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  • C#/.NET Little Wonders: Static Char Methods

    - by James Michael Hare
    Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Often times in our code we deal with the bigger classes and types in the BCL, and occasionally forgot that there are some nice methods on the primitive types as well.  Today we will discuss some of the handy static methods that exist on the char (the C# alias of System.Char) type. The Background I was examining a piece of code this week where I saw the following: 1: // need to get the 5th (offset 4) character in upper case 2: var type = symbol.Substring(4, 1).ToUpper(); 3:  4: // test to see if the type is P 5: if (type == "P") 6: { 7: // ... do something with P type... 8: } Is there really any error in this code?  No, but it still struck me wrong because it is allocating two very short-lived throw-away strings, just to store and manipulate a single char: The call to Substring() generates a new string of length 1 The call to ToUpper() generates a new upper-case version of the string from Step 1. In my mind this is similar to using ToUpper() to do a case-insensitive compare: it isn’t wrong, it’s just much heavier than it needs to be (for more info on case-insensitive compares, see #2 in 5 More Little Wonders). One of my favorite books is the C++ Coding Standards: 101 Rules, Guidelines, and Best Practices by Sutter and Alexandrescu.  True, it’s about C++ standards, but there’s also some great general programming advice in there, including two rules I love:         8. Don’t Optimize Prematurely         9. Don’t Pessimize Prematurely We all know what #8 means: don’t optimize when there is no immediate need, especially at the expense of readability and maintainability.  I firmly believe this and in the axiom: it’s easier to make correct code fast than to make fast code correct.  Optimizing code to the point that it becomes difficult to maintain often gains little and often gives you little bang for the buck. But what about #9?  Well, for that they state: “All other things being equal, notably code complexity and readability, certain efficient design patterns and coding idioms should just flow naturally from your fingertips and are no harder to write then the pessimized alternatives. This is not premature optimization; it is avoiding gratuitous pessimization.” Or, if I may paraphrase: “where it doesn’t increase the code complexity and readability, prefer the more efficient option”. The example code above was one of those times I feel where we are violating a tacit C# coding idiom: avoid creating unnecessary temporary strings.  The code creates temporary strings to hold one char, which is just unnecessary.  I think the original coder thought he had to do this because ToUpper() is an instance method on string but not on char.  What he didn’t know, however, is that ToUpper() does exist on char, it’s just a static method instead (though you could write an extension method to make it look instance-ish). This leads me (in a long-winded way) to my Little Wonders for the day… Static Methods of System.Char So let’s look at some of these handy, and often overlooked, static methods on the char type: IsDigit(), IsLetter(), IsLetterOrDigit(), IsPunctuation(), IsWhiteSpace() Methods to tell you whether a char (or position in a string) belongs to a category of characters. IsLower(), IsUpper() Methods that check if a char (or position in a string) is lower or upper case ToLower(), ToUpper() Methods that convert a single char to the lower or upper equivalent. For example, if you wanted to see if a string contained any lower case characters, you could do the following: 1: if (symbol.Any(c => char.IsLower(c))) 2: { 3: // ... 4: } Which, incidentally, we could use a method group to shorten the expression to: 1: if (symbol.Any(char.IsLower)) 2: { 3: // ... 4: } Or, if you wanted to verify that all of the characters in a string are digits: 1: if (symbol.All(char.IsDigit)) 2: { 3: // ... 4: } Also, for the IsXxx() methods, there are overloads that take either a char, or a string and an index, this means that these two calls are logically identical: 1: // check given a character 2: if (char.IsUpper(symbol[0])) { ... } 3:  4: // check given a string and index 5: if (char.IsUpper(symbol, 0)) { ... } Obviously, if you just have a char, then you’d just use the first form.  But if you have a string you can use either form equally well. As a side note, care should be taken when examining all the available static methods on the System.Char type, as some seem to be redundant but actually have very different purposes.  For example, there are IsDigit() and IsNumeric() methods, which sound the same on the surface, but give you different results. IsDigit() returns true if it is a base-10 digit character (‘0’, ‘1’, … ‘9’) where IsNumeric() returns true if it’s any numeric character including the characters for ½, ¼, etc. Summary To come full circle back to our opening example, I would have preferred the code be written like this: 1: // grab 5th char and take upper case version of it 2: var type = char.ToUpper(symbol[4]); 3:  4: if (type == 'P') 5: { 6: // ... do something with P type... 7: } Not only is it just as readable (if not more so), but it performs over 3x faster on my machine:    1,000,000 iterations of char method took: 30 ms, 0.000050 ms/item.    1,000,000 iterations of string method took: 101 ms, 0.000101 ms/item. It’s not only immediately faster because we don’t allocate temporary strings, but as an added bonus there less garbage to collect later as well.  To me this qualifies as a case where we are using a common C# performance idiom (don’t create unnecessary temporary strings) to make our code better. Technorati Tags: C#,CSharp,.NET,Little Wonders,char,string

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  • Financial Management: Why Move to the Cloud?

    - by Kathryn Perry
    A guest post by Terrance Wampler, Vice President, Financials Product Strategy, Oracle I’ve spent my career designing and developing financial management systems, most of it at Oracle. Every single day I either meet with our customers or talk to them on the phone. The time is usually spent discussing various business challenges facing CFOs and Controllers, who are running Oracle’s Financials. Lately, we’ve been talking a lot about cloud computing and whether it makes sense for finance to go to the cloud. Here are some pros and cons that might help you make that decision. Let’s start with the benefits of cloud solutions. The first is savings. With cloud services, you pay only for those commodities that you use. That makes you feel like you're getting better value for your money. Plus, you can preserve your cash for your core business and you can get a better matching of expenses and revenues. So, at the top of the list is lower total cost of ownership. The second point has to do with optimization. With cloud services, you’ll need less IT infrastructure so you can optimize your IT resources for better-value, higher-end projects. This also leads to greater financial visibility, where there's a clear cost for the set of services or features replaced by cloud services. And, the last benefit is what I call acceleration. You can save money by speeding up the initialization and deployment of the project. You don't have to deal with IT infrastructure and you can start implementing right away. We did a quick survey of about 70 CFOs at the CFO Summit last month in New York City. We asked them why they were looking at cloud services, and not necessarily just for financials. The No. 1 response was perceived lower cost of ownership. But of course there are risks to consider. The first thing most people think about in the cloud is security and ownership of data. So, will your data really be safe? Can you meet your own privacy policy requirements? Do you really want your private financial data exposed? Do you trust the provider? Is what you see really your data? Do you own it or is it managed by someone else? Security is a big concern that comes with an emotional component. The next thing in the risk category is reliability. Is the provider proven? You’re taking what you have control over – for example, standards and policies and internal service level agreements – away from your IT department and giving it to someone else. Will you still be able to adapt to shifts in your business? Will the provider be able to grow with your business effectively? Reliability means having a provider that can give you the service infrastructure that you need. And then there’s performance, which has two components in terms of risk. Going forward, will the provider be able to scale the infrastructure or service level if you have new employees or new businesses? And second, will the price you negotiate and the rate you lock in cover additional costs and rising service fees? Another piece is cost. What happens if you don't get the service level you want? What if you end the service? What happens, if after a few years, you send the service out for bid and change service? Can you move your data? Can you move the applications? Do the integrations work? These are cost components people don’t always take into account. And, the final piece is the business case. The perception is that you can get started really quickly with cloud. It has a perceived lower cost of total ownership and it feels cool because it's cloud. But do you have a good business case for moving to the cloud? Your total cost of ownership is over three years; then you’ll renew it, so your TCO is six years. Have you compared that to other internal services that you’re offering? You might already have product that you can run this new business or division on. In that same survey at the CFO Summit, the execs thought the biggest perceived risks were security of data, ability to move data back, and the ability to create a business case to actually justify the risks. So that’s the list of pros and cons. Not to leave you hanging, I will do another post on how to balance these pros and cons and make the right decision for your business.

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  • Problems implementing a screen space shadow ray tracing shader

    - by Grieverheart
    Here I previously asked for the possibility of ray tracing shadows in screen space in a deferred shader. Several problems were pointed out. One of the most important problem is that only visible objects can cast shadows and objects between the camera and the shadow caster can interfere. Still I thought it'd be a fun experiment. The idea is to calculate the view coordinates of pixels and cast a ray to the light. The ray is then traced pixel by pixel to the light and its depth is compared with the depth at the pixel. If a pixel is in front of the ray, a shadow is casted at the original pixel. At first I thought that I could use the DDA algorithm in 2D to calculate the distance 't' (in p = o + t d, where o origin, d direction) to the next pixel and use it in the 3D ray equation to find the ray's z coordinate at that pixel's position. For the 2D ray, I would use the projected and biased 3D ray direction and origin. The idea was that 't' would be the same in both 2D and 3D equations. Unfortunately, this is not the case since the projection matrix is 4D. Thus, some tweak needs to be done to make this work this way. I would like to ask if someone knows of a way to do what I described above, i.e. from a 2D ray in texture coordinate space to get the 3D ray in screen space. I did implement a simple version of the idea which you can see in the following video: video here Shadows may seem a bit pixelated, but that's mostly because of the size of the step in 't' I chose. And here is the shader: #version 330 core uniform sampler2D DepthMap; uniform vec2 projAB; uniform mat4 projectionMatrix; const vec3 light_p = vec3(-30.0, 30.0, -10.0); noperspective in vec2 pass_TexCoord; smooth in vec3 viewRay; layout(location = 0) out float out_AO; vec3 CalcPosition(void){ float depth = texture(DepthMap, pass_TexCoord).r; float linearDepth = projAB.y / (depth - projAB.x); vec3 ray = normalize(viewRay); ray = ray / ray.z; return linearDepth * ray; } void main(void){ vec3 origin = CalcPosition(); if(origin.z < -60) discard; vec2 pixOrigin = pass_TexCoord; //tex coords vec3 dir = normalize(light_p - origin); vec2 texel_size = vec2(1.0 / 600.0); float t = 0.1; ivec2 pixIndex = ivec2(pixOrigin / texel_size); out_AO = 1.0; while(true){ vec3 ray = origin + t * dir; vec4 temp = projectionMatrix * vec4(ray, 1.0); vec2 texCoord = (temp.xy / temp.w) * 0.5 + 0.5; ivec2 newIndex = ivec2(texCoord / texel_size); if(newIndex != pixIndex){ float depth = texture(DepthMap, texCoord).r; float linearDepth = projAB.y / (depth - projAB.x); if(linearDepth > ray.z + 0.1){ out_AO = 0.2; break; } pixIndex = newIndex; } t += 0.5; if(texCoord.x < 0 || texCoord.x > 1.0 || texCoord.y < 0 || texCoord.y > 1.0) break; } } As you can see, here I just increment 't' by some arbitrary factor, calculate the 3D ray and project it to get the pixel coordinates, which is not really optimal. Hopefully, I would like to optimize the code as much as possible and compare it with shadow mapping and how it scales with the number of lights. PS: Keep in mind that I reconstruct position from depth by interpolating rays through a full screen quad.

