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• Handling extremely large numbers in a language which can't?

  - by Mallow

  I'm trying to think about how I would go about doing calculations on extremely large numbers (to infinitum - intergers no floats) if the language construct is incapable of handling numbers larger than a certain value. I am sure I am not the first nor the last to ask this question but the search terms I am using aren't giving me an algorithm to handle those situations. Rather most suggestions offer a language change or variable change, or talk about things that seem irrelevant to my search. So I need a little guideance. I would sketch out an algorithm like this: Determine the max length of the integer variable for the language. If a number is more than half the length of the max length of the variable split it in an array. (give a little play room) Array order [0] = the numbers most to the right [n-max] = numbers most to the left Ex. Num: 29392023 Array[0]:23, Array[1]: 20, array[2]: 39, array[3]:29 Since I established half the length of the variable as the mark off point I can then calculate the ones, tenths, hundredths, etc. Place via the halfway mark so that if a variable max length was 10 digits from 0 to 9999999999 then I know that by halfing that to five digits give me some play room. So if I add or multiply I can have a variable checker function that see that the sixth digit (from the right) of array[0] is the same place as the first digit (from the right) of array[1]. Dividing and subtracting have their own issues which I haven't thought about yet. I would like to know about the best implementations of supporting larger numbers than the program can.

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• Can't get sprite to rotate correctly?

  - by rphello101

  I'm attempting to play with graphics using Java/Slick 2d. I'm trying to get my sprite to rotate to wherever the mouse is on the screen and then move accordingly. I figured the best way to do this was to keep track of the angle the sprite is at since I have to multiply the cosine/sine of the angle by the move speed in order to get the sprite to go "forwards" even if it is, say, facing 45 degrees in quadrant 3. However, before I even worry about that, I'm having trouble even getting my sprite to rotate in the first place. Preliminary console tests showed that this code worked, but when applied to the sprite, it just kind twitches. Anyone know what's wrong? int mX = Mouse.getX(); int mY = HEIGHT - Mouse.getY(); int pX = sprite.x; int pY = sprite.y; int tempY, tempX; double mAng, pAng = sprite.angle; double angRotate=0; if(mX!=pX){ tempY=pY-mY; tempX=mX-pX; mAng = Math.toDegrees(Math.atan2(Math.abs((tempY)),Math.abs((tempX)))); if(mAng==0 && mX<=pX) mAng=180; } else{ if(mY>pY) mAng=270; else mAng=90; } //Calculations if(mX<pX&&mY<pY){ //If in Q2 mAng = 180-mAng; } if(mX<pX&&mY>pY){ //If in Q3 mAng = 180+mAng; } if(mX>pX&&mY>pY){ //If in Q4 mAng = 360-mAng; } angRotate = mAng-pAng; sprite.angle = mAng; sprite.image.setRotation((float)angRotate);

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• GLSL billboard move center of rotation

  - by Jacob Kofoed

  I have successfully set up a billboard shader that works, it can take in a quad and rotate it so it always points toward the screen. I am using this vertex-shader: void main(){ vec4 tmpPos = (MVP * bufferMatrix * vec4(0.0, 0.0, 0.0, 1.0)) + (MV * vec4( vertexPosition.x * 1.0 * bufferMatrix[0][0], vertexPosition.y * 1.0 * bufferMatrix[1][1], vertexPosition.z * 1.0 * bufferMatrix[2][2], 0.0) ); UV = UVOffset + vertexUV * UVScale; gl_Position = tmpPos; BufferMatrix is the model-matrix, it is an attribute to support Instance-drawing. The problem is best explained through pictures: This is the start position of the camera: And this is the position, looking in from 45 degree to the right: Obviously, as each character is it's own quad, the shader rotates each one around their own center towards the camera. What I in fact want is for them to rotate around a shared center, how would I do this? What I have been trying to do this far is: mat4 translation = mat4(1.0); translation = glm::translate(translation, vec3(pos)*1.f * 2.f); translation = glm::scale(translation, vec3(scale, 1.f)); translation = glm::translate(translation, vec3(anchorPoint - pos) / vec3(scale, 1.f)); Where the translation is the bufferMatrix sent to the shader. What I am trying to do is offset the center, but this might not be possible with a single matrix..? I am interested in a solution that doesn't require CPU calculations each frame, but rather set it up once and then let the shader do the billboard rotation. I realize there's many different solutions, like merging all the quads together, but I would first like to know if the approach with offsetting the center is possible. If it all seems a bit confusing, it's because I'm a little confused myself.

