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• Ajaxy

  - by Chris Skardon

  Today is the big day, the day I attempt to use Ajax in the app… I’ve never done this (well, tell a lie, I’ve done it in a ‘tutorial’ site, but that was a while ago now), so it’s going to be interesting.. OK, basics first, let’s start with the @Ajax.ActionLink Right, first stab: @Ajax.ActionLink("Click to get latest", "LatestEntry", new AjaxOptions { UpdateTargetId = "ajaxEntrant", InsertionMode = InsertionMode.Replace, HttpMethod = "GET" }) As far as I’m aware, I’m asking to get the ‘LatestEntry’ from the current controller, and in doing so, I will replace the #ajaxEntrant DOM bit with the result. So. I guess I’d better get the result working… To the controller! public PartialResult LatestEntry() { var entrant =_db.Entrants.OrderByDescending(e => e.Id).Single(); return PartialView("_Entrant", entrant); } Pretty simple, just returns the last entry in a PartialView… but! I have yet to make my partial view, so onto that! @model Webby.Entrant <div class="entrant"> <h4>@Model.Name</h4> </div> Again, super simple, (I’m really just testing at this point)… All the code is now there (as far as I know), so F5 and in… And once again, in the traditionally disappointing way of the norm, it doesn’t work, sure… it opens the right view, but it doesn’t replace the #ajaxEntry DOM element, rather it replaces the whole page… The source code (again, as far as I know) looks ok: <a data-ajax="true" data-ajax-method="GET" data-ajax-mode="replace" data-ajax-update="#ajaxEntrants" href="/Entrants/LatestEntrant">Click to get latest</a> Changing the InsertionMode to any of the other modes has the same effect.. It’s not the DOM name either, changing that has the same effect.. i.e. none. It’s not the partial view either, just making that a <p> has (again) no effect… Ahhhhh --- what a schoolboy error… I had neglected (ahem) to actually put the script bit into the calling page (another save from stackoverflow): <script src="@Url.Content("~/Scripts/jquery.unobtrusive-ajax.js")" type="text/javascript"></script> I’ve now stuck that into the _Layout.cshtml view temporarily to aid the development process… :) Onwards and upwards! Chris

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• 0xC0017011 and other error messages - what is the error message text?

  Recently there was a bug raised against BIDS Helper which originated in my Expression Editor control. Thankfully the person that raised it kindly included a screenshot, so I had the error code (HRESULT 0xC0017011) and a stack trace that pointed the finger firmly at my control, but no error message text. The code itself looked fine so I searched on the error code but got no results. I’d expected to get a hit from Books Online with the Integration Services Error and Message Reference topic at the very least, but no joy. There is however a more accurate and definitive reference, namely the header file that defines all these codes dtsmsg.h which you can find at- C:\Program Files (x86)\Microsoft SQL Server\110\SDK\Include\dtsmsg.h Looking the code up in the header file gave me a much more useful error message. //////////////////////////////////////////////////////////////////////////// // The parameter is sensitive // // MessageId: DTS_E_SENSITIVEPARAMVALUENOTALLOWED // // MessageText: // // Accessing value of the parameter variable for the sensitive parameter "%1!s!" is not allowed. Verify that the variable is used properly and that it protects the sensitive information. // #define DTS_E_SENSITIVEPARAMVALUENOTALLOWED ((HRESULT)0xC0017011L) Unfortunately I’d forgotten all about this. By the time I had remembered about it, the person who raised the issue had managed to narrow it down to something to do with having  sensitive parameter. Putting that together with the error message I’d finally found, a quick poke around in the code and I found the new GetSensitiveValue method which seemed to do the trick. The HResult fields are also listed online but it only shows the short error message, and it doesn’t include that all so important HRESULT value itself. So let this be a lesson to you (and me!), if you need to check  SSIS error go straight to the horses mouth - dtsmsg.h. This is particularly true when working with early builds, or CTP releases when we expect the documentation to be a bit behind. There is also a programmatic approach to getting better SSIS error messages. I should to take another look at the error handling in the control, or the way it is hosted in BIDS Helper. I suspect that if I use an implementation of Microsoft.SqlServer.Dts.Runtime.Wrapper.IDTSInfoEvents100 I could catch the error itself and get the full error message text which I could then report back. This would obviously be a better user experience and also make it easier to diagnose any issues like this in the future. See ExprssionEvaluator.cs for an example of this in use in the Expression Editor control.

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• PCF shadow shader math causing artifacts

  - by user2971069

  For a while now I used PCSS for my shadow technique of choice until I discovered a type of percentage closer filtering. This method creates really smooth shadows and with hopes of improving performance, with only a fraction of texture samples, I tried to implement PCF into my shader. This is the relevant code: float c0, c1, c2, c3; float f = blurFactor; float2 coord = ProjectedTexCoords; if (receiverDistance - tex2D(lightSampler, coord + float2(0, 0)).x > 0.0007) c0 = 1; if (receiverDistance - tex2D(lightSampler, coord + float2(f, 0)).x > 0.0007) c1 = 1; if (receiverDistance - tex2D(lightSampler, coord + float2(0, f)).x > 0.0007) c2 = 1; if (receiverDistance - tex2D(lightSampler, coord + float2(f, f)).x > 0.0007) c3 = 1; coord = (coord % f) / f; return 1 - (c0 * (1 - coord.x) * (1 - coord.y) + c1 * coord.x * (1 - coord.y) + c2 * (1 - coord.x) * coord.y + c3 * coord.x * coord.y); This is a very basic implementation. blurFactor is initialized with 1 / LightTextureSize. So the if statements fetch the occlusion values for the four adjacent texels. I now want to weight each value based on the actual position of the texture coordinate. If it's near the bottom-right pixel, that occlusion value should be preferred. The weighting itself is done with a simple bilinear interpolation function, however this function takes a 2d vector in the range [0..1] so I have to convert my texture coordinate to get the distance from my first pixel to the second one in range [0..1]. For that I used the mod operator to get it into [0..f] range and then divided by f. This code makes sense to me, and for specific blurFactors it works, producing really smooth one pixel wide shadows, but not for all blurFactors. Initially blurFactor is (1 / LightTextureSize) to sample the 4 adjacent texels. I now want to increase the blurFactor by factor x to get a smooth interpolation across maybe 4 or so pixels. But that is when weird artifacts show up. Here is an image: Using a 1x on blurFactor produces a good result, 0.5 is as expected not so smooth. 2x however doesn't work at all. I found that only a factor of 1/2^n produces an good result, every other factor produces artifacts. I'm pretty sure the error lies here: coord = (coord % f) / f; Maybe the modulo is not calculated correctly? I have no idea how to fix that. Is it even possible for pixel that are further than 1 pixel away?

