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  • Most common parts of a SELECT SQL query?

    - by jnrbsn
    I'm writing a function that generates a SELECT SQL query. (I'm not looking for a tool that already does this.) My function currently takes the following arguments which correspond to different parts of the SELECT query (the base table name is already known): where order fields joins group limit All of these arguments will be optional so that the function generates something like this by default: SELECT * FROM `table_name` I want to order the arguments so that the most often used parts of a SELECT query are first. That way the average call to the function will use as few of the arguments as possible rather than passing a null value or something like that to skip an argument. For example, if someone wanted to use the 1st and 3rd arguments but not the rest, they might have to pass a null value as the 2nd argument in order to skip it. So, for general purpose use, how should I order the arguments? Edit: To be more precise, out of the query parts I listed above, what is the order from most used to least used? Also, I'm not looking for solutions that allow me to not have to specify the order. Edit #2: The "fields" argument will default to "*" (i.e all fields/columns).

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  • What and all the areas of a Linux a PHP developer should know about? (Like just commands of it or something advanced)

    - by droidsites
    I've developed a website using PHP but I implemented it on Windows OS and hosted it on Windows server. I just searched the PHP job market to know the on-going technology requirement and to keep my knowledge up-to-date accordingly with the job market. I see more are asking for LAMP stack. I understand the sort of skills required for a developer in PHP and MySQL. But coming to the Linux and Apache what kind of the skills exactly companies expect from a developer? On what should I be focusing in case of Linux, Apache whilst developing my website using these LAMP stack? I am going to develop a new website and want it to be using LAMP. But I want to know what difference it makes? Why LAMP stack got more demand in the job market compared to WAMP ? Edit: Sorry I thought my question is creating confusion ... so I put my question in different words as What and all the areas of a Linux a PHP developer should know about? (Like just commands of it or something advanced) Note: I am Linux newbie

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  • Quick Fix for GlassFish/MySQL NoPasswordCredential Found

    - by MarkH
    Just the other day, I stood up a GlassFish 3.1.2 server in preparation for a new web app we've developed. Since we're using MySQL as the back-end database, I configured it for MySQL (driver) and created the requisite JDBC resource and supporting connection pool. Pinging the finished pool returned a success, and all was well. Until we fired up the app, that is -- in this case, after a weekend. Funny how things seem to break when you leave them alone for a couple of days. :-) Strangely, the error indicated "No PasswordCredential found". Time to re-check that pool. All the usual properties and values were there (URL, driverClass, serverName, databaseName, portNumber, user, password) and were populated correctly. Yes, the password field, too. And it had pinged successfully. So why the problem? A bit of searching online produced enough relevant material to offer promise. I didn't take notes as I was investigating the cause (note to self), but here were the general steps I took to resolve the issue: First, per some guidance I had found, I tried resetting the password value to nothing (using () for a value). Of course, this didn't fix anything; the database account requires a password. And when I tried to put the value back, GlassFish politely refused. Hmm. I'd seen that some folks created a new pool to replace the "broken" one, and while that did work for them, it seemed to simply side-step the issue. So I deleted the password property - which GlassFish allowed me to do - and restarted the domain. Once I was back in, I re-added the password property and its value, saved it, and pinged...success! But now to the app for the litmus test. The web app worked, and everything and everyone was now happy. Not bad for a Monday.  :-D Hope this helps, Mark

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  • Computer Science graduate. Master or full-time job? [closed]

    - by Alex
    Possible Duplicate: Is a Master's worth it? I have just gotten my Bachelor's Degree in Computer Science and I have to make choice. Whether to continue with my full-time job I just got or put the job slightly in the background and concentrate on getting a Master's degree. I am currently working as an embedded C developer in a small company. The cool thing is that, because the team is quite small, my engineering ideas really play a part in the final product. Not to mention that I get to work on very different areas of embedded programming: device drivers and development of a Real Time OS. I am very enthusiastic about my job and what I do. On the other hand, in my country there isn't really a master's degree that focuses on embedded development so my gain from getting this degree will mainly in the field of general computer science knowledge. That being said, is it worth giving up all my spare time which I now use to study different areas of embedded devices and work mainly to get a degree rather than pure knowledge and experience in the field I want to work in?

