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  • Efficient algorithm for creating an ideal distribution of groups into containers?

    - by Inshim
    I have groups of students that need to be allocated into classrooms of a fixed capacity (say, 100 chairs in each). Each group must only be allocated to a single classroom, even if it is larger than the capacity (ie there can be an overflow, with students standing up) I need an algorithm to make the allocations with minimum overflows and under-capacity classrooms. A naive algorithm to do this allocation is horrendously slow when having ~200 groups, with a distribution of about half of them being under 20% of the classroom size. Any ideas where I can find at least some good starting point for making this algorithm lightning fast? Thanks!

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  • Texture not drawing on cubes

    - by Christian Frantz
    I can draw the cubes fine but they are just solid black besides the occasional lighting that goes on. The basic effect is being set for each cube also. public void Draw(BasicEffect effect) { foreach (EffectPass pass in effect.CurrentTechnique.Passes) { pass.Apply(); device.SetVertexBuffer(vertexBuffer); device.Indices = indexBuffer; device.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, 8, 0, 12); } } The cubes draw method. TextureEnabled is set to true in my main draw method. My texture is also loading fine. public Cube(GraphicsDevice graphicsDevice, Vector3 Position, Texture2D Texture) { device = graphicsDevice; texture = Texture; cubePosition = Position; effect = new BasicEffect(device); } The constructor seems fine too. Could this be caused by the Vector2's of my VertexPositionNormalTexture? Even if they were out of order something should still be drawn other than a black cube

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  • Can I use a plaintext diff algorithm for tracking XML changes?

    - by rinogo
    Hi all! Interesting question for you here. I'm working in Flex/AS3 on (for simplicity) an XML editor. I need to provide undo/redo functionality. Of course, one solution is to store the entire source text with each edit. However, to conserve memory, I'd like to store the diffs instead (these diffs will also be used to transmit updates to the server for auto-saving). My question is - can I use a plaintext diff algorithm for tracking these XML changes? My research on the internet indicates that I cannot do so. However, I'm obviously missing something. Plaintext diff provides functionality that is purportedly: diff(text, text') - diffs patch(text, diffs) - text' XML is simply text, so why can't I just use diff() and patch() to transform the text reliably? For example: Let's say that I'm a poet. When I write poetry, I use lots of funky punctuation... You know, like <, /, and . (You might see where I'm going with this...) If I'm writing my poetry in an application that uses diffs to provide undo/redo functionality, does my poetry become garbled when I undo/redo my edits? It's just text! Why does it make a difference to the algorithm? I obviously don't get something here...Thanks for explaining! :) -Rich

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  • O(log n) algorithm for computing rank of union of two sorted lists?

    - by Eternal Learner
    Given two sorted lists, each containing n real numbers, is there a O(log?n) time algorithm to compute the element of rank i (where i coresponds to index in increasing order) in the union of the two lists, assuming the elements of the two lists are distinct? I can think of using a Merge procedure to merge the 2 lists and then find the A[i] element in constant time. But the Merge would take O(n) time. How do we solve it in O(log n) time?

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  • O(log n) algorithm to find the element having rank i in union of pre-sorted lists

    - by Eternal Learner
    Given two sorted lists, each containing n real numbers, is there a O(log?n) time algorithm to compute the element of rank i (where i coresponds to index in increasing order) in the union of the two lists, assuming the elements of the two lists are distinct? I can think of using a Merge procedure to merge the 2 lists and then find the A[i] element in constant time. But the Merge would take O(n) time. How do we solve it in O(log n) time?

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  • How to investigate if opencl is possible for an algorithm

    - by Marnix
    I have a heavy-duty algorithm in C# that takes two large Bitmaps of about 10000x5000 and performs photo and ray collision operations on a 3D model to map photos on the 3D model. I would like to know if it is possible to convert such an algorithm to OpenCL to optimize parallel operations during the algorithm. But before asking you to go into the details of the algorithm, I would like to know how I can investigate if my algorithm is convertible to OpenCL. I am not experienced in OpenCL and I would like to know if it is worth it to get into it and learn how it works. Are there things I have to look for that will definitely not work on the graphics card? (for-loops, recursion) Update: My algorithm goes something like: foreach photo split the photo in 64x64 blocks foreach block cast a ray from the camera to the 3D model foreach triangle in 3D model perform raycheck

