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• How Can I Improve This Card-Game AI?

  - by James Burgess

  Let me get this out there before anything else: this is a learning exercise for me. I am not a game developer by trade or hobby (at least, not seriously) and am purely delving into some AI- and 3D-related topics to broaden my horizons a bit. As part of the learning experience, I thought I'd have a go at developing a basic card game AI. I selected Pit as the card game I was going to attempt to emulate (specifically, the 'bull and bear' variation of the game as mentioned in the link above). Unfortunately, the rule-set that I'm used to playing with (an older version of the game) isn't described. The basics of it are: The number of commodities played with is equal to the number of players. The bull and bear cards are included. All but two players receive 8 cards, two receive 9 cards. A player can win the round with 7 + bull, 8, or 8 + bull (receiving double points). The bear is a penalty card. You can trade up to a maximum of 4 cards at a time. They must all be of the same type, but can optionally include the bull or bear (so, you could trade A, A, A, Bull - but not A, B, A, Bull). For those who have played the card game, it will probably have been as obvious to you as it was to me that given the nature of the game, gameplay would seem to resemble a greedy algorithm. With this in mind, I thought it might simplify my AI experience somewhat. So, here's what I've come up with for a basic AI player to play Pit... and I'd really just like any form of suggestion (from improvements to reading materials) relating to it. Here it is in something vaguely pseudo-code-ish ;) While AI does not hold 7 similar + bull, 8 similar, or 8 similar + bull, do: 1. Establish 'target' hand, by seeing which card AI holds the most of. 2. Prepare to trade next-most-numerous card type in a trade (max. held, or 4, whichever is fewer) 3. If holding the bear, add to (if trading <=3 cards) or replace in (if trading 4 cards) hand. 4. Offer cards for trade. 5. If cards are accepted for trade within X turns, continue (clearing 'failed card types'). Otherwise: a. If only one card remains in the trade, go to #6. Otherwise: i. Remove one non-penalty card from the trade. ii. Return to #5. 6. Add card type to temporary list of failed card types. 7. Repeat from #2 (excluding 'failed card types'). I'm aware this is likely to be a sub-optimal way of solving the problem, but that's why I'm posting this question. Are there any AI- or algorithm-related concepts that I've missed and should be incorporating to make a better AI? Additionally, what are the flaws with my AI at present (I'm well aware it's probably far from complete)? Thanks in advance!

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• Merge sort versus quick sort performance

  - by Giorgio

  I have implemented merge sort and quick sort using C (GCC 4.4.3 on Ubuntu 10.04 running on a 4 GB RAM laptop with an Intel DUO CPU at 2GHz) and I wanted to compare the performance of the two algorithms. The prototypes of the sorting functions are: void merge_sort(const char **lines, int start, int end); void quick_sort(const char **lines, int start, int end); i.e. both take an array of pointers to strings and sort the elements with index i : start <= i <= end. I have produced some files containing random strings with length on average 4.5 characters. The test files range from 100 lines to 10000000 lines. I was a bit surprised by the results because, even though I know that merge sort has complexity O(n log(n)) while quick sort is O(n^2), I have often read that on average quick sort should be as fast as merge sort. However, my results are the following. Up to 10000 strings, both algorithms perform equally well. For 10000 strings, both require about 0.007 seconds. For 100000 strings, merge sort is slightly faster with 0.095 s against 0.121 s. For 1000000 strings merge sort takes 1.287 s against 5.233 s of quick sort. For 5000000 strings merge sort takes 7.582 s against 118.240 s of quick sort. For 10000000 strings merge sort takes 16.305 s against 1202.918 s of quick sort. So my question is: are my results as expected, meaning that quick sort is comparable in speed to merge sort for small inputs but, as the size of the input data grows, the fact that its complexity is quadratic will become evident? Here is a sketch of what I did. In the merge sort implementation, the partitioning consists in calling merge sort recursively, i.e. merge_sort(lines, start, (start + end) / 2); merge_sort(lines, 1 + (start + end) / 2, end); Merging of the two sorted sub-array is performed by reading the data from the array lines and writing it to a global temporary array of pointers (this global array is allocate only once). After each merge the pointers are copied back to the original array. So the strings are stored once but I need twice as much memory for the pointers. For quick sort, the partition function chooses the last element of the array to sort as the pivot and scans the previous elements in one loop. After it has produced a partition of the type start ... {elements <= pivot} ... pivotIndex ... {elements > pivot} ... end it calls itself recursively: quick_sort(lines, start, pivotIndex - 1); quick_sort(lines, pivotIndex + 1, end); Note that this quick sort implementation sorts the array in-place and does not require additional memory, therefore it is more memory efficient than the merge sort implementation. So my question is: is there a better way to implement quick sort that is worthwhile trying out? If I improve the quick sort implementation and perform more tests on different data sets (computing the average of the running times on different data sets) can I expect a better performance of quick sort wrt merge sort? EDIT Thank you for your answers. My implementation is in-place and is based on the pseudo-code I have found on wikipedia in Section In-place version: function partition(array, 'left', 'right', 'pivotIndex') where I choose the last element in the range to be sorted as a pivot, i.e. pivotIndex := right. I have checked the code over and over again and it seems correct to me. In order to rule out the case that I am using the wrong implementation I have uploaded the source code on github (in case you would like to take a look at it). Your answers seem to suggest that I am using the wrong test data. I will look into it and try out different test data sets. I will report as soon as I have some results.

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• Drawing transparent glyphs on the HTML canvas

  - by Bertrand Le Roy

  The HTML canvas has a set of methods, createImageData and putImageData, that look like they will enable you to draw transparent shapes pixel by pixel. The data structures that you manipulate with these methods are pseudo-arrays of pixels, with four bytes per pixel. One byte for red, one for green, one for blue and one for alpha. This alpha byte makes one believe that you are going to be able to manage transparency, but that’s a lie. Here is a little script that attempts to overlay a simple generated pattern on top of a uniform background: var wrong = document.getElementById("wrong").getContext("2d"); wrong.fillStyle = "#ffd42a"; wrong.fillRect(0, 0, 64, 64); var overlay = wrong.createImageData(32, 32), data = overlay.data; fill(data); wrong.putImageData(overlay, 16, 16); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } where the fill method is setting the pixels in the lower-left half of the overlay to opaque red, and the rest to transparent black. And here’s how it renders: As you can see, the transparency byte was completely ignored. Or was it? in fact, what happens is more subtle. What happens is that the pixels from the image data, including their alpha byte, replaced the existing pixels of the canvas. So the alpha byte is not lost, it’s just that it wasn’t used by putImageData to combine the new pixels with the existing ones. This is in fact a clue to how to write a putImageData that works: we can first dump that image data into an intermediary canvas, and then compose that temporary canvas onto our main canvas. The method that we can use for this composition is drawImage, which works not only with image objects, but also with canvas objects. var right = document.getElementById("right").getContext("2d"); right.fillStyle = "#ffd42a"; right.fillRect(0, 0, 64, 64); var overlay = wrong.createImageData(32, 32), data = overlay.data; fill(data); var overlayCanvas = document.createElement("canvas"); overlayCanvas.width = overlayCanvas.height = 32; overlayCanvas.getContext("2d").putImageData(overlay, 0, 0); right.drawImage(overlayCanvas, 16, 16); And there is is, a version of putImageData that works like it should always have:

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• Old School Wizardry Tip: Batch File Comments

