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  • C# [Mono]: MPAPI vs MPI.NET vs ?

    - by Olexandr
    Hi. I'm working on college project. I have to develop distributed computing system. And i decided to do some research to make this task fun :) I've found MPAPI and MPI.NET libraries. Yes, they are .NET libraries(Mono, in my case). Why .NET ? I'm choosing between Ada, C++ and C# so to i've choosed C# because of lower development time. I have two goals: Simplicity; Performance; Cluster computing. So, what to choose - MPAPI or MPI.NET or something else ?

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  • Comparison of the multiprocessing module and pyro?

    - by fivebells
    I use pyro for basic management of parallel jobs on a compute cluster. I just moved to a cluster where I will be responsible for using all the cores on each compute node. (On previous clusters, each core has been a separate node.) The python multiprocessing module seems like a good fit for this. I notice it can also be used for remote-process communication. If anyone has used both frameworks for remote-process communication, I'd be grateful to hear how they stack up against each other. The obvious benefit of the multiprocessing module is that it's built-in from 2.6. Apart from that, it's hard for me to tell which is better.

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  • Best approach for GPGPU/CUDA/OpenCL in Java?

    - by Frederik
    General-purpose computing on graphics processing units (GPGPU) is a very attractive concept to harness the power of the GPU for any kind of computing. I'd love to use GPGPU for image processing, particles, and fast geometric operations. Right now, it seems the two contenders in this space are CUDA and OpenCL. I'd like to know: Is OpenCL usable yet from Java on Windows/Mac? What are the libraries ways to interface to OpenCL/CUDA? Is using JNA directly an option? Am I forgetting something? Any real-world experience/examples/war stories are appreciated.

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  • Al Zimmermann's Son of Darts

    - by polygenelubricants
    There's about 2 months left in Al Zimmermann's Son of Darts programming contest, and I'd like to improve my standing (currently in the 60s) to something more respectable. I'd like to get some ideas from the great community of stackoverflow on how best to approach this problem. The contest problem is known as the Global Postage Stamp Problem in literatures. I don't have much experience with optimization algorithms (I know of hillclimbing and simulated annealing in concept only from college), and in fact the program that I have right now is basically sheer brute force, which of course isn't feasible for the larger search spaces. Here are some papers on the subject: A Postage Stamp Problem (Alter & Barnett, 1980) Algorithms for Computing the h-Range of the Postage Stamp Problem (Mossige, 1981) A Postage Stamp Problem (Lunnon, 1986) Two New Techniques for Computing Extremal h-bases Ak (Challis, 1992) Any hints and suggestions are welcome. Also, feel free to direct me to the proper site if stackoverflow isn't it.

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  • RequestDispatcher forward between Tomcat instances

    - by MontyBongo
    I have a scenario where I have single entry point Servlet and further Servlets that requests are forwarded to that undertake heavy processing. I am looking at options to distribute this load and I would like to know if it is possible using Tomcat or another platform to forward requests between Servlets sitting on different servers using a cluster type configuration or similar. I have found some documentation on clustering Servlets and Tomcat but none indicate if Servlet request forwarding is possible from what I can see. http://java.sun.com/blueprints/guidelines/designing_enterprise_applications_2e/web-tier/web-tier5.html http://tomcat.apache.org/tomcat-5.5-doc/cluster-howto.html

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  • OpenCV's cvKMeans2 - chosing clusters

    - by Goffrey
    Hi, I'm using cvKMeans2 for clustering, but I'm not sure, how it works in general - the part of choosing clusters. I thought that it set the first positions of clusters from given samples. So it means that in the end of clustering process would every cluster has at least one sample - in the output array of cluster labels will be full range of numbers (for 100 clusters - numbers 0 to 99). But as I checked output labels, I realised that some labels weren't used at all and only some were used. So, does anyone know, how it works? Or how should I use the parameters of cvKMeans2 to do what I want (cause I'm not sure if I use them right)? I'm using cvKMeans2 function also with optional parameters: cvKMeans2(descriptorMat, N_CLUSTERS, clusterLabels, cvTermCriteria( CV_TERMCRIT_EPS+CV_TERMCRIT_ITER, 10, 1.0), 1, 0, 0, clusterCenters, 0) Thanks for any advices!