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• How can I transform a Point2f with a matrix on Android?

  - by Vivendi

  I'm developing for Android and I'm using the android.renderscript.Matrix3f class to do some calculations. What I need to do now is to now is to do something like mat.tranform(pointIn, pointOut); So I need to transform a matrix by a given Point class. In awt I would simply do this: AffineTransform t = new AffineTransform(); Point2D.Float p = new Point2D.Float(); t.transform( p, p ); But in Android I now have this: Matrix3f t = new Matrix3f(); PointF p = new PointF(); // Now I need to tranform it somehow.. But the Matrix3f class in Android doesn't have a Matrix.transform(Point2D ptSrc, Point2D ptDst) method. So I guess I have to do the transformation manually. But I'm not really sure how that works. From what I've seen it's something like a translate and then a rotate? Could anyone please tell me how to do this in code?

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• Running multiple box2D world objects on a server

  - by CharbelAbdo

  I'm creating a multiplayer game using LibGdx (with Box2d) and Kryonet. Since this is the first time I work on multiplayer games, I read a bit about server - client implementations, and it turns out that the server should handle important tasks like collision detection, hits, characters dying etc... Based on some articles (like the excellent Gabriel Gambetta Fast paced multiplayer series), I also know that the client should work in parallel to avoid the lag while the server responds to commands. Physics wise, each game will have 2 players, and any projectiles fired. What I'm thinking of doing is the following: Create a physics world on the client When the game is signaled to start, I create the same physics world on the server (without any rendering obviously). Whenever the player issues a command (move or fire), I send the command to the server and immediately start processing it on the client. When the server receives the command, it applies it on the server's world (set velocity etc...) Each 100ms, the server sends the new state to the client which corrects what was calculated locally. Any critical action (hit, death, level up) is calculated only on the server and sent to the client. Essentially, I would have a Box2d World object running on the server for each game in progress, in sync with the worlds running on the clients. The alternative would be to do my own calculations on the server instead of relying on Box2D to do them for me, but I'm trying to avoid that. My question is: Is it wise to have, for example, 1000 instances of the World object running and executing steps on the server? Tomcat used around 750 MBytes of memory when trying it without any object added to the world. Anybody tried that before? If not, is there any alternative? Google did not help me, are there any guidelines to use when you want to have physics on both the client and the server? Thanks for any help.

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• Dell xps 15z fan issue in ubuntu 12.04

  - by Paxinum

  I just updated to ubuntu 12.04 on my Dell laptop xps 15z. The trouble is that I hear a slight ticking sound every 3rd second, probably from a fan. This is a new issue in this ubuntu version. I use the recommended boot options for grub, i.e. acpi_backlight=vendor, but I do not use any acpi=off or acpi=noirq. Is there a way to fix this issue from ubuntu, by maybe controlling the fans somehow? EDIT: Notice, the sound goes away as the fan speeds up, (when doing calculations or such), so it is really a fan issue. EDIT2: I have located the issue: If I use conky 1.9, together with the command execpi for a python application, then the sound appears, and the noise syncs with the update interval for conky (NOT for the update interval for execpi!). The noise seems to be proportional to the complexity of the drawing that is needed. This is very strange, as this issue was not in the prev. version of conky I used. The solution was to increase the update interval for conky from 0.5 to 3, i.e. update every 3rd second instead of twice a second.

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• What do I need to know to design a language and write a interpreter for it?

