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• matrix multiplication with MPI [on hold]

  - by user3695701

  I'm working on an assignment on matrix multiplication with MPI. A*B=C. the requirement is that B should be vertically partitioned. Here's what I intend to do: broadcast matrix A to all processes and scatter B into several slices with each slice containing n/p columns. The following code only works when the number of process(p) is 1. when p1(say 2), I got [cluster2:21080] *** Process received signal *** [cluster2:21080] Signal: Segmentation fault (11) [cluster2:21080] Signal code: Address not mapped (1) [cluster2:21080] Failing at address: (nil) [cluster2:21080] [ 0] /lib/libpthread.so.0(+0xf8f0) [0x7f49f38108f0] [cluster2:21080] [ 1] /lib/libc.so.6(memcpy+0xe1) [0x7f49f35024c1] [cluster2:21080] [ 2] /usr/lib/libmpi.so.0(ompi_convertor_unpack+0x121)[0x7f49f47c88e1] [cluster2:21080] [ 3] /usr/lib/openmpi/lib/openmpi/mca_pml_ob1.so(+0x8a26) [0x7f49f0dcea26] [cluster2:21080] [ 4] /usr/lib/openmpi/lib/openmpi/mca_btl_tcp.so(+0x662c) [0x7f49efce462c] [cluster2:21080] [ 5] /usr/lib/libopen-pal.so.0(+0x1ede8) [0x7f49f42e0de8] [cluster2:21080] [ 6] /usr/lib/libopen-pal.so.0(opal_progress+0x99) [0x7f49f42d5369] [cluster2:21080] [ 7] /usr/lib/openmpi/lib/openmpi/mca_pml_ob1.so(+0x5585) [0x7f49f0dcb585] [cluster2:21080] [ 8] /usr/lib/openmpi/lib/openmpi/mca_coll_tuned.so(+0xcc01) [0x7f49eeeb1c01] [cluster2:21080] [ 9] /usr/lib/openmpi/lib/openmpi/mca_coll_tuned.so(+0x266c) [0x7f49eeea766c] [cluster2:21080] [10] /usr/lib/openmpi/lib/openmpi/mca_coll_sync.so(+0x1388) [0x7f49ef0c0388] [cluster2:21080] [11] /usr/lib/libmpi.so.0(MPI_Bcast+0x10e) [0x7f49f47d025e] [cluster2:21080] [12] ./out(main+0x259) [0x401571] [cluster2:21080] [13] /lib/libc.so.6(__libc_start_main+0xfd) [0x7f49f3498c8d] [cluster2:21080] [14] ./out() [0x400f29] [cluster2:21080] *** End of error message *** Can someone help me? Thanks. //matrices A and B //double* A =(double *)malloc(n*n*sizeof(double)); //double* B =(double *)malloc(n*n*sizeof(double)); //code initializing A,B... //n is the size of the matrix //p is the number of processes //myrank is the rank of calling process MPI_Init (&argc, &argv); MPI_Comm_rank(MPI_COMM_WORLD, &myrank); MPI_Comm_size(MPI_COMM_WORLD, &p); //broadcast A to all processes MPI_Bcast (A, n*n, MPI_DOUBLE, 0, MPI_COMM_WORLD); MPI_Datatype tmp_type, col_type; // extract a slice from B MPI_Type_vector(n, num_of_col_per_slice, n, MPI_DOUBLE, &tmp_type); // position of the first (0) and each next (stride * sizeof(double) ) slice MPI_Type_create_resized(tmp_type, 0, n * sizeof(double), &col_type); MPI_Type_commit(&col_type); //scatter a slice of B to each process MPI_Scatter(B, 1, col_type, B+myrank*n/p, n * n/p, MPI_DOUBLE, 0, MPI_COMM_WORLD); //use blas function to calculate A*sliceOfB and store the resulting slice to C cblas_dgemm(CblasRowMajor, CblasNoTrans, CblasNoTrans, n, n/p, n, 1.0, A, n, B+myrank*n/p, n, 0.0, C+myrank*n/p, n); //gather all those resulting slices into C MPI_Gather (C+myrank*n/p, n*n/p, MPI_DOUBLE, C, n*n/p, MPI_DOUBLE, 0, MPI_COMM_WORLD);

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• A simple way to swap rows in a matrix for F#

  - by Wallhood

  Is there a simple way to swap the rows of a Matrix in F#?

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• importing animations in Blender, weird rotations/locations