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  • Requesting feedback on my OO design

    - by Prog
    I'm working on an application that creates music by itself. I'm seeking feedback for my OO design so far. This question will focus on one part of the program. The application produces Tune objects, that are the final musical products. Tune is an abstract class with an abstract method play. It has two subclasses: SimpleTune and StructuredTune. SimpleTune owns a Melody and a Progression (chord sequence). It's play implementation plays these two objects simultaneously. StructuredTune owns two Tune instances. It's own play plays the two Tunes one after the other according to a pattern (currently only ABAB). Melody is an abstract class with an abstract play method. It has two subclasses: SimpleMelody and StructuredMelody. SimpleMelody is composed of an array of notes. Invoking play on it plays these notes one after the other. StructuredMelody is composed of an array of Melody objects. Invoking play on it plays these Melodyies one after the other. I think you're starting to see the pattern. Progression is also an abstract class with a play method and two subclasses: SimpleProgression and StructuredProgression, each composed differently and played differently. SimpleProgression owns an array of chords and plays them sequentially. StructuredProgression owns an array of Progressions and it's play implementation plays them sequentially. Every class has a corresponding Generator class. Tune, Melody and Progression are matched with corresponding abstract TuneGenerator, MelodyGenerator and ProgressionGenerator classes, each with an abstract generate method. For example MelodyGenerator defines an abstract Melody generate method. Each of the generators has two subclasses, Simple and Structured. So for example MelodyGenerator has a subclasses SimpleMelodyGenerator, with an implementation of generate that returns a SimpleMelody. (It's important to note that the generate methods encapsulate complex algorithms. They are more than mere factory method. For example SimpleProgressionGenerator.generate() implements an algorithm to compose a series of Chord objects, which are used to instantiate the returned SimpleProgression). Every Structured generator uses another generator internally. It is a Simple generator be default, but in special cases may be a Structured generator. Parts of this design are meant to allow the end-user through the GUI to choose what kind of music is to be created. For example the user can choose between a "simple tune" (SimpleTuneGenerator) and a "full tune" (StructuredTuneGenerator). Other parts of the system aren't subject to direct user-control. What do you think of this design from an OOD perspective? What potential problems do you see with this design? Please share with me your criticism, I'm here to learn. Apart from this, a more specific question: the "every class has a corresponding Generator class" part feels very wrong. However I'm not sure how I could design this differently and achieve the same flexibility. Any ideas?

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  • Best depth sorting method for a Top Down 2D game using a 3D physics engine

    - by Alic44
    I've spent many days googling this and still have issues with my game engine I'd like to ask about, which I haven't seen addressed before. I think the problem is that my game is an unusual combination of a completely 2D graphical approach using XNA's SpriteBatch, and a completely 3D engine (the amazing BEPU physics engine) with rotation mostly disabled. In essence, my question is similar to this one (the part about "faux 3D"), but the difference is that in my game, the player as well as every other creature is represented by 3D objects, and they can all jump, pick up other objects, and throw them around. What this means is that sorting by one value, such as a Z position (how far north/south a character is on the screen) won't work, because as soon as a smaller creature jumps on top of a larger creature, or a box, and walks backwards, the moment its z value is less than that other creature, it will appear to be behind the object it is actually standing on. I actually originally solved this problem by splitting every object in the game into physics boxes which MUST have a Y height equal to their Z depth. I then based the depth sorting value on the object's y position (how high it is off the ground) PLUS its z position (how far north or south it is on the screen). The problem with this approach is that it requires all moving objects in the game to be split graphically into chunks which match up with a physical box which has its y dimension equal to its z dimension. Which is stupid. So, I got inspired last night to rewrite with a fresh approach. My new method is a little more complex, but I think a little more sane: every object which needs to be sorted by depth in the game exposes the interface IDepthDrawable and is added to a list owned by the DepthDrawer object. IDepthDrawable contains: public interface IDepthDrawable { Rectangle Bounds { get; } //possibly change this to a class if struct copying of the xna Rectangle type becomes an issue DepthDrawShape DepthShape { get; } void Draw(SpriteBatch spriteBatch); } The Bounds Rectangle of each IDepthDrawable object represents the 2D Axis-Aligned Bounding Box it will take up when drawn to the screen. Anything that doesn't intersect the screen will be culled at this stage and the remaining on-screen IDepthDrawables will be Bounds tested for intersections with each other. This is where I get a little less sure of what I'm doing. Each group of collisions will be added to a list or other collection, and each list will sort itself based on its DepthShape property, which will have access to the object-to-be-drawn's physics information. For starting out, lets assume everything in the game is an axis aligned 3D Box shape. Boxes are pretty easy to sort. Something like: if (depthShape1.Back > depthShape2.Front) //if depthShape1 is in front of depthShape2. //depthShape1 goes on top. else if (depthShape1.Bottom > depthShape2.Top) //if depthShape1 is above depthShape2. //depthShape1 goes on top. //if neither of these are true, depthShape2 must be in front or above. So, by sorting draw order by several different factors from the physics engine, I believe I can get a really correct draw order. My question is, is this a good way of going about this, or is there some tried and true, tested way which is completely different and has somehow completely eluded me on the internets? And, if this does seem like a good way to remake my draw order sorting, what's the right sorting algorithm for reordering the Bounds Rectangle collision lists, and how do you deal with a Bounds Rectangle colliding with two different object which don't collide with eachother. I know these are solved problems, but I've only been programming for a year so any specific input here will be greatly appreciated. Thanks for reading this far, ye who made it -- sorry it was so long!

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  • Determining explosion radius damage - Circle to Rectangle 2D

    - by Paul Renton
    One of the Cocos2D games I am working on has circular explosion effects. These explosion effects need to deal a percentage of their set maximum damage to all game characters (represented by rectangular bounding boxes as the objects in question are tanks) within the explosion radius. So this boils down to circle to rectangle collision and how far away the circle's radius is from the closest rectangle edge. I took a stab at figuring this out last night, but I believe there may be a better way. In particular, I don't know the best way to determine what percentage of damage to apply based on the distance calculated. Note : All tank objects have an anchor point of (0,0) so position is according to bottom left corner of bounding box. Explosion point is the center point of the circular explosion. TankObject * tank = (TankObject*) gameSprite; float distanceFromExplosionCenter; // IMPORTANT :: All GameCharacter have an assumed (0,0) anchor if (explosionPoint.x < tank.position.x) { // Explosion to WEST of tank if (explosionPoint.y <= tank.position.y) { //Explosion SOUTHWEST distanceFromExplosionCenter = ccpDistance(explosionPoint, tank.position); } else if (explosionPoint.y >= (tank.position.y + tank.contentSize.height)) { // Explosion NORTHWEST distanceFromExplosionCenter = ccpDistance(explosionPoint, ccp(tank.position.x, tank.position.y + tank.contentSize.height)); } else { // Exp center's y is between bottom and top corner of rect distanceFromExplosionCenter = tank.position.x - explosionPoint.x; } // end if } else if (explosionPoint.x > (tank.position.x + tank.contentSize.width)) { // Explosion to EAST of tank if (explosionPoint.y <= tank.position.y) { //Explosion SOUTHEAST distanceFromExplosionCenter = ccpDistance(explosionPoint, ccp(tank.position.x + tank.contentSize.width, tank.position.y)); } else if (explosionPoint.y >= (tank.position.y + tank.contentSize.height)) { // Explosion NORTHEAST distanceFromExplosionCenter = ccpDistance(explosionPoint, ccp(tank.position.x + tank.contentSize.width, tank.position.y + tank.contentSize.height)); } else { // Exp center's y is between bottom and top corner of rect distanceFromExplosionCenter = explosionPoint.x - (tank.position.x + tank.contentSize.width); } // end if } else { // Tank is either north or south and is inbetween left and right corner of rect if (explosionPoint.y < tank.position.y) { // Explosion is South distanceFromExplosionCenter = tank.position.y - explosionPoint.y; } else { // Explosion is North distanceFromExplosionCenter = explosionPoint.y - (tank.position.y + tank.contentSize.height); } // end if } // end outer if if (distanceFromExplosionCenter < explosionRadius) { /* Collision :: Smaller distance larger the damage */ int damageToApply; if (self.directHit) { damageToApply = self.explosionMaxDamage + self.directHitBonusDamage; [tank takeDamageAndAdjustHealthBar:damageToApply]; CCLOG(@"Explsoion-> DIRECT HIT with total damage %d", damageToApply); } else { // TODO adjust this... turning out negative for some reason... damageToApply = (1 - (distanceFromExplosionCenter/explosionRadius) * explosionMaxDamage); [tank takeDamageAndAdjustHealthBar:damageToApply]; CCLOG(@"Explosion-> Non direct hit collision with tank"); CCLOG(@"Damage to apply is %d", damageToApply); } // end if } else { CCLOG(@"Explosion-> Explosion distance is larger than explosion radius"); } // end if } // end if Questions: 1) Can this circle to rect collision algorithm be done better? Do I have too many checks? 2) How to calculate the percentage based damage? My current method generates negative numbers occasionally and I don't understand why (Maybe I need more sleep!). But, in my if statement, I ask if distance < explosion radius. When control goes through, distance/radius must be < 1 right? So 1 - that intermediate calculation should not be negative. Appreciate any help/advice!

