable<Dog>> query_GetDog = CompiledQuery.Compile<Entities, int, string, IEnumerable<Dog>>((ctx, age, name) => from dog in ctx.DogSet where dog.Age == age && dog.Name == name select dog); public List<Dog> GetSomeDogs( int age, string name ) { return query_GetDog(YourContext,age,name).ToList(); //<== change here } public void DataBindStuff() { List<Dog> dogs = GetSomeDogs(4,"Bud"); // but I want the dogs ordered by BirthDate gridView.DataSource = dogs.OrderBy( it => it.BirthDate ); } When you call ToList(), the query gets executed as per the compiled query and then, later, the OrderBy is executed against the objects in memory. It may be a little bit slower, but I'm not even sure. One sure thing is that you have no worries about mis-handling the ObjectQuery and invalidating the compiled query plan. Once again, that is not a blanket statement. ToList() is a defensive programming trick, but if you have a valid reason not to use ToList(), go ahead. There are many cases in which you would want to refine the query before executing it. Performance What is the performance impact of compiling a query? It can actually be fairly large. A rule of thumb is that compiling and caching the query for reuse takes at least double the time of simply executing it without caching. For complex queries (read inherirante), I have seen upwards to 10 seconds. So, the first time a pre-compiled query gets called, you get a performance hit. After that first hit, performance is noticeably better than the same non-pre-compiled query. Practically the same as Linq2Sql When you load a page with pre-compiled queries the first time you will get a hit. It will load in maybe 5-15 seconds (obviously more than one pre-compiled queries will end up being called), while subsequent loads will take less than 300ms. Dramatic difference, and it is up to you to decide if it is ok for your first user to take a hit or you want a script to call your pages to force a compilation of the queries. Can this query be cached? { Dog dog = from dog in YourContext.DogSet where dog.ID == id select dog; } No, ad-hoc Linq queries are not cached and you will incur the cost of generating the tree every single time you call it. Parametrized Queries Most search capabilities involve heavily parametrized queries. There are even libraries available that will let you build a parametrized query out of lamba expressions. The problem is that you cannot use pre-compiled queries with those. One way around that is to map out all the possible criteria in the query and flag which one you want to use: public struct MyParams { public string name; public bool checkName; public int age; public bool checkAge; } static readonly Func<Entities, MyParams, IEnumerable<Dog>> query_GetDog = CompiledQuery.Compile<Entities, MyParams, IEnumerable<Dog>>((ctx, myParams) => from dog in ctx.DogSet where (myParams.checkAge == true && dog.Age == myParams.age) && (myParams.checkName == true && dog.Name == myParams.name ) select dog); protected List<Dog> GetSomeDogs() { MyParams myParams = new MyParams(); myParams.name = "Bud"; myParams.checkName = true; myParams.age = 0; myParams.checkAge = false; return query_GetDog(YourContext,myParams).ToList(); } The advantage here is that you get all the benifits of a pre-compiled quert. The disadvantages are that you most likely will end up with a where clause that is pretty difficult to maintain, that you will incur a bigger penalty for pre-compiling the query and that each query you run is not as efficient as it could be (particularly with joins thrown in). Another way is to build an EntitySQL query piece by piece, like we all did with SQL. protected List<Dod> GetSomeDogs( string name, int age) { string query = "select value dog from Entities.DogSet where 1 = 1 "; if( !String.IsNullOrEmpty(name) ) query = query + " and dog.Name == @Name "; if( age > 0 ) query = query + " and dog.Age == @Age "; ObjectQuery<Dog> oQuery = new ObjectQuery<Dog>( query, YourContext ); if( !String.IsNullOrEmpty(name) ) oQuery.Parameters.Add( new ObjectParameter( "Name", name ) ); if( age > 0 ) oQuery.Parameters.Add( new ObjectParameter( "Age", age ) ); return oQuery.ToList(); } Here the problems are: - there is no syntax checking during compilation - each different combination of parameters generate a different query which will need to be pre-compiled when it is first run. In this case, there are only 4 different possible queries (no params, age-only, name-only and both params), but you can see that there can be way more with