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  • Is this an example of LINQ-to-SQL?

    - by Edward Tanguay
    I made a little WPF application with a SQL CE database. I built the following code with LINQ to get data out of the database, which was surprisingly easy. So I thought "this must be LINQ-to-SQL". Then I did "add item" and added a "LINQ-to-SQL classes" .dbml file, dragged my table onto the Object Relational Designer but it said, "The selected object uses an unsupported data provider." So then I questioned whether or not the following code actually is LINQ-to-SQL, since it indeed allows me to access data from my SQL CE database file, yet officially "LINQ-to-SQL" seems to be unsupported for SQL CE. So is the following "LINQ-to-SQL" or not? using System.Linq; using System.Data.Linq; using System.Data.Linq.Mapping; using System.Windows; namespace TestLinq22 { public partial class Window1 : Window { public Window1() { InitializeComponent(); MainDB db = new MainDB(@"Data Source=App_Data\Main.sdf"); var customers = from c in db.Customers select new {c.FirstName, c.LastName}; TheListBox.ItemsSource = customers; } } [Database(Name = "MainDB")] public class MainDB : DataContext { public MainDB(string connection) : base(connection) { } public Table<Customers> Customers; } [Table(Name = "Customers")] public class Customers { [Column(DbType = "varchar(100)")] public string FirstName; [Column(DbType = "varchar(100)")] public string LastName; } }

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  • Dependency Injection and decoupling of software layers

    - by cs31415
    I am trying to implement Dependency Injection to make my app tester friendly. I have a rather basic doubt. Data layer uses SqlConnection object to connect to a SQL server database. SqlConnection object is a dependency for data access layer. In accordance with the laws of dependency injection, we must not new() dependent objects, but rather accept them through constructor arguments. Not wanting to upset the DI gods, I dutifully create a constructor in my DAL that takes in SqlConnection. Business layer calls DAL. Business layer must therefore, pass in SqlConnection. Presentation layer calls Business layer. Hence it too, must pass in SqlConnection to business layer. This is great for class isolation and testability. But didn't we just couple the UI and Business layers to a specific implementation of the data layer which happens to use a relational database? Why do the Presentation and Business layers need to know that the underlying data store is SQL? What if the app needs to support multiple data sources other than SQL server (such as XML files, Comma delimited files etc.) Furthermore, what if I add another object upon which my data layer is dependent on (say, a second database). Now, I have to modify the upper layers to pass in this new object. How can I avoid this merry-go-round and reap all the benefits of DI without the pain?

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  • Make case-sensitive SMB share case-insensitive

    - by fungs
    I am running a legacy XP app that I would like to move on a network share. It is very simple and works in theory but the server providing the share is based on Linux (cannot configure) and the software does not work correctly because it is programmed case-insensitively, it seems. After some research, network shares behave like the filesystem they use underneath. This is normal. Unfortunately I cannot fix the software myself. Is there any way to turn the case-sensitivity into case-insensitivity for a Windows network drive on the client side? I fould two approaches: First, something like icasefile (http://wnd.katei.fi/icasefile/) that wraps around the program and intercepts the file I/O. This is for UNIX only. Secondly, a proxy virtual file system (e. g. something using Dokan). Unfortunately I couldn't find any suitable fs, the only possibility would be to put a case-insensitive filesystem on an image file and put this on the share using for example lmdisk (http://www.ltr-data.se/opencode.html/#ImDisk). Do you have any better ideas?

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  • mySQL Efficiency Issue - How to find the right balance of normalization...?

    - by Foo
    I'm fairly new to working with relational databases, but have read a few books and know the basics of good design. I'm facing a design decision, and I'm not sure how to continue. Here's a very over simplified version of what I'm building: People can rate photos 1-5, and I need to display the average votes on the picture while keeping track of the individual votes. For example, 12 people voted 1, 7 people voted 2, etc. etc. The normalization freak of me initially designed the table structure like this: Table pictures id* | picture | userID | Table ratings id* | pictureID | userID | rating With all the foreign key constraints and everything set as they shoudl be. Every time someone rates a picture, I just insert a new record into ratings and be done with it. To find the average rating of a picture, I'd just run something like this: SELECT AVG(rating) FROM ratings WHERE pictureID = '5' GROUP by pictureID Having it setup this way lets me run my fancy statistics to. I can easily find who rated a certain picture a 3, and what not. Now I'm thinking if there's a crapload of ratings (which is very possible in what I'm really designing), finding the average will became very expensive and painful. Using a non-normalized version would seem to be more efficient. e.g.: Table picture id | picture | userID | ratingOne | ratingTwo | ratingThree | ratingFour | ratingFive To calculate the average, I'd just have to select a single row. It seems so much more efficient, but so much more uglier. Can someone point me in the right direction of what to do? My initial research shows that I have to "find the right balance", but how do I go about finding that balance? Any articles or additional reading information would be appreciated as well. Thanks.