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  • ASP.NET MVC Validation of ViewState MAC failed

    - by Kevin Pang
    After publishing a new build of my ASP.NET MVC web application, I often see this exception thrown when browsing to the site: System.Web.Mvc.HttpAntiForgeryException: A required anti-forgery token was not supplied or was invalid. --- System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. --- System.Web.UI.ViewStateException: Invalid viewstate. This exception will continue to occur on each page I visit in my web application until I close out of Firefox. After reopening Firefox, the site works perfectly. Any idea what's going on? Additional notes: I am not using any ASP.NET web controls (there are no instances of runat="server" in my application) If I take out the <%= Html.AntiForgeryToken % from my pages, this problem seems to go away

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  • geographical deployment Vs geo load balancing SharePoint 2010

    - by vrajaraman
    we have a company wide SharePoint portals planned for few thousand users. since the users are distributed among different countries and their applications (hosted in sharepoint) We would like to consider geo deployment Vs geo load balancing. Please share your inputs. We are aware of this, Geo SharePoint Cluster facilitates - Farms at Central and other sites , db into regional. 2 db cluster - syncing using logshipping or SAN sync or SQL 2008 features like database mirroing Vs Loading balancing using URL and some 3rd party. all farm,sites,db centralised. benefits expecting. 1 High availability. 2.diaster recovering management. 3.maintenance hope i miss some of the points to be covered

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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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  • C# - Data Clustering approach

    - by Brett
    Hi all, I am writing a program in C# in which I have a set of 200 points displayed on an image. However, the points tend to cluster in various regions, and I am looking to find a way to "cluster." In other words, maybe draw a circle/ellipse around the clustered points. Has anyone seen any way to do this? I have heard about K-means clustering, but I am not sure how to implement it in C#. Any favorite implementations out there? Cheers, Brett

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  • Tips on deploying Ror

    - by notnoop
    How can I go about deploying a Rails app on a cluster of Amazon EC2 servers? Any recommended guides? I maintain a RoR app (currently hosted on Heroku) that uses a DB and DelayedJobs). The app has a large footprint, and needs to be distributed on a cluster most likely. Any tips would be appreciated. Are there Amazon AMIs that replicate some of Heroku's features (especially DJ)? P.S. I'm quite a Ruby newbie.

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  • AJAX with Web services and ASP.NET SessionState

    - by needhelp1
    We have an application which uses ScriptManager to generate a client-side proxy which makes AJAX calls to web services. The web services being invoked live in a separate appDomain(separate cluster altogether). The problem is that our application uses a State server for storing session. I want the web services to be able to access session also. First off, does anyone see anything wrong with the client making web service calls to a separate cluster(we're hoping this would be a better approach for scalability)? I was thinking that possibly anytime there is an update to the session dictionary in one appDomain, automatically update the session in the other appDomain also(referring to the web service appDomain, don't know how to do this, only theoretical). What do others think? Thanks!

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  • Converting Json to Java

    - by Binaryrespawn
    Hi all, I want to be able to access properties from a json string within my java action method. The string is available by simply saying myJsonString = object.getJson(); Below is an example of what the string can look like: {'title': 'Computing and Information systems','id':1,'children': 'true','groups': [{'title': 'Level one CIS','id':2,'children': 'true','groups':[{'title': 'Intro To Computing and Internet','id':3,'children': 'false','groups':[]}]}]} In this string every json object contains an array of other json objects. The intention is to extract a list of id's where any given object possessing a group property that contains other json objects. I looked at google's Gson as a potential json plugin. Can anyone offer some form of guidance as to how I can generate java from this json string? Thank you, Kind regards.

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  • Essential skills of a Data Scientist

    - by harshsinghal
    I would like to know more about the relevant skills in the arsenal of a Data Scientist, and with new technologies coming in every day, how one picks and chooses the essentials. A few ideas germane to this discussion: Knowing SQL and the use of a DB such as MySQL, PostgreSQL was great till the advent of NoSql and non-relational databases. MongoDB, CouchDB etc. are becoming popular to work with web-scale data. Knowing a stats tool like R is enough for analysis, but to create applications one may need to add Java, Python, and such others to the list. Data now comes in the form of text, urls, multi-media to name a few, and there are different paradigms associated with their manipulation. What about cluster computing, parallel computing, the cloud, Amazon EC2, Hadoop ? OLS Regression now has Artificial Neural Networks, Random Forests and other relatively exotic machine learning/data mining algos. for company Thoughts?

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  • complex mysql query problem

    - by Scarface
    Hey guys I have a query that selects data and organizes but not in the correct order. What I want to do is select all the comments for a user in that week and sort it by each topic, then sort the cluster by the latest timestamp of each comment in their respective cluster. My current query selects the right data, but in seemingly random order. Does anyone have any ideas? select * from ( SELECT topic.topic_title, topic.topic_id FROM comments JOIN topic ON topic.topic_id=comments.topic_id WHERE comments.user='$user' AND comments.timestamp>$week order by comments.timestamp desc) derived_table group by topic_id

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  • Segmenting a double array of labels

