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  • Graph representation benchmarking

    - by Carlucho
    Currently am developing a program that solves (if possible) any given labyrinth of dimensions from 3X4 to 26x30. I represent the graph using both adj matrix (sparse) and adj list. I would like to know how to output the total time taken by the DFS to find the solution using one and then the other method. Programatically, how could i produce such benchmark?

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  • Matrices of "long"s in Java/COLT?

    - by Darren Wilkinson
    I'm very new to Java/COLT so apologies if this is a dumb question... But, is it possible to define (2d) matrices of type "long" using the cern.colt.matrix stuff? If so, how?! I can find an abstract class for "Object" and a concrete implementation for "double", but then I am stuck... Thanks,

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  • Any ideas on How to search a 2D array quickly?

    - by Tattat
    I jave a 2D array like this, just like a matrix: {{1, 2, 4, 5, 3, 6}, {8, 3, 4, 4, 5, 2}, {8, 3, 4, 2, 6, 2}, //code skips... ... } I want to get all the "4" position, instead of searching the array one by way, and return the position, how can I search it faster / more efficient? thz in advance.

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  • java double[][] - display as image

    - by joe_shmoe
    Hi all, just wondering if there is a simple way in java to display the contents of say 16x16 array of doubles [0..1] as a greyscale image (ala matlab)? using an unfamiliar matrix library, so I'd like to check that I'm on the right track. don't really care if it is slow or ugly, or if it requires external library - it's just there for a quick look, so as long as it works, I'm fine.

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  • Graph representation

    - by Carlucho
    Given graph, how could i represent it using adj matrix?. I have read lots of tutorials, post, slides, etc but i cant get my head round it, i just need that little push.

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  • How do you rotate a two dimensional array?

    - by swilliams
    Inspired by Raymond Chen's post, say you have a 4x4 two dimensional array, write a function that rotates it 90 degrees. Raymond links to a solution in pseudo code, but I'd like to see some real world stuff. [1][2][3][4] [5][6][7][8] [9][0][1][2] [3][4][5][6] Becomes: [3][9][5][1] [4][0][6][2] [5][1][7][3] [6][2][8][4] Update: Nick's answer is the most straightforward, but is there a way to do it better than n^2? What if the matrix was 10000x10000?

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  • Efficiently solving sparse matrices

    - by anon
    For solving spare matrices, in general, how big does the matrix have to be (as a rule of thumb) for methods like congraduate descent to be faster than brute force solvers (that do not take advantage o sparsity)?

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  • XNA model drawing problem

    - by user1990950
    When using this code: public static void DrawModel(Model model, Vector3 position, Vector3 offset, float xRotation, float yRotation, float zRotation, float allrot, float xScale, float yScale, float zScale) { position.Y *= -1; offset.Y *= -1; Matrix worldMatrix = ((Matrix.CreateRotationZ(MathHelper.ToRadians(zRotation)) * Matrix.CreateRotationX(MathHelper.ToRadians(xRotation))) * Matrix.CreateRotationY(MathHelper.ToRadians(yRotation))) * (Matrix.CreateTranslation(offset) * Matrix.CreateRotationY(MathHelper.ToRadians(allrot))) * Matrix.CreateScale(xScale, yScale, zScale); worldMatrix *= Matrix.CreateTranslation(position) * theCamera.GetTransformation() * Matrix.CreateTranslation(new Vector3(-(graphics.GraphicsDevice.Viewport.Width / 2), graphics.GraphicsDevice.Viewport.Height / 2, 0)); foreach (ModelMesh mesh in model.Meshes) { for (int i = 0; i < mesh.Effects.Count; i++) { ((BasicEffect)mesh.Effects[i]).EnableDefaultLighting(); ((BasicEffect)mesh.Effects[i]).World = worldMatrix; ((BasicEffect)mesh.Effects[i]).View = viewMatrix; ((BasicEffect)mesh.Effects[i]).Projection = projectionMatrix; } mesh.Draw(); } } The model rotates and then scales. It should scale and then rotate, but whenever I try to change it, it won't work.