a normal world search. - Noone likes to concatenate strings! Another option is to query a large subset of the data and then narrow it down in memory. This is particularly useful if you are working with a definite subset of the data, like all the dogs in a city. You know there are a lot but you also know there aren't that many... so your CityDog search page can load all the dogs for the city in memory, which is a single pre-compiled query and then refine the results protected List<Dod> GetSomeDogs( string name, int age, string city) { string query = "select value dog from Entities.DogSet where dog.Owner.Address.City == @City "; ObjectQuery<Dog> oQuery = new ObjectQuery<Dog>( query, YourContext ); oQuery.Parameters.Add( new ObjectParameter( "City", city ) ); List<Dog> dogs = oQuery.ToList(); if( !String.IsNullOrEmpty(name) ) dogs = dogs.Where( it => it.Name == name ); if( age > 0 ) dogs = dogs.Where( it => it.Age == age ); return dogs; } It is particularly useful when you start displaying all the data then allow for filtering. Problems: - Could lead to serious data transfer if you are not careful about your subset. - You can only filter on the data that you returned. It means that if you don't return the Dog.Owner association, you will not be able to filter on the Dog.Owner.Name So what is the best solution? There isn't any. You need to pick the solution that works best for you and your problem: - Use lambda-based query building when you don't care about pre-compiling your queries. - Use fully-defined pre-compiled Linq query when your object structure is not too complex. - Use EntitySQL/string concatenation when the structure could be complex and when the possible number of different resulting queries are small (which means fewer pre-compilation hits). - Use in-memory filtering when you are working with a smallish subset of the data or when you had to fetch all of the data on the data at first anyway (if the performance is fine with all the data, then filtering in memory will not cause any time to be spent in the db). Singleton access The best way to deal with your context and entities accross all your pages is to use the singleton pattern: public sealed class YourContext { private const string instanceKey = "On3GoModelKey"; YourContext(){} public static YourEntities Instance { get { HttpContext context = HttpContext.Current; if( context == null ) return Nested.instance; if (context.Items[instanceKey] == null) { On3GoEntities entity = new On3GoEntities(); context.Items[instanceKey] = entity; } return (YourEntities)context.Items[instanceKey]; } } class Nested { // Explicit static constructor to tell C# compiler // not to mark type as beforefieldinit static Nested() { } internal static readonly YourEntities instance = new YourEntities(); } } NoTracking, is it worth it? When executing a query, you can tell the framework to track the objects it will return or not. What does it mean? With tracking enabled (the default option), the framework will track what is going on with the object (has it been modified? Created? Deleted?) and will also link objects together, when further queries are made from the database, which is what is of interest here. For example, lets assume that Dog with ID == 2 has an owner which ID == 10. Dog dog = (from dog in YourContext.DogSet where dog.ID == 2 select dog).FirstOrDefault(); //dog.OwnerReference.IsLoaded == false; Person owner = (from o in YourContext.PersonSet where o.ID == 10 select dog).FirstOrDefault(); //dog.OwnerReference.IsLoaded == true; If we were to do the same with no tracking, the result would be different. ObjectQuery<Dog> oDogQuery = (ObjectQuery<Dog>) (from dog in YourContext.DogSet where dog.ID == 2 select dog); oDogQuery.MergeOption = MergeOption.NoTracking; Dog dog = oDogQuery.FirstOrDefault(); //dog.OwnerReference.IsLoaded == false; ObjectQuery<Person> oPersonQuery = (ObjectQuery<Person>) (from o in YourContext.PersonSet where o.ID == 10 select o); oPersonQuery.MergeOption = MergeOption.NoTracking; Owner owner = oPersonQuery.FirstOrDefault(); //dog.OwnerReference.IsLoaded == false; Tracking is very useful and in a perfect world without performance issue, it would always be on. But in this world, there is a price for it, in terms of performance. So, should you use NoTracking to speed things up? It depends on what you are planning to use the data for. Is there any chance that the data your query with NoTracking can be used to make update/insert/delete in the database? If so, don't use NoTracking