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  • Take a Tour of the Future

    - by Tom Caldecott-Oracle
    Visit Our HQ Usability Lab During Oracle OpenWorld 2014 You want to look behind the scenes at the Oracle Applications User Experience Usability Lab on the campus of our headquarters. No problem. You’re invited to join an exclusive tour. When? Thursday, October 2 or Friday, October 3. Where? Redwood Shores, Calif.  And what will you see on the tour? The future—how we test future product designs and the advanced technology we use to do that. You’ll also view early demos of upcoming enterprise software designs for tables and mobile phones.  We’ll provide round-trip transportation, with the pickup and drop-off point being the InterContinental San Francisco.  Space is limited, so reserve your spot now. Want to know more about the tour and other Oracle Applications User Experience activities at Oracle OpenWorld? Visit UsableApps. Welcome to the future.

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  • 25 years old and considering a career change...possible? practical?

    - by mq330
    Hi all, I'm new to this site and new to programming as well. I've spent some time going through an intro cs book that uses python as the language of choice. I find the exercises interesting and engaging and I generally have had a favorable experience programming so far. I've gone through some of the basics with python like writing simple programs, basics of GUIs, manipulating strings, lists, defining functions, etc. And I've always loved technology. Although I've never done any real hardcore programming yet, I was inclined to building websites from a very young age but I never really developed my skills. Now, the thing is I'm 25, I have my bacholors in environmental studies and two masters degrees in urban planning and landscape architecture respectively. I know, it would be quite a departure to pursue a career in programming at this point. Currently, I'm working as a geographic information systems intern. I've taken some GIS classes and have a lot of experience with making maps, doing spatial analysis etc. So what I'm thinking is maybe I can learn some solid programming skills and apply these skills in the field of GIS. From what I've seen, .net languages are the norm in this arena. Could you perhaps provide some guidance to me in terms of what languages I should focus on or courses I should take at this point? What about for building web mapping applications? Also, I was thinking about getting a certificate in programming from a university extension program. Do you think it would be worth it? And furthermore, do you think potential employers would be interested in hiring someone like me (once I get a couple of languages down pretty well) as an intern or in an entry level position? I'll be living in the bay area so I feel that there should be decent opportunities even though I don't have a b.s. in cs.

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  • How do I prevent software packages from being downloaded until I know it's safe?

    - by Dave M G
    Recently, an update that caused a problem with Gnome session caused me to lose a day's work. The solution was to rollback some packages to a previous version. The update manager is now telling me that my old packages should be updated: ... but I don't want to do that until I know that whatever bug or problem the latest version has is resolved. I understand that with any upgrade that there is a risk of instability. However, in the 8 years or more that I've been on Ubuntu, using the latest releases has been stable enough and with the benefit of the latest features and security. So, I'm not looking for general advice on how to handle upgrades. What I'm saying is that in this one particular instance, the bug introduced by these upgrades is severe and time wasting. But, as an end user, when I encounter a problem like this, I have no idea how to address a specific concern about a specific package. I don't, for example, know which of these packages is the problem, and I can't take time from my work schedule to be experimenting with each package. So, my question is: How do I find out who exactly is responsible for these, or any, packages so that I can contact them and let them know about the problem? How do I freeze these packages only, but allow other upgrades to happen? ubuntu-session gnome-session-common gnome-session-bin gnome-session

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  • Where to ask a question about startups?

    - by Wolfpack'08
    I've got some questions about how to better run my web application development business, which has only been running for a little more than two years. It's still in its early phases, as I consider the first five years the 'early years'. Being inexperienced with business in general, I always have a lot of questions as to whether I am making the right decisions (for example, I often worry about my hiring practices, and I often worry that I may have priced new products wrongly). Is there a good site on the Stack Exchange to ask questions about things like this (for example, this site, the Project Management site, the Salesforce site, or perhaps the Personal Finance site)? I'm combing through questions and answers on each of these sites, now, and I can see questions that mimic my own. Nothing precisely the same, but things that are similar on all sites. Apart from just reading through previously asked questions, what is a good way to get a sense of whether or not my question fits on a site in the exchange? If you recommend going out of the exchange, please also let me know.

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  • Is there any CSS selector to reach an element outside of the current container?