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• Adding complexity to remove duplicate code

  - by Phil

  I have several classes that all inherit from a generic base class. The base class contains a collection of several objects of type T. Each child class needs to be able to calculate interpolated values from the collection of objects, but since the child classes use different types, the calculation varies a tiny bit from class to class. So far I have copy/pasted my code from class to class and made minor modifications to each. But now I am trying to remove the duplicated code and replace it with one generic interpolation method in my base class. However that is proving to be very difficult, and all the solutions I have thought of seem way too complex. I am starting to think the DRY principle does not apply as much in this kind of situation, but that sounds like blasphemy. How much complexity is too much when trying to remove code duplication? EDIT: The best solution I can come up with goes something like this: Base Class: protected T GetInterpolated(int frame) { var index = SortedFrames.BinarySearch(frame); if (index >= 0) return Data[index]; index = ~index; if (index == 0) return Data[index]; if (index >= Data.Count) return Data[Data.Count - 1]; return GetInterpolatedItem(frame, Data[index - 1], Data[index]); } protected abstract T GetInterpolatedItem(int frame, T lower, T upper); Child class A: public IGpsCoordinate GetInterpolatedCoord(int frame) { ReadData(); return GetInterpolated(frame); } protected override IGpsCoordinate GetInterpolatedItem(int frame, IGpsCoordinate lower, IGpsCoordinate upper) { double ratio = GetInterpolationRatio(frame, lower.Frame, upper.Frame); var x = GetInterpolatedValue(lower.X, upper.X, ratio); var y = GetInterpolatedValue(lower.Y, upper.Y, ratio); var z = GetInterpolatedValue(lower.Z, upper.Z, ratio); return new GpsCoordinate(frame, x, y, z); } Child class B: public double GetMph(int frame) { ReadData(); return GetInterpolated(frame).MilesPerHour; } protected override ISpeed GetInterpolatedItem(int frame, ISpeed lower, ISpeed upper) { var ratio = GetInterpolationRatio(frame, lower.Frame, upper.Frame); var mph = GetInterpolatedValue(lower.MilesPerHour, upper.MilesPerHour, ratio); return new Speed(frame, mph); }

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• What are the tradeoffs for using 'partial view models'?

  - by Kenny Evitt

  I've become aware of an itch due to some non-DRY code pertaining to view model classes in an (ASP.NET) MVC web application and I'm thinking of scratching my itch by organizing code in various 'partial view model' classes. By partial-view-model, I'm referring to a class like a view model class in an analogous way to how partial views are like views, i.e. a way to encapsulate common info and behavior. To strengthen the 'analogy', and to aid in visually organizing the code in my IDE, I was thinking of naming the partial-view-model classes with a _ prefix, e.g. _ParentItemViewModel. As a slightly more concrete example of why I'm thinking along these lines, imagine that I have a domain-model-entity class ParentItem and the user-friendly descriptive text that identifies these items to users is complex enough that I'd like to encapsulate that code in a method in a _ParentItemViewModel class, for which I can then include an object or a collection of objects of that class in all the view model classes for all the views that need to include a reference to a parent item, e.g. ChildItemViewModel can have a ParentItem property of the _ParentItemViewModel class type, so that in my ChildItemView view, I can use @Model.ParentItem.UserFriendlyDescription as desired, like breadcrumbs, links, etc. Edited 2014-02-06 09:56 -05 As a second example, imagine that I have entity classes SomeKindOfBatch, SomeKindOfBatchDetail, and SomeKindOfBatchDetailEvent, and a view model class and at least one view for each of those entities. Also, the example application covers a lot more than just some-kind-of-batches, so that it wouldn't really be useful or sensible to include info about a specific some-kind-of-batch in all of the project view model classes. But, like the above example, I have some code, say for generating a string for identifying a some-kind-of-batch in a user-friendly way, and I'd like to be able to use that in several views, say as breadcrumb text or text for a link. As a third example, I'll describe another pattern I'm currently using. I have a Contact entity class, but it's a fat class, with dozens of properties, and at least a dozen references to other fat classes. However, a lot of view model classes need properties for referencing a specific contact and most of those need other properties for collections of contacts, e.g. possible contacts to be referenced for some kind of relationship. Most of these view model classes only need a small fraction of all of the available contact info, basically just an ID and some kind of user-friendly description (i.e. a friendly name). It seems to be pretty useful to have a 'partial view model' class for contacts that all of these other view model classes can use. Maybe I'm just misunderstanding 'view model class' – I understand a view model class as always corresponding to a view. But maybe I'm assuming too much.

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• Programmatically updating one update panel elements from another update panel elements

  - by Jalpesh P. Vadgama

  While taking interviews for asp.net candidate I am often asking this question but most peoples are not able to give this answer. So I decided to write a blog post about this. Here is the scenario. There are two update panels in my html code in first update panel there is textbox hello world and another update panel there is a button called btnHelloWorld. Now I want to update textbox text in button click event without post back. But in normal scenario It will not update the textbox text as both are in different update panel. Here is the code for that. <form id="form1" runat="server"> <asp:ScriptManager ID="myScriptManager" runat="server" EnableCdn="true"></asp:ScriptManager> <asp:UpdatePanel ID="firstUpdatePanel" runat="server" UpdateMode="Conditional"> <ContentTemplate> <asp:TextBox ID="txtHelloWorld" runat="server"></asp:TextBox> </ContentTemplate> </asp:UpdatePanel> <asp:UpdatePanel ID="secondUpdatePanel" runat="server" UpdateMode="Conditional"> <ContentTemplate> <asp:Button ID="btnHelloWorld" runat="server" Text="Print Hello World" onclick="btnHelloWorld_Click" /> </ContentTemplate> </asp:UpdatePanel> </form> Here comes magic!!. Lots of people don’t know that update panel are providing the Update method from which we can programmatically update the update panel elements without post back. Below is code for that. protected void btnHelloWorld_Click(object sender, System.EventArgs e) { txtHelloWorld.Text = "Hello World!!!"; firstUpdatePanel.Update(); } That’s it here I have updated the firstUpdatePanel from the code!!!. Hope you liked it.. Stay tuned for more..Happy Programming.. Technorati Tags: UpdatePanel,ASP.NET

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• GUI device for throwing a ball

