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  • How to mount an ISO (or NRG) image and rip it as if it were a physical CD?

    - by Michael Robinson
    I have an ISO (created from an NRG with nrg2iso) backup of a beloved game from my youth: Dark Reign: Rise of the Shadowhand (1998). I with to relive those better times by listening to game's soundtrack. Is there a way for me to mount said ISO in such a way that I can rip the audio tracks into mp3 files? I ask because although I can successfully mount the ISO, ripit / abcde report no cd inserted. How I mounted the ISO: sudo mount -t iso9660 -o loop iso.iso /media/ISO Alternatively is there another way to recover audio from ISO / NRG images? Update: I was able to mount the NRG version of my backup in a way that ripit recognized using gCDEmu. ripit failed to rip, however, barfing on the first track - which is most definitely a data track. Is there a way to make ripit ignore the first track?

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  • problem with loading in .FBX meshes in DirectX 10

    - by N0xus
    I'm trying to load in meshes into DirectX 10. I've created a bunch of classes that handle it and allow me to call in a mesh with only a single line of code in my main game class. How ever, when I run the program this is what renders: In the debug output window the following errors keep appearing: D3D10: ERROR: ID3D10Device::DrawIndexed: Input Assembler - Vertex Shader linkage error: Signatures between stages are incompatible. The reason is that Semantic 'TEXCOORD' is defined for mismatched hardware registers between the output stage and input stage. [ EXECUTION ERROR #343: DEVICE_SHADER_LINKAGE_REGISTERINDEX ] D3D10: ERROR: ID3D10Device::DrawIndexed: Input Assembler - Vertex Shader linkage error: Signatures between stages are incompatible. The reason is that the input stage requires Semantic/Index (POSITION,0) as input, but it is not provided by the output stage. [ EXECUTION ERROR #342: DEVICE_SHADER_LINKAGE_SEMANTICNAME_NOT_FOUND ] The thing is, I've no idea how to fix this. The code I'm using does work and I've simply brought all of that code into a new project of mine. There are no build errors and this only appears when the game is running The .fx file is as follows: float4x4 matWorld; float4x4 matView; float4x4 matProjection; struct VS_INPUT { float4 Pos:POSITION; float2 TexCoord:TEXCOORD; }; struct PS_INPUT { float4 Pos:SV_POSITION; float2 TexCoord:TEXCOORD; }; Texture2D diffuseTexture; SamplerState diffuseSampler { Filter = MIN_MAG_MIP_POINT; AddressU = WRAP; AddressV = WRAP; }; // // Vertex Shader // PS_INPUT VS( VS_INPUT input ) { PS_INPUT output=(PS_INPUT)0; float4x4 viewProjection=mul(matView,matProjection); float4x4 worldViewProjection=mul(matWorld,viewProjection); output.Pos=mul(input.Pos,worldViewProjection); output.TexCoord=input.TexCoord; return output; } // // Pixel Shader // float4 PS(PS_INPUT input ) : SV_Target { return diffuseTexture.Sample(diffuseSampler,input.TexCoord); //return float4(1.0f,1.0f,1.0f,1.0f); } RasterizerState NoCulling { FILLMODE=SOLID; CULLMODE=NONE; }; technique10 Render { pass P0 { SetVertexShader( CompileShader( vs_4_0, VS() ) ); SetGeometryShader( NULL ); SetPixelShader( CompileShader( ps_4_0, PS() ) ); SetRasterizerState(NoCulling); } } In my game, the .fx file and model are called and set as follows: Loading in shader file //Set the shader flags - BMD DWORD dwShaderFlags = D3D10_SHADER_ENABLE_STRICTNESS; #if