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  • Reasons for & against a Database

    - by dbemerlin
    Hi, i had a discussion with a coworker about the architecture of a program i'm writing and i'd like some more opinions. The Situation: The Program should update at near-realtime (+/- 1 Minute). It involves the movement of objects on a coordinate system. There are some events that occur at regular intervals (i.e. creation of the objects). Movements can change at any time through user input. My solution was: Build a server that runs continously and stores the data internally. The server dumps a state-of-the-program at regular intervals to protect against powerfailures and/or crashes. He argued that the program requires a Database and i should use cronjobs to update the data. I can store movement information by storing startpoint, endpoint and speed and update the position in the cronjob (and calculate collisions with other objects there) by calculating direction and speed. His reasons: Requires more CPU & Memory because it runs constantly. Powerfailures/Crashes might destroy data. Databases are faster. My reasons against this are mostly: Not very precise as events can only occur at full minutes (wouldn't be that bad though). Requires (possibly costly) transformation of data on every run from relational data to objects. RDBMS are a general solution for a specialized problem so a specialized solution should be more efficient. Powerfailures (or other crashes) can leave the Data in an undefined state with only partially updated data unless (possibly costly) precautions (like transactions) are taken. What are your opinions about that? Which arguments can you add for any side?

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  • Real benefits of tcp TIME-WAIT and implications in production environment

    - by user64204
    SOME THEORY I've been doing some reading on tcp TIME-WAIT (here and there) and what I read is that it's a value set to 2 x MSL (maximum segment life) which keeps a connection in the "connection table" for a while to guarantee that, "before your allowed to create a connection with the same tuple, all the packets belonging to previous incarnations of that tuple will be dead". Since segments received (apart from SYN under specific circumstances) while a connection is either in TIME-WAIT or no longer existing would be discarded, why not close the connection right away? Q1: Is it because there is less processing involved in dealing with segments from old connections and less processing to create a new connection on the same tuple when in TIME-WAIT (i.e. are there performance benefits)? If the above explanation doesn't stand, the only reason I see the TIME-WAIT being useful would be if a client sends a SYN for a connection before it sends remaining segments for an old connection on the same tuple in which case the receiver would re-open the connection but then get bad segments and and would have to terminate it. Q2: Is this analysis correct? Q3: Are there other benefits to using TIME-WAIT? SOME PRACTICE I've been looking at the munin graphs on a production server that I administrate. Here is one: As you can see there are more connections in TIME-WAIT than ESTABLISHED, around twice as many most of the time, on some occasions four times as many. Q4: Does this have an impact on performance? Q5: If so, is it wise/recommended to reduce the TIME-WAIT value (and what to)? Q6: Is this ratio of TIME-WAIT / ESTABLISHED connections normal? Could this be related to malicious connection attempts?

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  • Model login constraints based on time

    - by DaDaDom
    Good morning, for an existing web application I need to implement "time based login constraints". It means that for each user, later maybe each group, I can define timeslots when they are (not) allowed to log in into the system. As all data for the application is stored in database tables, I need to somehow create a way to model this idea in that way. My first approach, I will try to explain it here: Create a tree of login constraints (called "timeslots") with the main "categories", like "workday", "weekend", "public holiday", etc. on the top level, which are in a "sorted" order (meaning "public holiday" has a higher priority than "weekday") for each top level node create subnodes, which have a finer timespan, like "monday", "tuesday", ... below that, create an "hour" level: 0, 1, 2, ..., 23. No further details are necessary. set every member to "allowed" by default For every member of the system create a 1:n relationship member:timeslots which defines constraints, e.g. a member A may have A:monday-forbidden and A:tuesday-forbidden Do a depth-first search at every login and check if the member has a constraint. Why a depth first search? Well, I thought that it may be that a member has the rules: A:monday->forbidden, A:monday-10->allowed, A:mondey-11->allowed So a login on monday at 12:30 would fail, but one at 10:30 succeed. For performance reasons I could break the relational database paradigm and set a flag for every entry in the member-to-timeslots-table which is set to true if the member has information set for "finer" timeslots, but that's a second step. Is this model in principle a good idea? Are there existing models? Thanks.