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  • GRAPH PROBLEM: find an algorithm to determine the shortest path from one point to another in a recta

    - by newba
    I'm getting such an headache trying to elaborate an appropriate algorithm to go from a START position to a EXIT position in a maze. For what is worth, the maze is rectangular, maxsize 500x500 and, in theory, is resolvable by DFS with some branch and bound techniques ... 10 3 4 7 6 3 3 1 2 2 1 0 2 2 2 4 2 2 5 2 2 1 3 0 2 2 2 2 1 3 3 4 2 3 4 4 3 1 1 3 1 2 2 4 2 2 1 Output: 5 1 4 2 Explanation: Our agent looses energy every time he gives a step and he can only move UP, DOWN, LEFT and RIGHT. Also, if the agent arrives with a remaining energy of zero or less, he dies, so we print something like "Impossible". So, in the input 10 is the initial agent's energy, 3 4 is the START position (i.e. column 3, line 4) and we have a maze 7x6. Think this as a kind of labyrinth, in which I want to find the exit that gives the agent a better remaining energy (shortest path). In case there are paths which lead to the same remaining energy, we choose the one which has the small number of steps, of course. I need to know if a DFS to a maze 500x500 in the worst case is feasible with these limitations and how to do it, storing the remaining energy in each step and the number of steps taken so far. The output means the agent arrived with remaining energy= 5 to the exit pos 1 4 in 2 steps. If we look carefully, in this maze it's also possible to exit at pos 3 1 (column 3, row 1) with the same energy but with 3 steps, so we choose the better one. With these in mind, can someone help me some code or pseudo-code? I have troubles working this around with a 2D array and how to store the remaining energy, the path (or number of steps taken)....

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  • Fast block placement algorithm, advice needed?

    - by James Morris
    I need to emulate the window placement strategy of the Fluxbox window manager. As a rough guide, visualize randomly sized windows filling up the screen one at a time, where the rough size of each results in an average of 80 windows on screen without any window overlapping another. It is important to note that windows will close and the space that closed windows previously occupied becomes available once more for the placement of new windows. The window placement strategy has three binary options: Windows build horizontal rows or vertical columns (potentially) Windows are placed from left to right or right to left Windows are placed from top to bottom or bottom to top Why is the algorithm a problem? It needs to operate to the deadlines of a real time thread in an audio application. At this moment I am only concerned with getting a fast algorithm, don't concern yourself over the implications of real time threads and all the hurdles in programming that that brings. So far I have two choices which I have built loose prototypes for: 1) A port of the Fluxbox placement algorithm into my code. The problem with this is, the client (my program) gets kicked out of the audio server (JACK) when I try placing the worst case scenario of 256 blocks using the algorithm. This algorithm performs over 14000 full (linear) scans of the list of blocks already placed when placing the 256th window. 2) My alternative approach. Only partially implemented, this approach uses a data structure for each area of rectangular free unused space (the list of windows can be entirely separate, and is not required for testing of this algorithm). The data structure acts as a node in a doubly linked list (with sorted insertion), as well as containing the coordinates of the top-left corner, and the width and height. Furthermore, each block data structure also contains four links which connect to each immediately adjacent (touching) block on each of the four sides. IMPORTANT RULE: Each block may only touch with one block per side. The problem with this approach is, it's very complex. I have implemented the straightforward cases where 1) space is removed from one corner of a block, 2) splitting neighbouring blocks so that the IMPORTANT RULE is adhered to. The less straightforward case, where the space to be removed can only be found within a column or row of boxes, is only partially implemented - if one of the blocks to be removed is an exact fit for width (ie column) or height (ie row) then problems occur. And don't even mention the fact this only checks columns one box wide, and rows one box tall. I've implemented this algorithm in C - the language I am using for this project (I've not used C++ for a few years and am uncomfortable using it after having focused all my attention to C development, it's a hobby). The implementation is 700+ lines of code (including plenty of blank lines, brace lines, comments etc). The implementation only works for the horizontal-rows + left-right + top-bottom placement strategy. So I've either got to add some way of making this +700 lines of code work for the other 7 placement strategy options, or I'm going to have to duplicate those +700 lines of code for the other seven options. Neither of these is attractive, the first, because the existing code is complex enough, the second, because of bloat. The algorithm is not even at a stage where I can use it in the real time worst case scenario, because of missing functionality, so I still don't know if it actually performs better or worse than the first approach. What else is there? I've skimmed over and discounted: Bin Packing algorithms: their emphasis on optimal fit does not match the requirements of this algorithm. Recursive Bisection Placement algorithms: sounds promising, but these are for circuit design. Their emphasis is optimal wire length. Both of these, especially the latter, all elements to be placed/packs are known before the algorithm begins. I need an algorithm which works accumulatively with what it is given to do when it is told to do it. What are your thoughts on this? How would you approach it? What other algorithms should I look at? Or even what concepts should I research seeing as I've not studied computer science/software engineering? Please ask questions in comments if further information is needed. [edit] If it makes any difference, the units for the coordinates will not be pixels. The units are unimportant, but the grid where windows/blocks/whatever can be placed will be 127 x 127 units.