    - by Ami
    The Problem: I have a large double array populated with various labels. Each element (cell) in the double array contains a set of labels and some elements in the double array may be empty. I need an algorithm to cluster elements in the double array into discrete segments. A segment is defined as a set of pixels that are adjacent within the double array and one label that all those pixels in the segment have in common. (Diagonal adjacency doesn't count and I'm not clustering empty cells). |-------|-------|------| | Jane | Joe | | | Jack | Jane | | |-------|-------|------| | Jane | Jane | | | | Joe | | |-------|-------|------| | | Jack | Jane | | | Joe | | |-------|-------|------| In the above arrangement of labels distributed over nine elements, the largest cluster is the “Jane” cluster occupying the four upper left cells. What I've Considered: I've considered iterating through every label of every cell in the double array and testing to see if the cell-label combination under inspection can be associated with a preexisting segment. If the element under inspection cannot be associated with a preexisting segment it becomes the first member of a new segment. If the label/cell combination can be associated with a preexisting segment it associates. Of course, to make this method reasonable I'd have to implement an elaborate hashing system. I'd have to keep track of all the cell-label combinations that stand adjacent to preexisting segments and are in the path of the incrementing indices that are iterating through the double array. This hash method would avoid having to iterate through every pixel in every preexisting segment to find an adjacency. Why I Don't Like it: As is, the above algorithm doesn't take into consideration the case where an element in the double array can be associated with two unique segments, one in the horizontal direction and one in the vertical direction. To handle these cases properly, I would need to implement a test for this specific case and then implement a method that will both associate the element under inspection with a segment and then concatenate the two adjacent identical segments. On the whole, this method and the intricate hashing system that it would require feels very inelegant. Additionally, I really only care about finding the large segments in the double array and I'm much more concerned with the speed of this algorithm than with the accuracy of the segmentation, so I'm looking for a better way. I assume there is some stochastic method for doing this that I haven't thought of. Any suggestions?

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  • MPAPI vs MPI.NET vs ?

    - by Olexandr
    I'm working on college project. I have to develop distributed computing system. And i decided to do some research to make this task fun :) I've found MPAPI and MPI.NET libraries. Yes, they are .NET libraries(Mono, in my case). Why .NET ? I'm choosing between Ada, C++ and C# so to i've choosed C# because of lower development time. I have two goals: Simplicity; Performance; Cluster computing. So, what to choose - MPAPI or MPI.NET or something else ?

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  • Why do mainframe greybeards refer to DB2/zOS as "he"? [closed]

    - by Alex Nauda
    If you ask a DB2/zOS engine DBA a question about DB2's behavior, the DBA will refer to the DB2 engine as "he" much the way a sailor uses "she" to refer to his ship. For example: "Once you fill the freespace, DB2 still wants to keep those rows in cluster order in the tablespace. That's why he'll split that page in half, and you end up with lots of half-empty pages. That is, unless the cluster key of the row you've just inserted is the highest in the table, in which case he makes a new empty page, and he puts just your new row into that page. So I wouldn't have to do this REORG if you would just sort your input like I suggested." Does anyone know where this tradition comes from?

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  • Distributed, persistent cache using EHCache

    - by Richard
    I currently have a distributed cache using EHCache via RMI that works just fine. I was wondering if you can include persistence with the caches to create a distributed, persistent cache. Alongside this, if the cache was persistent, would it load from the file store, then bootstrap from the cache cluster? Basically, what I want is: Cache starts Cache loads persistent objects from the file store Cache joins the distruted cluster and bootstraps as normal The usecase behind this is having 2 identical components running on independent machines, distributing the cache to avoid losing data in the event that one of the components fails. The persistence would guard against losing all data on the rare occasion that both components fail. Would moving to another distribution method (such as Terracotta) support this?

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  • Emacs/xterm color annoyance on Linux

    - by tgamblin
    I'm using emacs in a console window both on my local Linux box and on the login node of a remote cluster. I use emacs regularly, and I've got the foreground color set to white in my .emacs file like so: (set-foreground-color "white") (set-background-color "black") However, when I run emacs, the foreground isn't white; it's grey and very hard to read. On my Mac, emacs in a console window with the same settings shows up as proper white. But on both linux boxes, in konsole and xterm, it's grey. In case it matters, I've got TERM set to xterm-color, the desktop is running RHEL 5, and the cluster node is running RHEL 4 (CentOS). Is this some default with how Linux sets up terminal colors? How do I get white to be white? Note: this is with console emacs, not emacs under X. That's emacs -nw if you have DISPLAY set.

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  • Optimal Sharing of heavy computation job using Snow and/or multicore

    - by James
    Hi, I have the following problem. First my environment, I have two 24-CPU servers to work with and one big job (resampling a large dataset) to share among them. I've setup multicore and (a socket) Snow cluster on each. As a high-level interface I'm using foreach. What is the optimal sharing of the job? Should I setup a Snow cluster using CPUs from both machines and split the job that way (i.e. use doSNOW for the foreach loop). Or should I use the two servers separately and use multicore on each server (i.e. split the job in two chunks, run them on each server and then stich it back together). Basically what is an easy way to: 1. Keep communication between servers down (since this is probably the slowest bit). 2. Ensure that the random numbers generated in the servers are not highly correlated.

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