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  • DAS vs SAN storage for serving 2 to 4 nodes

    - by Luke404
    We currently have 4 Linux nodes with local storage, arranged in two active/passive pairs with storage mirrored using DRBD, running virtual machines (actually using Xen Hypervisor) for typical hosting workloads (mail, web, a couple VPS, etc.). We're approaching the (presumed) maximum IOPS of those servers, and we're planning to migrate to an external storage solution with two active nodes, with capacity for up to four active nodes. Since we're an all-Dell shop I've done some research and found the MD3200 / MD3200i products should be the ones we're looking for. We are pretty sure we won't be attaching more than 4 hosts on a single storage and I'm wondering if there is any clear advantage for one or the other. In theory I should be able to attach 4 SAS hosts to a single MD3200 (single links on a single controller MD3200, or dual redundant SAS links from each host to a dual-controller MD3200), or 4 iSCSI hosts to a single MD3200i (directly on its 4 GigE ports without any switch, again with dual links for the dual controller option). Both setups should let us implement live VM migration since all hosts can access all the LUNs at the same time, and also some shared filesystem like GFS2 or OCFS2. Also, both setups should allow full redundancy of the whole system (assuming dual controllers in the storage). One difference I can see is that the DAS solution is actually limited to 4 hosts while the iSCSI one should be able to grow to more hosts (adding two GigE switches to the mix). One point for the iSCSI solution is that it would allow us to start out with our current nodes and upgrade them at a later time (we can't add other SAS controllers, but they already have 4 GigE ports each). With the right (iSCSI|SAS) controllers I should be able to connect diskless nodes and boot them off the external storage which I think is a good thing (get rid of any local storage). On the other hand, I would have thought the SAS one to be cheaper but it seems like an MD3200 actually costs a little less than an MD3200i (?) (please note: I've used Dell gear in my examples since that's what we're looking for but I assume the same goes with other vendors) I would like to know if my assumptions above are correct, and if I'm missing any important difference between the two setups.

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  • How should I design my MYSQL table/s?

    - by yaya3
    I built a really basic php/mysql site for an architect that uses one 'projects' table. The website showcases various projects that he has worked on. Each project contained one piece of text and one series of images. Original projects table (create syntax): CREATE TABLE `projects` ( `project_id` int(11) NOT NULL auto_increment, `project_name` text, `project_text` text, `image_filenames` text, `image_folder` text, `project_pdf` text, PRIMARY KEY (`project_id`) ) ENGINE=MyISAM AUTO_INCREMENT=8 DEFAULT CHARSET=latin1; The client now requires the following, and I'm not sure how to handle the expansions in my DB. My suspicion is that I will need an additional table. Each project now have 'pages'. Pages either contain... One image One "piece" of text One image and one piece of text. Each page could use one of three layouts. As each project does not currently have more than 4 pieces of text (a very risky assumption) I have expanded the original table to accommodate everything. New projects table attempt (create syntax): CREATE TABLE `projects` ( `project_id` int(11) NOT NULL AUTO_INCREMENT, `project_name` text, `project_pdf` text, `project_image_folder` text, `project_img_filenames` text, `pages_with_text` text, `pages_without_img` text, `pages_layout_type` text, `pages_title` text, `page_text_a` text, `page_text_b` text, `page_text_c` text, `page_text_d` text, PRIMARY KEY (`project_id`) ) ENGINE=MyISAM AUTO_INCREMENT=8 DEFAULT CHARSET=latin1; In trying to learn more about MYSQL table structuring I have just read an intro to normalization and A Simple Guide to Five Normal Forms in Relational Database Theory. I'm going to keep reading! Thanks in advance