  - by jkauffman

  Johnny, the Endangered Keyboard-Driven Windows User Some of my proudest, obscure Windows tricks are losing their relevance. I know I’m not alone. Keyboard shortcuts are going the way of the dodo. I used to induce fearful awe by slapping Ctrl+Shift+Esc in front of the lowly, pedestrian Windows users. No windows key on the keyboard? No problem: Ctrl+Esc. No menu key on the keyboard: Shift+F10. I am also firmly planted in the habit of closing windows with the Alt+Space menu (Alt+Space, C); and I harbor a brooding, slow=growing list of programs that fail to support this correctly (that means you, Paint.NET). Every time a new version of windows comes out, the support for some of these minor time-saving habits get pared out. Will I complain publicly? Nope, I know my old ways should be axed to conserve precious design energy. In fact, I disapprove of fierce un-intuitiveness for the sake of alleged productivity. Like vim, for example. If you approach a program after being away for 5 years, having to recall encyclopedic knowledge is a flaw. The RTFM disciples have lost. Anyway, some of the items in my arsenal of goofy time-saving tricks are still relevant today. I wanted to draw attention to one that’s stood the test of time. Remember Batch Files? Yes, it’s true, batch files are fading faster than the world of print. But they're not dead yet. I still run into some situations where I opt to use batch files. They are still relevant for build processes, or just various development workflow tools. Sure, there’s powershell, but there’s that stupid Set-ExecutionPolicy speed bump standing in your way; can you really spare the time to A) hunt down that setting on all machines affected and/or B) make futile efforts to convince your coworkers/boss that the hassle was worth it? When possible, I prefer the batch file wild card. And whenever I return to batch files, I end up researching some of the unintuitive aspects such as parameters, quote handling, and ERRORLEVEL. But I never have to remember to use “REM” for comment lines, because there’s a cleaner way to do them! Double Colon For Eye-Friendly Comments Here is a very simple batch file, with pretty much minimal content: @ECHO OFF SETLOCAL REM This is a comment ECHO This batch file doesn’t do much If you code on a daily basis, this may be more suitable to your eyes: @ECHO OFF SETLOCAL :: This is a comment ECHO This batch file doesn’t do much Works great! I imagine I find it preferable due to the similarity to comments in other situations: // or ;  or # I’ve often make visual pseudo-line breaks in my code, and this colon-based syntax works wonders: @ECHO OFF SETLOCAL :: Do stuff ECHO Doing Stuff :::::::::::::::::::::::::::: :: Do more stuff ECHO This batch file doesn’t do much Not only is it more readable, but there’s a slight performance benefit. The batch file engine sees this as an invalid line label and immediately reads the following line. Use that fact to your advantage if this trick leads you into heated nerd debate. Two Pitfalls to Avoid Be aware of that there are a couple situations where this hack will fail you. It most likely won’t be a problem unless you’re getting really sophisticated with your batch files. Pitfall #1: Inline comments @ECHO OFF SETLOCAL IF EXIST C:\SomeFile.txt GOTO END ::This will fail :END Unfortunately, this fails. You can only have whitespace to the left of your comments. Pitfall #2: Code Blocks @ECHO OFF SETLOCAL IF EXIST C:\SomeFile.txt (         :: This will fail         ECHO HELLO ) Code blocks, such as if statements and for loops, cannot contain these comments. This is ultimately due to the fact that entire code blocks are processed as a single line. I originally learned this from Rob van der Woude’s site. He goes into more depth about the behavior of the pitfalls as well, if you are interested in further details. I hope this trick earns you serious geek rep!

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• Computing a normal matrix in conjunction with gluLookAt

  - by Chris Smith

  I have a hand-rolled camera class that converts yaw, pitch, and roll angles into a forward, side, and up vector suitable for calling gluLookAt. Using this camera class I can modify the model-view matrix to move about the 3D world just fine. However, I am having trouble when using this camera class (and associated model-view matrix) when trying to perform directional lighting in my vertex shader. The problem is that the light direction, (0, 1, 0) for example, is relative to where the 'camera is looking' and not the actual world coordinates. (Or is this eye coordinates vs. model coordinates?) I would like the light direction to be unaffected by the camera's viewing direction. For example, when the camera is looking down the Z axis the ground is lit correctly. However, if I point the camera straight at the ground, then it goes dark. This is (I think) because the light direction is parallel with the camera's 'up' vector which is perpendicular with the ground's normal vector. I tried computing the normal matrix without taking the camera's model view into account, but then none of my objects were rotated correctly. Sorry if this sounds vague. I suspect there is a straight forward answer, but I'm not 100% clear on how the normal matrix should be used for transforming vertex normals in my vertex shader. For reference, here is pseudo code for my rendering loop: pMatrix = new Matrix(); pMatrix = makePerspective(...) mvMatrix = new Matrix() camera.apply(mvMatrix); // Calls gluLookAt // Move the object into position. mvMatrix.translatev(position); mvMatrix.rotatef(rotation.x, 1, 0, 0); mvMatrix.rotatef(rotation.y, 0, 1, 0); mvMatrix.rotatef(rotation.z, 0, 0, 1); var nMatrix = new Matrix(); nMatrix.set(mvMatrix.get().getInverse().getTranspose()); // Set vertex shader uniforms. gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, new Float32Array(pMatrix.getFlattened())); gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, new Float32Array(mvMatrix.getFlattened())); gl.uniformMatrix4fv(shaderProgram.nMatrixUniform, false, new Float32Array(nMatrix.getFlattened())); // ... gl.drawElements(gl.TRIANGLES, this.vertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0); And the corresponding vertex shader: // Attributes attribute vec3 aVertexPosition; attribute vec4 aVertexColor; attribute vec3 aVertexNormal; // Uniforms uniform mat4 uMVMatrix; uniform mat4 uNMatrix; uniform mat4 uPMatrix; // Varyings varying vec4 vColor; // Constants const vec3 LIGHT_DIRECTION = vec3(0, 1, 0); // Opposite direction of photons. const vec4 AMBIENT_COLOR = vec4 (0.2, 0.2, 0.2, 1.0); float ComputeLighting() { vec4 transformedNormal = vec4(aVertexNormal.xyz, 1.0); transformedNormal = uNMatrix * transformedNormal; float base = dot(normalize(transformedNormal.xyz), normalize(LIGHT_DIRECTION)); return max(base, 0.0); } void main(void) { gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0); float lightWeight = ComputeLighting(); vColor = vec4(aVertexColor.xyz * lightWeight, 1.0) + AMBIENT_COLOR; } Note that I am using WebGL, so if the anser is use glFixThisProblem(...) any pointers on how to re-implement that on WebGL if missing would be appreciated.