because associations are not tracked and will causes exceptions to be thrown. In a page where there are absolutly no updates to the database, you can use NoTracking. Mixing tracking and NoTracking is possible, but it requires you to be extra careful with updates/inserts/deletes. The problem is that if you mix then you risk having the framework trying to Attach() a NoTracking object to the context where another copy of the same object exist with tracking on. Basicly, what I am saying is that Dog dog1 = (from dog in YourContext.DogSet where dog.ID == 2).FirstOrDefault(); ObjectQuery<Dog> oDogQuery = (ObjectQuery<Dog>) (from dog in YourContext.DogSet where dog.ID == 2 select dog); oDogQuery.MergeOption = MergeOption.NoTracking; Dog dog2 = oDogQuery.FirstOrDefault(); dog1 and dog2 are 2 different objects, one tracked and one not. Using the detached object in an update/insert will force an Attach() that will say "Wait a minute, I do already have an object here with the same database key. Fail". And when you Attach() one object, all of its hierarchy gets attached as well, causing problems everywhere. Be extra careful. How much faster is it with NoTracking It depends on the queries. Some are much more succeptible to tracking than other. I don't have a fast an easy rule for it, but it helps. So I should use NoTracking everywhere then? Not exactly. There are some advantages to tracking object. The first one is that the object is cached, so subsequent call for that object will not hit the database. That cache is only valid for the lifetime of the YourEntities object, which, if you use the singleton code above, is the same as the page lifetime. One page request == one YourEntity object. So for multiple calls for the same object, it will load only once per page request. (Other caching mechanism could extend that). What happens when you are using NoTracking and try to load the same object multiple times? The database will be queried each time, so there is an impact there. How often do/should you call for the same object during a single page request? As little as possible of course, but it does happens. Also remember the piece above about having the associations connected automatically for your? You don't have that with NoTracking, so if you load your data in multiple batches, you will not have a link to between them: ObjectQuery<Dog> oDogQuery = (ObjectQuery<Dog>)(from dog in YourContext.DogSet select dog); oDogQuery.MergeOption = MergeOption.NoTracking; List<Dog> dogs = oDogQuery.ToList(); ObjectQuery<Person> oPersonQuery = (ObjectQuery<Person>)(from o in YourContext.PersonSet select o); oPersonQuery.MergeOption = MergeOption.NoTracking; List<Person> owners = oPersonQuery.ToList(); In this case, no dog will have its .Owner property set. Some things to keep in mind when you are trying to optimize the performance. No lazy loading, what am I to do? This can be seen as a blessing in disguise. Of course it is annoying to load everything manually. However, it decreases the number of calls to the db and forces you to think about when you should load data. The more you can load in one database call the better. That was always true, but it is enforced now with this 'feature' of EF. Of course, you can call if( !ObjectReference.IsLoaded ) ObjectReference.Load(); if you want to, but a better practice is to force the framework to load the objects you know you will need in one shot. This is where the discussion about parametrized Includes begins to make sense. Lets say you have you Dog object public class Dog { public Dog Get(int id) { return YourContext.DogSet.FirstOrDefault(it => it.ID == id ); } } This is the type of function you work with all the time. It gets called from all over the place and once you have that Dog object, you will do very different things to it in different functions. First, it should be pre-compiled, because you will call that very often. Second, each different pages will want to have access to a different subset of the Dog data. Some will want the Owner, some the FavoriteToy, etc. Of course, you could call Load() for each reference you need anytime you need one. But that will generate a call to the database each time. Bad idea. So instead, each page will ask for the data it wants to see when it first request for the Dog object: static public Dog Get(int id) { return GetDog(entity,"");} static public Dog Get(int id, string includePath) { string query = "select value o " + " from YourEntities.DogSet as o " +