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  • openSSL tutorial not fully working - Can sign but cannot restore original file

    - by djechelon
    I'm writing, and testing, a little tutorial for my groupmates involved in an openSSL homework. We have a bunch of PDF files, I'm the CA and each one should send me a signed PDF for me to be verified. I've told them to do the following (and tried to do it by myself) Request and obtain a certificate (I'll skip this part) Create a MIME message with the PDF file in it makemime -c "text/pdf" -a "Content-Disposition: attachment; filename=”Elaborato.pdf" Elaborato.pdf > Elaborato.pdf.msg Sign with openSSL openssl smime -sign -in Elaborato.pdf.msg -out Elaborato.pdf.p7m -certfile ca.pem -certfile nomegruppo.crt -inkey nomegruppo.key -signer nomegruppo.crt Verify with openssl smime -verify -in Elaborato.pdf.p7m -out Elaborato-verified.msg -CAfile ca.pem -signer nomegruppo.crt Extract attachment with munpack Elaborato-verified.msg View with Acrobat Reader The problem is that even if I get a file that (from its binary content) resembles a PDF file my current Ubuntu PDF viewer doesn't read it. The XXXElaborato.pdf extracted by munpack is a little bit smaller than the original. What's the problem with this procedure? In theory, they should send me the signed S/MIME message and I should be able to read the PDF within it. Why can't I restore the original content of the PDF file?

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  • Is this a good job description? What title would you give this position?

    - by Zack Peterson
    Department: Information Technology Reports To: Chief Information Officer Purpose: Company's ________________ is specifically engaged in the development of World Wide Web applications and distributed network applications. This person is concerned with all facets of the software development process and specializes in software product management. He or she contributes to projects in an application architect role and also performs individual programming tasks. Essential Duties & Responsibilities: This person is involved in all aspects of the software development process such as: Participation in software product definitions, including requirements analysis and specification Development and refinement of simulations or prototypes to confirm requirements Feasibility and cost-benefit analysis, including the choice of architecture and framework Application and database design Implementation (e.g. installation, configuration, customization, integration, data migration) Authoring of documentation needed by users and partners Testing, including defining/supporting acceptance testing and gathering feedback from pre-release testers Participation in software release and post-release activities, including support for product launch evangelism (e.g. developing demonstrations and/or samples) and subsequent product build/release cycles Maintenance Qualifications: Bachelor's degree in computer science or software engineering Several years of professional programming experience Proficiency in the general technology of the World Wide Web: Hypertext Transfer Protocol (HTTP) Hypertext Markup Language (HTML) JavaScript Cascading Style Sheets (CSS) Proficiency in the following principles, practices, and techniques: Accessibility Interoperability Usability Security (especially prevention of SQL injection and cross-site scripting (XSS) attacks) Object-oriented programming (e.g. encapsulation, inheritance, modularity, polymorphism, etc.) Relational database design (e.g. normalization, orthogonality) Search engine optimization (SEO) Asynchronous JavaScript and XML (AJAX) Proficiency in the following specific technologies utilized by Company: C# or Visual Basic .NET ADO.NET (including ADO.NET Entity Framework) ASP.NET (including ASP.NET MVC Framework) Windows Presentation Foundation (WPF) Language Integrated Query (LINQ) Extensible Application Markup Language (XAML) jQuery Transact-SQL (T-SQL) Microsoft Visual Studio Microsoft Internet Information Services (IIS) Microsoft SQL Server Adobe Photoshop

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  • Mouse receiver stopped working after pairing mouse to an unifying receiver

    - by mp19uy
    I bought this mouse, logitech m510, which came with a nano receiver (no-unifying). Yes I know, the mouse is supposed to come with a unifying receiver but I bought it knowing that it won't come on it's original package and it will come with a no-unifying receiver. When I received it, everything worked ok but, after connecting the mouse to another computer using an unifying receiver (that also worked ok, btw), then, when I tried to connect back the mouse to my computer using the no-unifying receiver, I couldn't connect it. I tried everything from removing the batteries and reinstalling the drivers to restarting the computer and trying in different computers, but I couldn't connect them. What I think it happened, is that in fact if you check the documentation of the logitech m510 it says that it works with unifying receivers only, and even more, there is the following article explaining it: http://logitech-en-amr.custhelp.com/app/answers/detail/a_id/18001/~/using-my-m510-with-a-different-usb-receiver So my theory is that the problem was connecting it to a unifying receiver, and now, isn't recognize by another receiver. The receiver (the no-unifying one) itself is recognized by windows, and if I connect the mouse using a unifying receiver, it works. I would like to know if there is any know solution for this or if I can try something else to see if I can solve this.