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• How the SPARC T4 Processor Optimizes Throughput Capacity: A Case Study

  - by Ruud

  This white paper demonstrates the architected latency hiding features of Oracle’s UltraSPARC T2+ and SPARC T4 processors That is the first sentence from this technical white paper, but what does it exactly mean? Let's consider a very simple example, the computation of a = b + c. This boils down to the following (pseudo-assembler) instructions that need to be executed: load @b, r1 load @c, r2 add r1,r2,r3 store r3, @a The first two instructions load variables b and c from an address in memory (here symbolized by @b and @c respectively). These values go into registers r1 and r2. The third instruction adds the values in r1 and r2. The result goes into register r3. The fourth instruction stores the contents of r3 into the memory address symbolized by @a. If we're lucky, both b and c are in a nearby cache and the load instructions only take a few processor cycles to execute. That is the good case, but what if b or c, or both, have to come from very far away? Perhaps both of them are in the main memory and then it easily takes hundreds of cycles for the values to arrive in the registers. Meanwhile the processor is doing nothing and simply waits for the data to arrive. Actually, it does something. It burns cycles while waiting. That is a waste of time and energy. Why not use these cycles to execute instructions from another application or thread in case of a parallel program? That is exactly what latency hiding on the SPARC T-Series processors does. It is a hardware feature totally transparent to the user and application. As soon as there is a delay in the execution, the hardware uses these otherwise idle cycles to execute instructions from another process. As a result, the throughput capacity of the system improves because idle cycles are no longer wasted and therefore more jobs can be run per unit of time. This feature has been in the SPARC T-series from the beginning, so why this paper? The difference with previous publications on this topic is in the amount of detail given. How this all works under the hood is fully explained using two example programs. Starting from the assembly language instructions, it is demonstrated in what way these programs execute. To really see what is happening we go down to the processor pipeline level, where the gaps in the execution are, and show in what way these idle cycles are filled by other copies of the same program running simultaneously. Both the SPARC T4 as well as the older UltraSPARC T2+ processor are covered. You may wonder why the UltraSPARC T2+ is included. The focus of this work is on the SPARC T4 processor, but to explain the basic concept of latency hiding at this very low level, we start with the UltraSPARC T2+ processor because it is architecturally a much simpler design. From the single issue, in-order pipelines of this processor we then shift gears and cover how this all works on the much more advanced dual issue, out-of-order architecture of the T4. The analysis and performance experiments have been conducted on both processors. The results depend on the processor, but in all cases the theoretical estimates are confirmed by the experiments. If you're interested to read a lot more about this and find out how things really work under the hood, you can download a copy of the paper here. A paper like this could not have been produced without the help of several other people. I want to thank the co-author of this paper, Jared Smolens, for his very valuable contributions and our highly inspiring discussions. I'm also indebted to Thomas Nau (Ulm University, Germany), Shane Sigler and Mark Woodyard (both at Oracle) for their feedback on earlier versions of this paper. Karen Perkins (Perkins Technical Writing and Editing) and Rick Ramsey at Oracle were very helpful in providing editorial and publishing assistance.

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• Efficiently separating Read/Compute/Write steps for concurrent processing of entities in Entity/Component systems

  - by TravisG

  Setup I have an entity-component architecture where Entities can have a set of attributes (which are pure data with no behavior) and there exist systems that run the entity logic which act on that data. Essentially, in somewhat pseudo-code: Entity { id; map<id_type, Attribute> attributes; } System { update(); vector<Entity> entities; } A system that just moves along all entities at a constant rate might be MovementSystem extends System { update() { for each entity in entities position = entity.attributes["position"]; position += vec3(1,1,1); } } Essentially, I'm trying to parallelise update() as efficiently as possible. This can be done by running entire systems in parallel, or by giving each update() of one system a couple of components so different threads can execute the update of the same system, but for a different subset of entities registered with that system. Problem In reality, these systems sometimes require that entities interact(/read/write data from/to) each other, sometimes within the same system (e.g. an AI system that reads state from other entities surrounding the current processed entity), but sometimes between different systems that depend on each other (i.e. a movement system that requires data from a system that processes user input). Now, when trying to parallelize the update phases of entity/component systems, the phases in which data (components/attributes) from Entities are read and used to compute something, and the phase where the modified data is written back to entities need to be separated in order to avoid data races. Otherwise the only way (not taking into account just "critical section"ing everything) to avoid them is to serialize parts of the update process that depend on other parts. This seems ugly. To me it would seem more elegant to be able to (ideally) have all processing running in parallel, where a system may read data from all entities as it wishes, but doesn't write modifications to that data back until some later point. The fact that this is even possible is based on the assumption that modification write-backs are usually very small in complexity, and don't require much performance, whereas computations are very expensive (relatively). So the overhead added by a delayed-write phase might be evened out by more efficient updating of entities (by having threads work more % of the time instead of waiting). A concrete example of this might be a system that updates physics. The system needs to both read and write a lot of data to and from entities. Optimally, there would be a system in place where all available threads update a subset of all entities registered with the physics system. In the case of the physics system this isn't trivially possible because of race conditions. So without a workaround, we would have to find other systems to run in parallel (which don't modify the same data as the physics system), other wise the remaining threads are waiting and wasting time. However, that has disadvantages Practically, the L3 cache is pretty much always better utilized when updating a large system with multiple threads, as opposed to multiple systems at once, which all act on different sets of data. Finding and assembling other systems to run in parallel can be extremely time consuming to design well enough to optimize performance. Sometimes, it might even not be possible at all because a system just depends on data that is touched by all other systems. Solution? In my thinking, a possible solution would be a system where reading/updating and writing of data is separated, so that in one expensive phase, systems only read data and compute what they need to compute, and then in a separate, performance-wise cheap, write phase, attributes of entities that needed to be modified are finally written back to the entities. The Question How might such a system be implemented to achieve optimal performance, as well as making programmer life easier? What are the implementation details of such a system and what might have to be changed in the existing EC-architecture to accommodate this solution?

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• Getting 2D Platformer entity collision Response Correct (side-to-side + jumping/landing on heads)

  - by jbrennan

  I've been working on a 2D (tile based) 2D platformer for iOS and I've got basic entity collision detection working, but there's just something not right about it and I can't quite figure out how to solve it. There are 2 forms of collision between player entities as I can tell, either the two players (human controlled) are hitting each other side-to-side (i. e. pushing against one another), or one player has jumped on the head of the other player (naturally, if I wanted to expand this to player vs enemy, the effects would be different, but the types of collisions would be identical, just the reaction should be a little different). In my code I believe I've got the side-to-side code working: If two entities press against one another, then they are both moved back on either side of the intersection rectangle so that they are just pushing on each other. I also have the "landed on the other player's head" part working. The real problem is, if the two players are currently pushing up against each other, and one player jumps, then at one point as they're jumping, the height-difference threshold that counts as a "land on head" is passed and then it registers as a jump. As a life-long player of 2D Mario Bros style games, this feels incorrect to me, but I can't quite figure out how to solve it. My code: (it's really Objective-C but I've put it in pseudo C-style code just to be simpler for non ObjC readers) void checkCollisions() { // For each entity in the scene, compare it with all other entities (but not with one it's already compared against) for (int i = 0; i < _allGameObjects.count(); i++) { // GameObject is an Entity GEGameObject *firstGameObject = _allGameObjects.objectAtIndex(i); // Don't check against yourself or any previous entity for (int j = i+1; j < _allGameObjects.count(); j++) { GEGameObject *secondGameObject = _allGameObjects.objectAtIndex(j); // Get the collision bounds for both entities, then see if they intersect // CGRect is a C-struct with an origin Point (x, y) and a Size (w, h) CGRect firstRect = firstGameObject.collisionBounds(); CGRect secondRect = secondGameObject.collisionBounds(); // Collision of any sort if (CGRectIntersectsRect(firstRect, secondRect)) { //////////////////////////////// // // // Check for jumping first (???) // // //////////////////////////////// if (firstRect.origin.y > (secondRect.origin.y + (secondRect.size.height * 0.7))) { // the top entity could be pretty far down/in to the bottom entity.... firstGameObject.didLandOnEntity(secondGameObject); } else if (secondRect.origin.y > (firstRect.origin.y + (firstRect.size.height * 0.7))) { // second entity was actually on top.... secondGameObject.didLandOnEntity.(firstGameObject); } else if (firstRect.origin.x > secondRect.origin.x && firstRect.origin.x < (secondRect.origin.x + secondRect.size.width)) { // Hit from the RIGHT CGRect intersection = CGRectIntersection(firstRect, secondRect); // The NUDGE just offsets either object back to the left or right // After the nudging, they are exactly pressing against each other with no intersection firstGameObject.nudgeToRightOfIntersection(intersection); secondGameObject.nudgeToLeftOfIntersection(intersection); } else if ((firstRect.origin.x + firstRect.size.width) > secondRect.origin.x) { // hit from the LEFT CGRect intersection = CGRectIntersection(firstRect, secondRect); secondGameObject.nudgeToRightOfIntersection(intersection); firstGameObject.nudgeToLeftOfIntersection(intersection); } } } } } I think my collision detection code is pretty close, but obviously I'm doing something a little wrong. I really think it's to do with the way my jumps are checked (I wanted to make sure that a jump could happen from an angle (instead of if the falling player had been at a right angle to the player below). Can someone please help me here? I haven't been able to find many resources on how to do this properly (and thinking like a game developer is new for me). Thanks in advance!