  - by alFReD NSH

  I know this question has been asked and even there are thousands of books and articles about it. But the problem is that there are too many, and I don't know are they good enough, I have to design a language and write a interpreter for it. The base language is javascript (using nodejs) but it's ok if the compiler was written in another language that I can use from node. I had done a research about compiler compilers in JS, there is jison (Bison implementaion in JS), waxeye, peg.js. I decided to give jison a try, due to the popularity and its being used by coffee script, so it should be able to cover my language too. The grammar definition syntax is similar to bison. But when I tried read the bison manual it seemed very hard to understand for me. And I think it's because I don't know a lot of things about what I'm doing. Like I don't what is formal language theory. I am experienced in Javascript (I'm more talented in JS than most average programmers). And also know basic C and C++ (not much experience but can write a working code for basic things). I haven't had any formal education, so I may not be familiar with some software engineering and computer science principles. Though everyday I try to grasp a lot of articles and improve. So I'm asking if you know any good book or article that can help me. Please also write why the resource you're suggesting is good. --update-- The language I'm trying to create, is not really complicated. All it has is expressions (with or without units), comparisons and logical operators. There are no functions, loops, ... The goal is to create a language that non-programmers can easily learn. And to write customized validations and calculations.

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• From a DDD perspective is a report generating service a domain service or an infrastructure service?

  - by Songo

  Let assume we have the following service whose responsibility is to generate Excel reports: class ExcelReportService{ public String generateReport(String fileFormatFilePath, ResultSet data){ ReportFormat reportFormat = new ReportFormat(fileFormatFilePath); ExcelDataFormatterService excelDataFormatterService = new ExcelDataFormatterService(); FormattedData formattedData = excelDataFormatterService.format(data); ExcelFileService excelFileService = new ExcelFileService(); String reportPath= excelFileService.generateReport(reportFormat,formattedData); return reportPath; } } This is pseudo code for the service I want to design where: fileFormatFilePath: path to a configuration file where I'll keep the format of my excel file (headers, column widths, number of columns,..etc) data: the actual records returned from the database. This data can't be used directly coz I might need to make further calculations to the data before inserting them to the excel file. ReportFormat: Value object to hold the report format, has methods like getHeaders(), getColumnWidth(),...etc. ExcelDataFormatterService: a service to hold any logic that need to be applied to the data returned from the database before inserting it to the file. FormattedData: Value object the represents the formatted data to be inserted. ExcelFileService: a wrapper top the 3rd party library that generates the excel file. Now how do you determine whether a service is an infrastructure or domain service? I have the following 3 services here: ExcelReportService, ExcelDataFormatterService and ExcelFileService?

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• How to scroll hex tiles?

  - by Chris Evans

  I don't seem to be able to find an answer to this one. I have a map of hex tiles. I wish to implement scrolling. Code at present: drawTilemap = function() { actualX = Math.floor(viewportX / hexWidth); actualY = Math.floor(viewportY / hexHeight); offsetX = -(viewportX - (actualX * hexWidth)); offsetY = -(viewportY - (actualY * hexHeight)); for(i = 0; i < (10); i++) { for(j = 0; j < 10; j++) { if(i % 2 == 0) { x = (hexOffsetX * i) + offsetX; y = j * sourceHeight; } else { x = (hexOffsetX * i) + offsetX; y = hexOffsetY + (j * sourceHeight); } var tileselected = mapone[actualX + i][j]; drawTile(x, y, tileselected); } } } The code I've written so far only handles X movement. It doesn't yet work the way it should do. If you look at my example on jsfiddle.net below you will see that when moving to the right, when you get to the next hex tile along, there is a problem with the X position and calculations that have taken place. It seems it is a simple bit of maths that is missing. Unfortunately I've been unable to find an example that includes scrolling yet. http://jsfiddle.net/hd87E/1/ Make sure there is no horizontal scroll bar then trying moving right using the - right arrow on the keyboard. You will see the problem as you reach the end of the first tile. Apologies for the horrid code, I'm learning! Cheers

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• Oracle R Distribution 2-13.2 Update Available