defined( DEBUG ) || defined( _DEBUG ) dwShaderFlags |= D3D10_SHADER_DEBUG; #endif ID3D10Blob * pErrorBuffer=NULL; if( FAILED( D3DX10CreateEffectFromFile( TEXT("TransformedTexture.fx" ), NULL, NULL, "fx_4_0", dwShaderFlags, 0, md3dDevice, NULL, NULL, &m_pEffect, &pErrorBuffer, NULL ) ) ) { char * pErrorStr = ( char* )pErrorBuffer->GetBufferPointer(); //If the creation of the Effect fails then a message box will be shown MessageBoxA( NULL, pErrorStr, "Error", MB_OK ); return false; } //Get the technique called Render from the effect, we need this for rendering later on m_pTechnique=m_pEffect->GetTechniqueByName("Render"); //Number of elements in the layout UINT numElements = TexturedLitVertex::layoutSize; //Get the Pass description, we need this to bind the vertex to the pipeline D3D10_PASS_DESC PassDesc; m_pTechnique->GetPassByIndex( 0 )->GetDesc( &PassDesc ); //Create Input layout to describe the incoming buffer to the input assembler if (FAILED(md3dDevice->CreateInputLayout( TexturedLitVertex::layout, numElements,PassDesc.pIAInputSignature, PassDesc.IAInputSignatureSize, &m_pVertexLayout ) ) ) { return false; } model loading: m_pTestRenderable=new CRenderable(); //m_pTestRenderable->create<TexturedVertex>(md3dDevice,8,6,vertices,indices); m_pModelLoader = new CModelLoader(); m_pTestRenderable = m_pModelLoader->loadModelFromFile( md3dDevice,"armoredrecon.fbx" ); m_pGameObjectTest = new CGameObject(); m_pGameObjectTest->setRenderable( m_pTestRenderable ); // Set primitive topology, how are we going to interpet the vertices in the vertex buffer md3dDevice->IASetPrimitiveTopology( D3D10_PRIMITIVE_TOPOLOGY_TRIANGLELIST ); if ( FAILED( D3DX10CreateShaderResourceViewFromFile( md3dDevice, TEXT( "armoredrecon_diff.png" ), NULL, NULL, &m_pTextureShaderResource, NULL ) ) ) { MessageBox( NULL, TEXT( "Can't load Texture" ), TEXT( "Error" ), MB_OK ); return false; } m_pDiffuseTextureVariable = m_pEffect->GetVariableByName( "diffuseTexture" )->AsShaderResource(); m_pDiffuseTextureVariable->SetResource( m_pTextureShaderResource ); Finally, the draw function code: //All drawing will occur between the clear and present m_pViewMatrixVariable->SetMatrix( ( float* )m_matView ); m_pWorldMatrixVariable->SetMatrix( ( float* )m_pGameObjectTest->getWorld() ); //Get the stride(size) of the a vertex, we need this to tell the pipeline the size of one vertex UINT stride = m_pTestRenderable->getStride(); //The offset from start of the buffer to where our vertices are located UINT offset = m_pTestRenderable->getOffset(); ID3D10Buffer * pVB=m_pTestRenderable->getVB(); //Bind the vertex buffer to input assembler stage - md3dDevice->IASetVertexBuffers( 0, 1, &pVB, &stride, &offset ); md3dDevice->IASetIndexBuffer( m_pTestRenderable->getIB(), DXGI_FORMAT_R32_UINT, 0 ); //Get the Description of the technique, we need this in order to loop through each pass in the technique D3D10_TECHNIQUE_DESC techDesc; m_pTechnique->GetDesc( &techDesc ); //Loop through the passes in the technique for( UINT p = 0; p < techDesc.Passes; ++p ) { //Get a pass at current index and apply it m_pTechnique->GetPassByIndex( p )->Apply( 0 ); //Draw call md3dDevice->DrawIndexed(m_pTestRenderable->getNumOfIndices(),0,0); //m_pD3D10Device->Draw(m_pTestRenderable->getNumOfVerts(),0); } Is there anything I've clearly done wrong or are missing? Spent 2 weeks trying to workout what on earth I've done wrong to no avail. Any insight a fresh pair eyes could give on this would be great.