    - by acidrums4
    (And excuse me for my bad english, for starters...) Sorry if this is a noob question, but I really don't know if the following is possible. I'm doing a html5 portfolio. I'm following a tuto from codrops to visually filter works with only css3 (http://tympanus.net/codrops/2012/01/09/filter-functionality-with-css3/). There, user can select which category want to see with some <input type="radio">'s. But those selectors are under the same container (a <section>) and give visibility for the elements via CSS using a general sibling combinator (~). So in that example, the CSS code goes like this: .ff-container input.ff-selector-type-all:checked ~ label.ff-label-type-all, .ff-container input.ff-selector-type-1:checked ~ label.ff-label-type-1, .ff-container input.ff-selector-type-2:checked ~ label.ff-label-type-2, .ff-container input.ff-selector-type-3:checked ~ label.ff-label-type-3{ background: linear-gradient(top, #646d93 0%,#7c87ad 100%); color: #424d71; text-shadow: 0px 1px 1px rgba(255,255,255,0.3); box-shadow: 0px 0px 0px 1px #40496e, 0 1px 2px rgba(0,0,0,0.1) inset; } The thing is I want to put those <input type="radio">'s on the <head> section of my portfolio, but obviously the ~ selector won't work there. So my question is that is there any selector, hack or something that can do that? Something like .ff-container input.ff-selector-type-all:checked $ header > label.ff-label-type-all { awesomeness:100%; } I really don't want to use Javascript/Jquery for that... Thank you so much in advance!

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  • Quiz Master at Beyond Relational

    - by Vincent Maverick Durano
    Last month a friend of mine invited me to join BeyondRelational.com and asked me to nominate myself as a .NET Quiz Master. In order to qualify I must submit an interesting question related to .NET and their .NET team will review the information and will select 31 quiz masters for the .NET quiz category. This seems insteresting to me so I go ahead and submit one entry. Luckily I was selected as one of the 31 Quiz Masters in the .NET category. I hope to be able to keep up the good work there for years to come. Big Thanks to Jacob Sebastian and his Team! And oh.. I didn't get a changce to blog about this last week but just to let you guys know that the .NET General Quiz just started last january 1st 2011. The quiz will be a series of 31 questions, managed by 31 .NET quiz masters. Each quiz master will ask one question and will moderate the discussion and answers and finally will identify the winner of each quiz. Each answer that is correct will get a certain score ranging from 1 to 10 where 10 is the highest. The scores of all 31 questions will be added up to identify the final winner. So what are you waiting for? Sign-up and register now and get a changce to win some exciting prizes! Technorati Tags: Community

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  • Making efficeint voxel engines using "chunks"

    - by Wardy
    Concept I'm currently looking in to how voxel engines work with a view to possibly making one myself. I see a lot of stuff like this ... https://sites.google.com/site/letsmakeavoxelengine/home/chunks ... which talks about how to go about reducing the draw calls. What I can't seem to understand is how it actually saves draw call counts on the basis of the logic being something like this ... Without chunks foreach voxel in myvoxels DrawIfVisible() With Chunks foreach chunk in mychunks DrawIfVisible() which then does ... foreach voxel in myvoxels DrawIfVisible() So surely you saved nothing ?!?! You still make a draw call for each visible voxel do you not? A visible voxel needs a draw call in either scenario. The only real saving I can see is that the logic that evaluates a chunk will be able to determine if a large number of voxels are visible or not effectively saving a bit of "is this chunk visible" cpu time. But it's the draw calls that interest me ... The fewer of those, the faster the application. EDIT: In case it makes any difference I will probably be using XNA (DX not OpenGL) for my engine so don't consider my choice of example in the link above my choice of technology. But this question is such that I doubt it would matter.

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  • Why is my USB data transfer so slow?