  - by Sherry LaMonica

  Oracle has released an update to the Oracle R Distribution, an Oracle-supported distribution of open source R. Oracle R Distribution 2-13.2 now contains the ability to dynamically link the following libraries on both Windows and Linux: The Intel Math Kernel Library (MKL) on Intel chips The AMD Core Math Library (ACML) on AMD chips To take advantage of the performance enhancements provided by Intel MKL or AMD ACML in Oracle R Distribution, simply add the MKL or ACML shared library directory to the LD_LIBRARY_PATH system environment variable. This automatically enables MKL or ACML to make use of all available processors, vastly speeding up linear algebra computations and eliminating the need to recompile R.  Even on a single core, the optimized algorithms in the Intel MKL libraries are faster than using R's standard BLAS library. Open-source R is linked to NetLib's BLAS libraries, but they are not multi-threaded and only use one core. While R's internal BLAS are efficient for most computations, it's possible to recompile R to link to a different, multi-threaded BLAS library to improve performance on eligible calculations. Compiling and linking to R yourself can be involved, but for many, the significantly improved calculation speed justifies the effort. Oracle R Distribution notably simplifies the process of using external math libraries by enabling R to auto-load MKL or ACML. For R commands that don't link to BLAS code, taking advantage of database parallelism using embedded R execution in Oracle R Enterprise is the route to improved performance. For more information about rebuilding R with different BLAS libraries, see the linear algebra section in the R Installation and Administration manual. As always, the Oracle R Distribution is available as a free download to anyone. Questions and comments are welcome on the Oracle R Forum.

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• Japanese Multiplication simulation - is a program actually capable of improving calculation speed?

  - by jt0dd

  On SuperUser, I asked a (possibly silly) question about processors using mathematical shortcuts and would like to have a look at the possibility at the software application of that concept. I'd like to write a simulation of Japanese Multiplication to get benchmarks on large calculations utilizing the shortcut vs traditional CPU multiplication. I'm curious as to whether it makes sense to try this. My Question: I'd like to know whether or not a software math shortcut, as described above is actually a shortcut at all. This is a question of programming concept. By utilizing the simulation of Japanese Multiplication, is a program actually capable of improving calculation speed? Or am I doomed from the start? The answer to this question isn't required to determine whether or not the experiment will succeed, but rather whether or not it's logically possible for such a thing to occur in any program, using this concept as an example. My theory is that since addition is computed faster than multiplication, a simulation of Japanese multiplication may actually allow a program to multiply (large) numbers faster than the CPU arithmetic unit can. I think this would be a very interesting finding, if it proves to be true. If, in the multiplication of numbers of any immense size, the shortcut were to calculate the result via less instructions (or faster) than traditional ALU multiplication, I would consider the experiment a success.

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• Flickering problem with world matrix

  - by gnomgrol

  I do have a pretty wierd problem today. As soon as I try to change my translation- or rotationmatrix for an object to something else than (0,0,0), the object starts to flicker (scaling works fine). It rapid and randomly switches between the spot it should be in and a crippled something. I first thought that the problem would be z-fighting, but now Im pretty sure it isn't. I have now clue at all what it could be, here are two screenshots of the two states the plant is switching between. I already used PIX, but could find anything of use (Im not a very good debugger anyway) I would appreciate any help, thanks a lot! Important code: D3DXMatrixIdentity(&World); D3DXVECTOR3 rotaxisX = D3DXVECTOR3(1.0f, 0.0f, 0.0f); D3DXVECTOR3 rotaxisY = D3DXVECTOR3(0.0f, 1.0f, 0.0f); D3DXVECTOR3 rotaxisZ = D3DXVECTOR3(0.0f, 0.0f, 1.0f); D3DXMATRIX temprot1, temprot2, temprot3; D3DXMatrixRotationAxis(&temprot1, &rotaxisX, 0); D3DXMatrixRotationAxis(&temprot2, &rotaxisY, 0); D3DXMatrixRotationAxis(&temprot3, &rotaxisZ, 0); Rotation = temprot1 *temprot2 * temprot3; D3DXMatrixTranslation(&Translation, 0.0f, 10.0f, 0.0f); D3DXMatrixScaling(&Scale, 0.02f, 0.02f, 0.02f); //Set objs world space using the transformations World = Translation * Rotation * Scale; shader: cbuffer cbPerObject { matrix worldMatrix; matrix viewMatrix; matrix projectionMatrix; }; // Change the position vector to be 4 units for proper matrix calculations. input.position.w = 1.0f; // Calculate the position of the vertex against the world, view, and projection matrices. output.position = mul(input.position, worldMatrix); output.position = mul(output.position, viewMatrix); output.position = mul(output.position, projectionMatrix);

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• Calculating a child object's Position, Rotation and Scale values?