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  • Grid pathfinding with a lot of entities

    - by Vee
    I'd like to explain this problem with a screenshot from a released game, DROD: Gunthro's Epic Blunder, by Caravel Games. The game is turn-based and tile-based. I'm trying to create something very similar (a clone of the game), and I've got most of the fundamentals done, but I'm having trouble implementing pathfinding. Look at the screenshot. The guys in yellow are friendly, and want to kill the roaches. Every turn, every guy in yellow pathfinds to the closest roach, and every roach pathfinds to the closest guy in yellow. By closest I mean the target with the shortest path, not a simple distance calculation. All of this without any kind of slowdown when loading the level or when passing turns. And all of the entities change position every turn. Also (not shown in screenshot), there can be doors that open and close and change the level's layout. Impressive. I've tried implementing pathfinding in my clone. First attempt was making every roach find a path to a yellow guy every turn, using a breadth-first search algorithm. Obviously incredibly slow with more than a single roach, and would get exponentially slower with more than a single yellow guy. Second attempt was mas making every yellow guy generate a pathmap (still breadth-first search) every time he moved. Worked perfectly with multiple roaches and a single yellow guy, but adding more yellow guys made the game slow and unplayable. Last attempt was implementing JPS (jump point search). Every entity would individually calculate a path to its target. Fast, but with a limited number of entities. Having less than half the entities in the screenshot would make the game slow. And also, I had to get the "closest" enemy by calculating distance, not shortest path. I've asked on the DROD forums how they did it, and a user replied that it was breadth-first search. The game is open source, and I took a look at the source code, but it's C++ (I'm using C#) and I found it confusing. I don't know how to do it. Every approach I tried isn't good enough. And I believe that DROD generates global pathmaps, somehow, but I can't understand how every entity find the best individual path to other entities that move every turn. What's the trick? This is a reply I just got on the DROD forums: Without having looked at the code I'd wager it's two (or so) pathmaps for the whole room: One to the nearest enemy, and one to the nearest friendly for every tile. There's no need to make a separate pathmap for every entity when the overall goal is "move towards nearest enemy/friendly"... just mark every tile with the number of moves it takes to the nearest target and have the entity chose the move that takes it to the tile with the lowest number. To be honest, I don't understand it that well.

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  • SQL ADO.NET shortcut extensions (old school!)

    - by Jeff
    As much as I love me some ORM's (I've used LINQ to SQL quite a bit, and for the MSDN/TechNet Profile and Forums we're using NHibernate more and more), there are times when it's appropriate, and in some ways more simple, to just throw up so old school ADO.NET connections, commands, readers and such. It still feels like a pain though to new up all the stuff, make sure it's closed, blah blah blah. It's pretty much the least favorite task of writing data access code. To minimize the pain, I have a set of extension methods that I like to use that drastically reduce the code you have to write. Here they are... public static void Using(this SqlConnection connection, Action<SqlConnection> action) {     connection.Open();     action(connection);     connection.Close(); } public static SqlCommand Command(this SqlConnection connection, string sql){    var command = new SqlCommand(sql, connection);    return command;}public static SqlCommand AddParameter(this SqlCommand command, string parameterName, object value){    command.Parameters.AddWithValue(parameterName, value);    return command;}public static object ExecuteAndReturnIdentity(this SqlCommand command){    if (command.Connection == null)        throw new Exception("SqlCommand has no connection.");    command.ExecuteNonQuery();    command.Parameters.Clear();    command.CommandText = "SELECT @@IDENTITY";    var result = command.ExecuteScalar();    return result;}public static SqlDataReader ReadOne(this SqlDataReader reader, Action<SqlDataReader> action){    if (reader.Read())        action(reader);    reader.Close();    return reader;}public static SqlDataReader ReadAll(this SqlDataReader reader, Action<SqlDataReader> action){    while (reader.Read())        action(reader);    reader.Close();    return reader;} It has been awhile since I've really revisited these, so you will likely find opportunity for further optimization. The bottom line here is that you can chain together a bunch of these methods to make a much more concise database call, in terms of the code on your screen, anyway. Here are some examples: public Dictionary<string, string> Get(){    var dictionary = new Dictionary<string, string>();    _sqlHelper.GetConnection().Using(connection =>        connection.Command("SELECT Setting, [Value] FROM Settings")            .ExecuteReader()            .ReadAll(r => dictionary.Add(r.GetString(0), r.GetString(1))));    return dictionary;} or... public void ChangeName(User user, string newName){    _sqlHelper.GetConnection().Using(connection =>         connection.Command("UPDATE Users SET Name = @Name WHERE UserID = @UserID")            .AddParameter("@Name", newName)            .AddParameter("@UserID", user.UserID)            .ExecuteNonQuery());} The _sqlHelper.GetConnection() is just some other code that gets a connection object for you. You might have an even cleaner way to take that step out entirely. This looks more fluent, and the real magic sauce for me is the reader bits where you can put any kind of arbitrary method in there to iterate over the results.

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  • Schizophrenic Ubuntu 12.10-12.04: Atheros 922 PCI WIFI is disabled in Unity but enabled in terminal - How to getit to work?

    - by zewone
    I am trying to get my PCI Wireless Atheros 922 card to work. It is disabled in Unity: both the network utility and the desktop (see screenshot http://www.amisdurailhalanzy.be/Screenshot%20from%202012-10-25%2013:19:54.png) I tried many different advises on many different forums. Installed 12.10 instead of 12.04, enabled all interfaces... etc. I have read about the aht9 driver... The terminal shows no hw or sw lock for the Atheros card, nevertheless, it is still disabled. Nothing worked so far, the card is still disabled. Any help is much appreciated. Here are more tech details: myuser@adri1:~$ sudo lshw -C network *-network:0 DISABLED description: Wireless interface product: AR922X Wireless Network Adapter vendor: Atheros Communications Inc. physical id: 2 bus info: pci@0000:03:02.0 logical name: wlan1 version: 01 serial: 00:18:e7:cd:68:b1 width: 32 bits clock: 66MHz capabilities: pm bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=ath9k driverversion=3.5.0-17-generic firmware=N/A latency=168 link=no multicast=yes wireless=IEEE 802.11bgn resources: irq:18 memory:d8000000-d800ffff *-network:1 description: Ethernet interface product: VT6105/VT6106S [Rhine-III] vendor: VIA Technologies, Inc. physical id: 6 bus info: pci@0000:03:06.0 logical name: eth0 version: 8b serial: 00:11:09:a3:76:4a size: 10Mbit/s capacity: 100Mbit/s width: 32 bits clock: 33MHz capabilities: pm bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=via-rhine driverversion=1.5.0 duplex=half latency=32 link=no maxlatency=8 mingnt=3 multicast=yes port=MII speed=10Mbit/s resources: irq:18 ioport:d300(size=256) memory:d8013000-d80130ff *-network DISABLED description: Wireless interface physical id: 1 bus info: usb@1:8.1 logical name: wlan0 serial: 00:11:09:51:75:36 capabilities: ethernet physical wireless configuration: broadcast=yes driver=rt2500usb driverversion=3.5.0-17-generic firmware=N/A link=no multicast=yes wireless=IEEE 802.11bg myuser@adri1:~$ sudo rfkill list all 0: hci0: Bluetooth Soft blocked: no Hard blocked: no 1: phy1: Wireless LAN Soft blocked: no Hard blocked: yes 2: phy0: Wireless LAN Soft blocked: no Hard blocked: no myuser@adri1:~$ dmesg | grep wlan0 [ 15.114235] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready myuser@adri1:~$ dmesg | egrep 'ath|firm' [ 14.617562] ath: EEPROM regdomain: 0x30 [ 14.617568] ath: EEPROM indicates we should expect a direct regpair map [ 14.617572] ath: Country alpha2 being used: AM [ 14.617575] ath: Regpair used: 0x30 [ 14.637778] ieee80211 phy0: >Selected rate control algorithm 'ath9k_rate_control' [ 14.639410] Registered led device: ath9k-phy0 myuser@adri1:~$ dmesg | grep wlan1 [ 15.119922] IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready myuser@adri1:~$ lspci -nn | grep 'Atheros' 03:02.0 Network controller [0280]: Atheros Communications Inc. AR922X Wireless Network Adapter [168c:0029] (rev 01) myuser@adri1:~$ sudo ifconfig eth0 Link encap:Ethernet HWaddr 00:11:09:a3:76:4a inet addr:192.168.2.2 Bcast:192.168.2.255 Mask:255.255.255.0 inet6 addr: fe80::211:9ff:fea3:764a/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:5457 errors:0 dropped:0 overruns:0 frame:0 TX packets:2548 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:3425684 (3.4 MB) TX bytes:282192 (282.1 KB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:590 errors:0 dropped:0 overruns:0 frame:0 TX packets:590 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:53729 (53.7 KB) TX bytes:53729 (53.7 KB) myuser@adri1:~$ sudo iwconfig wlan0 IEEE 802.11bg ESSID:off/any Mode:Managed Access Point: Not-Associated Tx-Power=off Retry long limit:7 RTS thr:off Fragment thr:off Encryption key:off Power Management:on lo no wireless extensions. eth0 no wireless extensions. wlan1 IEEE 802.11bgn ESSID:off/any Mode:Managed Access Point: Not-Associated Tx-Power=0 dBm Retry long limit:7 RTS thr:off Fragment thr:off Encryption key:off Power Management:off myuser@adri1:~$ lsmod | grep "ath9k" ath9k 116549 0 mac80211 461161 3 rt2x00usb,rt2x00lib,ath9k ath9k_common 13783 1 ath9k ath9k_hw 376155 2 ath9k,ath9k_common ath 19187 3 ath9k,ath9k_common,ath9k_hw cfg80211 175375 4 rt2x00lib,ath9k,mac80211,ath myuser@adri1:~$ iwlist scan wlan0 Failed to read scan data : Network is down lo Interface doesn't support scanning. eth0 Interface doesn't support scanning. wlan1 Failed to read scan data : Network is down myuser@adri1:~$ lsb_release -d Description: Ubuntu 12.10 myuser@adri1:~$ uname -mr 3.5.0-17-generic i686 ![Schizophrenic Ubuntu](http://www.amisdurailhalanzy.be/Screenshot%20from%202012-10-25%2013:19:54.png) Any help much appreciated... Thanks, Philippe