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  • Algorithm design, "randomising" timetable schedule in Python although open to other languages.

    - by S1syphus
    Before I start I should add I am a musician and not a native programmer, this was undertook to make my life easier. Here is the situation, at work I'm given a new csv file each which contains a list of sound files, their length, and the minimum total amount of time they must be played. I create a playlist of exactly 60 minutes, from this excel file. Each sample played the by the minimum number of instances, but spread out from each other; so there will never be a period where for where one sound is played twice in a row or in close proximity to itself. Secondly, if the minimum instances of each song has been used, and there is still time with in the 60 min, it needs to fill the remaining time using sounds till 60 minutes is reached, while adhering to above. The smallest duration possible is 15 seconds, and then multiples of 15 seconds. Here is what I came up with in python and the problems I'm having with it, and as one user said its buggy due to the random library used in it. So I'm guessing a total rethink is on the table, here is where I need your help. Whats is the best way to solve the issue, I have had a brief look at things like knapsack and bin packing algorithms, while both are relevant neither are appropriate and maybe a bit beyond me.

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  • Diff Algorithm

    - by Daniel Magliola
    I've been looking like crazy for an explanation of a diff algorithm that works and is efficient. The closest I got is this link to RFC 3284 (from several Eric Sink blog posts), which describes in perfectly understandable terms the data format in which the diff results are stored. However, it has no mention whatsoever as to how a program would reach these results while doing a diff. I'm trying to research this out of personal curiosity, because I'm sure there must be tradeoffs when implementing a diff algorithm, which are pretty clear sometimes when you look at diffs and wonder "why did the diff program chose this as a change instead of that?"... Does anyone know where I can find a description of an efficient algorithm that'd end up outputting VCDIFF? By the way, if you happen to find a description of the actual algorithm used by SourceGear's DiffMerge, that'd be even better. NOTE: longest common subsequence doesn't seem to be the algorithm used by VCDIFF, it looks like they're doing something smarter, given the data format they use. Thanks!

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  • Optimizing drawing of cubes