  - by Sergio Plascencia

  I am making my own game editor, but have encountered the following problem: I have two objects, A and B. A's initial values: Position: (3,3,3), Rotation: (45,10,0), Scale(1,2,2.5) B's initial values: Position: (1,1,1), Rotation: (10,34,18), Scale(1.5,2,1) If I now make B a child of A, I need to re-calculate the B's Position, Rotation and Scale relative to A such that it maintains its current position, rotation and scale in world coordinates. So B's position would now be (-2, -2, -2) since now A is its center and (-2, -2, -2) will keep B in the same position. I think I got the Position and scale figured out, but not rotation. So I opened Unity and ran the same example and I noticed that when making a child object, the child object did not move at all. but had its Position, Rotation and Scale values changed relative to the parent. For example: Unity (Parent Object "A"): Position: (0,0,0) Rotation: (45,10,0) Scale: (1,1,1) Unity (Child Object "B"): Position: (0,0,0) Rotation: (0,0,0) Scale: (1,1,1) When B becomes a child of A, it's rotation values become: X: -44.13605 Y: -14.00195 Z: 9.851074 If I plug the same rotation values into the B object in my editor, the object does not move at all. How did Unity arrive at those rotation values for the child? What are the calculations? If you can put all the equations for the Position, Rotation or Scale then I can double check I am doing it correctly but the Rotation is what I really need.

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• Office 2010 Client &ndash; Should I go with 32 bit or 64 bit?

  - by Sahil Malik

  Ad:: SharePoint 2007 Training in .NET 3.5 technologies (more information). As you know, Office 2010 client now comes in both 32 bit and 64 bit versions. The question is, should you go with 32 bit or 64 bit? 64 is bigger than 32 .. so 64 is better no? NO! Given a choice, or unless you have a very strong reason not to – GO WITH 32 bit. Why is that? Here is why - 32 bit apps actually work better on 64 bit OS’s in most scenarios due to WoW, and the additional 64 bit VLSW calculations. If you have 2007 installations to support, SharePoint designer 2010 cannot be used to work with SharePoint 2007 sites. So you will have to install SharePoint designer 2007 32bit side by side with SharePoint designer 2010 32 bit side by side. So you cannot mix and match 32 bit and 64 bit here. Of course you can virtualize and not have this problem to begin with :-D. 64 bit office will break many things on your SharePoint experience for that client – example, that fancy datasheet view won’t work on lists. 32 bit office apps don’t have this issue. There are some extreme situations where you DO want 64 bit client apps though. Specifically if you have HUGE excel sheets to work with, then 64 bit office client excel is much better than the equivalent 32 bit excel. Comment on the article ....

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• Calculate travel time on road map with semaphores

  - by Ivansek

  I have a road map with intersections. At intersections there are semaphores. For each semaphore I generate a red light time and green light time which are represented with syntax [R:T1, G:T2], for example: 119 185 250 A ------- B: [R:6, G:4] ------ C: [R:5, G:5] ------ D I want to calculate a car travel time from A - D. Now I do this with this pseudo code: function get_travel_time(semaphores_configuration) { time = 0; for( i=1; i<path.length;i++) { prev_node = path[i-1]; next_node = path[i]); cost = cost_between(prev_node, next_node) time += (cost/movement_speed) // movement_speed = 50px per second light_times = get_light_times(path[i], semaphore_configurations) lights_cycle = get_lights_cycle(light_times) // Eg: [R,R,R,G,G,G,G], where [R:3, G:4] lights_sum = light_times.green_time+light_times.red_light; // Lights cycle time light = lights_cycle[cost%lights_sum]; if( light == "R" ) { time += light_times.red_light; } } return time; } So for distance 119 between A and B travel time is, 119/50 = 2.38s ( exactly mesaured time is between 2.5s and 2.6s), then we add time if we came at a red light when at B. If we came at a red light is calculated with lines: lights_cycle = get_lights_cycle(light_times) // Eg: [R,R,R,G,G,G,G], where [R:3, G:4] lights_sum = light_times.green_time+light_times.red_light light = lights_cycle[cost%lights_sum]; if( light == "R" ) { time += light_times.red_light; } This pseudo code doesn't calculate exactly the same times as they are mesaured, but the calculations are very close to them. Any idea how I would calculate this?