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  • SQL, moving million records from a database to other database [migrated]

    - by Ryoma
    I am a C# developer, I am not really good with SQL. I have a simple questions here. I need to move more than 50 millions records from a database to other database. I tried to use the import function in ms SQL, however it got stuck because the log was full (I got an error message The transaction log for database 'mydatabase' is full due to 'LOG_BACKUP'). The database recovery model was set to simple. My friend said that importing millions records using task-import data will cause the log to be massive and told me to use loop instead to transfer the data, does anyone know how and why? thanks in advance

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  • Collision Detection Game Design and Architecture

    - by Chompas
    I've reading some articles about collision detection. My question here is about ideas on the design for it. Baically I have a C++ game that has a main loop with entities with an update method. Based on keyboard input, these characters updates their positions. My question is not about how to detect collisions, it's about getting ideas in which is the best way to implement this. The game has a main character but also enemies that have to collide between them, so I'm not sure where to make all the iterations for checking collisions and if the right way is to check everything against everything. Thanks in advance.

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  • What to do with input during movement?

    - by user1895420
    In a concept I'm working on, the player can move from one position in a grid to the next. Once movement starts it can't be changed and takes a predetermined amount of time to finish (about a quarter of a second). Even though their movement can't be altered, the player can still press keys (perhaps in anticipation of their next move). What do I do with this input? Possibilities i've thought of: Ignore all input during movement. Log all input and loop through them one by one once movement finishes. Log the first or last input and move when possible. I'm not really sure which is the most appropriate or most natural. Hence my question: What do I do with player-input during movement?

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  • Finding the contact point with SAT

    - by Kai
    The Separating Axis Theorem (SAT) makes it simple to determine the Minimum Translation Vector, i.e., the shortest vector that can separate two colliding objects. However, what I need is the vector that separates the objects along the vector that the penetrating object is moving (i.e. the contact point). I drew a picture to help clarify. There is one box, moving from the before to the after position. In its after position, it intersects the grey polygon. SAT can easily return the MTV, which is the red vector. I am looking to calculate the blue vector. My current solution performs a binary search between the before and after positions until the length of the blue vector is known to a certain threshold. It works but it's a very expensive calculation since the collision between shapes needs to be recalculated every loop. Is there a simpler and/or more efficient way to find the contact point vector?

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  • Pathfinding library

    - by Shivan Dragon
    I'm an amateur game developer and somewhat amateur Java developer as well. I'm trying to find a way to have path finding for my game(s). I've first Googled for some existing Java libraries that have various path-finding implementations, but I've failed to find any. It seems to me that the only way to get pathfinding code is to use it via a game engine (like Unity). But I'd just like to have a library that I can use and make the game loop and other stuff on my own. Failing to find such a library I've tried implementing some algorithms myself. I've managed to make a running A* in Java, but for fancier stuff like D* I find it hard to do it by hand. So then, my question is, are there any Java libraries that contain at least some basic pathfinding algorithms implementations?

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  • How do I detect multiple sprite collisions when there are >10 sprites?

    - by yao jiang
    I making a small program to animate the astar algorithm. If you look at the image, there are lots of yellow cars moving around. Those can collide at any moment, could be just one or all of them could just stupidly crash into each other. How do I detect all of those collisions? How do I find out which specific car has crash into which other car? I understand that pygame has collision function, but it only detects one collision at a time and I'd have to specify which sprites. Right now I am just trying to iterate through each sprite to see if there is collision: for car1 in carlist: for car2 in carlist: collide(car1, car2); This can't be the proper way to do it, if the car list goes to a huge number, a double loop will be too slow.

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  • PyGame QIX clone, filling areas

    - by astropanic
    I'm playing around with PyGame. Now I'm trying to implement a QIX clone. I have my game loop, and I can move the player (cursor) on the screen. In QIX, the movment of the player leaves a trace (tail) on the screen, creating a polyline. If the polyline with the screen boundaries creates a polygon, the area is filled. How I can accomplish this behaviour ? How store the tail in memory ? How to detect when it build a closed shape that should be filled ? I don't need an exact working solution, some pointers, algo names would be cool.

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  • Limiting Audit Exposure and Managing Risk – Q&A and Follow-Up Conversation