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• Deploy ASP.NET MVC 2 to IIS 7.5 targeting .NET 3.5

  - by Agent_9191

  I created an ASP.NET MVC 2 application in Visual Studio 2008. I set the release build to go through the ASP.NET compiler to precompile all the views, minify Javascript and CSS, clean up the web.config, etc. Since the production deployment is going to an IIS6 server, I set up my pseudo-production deployment on my Windows 7 machine to have the application pool run in classic mode targeting the 2.0 runtime. I set up the extensionless handler in the web.config that's necessary and everything worked great. The problem came when I upgraded the solution to Visual Studio 2010. I'm still targeting the 3.5 framework, but now I'm using MSBuild 4.0 since that's what Visual Studio 2010 uses. Everything still compiles correctly because it runs fine under Cassini, but when I deploy it to the same location (same application pool, identity, etc) it now behaves differently. I still have the extensionless handler in the web.config, but now when I navigate to the root of the application it does directory browsing, and any routes that it had previously handled now come back as 404 errors being handled by the StaticFile handler in IIS. I'm at a loss for what changed and is causing the break. I have looked at this question, but I have already verified that all the prerequisite components are installed.

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• Algorithm for dynamic combinations

  - by sOltan

  My code has a list called INPUTS, that contains a dynamic number of lists, let's call them A, B, C, .. N. These lists contain a dynamic number of Events I would like to call a function with each combination of Events. To illustrate with an example: INPUTS: A(0,1,2), B(0,1), C(0,1,2,3) I need to call my function this many times for each combination (the input count is dynamic, in this example it is three parameter, but it can be more or less) function(A[0],B[0],C[0]) function(A[0],B[1],C[0]) function(A[0],B[0],C[1]) function(A[0],B[1],C[1]) function(A[0],B[0],C[2]) function(A[0],B[1],C[2]) function(A[0],B[0],C[3]) function(A[0],B[1],C[3]) function(A[1],B[0],C[0]) function(A[1],B[1],C[0]) function(A[1],B[0],C[1]) function(A[1],B[1],C[1]) function(A[1],B[0],C[2]) function(A[1],B[1],C[2]) function(A[1],B[0],C[3]) function(A[1],B[1],C[3]) function(A[2],B[0],C[0]) function(A[2],B[1],C[0]) function(A[2],B[0],C[1]) function(A[2],B[1],C[1]) function(A[2],B[0],C[2]) function(A[2],B[1],C[2]) function(A[2],B[0],C[3]) function(A[2],B[1],C[3]) This is what I have thought of so far: My approach so far is to build a list of combinations. The element combination is itself a list of "index" to the input arrays A, B and C. For our example: my list iCOMBINATIONS contains the following iCOMBO lists (0,0,0) (0,1,0) (0,0,1) (0,1,1) (0,0,2) (0,1,2) (0,0,3) (0,1,3) (1,0,0) (1,1,0) (1,0,1) (1,1,1) (1,0,2) (1,1,2) (1,0,3) (1,1,3) (2,0,0) (2,1,0) (2,0,1) (2,1,1) (2,0,2) (2,1,2) (2,0,3) (2,1,3) Then I would do this: foreach( iCOMBO in iCOMBINATIONS) { foreach ( P in INPUTS ) { COMBO.Clear() foreach ( i in iCOMBO ) { COMBO.Add( P[ iCOMBO[i] ] ) } function( COMBO ) --- (instead of passing the events separately) } } But I need to find a way to build the list iCOMBINATIONS for any given number of INPUTS and their events. Any ideas? Is there actually a better algorithm than this? any pseudo code to help me with will be great. C# (or VB) Thank You

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• Hopcroft–Karp algorithm in Python

  - by Simon

  I am trying to implement the Hopcroft Karp algorithm in Python using networkx as graph representation. Currently I am as far as this: #Algorithms for bipartite graphs import networkx as nx import collections class HopcroftKarp(object): INFINITY = -1 def __init__(self, G): self.G = G def match(self): self.N1, self.N2 = self.partition() self.pair = {} self.dist = {} self.q = collections.deque() #init for v in self.G: self.pair[v] = None self.dist[v] = HopcroftKarp.INFINITY matching = 0 while self.bfs(): for v in self.N1: if self.pair[v] and self.dfs(v): matching = matching + 1 return matching def dfs(self, v): if v != None: for u in self.G.neighbors_iter(v): if self.dist[ self.pair[u] ] == self.dist[v] + 1 and self.dfs(self.pair[u]): self.pair[u] = v self.pair[v] = u return True self.dist[v] = HopcroftKarp.INFINITY return False return True def bfs(self): for v in self.N1: if self.pair[v] == None: self.dist[v] = 0 self.q.append(v) else: self.dist[v] = HopcroftKarp.INFINITY self.dist[None] = HopcroftKarp.INFINITY while len(self.q) > 0: v = self.q.pop() if v != None: for u in self.G.neighbors_iter(v): if self.dist[ self.pair[u] ] == HopcroftKarp.INFINITY: self.dist[ self.pair[u] ] = self.dist[v] + 1 self.q.append(self.pair[u]) return self.dist[None] != HopcroftKarp.INFINITY def partition(self): return nx.bipartite_sets(self.G) The algorithm is taken from http://en.wikipedia.org/wiki/Hopcroft%E2%80%93Karp_algorithm However it does not work. I use the following test code G = nx.Graph([ (1,"a"), (1,"c"), (2,"a"), (2,"b"), (3,"a"), (3,"c"), (4,"d"), (4,"e"),(4,"f"),(4,"g"), (5,"b"), (5,"c"), (6,"c"), (6,"d") ]) matching = HopcroftKarp(G).match() print matching Unfortunately this does not work, I end up in an endless loop :(. Can someone spot the error, I am out of ideas and I must admit that I have not yet fully understand the algorithm, so it is mostly an implementation of the pseudo code on wikipedia

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• Decoding ima4 audio format

  - by MrDatabase

  To reduce the download size of an iPhone application I'm compressing some audio files. Specifically I'm using afconvert on the command line to change .wav format to .caf format w/ ima4 compression. I've read this (wooji-juice.com) awesome post about this exact topic. I'm having trouble w/ the "decoding ima4 packets" step. I've looked at their sample code and I'm stuck. Please help w/ some pseudo code or sample code that can guide me in the right direction. Thanks! Additional info: Here is what I've completed and where I'm having trouble... I can play .wav files in both the simulator and on the phone. I can compress .wav files to .caf w/ ima4 compression using afconvert on the command line. I'm using the SoundEngine that came w/ CrashLanding (I fixed one memory leak). I modified the SoundEngine code to look for the mFormatID 'ima4'. I don't understand the blog post linked above starting w/ "Calculating the size of the unpacked data". Why do I need to do this? Also, what does the term "packet" refer to? I'm very new to any sort of audio programming.