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• Name of the Countdown Numbers round problem - and algorithmic solutions?

  - by Dai

  For the non-Brits in the audience, there's a segment of a daytime game-show where contestants have a set of 6 numbers and a randomly generated target number. They have to reach the target number using any (but not necessarily all) of the 6 numbers using only arithmetic operators. All calculations must result in positive integers. An example: Youtube: Countdown - The Most Extraordinary Numbers Game Ever? A detailed description is given on Wikipedia: Countdown (Game Show) For example: The contentant selects 6 numbers - two large (possibilities include 25, 50, 75, 100) and four small (numbers 1 .. 10, each included twice in the pool). The numbers picked are 75, 50, 2, 3, 8, 7 are given with a target number of 812. One attempt is (75 + 50 - 8) * 7 - (3 * 2) = 813 (This scores 7 points for a solution within 5 of the target) An exact answer would be (50 + 8) * 7 * 2 = 812 (This would have scored 10 points exactly matching the target). Obviously this problem has existed before the advent of TV, but the Wikipedia article doesn't give it a name. I've also saw this game at a primary school I attended where the game was called "Crypto" as an inter-class competition - but searching for it now reveals nothing. I took part in it a few times and my dad wrote an Excel spreadsheet that attempted to brute-force the problem, I don't remember how it worked (only that it didn't work, what with Excel's 65535 row limit), but surely there must be an algorithmic solution for the problem. Maybe there's a solution that works the way human cognition does (e.g. in-parallel to find numbers 'close enough', then taking candidates and performing 'smaller' operations).

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• Expanding RAID-5

  - by Garry

  I'm new to RAID and trying to get my head around things. I have owned a Drobo in the past (which I liked) but it failed. Here's a hypothetical scenario: Assume I set up a RAID-5 array consisting of four 1TB hot-swappable 2.5" SATA drives. I name this volume 'My Data'. By my calculations, that would give me 2.7TB of usable space and the ability to recover if a single drive fails. I have a few questions: What happens if I pull out a single 1TB drive and replace it with a 2TB drive? Would the array automatically rebuild itself with no issues? Would the maximum capacity remain 2.7TB? If number (1) above is true and the array rebuilds itself with three 1TB drives one 2TB drive what would happen if I then pulled another 1TB drive out and stuck in a 2TB drive (you can see where I'm going here can't you). Would I eventually be able to gain more storage by gradually adding bigger drives? From a practical point of view, how much input is required from me as the end user whilst these drives are being pulled out and put in? On the Drobo, the storage space just automagically handles itself. Would I have to be actively involved in telling Ubuntu what was going on or would any of it be automated? Thanks in advance,

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• Dealing with Fine-Grained Cache Entries in Coherence

  - by jpurdy

  On occasion we have seen significant memory overhead when using very small cache entries. Consider the case where there is a small key (say a synthetic key stored in a long) and a small value (perhaps a number or short string). With most backing maps, each cache entry will require an instance of Map.Entry, and in the case of a LocalCache backing map (used for expiry and eviction), there is additional metadata stored (such as last access time). Given the size of this data (usually a few dozen bytes) and the granularity of Java memory allocation (often a minimum of 32 bytes per object, depending on the specific JVM implementation), it is easily possible to end up with the case where the cache entry appears to be a couple dozen bytes but ends up occupying several hundred bytes of actual heap, resulting in anywhere from a 5x to 10x increase in stated memory requirements. In most cases, this increase applies to only a few small NamedCaches, and is inconsequential -- but in some cases it might apply to one or more very large NamedCaches, in which case it may dominate memory sizing calculations. Ultimately, the requirement is to avoid the per-entry overhead, which can be done either at the application level by grouping multiple logical entries into single cache entries, or at the backing map level, again by combining multiple entries into a smaller number of larger heap objects. At the application level, it may be possible to combine objects based on parent-child or sibling relationships (basically the same requirements that would apply to using partition affinity). If there is no natural relationship, it may still be possible to combine objects, effectively using a Coherence NamedCache as a "map of maps". This forces the application to first find a collection of objects (by performing a partial hash) and then to look within that collection for the desired object. This is most naturally implemented as a collection of entry processors to avoid pulling unnecessary data back to the client (and also to encapsulate that logic within a service layer). At the backing map level, the NIO storage option keeps keys on heap, and so has limited benefit for this situation. The Elastic Data features of Coherence naturally combine entries into larger heap objects, with the caveat that only data -- and not indexes -- can be stored in Elastic Data.

