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• Why are Asynchronous processes not called Synchronous?

  - by Balk

  So I'm a little confused by this terminology. Everyone refers to "Asynchronous" computing as running different processes on seperate threads, which gives the illusion that these processes are running at the same time. This is not the definition of the word asynchronous. a·syn·chro·nous –adjective 1. not occurring at the same time. 2. (of a computer or other electrical machine) having each operation started only after the preceding operation is completed. What am I not understanding here?

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• Can I use MPI_Probe to probe messsages sent by any collective operation?

  - by takwing

  In my code I have a server process repeatedly probing for incoming messages, which come in two types. One type of the two will be sent once by each process to give hint to the server process about its termination. I was wondering if it is valid to use MPI_Broadcast to broadcast these termination messages and use MPI_Probe to probe their arrivals. I tried using this combination but it failed. This failure might have been caused by some other things. So I would like anyone who knows about this to confirm. Cheers.

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• [C++] Needed: A simple C++ container (stack, linked list) that is thread-safe for writing

  - by conradlee

  I am writing a multi-threaded program using OpenMP in C++. At one point my program forks into many threads, each of which need to add "jobs" to some container that keeps track of all added jobs. Each job can just be a pointer to some object. Basically, I just need the add pointers to some container from several threads at the same time. Is there a simple solution that performs well? After some googling, I found that STL containers are not thread-safe. Some stackoverflow threads address this question, but none form a consensus on a simple solution.

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• Take advantage of multiple cores executing SQL statements

  - by willvv

  I have a small application that reads XML files and inserts the information on a SQL DB. There are ~ 300 000 files to import, each one with ~ 1000 records. I started the application on 20% of the files and it has been running for 18 hours now, I hope I can improve this time for the rest of the files. I'm not using a multi-thread approach, but since the computer I'm running the process on has 4 cores I was thinking on doing it to get some improvement on the performance (although I guess the main problem is the I/O and not only the processing). I was thinking on using the BeginExecutingNonQuery() method on the SqlCommand object I create for each insertion, but I don't know if I should limit the max amount of simultaneous threads (nor I know how to do it). What's your advice to get the best CPU utilization? Thanks

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• how to cancel an awaiting task c#

  - by user1748906

  I am trying to cancel a task awaiting for network IO using CancellationTokenSource, but I have to wait until TcpClient connects: try { while (true) { token.Token.ThrowIfCancellationRequested(); Thread.Sleep(int.MaxValue); //simulating a TcpListener waiting for request } } any ideas ? Secondly, is it OK to start each client in a separate task ?

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• Parallelism in .NET – Part 5, Partitioning of Work