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  • How to use correctly the comments in C/++

    - by Lucio
    I'm learning to program in C and in my stage, the best form to use correctly the comments is writing good comments from the beginning. As the comments are not just for that one understands better the code but others too, I want to know the views of all of you to reach a consensus. So what I want is that the most experienced users edit the following code as you please. (If it's unnecessary, delete it; If it's wrong, correct it; If needed, add more) Thus there'll be multiple answers with different syntax and the responses with the most votes will be taken as referring when commenting. The code to copy, paste and edit to your pleasure is: (And I remark again, just import the comments, not the code) /* This programs find 1 number in 1 file. The file is binary type and has integers in series. The number is integer type and it's entered from the keyboard. When finished the program, a poster will show the results: Saying if the number is in the file or not. */ #include <stdio.h> //FUNCTION 1 //Open file 'path' and closes it. void openf(char path[]) { int num; //Read from Keyboard a Number and it save it into 'num' var printf("Ready for read number.\n\nNumber --> "); fflush(stdin); scanf("%d",&num); //Open file 'path' in READ mode FILE *fvar; fvar=fopen(path,"rb"); //IF error happens when open file, exit of function if (fvar==NULL) { printf("ERROR while open file %s in read mode.",path); exit(1); } /*Verify the result of 'funct' function IF TRUE, 'num' it's in the file*/ if (funct(path,fvar,num)) printf("The number %d it is in the file %s.",num,path); else printf("The number %d it is not in the file %s.",num,path); fclose(fvar); } /*FUNCTION 2 It is a recursive function. Reads number by number until the file is empty or the number is found. Parameters received: 'path' -> Directory file 'fvar' -> Pointer file 'num' -> Number to compare */ int funct(char path[],FILE *fvar,int num) { int compare; //FALSE condition when the pointer reaches the end if (fread(&compare,sizeof(int),1,fvar)>0) /*TRUE condition when the number readed is iqual that 'num' ELSE will go to the function itself*/ if (compare!=num) funct(path,fvar,num); else return 1; else return 0; } int main(int argc, char **argv) { char path[30]="file.bin"; //Direction of the file to process openf(path); //Function with algorithm return 0; }

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  • Seven Random Thoughts on JavaOne

    - by HecklerMark
    As most people reading this blog may know, last week was JavaOne. There are a lot of summary/recap articles popping up now, and while I didn't want to just "add to pile", I did want to share a few observations. Disclaimer: I am an Oracle employee, but most of these observations are either externally verifiable or based upon a collection of opinions from Oracle and non-Oracle attendees alike. Anyway, here are a few take-aways: The Java ecosystem is alive and well, with a breadth and depth that is impossible to adequately describe in a short post...or a long post, for that matter. If there is any one area within the Java language or JVM that you would like to - or need to - know more about, it's well-represented at J1. While there are several IDEs that are used to great effect by the developer community, NetBeans is on a roll. I lost count how many sessions mentioned or used NetBeans, but it was by far the dominant IDE in use at J1. As a recent re-convert to NetBeans, I wasn't surprised others liked it so well, only how many. OpenJDK, OpenJFX, etc. Many developers were understandably concerned with the change of sponsorship/leadership when Java creator and longtime steward Sun Microsystems was acquired by Oracle. The read I got from attendees regarding Oracle's stewardship was almost universally positive, and the push for "openness" is deep and wide within the current Java environs. Few would probably have imagined it to be this good, this soon. Someone observed that "Larry (Ellison) is competitive, and he wants to be the best...so if he wants to have a community, it will be the best community on the planet." Like any company, Oracle is bound to make missteps, but leadership seems to be striking an excellent balance between embracing open efforts and innovating in competitive paid offerings. JavaFX (2.x) isn't perfect or comprehensive, but a great many people (myself included) see great potential, are developing for it, and are really excited about where it is and where it may be headed. This is another part of the Java ecosystem that has impressive depth for being so new (JavaFX 1.x aside). If you haven't kicked the tires yet, give it a try! You'll be surprised at how capable and versatile it is, and you'll probably catch yourself smiling while coding again.  :-) JavaEE is everywhere. Not exactly a newsflash, but there is a lot of buzz around EE still/again/anew. Sessions ranged from updated component specs/technologies to Websockets/HTML5, from frameworks to profiles and application servers. Programming "server-side" Java isn't confined to the server (as you no doubt realize), and if you still consider JavaEE a cumbersome beast, you clearly haven't been using the last couple of versions. Download GlassFish or the WebLogic Zip distro (or another JavaEE 6 implementation) and treat yourself. JavaOne is not inexpensive, but to paraphrase an old saying, "If you think that's expensive, you should try ignorance." :-) I suppose it's possible to attend J1 and learn nothing, but you'd have to really work at it! Attending even a single session is bound to expand your horizons and make you approach your code, your problem domain, differently...even if it's a session about something you already know quite well. The various presenters offer vastly different perspectives and challenge you to re-think your own approach(es). And finally, if you think the scheduled sessions are great - and make no mistake, most are clearly outstanding - wait until you see what you pick up from what I like to call the "hallway sessions". Between the presentations, people freely mingle in the hallways, go to lunch and dinner together, and talk. And talk. And talk. Ideas flow freely, sparking other ideas and the "crowdsourcing" of knowledge in a way that is hard to imagine outside of a conference of this magnitude. Consider this the "GO" part of a "BOGO" (Buy One, Get One) offer: you buy the ticket to the "structured" part of JavaOne and get the hallway sessions at no additional charge. They're really that good. If you weren't able to make it to JavaOne this year, you can still watch/listen to the sessions online by visiting the JavaOne course catalog and clicking the media link(s) in the right column - another demonstration of Oracle's commitment to the Java community. But make plans to be there next year to get the full benefit! You'll be glad you did. All the best,Mark P.S. - I didn't mention several other exciting developments in areas like the embedded space and the "internet of things" (M2M), robotics, optimization, and the cloud (among others), but I think you get the idea. JavaOne == brainExpansion;  Hope to see you there next year!

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  • Javascript A* path finding ENEMY MOVEMENT in 3D environment

    - by faiz
    iam trying to implement pathfinding algorithm using PATHFINDING.JS in 3D world using webgl. iam have made a matrix of 200x200. and placed my enemy(swat) in it .iam confused in implmenting the path. i have tried implementing the path by compparing the value of each array value with swat's position . it works ! but ** THE ENEMY KEEPS GOING FROM THE UNWALKABLE AREA OF MY MATRIX....like the enemy should not move from 119,100(x=119,z=100) but its moving from that co-ordinate too ..... can any one help me out in this regard .. *prob facing :* enemy (swat character keeps moving from the wall /unwalkable area) wanted solution : enemy does not move from the unwalkable path.. ** function draw() { grid = new PF.Grid(200, 200); grid.setWalkableAt( 119,100, false); grid.setWalkableAt( 107,100, false); grid.setWalkableAt( 103,104, false); grid.setWalkableAt( 103,100, false); grid.setWalkableAt( 135,100, false); grid.setWalkableAt( 103,120, false); grid.setWalkableAt( 103,112, false); grid.setWalkableAt( 127,100, false); grid.setWalkableAt( 123,100, false); grid.setWalkableAt( 139,100, false); grid.setWalkableAt( 103,124, false); grid.setWalkableAt( 103,128, false); grid.setWalkableAt( 115,100, false); grid.setWalkableAt( 131,100, false); grid.setWalkableAt( 103,116, false); grid.setWalkableAt( 103,108, false); grid.setWalkableAt( 111,100, false); grid.setWalkableAt( 103,132, false); finder = new PF.AStarFinder(); f1=Math.abs(first_person_controller.position.x); f2=Math.abs(first_person_controller.position.z); ff1=Math.round(f1); ff2=Math.round(f2); s1=Math.abs(swat.position.x); s2=Math.abs(swat.position.z); ss1=Math.round(s1); ss2=Math.round(s1); path = finder.findPath(ss1,ss2,ff1,ff2, grid); size=path.length-1; Ai(); } function Ai(){ if (i<size) { if (swat.position.x >= path[i][0]) { swat.position.x -= 0.3; if(Math.floor(swat.position.x) == path[i][0]) { i=i+1; } } else if(swat.position.x <= path[i][0]) { swat.position.x += 0.3; if(Math.floor(swat.position.x) == path[i][0]) { i=i+1; } } } if (j<size) { if((Math.abs(swat.position.z)) >= path[j][1]) { swat.position.z -= 0.3; if(Math.floor(Math.abs(swat.position.z)) == path[j][1]) { j=j+1; } } else if((Math.abs(swat.position.z)) <= path[j][1]) { swat.position.z += 0.3; if(Math.floor(Math.abs(swat.position.z)) == path[j][1]) { j=j+1; } } } }

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  • YouTube Scalability Lessons