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• Bending of track in a racing game

  - by caius

  I am trying to create a small racing game in which the track would be modeled using a BSpline curve for the path's center line and directional vectors to define the 'bending' of the track at each point. My problem is that I don't know how to calculate the correct bending / slope of the curve, in such a way that it would be optimal or at least visually nice for a car to 'bend in the corner'. My idea was to use the direction of the 2nd derivatives of the curve, however while this approach looks fine for most of the track, there are points in which the 2nd derivative makes sharp 'twists' / very quick 180 degree flips. I also read about 'knots' of bsplines, but I don't know if such 'twist' in 2nd derivatives is a knot or knots are something else. Can you tell me that using a BSpline: 1. How could I calculate a visually nice bending of a track for a racing game? 2. Is it possible to do this by using some simple calculations of centripertal force / gravity? 3. Is it possible to do this by using 1st, 2nd and 3rd derivatives of the BSpline curve? I am not looking for the 'physically correct' bending angle for the track, I would just like to create something which is visually pleasing in a simple game. I am using a framework which has a built-in class for BSpline, including support for 1st, 2nd and 3rd derivatives of the curve.

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• Including Microsoft.XNA.Framework.Input.Touch in a project?

  - by steven_desu

  So after running through tutorials by both Microsoft and www.xnadevelopment.com I feel very confident in my ability to get to work on my first game using the XNA Framework. I've manipulated sprites, added audio, changed game states, and even went a step further to apply the knowledge I had and figure out how to make animations and basic 2-dimensional physics (including impulses, force, acceleration, and speed calculations) But then shortly into the project I hit a curious bump that I've been unable to figure out. In wanting to implement menus, pause screens, and several different aspects of play (a "pre-level" prep screen, the level itself, and a screen after the level to review how well you did) I took a look at Microsoft's Game State Management sample. I understood the concept, although it was admittedly quite a lot to take in. Not wanting to recreate the entire concept by scratch (after all- what purpose would that serve?) I tried copying and pasting the sample code into my own ScreenManager class (as well as InputState and GameScreen classes) to try and borrow their ingenuity. When I did this, however, my project stopped compiling. I was getting the following error: The type or namespace name 'Touch' does not exist in the namespace 'Microsoft.Xna.Framework.Input' (are you missing an assembly reference?) Having read through their sample code already, I realized that this namespace and every function and class within it could be safely ripped from the code without losing functionality. It's a namespace simply for integrating with touchscreen devices (presumably Windows Phone 7, but maybe also tablets). But then I began to wonder- how come Microsoft's sample compiled but mine didn't? I copied their code exactly so there must be a setting somewhere that I need to change in Visual Studio in order to correct this. I tried creating a new project as a Windows Phone 7 game rather than a Windows game, however that only forced it to compile to a Windows Phone emulator and denied me the ability to change the resolution and other features which I clearly had the power to do in the sample code. So my question is simple - how do I properly use the namespace Microsoft.XNA.Framework.Input.Touch?

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• Web application interacts bi-directional with server program?

  - by Roelof Berkepeis

  I want to write a web application to play chess against the engine Crafty. I'm not new to PHP and javascript, but must learn how to interact with a server process : how can a web application and/or (jQuery) ajax interact bi-directionally with a (linux) program running on the server? At this moment i am developing on (Apache) local host. Crafty is installed on my Ubuntu PC. This well-known chess engine has no GUI, it runs in terminal by the command $ /usr/games/crafty and so you can play chess against it and even see it's calculations. I can make Crafty run by PHP, using the functions proc_open() or exec(), and most documentation i found states that the output stream should be a file .. But i think i don't want such setup, because then the webpage should be constanty polling that file (eg. by ajax) to see if some new data was appended, right? How can Crafty talk to the web page directly, saying "i have calculated another variation" or "i have decided a move" etc, then display this info on the web page and let the user give some counter move, just like in terminal. Isn't it possible to use some session / stream / listener? I have no clue at all, can anybody point me in a right direction?