    - by Tanu Sood
    Thanks to all who attended the live ISACA webcast on Limiting Audit Exposure and Managing Risk with Metrics-Driven Identity Analytics. We were really fortunate to have Don Sparks from ISACA moderate the webcast featuring Stuart Lincoln, Vice President, IT P&L Client Services, BNP Paribas, North America and Neil Gandhi, Principal Product Manager, Oracle Identity Analytics. Stuart’s insights given the team’s role in providing IT for P&L Client Services and his tremendous experience in identity management and establishing sustainable compliance programs were true value-add at yesterday’s webcast. And if you are a healthcare organization looking to solve your compliance and security challenges, we recommend you join us for a live webcast on Tuesday, November 29 at 10 am PT. The webcast will feature experts from Kaiser Permanente, PricewaterhouseCoopers and Oracle and the focus of the discussion will be around the compliance challenges a healthcare organization faces and best practices for tackling those. Here are the details: Healthcare IT News Webcast: Managing Risk and Enforcing Compliance in Healthcare with Identity Analytics Tuesday, November 29, 201110:00 a.m. PT / 1:00 p.m. ET Register Today The ISACA webcast replay is now available on-demand and the slides are also available for download. Since we didn’t have time to address all the questions we received during the live Q&A portion of the webcast, we have captured responses to the remaining questions here. Please continue to provide us your feedback and insights from your experience in deploying identity compliance solutions. Q. Can you please clarify the mechanism utilized to populate the Identity Warehouse from each individual application's access management function / files? A. Oracle Identity Analytics (OIA) supports direct imports from applications. Data collection is based on Extract, Transform and Load (ETL) that eliminates the need to write connectors to different applications. Oracle Identity Analytics’ import engine supports complex entitlement feeds saved as either text files or XML. The imports can be scheduled on a periodic basis or triggered as needed. If the applications are synchronized with a user provisioning solution like Oracle Identity Manager, Oracle Identity Analytics has a seamless integration to pull in data from Oracle Identity Manager. Q.  Can you provide a short summary of the new features in your latest release of Oracle Identity Analytics? A. Oracle recently announced availability of enhanced Oracle Identity Analytics. This release focused on easing the certification process by offering risk analytics driven certification, advanced certification screens, business centric views and significant improvement in performance including 3X faster data imports, 3X faster certification campaign generation and advanced auto-certification features, that  will allow organizations to improve user productivity by up to 80%. Closed-loop risk feedback and IT policy monitoring with Oracle Identity Manager, a leading user provisioning solution, allows for more accurate certification reviews. And, OIA's improved performance enables customers to scale compliance initiatives supporting millions of user entitlements across thousands of applications, whether on premise or in the cloud, without compromising speed or integrity. Q. Will ISACA grant a CPE credit for attending this ISACA-sponsored webinar today? A. From ISACA: Hello and thank you for your interest in the 2011 ISACA Webinar Program!  Unfortunately, there are no CPEs offered for this program, archived or live.  We will be looking into the feasibility of offering them in the future.  Q. Would you be able to use this to help manage licenses for software? That is to say - could it track software that is not used by a user, thus eliminating the software license? A. OIA’s integration with Oracle Identity Manager, a leading user provisioning solution, allows organizations to detect ghost accounts or unused accounts via account reconciliation. Based on company’s policies, this could trigger an automated workflow for account deletion or asking for further investigation. Closed-loop feedback between the two solutions would then allow visibility into the complete audit trail of when the account was detected, the action taken, by whom, when and the current status. Q. We have quarterly attestations and .xls mechanisms are not working. Once the identity data is correlated in Identity Analytics, do you then automate access certification? A. OIA’s identity warehouse analyzes and correlates identity data across various resources that allows OIA to determine a user’s risk profile, who the access review request should go to, along with all the relevant access details of the user. The access certification manager gets notification on what to review, when and the relevant data is presented in a business friendly screen. Based on the result of the access certification process, actions are triggered and results recorded and archived. Access review managers have visual risk indicators that also allow them to prioritize access certification tasks and efforts. Q. How does Oracle Identity Analytics work with Cloud Security? A. For enterprises looking to build their own cloud(s), Oracle offers a set of security services that cloud developers can leverage including Oracle Identity Analytics.  For enterprises looking to manage their compliance requirements but without hosting those in-house and instead having a hosting provider offer managed Identity Management services to the organizations, Oracle Identity Analytics can be leveraged much the same way as you’d in an on-premise (within the enterprise) environment. In fact, organizations today are leveraging Oracle Identity Analytics to manage identity compliance in both these ways. Q. Would you recommend this as a cost effective solution for a smaller organization with @ 2,500 users? A. The key return-on-investment (ROI) on Oracle Identity Analytics is derived from automating compliance processes thereby eliminating administrative overhead, minimizing errors, maintaining cost- and time-effective sustainable compliance processes and minimizing audit exposures and penalties.  Of course, there are other tangible benefits that are derived from an Oracle Identity Analytics implementation as outlined in the webcast. For a quantitative analysis of your requirements and potential ROI calculation, we recommend you refer to the Forrester Study on Total Economic Impact of Oracle Identity Analytics. For an in-person discussion, please email Richard Caldwell.