    - by Bertrand Matthelié
    @font-face { font-family: "Arial"; }@font-face { font-family: "Courier New"; }@font-face { font-family: "Wingdings"; }@font-face { font-family: "Calibri"; }@font-face { font-family: "Cambria"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman"; }h2 { margin: 12pt 0cm 3pt; page-break-after: avoid; font-size: 14pt; font-family: "Times New Roman"; font-style: italic; }a:link, span.MsoHyperlink { color: blue; text-decoration: underline; }a:visited, span.MsoHyperlinkFollowed { color: purple; text-decoration: underline; }span.Heading2Char { font-family: Calibri; font-weight: bold; font-style: italic; }div.Section1 { page: Section1; }ol { margin-bottom: 0cm; }ul { margin-bottom: 0cm; } Very interesting blog post by Todd Hoff at highscalability.com presenting “7 Years of YouTube Scalability Lessons in 30 min” based on a presentation from Mike Solomon, one of the original engineers at YouTube: …. The key takeaway away of the talk for me was doing a lot with really simple tools. While many teams are moving on to more complex ecosystems, YouTube really does keep it simple. They program primarily in Python, use MySQL as their database, they’ve stuck with Apache, and even new features for such a massive site start as a very simple Python program. That doesn’t mean YouTube doesn’t do cool stuff, they do, but what makes everything work together is more a philosophy or a way of doing things than technological hocus pocus. What made YouTube into one of the world’s largest websites? Read on and see... Stats @font-face { font-family: "Arial"; }@font-face { font-family: "Cambria"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; } 4 billion Views a day 60 hours of video is uploaded every minute 350+ million devices are YouTube enabled Revenue double in 2010 The number of videos has gone up 9 orders of magnitude and the number of developers has only gone up two orders of magnitude. 1 million lines of Python code Stack @font-face { font-family: "Arial"; }@font-face { font-family: "Cambria"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; } Python - most of the lines of code for YouTube are still in Python. Everytime you watch a YouTube video you are executing a bunch of Python code. Apache - when you think you need to get rid of it, you don’t. Apache is a real rockstar technology at YouTube because they keep it simple. Every request goes through Apache. Linux - the benefit of Linux is there’s always a way to get in and see how your system is behaving. No matter how bad your app is behaving, you can take a look at it with Linux tools like strace and tcpdump. MySQL - is used a lot. When you watch a video you are getting data from MySQL. Sometime it’s used a relational database or a blob store. It’s about tuning and making choices about how you organize your data. Vitess- a  new project released by YouTube, written in Go, it’s a frontend to MySQL. It does a lot of optimization on the fly, it rewrites queries and acts as a proxy. Currently it serves every YouTube database request. It’s RPC based. Zookeeper - a distributed lock server. It’s used for configuration. Really interesting piece of technology. Hard to use correctly so read the manual Wiseguy - a CGI servlet container. Spitfire - a templating system. It has an abstract syntax tree that let’s them do transformations to make things go faster. Serialization formats - no matter which one you use, they are all expensive. Measure. Don’t use pickle. Not a good choice. Found protocol buffers slow. They wrote their own BSON implementation, which is 10-15 time faster than the one you can download. ...Contiues. Read the blog Watch the video

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  • Give a session on C++ AMP – here is how

    - by Daniel Moth
    Ever since presenting on C++ AMP at the AMD Fusion conference in June, then the Gamefest conference in August, and the BUILD conference in September, I've had numerous requests about my material from folks that want to re-deliver the same session. The C++ AMP session I put together has evolved over the 3 presentations to its final form that I used at BUILD, so that is the one I recommend you base yours on. Please get the slides and the recording from channel9 (I'll refer to slide numbers below). This is how I've been presenting the C++ AMP session: Context (slide 3, 04:18-08:18) Start with a demo, on my dual-GPU machine. I've been using the N-Body sample (for VS 11 Developer Preview). (slide 4) Use an nvidia slide that has additional examples of performance improvements that customers enjoy with heterogeneous computing. (slide 5) Talk a bit about the differences today between CPU and GPU hardware, leading to the fact that these will continue to co-exist and that GPUs are great for data parallel algorithms, but not much else today. One is a jack of all trades and the other is a number cruncher. (slide 6) Use the APU example from amd, as one indication that the hardware space is still in motion, emphasizing that the C++ AMP solution is a data parallel API, not a GPU API. It has a future proof design for hardware we have yet to see. (slide 7) Provide more meta-data, as blogged about when I first introduced C++ AMP. Code (slide 9-11) Introduce C++ AMP coding with a simplistic array-addition algorithm – the slides speak for themselves. (slide 12-13) index<N>, extent<N>, and grid<N>. (Slide 14-16) array<T,N>, array_view<T,N> and comparison between them. (Slide 17) parallel_for_each. (slide 18, 21) restrict. (slide 19-20) actual restrictions of restrict(direct3d) – the slides speak for themselves. (slide 22) bring it altogether with a matrix multiplication example. (slide 23-24) accelerator, and accelerator_view. (slide 26-29) Introduce tiling incl. tiled matrix multiplication [tiling probably deserves a whole session instead of 6 minutes!]. IDE (slide 34,37) Briefly touch on the concurrency visualizer. It supports GPU profiling, but enhancements specific to C++ AMP we hope will come at the Beta timeframe, which is when I'll be spending more time talking about it. (slide 35-36, 51:54-59:16) Demonstrate the GPU debugging experience in VS 11. Summary (slide 39) Re-iterate some of the points of slide 7, and add the point that the C++ AMP spec will be open for other compiler vendors to implement, even on other platforms (in fact, Microsoft is actively working on that). (slide 40) Links to content – see slide – including where all your questions should go: http://social.msdn.microsoft.com/Forums/en/parallelcppnative/threads.   "But I don't have time for a full blown session, I only need 2 (or just 1, or 3) C++ AMP slides to use in my session on related topic X" If all you want is a small number of slides, you can take some from the session above and customize them. But because I am so nice, I have created some slides for you, including talking points in the notes section. Download them here. Comments about this post by Daniel Moth welcome at the original blog.

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  • Octree subdivision problem

    - by ChaosDev
    Im creating octree manually and want function for effectively divide all nodes and their subnodes - For example - I press button and subnodes divided - press again - all subnodes divided again. Must be like - 1 - 8 - 64. The problem is - i dont understand how organize recursive loops for that. OctreeNode in my unoptimized implementation contain pointers to subnodes(childs),parent,extra vector(contains dublicates of child),generation info and lots of information for drawing. class gOctreeNode { //necessary fields gOctreeNode* FrontBottomLeftNode; gOctreeNode* FrontBottomRightNode; gOctreeNode* FrontTopLeftNode; gOctreeNode* FrontTopRightNode; gOctreeNode* BackBottomLeftNode; gOctreeNode* BackBottomRightNode; gOctreeNode* BackTopLeftNode; gOctreeNode* BackTopRightNode; gOctreeNode* mParentNode; std::vector<gOctreeNode*> m_ChildsVector; UINT mGeneration; bool mSplitted; bool isSplitted(){return m_Splitted;} .... //unnecessary fields }; DivideNode of Octree class fill these fields, set mSplitted to true, and prepare for correctly drawing. Octree contains basic nodes(m_nodes). Basic node can be divided, but now I want recursivly divide already divided basic node with 8 subnodes. So I write this function. void DivideAllChildCells(int ix,int ih,int id) { std::vector<gOctreeNode*> nlist; std::vector<gOctreeNode*> dlist; int index = (ix * m_Height * m_Depth) + (ih * m_Depth) + (id * 1);//get index of specified node gOctreeNode* baseNode = m_nodes[index].get(); nlist.push_back(baseNode->FrontTopLeftNode); nlist.push_back(baseNode->FrontTopRightNode); nlist.push_back(baseNode->FrontBottomLeftNode); nlist.push_back(baseNode->FrontBottomRightNode); nlist.push_back(baseNode->BackBottomLeftNode); nlist.push_back(baseNode->BackBottomRightNode); nlist.push_back(baseNode->BackTopLeftNode); nlist.push_back(baseNode->BackTopRightNode); bool cont = true; UINT d = 0;//additional recursive loop param (?) UINT g = 0;//additional recursive loop param (?) LoopNodes(d,g,nlist,dlist); //Divide resulting nodes for(UINT i = 0; i < dlist.size(); i++) { DivideNode(dlist[i]); } } And now, back to the main question,I present LoopNodes, which must do all work for giving dlist nodes for splitting. void LoopNodes(UINT& od,UINT& og,std::vector<gOctreeNode*>& nlist,std::vector<gOctreeNode*>& dnodes) { //od++;//recursion depth bool f = false; //pass through childs for(UINT i = 0; i < 8; i++) { if(nlist[i]->isSplitted())//if node splitted and have childs { //pass forward through tree for(UINT j = 0; j < 8; j++) { nlist[j] = nlist[j]->m_ChildsVector[j];//set pointers to these childs } LoopNodes(od,og,nlist,dnodes); } else //if no childs { //add to split vector dnodes.push_back(nlist[i]); } } } This version of loop nodes works correctly for 2(or 1?) generations after - this will not divide neightbours nodes, only some corners. I need correct algorithm. Screenshot All I need - is correct version of LoopNodes, which can add all nodes for DivideNode.

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  • Asynchrony in C# 5 (Part I)

    - by javarg
    I’ve been playing around with the new Async CTP preview available for download from Microsoft. It’s amazing how language trends are influencing the evolution of Microsoft’s developing platform. Much effort is being done at language level today than previous versions of .NET. In these post series I’ll review some major features contained in this release: Asynchronous functions TPL Dataflow Task based asynchronous Pattern Part I: Asynchronous Functions This is a mean of expressing asynchronous operations. This kind of functions must return void or Task/Task<> (functions returning void let us implement Fire & Forget asynchronous operations). The two new keywords introduced are async and await. async: marks a function as asynchronous, indicating that some part of its execution may take place some time later (after the method call has returned). Thus, all async functions must include some kind of asynchronous operations. This keyword on its own does not make a function asynchronous thought, its nature depends on its implementation. await: allows us to define operations inside a function that will be awaited for continuation (more on this later). Async function sample: Async/Await Sample async void ShowDateTimeAsync() {     while (true)     {         var client = new ServiceReference1.Service1Client();         var dt = await client.GetDateTimeTaskAsync();         Console.WriteLine("Current DateTime is: {0}", dt);         await TaskEx.Delay(1000);     } } The previous sample is a typical usage scenario for these new features. Suppose we query some external Web Service to get data (in this case the current DateTime) and we do so at regular intervals in order to refresh user’s UI. Note the async and await functions working together. The ShowDateTimeAsync method indicate its asynchronous nature to the caller using the keyword async (that it may complete after returning control to its caller). The await keyword indicates the flow control of the method will continue executing asynchronously after client.GetDateTimeTaskAsync returns. The latter is the most important thing to understand about the behavior of this method and how this actually works. The flow control of the method will be reconstructed after any asynchronous operation completes (specified with the keyword await). This reconstruction of flow control is the real magic behind the scene and it is done by C#/VB compilers. Note how we didn’t use any of the regular existing async patterns and we’ve defined the method very much like a synchronous one. Now, compare the following code snippet  in contrast to the previuous async/await: Traditional UI Async void ComplicatedShowDateTime() {     var client = new ServiceReference1.Service1Client();     client.GetDateTimeCompleted += (s, e) =>     {         Console.WriteLine("Current DateTime is: {0}", e.Result);         client.GetDateTimeAsync();     };     client.GetDateTimeAsync(); } The previous implementation is somehow similar to the first shown, but more complicated. Note how the while loop is implemented as a chained callback to the same method (client.GetDateTimeAsync) inside the event handler (please, do not do this in your own application, this is just an example).  How it works? Using an state workflow (or jump table actually), the compiler expands our code and create the necessary steps to execute it, resuming pending operations after any asynchronous one. The intention of the new Async/Await pattern is to let us think and code as we normally do when designing and algorithm. It also allows us to preserve the logical flow control of the program (without using any tricky coding patterns to accomplish this). The compiler will then create the necessary workflow to execute operations as the happen in time.