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  • Vertical Image Border Changes Alignment when Screen is not maximized

    - by Randy
    I have some pretty straightforward HTML code with a few tables to organize various items of text or images. All works fine except that I need to place a vertical border on both the left and right sides of the screen. I am able to do this with a 2x2 pixel image that I stretch out. When the user has their screen maximized, everything looks great. But when the user hits "Restore Down", then the borders stay in place, but the tables get shoved down so that they start below where the borders end, which is off screen. in other words, the relational alignment between the borders and the tables gets all screwed up. Does anybody know how to make this alignment stay consistent on a restore down? I'm pretty much a newbie with html and asp, so speak slowly. If there is a better method to accomplish this, I'm all ears. Thanks. Here is the relevant section of code: <%@ Master Language="C#" AutoEventWireup="true" CodeFile="MasterPage.master.cs" Inherits="MasterPage" % <form id="form1" runat="server"> <asp:Image ID="LeftBorder" src="../Images/Border_Blue.jpg" runat="server" WIDTH="15" HEIGHT="1000" BORDER="0" alt="Image Missing" align="left"/> <asp:Image ID="RightBorder" src="../Images/Border_Blue.jpg" runat="server" WIDTH="15" HEIGHT="1000" BORDER="0" alt="Image Missing" align="right" /> <table id="BannerTable" style="height: 100px"> <tr> <td width="934px"> <img src="../Images/Header.jpg" alt="Image Missing" id="ImgBanner" align="left"/></td> </tr> </table>

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  • How to restrict text search to a certain subset of the database ?

    - by Nikhil Garg
    I have a large central database of around 1 million heavy records. In my app, for every user I would have a subset of rows from central table, which would be very small (probably 100 records each).When a particular user has logged in , I would want to search on this data set only. Example: Say I have a central database of all cars in the world. I have a user profile for General Motors(GM) , Ferrari etc. When GM is logged in I just want to search(a full text search and not fire a sql query) for those cars which are manufactured by GM. Also GM may launch/withdraw a model in which case central db would be updated & so would be rowset associated with GM. In case of acquisitions, db of certain profiles may change without launch/removal of new car. So central db wont change then , but rowsets may. Whats the best way to implement such a design ? These smaller row sets would need to be dynamic depending on user activities. We are on Rails 2.3.5 and use thinking_sphinx as the connector and Sphinx/MySQL for search and relational associations.

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  • Schema-less design guidelines for Google App Engine Datastore and other NoSQL DBs

    - by jamesaharvey
    Coming from a relational database background, as I'm sure many others are, I'm looking for some solid guidelines for setting up / designing my datastore on Google App Engine. Are there any good rules of thumb people have for setting up these kinds of schema-less data stores? I understand some of the basics such as denormalizing since you can't do joins, but I was wondering what other recommendations people had. The particular simple example I am working with concerns storing searches and their results. For example I have the following 2 models defined in my Google App Engine app using Python: class Search(db.Model): who = db.StringProperty() what = db.StringProperty() where = db.StringProperty() createDate = db.DateTimeProperty(auto_now_add=True) class SearchResult(db.Model): title = db.StringProperty() content = db.StringProperty() who = db.StringProperty() what = db.StringProperty() where = db.StringProperty() createDate = db.DateTimeProperty(auto_now_add=True) I'm duplicating a bunch of properties between the models for the sake of denormalization since I can't join Search and SearchResult together. Does this make sense? Or should I store a search ID in the SearchResult model and effectively 'join' the 2 models in code when I retrieve them from the datastore? Please keep in mind that this is a simple example. Both models will have a lot more properties and the way I'm approaching this right now, I would put any property I put in the Search model in the SearchResult model as well.

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  • Is VGA port hot-pluggable?