  - by Reed

  When parallelizing any routine, we start by decomposing the problem.  Once the problem is understood, we need to break our work into separate tasks, so each task can be run on a different processing element.  This process is called partitioning. Partitioning our tasks is a challenging feat.  There are opposing forces at work here: too many partitions adds overhead, too few partitions leaves processors idle.  Trying to work the perfect balance between the two extremes is the goal for which we should aim.  Luckily, the Task Parallel Library automatically handles much of this process.  However, there are situations where the default partitioning may not be appropriate, and knowledge of our routines may allow us to guide the framework to making better decisions. First off, I’d like to say that this is a more advanced topic.  It is perfectly acceptable to use the parallel constructs in the framework without considering the partitioning taking place.  The default behavior in the Task Parallel Library is very well-behaved, even for unusual work loads, and should rarely be adjusted.  I have found few situations where the default partitioning behavior in the TPL is not as good or better than my own hand-written partitioning routines, and recommend using the defaults unless there is a strong, measured, and profiled reason to avoid using them.  However, understanding partitioning, and how the TPL partitions your data, helps in understanding the proper usage of the TPL. I indirectly mentioned partitioning while discussing aggregation.  Typically, our systems will have a limited number of Processing Elements (PE), which is the terminology used for hardware capable of processing a stream of instructions.  For example, in a standard Intel i7 system, there are four processor cores, each of which has two potential hardware threads due to Hyperthreading.  This gives us a total of 8 PEs – theoretically, we can have up to eight operations occurring concurrently within our system. In order to fully exploit this power, we need to partition our work into Tasks.  A task is a simple set of instructions that can be run on a PE.  Ideally, we want to have at least one task per PE in the system, since fewer tasks means that some of our processing power will be sitting idle.  A naive implementation would be to just take our data, and partition it with one element in our collection being treated as one task.  When we loop through our collection in parallel, using this approach, we’d just process one item at a time, then reuse that thread to process the next, etc.  There’s a flaw in this approach, however.  It will tend to be slower than necessary, often slower than processing the data serially. The problem is that there is overhead associated with each task.  When we take a simple foreach loop body and implement it using the TPL, we add overhead.  First, we change the body from a simple statement to a delegate, which must be invoked.  In order to invoke the delegate on a separate thread, the delegate gets added to the ThreadPool’s current work queue, and the ThreadPool must pull this off the queue, assign it to a free thread, then execute it.  If our collection had one million elements, the overhead of trying to spawn one million tasks would destroy our performance. The answer, here, is to partition our collection into groups, and have each group of elements treated as a single task.  By adding a partitioning step, we can break our total work into small enough tasks to keep our processors busy, but large enough tasks to avoid overburdening the ThreadPool.  There are two clear, opposing goals here: Always try to keep each processor working, but also try to keep the individual partitions as large as possible. When using Parallel.For, the partitioning is always handled automatically.  At first, partitioning here seems simple.  A naive implementation would merely split the total element count up by the number of PEs in the system, and assign a chunk of data to each processor.  Many hand-written partitioning schemes work in this exactly manner.  This perfectly balanced, static partitioning scheme works very well if the amount of work is constant for each element.  However, this is rarely the case.  Often, the length of time required to process an element grows as we progress through the collection, especially if we’re doing numerical computations.  In this case, the first PEs will finish early, and sit idle waiting on the last chunks to finish.  Sometimes, work can decrease as we progress, since previous computations may be used to speed up later computations.  In this situation, the first chunks will be working far longer than the last chunks.  In order to balance the workload, many implementations create many small chunks, and reuse threads.  This adds overhead, but does provide better load balancing, which in turn improves performance. The Task Parallel Library handles this more elaborately.  Chunks are determined at runtime, and start small.  They grow slowly over time, getting larger and larger.  This tends to lead to a near optimum load balancing, even in odd cases such as increasing or decreasing workloads.  Parallel.ForEach is a bit more complicated, however. When working with a generic IEnumerable<T>, the number of items required for processing is not known in advance, and must be discovered at runtime.  In addition, since we don’t have direct access to each element, the scheduler must enumerate the collection to process it.  Since IEnumerable<T> is not thread safe, it must lock on elements as it enumerates, create temporary collections for each chunk to process, and schedule this out.  By default, it uses a partitioning method similar to the one described above.  We can see this directly by looking at the Visual Partitioning sample shipped by the Task Parallel Library team, and available as part of the Samples for Parallel Programming.  When we run the sample, with four cores and the default, Load Balancing partitioning scheme, we see this: The colored bands represent each processing core.  You can see that, when we started (at the top), we begin with very small bands of color.  As the routine progresses through the Parallel.ForEach, the chunks get larger and larger (seen by larger and larger stripes). Most of the time, this is fantastic behavior, and most likely will out perform any custom written partitioning.  However, if your routine is not scaling well, it may be due to a failure in the default partitioning to handle your specific case.  With prior knowledge about your work, it may be possible to partition data more meaningfully than the default Partitioner. There is the option to use an overload of Parallel.ForEach which takes a Partitioner<T> instance.  The Partitioner<T> class is an abstract class which allows for both static and dynamic partitioning.  By overriding Partitioner<T>.SupportsDynamicPartitions, you can specify whether a dynamic approach is available.  If not, your custom Partitioner<T> subclass would override GetPartitions(int), which returns a list of IEnumerator<T> instances.  These are then used by the Parallel class to split work up amongst processors.  When dynamic partitioning is available, GetDynamicPartitions() is used, which returns an IEnumerable<T> for each partition.  If you do decide to implement your own Partitioner<T>, keep in mind the goals and tradeoffs of different partitioning strategies, and design appropriately. The Samples for Parallel Programming project includes a ChunkPartitioner class in the ParallelExtensionsExtras project.  This provides example code for implementing your own, custom allocation strategies, including a static allocator of a given chunk size.  Although implementing your own Partitioner<T> is possible, as I mentioned above, this is rarely required or useful in practice.  The default behavior of the TPL is very good, often better than any hand written partitioning strategy.

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• How can I print text fields at the right coordinates?