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  • .htaccess rewrite www to non-www and remove .html

    - by lester8891
    I need rewrite rules to redirect the following: http://www. to http:// /file.html to /file I've tried using a combination of these but each time it results in a redirect loop on one of the situations RewriteBase / RewriteRule ^(.*)\.html$ $1 [NC] RewriteCond %{HTTP_HOST} ^www.domain.co.uk [NC, L] RewriteRule ^(.*)$ http://domain.co.uk/$1 [R=301] I figure it's probably something to do with the flags but I don't know how to fix it. Just to be clear it needs to do all these situations: http://www.domain.co.uk to http://domain.co.uk http://www.domain.co.uk/file.html to http://domain.co.uk/file http://domain.co.uk to http://domain.co.uk http://domain.co.uk/file.html to http://domain.co.uk/file Thanks!

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  • OpenGL-ES: clearing the alpha of the FrameBufferObject

    - by MrDatabase
    This question is a follow-up to Texture artifacts on iPad How does one "clear the alpha of the render texture frameBufferObject"? I've searched around here, StackOverflow and various search engines but no luck. I've tried a few things... for example calling GlClear(GL_COLOR_BUFFER_BIT) at the beginning of my render loop... but it doesn't seem to make a difference. Any help is appreciated since I'm still new to OpenGL. Cheers! p.s. I read on SO and in Apple's documentation that GlClear should always be called at the beginning of the renderLoop. Agree? Disagree? Here's where I read this: http://stackoverflow.com/questions/2538662/how-does-glclear-improve-performance

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  • Resources for improving your comprehension of recursion?

    - by Andrew M
    I know what recursion is (when a patten reoccurs within itself, typically a function that calls itself on one of its lines, after a breakout conditional... right?), and I can understand recursive functions if I study them closely. My problem is, when I see new examples, I'm always initially confused. If I see a loop, or a mapping, zipping, nesting, polymorphic calling, and so on, I know what's going just by looking at it. When I see recursive code, my thought process is usually 'wtf is this?' followed by 'oh it's recursive' followed by 'I guess it must work, if they say it does.' So do you have any tips/plans/resources for building up your skills in this area? Recursion is kind of a wierd concept so I'm thinking the way to tackle it may be equally wierd and inobvious.

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  • The best tile based level design [on hold]

    - by ReallyGoodPie
    My current method for tile based levels is to put everything in an array like the following: grass = g sky = s house = h ... """ ["SSSSSSSSSSSSSSSSSSSSSSSSSSSSSS"], ["SSSSSSSSSSSSSSSSSSSSSSSSSSSSSS"], ["HHHHHHHHHHHHHHSSSSSSSSSSSSSSSS"], ["GGGGGGGGGGGGGGGGGGGGGGGGGGGGGG"], """ I would then run a for loop to pass these on to a sprite class, bliting the images to the screen. This is what I'd generally do in pygame when I am creating levels for a tile based RPG's. However, as I've gone on, I have added allot more sprites and image and it is seriously becoming more and more confusing to work with this and allot of mistakes are being made. What is the best alternative or other methods for doing this?

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  • 2D Planet Gravity

    - by baked
    I'm trying to make a simple game where a spaceship is launched and then its path is effected by the gravity of planets. Similar to this game: http://sciencenetlinks.com/interactives/gravity.html I wish to know how to replicate the effect the planets have on the spaceship in this game so a spaceship can 'loop' around a planet to change direction. I have managed to achieve some bogus results where the spaceship loops in a huge ellipse around the planet or is only slightly affected by the gravity of a planet using Vectors. Thanks in advance. p.s I have plenty of coding experience just none to do with game dev.

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  • Improving grepping over a huge file performance

    - by rogerio_marcio
    I have FILE_A which has over 300K lines and FILE_B which has over 30M lines. I created a bash script that greps each line in FILE_A over in FILE_B and writes the result of the grep to a new file. This whole process is taking over 5+ hours. I'm looking for suggestions on whether you see any way of improving the performance of my script. I'm using grep -F -m 1 as the grep command. FILE_A looks like this: 123456789 123455321 and FILE_B is like this: 123456789,123456789,730025400149993, 123455321,123455321,730025400126097, So with bash I have a while loop that picks the next line in FILE_A and greps it over in FILE_B. When the pattern is found in FILE_B i write it to result.txt. while read -r line; do grep -F -m1 $line 30MFile done < 300KFile Thanks a lot in advance for your help.

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  • How does an Engine like Source process entities?