  - by user975135

  This is for the Blender 2.6 API. There are two problems: 1. When I import a single animation frame from my animation file to Blender, all bones look fine. But when I import multiple (all of the frames), just the first one looks right, seems like newer frames are affected by older ones, so you get slightly off positions/rotations. This is true when both assigning PoseBone.matrix and PoseBone.matrix_basis. bone_index = 0 # for each frame: for frame_index in range(frame_count): # for each pose bone: add a key for bone_name in bone_names: # "bone_names" - a list of bone names I got earlier pose.bones[bone_name].matrix = animation_matrices[frame_index][bone_index] # "animation_matrices" - a nested list of matrices generated from reading a file # create the 'keys' for the Action from the poses pose.bones[bone_name].keyframe_insert('location', frame = frame_index+1) pose.bones[bone_name].keyframe_insert('rotation_euler', frame = frame_index+1) pose.bones[bone_name].keyframe_insert('scale', frame = frame_index+1) bone_index += 1 bone_index = 0 Again, it seems like previous frames are affecting latter ones, because if I import a single frame from the middle of the animation, it looks fine. 2. I can't assign armature-space animation matrices read from a file to a skeleton with hierarchy (parenting). In Blender 2.4 you could just assign them to PoseBone.poseMatrix and bones would deform perfectly whether the bones had a hierarchy or none at all. In Blender 2.6, there's PoseBone.matrix_basis and PoseBone.matrix. While matrix_basis is relative to parent bone, matrix isn't, the API says it's in object space. So it should have worked, but doesn't. So I guess we need to calculate a local space matrix from our armature-space animation matrices from the files. So I tried multiplying it ( PoseBone.matrix ) with PoseBone.parent.matrix.inverted() in both possible orders with no luck, still weird deformations.

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• Can someone explain the (reasons for the) implications of colum vs row major in multiplication/concatenation?

  - by sebf

  I am trying to learn how to construct view and projection matrices, and keep reaching difficulties in my implementation owing to my confusion about the two standards for matrices. I know how to multiply a matrix, and I can see that transposing before multiplication would completely change the result, hence the need to multiply in a different order. What I don't understand though is whats meant by only 'notational convention' - from the articles here and here the authors appear to assert that it makes no difference to how the matrix is stored, or transferred to the GPU, but on the second page that matrix is clearly not equivalent to how it would be laid out in memory for row-major; and if I look at a populated matrix in my program I see the translation components occupying the 4th, 8th and 12th elements. Given that: "post-multiplying with column-major matrices produces the same result as pre-multiplying with row-major matrices. " Why in the following snippet of code: Matrix4 r = t3 * t2 * t1; Matrix4 r2 = t1.Transpose() * t2.Transpose() * t3.Transpose(); Does r != r2 and why does pos3 != pos for: Vector4 pos = wvpM * new Vector4(0f, 15f, 15f, 1); Vector4 pos3 = wvpM.Transpose() * new Vector4(0f, 15f, 15f, 1); Does the multiplication process change depending on whether the matrices are row or column major, or is it just the order (for an equivalent effect?) One thing that isn't helping this become any clearer, is that when provided to DirectX, my column major WVP matrix is used successfully to transform vertices with the HLSL call: mul(vector,matrix) which should result in the vector being treated as row-major, so how can the column major matrix provided by my math library work?

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• Black Screen: How to set Projection/View Matrix