  - by Milad

  I don't have any background in programming and this is my first shot. I wrote a Delphi program that is supposed to print on a result sheet. I work in an institute and we have to establish hundreds of result sheets every 2 months. It's really difficult to do that and different handwriting is also an important issue. I have this code: if PrintDialog.Execute() then begin with MyPrinter do begin MyPrinter.BeginDoc();//Start Printing //Prints First Name MyPrinter.Canvas.TextOut(FirstNameX,FirstNameY,EditFirstName.Text); //Prints Last Name MyPrinter.Canvas.TextOut(LastNameX,LastNameY,EditLastName.Text); //Prints Level MyPrinter.Canvas.TextOut(LevelX,LevelY,EditLevel.Text); //Prints Date MyPrinter.Canvas.TextOut(DateX,DateY,MEditDate.Text); //Prints Student Number MyPrinter.Canvas.TextOut(StdNumX,StdNumY,EditStdnumber.Text); .... MyPrinter.EndDoc();//End Printing end; end; I can't get the right coordinates to print properly. Am I missing something? How can I set the right coordinates? You know TPrinter uses pixels to get the coordinates but papers are measured in inches or centimeters. I'm really confused. I appreciate any help.

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• iPhone Mobile Safari, How many max parallel http connections?

  - by user316994

  I would like to use parallel AJAX HTTP requests with iPhone Mobile Safari (OS4). What is the max number of parallel connections?

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• Is there a way to control how pytest-xdist runs tests in parallel?

  - by superselector

  I have the following directory layout: runner.py lib/ tests/ testsuite1/ testsuite1.py testsuite2/ testsuite2.py testsuite3/ testsuite3.py testsuite4/ testsuite4.py The format of testsuite*.py modules is as follows: import pytest class testsomething: def setup_class(self): ''' do some setup ''' # Do some setup stuff here def teardown_class(self): '''' do some teardown''' # Do some teardown stuff here def test1(self): # Do some test1 related stuff def test2(self): # Do some test2 related stuff .... .... .... def test40(self): # Do some test40 related stuff if __name__=='__main()__' pytest.main(args=[os.path.abspath(__file__)]) The problem I have is that I would like to execute the 'testsuites' in parallel i.e. I want testsuite1, testsuite2, testsuite3 and testsuite4 to start execution in parallel but individual tests within the testsuites need to be executed serially. When I use the 'xdist' plugin from py.test and kick off the tests using 'py.test -n 4', py.test is gathering all the tests and randomly load balancing the tests among 4 workers. This leads to the 'setup_class' method to be executed every time of each test within a 'testsuitex.py' module (which defeats my purpose. I want setup_class to be executed only once per class and tests executed serially there after). Essentially what I want the execution to look like is: worker1: executes all tests in testsuite1.py serially worker2: executes all tests in testsuite2.py serially worker3: executes all tests in testsuite3.py serially worker4: executes all tests in testsuite4.py serially while worker1, worker2, worker3 and worker4 are all executed in parallel. Is there a way to achieve this in 'pytest-xidst' framework? The only option that I can think of is to kick off different processes to execute each test suite individually within runner.py: def test_execute_func(testsuite_path): subprocess.process('py.test %s' % testsuite_path) if __name__=='__main__': #Gather all the testsuite names for each testsuite: multiprocessing.Process(test_execute_func,(testsuite_path,))

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• How can I find the right UV coordinates for interpolating a bezier curve?

  - by ssb

  I'll let this picture do the talking. I'm trying to create a mesh from a bezier curve and then add a texture to it. The problem here is that the interpolation points along the curve do not increase linearly, so points farther from the control point (near the endpoints) stretch and those in the bend contract, causing the texture to be uneven across the curve, which can be problematic when using a pattern like stripes on a road. How can I determine how far along the curve the vertices actually are so I can give a proper UV coordinate? EDIT: Allow me to clarify that I'm not talking about the trapezoidal distortion of the roads. That I know is normal and I'm not concerned about. I've updated the image to show more clearly where my concerns are. Interpolating over the curve I get 10 segments, but each of these 10 segments is not spaced at an equal point along the curve, so I have to account for this in assigning UV data to vertices or else the road texture will stretch/shrink depending on how far apart vertices are at that particular part of the curve.