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  • How do I go about overloading C++ operators to allow for chaining?

    - by fneep
    I, like so many programmers before me, am tearing my hair out writing the right-of-passage-matrix-class-in-C++. I have never done very serious operator overloading and this is causing issues. Essentially, by stepping through This is what I call to cause the problems. cMatrix Kev = CT::cMatrix::GetUnitMatrix(4, true); Kev *= 4.0f; cMatrix Baz = Kev; Kev = Kev+Baz; //HERE! What seems to be happening according to the debugger is that Kev and Baz are added but then the value is lost and when it comes to reassigning to Kev, the memory is just its default dodgy values. How do I overload my operators to allow for this statement? My (stripped down) code is below. //header class cMatrix { private: float* _internal; UInt32 _r; UInt32 _c; bool _zeroindexed; //fast, assumes zero index, no safety checks float cMatrix::_getelement(UInt32 r, UInt32 c) { return _internal[(r*this->_c)+c]; } void cMatrix::_setelement(UInt32 r, UInt32 c, float Value) { _internal[(r*this->_c)+c] = Value; } public: cMatrix(UInt32 r, UInt32 c, bool IsZeroIndexed); cMatrix( cMatrix& m); ~cMatrix(void); //operators cMatrix& operator + (cMatrix m); cMatrix& operator += (cMatrix m); cMatrix& operator = (const cMatrix &m); }; //stripped source file cMatrix::cMatrix(cMatrix& m) { _r = m._r; _c = m._c; _zeroindexed = m._zeroindexed; _internal = new float[_r*_c]; UInt32 size = GetElementCount(); for (UInt32 i = 0; i < size; i++) { _internal[i] = m._internal[i]; } } cMatrix::~cMatrix(void) { delete[] _internal; } cMatrix& cMatrix::operator+(cMatrix m) { return cMatrix(*this) += m; } cMatrix& cMatrix::operator*(float f) { return cMatrix(*this) *= f; } cMatrix& cMatrix::operator*=(float f) { UInt32 size = GetElementCount(); for (UInt32 i = 0; i < size; i++) { _internal[i] *= f; } return *this; } cMatrix& cMatrix::operator+=(cMatrix m) { if (_c != m._c || _r != m._r) { throw new cCTException("Cannot add two matrix classes of different sizes."); } if (!(_zeroindexed && m._zeroindexed)) { throw new cCTException("Zero-Indexed mismatch."); } for (UInt32 row = 0; row < _r; row++) { for (UInt32 column = 0; column < _c; column++) { float Current = _getelement(row, column) + m._getelement(row, column); _setelement(row, column, Current); } } return *this; } cMatrix& cMatrix::operator=(const cMatrix &m) { if (this != &m) { _r = m._r; _c = m._c; _zeroindexed = m._zeroindexed; delete[] _internal; _internal = new float[_r*_c]; UInt32 size = GetElementCount(); for (UInt32 i = 0; i < size; i++) { _internal[i] = m._internal[i]; } } return *this; }

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  • Converting a WPFToolkit DataGrid from 1D list to 2D matrix