  - by Lisa

  I have a Windows Phone 8 C#/XAML with DirectX component project. I'm rendering some particles, but each particle is a rectangle versus a square (as I've set the vertices to be positions equally offset from each other). I used an Identity matrix in the view and projection matrix. I decided to add the windows aspect ratio to prevent the rectangles. But now I get a black screen. None of the particles are rendered now. I don't know what's wrong with my matrices. Can anyone see the problem? These are the default matrices in Microsoft's project example. View Matrix: XMVECTOR eye = XMVectorSet(0.0f, 0.7f, 1.5f, 0.0f); XMVECTOR at = XMVectorSet(0.0f, -0.1f, 0.0f, 0.0f); XMVECTOR up = XMVectorSet(0.0f, 1.0f, 0.0f, 0.0f); XMStoreFloat4x4(&m_constantBufferData.view, XMMatrixTranspose(XMMatrixLookAtRH(eye, at, up))); Projection Matrix: void CubeRenderer::CreateWindowSizeDependentResources() { Direct3DBase::CreateWindowSizeDependentResources(); float aspectRatio = m_windowBounds.Width / m_windowBounds.Height; float fovAngleY = 70.0f * XM_PI / 180.0f; if (aspectRatio < 1.0f) { fovAngleY /= aspectRatio; } XMStoreFloat4x4(&m_constantBufferData.projection, XMMatrixTranspose(XMMatrixPerspectiveFovRH(fovAngleY, aspectRatio, 0.01f, 100.0f))); } I've tried modifying them to use cocos2dx's WP8 example. XMMATRIX identityMatrix = XMMatrixIdentity(); float fovy = 60.0f; float aspect = m_windowBounds.Width / m_windowBounds.Height; float zNear = 0.1f; float zFar = 100.0f; float xmin, xmax, ymin, ymax; ymax = zNear * tanf(fovy * XM_PI / 360); ymin = -ymax; xmin = ymin * aspect; xmax = ymax * aspect; XMMATRIX tmpMatrix = XMMatrixPerspectiveOffCenterRH(xmin, xmax, ymin, ymax, zNear, zFar); XMMATRIX projectionMatrix = XMMatrixMultiply(tmpMatrix, identityMatrix); // View Matrix float fEyeX = m_windowBounds.Width * 0.5f; float fEyeY = m_windowBounds.Height * 0.5f; float fEyeZ = m_windowBounds.Height / 1.1566f; float fLookAtX = m_windowBounds.Width * 0.5f; float fLookAtY = m_windowBounds.Height * 0.5f; float fLookAtZ = 0.0f; float fUpX = 0.0f; float fUpY = 1.0f; float fUpZ = 0.0f; XMMATRIX tmpMatrix2 = XMMatrixLookAtRH(XMVectorSet(fEyeX,fEyeY,fEyeZ,0.f), XMVectorSet(fLookAtX,fLookAtY,fLookAtZ,0.f), XMVectorSet(fUpX,fUpY,fUpZ,0.f)); XMMATRIX viewMatrix = XMMatrixMultiply(tmpMatrix2, identityMatrix); XMStoreFloat4x4(&m_constantBufferData.view, viewMatrix); Vertex Shader cbuffer ModelViewProjectionConstantBuffer : register(b0) { //matrix model; matrix view; matrix projection; }; struct VertexInputType { float4 position : POSITION; float2 tex : TEXCOORD0; float4 color : COLOR; }; struct PixelInputType { float4 position : SV_POSITION; float2 tex : TEXCOORD0; float4 color : COLOR; }; PixelInputType main(VertexInputType input) { PixelInputType output; // Change the position vector to be 4 units for proper matrix calculations. input.position.w = 1.0f; //===================================== // TODO: ADDED for testing input.position.z = 0.0f; //===================================== // Calculate the position of the vertex against the world, view, and projection matrices. //output.position = mul(input.position, model); output.position = mul(input.position, view); output.position = mul(output.position, projection); // Store the texture coordinates for the pixel shader. output.tex = input.tex; // Store the particle color for the pixel shader. output.color = input.color; return output; } Before I render the shader, I set the view/projection matrices into the constant buffer void ParticleRenderer::SetShaderParameters() { ViewProjectionConstantBuffer* dataPtr; D3D11_MAPPED_SUBRESOURCE mappedResource; DX::ThrowIfFailed(m_d3dContext->Map(m_constantBuffer.Get(), 0, D3D11_MAP_WRITE_DISCARD, 0, &mappedResource)); dataPtr = (ViewProjectionConstantBuffer*)mappedResource.pData; dataPtr->view = m_constantBufferData.view; dataPtr->projection = m_constantBufferData.projection; m_d3dContext->Unmap(m_constantBuffer.Get(), 0); // Now set the constant buffer in the vertex shader with the updated values. m_d3dContext->VSSetConstantBuffers(0, 1, m_constantBuffer.GetAddressOf() ); // Set shader texture resource in the pixel shader. m_d3dContext->PSSetShaderResources(0, 1, &m_textureView); } Nothing, black screen... I tried so many different look at, eye, and up vectors. I tried transposing the matrices. I've set the particle center position to always be (0, 0, 0), I tried different positions too, just to make sure they're not being rendered offscreen.

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• VFP Unit Matrix Multiply problem on the iPhone

  - by Ian Copland

  Hi. I'm trying to write a Matrix3x3 multiply using the Vector Floating Point on the iPhone, however i'm encountering some problems. This is my first attempt at writing any ARM assembly, so it could be a faily simple solution that i'm not seeing. I've currently got a small application running using a maths library that i've written. I'm investigating into the benifits using the Vector Floating Point Unit would provide so i've taken my matrix multiply and converted it to asm. Previously the application would run without a problem, however now my objects will all randomly disappear. This seems to be caused by the results from my matrix multiply becoming NAN at some point. Heres the code IMatrix3x3 operator*(IMatrix3x3 & _A, IMatrix3x3 & _B) { IMatrix3x3 C; //C++ code for the simulator #if TARGET_IPHONE_SIMULATOR == true C.A0 = _A.A0 * _B.A0 + _A.A1 * _B.B0 + _A.A2 * _B.C0; C.A1 = _A.A0 * _B.A1 + _A.A1 * _B.B1 + _A.A2 * _B.C1; C.A2 = _A.A0 * _B.A2 + _A.A1 * _B.B2 + _A.A2 * _B.C2; C.B0 = _A.B0 * _B.A0 + _A.B1 * _B.B0 + _A.B2 * _B.C0; C.B1 = _A.B0 * _B.A1 + _A.B1 * _B.B1 + _A.B2 * _B.C1; C.B2 = _A.B0 * _B.A2 + _A.B1 * _B.B2 + _A.B2 * _B.C2; C.C0 = _A.C0 * _B.A0 + _A.C1 * _B.B0 + _A.C2 * _B.C0; C.C1 = _A.C0 * _B.A1 + _A.C1 * _B.B1 + _A.C2 * _B.C1; C.C2 = _A.C0 * _B.A2 + _A.C1 * _B.B2 + _A.C2 * _B.C2; //VPU ARM asm for the device #else //create a pointer to the Matrices IMatrix3x3 * pA = &_A; IMatrix3x3 * pB = &_B; IMatrix3x3 * pC = &C; //asm code asm volatile( //turn on a vector depth of 3 "fmrx r0, fpscr \n\t" "bic r0, r0, #0x00370000 \n\t" "orr r0, r0, #0x00020000 \n\t" "fmxr fpscr, r0 \n\t" //load matrix B into the vector bank "fldmias %1, {s8-s16} \n\t" //load the first row of A into the scalar bank "fldmias %0!, {s0-s2} \n\t" //calulate C.A0, C.A1 and C.A2 "fmuls s17, s8, s0 \n\t" "fmacs s17, s11, s1 \n\t" "fmacs s17, s14, s2 \n\t" //save this into the output "fstmias %2!, {s17-s19} \n\t" //load the second row of A into the scalar bank "fldmias %0!, {s0-s2} \n\t" //calulate C.B0, C.B1 and C.B2 "fmuls s17, s8, s0 \n\t" "fmacs s17, s11, s1 \n\t" "fmacs s17, s14, s2 \n\t" //save this into the output "fstmias %2!, {s17-s19} \n\t" //load the third row of A into the scalar bank "fldmias %0!, {s0-s2} \n\t" //calulate C.C0, C.C1 and C.C2 "fmuls s17, s8, s0 \n\t" "fmacs s17, s11, s1 \n\t" "fmacs s17, s14, s2 \n\t" //save this into the output "fstmias %2!, {s17-s19} \n\t" //set the vector depth back to 1 "fmrx r0, fpscr \n\t" "bic r0, r0, #0x00370000 \n\t" "orr r0, r0, #0x00000000 \n\t" "fmxr fpscr, r0 \n\t" //pass the inputs and set the clobber list : "+r"(pA), "+r"(pB), "+r" (pC) : :"cc", "memory","s0", "s1", "s2", "s8", "s9", "s10", "s11", "s12", "s13", "s14", "s15", "s16", "s17", "s18", "s19" ); #endif return C; } As far as i can see that makes sence. While debugging i've managed to notice that if i were to say _A = C prior to the return and after the ASM, _A will not necessarily be equal to C which has only increased my confusion. I had thought it was possibly due to the pointers I'm giving to the VFPU being incrimented by lines such as "fldmias %0!, {s0-s2} \n\t" however my understanding of asm is not good enough to properly understand the problem, nor to see an alternative approach to that line of code. Anyway, I was hoping someone with a greater understanding than me would be able to see a solution, and any help would be greatly appreciated, thank you :-)