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  • disks not ready in array causes mdadm to force initramfs shell

    - by RaidPinata
    Okay, this is starting to get pretty frustrating. I've read most of the other answers on this site that have anything to do with this issue but I'm still not getting anywhere. I have a RAID 6 array with 10 devices and 1 spare. The OS is on a completely separate device. At boot only three of the 10 devices in the raid are available, the others become available later in the boot process. Currently, unless I go through initramfs I can't get the system to boot - it just hangs with a blank screen. When I do boot through recovery (initramfs), I get a message asking if I want to assemble the degraded array. If I say no and then exit initramfs the system boots fine and my array is mounted exactly where I intend it to. Here are the pertinent files as near as I can tell. Ask me if you want to see anything else. # mdadm.conf # # Please refer to mdadm.conf(5) for information about this file. # # by default (built-in), scan all partitions (/proc/partitions) and all # containers for MD superblocks. alternatively, specify devices to scan, using # wildcards if desired. #DEVICE partitions containers # auto-create devices with Debian standard permissions # CREATE owner=root group=disk mode=0660 auto=yes # automatically tag new arrays as belonging to the local system HOMEHOST <system> # instruct the monitoring daemon where to send mail alerts MAILADDR root # definitions of existing MD arrays # This file was auto-generated on Tue, 13 Nov 2012 13:50:41 -0700 # by mkconf $Id$ ARRAY /dev/md0 level=raid6 num-devices=10 metadata=1.2 spares=1 name=Craggenmore:data UUID=37eea980:24df7b7a:f11a1226:afaf53ae Here is fstab # /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> # / was on /dev/sdc2 during installation UUID=3fa1e73f-3d83-4afe-9415-6285d432c133 / ext4 errors=remount-ro 0 1 # swap was on /dev/sdc3 during installation UUID=c4988662-67f3-4069-a16e-db740e054727 none swap sw 0 0 # mount large raid device on /data /dev/md0 /data ext4 defaults,nofail,noatime,nobootwait 0 0 output of cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid6 sda[0] sdd[10](S) sdl[9] sdk[8] sdj[7] sdi[6] sdh[5] sdg[4] sdf[3] sde[2] sdb[1] 23441080320 blocks super 1.2 level 6, 512k chunk, algorithm 2 [10/10] [UUUUUUUUUU] unused devices: <none> Here is the output of mdadm --detail --scan --verbose ARRAY /dev/md0 level=raid6 num-devices=10 metadata=1.2 spares=1 name=Craggenmore:data UUID=37eea980:24df7b7a:f11a1226:afaf53ae devices=/dev/sda,/dev/sdb,/dev/sde,/dev/sdf,/dev/sdg,/dev/sdh,/dev/sdi,/dev/sdj,/dev/sdk,/dev/sdl,/dev/sdd Please let me know if there is anything else you think might be useful in troubleshooting this... I just can't seem to figure out how to change the boot process so that mdadm waits until the drives are ready to build the array. Everything works just fine if the drives are given enough time to come online. edit: changed title to properly reflect situation

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  • The gestures of Windows 8 (Consumer preview): part 2, More about Search

    - by Laurent Bugnion
    This is part 2 of a multipart blog post about the gestures and shortcuts in Windows 8 consumer preview. Part 1 can be found here! More about the Search charm In the first installment of this series, we talked about the charms and mentioned a few gestures to display the Search charm. Search is a very central and powerful feature in Windows 8, and allows you to search in Apps, Settings, Files and within Metro applications that support the Search contract. There are a few cool features around the Search, and especially the applications associated to it. I already mentioned the keyboard shortcuts you can use: Win-C shows the Charms bar (same as swiping from the right bevel towards the center of the screen). Win-Q open the Search fly out with Apps preselected. Win-W open the Search fly out with Settings preselected. Win-F open the Search fly out with Files preselected. Searching in Metro apps In addition to these three search domains, you can also search a Metro app, as long as it supports the Search contract (check this Build video to learn more about the Search contract). These apps show up in the Search flyout as shown here: Notice the list of apps below the Files button? That’s what we are talking about. First of all, the list order changes when you search in some applications. For instance, in the image above, I had used the Store with the Search charm. This is why the store shows up as the first app. I am not 100% what algorithm is used here (sorting according to number of searches is my guess), but try it out and try to figure it out Applications that have never been searched are sorted alphabetically. Does it mean we will see cool app names like ___AAA_MyCoolApp? I certainly hope not!! Pinning You can also pin often used apps to the Search flyout. To pin an app with the mouse, right click on it in the Search flyout and select Pin from the context menu. With the keyboard, use the arrow keys to go down to the selected app, and then open the context menu. With the finger, simply tap and hold until you see a semi transparent rectangle indicating that the context menu will be shown, then release. The context menu opens up and you can select Pin. Pin context menu Pinned apps Unpinning, Hiding Using the same technique as for pinning here above, you can also unpin a pinned application. Finally, you can also choose to hide an app from the Search flyout altogether. This is a convenient way to clean up and make it easy to find stuff. Note: At this point, I am not sure how to re-add a hidden app to the Search flyout. If anyone knows, please mention it in the comments, thanks! Reordering You can also reorder pinned apps. To do this, with the finger, tap, hold and pull the app to the side, then pull it vertically to reorder it. You can also reorder with the mouse, simply by clicking on an app and pulling it vertically to the place you want to put it. I don’t think there is a way to do that with the keyboard though. That’s it for now More gestures will follow in a next installment! Have fun with Windows 8   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • It happens only at Devoxx ...

    - by arungupta
    After attending several Java conferences world wide, this was my very first time at Devoxx. Here are some items I found that happens only at Devoxx ... Pioneers of theater-style seating - This not only provides comfortable seating for each attendee but the screens are very clearly visible to everybody in the room. Intellectual level of attendees is very high - Read more explanation on the Java EE 6 lab blog. In short, a lab, 1/3 of the content delivered at Devoxx 2011, could not be completed at other developer days in more than 1/3 the time. Snack box for lunches - Even though this suits well to the healthy lifestyle of multiple-snacks-during-a-day style but leaves attendees hungry sooner in the day. The longer breaks before the next snack in the evening does not help at all. Fortunately, Azure cupcakes and Android ice creams turned out to be handy. I finally carried my own apple :-) Wrist band instead of lanyard - The good part about this is that once tied to your hand then you are less likely to forget in your room. But OTOH you are a pretty much a branded conference attendee all through out the city. It was cost effective as it costed 20c as opposed to 1 euro for the lanyard. Live streaming from theater #8 (the biggest room) on parleys.com All talks recorded and released on parleys.com over next year. This allows attendees to not to miss any session and watch replay at their own leisure. Stephan promised to start sharing the sessions by mid December this year. No need to pre-register for a session - This is true for most of the conferences but bigger rooms (+ overflow room for key sessions) provide sufficient space for all those who want to attend the session. And of course all sessions are available on parleys.com anyway! Community votes on whiteboard - Devoxx attendees gets a chance to vote on topics ranging from their favorite non-Java language, operating system, or love from Oracle. Captured pictures at the end of Day 2 are shown below. Movie on the last but one night - This year it was The Adventures of Tintin and was lots of fun. Fries with mayo - This is a typical Belgian thing. Guys going in ladies room to avoid the long queues ... wow! Tweet wall everywhere and I mean literally everywhere, in rooms, hallways, front desk, and other places. The tweet picking algorithm was not very clear as I never saw my tweet appear on the wall ;-) You can also watch it at wall.devoxx.com. Cozy speaker dinner with great food and wine List of parallel and upcoming sessions displayed on the screen - This makes the information more explicit with the attendees. REST API with multiple mobile clients - This API is also used by some other conferences as well. And there always is iphone.devoxx.com. Steering committee members were recognized multiple times. The committee members were clearly identifiable wearing red hoodies. The wireless SSID was intuitive "Devoxx" but hidden to avoid some crap from Microsoft Windows. All of 9000 addresses were used up most of the times with each attendee having multiple devices. A 1 GB fibre optic cable was stretched to Metropolis to support the required network bandwidth. Stephan is already planning to upgrade the equipment and have a better infrastructure next year. Free water, soda, juice in a cooler Kinect connected to TV screens so that attendees can use their hands to browse through the list of sesssions. #devoxxblog, #devoxxwomen, #devoxxfrance, #devoxxgreat, #devoxxsuggestions And Devoxx attendees are called Devoxxians ... how cool is that ? :-) What other things do you think happen only at Devoxx ? And now the pictures from the community whiteboard: And a more complete album (including bigger pics of community votes) is available below:

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  • Oh no! My padding's invalid!