    - by user61073
    Hello - I am wondering if anyone has attempted the following or has an idea as to how to do it. I have a WPFToolkit DataGrid which is bound to an ObservableCollection of items. As such, the DataGrid is shown with as many rows in the ObservableCollection, and as many columns as I have defined in for the DataGrid. That all is good. What I now need is to provide another view of the same data, only, instead, the DataGrid is shown with as many cells in the ObservableCollection. So let's say, my ObservableCollection has 100 items in it. The original scenario showed the DataGrid with 100 rows and 1 column. In the modified scenario, I need to show it with 10 rows and 10 columns, where each cell shows the value that was in the original representation. In other words, I need to transform my 1D ObservableCollection to a 2D ObservableCollection and display it in the DataGrid. I know how to do that programmatically in the code behind, but can it be done in XAML? Let me simplify the problem a little, in case anybody can have a crack at this. The XAML below does the following: * Defines an XmlDataProvider just for dummy data * Creates a DataGrid with 10 columns o each column is a DataGridTemplateColumn using the same CellTemplate * The CellTemplate is a simple TextBlock bound to an XML element If you run the XAML below, you will find that the DataGrid ends up with 5 rows, one for each book, and 10 columns that have identical content (all showing the book titles). However, what I am trying to accomplish, albeit with a different data set, is that in this case, I would end up with one row, with each book title appearing in a single cell in row 1, occupying cells 0-4, and nothing in cells 5-9. Then, if I added more data and had 12 books in my XML data source, I would get row 1 completely filled (cells covering the first 10 titles) and row 2 would get the first 2 cells filled. Can my scenario be accomplished primarily in XAML, or should I resign myself to working in the code behind? Any guidance would greatly be appreciated. Thanks so much! <UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:custom="http://schemas.microsoft.com/wpf/2008/toolkit" mc:Ignorable="d" x:Name="UserControl" d:DesignWidth="600" d:DesignHeight="400" > <UserControl.Resources> <XmlDataProvider x:Key="InventoryData" XPath="Inventory/Books"> <x:XData> <Inventory xmlns=""> <Books> <Book ISBN="0-7356-0562-9" Stock="in" Number="9"> <Title>XML in Action</Title> <Summary>XML Web Technology</Summary> </Book> <Book ISBN="0-7356-1370-2" Stock="in" Number="8"> <Title>Programming Microsoft Windows With C#</Title> <Summary>C# Programming using the .NET Framework</Summary> </Book> <Book ISBN="0-7356-1288-9" Stock="out" Number="7"> <Title>Inside C#</Title> <Summary>C# Language Programming</Summary> </Book> <Book ISBN="0-7356-1377-X" Stock="in" Number="5"> <Title>Introducing Microsoft .NET</Title> <Summary>Overview of .NET Technology</Summary> </Book> <Book ISBN="0-7356-1448-2" Stock="out" Number="4"> <Title>Microsoft C# Language Specifications</Title> <Summary>The C# language definition</Summary> </Book> </Books> <CDs> <CD Stock="in" Number="3"> <Title>Classical Collection</Title> <Summary>Classical Music</Summary> </CD> <CD Stock="out" Number="9"> <Title>Jazz Collection</Title> <Summary>Jazz Music</Summary> </CD> </CDs> </Inventory> </x:XData> </XmlDataProvider> <DataTemplate x:Key="GridCellTemplate"> <TextBlock> <TextBlock.Text> <Binding XPath="Title"/> </TextBlock.Text> </TextBlock> </DataTemplate> </UserControl.Resources> <Grid x:Name="LayoutRoot"> <custom:DataGrid HorizontalAlignment="Stretch" VerticalAlignment="Stretch" IsSynchronizedWithCurrentItem="True" Background="{DynamicResource WindowBackgroundBrush}" HeadersVisibility="All" RowDetailsVisibilityMode="Collapsed" SelectionUnit="CellOrRowHeader" CanUserResizeRows="False" GridLinesVisibility="None" RowHeaderWidth="35" AutoGenerateColumns="False" CanUserReorderColumns="False" CanUserSortColumns="False"> <custom:DataGrid.Columns> <custom:DataGridTemplateColumn CellTemplate="{StaticResource GridCellTemplate}" Header="01" /> <custom:DataGridTemplateColumn CellTemplate="{StaticResource GridCellTemplate}" Header="02" /> <custom:DataGridTemplateColumn CellTemplate="{StaticResource GridCellTemplate}" Header="03" /> <custom:DataGridTemplateColumn CellTemplate="{StaticResource GridCellTemplate}" Header="04" /> <custom:DataGridTemplateColumn CellTemplate="{StaticResource GridCellTemplate}" Header="05" /> <custom:DataGridTemplateColumn CellTemplate="{StaticResource GridCellTemplate}" Header="06" /> <custom:DataGridTemplateColumn CellTemplate="{StaticResource GridCellTemplate}" Header="07" /> <custom:DataGridTemplateColumn CellTemplate="{StaticResource GridCellTemplate}" Header="08" /> <custom:DataGridTemplateColumn CellTemplate="{StaticResource GridCellTemplate}" Header="09" /> <custom:DataGridTemplateColumn CellTemplate="{StaticResource GridCellTemplate}" Header="10" /> </custom:DataGrid.Columns> <custom:DataGrid.ItemsSource> <Binding Source="{StaticResource InventoryData}" XPath="Book"/> </custom:DataGrid.ItemsSource> </custom:DataGrid> </Grid>