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• How to find same-value rectangular areas of a given size in a matrix most efficiently?

  - by neo

  My problem is very simple but I haven't found an efficient implementation yet. Suppose there is a matrix A like this: 0 0 0 0 0 0 0 4 4 2 2 2 0 0 4 4 2 2 2 0 0 0 0 2 2 2 1 1 0 0 0 0 0 1 1 Now I want to find all starting positions of rectangular areas in this matrix which have a given size. An area is a subset of A where all numbers are the same. Let's say width=2 and height=3. There are 3 areas which have this size: 2 2 2 2 0 0 2 2 2 2 0 0 2 2 2 2 0 0 The result of the function call would be a list of starting positions (x,y starting with 0) of those areas. List((2,1),(3,1),(5,0)) The following is my current implementation. "Areas" are called "surfaces" here. case class Dimension2D(width: Int, height: Int) case class Position2D(x: Int, y: Int) def findFlatSurfaces(matrix: Array[Array[Int]], surfaceSize: Dimension2D): List[Position2D] = { val matrixWidth = matrix.length val matrixHeight = matrix(0).length var resultPositions: List[Position2D] = Nil for (y <- 0 to matrixHeight - surfaceSize.height) { var x = 0 while (x <= matrixWidth - surfaceSize.width) { val topLeft = matrix(x)(y) val topRight = matrix(x + surfaceSize.width - 1)(y) val bottomLeft = matrix(x)(y + surfaceSize.height - 1) val bottomRight = matrix(x + surfaceSize.width - 1)(y + surfaceSize.height - 1) // investigate further if corners are equal if (topLeft == bottomLeft && topLeft == topRight && topLeft == bottomRight) { breakable { for (sx <- x until x + surfaceSize.width; sy <- y until y + surfaceSize.height) { if (matrix(sx)(sy) != topLeft) { x = if (x == sx) sx + 1 else sx break } } // found one! resultPositions ::= Position2D(x, y) x += 1 } } else if (topRight != bottomRight) { // can skip x a bit as there won't be a valid match in current row in this area x += surfaceSize.width } else { x += 1 } } } return resultPositions } I already tried to include some optimizations in it but I am sure that there are far better solutions. Is there a matlab function existing for it which I could port? I'm also wondering whether this problem has its own name as I didn't exactly know what to google for. Thanks for thinking about it! I'm excited to see your proposals or solutions :)

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• glm matrix conversion for DirectX