    - by Christian Frantz
    After googling for hours I've come to a few conclusions, I need to either rewrite my whole cube class, or figure out how to use hardware instancing. I can draw up to 2500 cubes with little lag, but after that my fps drops. Is there a way I can use my class for hardware instancing? Or would I be better off rewriting my class for optimization? public class Cube { public GraphicsDevice device; public VertexBuffer cubeVertexBuffer; public Cube(GraphicsDevice graphicsDevice) { device = graphicsDevice; var vertices = new List<VertexPositionTexture>(); BuildFace(vertices, new Vector3(0, 0, 0), new Vector3(0, 1, 1)); BuildFace(vertices, new Vector3(0, 0, 1), new Vector3(1, 1, 1)); BuildFace(vertices, new Vector3(1, 0, 1), new Vector3(1, 1, 0)); BuildFace(vertices, new Vector3(1, 0, 0), new Vector3(0, 1, 0)); BuildFaceHorizontal(vertices, new Vector3(0, 1, 0), new Vector3(1, 1, 1)); BuildFaceHorizontal(vertices, new Vector3(0, 0, 1), new Vector3(1, 0, 0)); cubeVertexBuffer = new VertexBuffer(device, VertexPositionTexture.VertexDeclaration, vertices.Count, BufferUsage.WriteOnly); cubeVertexBuffer.SetData<VertexPositionTexture>(vertices.ToArray()); } private void BuildFace(List<VertexPositionTexture> vertices, Vector3 p1, Vector3 p2) { vertices.Add(BuildVertex(p1.X, p1.Y, p1.Z, 1, 0)); vertices.Add(BuildVertex(p1.X, p2.Y, p1.Z, 1, 1)); vertices.Add(BuildVertex(p2.X, p2.Y, p2.Z, 0, 1)); vertices.Add(BuildVertex(p2.X, p2.Y, p2.Z, 0, 1)); vertices.Add(BuildVertex(p2.X, p1.Y, p2.Z, 0, 0)); vertices.Add(BuildVertex(p1.X, p1.Y, p1.Z, 1, 0)); } private void BuildFaceHorizontal(List<VertexPositionTexture> vertices, Vector3 p1, Vector3 p2) { vertices.Add(BuildVertex(p1.X, p1.Y, p1.Z, 0, 1)); vertices.Add(BuildVertex(p2.X, p1.Y, p1.Z, 1, 1)); vertices.Add(BuildVertex(p2.X, p2.Y, p2.Z, 1, 0)); vertices.Add(BuildVertex(p1.X, p1.Y, p1.Z, 0, 1)); vertices.Add(BuildVertex(p2.X, p2.Y, p2.Z, 1, 0)); vertices.Add(BuildVertex(p1.X, p1.Y, p2.Z, 0, 0)); } private VertexPositionTexture BuildVertex(float x, float y, float z, float u, float v) { return new VertexPositionTexture(new Vector3(x, y, z), new Vector2(u, v)); } public void Draw(BasicEffect effect) { foreach (EffectPass pass in effect.CurrentTechnique.Passes) { pass.Apply(); device.SetVertexBuffer(cubeVertexBuffer); device.DrawPrimitives(PrimitiveType.TriangleList, 0, cubeVertexBuffer.VertexCount / 3); } } } The following class is a list that draws the cubes. public class DrawableList<T> : DrawableGameComponent { private BasicEffect effect; private ThirdPersonCam camera; private class Entity { public Vector3 Position { get; set; } public Matrix Orientation { get; set; } public Texture2D Texture { get; set; } } private Cube cube; private List<Entity> entities = new List<Entity>(); public DrawableList(Game game, ThirdPersonCam camera, BasicEffect effect) : base(game) { this.effect = effect; cube = new Cube(game.GraphicsDevice); this.camera = camera; } public void Add(Vector3 position, Matrix orientation, Texture2D texture) { entities.Add(new Entity() { Position = position, Orientation = orientation, Texture = texture }); } public override void Draw(GameTime gameTime) { foreach (var item in entities) { effect.VertexColorEnabled = false; effect.TextureEnabled = true; effect.Texture = item.Texture; Matrix center = Matrix.CreateTranslation(new Vector3(-0.5f, -0.5f, -0.5f)); Matrix scale = Matrix.CreateScale(1f); Matrix translate = Matrix.CreateTranslation(item.Position); effect.World = center * scale * translate; effect.View = camera.view; effect.Projection = camera.proj; effect.FogEnabled = true; effect.FogColor = Color.CornflowerBlue.ToVector3(); effect.FogStart = 1.0f; effect.FogEnd = 50.0f; cube.Draw(effect); } base.Draw(gameTime); } } } There are probably many reasons that my fps is so slow, but I can't seem to figure out how to fix it. I've looked at techcraft as well, but what I have is too specific to what I want the outcome to be to just rewrite everything from scratch

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  • Algorithm to reduce a bitmap mask to a list of rectangles?