  - by Fredrik Johansson

  The hero has a ball, which shall be thrown with accuracy in a court on iPhone/iPad. The player is seen from above, in a 2D view. In game play, the player reach is between 1/15 and 1/6 of the height of the iPhone screen. The player will run, and try to outmaneuver his opponent, and then throw the ball at a specific location, which is guarded by the opponent (which is also shown on the screen). The player is controlled by a joystick, and that works ok, but how shall I control the stick? Maybe someone can propose a third control method? I've tried the following two approaches: Joystick: Hero has a reach of 1 meter, and this reach is marked with a semi-opaque circle around the player. The ball can be moved by a joystick. When the joystick is moved south, the ball is moved south within the reach circle. There is a direct coupling with the joystick and the position of the ball. I.e. when the joystick is moved max south, the ball is max south within the player reach. At each touch update the speed is calculated, and the Box2d ball position and ball speed are updated. NB, the ball will never be moved outside the reach as long as the player push the joystick. The ball is thrown by swiping the joystick to make the ball move, and then releasing the joystick. At release, the ball will get a smoothed speed of the joystick. Joystick Problem: The throwing accuracy gets bad, because the joystick can not be that big, and a small movement results in quite a large movement of the ball. If the user does not release before the end of the joystick maximum end point, the ball will stop, and when the user releases the joystick the speed of the ball will be zero. Bad... Touch pad A force is applied to the ball by a sweep on a touchpad. The ball is released when the sweep is ended, or when the ball is moved outside the player reach. As there is no one to one mapping between the swipe and the ball position, the precision can be improved. A large swipe can result in a small ball movement. Touch Pad Problem A touchpad is less intuitive. Users do not seem to know what to do with the touch pad. Some tap the touchpad, and then the ball just falls to the ground. As there is no one-to-one mapping, the ball can be moved outside the reach, and then it will just fall to the ground. It's a bit hard to control the ball, especially if the player also moves.

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• JavaScript: Code Folding

  - by Petr

  Today I would like to mentioned code folding in the new JavaScript editor support, which is available in the continual builds from our server. It's a basic feature, but was mentioned in a comment under the mentioned post. So you can fold comments and every code block between { and }. The current support allows only methods to be folded. The difference is shown below. In the picture on the left side is the current folding and on the right side the new one.   The code folding can be switched off in the Editor Options (Tools main menu -> Options -> Editor category -> General Tab). In this dialog you can also define which folds should be collapsed by default when you open a file. These options more closely fit Java editor needs, but you can see in the next picture how the options are mapped for JavaScript code.  The Method option folds all functions in the code. Other code blogs are fold through the option Tags and Other Code Blogs.  The documentation comments (starts with /**) are fold through Javadoc Comments and when you check Initial Comment, then all comments that start with /* are folded by default.  The new JavaScript editor also supports custom folds. To add your custom fold, type in two special comments as shown in this example: // <editor-fold> Your code goes here... // </editor-fold> You can define the default description of a collapsed fold by adding a "desc" attribute: // <editor-fold desc="This is my super secret genius code."> Your code goes here... // </editor-fold> You can set a fold to be collapsed by default by adding a "defaultstate" attribute: // <editor-fold defaultstate="collapsed"> Your code goes here... // </editor-fold> There is a code template that helps with writing custom fold comments. The abbreviation for the template is fcom. As I wrote the new JS support is available in the continual builds. Go here for more info.

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• Any reliable polygon normal calculation code?

  - by Jenko

  I'm currently calculating the normal vector of a polygon using this code, but for some faces here and there it calculates a wrong normal. I don't really know what's going on or where it fails but its not reliable. Do you have any polygon normal calculation that's tested and found to be reliable? // calculate normal of a polygon using all points var n:int = points.length; var x:Number = 0; var y:Number = 0; var z:Number = 0 // ensure all points above 0 var minx:Number = 0, miny:Number = 0, minz:Number = 0; for (var p:int = 0, pl:int = points.length; p < pl; p++) { var po:_Point3D = points[p] = points[p].clone(); if (po.x < minx) { minx = po.x; } if (po.y < miny) { miny = po.y; } if (po.z < minz) { minz = po.z; } } for (p = 0; p < pl; p++) { po = points[p]; po.x -= minx; po.y -= miny; po.z -= minz; } var cur:int = 1, prev:int = 0, next:int = 2; for (var i:int = 1; i <= n; i++) { // using Newell method x += points[cur].y * (points[next].z - points[prev].z); y += points[cur].z * (points[next].x - points[prev].x); z += points[cur].x * (points[next].y - points[prev].y); cur = (cur+1) % n; next = (next+1) % n; prev = (prev+1) % n; } // length of the normal var length:Number = Math.sqrt(x * x + y * y + z * z); // turn large values into a unit vector if (length != 0){ x = x / length; y = y / length; z = z / length; }else { throw new Error("Cannot calculate normal since triangle has an area of 0"); }

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• What's the best way to create a static utility class in python? Is using metaclasses code smell?

  - by rsimp

  Ok so I need to create a bunch of utility classes in python. Normally I would just use a simple module for this but I need to be able to inherit in order to share common code between them. The common code needs to reference the state of the module using it so simple imports wouldn't work well. I don't like singletons, and classes that use the classmethod decorator do not have proper support for python properties. One pattern I see used a lot is creating an internal python class prefixed with an underscore and creating a single instance which is then explicitly imported or set as the module itself. This is also used by fabric to create a common environment object (fabric.api.env). I've realized another way to accomplish this would be with metaclasses. For example: #util.py class MetaFooBase(type): @property def file_path(cls): raise NotImplementedError def inherited_method(cls): print cls.file_path #foo.py from util import * import env class MetaFoo(MetaFooBase): @property def file_path(cls): return env.base_path + "relative/path" def another_class_method(cls): pass class Foo(object): __metaclass__ = MetaFoo #client.py from foo import Foo file_path = Foo.file_path I like this approach better than the first pattern for a few reasons: First, instantiating Foo would be meaningless as it has no attributes or methods, which insures this class acts like a true single interface utility, unlike the first pattern which relies on the underscore convention to dissuade client code from creating more instances of the internal class. Second, sub-classing MetaFoo in a different module wouldn't be as awkward because I wouldn't be importing a class with an underscore which is inherently going against its private naming convention. Third, this seems to be the closest approximation to a static class that exists in python, as all the meta code applies only to the class and not to its instances. This is shown by the common convention of using cls instead of self in the class methods. As well, the base class inherits from type instead of object which would prevent users from trying to use it as a base for other non-static classes. It's implementation as a static class is also apparent when using it by the naming convention Foo, as opposed to foo, which denotes a static class method is being used. As much as I think this is a good fit, I feel that others might feel its not pythonic because its not a sanctioned use for metaclasses which should be avoided 99% of the time. I also find most python devs tend to shy away from metaclasses which might affect code reuse/maintainability. Is this code considered code smell in the python community? I ask because I'm creating a pypi package, and would like to do everything I can to increase adoption.