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  • MATLAB using MAT2CELL

    - by Ali
    i have the following matrices letter=[A B C D E F G H I J K L M N O P Q R S T U V W X Y Z ... a b c d e f g h ii jj k l m o p q r s t u v w x y z]; number=[one two three four five six seven eight nine zero]; character =[number letter]; Character becomes a matrix of 42 by 1464, but i would like to break it into cells of 42 by 24 using mat2cell. How can i please do it, every time i try i get an error????

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  • Representing Sparse Data in PostgreSQL

    - by Chris S
    What's the best way to represent a sparse data matrix in PostgreSQL? The two obvious methods I see are: Store data in a single a table with a separate column for every conceivable feature (potentially millions), but with a default value of NULL for unused features. This is conceptually very simple, but I know that with most RDMS implementations, that this is typically very inefficient, since the NULL values ususually takes up some space. However, I read an article (can't find its link unfortunately) that claimed PG doesn't take up data for NULL values, making it better suited for storing sparse data. Create separate "row" and "column" tables, as well as an intermediate table to link them and store the value for the column at that row. I believe this is the more traditional RDMS solution, but there's more complexity and overhead associated with it. I also found PostgreDynamic, which claims to better support sparse data, but I don't want to switch my entire database server to a PG fork just for this feature. Are there any other solutions? Which one should I use?

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  • How to get predecessor and successors from an adjacency matrix

    - by NickTFried
    Hi I am am trying to complete an assignment, where it is ok to consult the online community. I have to create a graph class that ultimately can do Breadth First Search and Depth First Search. I have been able to implement those algorithms successfully however another requirement is to be able to get the successors and predecessors and detect if two vertices are either predecessors or successors for each other. I'm having trouble thinking of a way to do this. I will post my code below, if anyone has any suggestions it would be greatly appreciated. import java.util.ArrayList; import java.util.Iterator; import java.util.LinkedList; import java.util.Queue; import java.util.Stack; public class Graph<T> { public Vertex<T> root; public ArrayList<Vertex<T>> vertices=new ArrayList<Vertex<T>>(); public int[][] adjMatrix; int size; private ArrayList<Vertex<T>> dfsArrList; private ArrayList<Vertex<T>> bfsArrList; public void setRootVertex(Vertex<T> n) { this.root=n; } public Vertex<T> getRootVertex() { return this.root; } public void addVertex(Vertex<T> n) { vertices.add(n); } public void removeVertex(int loc){ vertices.remove(loc); } public void addEdge(Vertex<T> start,Vertex<T> end) { if(adjMatrix==null) { size=vertices.size(); adjMatrix=new int[size][size]; } int startIndex=vertices.indexOf(start); int endIndex=vertices.indexOf(end); adjMatrix[startIndex][endIndex]=1; adjMatrix[endIndex][startIndex]=1; } public void removeEdge(Vertex<T> v1, Vertex<T> v2){ int startIndex=vertices.indexOf(v1); int endIndex=vertices.indexOf(v2); adjMatrix[startIndex][endIndex]=1; adjMatrix[endIndex][startIndex]=1; } public int countVertices(){ int ver = vertices.size(); return ver; } /* public boolean isPredecessor( Vertex<T> a, Vertex<T> b){ for() return true; }*/ /* public boolean isSuccessor( Vertex<T> a, Vertex<T> b){ for() return true; }*/ public void getSuccessors(Vertex<T> v1){ } public void getPredessors(Vertex<T> v1){ } private Vertex<T> getUnvisitedChildNode(Vertex<T> n) { int index=vertices.indexOf(n); int j=0; while(j<size) { if(adjMatrix[index][j]==1 && vertices.get(j).visited==false) { return vertices.get(j); } j++; } return null; } public Iterator<Vertex<T>> bfs() { Queue<Vertex<T>> q=new LinkedList<Vertex<T>>(); q.add(this.root); printVertex(this.root); root.visited=true; while(!q.isEmpty()) { Vertex<T> n=q.remove(); Vertex<T> child=null; while((child=getUnvisitedChildNode(n))!=null) { child.visited=true; bfsArrList.add(child); q.add(child); } } clearVertices(); return bfsArrList.iterator(); } public Iterator<Vertex<T>> dfs() { Stack<Vertex<T>> s=new Stack<Vertex<T>>(); s.push(this.root); root.visited=true; printVertex(root); while(!s.isEmpty()) { Vertex<T> n=s.peek(); Vertex<T> child=getUnvisitedChildNode(n); if(child!=null) { child.visited=true; dfsArrList.add(child); s.push(child); } else { s.pop(); } } clearVertices(); return dfsArrList.iterator(); } private void clearVertices() { int i=0; while(i<size) { Vertex<T> n=vertices.get(i); n.visited=false; i++; } } private void printVertex(Vertex<T> n) { System.out.print(n.label+" "); } }