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  • Data from 6 ArrayLists into a single JTable - Java Swing

    - by Splunk
    I have created a JTable which is populated by various arraylists which get their data from a text list using a "~" to split. The issue I am having is that the table is displaying all data from the list on a single row. For example: Column1 Column2 Column2 Column2 Column3 Column4 1,2,3,4,5 1,2,3,4,5 1,2,3,4,5 1,2,3,4,5 1,2,3,4,5 1,2,3,4,5 When I want it to display Column1 Column2 Column2 Column2 Column3 Column4 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 You get the idea. From previous advice, I think the issue may be looping, but I am not sure. Any advice would be great. The code is below: private void table(){ String[] colName = { "Course", "Examiner", "Moderator", "Semester Available ", "Associated Programs", "Associated Majors"}; DefaultTableModel model = new DefaultTableModel(colName,0); for(Object item : courseList){ Object[] row = new Object[6]; // String[] row = new String[6]; row[0] = fileManage.getCourseList(); row[1] = fileManage.getNameList(); row[2] = fileManage.getModeratorList(); row[3] = fileManage.getSemesterList(); row[4] = fileManage.getProgramList(); row[5] = fileManage.getMajorList(); model.addRow(row); textArea = new JTable(model); } This is the class that has the arraylists: import java.io.File; import java.io.FileNotFoundException; import java.util.ArrayList; import java.util.Collections; import java.util.HashSet; import java.util.Scanner; public class FileIOManagement { private ArrayList<String> nameList = new ArrayList<String>(); private ArrayList<String> courseList = new ArrayList<String>(); private ArrayList<String> semesterList = new ArrayList<String>(); private ArrayList<String> moderatorList = new ArrayList<String>(); private ArrayList<String> programList = new ArrayList<String>(); private ArrayList<String> majorList = new ArrayList<String>(); public ArrayList<String> getNameList(){ return this.nameList; } public ArrayList<String> getCourseList(){ return this.courseList; } public ArrayList<String> getSemesterList(){ return this.semesterList; } public ArrayList<String> getModeratorList(){ return this.moderatorList; } public ArrayList<String> getProgramList(){ return this.programList; } public ArrayList<String> getMajorList(){ return this.majorList; } public void setNameList(ArrayList<String> nameList){ this.nameList = nameList; } public void setCourseList(ArrayList<String> courseList){ this.courseList = courseList; } public void setSemesterList(ArrayList<String> semesterList){ this.semesterList = semesterList; } public void setModeratorList(ArrayList<String> moderatorList){ this.moderatorList = moderatorList; } public void setProgramList(ArrayList<String> programList){ this.programList = programList; } public void setMajorList(ArrayList<String> majorList){ this.majorList = majorList; } public FileIOManagement(){ setNameList(new ArrayList<String>()); setCourseList(new ArrayList<String>()); setSemesterList(new ArrayList<String>()); setModeratorList(new ArrayList<String>()); setProgramList(new ArrayList<String>()); setMajorList(new ArrayList<String>()); readTextFile(); getNameList(); getCourseList(); } private void readTextFile(){ try{ Scanner scan = new Scanner(new File("Course.txt")); while(scan.hasNextLine()){ String line = scan.nextLine(); String[] tokens = line.split("~"); String course = tokens[0].trim(); String examiner = tokens[1].trim(); String moderator = tokens[2].trim(); String semester = tokens[3].trim(); String program = tokens[4].trim(); String major = tokens[5].trim(); courseList.add(course); semesterList.add(semester); nameList.add(examiner); moderatorList.add(moderator); programList.add(program); majorList.add(major); HashSet hs = new HashSet(); hs.addAll(nameList); nameList.clear(); nameList.addAll(hs); Collections.sort(nameList); } scan.close(); } catch (FileNotFoundException e){ e.printStackTrace(); } } } This is the class where I need to have the JTable: import java.awt.*; import javax.swing.*; import java.io.