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• Help, i cant reference my vars!

  - by SystemNetworks

  I have a sub-class(let's call it sub) and it contains all the function of an object in my game. In my main class(Let's call it main), i connect my sub to main. (Example sub Code: s = new sub(); Then I put my sub function at the update method. Code: s.myFunc(); Becuase in my sub, i have booleans, integers, float and more. The problem is that I don't want to connect my main class to use my main's int, booleans and others. If i connect it, it will have a stack overflow. This is what I put in my sub: Code: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.Input; import org.newdawn.slick.state.StateBasedGame; public class Armory { package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.Input; import org.newdawn.slick.state.StateBasedGame; public class Store { public Integer wood; public Float probePositionX; public Float probePositionY; public Boolean StoreOn; public Boolean darkBought; public Integer money; public Integer darkEnergy; public Integer lifeLeft; public Integer powerLeft; public void darkStores(GameContainer gc, StateBasedGame sbg, GameContainer gc2) { Input input1 = gc.getInput(); //Player need wood to enter(200) If not there will be an error. if(wood>=200) { //Enter Store! if(input1.isKeyDown(Input.KEY_Q)) { //Player must be in this cord! if((probePositionX>393 && probePositionX<555) && (probePositionY< 271 && probePositionY>171)) { //The Store is On StoreOn=true; } } } } } In my main (update function) I put: Code: s.darkBought = darkBought; s.darkEnergy = darkEnergy; s.lifeLeft = lifeLeft; s.money = money; s.powerLeft = powerLeft; s.probePositionX = probePositionX; s.probePositionY = probePositionY; s.StoreOn = StoreOn; s.wood = wood; s.darkStores(gc, sbg, gc); The problem is when I go to the place, and I press q, nothing shows up. It should show another image. Is there anything wrong???

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• SQL SERVER – Fix: Error: 10920 Cannot drop user-defined function. It is being used as a resource governor classifier

  - by pinaldave

  If you have not read my SQL SERVER – Simple Example to Configure Resource Governor – Introduction to Resource Governor yesterday’s detailed primer on Resource Governor, I suggest you go ahead and read it before continuing this article. After reading the article the very first email I received was as follows: “Pinal, I configured resource governor on my development server and it worked fine with tests I ran. After doing some tests, I decided to remove the resource governor and as a first step I disabled it however, I was not able to drop the classification function during the process of the clean up. It was continuously giving me following error. Msg 10920, Level 16, State 1, Line 1 Cannot drop user-defined function myudfname. It is being used as a resource governor classifier. Would you please give me solution?” The original email was really this short and there is no other information. I am glad he has done experiments on development server and not on the production server. Production server must not be the playground of the experiments. I think I have covered the answer of this error in an earlier blog post. If the user disables the Resource Governor it is still not possible to drop the function because it can be enabled again and when enabled it can still use the same function. Here is the simple resolution of the how one can drop the classifier function (do this only if you are not going to use the function). The reason the classifier function can’t be dropped because it is associated with resource governor. Create a new classified function for your resource governor or just assign NULL as described in the following T-SQL Script and you will be able to drop the function without error. ALTER RESOURCE GOVERNOR WITH (CLASSIFIER_FUNCTION = NULL) GO ALTER RESOURCE GOVERNOR DISABLE GO DROP FUNCTION dbo.UDFClassifier GO I am glad that user asked me question instead of doing something radically different, which can leave the server in the unusable state. I am aware of this only method to avoid this error. Is there any better way to achieve the same? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Error Messages, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Oracle????????????????????????~????????????????????

  - by Yusuke.Yamamoto

  RDBMS ???????·????????????????????????????????????????????????????????????????????????? ????????Oracle ?????????????????????????????????? Oracle Database ???????????????????????????????? ????????????????????? ????Oracle???????????????????????????????????????????????????????????????????????????? ?????????????? Oracle Database ???????????????????????? ??????????????????????????????????2????????????? 1. ??????(Query Transformation) Query Transformation ???????SQL??????????????????SQL????????????????????? Query Transformation ???Predicate Transformation ? Common Sub-expression Elimination (CSE), Order-BY Elimination (OBYE), Outer Join Elimination (OJE), Simple View Meging (SVM), Predicate Move around (PM), Complex View Merging (CVM), Sub-query Unnesting (SU), Join Predicate Push Down (JPPD) ???? OR Expansion, Star Transformation (ST) ????????????? ···???????????????????????????????????????????????????? Predicate Transformation ?????? Transitive Predicate Generation ????????????? ?????????????SQL???deptno ? 10 ????????????????????????????? select e.ename, d.loc from emp e, dept d where e.deptno=d.deptno and e.deptno=10; ???????????????emp ??? deptno=10 ??????????????dept ??? d.deptno=10 ??????????????????? emp ?? deptno=10 ????????????????????emp ?? deptno=10 ??????10???????10? dept ????????????dept ??20???????????????????????10?*20?=200?????(??????????·?????????)? ??SQL?? Transitive Predicate Generation ??????SQL????????????????? select e.ename, d.location from emp e, dept d where e.deptno=d.deptno and e.deptno=10 and d.deptno=10; ^^^^^^^^^^^ ??????dept ?????? deptno=10 ??????????????????????????10?*1?=10(dept.deptno ?unique????)?1/20????????????????1/20????????????????10??????????30???????????????Query Transformation ???????????????????????????? ?:??????????? dept ?? 1-row table ??????dept ?? driving ???(Outer Table)??? emp ?? probe ???(Inner Table)????????????1?*10?=10 ????????????????????????????????????????????????????????1/20????????????? ?????? Query Transformation ??????SQL????????????????????????????????? Transformation ??????????????????????????????????? 2. ????·????(Access Path Analysis) Access Path Analysis ??Query Transformation ??SQL????????????(Access Path)?????????(Join Method)?????(Join Order)?????????? ??????????????????(FTS)?ROWID?????????????????????????????·?????(Nested Loop Join)???????(Hash Join)????/?????(Sort Merge Join)????????????????????????????????????????????????????????????????????????? Oracle Database ????????? Query Transformation ???? Logical Optimizer?Access Path Analysis ???? Physical Optimizer ????????? ??????????????????????????????????????????????????????????????????????????????????????????????????? ????????????????????????????????????????????????????? Oracle Database ????????????????????? "Oracle ????????" ?????????? Sustaining Engineering?? ?(??? ???) ???????????????? Sustaining Engineering ????????????????????????Oracle Database ???????????????????????? ?????????????????????Ruby????????????????????????? Oracle????????????????????????! Oracle????????????? Oracle????????????????????????