    - by Simon Cooper
    Recently, I've been doing some work involving cryptography, and encountered the standard .NET CryptographicException: 'Padding is invalid and cannot be removed.' Searching on StackOverflow produces 57 questions concerning this exception; it's a very common problem encountered. So I decided to have a closer look. To test this, I created a simple project that decrypts and encrypts a byte array: // create some random data byte[] data = new byte[100]; new Random().NextBytes(data); // use the Rijndael symmetric algorithm RijndaelManaged rij = new RijndaelManaged(); byte[] encrypted; // encrypt the data using a CryptoStream using (var encryptor = rij.CreateEncryptor()) using (MemoryStream encryptedStream = new MemoryStream()) using (CryptoStream crypto = new CryptoStream( encryptedStream, encryptor, CryptoStreamMode.Write)) { crypto.Write(data, 0, data.Length); encrypted = encryptedStream.ToArray(); } byte[] decrypted; // and decrypt it again using (var decryptor = rij.CreateDecryptor()) using (CryptoStream crypto = new CryptoStream( new MemoryStream(encrypted), decryptor, CryptoStreamMode.Read)) { byte[] decrypted = new byte[data.Length]; crypto.Read(decrypted, 0, decrypted.Length); } Sure enough, I got exactly the same CryptographicException when trying to decrypt the data even in this simple example. Well, I'm obviously missing something, if I can't even get this single method right! What does the exception message actually mean? What am I missing? Well, after playing around a bit, I discovered the problem was fixed by changing the encryption step to this: // encrypt the data using a CryptoStream using (var encryptor = rij.CreateEncryptor()) using (MemoryStream encryptedStream = new MemoryStream()) { using (CryptoStream crypto = new CryptoStream( encryptedStream, encryptor, CryptoStreamMode.Write)) { crypto.Write(data, 0, data.Length); } encrypted = encryptedStream.ToArray(); } Aaaah, so that's what the problem was. The CryptoStream wasn't flushing all it's data to the MemoryStream before it was being read, and closing the stream causes it to flush everything to the backing stream. But why does this cause an error in padding? Cryptographic padding All symmetric encryption algorithms (of which Rijndael is one) operates on fixed block sizes. For Rijndael, the default block size is 16 bytes. This means the input needs to be a multiple of 16 bytes long. If it isn't, then the input is padded to 16 bytes using one of the padding modes. This is only done to the final block of data to be encrypted. CryptoStream has a special method to flush this final block of data - FlushFinalBlock. Calling Stream.Flush() does not flush the final block, as you might expect. Only by closing the stream or explicitly calling FlushFinalBlock is the final block, with any padding, encrypted and written to the backing stream. Without this call, the encrypted data is 16 bytes shorter than it should be. If this final block wasn't written, then the decryption gets to the final 16 bytes of the encrypted data and tries to decrypt it as the final block with padding. The end bytes don't match the padding scheme it's been told to use, therefore it throws an exception stating what is wrong - what the decryptor expects to be padding actually isn't, and so can't be removed from the stream. So, as well as closing the stream before reading the result, an alternative fix to my encryption code is the following: // encrypt the data using a CryptoStream using (var encryptor = rij.CreateEncryptor()) using (MemoryStream encryptedStream = new MemoryStream()) using (CryptoStream crypto = new CryptoStream( encryptedStream, encryptor, CryptoStreamMode.Write)) { crypto.Write(data, 0, data.Length); // explicitly flush the final block of data crypto.FlushFinalBlock(); encrypted = encryptedStream.ToArray(); } Conclusion So, if your padding is invalid, make sure that you close or call FlushFinalBlock on any CryptoStream performing encryption before you access the encrypted data. Flush isn't enough. Only then will the final block be present in the encrypted data, allowing it to be decrypted successfully.

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  • #OOW 2012 : IaaS, Private Cloud, Multitenant Database, and X3H2M2

    - by Eric Bezille
    The title of this post is a summary of the 4 announcements made by Larry Ellison today, during the opening session of Oracle Open World 2012... To know what's behind X3H2M2, you will have to wait a little, as I will go in order, beginning with the IaaS - Infrastructure as a Service - announcement. Oracle IaaS goes Public... and Private... Starting in 2004 with Fusion development, Oracle Cloud was launch last year to provide not only SaaS Application, based on standard development, but also the underlying PaaS, required to build the specifics, and required interconnections between applications, in and outside of the Cloud. Still, to cover the end-to-end Cloud  Services spectrum, we had to provide an Infrastructure as a Service, leveraging our Servers, Storage, OS, and Virtualization Technologies, all "Engineered Together". This Cloud Infrastructure, was already available for our customers to build rapidly their own Private Cloud either on SPARC/Solaris or x86/Linux... The second announcement made today bring that proposition a big step further : for cautious customers (like Banks, or sensible industries) who would like to benefits from the Cloud value of "as a Service", but don't want their Data out in the Cloud... We propose to them to operate the same systems, Exadata, Exalogic & SuperCluster, that are providing our Public Cloud Infrastructure, behind their firewall, in a Private Cloud model. Oracle 12c Multitenant Database This is also a major announcement made today, on what's coming with Oracle Database 12c : the ability to consolidate multiple databases with no extra additional  cost especially in terms of memory needed on the server node, which is often THE consolidation limiting factor. The principle could be compare to Solaris Zones, where, you will have a Database Container, who is "owning" the memory and Database background processes, and "Pluggable" Database in this Database Container. This particular feature is a strong compelling event to evaluate rapidly Oracle Database 12c once it will be available, as this is major step forward into true Database consolidation with Multitenancy on a shared (optimized) infrastructure. X3H2M2, enabling the new Exadata X3 in-Memory Database Here we are :  X3H2M2 stands for X3 (the new version of Exadata announced also today) Heuristic Hierarchical Mass Memory, providing the capability to keep most if not all the Data in the memory cache hierarchy. Of course, this is the major software enhancement of the new X3 Exadata machine, but as this is a software, our current customers would be able to benefit from it on their existing systems by upgrading to the new release. But that' not the only thing that we did with X3, at the same time we have upgraded everything : the CPUs, adding more cores per server node (16 vs. 12, with the arrival of Intel E5 / Sandy Bridge), the memory with 512GB memory as well per node,  and the new Flash Fire card, bringing now up to 22 TB of Flash cache. All of this 4TB of RAM + 22TB of Flash being use cleverly not only for read but also for write by the X3H2M2 algorithm... making a very big difference compare to traditional storage flash extension. But what does those extra performances brings to you on an already very efficient system: double your performances compare to the fastest storage array on the market today (including flash) and divide you storage price x10 at the same time... Something to consider closely this days... Especially that we also announced the availability of a new Exadata X3-2 8th rack : a good starting point. As you have seen a major opening for this year again with true innovation. But that was not the only thing that we saw today, as before Larry's talk, Fujitsu did introduce more in deep the up coming new SPARC processor, that they are co-developing with us. And as such Andrew Mendelsohn - Senior Vice President Database Server Technologies came on stage to explain that the next step after I/O optimization for Database with Exadata, was to accelerate the Database at execution level by bringing functions in the SPARC processor silicium. All in all, to process more and more Data... The big theme of the day... and of the Oracle User Groups Conferences that were also happening today and where I had the opportunity to attend some interesting sessions on practical use cases of Big Data one in Finances and Fraud profiling and the other one on practical deployment of Oracle Exalytics for Data Analytics. In conclusion, one picture to try to size Oracle Open World ... and you can understand why, with such a rich content... and this only the first day !

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  • What Color is your Jetpack ?

    - by JoshReuben
    I’m a programmer, Im approaching 40, and I’m fairly decent at my job – I’ll keep doing what I’m doing for as long as they let me!   So what are your career options if you know how to code? A Programmer could be ..   An Algorithm developer Pros Interesting High barriers of entry, potential for startup competitive factor Cons Do you have the skill, qualifications? What are working conditions n this mystery niche ? micro-focus An Academic Pros Low pressure Job security – or is this an illusion ? Cons Low Pay Need a PhD A Software Architect Pros: strategic, rather than tactical Setting technology platform and high level vision You say how it should work, others have to figure out why its not working the way its supposed to ! broad view – you are paid to learn (how do you con people into paying for you to learn ??) Cons: Glorified developer – more often than not! competitive – everyone wants to do it ! loose touch with underlying tech in tough times, first guy to get the axe ! A Software Engineer Pros: interesting, always more to learn fun I can do it Fallback Cons: Nothing new under the sun – been there, done that Dealing with poor requirements, deadlines, other peoples code, overtime C#, XAML, Web - Low barriers of entry –> à race to the bottom A Team leader Pros: Setting code standards and proposing technology choices Cons: Glorified developer – more often than not! Inspecting other peoples code and debugging the problems they cannot fix Dealing with mugbies and prima donas Responsible for QA of others A Project Manager Pros No need for debugging other peoples code Cons Low barrier of entry High pressure Responsible for QA of others Loosing touch with technology A lot of bullshit meetings Have to be an asshole A Product Manager Pros No need for debugging other peoples code Learning new skillset of sales and marketing Cons Travel (I'm a family man) May need to know the bs details of an uninteresting product things I want to work with: AI, algorithms, Numerical Computing, Mathematica, C++ AMP – unfortunately, the work here is few & far between. VS & TFS Extensibility, DSLs (Workflow , Lightswitch), Code Generation – one day, code will write code ! Unity3D, WebGL – fun, fun, fun ! Modern Web – Knockout, SignalR, MVC, Node.Js ??? (tentative – I'll wait until things stabilize as this area is undergoing a pre-Cambrian explosion) Things I don’t want to work with: (but will if I'm asked to !) C# – same old, same old – not learning anything new here Old code – blech ! Environment with code & fix mentality , ad hoc requirements, excessive overtime Pc support, System administration – even after 20 years, people still ask you to do this sometimes ! debugging – my skills are just not there yet Oracle Old tech: VB 6, XSLT, WinForms, Net 3.51 or less Old style Web dev Information Systems: ASP.NET webforms, Reporting services / crystal reports, SQL Server CRUD with manual data layer, XAML MVVM – variations of the same concept, ad nauseaum. Low barriers of entry –> race to the bottom.  Metro – an elegant API coupled to a horrendous UX – I'll wait for market penetration viability before investing further in this.   Conclusion So if you are in a slump, take heart: Programming is a great career choice compared to every other job !

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  • Numerically stable(ish) method of getting Y-intercept of mouse position?