    - by mos
    Before I go spend an afternoon writing this myself, I thought I'd ask if there was an implementation already available --even just as a reference. The first image is an example of a bitmap mask that I would like to turn into a list of rectangles. A bad algorithm would return every set pixel as a 1x1 rectangle. A good algorithm would look like the second image, where it returns the coordinates of the orange and red rectangles. The fact that the rectangles overlap don't matter, just that there are only two returned. To summarize, the ideal result would be these two rectangles (x, y, w, h): [ { 3, 1, 2, 6 }, { 1, 3, 6, 2 } ]

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  • Why hill climbing is called anytime algorithm?

    - by crucified soul
    From wikipedia, Anytime algorithm In computer science an anytime algorithm is an algorithm that can return a valid solution to a problem even if it's interrupted at any time before it ends. The algorithm is expected to find better and better solutions the more time it keeps running. Hill climbing Hill climbing can often produce a better result than other algorithms when the amount of time available to perform a search is limited, such as with real-time systems. It is an anytime algorithm: it can return a valid solution even if it's interrupted at any time before it ends. Hill climbing algorithm can stuck into local optima or ridge, after that even if it runs infinite time, the result won't be any better. Then, why hill climbing is called anytime algorithm?

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  • Dijkstra’s algorithm and functions

    - by baris_a
    Hi guys, the question is: suppose I have an input function like sin(2-cos(3*A/B)^2.5)+0.756*(C*D+3-B) specified with a BNF, I will parse input using recursive descent algorithm, and then how can I use or change Dijkstra’s algorithm to handle this given function? After parsing this input function, I need to execute it with variable inputs, where Dijkstra’s algorithm should do the work. Thanks in advance. EDIT: May be I should ask also: What is the best practice or data structure to represent given function?

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  • Efficient algorithm for finding largest eigenpair of small general complex matrix

    - by mklassen
    I am looking for an efficient algorithm to find the largest eigenpair of a small, general (non-square, non-sparse, non-symmetric), complex matrix, A, of size m x n. By small I mean m and n is typically between 4 and 64 and usually around 16, but with m not equal to n. This problem is straight forward to solve with the general LAPACK SVD algorithms, i.e. gesvd or gesdd. However, as I am solving millions of these problems and only require the largest eigenpair, I am looking for a more efficient algorithm. Additionally, in my application the eigenvectors will generally be similar for all cases. This lead me to investigate Arnoldi iteration based methods, but I have neither found a good library nor algorithm that applies to my small general complex matrix. Is there an appropriate algorithm and/or library?

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  • Algorithm for Text Wrapping Within a Shape

    - by devongovett
    I am looking for an algorithm to wrap text within a non-rectangular shape, preferably based on the Knuth and Plass algorithm. The hardest part of this is that the lines may have different heights due to differing font sizes in the text. The image below is an example of what the algorithm should be able to generate. Thanks for any help!

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  • Clustering [assessment] algorithm with distance matrix as an input

    - by Max
    Can anyone suggest some clustering algorithm which can work with distance matrix as an input? Or the algorithm which can assess the "goodness" of the clustering also based on the distance matrix? At this moment I'm using a modification of Kruskal's algorithm (http://en.wikipedia.org/wiki/Kruskal%27s_algorithm) to split data into two clusters. It has a problem though. When the data has no distinct clusters the algorithm will still create two clusters with one cluster containing one element and the other containing all the rest. In this case I would rather have one cluster containing all the elements and another one which is empty. Are there any algorithms which are capable of doing this type of clustering? Are there any algorithms which can estimate how well the clustering was done or even better how many clusters are there in the data? The algorithms should work only with distance(similarity) matrices as an input.

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  • Dijkstra's algorithm: why does it work? (not how)

    - by BeeBand
    I understand what Dijkstra's algorithm is but I don't understand why it works. When selecting the next vertice to examine, why does Dijkstra's algorithm select the one with the smallest weight? Why not just select a vertex arbitrarily, since the algorithm visits all vertices anyway?

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  • Algorithm for matching partially filled words

    - by adnanhb
    Hello All, I am writing a game which when given a partially filled word, searches a dictionary and returns all the matching words. To that effect, I am trying to find an algorithm that can be used for the said purpose. For example, given - - a -, the algorithm will search a dictionary for all the words which have length 4 and have 'a' as the third letter. Is there such an algorithm already? If not, can somebody given a rough idea of how to design such an algorithm? Thanks in Advance.