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• Challenge: Learn One New Thing Today

  - by BuckWoody

  Most of us know that there's a lot to learn. I'm teaching a class this morning, and even on the subject where I'm the "expert" (that word always makes me nervous!) I still have a lot to learn. To learn, sometimes I take a class, read a book, or carve out a large chunk of time so that I can fully grasp the subject. But since I've been working, I really don't have a lot of opportunities to do that. Like you, I'm really busy. So what I've been able to learn is to take just a few moments each day and learn something new about SQL Server. I thought I would share that process here. First, I started with an outline of the product. You can use Books Online, a college class syllabus, a training class outline, or a comprehensive book table of contents. Then I checked off the things I felt I knew a little about. Sure, I'll come back around to those, but I want to be as efficient as I can. I then trolled various checklists to see what I needed to know about the subjects I didn't have checked off. From there (I'm doing all this in a notepad, and then later in OneNote when that came out) I developed a block of text for that subject. Every time I ran across a book, article, web site or recording on that topic I wrote that reference down. Later I went back and quickly looked over those resources and tried to figure out how I could parcel it out - 10 minutes for this one, a free seminar (like the one I'm teaching today - ironic) takes 4 hours, a web site takes an hour to grok, that sort of thing.  Then all I did was figure out how much time each day I'll give to training. Sure, it literally may be ten minutes, but it adds up. One final thing - as I used something I learned, I came back and made notes in that topic. You learn to play the piano not just from a book, but by playing the piano, after all. If you don't use what you learn, you'll lose it. So if you're interested in getting better at SQL Server, and you're willing to do a little work, try out this method. Leave a note here for others to encourage them.  Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Selectively Exposing Functionallity in .Net

  - by David V. Corbin

  Any developer should be aware of the principles of encapsulation, cross-tier isolation, and cross-functional separation of concerns. However, it seems the few take the time to consider the adage of "minimal yet complete"1 when developing the software. Consider the exposure of "business objects" to the user interface. Some common situations occur: Accessing a given element requires a compound set of calls that do not "make sense" to the User Interface. More information than absolutely required is exposed to the user interface It would be much cleaner if a custom interface was provided that exposed exactly (and only) the information that is required by the consumer. Achieving this using conventional techniques would require the creation (and maintenance!) of custom classes to filter and transpose the information into the ideal format. Determining the ROI on this approach can be very difficult to ascertain, and as a result it is often ignored completely. There is another approach, which is largely made practical by virtual of the Action and Func delegates. From a callers point of view, the following two samples can be used interchangeably:     interface ISomeInterface     {         void SampleMethod1(string param);         string SamepleMethod2(string param);     }       class ISomeInterface     {         public Action<string> SampleMethod1 {get; }         public Func<string,string> SamepleMethod2 {get; }     }   The capabilities this simple changes enable are significant (and remember it does not cange the syntax at the call site): The delegates can be initialized to directly call the proper method of any target class. The delegates can be dynamically updated based on the current state. The "interface" can NOT be cast to the concrete class (which often exposes more functionallity). This patterns By limiting the interface to the exact functionallity required, the reduced surface area will typically result in lower development, testing and maintenance costs. We are currently in the process of posting a project on CodePlex which illustrates this (and many other) techniques which have proven helpful in creating robust yet flexible solutions that are highly efficient2 and maintainable. This post will be updated as soon as the project is published. 1) Credit: Scott  Meyers, Effective C++, Addison-Wesley 1992 2) For those who read my previous post on performance it should be noted that the use of delegates is on the same order of magnitude (actually a tiny amount faster) as conventional interfaces.

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• PowerShell - grabbing values out of the registry and running them

  - by Rob Farley

  So I closed an application that runs when Windows starts up, but it doesn’t have a Start Menu entry, and I was trying to find it. Ok, I could’ve run regedit.exe, navigated through the tree and found the list of things that run when Windows starts up, but I thought I’d use PowerShell instead. PowerShell presents the registry as if it’s a volume on a disk, and you can navigate around it using commands like cd and dir. It wasn’t hard to find the folder I knew I was after – tab completion (starting the word and then hitting the Tab key) was a friend here. But unfortunately dir doesn’t list values, only subkeys (which look like folders). PS C:\Windows\system32> dir HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Run PS C:\Windows\system32> Instead, I needed to use Get-Item to fetch the ‘Run’ key, and use its Property property. This listed the values in there for me, as an array of strings (I could work this out using Get-Member). PS C:\Windows\system32> (Get-Item HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Run).Property QuickSet SynTPEnh Zune Launcher PS C:\Windows\system32> Ok, so the thing I wanted wasn’t in there (an app called PureText, whicih lets me Paste As Text using Windows+V). That’s ok – a simple change to use HKCU instead of HKLM (Current User instead of Local Machine), and I found it. Now to fetch the details of the application itself, using the RegistryKey method GetValue PS C:\Windows\system32> (Get-Item HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\Run).GetValue('PureText') "C:\Users\Rob\Utilities\PureText.exe" PS C:\Windows\system32> And finally, surrounding it in a bit of code to execute that command. That needs an ampersand and the Invoke-Expression cmdlet. PS C:\Windows\system32> '& ' + (Get-Item HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\Run).GetValue('PureText') | Invoke-Expression A simple bit of exploring PowerShell which will makes for a much easier way of finding and running those apps which start with Windows.

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• Chargeback and showback...both a 'throw back'

  - by llaszews

  Been getting asked again by customers and partners about chargeback and showback in the cloud so thought I would blog on my response to this question. Charge Back background, information and industry analysis: Cloud computing is all about shared resources. These shared resources are computer servers (including memory and CPU), network devices, hard disk storage, database servers, application servers, cooling, floor space, electricity and more. These resources are shared by departments within a company, or by a number of companies, when resources are hosted in the public or hybrid cloud. Currently, hosting providers that run other companies on their cloud platforms do not have an accurate way to measure the shared computing resources used by a specific user let alone used by a specific customer. Additionally, companies running their own cloud data centers, for private or hybrid clouds, have no way of measure and charging back the departments in the company that are using these shared cloud resources. In both cases, the lack of determine shared resource costs and to charge them back to the company, department or user that is using this resources is limited a clear measure of business benefit and impacting company’s ability to measure the Return on Investment (ROI). An IT chargeback system is an accounting strategy that applies the costs of IT services, hardware or software to the business unit in which they are used. This system contrasts with traditional IT accounting models in which a centralized department bears all of the IT costs in an organization and those costs are treated simply as corporate overhead. Showback involves showing the IT costs to a department or customer but not actually charging them for their IT usage. Showback is a gradual method of introducing chargeback into an enterprise. Most companies implement a show back mechanism before a full chargeback system is put in place. Oracle chargeback product: Oracle Enterprise Manager provides tools for defining detailed Chargeback plans spanning different metrics collected for each type of resources as well as defining Cost Centers for grouping costs across multiple developers. Chargeback plans can use not only usage based costs, but also configuration based costs (e.g. version of the platform) or fixed costs (e.g. flat-rate management fee). Chargeback has rich out of the box reports. Trending reports show how charge and resource consumption varies over time, while Summary reports show the breakdown of charges or usage by different dimensions such as Cost Center or Target Type. These reports help consumers in understanding how their charges relate to their consumption and also assist the IT department with budgeting and planning activities. With BI Publisher, the reports can be made available in a variety of formats such as PDF, HTML, Word, Excel or PowerPoint.