*; import javax.swing.border.EmptyBorder; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.util.ArrayList; import javax.swing.table.DefaultTableModel; public class AllDataGUI extends JFrame{ private JButton saveCloseBtn = new JButton("Save Changes and Close"); private JButton closeButton = new JButton("Exit Without Saving"); private JFrame frame=new JFrame("Viewing All Program Details"); private final FileIOManagement fileManage = new FileIOManagement(); private ArrayList<String> nameList = new ArrayList(); private ArrayList<String> courseList = new ArrayList(); private ArrayList<String> semesterList = new ArrayList(); private ArrayList<String> moderatorList = new ArrayList(); private ArrayList<String> majorList = new ArrayList(); private ArrayList<String> programList = new ArrayList(); private JTable textArea; public ArrayList<String> getNameList(){ return this.nameList; } public ArrayList<String> getCourseList(){ return this.courseList; } public ArrayList<String> getSemesterList(){ return this.semesterList; } public ArrayList<String> getModeratorList(){ return this.moderatorList; } public ArrayList<String> getProgramList(){ return this.programList; } public ArrayList<String> getMajorList(){ return this.majorList; } public void setNameList(ArrayList<String> nameList){ this.nameList = nameList; } public void setCourseList(ArrayList<String> courseList){ this.courseList = courseList; } public void setSemesterList(ArrayList<String> semesterList){ this.semesterList = semesterList; } public void setModeratorList(ArrayList<String> moderatorList){ this.moderatorList = moderatorList; } public void setProgramList(ArrayList<String> programList){ this.programList = programList; } public void setMajorList(ArrayList<String> majorList){ this.majorList = majorList; } public AllDataGUI(){ getData(); table(); panels(); } public Object getValueAt(int rowIndex, int columnIndex) { String[] token = nameList.get(rowIndex).split(","); return token[columnIndex]; } private void table(){ String[] colName = { "Course", "Examiner", "Moderator", "Semester Available ", "Associated Programs", "Associated Majors"}; DefaultTableModel model = new DefaultTableModel(colName,0); for(Object item : courseList){ Object[] row = new Object[6]; // String[] row = new String[6]; row[0] = fileManage.getCourseList(); row[1] = fileManage.getNameList(); row[2] = fileManage.getModeratorList(); row[3] = fileManage.getSemesterList(); row[4] = fileManage.getProgramList(); row[5] = fileManage.getMajorList(); model.addRow(row); textArea = new JTable(model); // String END_OF_LINE = ","; // // String[] colName = { "Course", "Examiner", "Moderator", "Semester Available ", "Associated Programs", "Associated Majors"}; //// textArea.getTableHeader().setBackground(Color.WHITE); //// textArea.getTableHeader().setForeground(Color.BLUE); // // Font Tablefont = new Font("Details", Font.BOLD, 12); // // textArea.getTableHeader().setFont(Tablefont); // Object[][] object = new Object[100][100]; // int i = 0; // if (fileManage.size() != 0) { // for (fileManage book : fileManage) { // object[i][0] = fileManage.getCourseList(); // object[i][1] = fileManage.getNameList(); // object[i][2] = fileManage.getModeratorList(); // object[i][3] = fileManage.getSemesterList(); // object[i][4] = fileManage.getProgramList(); // object[i][5] = fileManage.getMajorList(); // // textArea = new JTable(object, colName); // } // } } } public void getData(){ nameList = fileManage.getNameList(); courseList = fileManage.getCourseList(); semesterList = fileManage.getSemesterList(); moderatorList = fileManage.getModeratorList(); majorList = fileManage.getMajorList(); programList = fileManage.getProgramList(); // textArea.(write()); } private JButton getCloseButton(){ return closeButton; } private void panels(){ JPanel panel = new JPanel(new GridLayout(1,1)); panel.setBorder(new EmptyBorder(5, 5, 5, 5)); JPanel rightPanel = new JPanel(new GridLayout(15,0,10,10)); rightPanel.setBorder(new EmptyBorder(15, 5, 5, 10)); JScrollPane scrollBarForTextArea=new JScrollPane(textArea,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED); panel.add(scrollBarForTextArea); frame.add(panel); frame.getContentPane().add(rightPanel,BorderLayout.EAST); rightPanel.add(saveCloseBtn); rightPanel.add(closeButton); closeButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { frame.dispose(); } }); saveCloseBtn.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { //saveBtn(); frame.dispose(); } }); frame.setSize(1000, 700); frame.setVisible(true); frame.setLocationRelativeTo(null); } // private void saveBtn(){ // File file = null; // FileWriter out=null; // try { // file = new File("Course.txt"); // out = new FileWriter(file); // out.write(textArea.getText()); // out.close(); // } catch (FileNotFoundException e) { // e.printStackTrace(); // } catch (IOException e) { // e.printStackTrace(); // } // JOptionPane.showMessageDialog(this, "File Successfully Updated"); // // } }

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