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  • SQL SERVER – BI Quiz Hint – Performance Tuning Cubes – Hints

    - by pinaldave
    I earlier wrote about SQL BI Quiz over here and here. The details of the quiz is here: Working with huge data is very common when it is about Data Warehousing. It is necessary to create Cubes on the data to make it meaningful and consumable. There are cases when retrieving the data from cube takes lots of the time. Let us assume that your cube is returning you data very quickly. Suddenly on one day it is returning the data very slowly. What are the three things will you to diagnose this. After diagnose what you will do to resolve performance issue. Participate in my question over here I required BI Expert Jason Thomas to help with few hints to blog readers. He is one of the leading SSAS expert and writes a complicated subject in simple words. If queries were executing properly before but now take a long time to return the data, it means that there has been a change in the environment in which it is running. Some possible changes are listed below:-  1) Data factors:- Compare the data size then and now. Increase in data can result in different execution times. Poorly written queries as well as poor design will not start showing issues till the data grows. How to find it out? (Ans : SQL Server profiler and Perfmon Counters can be used for identifying the issues and performance  tuning the MDX queries)  2) Internal Factors:- Is some slow MDX query / multiple mdx queries running at the same time, which was not running when you had tested it before? Is there any locking happening due to proactive caching or processing operations? Are the measure group caches being cleared by processing operations? (Ans : Again, profiler and perfmon counters will help in finding it out. Load testing can be done using AS Performance Workbench (http://asperfwb.codeplex.com/) by running multiple queries at once)  3) External factors:- Is some other application competing for the same resources?  HINT : Read “Identifying and Resolving MDX Query Performance Bottlenecks in SQL Server 2005 Analysis Services” (http://sqlcat.com/whitepapers/archive/2007/12/16/identifying-and-resolving-mdx-query-performance-bottlenecks-in-sql-server-2005-analysis-services.aspx) Well, these are great tips. Now win big prizes by participate in my question over here. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • isometric drawing order with larger than single tile images - drawing order algorithm?

    - by Roger Smith
    I have an isometric map over which I place various images. Most images will fit over a single tile, but some images are slightly larger. For example, I have a bed of size 2x3 tiles. This creates a problem when drawing my objects to the screen as I get some tiles erroneously overlapping other tiles. The two solutions that I know of are either splitting the image into 1x1 tile segments or implementing my own draw order algorithm, for example by assigning each image a number. The image with number 1 is drawn first, then 2, 3 etc. Does anyone have advice on what I should do? It seems to me like splitting an isometric image is very non obvious. How do you decide which parts of the image are 'in' a particular tile? I can't afford to split up all of my images manually either. The draw order algorithm seems like a nicer choice but I am not sure if it's going to be easy to implement. I can't solve, in my head, how to deal with situations whereby you change the index of one image, which causes a knock on effect to many other images. If anyone has an resources/tutorials on this I would be most grateful.

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  • What algorithm to use to fill a KenKen square board with cages?

    - by JimmyBoh
    I am working on recreating KenKen, a popular math puzzle involving a blank grid that is divided into "cages". Each cage is just a collection of adjacent squares and has a clue which is generally a number and an operand, shown below: What type of algorithm would be best to fill the square with cages? Assume the maximum number of cells per cage would be 3 and the board is 4x4 in size, like in the example above.

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  • Lawler's Algorithm Implementation Assistance