  - by niktehpui

  For on of the coursework specification I need to work with DirectX, so I tried to implement a DirectX Renderer in my small cross-platform framework (to have it optionally available for Windows). Since I want to stick to my dependencies I want use glm for vector/matrix/quaternions math. The vectors seem to be fully compatible with DirectX, but the glm::mat4 is not working properly in DirectX Effects Framework. I assumed the reason is that DirectX uses row majors layouts and OpenGL column majors (although if I remember right internally in HLSL DX uses column major as well), so I transposed the matrix, but I still get no proper results compared to using XNA-Math. XNA-Version of the code (works): XMMATRIX world = XMMatrixIdentity(); XMMATRIX view = XMMatrixLookAtLH(XMVectorSet(5.0, 5.0, 5.0, 1.0f), XMVectorZero(), XMVectorSet(0.0f, 1.0f, 0.0f, 0.0f)); XMMATRIX proj = XMMatrixPerspectiveFovLH(0.25f*3.14f, 1.25f, 1.0f, 1000.0f); XMMATRIX worldViewProj = world*view*proj; m_fxWorldViewProj->SetMatrix(reinterpret_cast<float*>(&worldViewProj)); This works flawlessly and displays the expected colored cube. GLM-Version (does not work): glm::mat4 world(1.0f); glm::mat4 view = glm::lookAt(glm::vec3(5.0f, 5.0f, 5.0f), glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3(0.0f, 1.0f, 0.0f)); glm::mat4 proj = glm::perspective(0.25f*3.14f, 1.25f, 1.0f, 1000.0f); glm::mat4 worldViewProj = glm::transpose(world*view*proj); m_fxWorldViewProj->SetMatrix(glm::value_ptr(worldViewProj)); Displays nothing, screen stays black. I really would like to stick to glm on all platforms.

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• HTML to 'pretty' text conversion for printing on text only printer (dot matrix)

  - by Gala101

  Hi, I have a web-site that generates some simple tabular data as html tables, many of my users print the web-page on a laser/inkjet printer; however some like to print on legacy Dot Matrix printers (text only) and there-in lies the problem. When giving Print from web-browser onto dot-matrix printer, the printer actually perceives data as 'graphic'/image and proceeds to print it dot-by-dot. i.e If printing a character 'C', printer slices it horizontally and prints in 3-4 passes. Same printer prints a text from an ASCII file (say from notepad) as complete characters in single pass, thereby being 5 times faster and much quieter than when printing a web-page. (Even tried 'generic text-only driver' but Mozilla Firefox has a know bug that it does not print anything over this particular driver since 2.0+) So is there some clean way of formatting an already generated HTML (say method takes the entire html table as string) and generates a corresponding text file with properly aligned columns? I have tried stripping the html tags, but the major issue there is performing good 'wrapping' of a cell's data and maintaining integrity of other cells' data (from same row). eg: ( '|' and '_' not really required) Col1 | Col2 | Colum_Name3 | Col4 | _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 | this cell | this column | smaller | | is in three| spans 2 rows | | | rows | | | - - - - - - - - - - - - - - - - - - - - - - - - 2 | smaller now| this also | but this| | | | cell's | | | | data is | | | | now | | | | bigger | _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Could you please suggest preferred approach? I've thought of using xslt and somehow outputting text (instead of more prevalent pdf), but Apache FOP's text renderer is really broken and perhaps forgotten in development path. Commercial one's are way too costly.

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• Custom Calculations in a Matrix - Reporting Services 2005

  - by bfrancis

  I am writing a report to show gas usage (in gallons) used by each department. The request is to view each month and the gallons used by each department. A column is required to display what each departments target goal is, based on the gallons of gas they have used in a past time frame. Each departments target goal is x percent less than the total gallons used for said time frame. I currently have a matrix in Reporting Services with departments making up rows, months making up columns, and gallons filling the details. The matrix is being filled by dataset1. I have the data grouping as is requested for each month by each department. My problem is calculating the target goal. My thought was to create a second dataset (dataset2) that returns the gallons used based on the time frame requested. I grouped this data by department. I was hoping I could use the department field in each dataset to make sure the appropriate numbers were used. I added a new column which shows up next to the gallons field. As I attempted to build the Expression I found out that I could only grab the gallons used from dataset2 if I was summing the gallons field. This gives me the total gallons used by every department combined. I have tried to find resources with similar examples of what I am trying to accomplish but I cannot seem to come across one. I am trying to keep this as detailed as possible without making it too wordy. I would be more than happy to clarify or explain into further detail what I have written above if it is needed. If anyone has links, comments, or suggestions they would be greatly appreciated. A very simple visual or what I am hoping to accomplish is below. The months and departments would expand based on the data returned. months ------------------------------ departments| gallons/month | target goal

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• how to implement a sparse_vector class

  - by Neil G

  I am implementing a templated sparse_vector class. It's like a vector, but it only stores elements that are different from their default constructed value. So, sparse_vector would store the index-value pairs for all indices whose value is not T(). I am basing my implementation on existing sparse vectors in numeric libraries-- though mine will handle non-numeric types T as well. I looked at boost::numeric::ublas::coordinate_vector and eigen::SparseVector. Both store: size_t* indices_; // a dynamic array T* values_; // a dynamic array int size_; int capacity_; Why don't they simply use vector<pair<size_t, T>> data_; My main question is what are the pros and cons of both systems, and which is ultimately better? The vector of pairs manages size_ and capacity_ for you, and simplifies the accompanying iterator classes; it also has one memory block instead of two, so it incurs half the reallocations, and might have better locality of reference. The other solution might search more quickly since the cache lines fill up with only index data during a search. There might also be some alignment advantages if T is an 8-byte type? It seems to me that vector of pairs is the better solution, yet both containers chose the other solution. Why?