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• UV Atlas Generation and Seam Removal

  - by P. Avery

  I'm generating light maps for scene mesh objects using DirectX's UV Atlas Tool( D3DXUVAtlasCreate() ). I've succeeded in generating an atlas, however, when I try to render the mesh object using the atlas the seams are visible on the mesh. Below are images of a lightmap generated for a cube. Here is the code I use to generate a uv atlas for a cube: struct sVertexPosNormTex { D3DXVECTOR3 vPos, vNorm; D3DXVECTOR2 vUV; sVertexPosNormTex(){} sVertexPosNormTex( D3DXVECTOR3 v, D3DXVECTOR3 n, D3DXVECTOR2 uv ) { vPos = v; vNorm = n; vUV = uv; } ~sVertexPosNormTex() { } }; // create a light map texture to fill programatically hr = D3DXCreateTexture( pd3dDevice, 128, 128, 1, 0, D3DFMT_A8R8G8B8, D3DPOOL_MANAGED, &pLightmap ); if( FAILED( hr ) ) { DebugStringDX( "Main", "Failed to D3DXCreateTexture( lightmap )", __LINE__, hr ); return hr; } // get the zero level surface from the texture IDirect3DSurface9 *pS = NULL; pLightmap->GetSurfaceLevel( 0, &pS ); // clear surface pd3dDevice->ColorFill( pS, NULL, D3DCOLOR_XRGB( 0, 0, 0 ) ); // load a sample mesh DWORD dwcMaterials = 0; LPD3DXBUFFER pMaterialBuffer = NULL; V_RETURN( D3DXLoadMeshFromX( L"cube3.x", D3DXMESH_MANAGED, pd3dDevice, &pAdjacency, &pMaterialBuffer, NULL, &dwcMaterials, &g_pMesh ) ); // generate adjacency DWORD *pdwAdjacency = new DWORD[ 3 * g_pMesh->GetNumFaces() ]; g_pMesh->GenerateAdjacency( 1e-6f, pdwAdjacency ); // create light map coordinates LPD3DXMESH pMesh = NULL; LPD3DXBUFFER pFacePartitioning = NULL, pVertexRemapArray = NULL; FLOAT resultStretch = 0; UINT numCharts = 0; hr = D3DXUVAtlasCreate( g_pMesh, 0, 0, 128, 128, 3.5f, 0, pdwAdjacency, NULL, NULL, NULL, NULL, NULL, 0, &pMesh, &pFacePartitioning, &pVertexRemapArray, &resultStretch, &numCharts ); if( SUCCEEDED( hr ) ) { // release and set mesh SAFE_RELEASE( g_pMesh ); g_pMesh = pMesh; // write mesh to file hr = D3DXSaveMeshToX( L"cube4.x", g_pMesh, 0, ( const D3DXMATERIAL* )pMaterialBuffer->GetBufferPointer(), NULL, dwcMaterials, D3DXF_FILEFORMAT_TEXT ); if( FAILED( hr ) ) { DebugStringDX( "Main", "Failed to D3DXSaveMeshToX() at OnD3D9CreateDevice()", __LINE__, hr ); } // fill the the light map hr = BuildLightmap( pS, g_pMesh ); if( FAILED( hr ) ) { DebugStringDX( "Main", "Failed to BuildLightmap()", __LINE__, hr ); } } else { DebugStringDX( "Main", "Failed to D3DXUVAtlasCreate() at OnD3D9CreateDevice()", __LINE__, hr ); } SAFE_RELEASE( pS ); SAFE_DELETE_ARRAY( pdwAdjacency ); SAFE_RELEASE( pFacePartitioning ); SAFE_RELEASE( pVertexRemapArray ); SAFE_RELEASE( pMaterialBuffer ); Here is code to fill lightmap texture: HRESULT BuildLightmap( IDirect3DSurface9 *pS, LPD3DXMESH pMesh ) { HRESULT hr = S_OK; // validate lightmap texture surface and mesh if( !pS || !pMesh ) return E_POINTER; // lock the mesh vertex buffer sVertexPosNormTex *pV = NULL; pMesh->LockVertexBuffer( D3DLOCK_READONLY, ( void** )&pV ); // lock the mesh index buffer WORD *pI = NULL; pMesh->LockIndexBuffer( D3DLOCK_READONLY, ( void** )&pI ); // get the lightmap texture surface description D3DSURFACE_DESC desc; pS->GetDesc( &desc ); // lock the surface rect to fill with color data D3DLOCKED_RECT rct; hr = pS->LockRect( &rct, NULL, 0 ); if( FAILED( hr ) ) { DebugStringDX( "main.cpp:", "Failed to IDirect3DTexture9::LockRect()", __LINE__, hr ); return hr; } // iterate the pixels of the lightmap texture // check each pixel to see if it lies between the uv coordinates of a cube face BYTE *pBuffer = ( BYTE* )rct.pBits; for( UINT y = 0; y < desc.Height; ++y ) { BYTE* pBufferRow = ( BYTE* )pBuffer; for( UINT x = 0; x < desc.Width * 4; x+=4 ) { // determine the pixel's uv coordinate D3DXVECTOR2 p( ( ( float )x / 4.0f ) / ( float )desc.Width + 0.5f / 128.0f, y / ( float )desc.Height + 0.5f / 128.0f ); // for each face of the mesh // check to see if the pixel lies within the face's uv coordinates for( UINT i = 0; i < 3 * pMesh->GetNumFaces(); i +=3 ) { sVertexPosNormTex v[ 3 ]; v[ 0 ] = pV[ pI[ i + 0 ] ]; v[ 1 ] = pV[ pI[ i + 1 ] ]; v[ 2 ] = pV[ pI[ i + 2 ] ]; if( TexcoordIsWithinBounds( v[ 0 ].vUV, v[ 1 ].vUV, v[ 2 ].vUV, p ) ) { // the pixel lies b/t the uv coordinates of a cube face // light contribution functions aren't needed yet //D3DXVECTOR3 vPos = TexcoordToPos( v[ 0 ].vPos, v[ 1 ].vPos, v[ 2 ].vPos, v[ 0 ].vUV, v[ 1 ].vUV, v[ 2 ].vUV, p ); //D3DXVECTOR3 vNormal = v[ 0 ].vNorm; // set the color of this pixel red( for demo ) BYTE ba[] = { 0, 0, 255, 255, }; //ComputeContribution( vPos, vNormal, g_sLight, ba ); // copy the byte array into the light map texture memcpy( ( void* )&pBufferRow[ x ], ( void* )ba, 4 * sizeof( BYTE ) ); } } } // go to next line of the texture pBuffer += rct.Pitch; } // unlock the surface rect pS->UnlockRect(); // unlock mesh vertex and index buffers pMesh->UnlockIndexBuffer(); pMesh->UnlockVertexBuffer(); // write the surface to file hr = D3DXSaveSurfaceToFile( L"LightMap.jpg", D3DXIFF_JPG, pS, NULL, NULL ); if( FAILED( hr ) ) DebugStringDX( "Main.cpp", "Failed to D3DXSaveSurfaceToFile()", __LINE__, hr ); return hr; } bool TexcoordIsWithinBounds( const D3DXVECTOR2 &t0, const D3DXVECTOR2 &t1, const D3DXVECTOR2 &t2, const D3DXVECTOR2 &p ) { // compute vectors D3DXVECTOR2 v0 = t1 - t0, v1 = t2 - t0, v2 = p - t0; float f00 = D3DXVec2Dot( &v0, &v0 ); float f01 = D3DXVec2Dot( &v0, &v1 ); float f02 = D3DXVec2Dot( &v0, &v2 ); float f11 = D3DXVec2Dot( &v1, &v1 ); float f12 = D3DXVec2Dot( &v1, &v2 ); // Compute barycentric coordinates float invDenom = 1 / ( f00 * f11 - f01 * f01 ); float fU = ( f11 * f02 - f01 * f12 ) * invDenom; float fV = ( f00 * f12 - f01 * f02 ) * invDenom; // Check if point is in triangle if( ( fU >= 0 ) && ( fV >= 0 ) && ( fU + fV < 1 ) ) return true; return false; } Screenshot Lightmap I believe the problem comes from the difference between the lightmap uv coordinates and the pixel center coordinates...for example, here are the lightmap uv coordinates( generated by D3DXUVAtlasCreate() ) for a specific face( tri ) within the mesh, keep in mind that I'm using the mesh uv coordinates to write the pixels for the texture: v[ 0 ].uv = D3DXVECTOR2( 0.003581, 0.295631 ); v[ 1 ].uv = D3DXVECTOR2( 0.003581, 0.003581 ); v[ 2 ].uv = D3DXVECTOR2( 0.295631, 0.003581 ); the lightmap texture size is 128 x 128 pixels. The upper-left pixel center coordinates are: float halfPixel = 0.5 / 128 = 0.00390625; D3DXVECTOR2 pixelCenter = D3DXVECTOR2( halfPixel, halfPixel ); will the mapping and sampling of the lightmap texture will require that an offset be taken into account or that the uv coordinates are snapped to the pixel centers..? ...Any ideas on the best way to approach this situation would be appreciated...What are the common practices?