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• Finding Z given X & Y coordinates on terrain?

  - by mrky

  I need to know what the most efficient way of finding Z given X & Y coordinates on terrain. My terrain is set up as a grid, each grid block consisting of two triangles, which may be flipped in any direction. I want to move game objects smoothly along the floor of the terrain without "stepping." I'm currently using the following method with unexpected results: double mapClass::getZ(double x, double y) { int vertexIndex = ((floor(y))*width*2)+((floor(x))*2); vec3ray ray = {glm::vec3(x, y, 2), glm::vec3(x, y, 0)}; vec3triangle tri1 = { glmFrom(vertices[vertexIndex].v1), glmFrom(vertices[vertexIndex].v2), glmFrom(vertices[vertexIndex].v3) }; vec3triangle tri2 = { glmFrom(vertices[vertexIndex+1].v1), glmFrom(vertices[vertexIndex+1].v2), glmFrom(vertices[vertexIndex+1].v3) }; glm::vec3 intersect; if (!intersectRayTriangle(tri1, ray, intersect)) { intersectRayTriangle(tri2, ray, intersect); } return intersect.z; } intersectRayTriangle() and glmFrom() are as follows: bool intersectRayTriangle(vec3triangle tri, vec3ray ray, glm::vec3 &worldIntersect) { glm::vec3 barycentricIntersect; if (glm::intersectLineTriangle(ray.origin, ray.direction, tri.p0, tri.p1, tri.p2, barycentricIntersect)) { // Convert barycentric to world coordinates double u, v, w; u = barycentricIntersect.x; v = barycentricIntersect.y; w = 1 - (u+v); worldIntersect.x = (u * tri.p0.x + v * tri.p1.x + w * tri.p2.x); worldIntersect.y = (u * tri.p0.y + v * tri.p1.y + w * tri.p2.y); worldIntersect.z = (u * tri.p0.z + v * tri.p1.z + w * tri.p2.z); return true; } else { return false; } } glm::vec3 glmFrom(s_point3f point) { return glm::vec3(point.x, point.y, point.z); } My convenience structures are defined as: struct s_point3f { GLfloat x, y, z; }; struct s_triangle3f { s_point3f v1, v2, v3; }; struct vec3ray { glm::vec3 origin, direction; }; struct vec3triangle { glm::vec3 p0, p1, p2; }; vertices is defined as: std::vector<s_triangle3f> vertices; Basically, I'm trying to get the intersect of a ray (which is positioned at the x, and y coordinates specified facing pointing downwards toward the terrain) and one of the two triangles on the grid. getZ() rarely returns anything but 0. Other times, the numbers it generates seem to be completely off. Am I taking the wrong approach? Can anyone see a problem with my code? Any help or critique is appreciated!

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• DOAG 2012 and Educause 2012

  - by Chris Kawalek

  Oracle understands the value of desktop virtualization and how customers have really embraced it as a top tier method to deliver access to applications and data. Just as supporting operating systems other than Windows in the enterprise desktop space started to become necessary perhaps 5-7 years ago, supporting desktop virtualization with VDI, application virtualization, thin clients, and tablet access is becoming necessary today in 2012. Any application strategy needs to have a secure mobile component, and a solution that gives you a holistic strategy across both mobile and fixed-asset (i.e., desktop PCs) devices is crucial to success. This means it's probably useful to learn about desktop virtualization, even if it's not in your typical area of responsibility. A good way to do that is at one of the many trade shows where we exhibit. Here are two examples:  DOAG 2012 Conference + Exhibition The DOAG Conference is fast approaching, starting November 20th in Nuremberg, Germany. If you've been reading this blog for a while, you might remember that we attended last year as well. This conference is fantastic for us because we get to speak directly to users of Oracle products. In many cases, those DBAs, IT managers, and other infrastructure folks are looking for ways to deal with the burgeoning BYOD model, as well as ways of streamlining their standard desktop and access technologies. We have a couple of sessions where you can learn a great deal about how Oracle can help with these points. Session Schedule (look under "Infrastruktur & Hardware") The two sessions focused on desktop virtualization are: Oracle VDI Best Practice unter Linux (Oracle VDI Best Practice Under Linux) Virtual Desktop Infrastructure Implementierungen und Praxiserfahrungen (Virtual Desktop Infrastructures Implementations and Best Practices) We will also have experts on hand at the booth to answer your questions on using desktop virtualization. If you're at the show, please stop by and say hello to our team there! Educause 2012  Another good example is Educause. We've gone the last few years to show off a slough of education oriented applications and capabilities in the Oracle product portfolio. And every year, we display those applications through Oracle desktop virtualization. This means the demonstration can easily be setup ahead of time and replicated out to however many "demo pods" that we have available. There's no need for our product teams to setup individual laptops for demos -- we can display a standardized Windows desktop virtual machine with their apps all ready to go on a whole bunch of devices like your standard trade show laptop, our Sun Ray Clients, and iPad. Educause 2012 just wrapped, so we're sorry we missed you this year. But there is always next year! Until then, here are a few pictures from this year's show: You can also watch this video to see how Catholic Education Australia uses Oracle Secure Global Desktop to help cope with the ever changing ways that people access their applications.  -Chris 