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• Show/Hide RichFaces component onclick client-side? (without AJAX)

  - by Dolph Mathews

  I'm looking for a way to show/hide an arbitrary RichFaces component. In this case, I have a <rich:dataTable> that contains several rows. Each row needs to have it's own, independent Show/Hide link, such that when you click "Show details", two things happen: The "Show details" link is re-rendered as "Hide details" The associated detailsColumn is displayed. Furthermore, detailsColumns should be hidden by default (effectively rendered="true" to the client but hidden with style="display: none;"). I don't want to write my own JavaScript functions if it's not absolutely necessary. I also don't want to have a server-side bean keep track of which detailColumns are being displayed, and subsequently re-render everything over AJAX: this should be purely client-side behavior. I'm not sure how to accomplish that. The following pseudo-code (hopefully) illustrates my goal: <rich:column> <a href="#" onclick="#{thisRow.detailsColumn}.show();" rendered="">Show details</a> <a href="#" onclick="#{thisRow.detailsColumn}.hide();" rendered="">Hide details</a> </rich:column> <rich:column> <h:outputText value="#{thisRow.someData}" /> </rich:column> <rich:column id="detailsColumn" colspan="2" breakBefore="true"> <h:outputText value="#{thisRow.someMoreData}" /> </rich:column>

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• ANTLR AST rules fail with RewriteEmptyStreamException

  - by Barry Brown

  I have a simple grammar: grammar sample; options { output = AST; } assignment : IDENT ':=' expr ';' ; expr : factor ('*' factor)* ; factor : primary ('+' primary)* ; primary : NUM | '(' expr ')' ; IDENT : ('a'..'z')+ ; NUM : ('0'..'9')+ ; WS : (' '|'\n'|'\t'|'\r')+ {$channel=HIDDEN;} ; Now I want to add some rewrite rules to generate an AST. From what I've read online and in the Language Patterns book, I should be able to modify the grammar like this: assignment : IDENT ':=' expr ';' -> ^(':=' IDENT expr) ; expr : factor ('*' factor)* -> ^('*' factor+) ; factor : primary ('+' primary)* -> ^('+' primary+) ; primary : NUM | '(' expr ')' -> ^(expr) ; But it does not work. Although it compiles fine, when I run the parser I get a RewriteEmptyStreamException error. Here's where things get weird. If I define the pseudo tokens ADD and MULT and use them instead of the tree node literals, it works without error. tokens { ADD; MULT; } expr : factor ('*' factor)* -> ^(MULT factor+) ; factor : primary ('+' primary)* -> ^(ADD primary+) ; Alternatively, if I use the node suffix notation, it also appears to work fine: expr : factor ('*'^ factor)* ; factor : primary ('+'^ primary)* ; Is this discrepancy in behavior a bug?

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• How to support 3-byte UTF-8 Characters in ANT