    - by Martin Bøgelund
    In meetings, I often see people detaching the VGA connector from one running laptop and connecting it to another, while the projector is still on. Is this 100% risk free, and OK by design of the VGA standard? If there's a risk involved in hot-plugging VGA, can it be removed by turning off or suspending either laptop, display, or both? I see this being done all the time without causing disaster, so clearly I'm not interested in answers stating "we do it all the time, so it should be OK!". I want to know if there's a risk - real or in theory - that something breaks when doing this. EDIT: I did an internet search on the topic, and I never found a clear statement as to why it is safe or unsafe to hot swap VGA devices. The typical form is a forum question asking basically the same question as I did, and the following types of statements Yes it's hot swappable! I do it all the time! It involves some kind of risk, so don't do it! You're some kind of moron if you think there's a risk, so just do it! But no explanation as to why it safe or not... Joe Taylors answer below contains a link to a forum post and answers that basically give me the same statements as mentioned above. But again, no good explanation why. So I looked for an actual manual for a projector, and found "Lenovo C500 Projector User’s Guide". It states on page 3-1: Connecting devices Computers and video devices can be connected to the projector at the same time. Check the user’s manual of the connecting device to confirm that it has the appropriate output connector. [image] Attention: As a safety precaution, disconnect all power to the projector and devices before making connections. But again, no good explanation.

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  • When is a good time to start thinking about scaling?

    - by Slokun
    I've been designing a site over the past couple days, and been doing some research into different aspects of scaling a site horizontally. If things go as planned, in a few months (years?) I know I'd need to worry about scaling the site up and out, since the resources it would end up consuming would be huge. So, this got me to thinking, when is the best time to start thinking about, and designing for, scalability? If you start too early on, you could easily over complicate your design, and make it impossible to actually build. You could also get too caught up in the details, the architecture, whatever, and wind up getting nothing done. Also, if you do get it working, but the site never takes off, you may have wasted a good chunk of extra effort. On the other hand, you could be saving yourself a ton of effort down the road. Designing it from the ground up to be big would make it much easier later on to let it grow big, with very little rewriting going on. I know for what I'm working on, I've decided to make at least a few choices now on the side of scaling, but I'm not going to do a complete change of thinking to get it to scale completely. Notably, I've redesigned my database from a conventional relational design to one similar to what was suggested on the Reddit site linked below, and I'm going to give memcache a try. So, the basic question, when is a good time to start thinking or worrying about scaling, and what are some good designs, tips, etc. for when doing so? A couple of things I've been reading, for those who are interested: http://www.codinghorror.com/blog/2009/06/scaling-up-vs-scaling-out-hidden-costs.html http://highscalability.com/blog/2010/5/17/7-lessons-learned-while-building-reddit-to-270-million-page.html http://developer.yahoo.com/performance/rules.html

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  • Why is my apache2, mod_fcgid, php configuration causing 100% cpu usage?

    - by Scott Lundgren
    Page load makes a quick initial connection, then hangs about 10 seconds before the page renders. When the server load goes up I start watching top & I see that both CPUs get pegged at times to 100% by between 4-8 processes of php-cgi. My theory is that since I never see RAM usage never go above 50%, that apache is able to handle the requests coming in, but is queueing them for PHP to process. What is wrong with my mod_fcgid/php configuration ? RHEL 5.4 2 Xeon E5420s @ 2.50 Ghz 4 Gb RAM Apache 2.2.3 Timeout 30 KeepAlive On MaxKeepAliveRequests 0 KeepAliveTimeout 5 <IfModule worker.c> StartServers 2 MaxClients 300 MinSpareThreads 25 MaxSpareThreads 75 ThreadsPerChild 25 MaxRequestsPerChild 0 </IfModule> mod_fcgid 2.2.10 LoadModule fcgid_module modules/mod_fcgid.so <IfModule !mod_fastcgi.c> AddHandler fcgid-script fcg fcgi fpl php </IfModule> SocketPath run/mod_fcgid SharememPath run/mod_fcgid/fcgid_shm DefaultInitEnv PHPRC "/etc/" FCGIWrapper /usr/bin/php-cgi .php MaxRequestsPerProcess 1500 MaxProcessCount 20 IPCCommTimeout 240 IdleTimeout 240 APC 3.0.19 extension = apc.so apc.enabled=1 apc.shm_segments=1 apc.optimization=0 apc.shm_size=32 apc.ttl=7200 APC cache is 43% used with a 99% hit rate