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  • Is Matlab faster than Python?

    - by kame
    I want to compute magnetic fields of some conductors using the biot-savart-law and I want to use a 1000x1000x1000 matrix. Before I use Matlab, but now I want to use Python. Is Python slower than Matlab? How can I make Python faster? EDIT: Maybe the best way is to compute the big array with c/c++ and then transfering them to python. I want to visualise then with VPython. EDIT2: Could somebody give an advice for which is better in my case: C or C++?

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  • More complex view matrix calculation required to composite 3d models with 2d video

    - by lzcd
    I'm utilising some 2d / 3d tracking data (provided by pfHoe) to help integrate some 3d models into the playback of some 2d video. Things are working.... okay... but there's still some visible 'slipping' of the models against the video background and I suspect this is may be because the XNA CreatePerspective helper method isn't taking into account some of the additional data supplied by pfHoe such as independent horizontal / vertical field of view angles and focal length. Would anyone be able to point me towards some examples of constructing view matrices that include such details?

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  • MATLAB (MATrix LABoratory) interview questions?

    - by Shane
    I programmed in Matlab for many years, but switched to using R exclusively in the past few years so I'm a little out of practice. I'm interviewing a candidate today who describes himself as a Matlab expert. What MATLAB interview questions that I should be asking?

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  • What's the proper term for a function inverse to a constructor? Deconstructor, destructor, or something else?

    - by Petr Pudlák
    Edit: I'm rephrasing the question a bit. Apparently I caused some confusion because I didn't realize that the term destructor is used in OOP for something quite different - it's a function invoked when an object is being destroyed. In functional programming we (try to) avoid mutable state so there is no such equivalent to it. (I added the proper tag to the question.) Instead, I've seen that the record field for unwrapping a value (especially for single-valued data types such as newtypes) is sometimes called destructor or perhaps deconstructor. For example, let's have (in Haskell): newtype Wrap = Wrap { unwrap :: Int } Here Wrap is the constructor and unwrap is what? I've seen both, for example: ... Most often, one supplies smart constructors and destructors for these to ease working with them. ... at Haskell wiki, or ... The general theme here is to fuse constructor - deconstructor pairs like ... at Haskell wikibook (here it's probably meant in a bit more general sense). The questions are: How do we call unwrap in functional programming? Deconstructor? Destructor? Or by some other term? And to clarify, is this terminology applicable to other functional languages, or is it used just in the Has

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  • How to use Eclipse and versioning for a matrix of projects

    - by Nulldevice
    Our company develop several software products, which reuse each others packages (we use Java). Every product represented as separate Eclipse Java project and has it's own versioning repository (we use Mercurial). When we find a bug in some shared package, we need to transfer changes to all consuming projects, and this is a hell. The key problem is that Eclipse project can be associated only with one versioning repository. Could someone recommend some way to associate Eclipse Java project whith several versioning repositories which in ideal may be geterogeious (svn, git, mercurial) ?

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