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• What is the best way to exploit multicores when making multithread games?

  - by Keeper

  Many people suggest to write a program, and then start optimizing it. But I think that when it's coming to multithreading with multicore, a little think ahead is required. I've read about using threads, and experienced it myself during some courses at the university (still a student). The big question is simple, but a bit abstract: What thread related steps in game design do I need to take, before implementation? Now trying to be more specific. Let's say, as an example, that I'm making a small board game (like Monopoly) that I want to be multithreaded. My goal Is that this multithreaded game will exploit the best of the multicore system, lets say 4-6 cores (like in i7 processors). My answer to this question at the moment is, one thread for each of these four basic components: GUI User Input / Output AI (computer rival) Other game related calculations (like shortest path from A to B, or level up status change) I'm not an expert (yet!), and I'm sure there are better answers out there. Any suggestion, answer, different approach will be helpful. Some thoughts: Maybe splitting the main database is a good way.. (or total disaster.. )

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• Managing many draw calls for dynamic objects

  - by codetiger

  We are developing a game (cross-platform) using Irrlicht. The game has many (around 200 - 500) dynamic objects flying around during the game. Most of these objects are static mesh and build from 20 - 50 unique Meshes. We created seperate scenenodes for each object and referring its mesh instance. But the output was very much unexpected. Menu screen: (150 tris - Just to show you the full speed rendering performance of 2 test computers) a) NVidia Quadro FX 3800 with 1GB: 1600 FPS DirectX and 2600 FPS on OpenGL b) Mac Mini with Geforce 9400M 256mb: 260 FPS in OpenGL Now inside the game in a test level: (160 dynamic objects counting around 10K tris): a) NVidia Quadro FX 3800 with 1GB: 45 FPS DirectX and 50 FPS on OpenGL b) Mac Mini with Geforce 9400M 256mb: 45 FPS in OpenGL Obviously we don't have the option of mesh batch rendering as most of the objects are dynamic. And the one big static terrain is already in single mesh buffer. To add more information, we use one 2048 png for texture for most of the dynamic objects. And our collision detection hardly and other calculations hardly make any impact on FPS. So we understood its the draw calls we make that eats up all FPS. Is there a way we can optimize the rendering, or are we missing something?

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• Should this code/logic be included in Business Objects class or a separate class?

  - by aspdotnetuser

  I have created a small application which has a three tier architecture and I have business object classes to represent entities such as User, Orders, UserType etc. In these classes I have methods that are executed when the Constuctor method of, for example, User is called. These methods perform calculations and generate details that setup data for attributes that are part of each User object. Here is the structure for the project in Visual Studio: Here is some code from the business object class User.cs: Public Class User { public string Name { get; set; } public int RandomNumber { get; set; } etc public User { Name = GetName(); RandomNumber = GetRandomNumber(); } public string GetName() { .... return name; } public int GetRandomNumber() { ... return randomNumber; } } Should this logic be included in the Business Object classes or should it be included in a Utilities class of some kind? Or in the business rules?

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• How are certain analytics metrics (time on site, etc.) usually distributed?

  - by a barking spider

  I'm not sure if I've come to the right place to ask this question, but I'm gathering some information for a research project. We're trying to design an experiment that'll heavily involve web analytics, and I'm trying to figure out some sensible values of mean +/- standard deviation for the following visitor-level (i.e., visitor 1 spends 2 minutes on site, visitor 2 spends 1 minute -- mean 1.5 +/- 0.71...) metrics: time spent on site page views If time allowed, we would put up the sites and gather the information ourselves, but we have a grant deadline coming up. I realize that even though these the distributions of these quantities are probably going to be heavily skewed towards zero, we'll need some reasonable figures or estimates of these figures in order to do sample size calculations, etc. Anyway, I'm not sure where else I'd turn, and I certainly have had a difficult time finding these values in the prior literature. If someone could direct me to a paper with the right information, or if you have these figures on hand (perhaps taken directly from your logs!) -- that would be amazing, and I'd love to hear from you. Thanks in advance, and even though I'm not allowed to reveal too much, rest assured that this info'll be applied towards a good cause :)

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