  - by efelton

  I am trying to support UTF-8 characters in my ANT script. As long as the character string are made up of 2-byte UTF-8 characters, such as: Lògìñ Ùsèr ÌÐ Then things work fine. When I use Unicode Han Character: ? Which, according to this site: http://www.fileformat.info/info/unicode/char/6211/index.htm Has a UTF-8 encoding of 0xE6 0x88 0x91 I can see in UltraEdit, my input properties file has the values "E6 88 91" all in a row, so I'm fairly confident that my input is correct. And When I open the same file in Notepad++ I can see all the characters correctly. Here is my Build Script: <?xml version="1.0" encoding="UTF-8" ?> <project name="utf8test" default="all" basedir="."> <target name="all"> <loadproperties encoding="UTF-8" srcfile="./apps.properties.all.txt" /> <echo>No encoding ${common.app.name}</echo> <echo encoding="UTF-8">UTF-8 ${common.app.name}</echo> <echo encoding="UnicodeLittle">UnicodeLittle ${common.app.name}</echo> <echo encoding="UnicodeLittleUnmarked">UnicodeLittleUnmarked ${common.app.name}</echo> <echo>${common.app.ServerName}</echo> <echo>${bb.vendor}</echo> <echo>No encoding ${common.app.UserIdText}</echo> <echo encoding="UTF-8">UTF-8 ${common.app.UserIdText}</echo> <echo encoding="UnicodeLittle">UnicodeLittle ${common.app.UserIdText}</echo> <echo encoding="UnicodeLittleUnmarked">UnicodeLittleUnmarked ${common.app.UserIdText}</echo> <echoproperties /> </target> </project> And here is my properties file: common.app=VrvPsLTst common.app.name=?? common.app.description=Pseudo Loc Test App for Build Script testing common.app.ServerName=http://Vèrìvò.com bb.vendor=Vèrìvò common.app.PasswordText=Pàsswòrð bb.override.list=MP_COPYRIGHTTEXT, "Çòpÿrìght 2012 Vèrívó Bùîlð TéàM" common.app.LoginButtonText=Lògìñ common.app.UserIdText=Ùsèr ÌÐ bb.SMSSuccess=Mèssàgéß Sùççêssfúllÿ Sëñt common.app.LoginScreenMessage=WèlçòMé Mêssàgë common.app.LoginProgressMessage=Àùthèñtìçàtíòñ îñ prógréss... ios.RegistrationText=Règìstràtíòñ Téxt ios.RegistrationURL=http://www.josscrowcroft.com/2011/code/utf-8-multibyte-characters-in-url-parameters-%E2%9C%93/ Here is what the output looks like: Buildfile: C:\Temp\utf8\build.xml all: [echo] No encoding ?? [echo] UTF-8 ?? [echo] ÿþU n i c o d e L i t t l e ? ? [echo] U n i c o d e L i t t l e U n m a r k e d ? ? [echo] http://Vèrìvò.com [echo] Vèrìvò [echo] No encoding Ùsèr ÌÐ [echo] UTF-8 Ùsèr ÃŒÃ? [echo] ÿþU n i c o d e L i t t l e Ù s è r Ì Ð [echo] U n i c o d e L i t t l e U n m a r k e d Ù s è r Ì Ð [echoproperties] #Ant properties [echoproperties] #Mon Jun 18 15:25:13 EDT 2012 [echoproperties] ant.core.lib=C\:\\ant\\lib\\ant.jar [echoproperties] ant.file=C\:\\Temp\\utf8\\build.xml [echoproperties] ant.file.type=file [echoproperties] ant.file.type.utf8test=file [echoproperties] ant.file.utf8test=C\:\\Temp\\utf8\\build.xml [echoproperties] ant.home=c\:\\ant\\bin\\.. [echoproperties] ant.java.version=1.6 [echoproperties] ant.library.dir=C\:\\ant\\lib [echoproperties] ant.project.default-target=all [echoproperties] ant.project.invoked-targets=all [echoproperties] ant.project.name=utf8test [echoproperties] ant.version=Apache Ant version 1.8.1 compiled on April 30 2010 [echoproperties] awt.toolkit=sun.awt.windows.WToolkit [echoproperties] basedir=C\:\\Temp\\utf8 [echoproperties] bb.SMSSuccess=M\u00E8ss\u00E0g\u00E9\u00DF S\u00F9\u00E7\u00E7\u00EAssf\u00FAll\u00FF S\u00EB\u00F1t [echoproperties] bb.override.list=MP_COPYRIGHTTEXT, "\u00C7\u00F2p\u00FFr\u00ECght 2012 V\u00E8r\u00EDv\u00F3 B\u00F9\u00EEl\u00F0 T\u00E9\u00E0?" [echoproperties] bb.vendor=V\u00E8r\u00ECv\u00F2 [echoproperties] common.app=VrvPsLTst [echoproperties] common.app.LoginButtonText=L\u00F2g\u00EC\u00F1 [echoproperties] common.app.LoginProgressMessage=\u00C0\u00F9th\u00E8\u00F1t\u00EC\u00E7\u00E0t\u00ED\u00F2\u00F1 \u00EE\u00F1 pr\u00F3gr\u00E9ss... [echoproperties] common.app.LoginScreenMessage=W\u00E8l\u00E7\u00F2?\u00E9 M\u00EAss\u00E0g\u00EB [echoproperties] common.app.PasswordText=P\u00E0ssw\u00F2r\u00F0 [echoproperties] common.app.ServerName=http\://V\u00E8r\u00ECv\u00F2.com [echoproperties] common.app.UserIdText=\u00D9s\u00E8r \u00CC\u00D0 [echoproperties] common.app.description=Pseudo Loc Test App for Build Script testing [echoproperties] common.app.name=?? [echoproperties] file.encoding=Cp1252 [echoproperties] file.encoding.pkg=sun.io [echoproperties] file.separator=\\ [echoproperties] ios.RegistrationText=R\u00E8g\u00ECstr\u00E0t\u00ED\u00F2\u00F1 T\u00E9xt [echoproperties] ios.RegistrationURL=http\://www.josscrowcroft.com/2011/code/utf-8-multibyte-characters-in-url-parameters-%E2%9C%93/ [echoproperties] java.awt.graphicsenv=sun.awt.Win32GraphicsEnvironment [echoproperties] java.awt.printerjob=sun.awt.windows.WPrinterJob [echoproperties] java.class.path=c\:\\ant\\bin\\..\\lib\\ant-launcher.jar;C\:\\Temp\\utf8\\.\\;C\:\\Program Files (x86)\\Java\\jre7\\lib\\ext\\QTJava.zip;C\:\\ant\\lib\\ant-antlr.jar;C\:\\ant\\lib\\ant-apache-bcel.jar;C\:\\ant\\lib\\ant-apache-bsf.jar;C\:\\ant\\lib\\ant-apache-log4j.jar;C\:\\ant\\lib\\ant-apache-oro.jar;C\:\\ant\\lib\\ant-apache-regexp.jar;C\:\\ant\\lib\\ant-apache-resolver.jar;C\:\\ant\\lib\\ant-apache-xalan2.jar;C\:\\ant\\lib\\ant-commons-logging.jar;C\:\\ant\\lib\\ant-commons-net.jar;C\:\\ant\\lib\\ant-contrib-1.0b3.jar;C\:\\ant\\lib\\ant-jai.jar;C\:\\ant\\lib\\ant-javamail.jar;C\:\\ant\\lib\\ant-jdepend.jar;C\:\\ant\\lib\\ant-jmf.jar;C\:\\ant\\lib\\ant-jsch.jar;C\:\\ant\\lib\\ant-junit.jar;C\:\\ant\\lib\\ant-launcher.jar;C\:\\ant\\lib\\ant-netrexx.jar;C\:\\ant\\lib\\ant-nodeps.jar;C\:\\ant\\lib\\ant-starteam.jar;C\:\\ant\\lib\\ant-stylebook.jar;C\:\\ant\\lib\\ant-swing.jar;C\:\\ant\\lib\\ant-testutil.jar;C\:\\ant\\lib\\ant-trax.jar;C\:\\ant\\lib\\ant-weblogic.jar;C\:\\ant\\lib\\ant.jar;C\:\\ant\\lib\\bb-ant-tools.jar;C\:\\ant\\lib\\xercesImpl.jar;C\:\\ant\\lib\\xml-apis.jar;C\:\\Program Files\\Java\\jre7\\lib\\tools.jar [echoproperties] java.class.version=51.0 [echoproperties] java.endorsed.dirs=C\:\\Program Files\\Java\\jre7\\lib\\endorsed [echoproperties] java.ext.dirs=C\:\\Program Files\\Java\\jre7\\lib\\ext;C\:\\Windows\\Sun\\Java\\lib\\ext [echoproperties] java.home=C\:\\Program Files\\Java\\jre7 [echoproperties] java.io.tmpdir=C\:\\Users\\efelton\\AppData\\Local\\Temp\\ [echoproperties] java.library.path=C\:\\Windows\\SYSTEM32;C\:\\Windows\\Sun\\Java\\bin;C\:\\Windows\\system32;C\:\\Windows;C\:\\Windows\\SYSTEM32;C\:\\Windows;C\:\\Windows\\SYSTEM32\\WBEM;C\:\\Windows\\SYSTEM32\\WINDOWSPOWERSHELL\\V1.0\\;C\:\\PROGRAM FILES\\INTEL\\WIFI\\BIN\\;C\:\\PROGRAM FILES\\COMMON FILES\\INTEL\\WIRELESSCOMMON\\;C\:\\PROGRAM FILES (X86)\\MICROSOFT SQL SERVER\\100\\TOOLS\\BINN\\;C\:\\PROGRAM FILES\\MICROSOFT SQL SERVER\\100\\TOOLS\\BINN\\;C\:\\PROGRAM FILES\\MICROSOFT SQL SERVER\\100\\DTS\\BINN\\;C\:\\PROGRAM FILES (X86)\\MICROSOFT SQL SERVER\\100\\TOOLS\\BINN\\VSSHELL\\COMMON7\\IDE\\;C\:\\PROGRAM FILES (X86)\\MICROSOFT SQL SERVER\\100\\DTS\\BINN\\;C\:\\Program Files\\ThinkPad\\Bluetooth Software\\;C\:\\Program Files\\ThinkPad\\Bluetooth Software\\syswow64;C\:\\Program Files (x86)\\QuickTime\\QTSystem\\;C\:\\Program Files (x86)\\AccuRev\\bin;C\:\\Program Files\\Java\\jdk1.7.0_04\\bin;C\:\\Program Files (x86)\\IDM Computer Solutions\\UltraEdit\\;. [echoproperties] java.runtime.name=Java(TM) SE Runtime Environment [echoproperties] java.runtime.version=1.7.0_04-b22 [echoproperties] java.specification.name=Java Platform API Specification [echoproperties] java.specification.vendor=Oracle Corporation [echoproperties] java.specification.version=1.7 [echoproperties] java.vendor=Oracle Corporation [echoproperties] java.vendor.url=http\://java.oracle.com/ [echoproperties] java.vendor.url.bug=http\://bugreport.sun.com/bugreport/ [echoproperties] java.version=1.7.0_04 [echoproperties] java.vm.info=mixed mode [echoproperties] java.vm.name=Java HotSpot(TM) 64-Bit Server VM [echoproperties] java.vm.specification.name=Java Virtual Machine Specification [echoproperties] java.vm.specification.vendor=Oracle Corporation [echoproperties] java.vm.specification.version=1.7 [echoproperties] java.vm.vendor=Oracle Corporation [echoproperties] java.vm.version=23.0-b21 [echoproperties] line.separator=\r\n [echoproperties] os.arch=amd64 [echoproperties] os.name=Windows 7 [echoproperties] os.version=6.1 [echoproperties] path.separator=; [echoproperties] sun.arch.data.model=64 [echoproperties] sun.boot.class.path=C\:\\Program Files\\Java\\jre7\\lib\\resources.jar;C\:\\Program Files\\Java\\jre7\\lib\\rt.jar;C\:\\Program Files\\Java\\jre7\\lib\\sunrsasign.jar;C\:\\Program Files\\Java\\jre7\\lib\\jsse.jar;C\:\\Program Files\\Java\\jre7\\lib\\jce.jar;C\:\\Program Files\\Java\\jre7\\lib\\charsets.jar;C\:\\Program Files\\Java\\jre7\\lib\\jfr.jar;C\:\\Program Files\\Java\\jre7\\classes [echoproperties] sun.boot.library.path=C\:\\Program Files\\Java\\jre7\\bin [echoproperties] sun.cpu.endian=little [echoproperties] sun.cpu.isalist=amd64 [echoproperties] sun.desktop=windows [echoproperties] sun.io.unicode.encoding=UnicodeLittle [echoproperties] sun.java.command=org.apache.tools.ant.launch.Launcher -cp .;C\:\\Program Files (x86)\\Java\\jre7\\lib\\ext\\QTJava.zip [echoproperties] sun.java.launcher=SUN_STANDARD [echoproperties] sun.jnu.encoding=Cp1252 [echoproperties] sun.management.compiler=HotSpot 64-Bit Tiered Compilers [echoproperties] sun.os.patch.level=Service Pack 1 [echoproperties] user.country=US [echoproperties] user.dir=C\:\\Temp\\utf8 [echoproperties] user.home=C\:\\Users\\efelton [echoproperties] user.language=en [echoproperties] user.name=efelton [echoproperties] user.script= [echoproperties] user.timezone= [echoproperties] user.variant= BUILD SUCCESSFUL Total time: 1 second Thank you for your help EDIT\UPDATE 6/19/2012 I am developing in a Windows environment. I have installed a TTF from: http://freedesktop.org/wiki/Software/CJKUnifonts/Download I have updated UltraEdit to use the TTF and I can see the Chinese characters. <?xml version="1.0" encoding="UTF-8" ?> <project name="utf8test" default="all" basedir="."> <target name="all"> <echo>??</echo> <echo encoding="ISO-8859-1">ISO-8859-1 ??</echo> <echo encoding="UTF-8">UTF-8 ??</echo> <echo file="echo_output.txt" append="true" >?? ${line.separator}</echo> <echo file="echo_output.txt" append="true" encoding="ISO-8859-1">ISO-8859-1 ?? ${line.separator}</echo> <echo file="echo_output.txt" append="true" encoding="UTF-8">UTF-8 ?? ${line.separator}</echo> <echo file="echo_output.txt" append="true" encoding="UnicodeLittle">UnicodeLittle ?? ${line.separator}</echo> <echo file="echo_output.txt" append="true" encoding="UnicodeLittleUnmarked">UnicodeLittleUnmarked ?? ${line.separator}</echo> </target> </project> The output captured by running inside UltraEdit is: Buildfile: E:\temp\utf8\build.xml all: [echo] ?? [echo] ISO-8859-1 ?? [echo] UTF-8 ?? BUILD SUCCESSFUL Total time: 1 second And the echo_output.txt file shows up like this: ?? ISO-8859-1 ?? UTF-8 ?? ÿþU n i c o d e L i t t l e ? ? U n i c o d e L i t t l e U n m a r k e d ? ? So there appears to be somehting fundamentally wrong with how my ANT environment is set up since I cannot simply echo the character to the screen or to a file.