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  • finding ALL cycles in a huge sparse matrix

    - by Andy
    Hi there, First of all I'm quite a Java beginner, so I'm not sure if this is even possible! Basically I have a huge (3+million) data source of relational data (i.e. A is friends with B+C+D, B is friends with D+G+Z (but not A - i.e. unmutual) etc.) and I want to find every cycle within this (not necessarily connected) directed graph. I've found this thread (http://stackoverflow.com/questions/546655/finding-all-cycles-in-graph/549402#549402) which has pointed me to Donald Johnson's (elementary) cycle-finding algorithm which, superficially at least, looks like it'll do what I'm after (I'm going to try when I'm back at work on Tuesday - thought it wouldn't hurt to ask in the meanwhile!). I had a quick scan through the code of the Java implementation of Johnson's algorithm (in that thread) and it looks like a matrix of relations is the first step, so I guess my questions are: a) Is Java capable of handling a 3+million*3+million matrix? (was planning on representing A-friends-with-B by a binary sparse matrix) b) Do I need to find every connected subgraph as my first problem, or will cycle-finding algorithms handle disjoint data? c) Is this actually an appropriate solution for the problem? My understanding of "elementary" cycles is that in the graph below, rather than picking out A-B-C-D-E-F it'll pick out A-B-F, B-C-D etc. but that's not the end of the world given the task. E / \ D---F / \ / \ C---B---A d) If necessary, I can simplify the problem by enforcing mutuality in relations - i.e. A-friends-with-B <== B-friends-with-A, and if really necessary I can maybe cut down the data size, but realistically it is always going to be around the 1mil mark. z) Is this a P or NP task?! Am I biting off more than I can chew? Thanks all, any help appreciated! Andy

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  • Recommend me an architecture for this Facebook application

    - by andybaird
    Firstly, this question is subjective. There is not a right answer for this question and it really depends on what works for you. I'm hoping to use this thread as a breeding ground for ideas. I hope this is acceptable in this medium. I'm working on building a Facebook app that will be replacing an already popular app that gets ~50k hits a day. The original app is using a very typical LAMP setup with help from some Zend libraries for database layer extraction. For the most part the app worked well, except to solve a lot of issues I ended up fragmenting tables to speed things up. As a result, I couldn't do a lot of things with the app that I wanted to (namely any processing using aggregate data that needed to be returned quickly) So I'm starting to design plans for the next version of this application, and I have a whole bunch of new and cool features that I know would choke my current setup. I'm looking for technological recommendations of data storage methods that scale well. The database does not necessarily need to be relational, simple key/value storage would suffice (although at present time I know little to nothing about KV stores) What's your recommendation? How would you tackle this? I'd like to take a completely free approach to this -- although I am most familiar and comfortable using PHP, I want to leave all technical options open.

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  • Sparse (Pseudo) Infinite Grid Data Structure for Web Game

    - by Ming
    I'm considering trying to make a game that takes place on an essentially infinite grid. The grid is very sparse. Certain small regions of relatively high density. Relatively few isolated nonempty cells. The amount of the grid in use is too large to implement naively but probably smallish by "big data" standards (I'm not trying to map the Internet or anything like that) This needs to be easy to persist. Here are the operations I may want to perform (reasonably efficiently) on this grid: Ask for some small rectangular region of cells and all their contents (a player's current neighborhood) Set individual cells or blit small regions (the player is making a move) Ask for the rough shape or outline/silhouette of some larger rectangular regions (a world map or region preview) Find some regions with approximately a given density (player spawning location) Approximate shortest path through gaps of at most some small constant empty spaces per hop (it's OK to be a bad approximation often, but not OK to keep heading the wrong direction searching) Approximate convex hull for a region Here's the catch: I want to do this in a web app. That is, I would prefer to use existing data storage (perhaps in the form of a relational database) and relatively little external dependency (preferably avoiding the need for a persistent process). Guys, what advice can you give me on actually implementing this? How would you do this if the web-app restrictions weren't in place? How would you modify that if they were? Thanks a lot, everyone!

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  • Apache runs in console but not as a service?