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• Matlab matrix translation and rotation multiple times

  - by pinnacler

  I have a map of individual trees from a forest stored as x,y points in a matrix. I call it fixedPositions. It's cartesian and (0,0) is the origin. I would like 0/360 degrees to be the top of the screen and 90 degrees to be to the right. Given a velocity and a heading, i.e. .5 m/s and 60 degrees (2 o'clock equivalent on a watch), how do I rotate that x,y points, so that the new origin is centered at (.5cos(60),.5sin(60)) and 60 degrees is now at the top of the screen? Then if I were to give you another heading and speed, i.e. 0 degrees and 2m/s, it should calculate it from the last point, not the original fixedPositions origin. I've wasted my day trying to figure this out. I wish I took matrix algebra but I'm at a loss. I tried doing cos(30) and even those wouldn't compute correctly, which after an hour I realize were in radians.

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• Better way to compare neighboring cells in matrix

  - by HyperCube

  Suppose I have a matrix of size 100x100 and I would like to compare each pixel to its direct neighbor (left, upper, right, lower) and then do some operations on the current matrix or a new one of the same size. A sample code in Python/Numpy could look like the following: (the comparison 0.5 has no meaning, I just want to give a working example for some operation while comparing the neighbors) import numpy as np my_matrix = np.random.rand(100,100) new_matrix = np.array((100,100)) my_range = np.arange(1,99) for i in my_range: for j in my_range: if my_matrix[i,j+1] > 0.5: new_matrix[i,j+1] = 1 if my_matrix[i,j-1] > 0.5: new_matrix[i,j-1] = 1 if my_matrix[i+1,j] > 0.5: new_matrix[i+1,j] = 1 if my_matrix[i-1,j] > 0.5: new_matrix[i-1,j] = 1 if my_matrix[i+1,j+1] > 0.5: new_matrix[i+1,j+1] = 1 if my_matrix[i+1,j-1] > 0.5: new_matrix[i+1,j-1] = 1 if my_matrix[i-1,j+1] > 0.5: new_matrix[i-1,j+1] = 1 This can get really nasty if I want to step into one neighboring cell and start from it to do a similar task... Do you have some suggestions how this can be done in a more efficient manner? Is this even possible?

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• How to solve linker error in matrix multiplication in c using lapack library?

  - by Malar

  I did Matrix multiplication using lapack library, I am getting an error like below. Can any one help me? "error LNK2019: unresolved external symbol "void __cdecl dgemm(char,char,int *,int *,int *,double *,double *,int *,double *,int *,double *,double *,int *)" (?dgemm@@YAXDDPAH00PAN1010110@Z) referenced in function _main" 1..\bin\matrixMultiplicationUsingLapack.exe : fatal error LNK1120: 1 unresolved externals I post my code below # define matARowSize 2 // -- Matrix 1 number of rows # define matAColSize 2 // -- Matrix 1 number of cols # define matBRowSize 2 // -- Matrix 2 number of rows # define matBColSize 2 // -- Matrix 2 number of cols using namespace std; void dgemm(char, char, int *, int *, int *, double *, double *, int *, double *, int *, double *, double *, int *); int main() { double iMatrixA[matARowSize*matAColSize]; // -- Input matrix 1 {m x n} double iMatrixB[matBRowSize*matBColSize]; // -- Input matrix 2 {n x k} double iMatrixC[matARowSize*matBColSize]; // -- Output matrix {m x n * n x k = m x k} double alpha = 1.0f; double beta = 0.0f; int n = 2; iMatrixA[0] = 1; iMatrixA[1] = 1; iMatrixA[2] = 1; iMatrixA[3] = 1; iMatrixB[0] = 1; iMatrixB[1] = 1; iMatrixB[2] = 1; iMatrixB[3] = 1; //dgemm('N','N',&n,&n,&n,&alpha,iMatrixA,&n,iMatrixB,&n,&beta,iMatrixC,&n); dgemm('N','N',&n,&n,&n,&alpha,iMatrixA,&n,iMatrixB,&n,&beta,iMatrixC,&n); std::cin.get(); return 0; }

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• What does it mean to "preconcat" a matrix?

  - by Brad Hein

  In reviewing: http://developer.android.com/reference/android/graphics/Canvas.html I'm wondering translate(): "preconcat the current matrix with the specified translation" -- what does this mean? I can't find a good definition of "preconcat" anywhere on the internet! The only place I can find it is in the Android Source - I'm starting to wonder if they made it up? :) I'm familiar with "concat" or concatenate, which is to append to, so what is a pre-concat?

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• Numpy ‘smart’ symmetric matrix

  - by Debilski

  Is there a smart and space-efficient symmetric matrix in numpy which automatically fills [j][i] when [i][j] is written to? a = numpy.symmetric((3, 3)) a[0][1] = 1 print a # [[0 1 0], [1 0 0], [0 0 0]] An automatic Hermitian would also be nice, although I won’t need that at the time of writing.

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• Diagonalization of bidiagonal matrix with QR

  - by Simon

  How can i diagonalize the matrix A having the orthogonal transformations P and Q: A = Q*B*P ? I saw something pointing out to QR transformations, but i couldn't find out the algorithm.

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• A python random function acts differently when assigned to a list or called directly...