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• rand() generating the same number – even with srand(time(NULL)) in my main!

  - by Nick Sweet

  So, I'm trying to create a random vector (think geometry, not an expandable array), and every time I call my random vector function I get the same x value, thought y and z are different. int main () { srand ( (unsigned)time(NULL)); Vector<double> a; a.randvec(); cout << a << endl; return 0; } using the function //random Vector template <class T> void Vector<T>::randvec() { const int min=-10, max=10; int randx, randy, randz; const int bucket_size = RAND_MAX/(max-min); do randx = (rand()/bucket_size)+min; while (randx <= min && randx >= max); x = randx; do randy = (rand()/bucket_size)+min; while (randy <= min && randy >= max); y = randy; do randz = (rand()/bucket_size)+min; while (randz <= min && randz >= max); z = randz; } For some reason, randx will consistently return 8, whereas the other numbers seem to be following the (pseudo) randomness perfectly. However, if I put the call to define, say, randy before randx, randy will always return 8. Why is my first random number always 8? Am I seeding incorrectly?

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• determine parity of a bit representation of a number in MIPS

  - by Hristo

  Is there some instruction in MIPS that will determine the parity of a certain bit representation? I know to determine whether a "number" has an even parity or an odd parity is to XOR the individual bits of the binary representation together, but that seems computationally-intensive for a set of MIPS instructions... and I need to do this as quick as possible. Also, the number I'm working in is represented in Grey Code... just to throw that in there. So is there some pseudo-instruction in MIPS to determine the parity of a "number" or do I have to do it by hand? If there is no MIPS instruction, which it seems very unlikely to be, any advice on how to do it by hand? Thanks, Hristo follow-up: I found a optimization, but my implementation isn't working. unsigned int v; // 32-bit word v ^= v >> 1; v ^= v >> 2; v = (v & 0x11111111U) * 0x11111111U; return (v >> 28) & 1;

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• Webforms MVP Passive View - event handling

  - by ss2k

  Should the view have nothing event specific in its interface and call the presenter plain methods to handle events and not have any official EventHandlers? For instance // ASPX protected void OnSaveButtonClicked(object sender, EventArgs e) { _Presenter.OnSave(); } Or should the view have event EventHandlers defined in its interface and link those up explicitly to control events on the page // View public interface IView { ... event EventHandler Saved; ... } // ASPX Page implementing the view protected override void OnInit(EventArgs e) { base.OnInit(e); SaveButton.Click += delegate { Saved(this, e); }; } // Presenter internal Presenter(IView view,IRepository repository) { _view = view; _repository = repository; view.Saved += Save; } The second seems like a whole lot of plumbing code to add all over. My intention is to understand the benefits of each style and not just a blanket answer of which to use. My main goals is clarity and high value testability. Testability overall is important, but I wouldn't sacrifice design simplicity and clarity to be able to add another type of test that doesn't lead to too much gain over the test cases already possible with a simpler design. If a design choice does off more testability please include an example (pseudo code is fine) of the type of test it can now offer so I can make my decision if I value that type of extra test enough. Thanks!

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• mongodb: insert if not exists

  - by LeMiz

  Hello, Every day, I receive a stock of documents (an update). What I want to do is inserting each of them if it does not exists. I also want to keep track of the first time I inserted them, and the last time I saw them in an update. I don't want to have duplicate documents. I don't want to remove a document which has previously been saved, but is not in my update. 95% (estimated) of the records are unmodified from day to day. I am using the python driver (pymongo), for that matter. What I currently do is (pseudo-code): for each document in update: existing_document = collection.find_one(document) if not existing_document: document['insertion_date'] = now else: document = existing_document document['last_update_date'] = now my_collection.save(document) My problem is that it is very slow (40 mins for less than 100 000 records, and I have millions of them in the update). I am pretty sure there is something builtin for doing this, but the document for update() is mmmhhh.... a bit terse.... ( http://www.mongodb.org/display/DOCS/Updating ) Can someone give an advice on doing it faster ?

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• How to program a neural network for chess?