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• How can I test if a point lies between two parallel lines?

  - by Harold

  In the game I'm designing there is a blast that shoots out from an origin point towards the direction of the mouse. The width of this blast is always going to be the same. Along the bottom of the screen (what's currently) squares move about which should be effected by the blast that the player controls. Currently I am trying to work out a way to discover if the corners of these squares are within the blast's two bounding lines. I thought the best way to do this would be to rotate the corners of the square around an origin point as if the blast were completely horizontal and see if the Y values of the corners were less than or equal to the width of the blast which would mean that they lie within the effected region, but I can't work out

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• How to get scripted programs governing game entities run in parallel with a game loop?

  - by Jim

  I recently discovered Crobot which is (briefly) a game where each player codes a virtual robot in a pseudo-C language. Each robot is then put in an arena where it fights against other robots. A robots' source code has this shape : /* Beginning file robot.r */ main() { while (1) { /* Do whatever you want */ ... move(); ... fire(); } } /* End file robot.r */ You can see that : The code is totally independent from any library/include Some predefined functions are available (move, fire, etc…) The program has its own game loop, and consequently is not called every frame My question is: How to achieve a similar result using scripted languages in collaboration with a C/C++ main program ? I found a possible approach using Python, multi-threading and shared memory, although I am not sure yet that it is possible this way. TCP/IP seems a bit too complicated for this kind of application.

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• How to prioritize tasks when you have multiple programming projects running in parallel?

  - by Vinko Vrsalovic

  Say you have 5 customers, you develop 2 or 3 different projects for each. Each project has Xi tasks. Each project takes from 2 to 10 man weeks. Given that there are few resources, it is desired to minimize the management overhead. Two questions in this scenario: What tools would you use to prioritize the tasks and track their completion, while tending to minimize the overhead? What criteria would you take into consideration to determine which task to assign to the next available resource given that the primary objective is to increase throughput (more projects finished per time unit, this objective conflicts with starting one project and finishing it and then moving on to the next)? Ideas, management techniques, algorithms are welcome

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• Why is lowlatency kernel not being updated in parallel with the generic kernel?

  - by FlabbergastedPickle

  All, Any idea when we'll see updates to the lowlatency version of the Ubuntu 12.04 kernel? It is still stuck at 3.2.0.23 whereas the generic kernel is already several updates ahead of it at a version 3.2.0.25? NB: I am using a 64-bit version but I don't think this is limited to the 64-bit kernels alone but rather affects both 32-bit and 64-bit builds. Please do correct me if I am wrong about this.

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• How to find optimal path visit every node with parallel workers complicated by dynamic edge costs?

  - by Aaron Anodide

  Say you have an acyclic directed graph with weighted edges and create N workers. My goal is to calculate the optimal way those workers can traverse the entire graph in parralel. However, edge costs may change along the way. Example: A -1-> B A -2-> C B -3-> C (if A has already been visited) B -5-> C (if A has not already been visited) Does what I describe lend itself to a standard algorithmic approach, or alternately can someone suggest if I'm looking at this in an inherently flawed way (i have an intuition I might be)?

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• Shows how to use the new Tasks namespace to download multiple documents in parallel.

  In C# 4.0, Task parallelism is the lowest-level approach to parallelization with PFX. The classes for working at this level are defined in the System.Threading.Tasks namespace.  read moreBy Peter BrombergDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Virtual PC, XP mode. Bidirectional parallel port physical LPT1 not available in VPC XP mode?

  - by Tom Merklin

  I need my LPT1 port to be available in XP mode. In the "guest" window, it shows up in system hardware, but it is not available to the application. If I look into Tools, settings there are no parallel port available? How can I fix this problem? (If I use VMWare Workstation XP mode, I load a driver and it works perfect).

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• Can multiple windows users connect to a Mac Mini OS X Server and run applications in parallel?

  - by ilight

  I want to validate the current situation :- I have multiple users who have to use designing applications like Adobe Photoshop, Illustrator etc and maybe some Mac specific applications like iWork and they need to be working on the applications in parallel. Can I setup a Mac Mini OS X Server and create separate user accounts and give to these users so that they can remote login to the OS X Server simultaneously from their Windows machines and use any application they want? In crux, can they share the server resources and applications from their windows machines?