  - by Dror Hilman

  I have a python function that randomize a dictionary representing a position specific scoring matrix. for example: mat = { 'A' : [ 0.53, 0.66, 0.67, 0.05, 0.01, 0.86, 0.03, 0.97, 0.33, 0.41, 0.26 ] 'C' : [ 0.14, 0.04, 0.13, 0.92, 0.99, 0.04, 0.94, 0.00, 0.07, 0.23, 0.35 ] 'T' : [ 0.25, 0.07, 0.01, 0.01, 0.00, 0.04, 0.00, 0.03, 0.06, 0.12, 0.14 ] 'G' : [ 0.08, 0.23, 0.20, 0.02, 0.00, 0.06, 0.04, 0.00, 0.54, 0.24, 0.25 ] } The scambling function: def scramble_matrix(matrix, iterations): mat_len = len(matrix["A"]) pos1 = pos2 = 0 for count in range(iterations): pos1,pos2 = random.sample(range(mat_len), 2) #suffle the matrix: for nuc in matrix.keys(): matrix[nuc][pos1],matrix[nuc][pos2] = matrix[nuc][pos2],matrix[nuc][pos1] return matrix def print_matrix(matrix): for nuc in matrix.keys(): print nuc+"[", for count in matrix[nuc]: print "%.2f"%count, print "]" now to the problem... When I try to scramble a matrix directly, It's works fine: print_matrix(mat) print "" print_matrix(scramble_matrix(mat,10)) gives: A[ 0.53 0.66 0.67 0.05 0.01 0.86 0.03 0.97 0.33 0.41 0.26 ] C[ 0.14 0.04 0.13 0.92 0.99 0.04 0.94 0.00 0.07 0.23 0.35 ] T[ 0.25 0.07 0.01 0.01 0.00 0.04 0.00 0.03 0.06 0.12 0.14 ] G[ 0.08 0.23 0.20 0.02 0.00 0.06 0.04 0.00 0.54 0.24 0.25 ] A[ 0.41 0.97 0.03 0.86 0.53 0.66 0.33.05 0.67 0.26 0.01 ] C[ 0.23 0.00 0.94 0.04 0.14 0.04 0.07 0.92 0.13 0.35 0.99 ] T[ 0.12 0.03 0.00 0.04 0.25 0.07 0.06 0.01 0.01 0.14 0.00 ] G[ 0.24 0.00 0.04 0.06 0.08 0.23 0.54 0.02 0.20 0.25 0.00 ] but when I try to assign this scrambling to a list , it does not work!!! ... print_matrix(mat) s=[] for x in range(3): s.append(scramble_matrix(mat,10)) for matrix in s: print "" print_matrix(matrix) result: A[ 0.53 0.66 0.67 0.05 0.01 0.86 0.03 0.97 0.33 0.41 0.26 ] C[ 0.14 0.04 0.13 0.92 0.99 0.04 0.94 0.00 0.07 0.23 0.35 ] T[ 0.25 0.07 0.01 0.01 0.00 0.04 0.00 0.03 0.06 0.12 0.14 ] G[ 0.08 0.23 0.20 0.02 0.00 0.06 0.04 0.00 0.54 0.24 0.25 ] A[ 0.01 0.66 0.97 0.67 0.03 0.05 0.33 0.53 0.26 0.41 0.86 ] C[ 0.99 0.04 0.00 0.13 0.94 0.92 0.07 0.14 0.35 0.23 0.04 ] T[ 0.00 0.07 0.03 0.01 0.00 0.01 0.06 0.25 0.14 0.12 0.04 ] G[ 0.00 0.23 0.00 0.20 0.04 0.02 0.54 0.08 0.25 0.24 0.06 ] A[ 0.01 0.66 0.97 0.67 0.03 0.05 0.33 0.53 0.26 0.41 0.86 ] C[ 0.99 0.04 0.00 0.13 0.94 0.92 0.07 0.14 0.35 0.23 0.04 ] T[ 0.00 0.07 0.03 0.01 0.00 0.01 0.06 0.25 0.14 0.12 0.04 ] G[ 0.00 0.23 0.00 0.20 0.04 0.02 0.54 0.08 0.25 0.24 0.06 ] A[ 0.01 0.66 0.97 0.67 0.03 0.05 0.33 0.53 0.26 0.41 0.86 ] C[ 0.99 0.04 0.00 0.13 0.94 0.92 0.07 0.14 0.35 0.23 0.04 ] T[ 0.00 0.07 0.03 0.01 0.00 0.01 0.06 0.25 0.14 0.12 0.04 ] G[ 0.00 0.23 0.00 0.20 0.04 0.02 0.54 0.08 0.25 0.24 0.06 ] What is the problem??? Why the scrambling do not work after the first time, and all the list filled with the same matrix?!