    - by Júlio Souza
    [background information] On the Source engine (and it's antecessor, goldsrc, quake's) the game objects are divided on two types, world and entities. The world is the map geometry and the entities are players, particles, sounds, scores, etc (for the Source Engine). Every entity has a think function, which do all the logic for that entity. So, if everything that needs to be processed comes from a base class with the think function, the game engine could store everything on a list and, on every frame, loop through it and call that function. On a first look, this idea is reasonable, but it can take too much resources, if the game has a lot of entities.. [end of background information] So, how does a engine like Source take care (process, update, draw, etc) of the game objects?

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  • Electronic circuit simulator four-way flood-filling issues

    - by AJ Weeks
    I've made an electronic circuit board simulator which has simply 3 types of tiles: wires, power sources, and inverters. Wires connect to anything they touch, other than the sides of inverters; inverters have one input side and one output side; and finally power tiles connect in a similar manner as wires. In the case of an infinite loop, caused by the output of the inverter feeding into its input, I want inverters to oscillate (quickly turn on/off). I've attempted to implement a FloodFill algorithm to spread the power throughout the grid, but seem to have gotten something wrong, as only the tiles above the power source get powered (as seen below) I've attempted to debug the program, but have had no luck thus far. My code concerning the updating of power can be seen here.

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  • How to optimize collision detection

    - by Niklas
    I am developing a 2D Java Game with LibGDX. This is what it kinda looks like (simplified): The big black circle is the player, which you can move by tilting the smartphone. The red circles and blue rectangles are enemies, which will move from the right of the screen to the left. The player has to avoid crashing into them. Right now I am checking in the Game Loop every enemy against the player, whether they collide or not. This seems kinda inefficient to me, but I don't know how to improve it. I have tried the Quadtree approach, but it did not really work. The player could easily glitch through enemies and the collision was not detected. Unfortunately, I have destroyed the Quadtree implementation. I used this [tutorial/blog] as my Quadtree implementation(http://gamedevelopment.tutsplus.com/tutorials/quick-tip-use-quadtrees-to-detect-likely-collisions-in-2d-space--gamedev-374).

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  • How can I best study a problem to determine whether recursion can/should be used?

    - by user10326
    In some cases, I fail to see that a problem could be solved by the divide and conquer method. To give a specific example, when studying the find max sub-array problem, my first approach is to brute force it by using a double loop to find the max subarray. When I saw the solution using the divide and conquer approach which is recursion-based, I understood it but ok. From my side, though, when I first read the problem statement, I did not think that recursion is applicable. When studying a problem, is there any technique or trick to see that a recursion based (i.e. divide and conquer) approach can be used or not?

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  • Sprites as Actors

    - by Scán
    Hello, I'm not experienced in GameDev questions, but as a programmer. In the language Scala, you can have scalable multi-tasking with Actors, very stable, as I hear. You can even habe hundreds of thousands of them running at once without a problem. So I thought, maybe you can use these as a base class for 2D-Sprites, to break out of the game-loop thing that requires to go through all the sprites and move them. They'd basically move themselves, event-driven. Would that make sense for a game? Having it multitasked like that? After all, it will run on the JVM, though that should not be much of a problem nowadays.

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  • Find vertices of a convex hull

    - by Jeff Bullard
    I am attempting to do this within CGAL. From a 3D point cloud, find the convex hull, then loop over the finite facets of the convex hull and print each facet's vertices. It seems like there should be a straightforward way to do this; I would have expected that 3D polyhedra would own a vector of facet objects, each of which in turn would own a vector of its edges, each of which in turn would own a vector of its vertices, and that their would be some access through this hierarchy using iterators. But so far I have been unable to find a simple way to navigate through this hierarchy (if it exists).

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  • Polite busy-waiting with WRPAUSE on SPARC