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• When can a freely moving sphere escape from a ‘cage’ defined by a set of impassible coordinates?

  - by RGrey

  Hopefully there are some computational geometry folks here who can help me out with the following problem - Please imagine that I take a freely moving ball in 3-space and create a 'cage' around it by defining a set of impassible coordinates, Sc (i.e. points in 3-space that no part of the diffusing ball is allowed to overlap). These points reside within the volume, V(cage), of some larger sphere, where V(cage) V(ball). Provided the set of impassible coordinates, Sc, is there a computationally efficient and/or nice way to determine if the ball can ever escape the cage?

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• Codeigniter Image Library Cropping an Image with 2 sets of coordinates to make square anywhere?

  - by chris

  Spending time reading through the docs, and searching for examples. I understand cropping an image from top 0, and left 0 is pretty straight forward. However. I would like to pass 2 sets of coordinates, a starting point and an ending point. Four Points, a Square that is defined anywhere. However from the examples I am finding, and from what I gather the rendition is not going to let me do this. codeigniter so I am seeking confirmation on this thought, is it true that I can only provide end points from 0, and it crops a square based on said end points or can I actually specify an x start, an x end, and similar for y? Or is there some other technique I can use within codeigniter that will allow me to pass for coordinates for starting and ending points?

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• What are the z-coordinates in Cocoa mouse events for?

  - by gf

  Interestingly i didn't find the answer for this seemingly trivial question - Cocoas mouse events have z-coordinates - what are they for?

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• Is there a ways to make google store coordinates in the android map?

  - by Pavel

  Hi. I'm in the middle of developing android app using google map. My question is - how to store coordinates with google map and display them later on? I know how to use canvas, how to draw it etc. but I want to store those coordinates with google map - just like with the google maps feature on internet. When I log in I can see points I've put on the map straight away. Can someone please tell me how to do that? There must be a way. Any answers greatly appreciated!

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• Decal implementation

  - by dreta

  I had issues finding information about decals, so maybe this question will help others. The implementation is for a forward renderer. Could somebody confirm if i got decal implementation right? You define a cube of any dimension that'll define the projection volume in common space. You check for triangle intersection with the defined cube to recieve triangles that the projection will affect. You clip these triangles and save them. You then use matrix tricks to calculate UV coordinates for the saved triangles that'll reference the texture you're projecting. To do this you take the vectors representing height, width and depth of the cube in common space, so that f.e. the bottom left corner is the origin. You put that in a matrix as the i, j, k unit vectors, set the translation for the cube, then you inverse this matrix. You multiply the vertices of the saved triangles by this matrix, that way you get their coordinates inside of a 0 to 1 size cube that you use as the UV coordinates. This way you have the original triangles you're projecting onto and you have UV coordinates for them (the UV coordinates are referencing the texture you're projecting). Then you rerender the saved triangles onto the scene and they overwrite the area of projection with the projected image. Now the questions that i couldn't find answers for. Is the last point right? I've never done software clipping, but it seems error prone enough, due to limited precision, that the'll be some z fighting occuring for the projected texture. Also is the way of getting UV coordinates correct?

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• Split up a screen into regions

  - by nexen

  My task: I want to split up a screen into 3 regions for buffs-bar (with picked items), score-info and a game-map. It doesn't matter are regions intersect with each other or not. For example: I have a screen with width=1; height=1 and the origin of coordinates (0;0) is the left bottom point. I have 3 functions: draw items, draw info, draw map. If I use it without any matrix transformations, it draws fullscreen, because it's vertex coordinates are from 0;0 to 1;1. (pseudo-code) drawItems(); drawInfo(); drawMap(); And after that I see only map onto info onto items. My goal: I have some matrixes for transformation vertexes with 0;0-1;1 coordinates to strict regions. There is only one thing, what I need to do - set matrix before drawing. So my call of drawItems-function is like: (pseudo-code) adjustViewMatrixes_andSomethingElse(items.position_of_the_region_there_it_should_be_drawn, items.sizes_of_region_to_draw); setItemsMatrix(); drawItems(); //the same function with vertex coordinates 0;0->1;1, //but it draws in other coordinates, //because I have just set the matrix for region I know only some people will understand me, so there is a picture with regions which I need to make. Every region has 0;0 - 1;1 inner coordinates.

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