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• Error at lapack cgesv when matrix is not singular

  - by Jan Malec

  This is my first post. I usually ask classmates for help, but they have a lot of work now and I'm too desperate to figure this out on my own :). I am working on a project for school and I have come to a point where I need to solve a system of linear equations with complex numbers. I have decided to call lapack routine "cgesv" from c++. I use the c++ complex library to work with complex numbers. Problem is, when I call the routine, I get error code "2". From lapack documentation: INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, U(i,i) is exactly zero. The factorization has been completed, but the factor U is exactly singular, so the solution could not be computed. Therefore, the element U(2, 2) should be zero, but it is not. This is how I declare the function: void cgesv_( int* N, int* NRHS, std::complex* A, int* lda, int* ipiv, std::complex* B, int* ldb, int* INFO ); This is how I use it: int *IPIV = new int[NA]; int INFO, NRHS = 1; std::complex<double> *aMatrix = new std::complex<double>[NA*NA]; for(int i=0; i<NA; i++){ for(int j=0; j<NA; j++){ aMatrix[j*NA+i] = A[i][j]; } } cgesv_( &NA, &NRHS, aMatrix, &NA, IPIV, B, &NB, &INFO ); And this is how the matrix looks like: (1,-160.85) (0,0.000306796) (0,-0) (0,-0) (0,-0) (0,0.000306796) (1,-40.213) (0,0.000306796) (0,-0) (0,-0) (0,-0) (0,0.000306796) (1,-0.000613592) (0,0.000306796) (0,-0) (0,-0) (0,-0) (0,0.000306796) (1,-40.213) (0,0.000306796) (0,-0) (0,-0) (0,-0) (0,0.000306796) (1,-160.85) I had to split the matrix colums, otherwise it did not format correctly. My first suspicion was that complex is not parsed correctly, but I have used lapack functions with complex numbers before this way. Any ideas?

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• Create a binary indicator matrix in R

  - by Brian Vanover

  I have a list of data indicating attendance to conferences like this: Event Participant ConferenceA John ConferenceA Joe ConferenceA Mary ConferenceB John ConferenceB Ted ConferenceC Jessica I would like to create a binary indicator attendance matrix of the following format: Event John Joe Mary Ted Jessica ConferenceA 1 1 1 0 0 ConferenceB 1 0 0 1 0 ConferenceC 0 0 0 0 1 Is there a way to do this in R? Sorry for the poor formatting.

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• Matrix of the diagonal sobel operator of size 3x3

  - by erjik

  What is the matrix of sobel operator of size 3x3 if the operator is said to be diagonal (Left or right diagonal)? EDIT: or may be with more bigger size

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• How to remove commas etc form a matrix in python

  - by robert

  say ive got a matrix that looks like: [[0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]] how can i make it on seperate lines: [[0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]] and then remove commas etc: 0 0 0 0 0 And also to make it blank instead of 0's, so that numbers can be put in later, so in the end it will be like: _ 1 2 _ 1 _ 1 (spaces not underscores) thanks

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• Matrix in python

  - by Werner

  Hi, I am very new to Python, I need to read numbers from a file and store them in a matrix like I would do it in fortran or C; for i for j data[i][j][0]=read(0) data[i][j][1]=read(1) data[i][j][2]=read(2) ... ... How can I do the same in Python? I read a bit but got confused with tuples and similar things If you could point me to a similar example it would be great thanks

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• What is a Matrix Table ?

  - by I Pravin Kumar

  Can somebody give me a picture as to what Matrix Tables are in the area of Database and the context in which they are best used ? Thanks,

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• Differences between matrix implementation in C

  - by tempy

  I created two 2D arrays (matrix) in C in two different ways. I don't understand the difference between the way they're represented in the memory, and the reason why I can't refer to them in the same way: scanf("%d", &intMatrix1[i][j]); //can't refer as &intMatrix1[(i * lines)+j]) scanf("%d", &intMatrix2[(i * lines)+j]); //can't refer as &intMatrix2[i][j]) What is the difference between the ways these two arrays are implemented and why do I have to refer to them differently? How do I refer to an element in each of the arrays in the same way (?????? in my printMatrix function)? int main() { int **intMatrix1; int *intMatrix2; int i, j, lines, columns; lines = 3; columns = 2; /************************* intMatrix1 ****************************/ intMatrix1 = (int **)malloc(lines * sizeof(int *)); for (i = 0; i < lines; ++i) intMatrix1[i] = (int *)malloc(columns * sizeof(int)); for (i = 0; i < lines; ++i) { for (j = 0; j < columns; ++j) { printf("Type a number for intMatrix1[%d][%d]\t", i, j); scanf("%d", &intMatrix1[i][j]); } } /************************* intMatrix2 ****************************/ intMatrix2 = (int *)malloc(lines * columns * sizeof(int)); for (i = 0; i < lines; ++i) { for (j = 0; j < columns; ++j) { printf("Type a number for intMatrix2[%d][%d]\t", i, j); scanf("%d", &intMatrix2[(i * lines)+j]); } } /************** printing intMatrix1 & intMatrix2 ****************/ printf("intMatrix1:\n\n"); printMatrix(*intMatrix1, lines, columns); printf("intMatrix2:\n\n"); printMatrix(intMatrix2, lines, columns); } /************************* printMatrix ****************************/ void printMatrix(int *ptArray, int h, int w) { int i, j; printf("Printing matrix...\n\n\n"); for (i = 0; i < h; ++i) for (j = 0; j < w; ++j) printf("array[%d][%d] ==============> %d\n, i, j, ??????); }

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