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Search found 287 results on 12 pages for 'sparse'.

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  • Sparse matrices / arrays in Java

    - by DanM
    I'm working on a project, written in Java, which requires that I build a very large 2-D sparse array. Very sparse, if that makes a difference. Anyway: the most crucial aspect for this application is efficency in terms of time (assume loads of memory, though not nearly so unlimited as to allow me to use a standard 2-D array -- the key range is in

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  • Sparse constrained linear least-squares solver

    - by Jacob
    This great SO answer points to a good sparse solver, but I've got constraints on x (for Ax = b) such that each element in x is >=0 an <=N. The first thing which comes to mind is an QP solver for large sparse matrices. Also, A is huge (around 2e6x2e6) but very sparse with <=4 elements per row. Any ideas/recommendations? I'm looking for

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  • Make huge space savings by using SPARSE columns

    - by simonsabin
    I’ve blogged before about Getting more than 1024 columns on a table , this is done by using sparse columns. Whilst this is potentially useful for people with insane table designs, sparse columns aren’t just for this. My experience over the past few years has shown that sparse columns are useful for almost all databases when you have columns

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  • Sparse quadratic program solver

    - by Jacob
    This great SO answer points to a good sparse solver, but I've got constraints on x (for Ax = b) such that each element in x is >=0 an <=N. The first thing which comes to mind is an QP solver for large sparse matrices. Also, A is huge (around 2e6x2e6) but very sparse with <=4 elements per row. Any ideas/recommendations?

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  • Can I choose a sparse file as vdev for a zfs pool?

    - by Karl Richter
    man zpool states that a vdev for a zfs pool can be a "regular file". Can I specify a sparse file (the warning about the integrity of the file being determined by the underlying filesystem should apply with the same relevance for a sparse file)? The ZFS administration guide on https://pthree.org/2012/12/04/zfs-administration-part-i-vdevs/

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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

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  • Learning about sparse columns and filtered indexes

    - by Christian
    I’ve been brushing up on sparse columns and filtered indexes recently and two resources stood out for me as indispensable so I’d thought I’d share them. Those of you studying for Microsoft Certified Master: SQL Server will no doubt have found the Readiness Videos published on TechNet and Kimberley Tripp’s (Blog|Twitter) webcast

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  • Sparse linear program solver

    - by Jacob
    This great SO answer points to a good sparse solver, but I've got constraints on x (for Ax = b) such that each element in x is >=0 an <=N. The first thing which comes to mind is an LP solver for large sparse matrices. Any ideas/recommendations?

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  • Sparse checkouts and svn:externals

    - by JesperE
    I'm trying to do a sparse checkout of a folder containing externals, but none of the externals are being checked out. This issue seems to indicate that this behavior may be by design, or at least that it isn't clear what the behavior should be. From my point of view, the obvious behavior is that externals are treated just as any

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  • Vectorizatoin of index operation for a scipy.sparse matrix

    - by celil
    The following code runs too slowly even though everything seems to be vectorized. from numpy import * from scipy.sparse import * n = 100000; i = xrange(n); j = xrange(n); data = ones(n); A=csr_matrix((data,(i,j))); x = A[i,j] The problem seems to be that the indexing operation is implemented as a python function, and

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  • Sparse checkout in Git 1.7.0?

    - by davr
    With the new sparse checkout feature in Git 1.7.0, is it possible to just get the contents of a subdirectory like how you can in SVN? I found this example, but it preserves the full directory structure. Imagine that I just wanted the contents of the 'perl' directory, without an actual directory named 'perl'. -- EDIT --

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  • Discrete and Continuous Classifier on Sparse Data

    - by Chris S
    I'm trying to classify an example, which contains discrete and continuous features. Also, the example represents sparse data, so even though the system may have been trained on 100 features, the example may only have 12. What would be the best classifier algorithm to use to accomplish this? I've been looking at Bayes,

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  • create a sparse BufferedImage in java

    - by elgcom
    I have to create an image with very large resolution, but the image is relatively "sparse", only some areas in the image need to draw. For example with following code /* this take 5GB memory */ final BufferedImage img = new BufferedImage( 36000, 36000, BufferedImage.TYPE_INT_ARGB); /* draw something */

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  • Decode sparse json array to php array

    - by Isaac Sutherland
    I can create a sparse php array (or map) using the command: $myarray = array(10=>'hi','test20'=>'howdy'); I want to serialize/deserialize this as JSON. I can serialize it using the command: $json = json_encode($myarray); which results in the string {"10":"hi","test20":"howdy"}. However, when I

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  • MATLAB: Convert two array to a sparse matrix

    - by CziX
    I'm looking for an a command or trick to convert two arrays to a sparse matrix. The two arrays contain x-values and y-values, which gives a coordinate in the cartesian coordinate system. I want to group the coordinates, which if the value is between some value on the x-axes and the y-axes. % MATLAB x_i

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  • best way to get a vector from sparse matrix

    - by niko
    Hi, I have a m x n matrix where each row consists of zeros and same values for each row. an example would be: M = -0.6 1.8 -2.3 0 0 0; 0 0 0 3.4 -3.8 -4.3; -0.6 0 0 3.4 0 0 In this example the first column consists of 0s and -0.6, second 0 and 1.8, third -2.3 and so on. In such case I would

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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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  • Scipy sparse... arrays?

    - by spitzanator
    Hey, folks. So, I'm doing some Kmeans classification using numpy arrays that are quite sparse-- lots and lots of zeroes. I figured that I'd use scipy's 'sparse' package to reduce the storage overhead, but I'm a little confused about how to create arrays, not matrices. I've gone through this

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