    - by danspants
    I have an apache 2.2 server running Django. We have a network drive T: which we need constant access to within our Django app. When running Apache as a service, we cannot access this drive, as far as any django code is concerned the drive does not exist. If I add... <Directory "t:/"> Options Indexes FollowSymLinks MultiViews AllowOverride None Order allow,deny allow from all </Directory> to the httpd.conf file the service no longer runs, but I can start apache as a console and it works fine, Django can find the network drive and all is well. Why is there a difference between the console and the service? Should there be a difference? I have the service using my own log on so in theory it should have the same access as I do. I'm keen to keep it running as a service as it's far less obtrusive when I'm working on the server (unless there's a way to hide the console?). Any help would be most appreciated.

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  • retrieving object information with Doctrine

    - by ajsie
    i want to fetch information from the database using objects. i really like this approach cause this is more OOP: $user = Doctrine_Core::getTable('User')->find(1); echo $user->Email['address']; echo $user->Phonenumbers[0]->phonenumber; rather than: $q = Doctrine_Query::create() ->from('User u') ->leftJoin('u.Email e') ->leftJoin('u.Phonenumbers p') ->where('u.id = ?', 1); $user = $q->fetchOne(); echo $user->Email['address']; echo $user->Phonenumbers[0]['phonenumber']; the problem is that the first one uses 3 queries (3 different tables), while the second one uses only 1 (and is therefore recommended technique). but i feel that it destroys the object oriented design. cause ORM is meant to give us an OOP approach so that we could focus on objects and not the relational database. but now they want us to go back to use SQL like pattern. there isn't a way to get information form multiple tables not using DQL? the above examples are taken from the documentation: doctrine

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  • IIS / Virtual Directory authentication.

    - by Chris L
    I have an IIS(v6)/Windows 2003/.Net 3.5(app code, libraries etc.) server hosting a website at www.mywebsite.com mapped to E:\Inetpub\wwwroot\mywebsite, we also have a virtual directory (VirtDir) mapped out to E:\Inetpub\wwwroot\mywebsite\files (although in theory this could be in a different directory or a separate machine) where we store a customer's files(a bunch of .pdf & .xls). Currently to access a file you can enter into the url something like: www.mywebsite.com/VirtDir/Customer/myFile.pdf and get access to the file. The problem is the user doesn't have to log into www.mywebsite.com to get access to the file, we would prefer them to log in first. We would like the user to login via the mywebsite and if valid, let them download files from the virtual directory. The www.mywebsite.com and VirtDir are separate sites on the same farm. Allow Anon Access, and Integrated Windows Authentication both enabled. I'm more of a developer and less of a Sys Admin, but hopefully I'm in the right spot, any help would be appreciated.

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  • Outlook Signature Broken in Entourage

    - by Eric J.
    Some of our company uses Windows with Outlook 2010, and the rest use Mac with Entourage. When our standard signature line is included in an email that goes to Entourage, the result does not display correctly. It appears that Entourage is mangling the HTML. My working theory is that Entourage encounters inline CSS styles it does not know about and stops processing styles, but I'm really not sure. Question: How can I enter a signature into Outlook 2010 that will render correctly in Entourage? For example, can I specify somehow the exact HTML to use? Here's an example of how the HTML is being changed. Original on Outlook, as received by another Outlook client: <span style='font-size:9.0pt;font-family:"Century Gothic","sans-serif"; color:#1785C5'>My Company<br> </span></b><span class=apple-style-span><span style='font-size:9.0pt; font-family:"Century Gothic","sans-serif";color:#666666'>123 Main St.</span></span><span class=apple-style-span><span style='font-size:9.0pt;font-family:"Century Gothic","sans-serif"; color:#AFAFAF'>&nbsp;</span></span><span class=apple-style-span><span style='font-size:9.0pt;font-family:"Century Gothic","sans-serif";color:#666666'>Suite 100</span></span> Note the use of spans, color #1785C5 and color #666666. Same original email, as displayed in an Entourage client: <span style='font-size:9.0pt;font-family:"Century Gothic","sans-serif"; mso-fareast-font-family:"Times New Roman"'><br> <span style='color:#656565'>My Company<br> 123 Main St Suite 100<br> </span> Note the use of br tags rather than spans, and the color #656565.

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