    - by Richard Knop
    Here is my implemenation of Lawler's algorithm in PHP (I know... but I'm used to it): <?php $jobs = array(1, 2, 3, 4, 5, 6); $jobsSubset = array(2, 5, 6); $n = count($jobs); $processingTimes = array(2, 3, 4, 3, 2, 1); $dueDates = array(3, 15, 9, 7, 11, 20); $optimalSchedule = array(); foreach ($jobs as $j) { $optimalSchedule[] = 0; } $dicreasedCardinality = array(); for ($i = $n; $i >= 1; $i--) { $x = 0; $max = 0; // loop through all jobs for ($j = 0; $j < $i; $j++) { // ignore if $j already is in the $dicreasedCardinality array if (false === in_array($j, $dicreasedCardinality)) { // if the job has no succesor in $jobsSubset if (false === isset($jobs[$j+1]) || false === in_array($jobs[$j+1], $jobsSubset)) { // here I find an array index of a job with the maximum due date // amongst jobs with no sucessor in $jobsSubset if ($x < $dueDates[$j]) { $x = $dueDates[$j]; $max = $j; } } } } // move the job at the end of $optimalSchedule $optimalSchedule[$i-1] = $jobs[$max]; // decrease the cardinality of $jobs $dicreasedCardinality[] = $max; } print_r($optimalSchedule); Now the above returns an optimal schedule like this: Array ( [0] => 1 [1] => 1 [2] => 1 [3] => 3 [4] => 2 [5] => 6 ) Which doesn't seem right to me. The problem might be with my implementation of the algorithm because I am not sure I understand it correctly. I used this source to implement it: http://www.google.com/books?id=aSiBs6PDm9AC&pg=PA166&dq=lawler%27s+algorithm+code&lr=&hl=sk&cd=4#v=onepage&q=&f=false The description there is a little confusing. For example, I didn't quite get how is the subset D defined (I guess it is arbitrary). Could anyone help me out with this? I have been trying to find some sources with simpler explanation of the algorithm but all sources I found were even more complicated (with math proofs and such) so I am stuck with the link above. Yes, this is a homework, if it wasn't obvious. I still have few weeks to crack this but I have spent few days already trying to get how exactly this algorithm works with no success so I don't think I will get any brighter during that time.

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  • SSIS: Deploying OLAP cubes using C# script tasks and AMO