    - by Dave
    Unbounded busy-waiting is an poor idea for user-space code, so we typically use spin-then-block strategies when, say, waiting for a lock to be released or some other event. If we're going to spin, even briefly, then we'd prefer to do so in a manner that minimizes performance degradation for other sibling logical processors ("strands") that share compute resources. We want to spin politely and refrain from impeding the progress and performance of other threads — ostensibly doing useful work and making progress — that run on the same core. On a SPARC T4, for instance, 8 strands will share a core, and that core has its own L1 cache and 2 pipelines. On x86 we have the PAUSE instruction, which, naively, can be thought of as a hardware "yield" operator which temporarily surrenders compute resources to threads on sibling strands. Of course this helps avoid intra-core performance interference. On the SPARC T2 our preferred busy-waiting idiom was "RD %CCR,%G0" which is a high-latency no-nop. The T4 provides a dedicated and extremely useful WRPAUSE instruction. The processor architecture manuals are the authoritative source, but briefly, WRPAUSE writes a cycle count into the the PAUSE register, which is ASR27. Barring interrupts, the processor then delays for the requested period. There's no need for the operating system to save the PAUSE register over context switches as it always resets to 0 on traps. Digressing briefly, if you use unbounded spinning then ultimately the kernel will preempt and deschedule your thread if there are other ready threads than are starving. But by using a spin-then-block strategy we can allow other ready threads to run without resorting to involuntary time-slicing, which operates on a long-ish time scale. Generally, that makes your application more responsive. In addition, by blocking voluntarily we give the operating system far more latitude regarding power management. Finally, I should note that while we have OS-level facilities like sched_yield() at our disposal, yielding almost never does what you'd want or naively expect. Returning to WRPAUSE, it's natural to ask how well it works. To help answer that question I wrote a very simple C/pthreads benchmark that launches 8 concurrent threads and binds those threads to processors 0..7. The processors are numbered geographically on the T4, so those threads will all be running on just one core. Unlike the SPARC T2, where logical CPUs 0,1,2 and 3 were assigned to the first pipeline, and CPUs 4,5,6 and 7 were assigned to the 2nd, there's no fixed mapping between CPUs and pipelines in the T4. And in some circumstances when the other 7 logical processors are idling quietly, it's possible for the remaining logical processor to leverage both pipelines. Some number T of the threads will iterate in a tight loop advancing a simple Marsaglia xor-shift pseudo-random number generator. T is a command-line argument. The main thread loops, reporting the aggregate number of PRNG steps performed collectively by those T threads in the last 10 second measurement interval. The other threads (there are 8-T of these) run in a loop busy-waiting concurrently with the T threads. We vary T between 1 and 8 threads, and report on various busy-waiting idioms. The values in the table are the aggregate number of PRNG steps completed by the set of T threads. The unit is millions of iterations per 10 seconds. For the "PRNG step" busy-waiting mode, the busy-waiting threads execute exactly the same code as the T worker threads. We can easily compute the average rate of progress for individual worker threads by dividing the aggregate score by the number of worker threads T. I should note that the PRNG steps are extremely cycle-heavy and access almost no memory, so arguably this microbenchmark is not as representative of "normal" code as it could be. And for the purposes of comparison I included a row in the table that reflects a waiting policy where the waiting threads call poll(NULL,0,1000) and block in the kernel. Obviously this isn't busy-waiting, but the data is interesting for reference. _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } _td { border: 1px green solid; } _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } Aggregate progress T = #worker threads Wait Mechanism for 8-T threadsT=1T=2T=3T=4T=5T=6T=7T=8 Park thread in poll() 32653347334833483348334833483348 no-op 415 831 124316482060249729303349 RD %ccr,%g0 "pause" 14262429269228623013316232553349 PRNG step 412 829 124616702092251029303348 WRPause(8000) 32443361333133483349334833483348 WRPause(4000) 32153308331533223347334833473348 WRPause(1000) 30853199322432513310334833483348 WRPause(500) 29173070315032223270330933483348 WRPause(250) 26942864294930773205338833483348 WRPause(100) 21552469262227902911321433303348

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  • Can a recursive function have iterations/loops?

    - by Omega
    I've been studying about recursive functions, and apparently, they're functions that call themselves, and don't use iterations/loops (otherwise it wouldn't be a recursive function). However, while surfing the web for examples (the 8-queens-recursive problem), I found this function: private boolean placeQueen(int rows, int queens, int n) { boolean result = false; if (row < n) { while ((queens[row] < n - 1) && !result) { queens[row]++; if (verify(row,queens,n)) { ok = placeQueen(row + 1,queens,n); } } if (!result) { queens[row] = -1; } }else{ result = true; } return result; } There is a while loop involved. ... so I'm a bit lost now. Can I use loops or not?

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  • Tool for creating Spritesheet? and Tips

    - by Spooks
    I am looking for a tool that I can use to create sprite sheet easily. Right now I am using Illustrator, but I can never get the center of the character in the exact position, so it looks like it is moving around(even though its always in one place), while being loop through the sprite sheet. Is there any better tools that I can be using? Also what kind of tips would you give for working with a sprite sheet? Should I create each part of the character in individual layers (left arm, right arm, body, etc.) or everything at once? any other tips would also be helpful! thank you

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