  - by marco92w

  Hello! I want to program a chess engine which learns to make good moves and win against other players. I've already coded a representation of the chess board and a function which outputs all possible moves. So I only need an evaluation function which says how good a given situation of the board is. Therefore, I would like to use an artificial neural network which should then evaluate a given position. The output should be a numerical value. The higher the value is, the better is the position for the white player. My approach is to build a network of 385 neurons: There are six unique chess pieces and 64 fields on the board. So for every field we take 6 neurons (1 for every piece). If there is a white piece, the input value is 1. If there is a black piece, the value is -1. And if there is no piece of that sort on that field, the value is 0. In addition to that there should be 1 neuron for the player to move. If it is White's turn, the input value is 1 and if it's Black's turn, the value is -1. I think that configuration of the neural network is quite good. But the main part is missing: How can I implement this neural network into a coding language (e.g. Delphi)? I think the weights for each neuron should be the same in the beginning. Depending on the result of a match, the weights should then be adjusted. But how? I think I should let 2 computer players (both using my engine) play against each other. If White wins, Black gets the feedback that its weights aren't good. So it would be great if you could help me implementing the neural network into a coding language (best would be Delphi, otherwise pseudo-code). Thanks in advance!

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• NETCF - Optimized Repaint (onPaint)

  - by Nullstr1ng

  Hi Guys, I want to ask for suggestions on how to optimize a repaint in Compact Framework? GetHashCode() didn't help because it always return a different hash code. Anyway, I have a program which you can drag and resize an object in run time. This object is a transparent object and it has a PNG image which also dynamically resize relative to object client size. Though I noticed, (e.g. I have 4 transparent object and I'm dragging or resizing one) all 4 of them triggers OnPaintBackground even if the 3 are not moving. Another one when am just tapping on the one object .. it sill triggers onPaintBacground(). Anyway, I don't have a problem when this events get triggered. What I like to do is optimization and that means I only have to repaint the object when it's necessary. Can you guys please give a suggestions? here's my pseudo C# code Bitmap _backBuff; onResize() { if(_backBuff != null) _backBuff.Dispose(); _backBuff = new Bitmap(ClientSize.Width, ClientSize.Height); Invalidate(); } onPaintBackground(e) /*have to use onPaintBackground because MSDN said it's faster*/ { using(Graphics g = Graphics.FromImage(_backBuff)) { g.Clear(Color.Black); // draw background ....some interface calling here ....and paint the background // draw alpha PNG .. get hDc .. paint PNG .. release hDc } e.Graphics.DrawImage(_backBuff,0,0); } Thanks in advance.

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• Switching from ListView to VirtualStringTree

  - by Jeff

  Hey S.O! I am trying to build my projects with a VirtualStringTree rather than a Listview, because of the vast speed difference. The thing is, even after looking thru the demo's, I just can't figure out exactly how I would use it as a ListView. Like, adding, deleting, and basically just working with ListView items is so easy, but when I look at the VT, it gets almost too complicated. All I am looking for, is a VT that looks like a ListView, with subitems etc. Here are some routines using the ListView, that I would like to use with VT (This is just a pseudo example: procedure Add; begin with ListView.Items.Add do Begin Caption := EditCaption.Text; SubItems.Add(EditSubItem.Text): End; end; Procedure ReadItem(I : Integer); begin ShowMessage(ListView.Items[I].Caption); ShowMessage(ListView.Items[I].SubItems[0]); end; Of course, also the Delete function, but since thats like 1 line, I didnt bother :P Could anyone maybe translate the above examples into using a ListView style VT? Thanks!

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• LGPL and Dual Licensing Ajax Library

  - by Thomas Hansen

  Hi guys, I'm the previous founder of Gaiaware and Gaia Ajax Widgets and when I used to work there we had this rhetoric (which I have confirmed with some very smart FOSS people is correct) that when using a GPL Ajax library you're basically "distributing" the JavaScript which in turn makes the GPL viral clause kick in and forces people to purchase a proprietary license if they're going to build Closed Source stuff... So now I'm the the LGPL world here with Ra-Ajax which is an LGPL licensed library and I've got no intentions of creating a GPL licensed library since I believe strongly in that the LGPL is the "enabler" of the Open Web to prevail. But something interesting have happened which I think might still give me a "business model" here which is the Linking clause of the LGPL which I think goes something like this (pseudo); "If you link to an LGPL licensed thing you get no restrictions on your own derived works"... But so we started creating something we're calling Ajax Starter-Kits which effectively is a "Project Kickstarter" where you can download a finished project/solution which basically enables you to start out with some pre-done boiler plate code for problems such as Ajax DataGrids, Ajax Calendar Applications, Ajax TreeView Applications etc. And the funny thing is that our users would NOT "link" to these, they would effectively BE our users applications... So to wrap up my question. Would this force users of our LGPL licensed Ajax Starter-Kits to LGPL license their own work? Basically if it does we have a business model (and I get very happy) if not I'd just have to hope people would still like to pay us those $29 for our Starter-Kits to support the project... ;) Help rewarded with extreme gratitude...

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• Updating Lists of Lists in Tapestry4 using textfields and a single submit button

  - by Nicolas Scarrci

  In Tapestry 4 I am trying it iterate over a list of lists (technically a list of objects who have a list of strings as a data field). I am currently doing this by using 'nested' for components. (This is pseudo code) <span jwcid="Form"> <span jwcid="@For" source="ognl:Javaclass.TopLevelList" value="ognl:SecondLevelList" index="ognl:index"> <span jwcid="@For" source="ognl:SecondLevelList.List" value="ognl:ListItem" index="ListItemIndex"> <span jwcid="@TextField" value="ognl:ListItem"/> <span jwcid="@Submit" listener="ognl:listeners.onSubmit"/> </span></span></span> The onSubmit listener then accesses the index and ListItem index page properties, as well as the ListItem page property in order to correctly update the list in Javaclass.TopLevelList. This works fine, but it looks terrible, and is cumbersome to the end user. I would prefer to somehow simulate this functionality using only one submit button at the bottom of the page. I have looked into somehow using the overlying form component to obtain a list of the 'form control components' within it, and then (with great care) parsing through tapestry's naming conventions to recover the functionality of the indexes. If anyone knows how to do this, or could explain the form component (how/when it submits, etc.) it would be greatly appreciated.

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• C++/CLI managed thread cleanup

  - by Guillermo Prandi

  Hi. I'm writing a managed C++/CLI library wrapper for the MySQL embedded server. The mysql C library requires me to call mysql_thread_init() for every thread that will be using it, and mysql_thread_end() for each thread that exits after using it. Debugging any given VB.Net project I can see at least seven threads; I suppose my library will see only one thread if VB doesn't explicitly create worker threads itself (any confirmations on that?). However, I need clients to my library to be able to create worker threads if they need to, so my library must be thread-aware to some degree. The first option I could think of is to expose some "EnterThread()" and "LeaveThread()" methods in my class, so the client code will explicitly call them at the beginning and before exiting their DoWork() method. This should work if (1) .Net doesn't "magically" create threads the user isn't aware of and (2) the user is careful enough to have the methods called in a try/finally structure of some sort. However, I don't like it very much to have the user handle things manually like that, and I wonder if I could give her a hand on that matter. In a pure Win32 C/C++ DLL I do have the DllMain DLL_THREAD_ATTACH and DLL_THREAD_DETACH pseudo-events, and I could use them for calling mysql_thread_init() and mysql_thread_end() as needed, but there seem to be no such thing in C++/CLI managed code. At the expense of some performance (not much, I think) I can use TLS for detecting the "usage from a new thread" case, but I can imagine no mechanism for the thread exiting case. So, my questions are: (1) could .net create application threads without the user being aware of them? and (2) is there any mechanism I could use similar to DLL_THREAD_ATTACH / DLL_THREAD_DETACH from managed C++/CLI? Thanks in advance.

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