    - by DrJohn
    As part of the continuing series on Building dynamic OLAP data marts on-the-fly, this blog entry will focus on how to automate the deployment of OLAP cubes using SQL Server Integration Services (SSIS) and Analysis Services Management Objects (AMO). OLAP cube deployment is usually done using the Analysis Services Deployment Wizard. However, this option was dismissed for a variety of reasons. Firstly, invoking external processes from SSIS is fraught with problems as (a) it is not always possible to ensure SSIS waits for the external program to terminate; (b) we cannot log the outcome properly and (c) it is not always possible to control the server's configuration to ensure the executable works correctly. Another reason for rejecting the Deployment Wizard is that it requires the 'answers' to be written into four XML files. These XML files record the three things we need to change: the name of the server, the name of the OLAP database and the connection string to the data mart. Although it would be reasonably straight forward to change the content of the XML files programmatically, this adds another set of complication and level of obscurity to the overall process. When I first investigated the possibility of using C# to deploy a cube, I was surprised to find that there are no other blog entries about the topic. I can only assume everyone else is happy with the Deployment Wizard! SSIS "forgets" assembly references If you build your script task from scratch, you will have to remember how to overcome one of the major annoyances of working with SSIS script tasks: the forgetful nature of SSIS when it comes to assembly references. Basically, you can go through the process of adding an assembly reference using the Add Reference dialog, but when you close the script window, SSIS "forgets" the assembly reference so the script will not compile. After repeating the operation several times, you will find that SSIS only remembers the assembly reference when you specifically press the Save All icon in the script window. This problem is not unique to the AMO assembly and has certainly been a "feature" since SQL Server 2005, so I am not amazed it is still present in SQL Server 2008 R2! Sample Package So let's take a look at the sample SSIS package I have provided which can be downloaded from here: DeployOlapCubeExample.zip  Below is a screenshot after a successful run. Connection Managers The package has three connection managers: AsDatabaseDefinitionFile is a file connection manager pointing to the .asdatabase file you wish to deploy. Note that this can be found in the bin directory of you OLAP database project once you have clicked the "Build" button in Visual Studio TargetOlapServerCS is an Analysis Services connection manager which identifies both the deployment server and the target database name. SourceDataMart is an OLEDB connection manager pointing to the data mart which is to act as the source of data for your cube. This will be used to replace the connection string found in your .asdatabase file Once you have configured the connection managers, the sample should run and deploy your OLAP database in a few seconds. Of course, in a production environment, these connection managers would be associated with package configurations or set at runtime. When you run the sample, you should see that the script logs its activity to the output screen (see screenshot above). If you configure logging for the package, then these messages will also appear in your SSIS logging. Sample Code Walkthrough Next let's walk through the code. The first step is to parse the connection string provided by the TargetOlapServerCS connection manager and obtain the name of both the target OLAP server and also the name of the OLAP database. Note that the target database does not have to exist to be referenced in an AS connection manager, so I am using this as a convenient way to define both properties. We now connect to the server and check for the existence of the OLAP database. If it exists, we drop the database so we can re-deploy. svr.Connect(olapServerName); if (svr.Connected) { // Drop the OLAP database if it already exists Database db = svr.Databases.FindByName(olapDatabaseName); if (db != null) { db.Drop(); } // rest of script } Next we start building the XMLA command that will actually perform the deployment. Basically this is a small chuck of XML which we need to wrap around the large .asdatabase file generated by the Visual Studio build process. // Start generating the main part of the XMLA command XmlDocument xmlaCommand = new XmlDocument(); xmlaCommand.LoadXml(string.Format("<Batch Transaction='false' xmlns='http://schemas.microsoft.com/analysisservices/2003/engine'><Alter AllowCreate='true' ObjectExpansion='ExpandFull'><Object><DatabaseID>{0}</DatabaseID></Object><ObjectDefinition/></Alter></Batch>", olapDatabaseName));  Next we need to merge two XML files which we can do by simply using setting the InnerXml property of the ObjectDefinition node as follows: // load OLAP Database definition from .asdatabase file identified by connection manager XmlDocument olapCubeDef = new XmlDocument(); olapCubeDef.Load(Dts.Connections["AsDatabaseDefinitionFile"].ConnectionString); // merge the two XML files by obtain a reference to the ObjectDefinition node oaRootNode.InnerXml = olapCubeDef.InnerXml;   One hurdle I had to overcome was removing detritus from the .asdabase file left by the Visual Studio build. Through an iterative process, I found I needed to remove several nodes as they caused the deployment to fail. The XMLA error message read "Cannot set read-only node: CreatedTimestamp" or similar. In comparing the XMLA generated with by the Deployment Wizard with that generated by my code, these read-only nodes were missing, so clearly I just needed to strip them out. This was easily achieved using XPath to find the relevant XML nodes, of which I show one example below: foreach (XmlNode node in rootNode.SelectNodes("//ns1:CreatedTimestamp", nsManager)) { node.ParentNode.RemoveChild(node); } Now we need to change the database name in both the ID and Name nodes using code such as: XmlNode databaseID = xmlaCommand.SelectSingleNode("//ns1:Database/ns1:ID", nsManager); if (databaseID != null) databaseID.InnerText = olapDatabaseName; Finally we need to change the connection string to point at the relevant data mart. Again this is easily achieved using XPath to search for the relevant nodes and then replace the content of the node with the new name or connection string. XmlNode connectionStringNode = xmlaCommand.SelectSingleNode("//ns1:DataSources/ns1:DataSource/ns1:ConnectionString", nsManager); if (connectionStringNode != null) { connectionStringNode.InnerText = Dts.Connections["SourceDataMart"].ConnectionString; } Finally we need to perform the deployment using the Execute XMLA command and check the returned XmlaResultCollection for errors before setting the Dts.TaskResult. XmlaResultCollection oResults = svr.Execute(xmlaCommand.InnerXml);  // check for errors during deployment foreach (Microsoft.AnalysisServices.XmlaResult oResult in oResults) { foreach (Microsoft.AnalysisServices.XmlaMessage oMessage in oResult.Messages) { if ((oMessage.GetType().Name == "XmlaError")) { FireError(oMessage.Description); HadError = true; } } } If you are not familiar with XML programming, all this may all seem a bit daunting, but perceiver as the sample code is pretty short. If you would like the script to process the OLAP database, simply uncomment the lines in the vicinity of Process method. Of course, you can extend the script to perform your own custom processing and to even synchronize the database to a front-end server. Personally, I like to keep the deployment and processing separate as the code can become overly complex for support staff.If you want to know more, come see my session at the forthcoming SQLBits conference.

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