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• Refresh banshee album art

  - by kmassada

  I usually just copy ~/.config/banshee-1, and ~/.gconf/apps/banshee-1 when i'm moving from one computer to the other, if I keep the path of the folders. I get to keep my music library intact with the playlists I have. The problem with this method is that, the album arts doesn't carry over nicely. You'd have to play every album to get the album art to appear. Anyone knows a workaround, to maybe force banshee to reload all album art? I saw this, but not quite what my issue is? I tried banshee --fetch-artwork, but didn't work too well kenneth@dv7:~$ banshee --fetch-artwork [Warn 11:23:38.200] DBus support could not be started. Disabling for this sessi on. - System.Exception: Error 111: Connection refused (in `dbus-sharp') at DBus.Unix.UnixSocket.Connect (System.Byte[] remote_end) [0x00000] in <filen ame unknown>:0 at DBus.Transports.UnixNativeTransport.OpenAbstractUnix (System.String path) [ 0x00000] in <filename unknown>:0 at DBus.Transports.UnixNativeTransport.Open (System.String path, Boolean abstr act) [0x00000] in <filename unknown>:0 at DBus.Transports.UnixTransport.Open (DBus.AddressEntry entry) [0x00000] in < filename unknown>:0 at DBus.Transports.Transport.Create (DBus.AddressEntry entry) [0x00000] in <fi lename unknown>:0 at DBus.Connection.OpenPrivate (System.String address) [0x00000] in <filename unknown>:0 at DBus.Connection..ctor (System.String address) [0x00000] in <filename unknow n>:0 at DBus.Bus..ctor (System.String address) [0x00000] in <filename unknown>:0 at DBus.Bus.Open (System.String address) [0x00000] in <filename unknown>:0 at DBus.Bus.get_Session () [0x00000] in <filename unknown>:0 System.Exception: Unable to open the session message bus. (in `dbus-sharp') at DBus.Bus.get_Session () [0x00000] in <filename unknown>:0 at DBus.BusG.Init () [0x00000] in <filename unknown>:0 at Banshee.ServiceStack.DBusConnection.Connect (System.String serviceName, Boo lean init) [0x00000] in <filename unknown>:0 at Banshee.ServiceStack.DBusConnection.GrabDefaultName () [0x00000] in <filena me unknown>:0 [Info 11:23:38.286] Running Banshee 2.6.0: [Ubuntu 12.10 (linux-gnu, x86_64) @ 2012-10-11 06:19:37 UTC] (Banshee:21865): GConf-WARNING **: Client failed to connect to the D-BUS daemon: Failed to connect to socket /tmp/dbus-vLxS6Riwsn: Connection refused [Warn 11:23:38.948] Could not read GConf key core.send_anonymous_usage_data - G Lib.GException: No D-BUS daemon running (in `gconf-sharp') at GConf.Client.Get (System.String key) [0x00000] in <filename unknown>:0 at Banshee.GnomeBackend.GConfConfigurationClient.TryGet[Boolean] (System.Strin g namespace, System.String key, System.Boolean& result) [0x00000] in <filename u nknown>:0 (Banshee:21865): GConf-WARNING **: Client failed to connect to the D-BUS daemon: Failed to connect to socket /tmp/dbus-vLxS6Riwsn: Connection refused [Warn 11:23:39.239] Could not read GConf key core.send_anonymous_usage_data - G Lib.GException: No D-BUS daemon running (in `gconf-sharp') at GConf.Client.Get (System.String key) [0x00000] in <filename unknown>:0 at Banshee.GnomeBackend.GConfConfigurationClient.TryGet[Boolean] (System.Strin g namespace, System.String key, System.Boolean& result) [0x00000] in <filename u nknown>:0

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• When following SRP, how should I deal with validating and saving entities?

  - by Kristof Claes

  I've been reading Clean Code and various online articles about SOLID lately, and the more I read about it, the more I feel like I don't know anything. Let's say I'm building a web application using ASP.NET MVC 3. Let's say I have a UsersController with a Create action like this: public class UsersController : Controller { public ActionResult Create(CreateUserViewModel viewModel) { } } In that action method I want to save a user to the database if the data that was entered is valid. Now, according to the Single Responsibility Principle an object should have a single responsibility, and that responsibility should be entirely encapsulated by the class. All its services should be narrowly aligned with that responsibility. Since validation and saving to the database are two separate responsibilities, I guess I should create to separate class to handle them like this: public class UsersController : Controller { private ICreateUserValidator validator; private IUserService service; public UsersController(ICreateUserValidator validator, IUserService service) { this.validator = validator; this.service= service; } public ActionResult Create(CreateUserViewModel viewModel) { ValidationResult result = validator.IsValid(viewModel); if (result.IsValid) { service.CreateUser(viewModel); return RedirectToAction("Index"); } else { foreach (var errorMessage in result.ErrorMessages) { ModelState.AddModelError(String.Empty, errorMessage); } return View(viewModel); } } } That makes some sense to me, but I'm not at all sure that this is the right way to handle things like this. It is for example entirely possible to pass an invalid instance of CreateUserViewModel to the IUserService class. I know I could use the built in DataAnnotations, but what when they aren't enough? Image that my ICreateUserValidator checks the database to see if there already is another user with the same name... Another option is to let the IUserService take care of the validation like this: public class UserService : IUserService { private ICreateUserValidator validator; public UserService(ICreateUserValidator validator) { this.validator = validator; } public ValidationResult CreateUser(CreateUserViewModel viewModel) { var result = validator.IsValid(viewModel); if (result.IsValid) { // Save the user } return result; } } But I feel I'm violating the Single Responsibility Principle here. How should I deal with something like this?

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• OpenGL flickerinng near the edges

  - by Daniel

  I am trying to simulate particles moving around the scene with OpenCL for computation and OpenGL for rendering with GLUT. There is no OpenCL-OpenGL interop yet, so the drawing is done in the older fixed pipeline way. Whenever circles get close to the edges, they start to flicker. The drawing should draw a part of the circle on the top of the scene and a part on the bottom. The effect is the following: The balls you see on the bottom should be one part on the bottom and one part on the top. Wrapping around the scene, so to say, but they constantly flicker. The code for drawing them is: void Scene::drawCircle(GLuint index){ glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glTranslatef(pos.at(2*index),pos.at(2*index+1), 0.0f); glBegin(GL_TRIANGLE_FAN); GLfloat incr = (2.0 * M_PI) / (GLfloat) slices; glColor3f(0.8f, 0.255f, 0.26f); glVertex2f(0.0f, 0.0f); glColor3f(1.0f, 0.0f, 0.0f); for(GLint i = 0; i <=slices; ++i){ GLfloat x = radius * sin((GLfloat) i * incr); GLfloat y = radius * cos((GLfloat) i * incr); glVertex2f(x, y); } glEnd(); } If it helps, this is the reshape method: void Scene::reshape(GLint width, GLint height){ if(0 == height) height = 1; //Prevent division by zero glViewport(0, 0, width, height); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D(xmin, xmax, ymin, ymax); std::cout << xmin << " " << xmax << " " << ymin << " " << ymax << std::endl; }