    - by Fraser
    I'm trying to unproject the mouse position to get the position on the X-Z plane of a ray cast from the mouse. The camera is fully controllable by the user. Right now, the algorithm I'm using is... Unproject the mouse into the camera to get the ray: Vector3 p1 = Vector3.Unproject(new Vector3(x, y, 0), 0, 0, width, height, nearPlane, farPlane, viewProj; Vector3 p2 = Vector3.Unproject(new Vector3(x, y, 1), 0, 0, width, height, nearPlane, farPlane, viewProj); Vector3 dir = p2 - p1; dir.Normalize(); Ray ray = Ray(p1, dir); Then get the Y-intercept by using algebra: float t = -ray.Position.Y / ray.Direction.Y; Vector3 p = ray.Position + t * ray.Direction; The problem is that the projected position is "jumpy". As I make small adjustments to the mouse position, the projected point moves in strange ways. For example, if I move the mouse one pixel up, it will sometimes move the projected position down, but when I move it a second pixel, the project position will jump back to the mouse's location. The projected location is always close to where it should be, but it does not smoothly follow a moving mouse. The problem intensifies as I zoom the camera out. I believe the problem is caused by numeric instability. I can make minor improvements to this by doing some computations at double precision, and possibly abusing the fact that floating point calculations are done at 80-bit precision on x86, however before I start micro-optimizing this and getting deep into how the CLR handles floating point, I was wondering if there's an algorithmic change I can do to improve this? EDIT: A little snooping around in .NET Reflector on SlimDX.dll: public static Vector3 Unproject(Vector3 vector, float x, float y, float width, float height, float minZ, float maxZ, Matrix worldViewProjection) { Vector3 coordinate = new Vector3(); Matrix result = new Matrix(); Matrix.Invert(ref worldViewProjection, out result); coordinate.X = (float) ((((vector.X - x) / ((double) width)) * 2.0) - 1.0); coordinate.Y = (float) -((((vector.Y - y) / ((double) height)) * 2.0) - 1.0); coordinate.Z = (vector.Z - minZ) / (maxZ - minZ); TransformCoordinate(ref coordinate, ref result, out coordinate); return coordinate; } // ... public static void TransformCoordinate(ref Vector3 coordinate, ref Matrix transformation, out Vector3 result) { Vector3 vector; Vector4 vector2 = new Vector4 { X = (((coordinate.Y * transformation.M21) + (coordinate.X * transformation.M11)) + (coordinate.Z * transformation.M31)) + transformation.M41, Y = (((coordinate.Y * transformation.M22) + (coordinate.X * transformation.M12)) + (coordinate.Z * transformation.M32)) + transformation.M42, Z = (((coordinate.Y * transformation.M23) + (coordinate.X * transformation.M13)) + (coordinate.Z * transformation.M33)) + transformation.M43 }; float num = (float) (1.0 / ((((transformation.M24 * coordinate.Y) + (transformation.M14 * coordinate.X)) + (coordinate.Z * transformation.M34)) + transformation.M44)); vector2.W = num; vector.X = vector2.X * num; vector.Y = vector2.Y * num; vector.Z = vector2.Z * num; result = vector; } ...which seems to be a pretty standard method of unprojecting a point from a projection matrix, however this serves to introduce another point of possible instability. Still, I'd like to stick with the SlimDX Unproject routine rather than writing my own unless it's really necessary.

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  • Optimizing drawing of cubes

    - by Christian Frantz
    After googling for hours I've come to a few conclusions, I need to either rewrite my whole cube class, or figure out how to use hardware instancing. I can draw up to 2500 cubes with little lag, but after that my fps drops. Is there a way I can use my class for hardware instancing? Or would I be better off rewriting my class for optimization? public class Cube { public GraphicsDevice device; public VertexBuffer cubeVertexBuffer; public Cube(GraphicsDevice graphicsDevice) { device = graphicsDevice; var vertices = new List<VertexPositionTexture>(); BuildFace(vertices, new Vector3(0, 0, 0), new Vector3(0, 1, 1)); BuildFace(vertices, new Vector3(0, 0, 1), new Vector3(1, 1, 1)); BuildFace(vertices, new Vector3(1, 0, 1), new Vector3(1, 1, 0)); BuildFace(vertices, new Vector3(1, 0, 0), new Vector3(0, 1, 0)); BuildFaceHorizontal(vertices, new Vector3(0, 1, 0), new Vector3(1, 1, 1)); BuildFaceHorizontal(vertices, new Vector3(0, 0, 1), new Vector3(1, 0, 0)); cubeVertexBuffer = new VertexBuffer(device, VertexPositionTexture.VertexDeclaration, vertices.Count, BufferUsage.WriteOnly); cubeVertexBuffer.SetData<VertexPositionTexture>(vertices.ToArray()); } private void BuildFace(List<VertexPositionTexture> vertices, Vector3 p1, Vector3 p2) { vertices.Add(BuildVertex(p1.X, p1.Y, p1.Z, 1, 0)); vertices.Add(BuildVertex(p1.X, p2.Y, p1.Z, 1, 1)); vertices.Add(BuildVertex(p2.X, p2.Y, p2.Z, 0, 1)); vertices.Add(BuildVertex(p2.X, p2.Y, p2.Z, 0, 1)); vertices.Add(BuildVertex(p2.X, p1.Y, p2.Z, 0, 0)); vertices.Add(BuildVertex(p1.X, p1.Y, p1.Z, 1, 0)); } private void BuildFaceHorizontal(List<VertexPositionTexture> vertices, Vector3 p1, Vector3 p2) { vertices.Add(BuildVertex(p1.X, p1.Y, p1.Z, 0, 1)); vertices.Add(BuildVertex(p2.X, p1.Y, p1.Z, 1, 1)); vertices.Add(BuildVertex(p2.X, p2.Y, p2.Z, 1, 0)); vertices.Add(BuildVertex(p1.X, p1.Y, p1.Z, 0, 1)); vertices.Add(BuildVertex(p2.X, p2.Y, p2.Z, 1, 0)); vertices.Add(BuildVertex(p1.X, p1.Y, p2.Z, 0, 0)); } private VertexPositionTexture BuildVertex(float x, float y, float z, float u, float v) { return new VertexPositionTexture(new Vector3(x, y, z), new Vector2(u, v)); } public void Draw(BasicEffect effect) { foreach (EffectPass pass in effect.CurrentTechnique.Passes) { pass.Apply(); device.SetVertexBuffer(cubeVertexBuffer); device.DrawPrimitives(PrimitiveType.TriangleList, 0, cubeVertexBuffer.VertexCount / 3); } } } The following class is a list that draws the cubes. public class DrawableList<T> : DrawableGameComponent { private BasicEffect effect; private ThirdPersonCam camera; private class Entity { public Vector3 Position { get; set; } public Matrix Orientation { get; set; } public Texture2D Texture { get; set; } } private Cube cube; private List<Entity> entities = new List<Entity>(); public DrawableList(Game game, ThirdPersonCam camera, BasicEffect effect) : base(game) { this.effect = effect; cube = new Cube(game.GraphicsDevice); this.camera = camera; } public void Add(Vector3 position, Matrix orientation, Texture2D texture) { entities.Add(new Entity() { Position = position, Orientation = orientation, Texture = texture }); } public override void Draw(GameTime gameTime) { foreach (var item in entities) { effect.VertexColorEnabled = false; effect.TextureEnabled = true; effect.Texture = item.Texture; Matrix center = Matrix.CreateTranslation(new Vector3(-0.5f, -0.5f, -0.5f)); Matrix scale = Matrix.CreateScale(1f); Matrix translate = Matrix.CreateTranslation(item.Position); effect.World = center * scale * translate; effect.View = camera.view; effect.Projection = camera.proj; effect.FogEnabled = true; effect.FogColor = Color.CornflowerBlue.ToVector3(); effect.FogStart = 1.0f; effect.FogEnd = 50.0f; cube.Draw(effect); } base.Draw(gameTime); } } } There are probably many reasons that my fps is so slow, but I can't seem to figure out how to fix it. I've looked at techcraft as well, but what I have is too specific to what I want the outcome to be to just rewrite everything from scratch

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  • CI tests to enforce specific development rules - good practice?

    - by KeithS
    The following is all purely hypothetical and any particular portion of it may or may not accurately describe real persons or situations, whether living, dead or just pretending. Let's say I'm a senior dev or architect in charge of a dev team working on a project. This project includes a security library for user authentication/authorization of the application under development. The library must be available for developers to edit; however, I wish to "trust but verify" that coders are not doing things that could compromise the security of the finished system, and because this isn't my only responsibility I want it to be done in an automated way. As one example, let's say I have an interface that represents a user which has been authenticated by the system's security library. The interface exposes basic user info and a list of things the user is authorized to do (so that the client app doesn't have to keep asking the server "can I do this?"), all in an immutable fashion of course. There is only one implementation of this interface in production code, and for the purposes of this post we can say that all appropriate measures have been taken to ensure that this implementation can only be used by the one part of our code that needs to be able to create concretions of the interface. The coders have been instructed that this interface and its implementation are sacrosanct and any changes must go through me. However, those are just words; the security library's source is open for editing by necessity. Any of my devs could decide that this secured, private, hash-checked implementation needs to be public so that they could do X, or alternately they could create their own implementation of this public interface in a different library, exposing the hashing algorithm that provides the secure checksum, in order to do Y. I may not be made aware of these changes so that I can beat the developer over the head for it. An attacker could then find these little nuggets in an unobfuscated library of the compiled product, and exploit it to provide fake users and/or falsely-elevated administrative permissions, bypassing the entire security system. This possibility keeps me awake for a couple of nights, and then I create an automated test that reflectively checks the codebase for types deriving from the interface, and fails if it finds any that are not exactly what and where I expect them to be. I compile this test into a project under a separate folder of the VCS that only I have rights to commit to, have CI compile it as an external library of the main project, and set it up to run as part of the CI test suite for user commits. Now, I have an automated test under my complete control that will tell me (and everyone else) if the number of implementations increases without my involvement, or an implementation that I did know about has anything new added or has its modifiers or those of its members changed. I can then investigate further, and regain the opportunity to beat developers over the head as necessary. Is this considered "reasonable" to want to do in situations like this? Am I going to be seen in a negative light for going behind my devs' backs to ensure they aren't doing something they shouldn't?

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