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• How to join two collections with LINQ

  - by JustinGreenwood

  Here is a simple and complete example of how to perform joins on two collections with LINQ. I wrote it for a friend to show him, in one simple file, the power of LINQ queries and anonymous objects. In the file below, there are two simple data classes defined: Person and Item. In the beginning of the main method, two collections are created. Note that the Item's OwnerId field reference the PersonId of a Person object. The effect of the LINQ query below is equivalent to a SQL statement looking like this: select Person.PersonName as OwnerName, Item.ItemName as OwnedItem from Person inner join Item on Item.OwnerId = Person.PersonId order by Item.ItemName desc; using System; using System.Collections.Generic; using System.Linq; namespace LinqJoinAnonymousObjects { class Program { class Person { public int PersonId { get; set; } public string PersonName { get; set; } } class Item { public string ItemName { get; set; } public int OwnerId { get; set; } } static void Main(string[] args) { // Create two collections: one of people, and another with their possessions. var people = new List<Person> { new Person { PersonId=1, PersonName="Justin" }, new Person { PersonId=2, PersonName="Arthur" }, new Person { PersonId=3, PersonName="Bob" } }; var items = new List<Item> { new Item { OwnerId=1, ItemName="Armor" }, new Item { OwnerId=1, ItemName="Book" }, new Item { OwnerId=2, ItemName="Chain Mail" }, new Item { OwnerId=2, ItemName="Excalibur" }, new Item { OwnerId=3, ItemName="Bubbles" }, new Item { OwnerId=3, ItemName="Gold" } }; // Create a new, anonymous composite result for person id=2. var compositeResult = from p in people join i in items on p.PersonId equals i.OwnerId where p.PersonId == 2 orderby i.ItemName descending select new { OwnerName = p.PersonName, OwnedItem = i.ItemName }; // The query doesn't evaluate until you iterate through the query or convert it to a list Console.WriteLine("[" + compositeResult.GetType().Name + "]"); // Convert to a list and loop through it. var compositeList = compositeResult.ToList(); Console.WriteLine("[" + compositeList.GetType().Name + "]"); foreach (var o in compositeList) { Console.WriteLine("\t[" + o.GetType().Name + "] " + o.OwnerName + " - " + o.OwnedItem); } Console.ReadKey(); } } } The output of the program is below: [WhereSelectEnumerableIterator`2] [List`1] [<>f__AnonymousType1`2] Arthur - Excalibur [<>f__AnonymousType1`2] Arthur - Chain Mail

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• Use CSS Selectors with HtmlUnit

  - by kerry

  HtmlUnit is a great library for performing web integration tests in Java.  But sometimes node traversal can be somewhat cumbersome. Fear not fellow automated tester (good for you!).  I found a great little project on Github that will allow you to query your document for elements via css selectors similar to jQuery. The project is located at https://github.com/chrsan/css-selectors.  You can use Maven to build it, or download 1.0.2 here.  Beware.  I will not be updating this link so I suggest you download the latest code. In any case, you can use it like so: // from HtmlUnit getting started final WebClient webClient = new WebClient(); final HtmlPage page = webClient.getPage("http://htmlunit.sourceforge.net"); final DOMNodeSelector cssSelector = new DOMNodeSelector(page.getDocumentElement()); final Set elements = cssSelector.querySelectorAll("div.section h2"); final Node first = elements.iterator().next(); assertThat(first.getTextContent(), equalTo("HtmlUnit")); The only problem here is that the querySelectAll returns a Set<Node>.  Not HtmlElement like we may want in some cases.   However, if you were to reflect on the Set, you would find that it is indeed a Set of HtmlElement objects. Typically, I like to create a base class for my web tests.  Just for fun, I am using the $ method similar to jQuery. public class WebTestBase { protected WebClient webClient; protected HtmlPage htmlPage; protected void goTo(final String url){ return (HtmlPage)webClient.getPage(url); } protected List $(final String cssSelector) { final DOMNodeSelector cssSelector = new DOMNodeSelector(htmlPage.getDocumentElement()); final Set nodes = cssSelector.querySelectorAll("div.section h2"); // for some reason Set cannot be cast to Set? final List elements = new ArrayList(nodes.size()); for (final Node node : nodes) { elements.add((HtmlElement)node); } return elements; } } Now we can write tests like this: public class LoginWebTest extends WebTestBase { @Test public void login_page_has_instructions() throws Exception { goTo(baseUrl + "/login") assertThat( $("p.instructions").size(), equalTo(1) ); } }

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• Using machine learning to aim mirrors in a solar array?

  - by Buttons840

  I've been thinking about solar collectors where several independent mirrors to focus the light on a solar collector, similar to the following design from Energy Innovations. Because there will be flaws in the assembly of this solar array, I am proceeding with the following assumptions (or lack thereof): The software knows the "position" of each mirror, but doesn't know how this position relates to the real world or to other mirrors. This will account for poor mirror calibration or other environmental factors which may effect one mirror but not the others. If a mirror moves 10 units in one direction, and then 10 units in the opposite direction, it will end up where it originally started. I would like to use machine learning to position the mirrors correctly and focus the light on the collector. I expect I would approach this as an optimization problem, optimizing the mirror positions to maximize the heat inside the collector and the power output. The problem is finding a small target in a noisy high-dimensional space (considering each mirror has 2 axis of rotation). Some of the problems I anticipate are: cloudy days, even if you stumble upon the perfect mirror alignment, it might be cloudy at the time noisy sensor data the sun is a moving target, it moves along a path, and follows a different path every day - although you could calculate the exact position of the sun at any time, you wouldn't know how that position relates to your mirrors My question isn't about the solar array, but possible machine learning techniques that would help in this "small target in a noisy high dimensional-space" problem. I mentioned the solar array because it was the catalyst for this question and a good example. What machine learning techniques can find such a small target in a noisy high-dimensional space? EDIT: A few additional thoughts: Yes, you can calculate the suns position in the real world, but you don't know how the mirrors position is related to the real world (unless you've learned it somehow). You might know the suns azimuth is 220 degrees, and the suns elevation is 60 degrees, and you might know a mirror is at position (-20, 42); now tell me, is that mirror correctly aligned with the sun? You don't know. Lets assume you have some very sophisticated heat measurements, and you know "with this heat level, there must be 2 mirrors correctly aligned". Now the question is, which two mirrors (out of 25 or more) are correctly aligned? One solution I considered was to approximate the correct "alignment function" using a neural network which would take the suns azimuth and elevation as input and output a large array with 2 values for each mirror which correspond to the 2 axis of each mirror. I'm not sure what the best training method is though.

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