    - by Dave M G
    Whenever I do any kind of file transfer using USB, whether to a USB stick, or with my Android phone, or anything else, it is ridiculously slow. It says 59.8 KB/sec, which would be an awesome speed if this were 1991 and I was using a modem to dial up to my local BBS. Surely USB technology is better than that...? 37 seconds to move less data than the equivelent of 1 MP3 file? Also, regardless of what it says about speed and time, the reality is much, much slower. I routinely see it say something like "37 seconds left" and have to wait for minutes. Sometimes, if I want to move large amounts of files, it can say it will take 8 hours or more. Is this normal? My computer may not be the most awesome on the market, and about a year old, but it's an i5 with 4GB RAM and modern components, so surely this isn't the hardware's fault. What can I do to get better USB data transfer performance? Also, I did look at this question, but my newbie eyes don't see anything that look like an actual solution, just a lot of discussion about what transfer rates could or should be. Update: As requested in the comments, I've generated a whole bunch of output from the command line, and put it on Ubuntu Pastebin. Please see it here.

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  • Object desing problem for simple school application

    - by Aragornx
    I want to create simple school application that provides grades,notes,presence,etc. for students,teachers and parents. I'm trying to design objects for this problem and I'm little bit confused - because I'm not very experienced in class designing. Some of my present objects are : class PersonalData() { private String name; private String surename; private Calendar dateOfBirth; [...] } class Person { private PersonalData personalData; } class User extends Person { private String login; private char[] password; } class Student extends Person { private ArrayList<Counselor> counselors = new ArrayList<>(); } class Counselor extends Person { private ArrayList<Student> children = new ArrayList<>(); } class Teacher extends Person { private ArrayList<ChoolClass> schoolClasses = new ArrayList<>(); private ArrayList<Subject> subjects = new ArrayList<>(); } This is of course a general idea. But I'm sure it's not the best way. For example I want that one person could be a Teacher and also a Parent(Counselor) and present approach makes me to have two Person objects. I want that user after successful logging in get all roles that it has (Student or Teacher or (Teacher & Parent) ). I think I should make and use some interfaces but I'm not sure how to do this right. Maybe like this: interface Role { } interface TeacherRole implements Role { void addGrade( Student student, Grade grade, [...] ); } class Teacher implements TeacherRole { private Person person; [...] } class User extends Person{ ArrayList<Role> roles = new ArrayList<>(); } Please if anyone could help me to make this right or maybe just point me to some literature/article that covers practical objects design.

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  • Oracle Fusion Middleware 11gR1 ?FAQ??

    - by Hiroyuki Yoshino
    ??????FAQ????????????????? Oracle Technology Network (OTN)???????·??????·???????? Q. "Generic", "x86", "x86-64", ????????????????????????????????? A. ?????????????? Generic ????????·???????????????? 32????64???·??????????JDK/JVM????????? JDK/JVM???????????????????? x86 Supported System Configurations??????????????????????????????32???·???????????? x86-64 Supported System Configurations??????????????????????????????64???·???????????? ?????????? ("SPARC"??) Supported System Configurations????????????????????????????????????WebCenter for AIX?Portal, Forms, Reports and Discoverer for HP-UX PA-RISC???????? Q. SOA 11gR1 (11.1.1.1.0)??????????? 11gR1 (11.1.1.1.0)????????????????? A. ??????·????11gR1???????????????????????????????Oracle Support???????????????? Q. Oracle Fusion Middleware 11gR1???????????????????? A. Oracle Fusion Middleware 11gR1 ????????????????? Supported System Configurations?????????????? Q. Oracle Fusion Middleware 11gR1?????????????????????????????? A. Oracle Fusion Middleware?Oracle?????? Oracle Virtual Machine ????????????Oracle??????????????????????????????????????????????????? ???????? 

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  • Who wants to keep developing?

    - by wcm
    I'm a bit older than most of my peers, having come into programming in my mid 30's. The thing is, I love what I do. Most of my project managers and bosses are my age or younger. I'm really OK with that. I, however, have no desire to climb the company ladder. While I regularly take on the responsibility of making sure that projects get done and my peers often look to me for programming and architectural guidance, I just like writing code and want to keep doing it for as long as possible. Honestly, my only real goal is grow into being a crusty old tech lead until I retire. IF I retire. I would so much rather learn the latest and greatest new technology than PMP my resume. Are there others out there who feel like this because I often feel rather alone in my pathology? EDIT Something I didn't make clear is that I really like helping and mentoring other developers. It makes me feel good and useful and (to be brutaly honest) important.

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  • Classes as a compilation unit

    - by Yannbane
    If "compilation unit" is unclear, please refer to this. However, what I mean by it will be clear from the context. Edit: my language allows for multiple inheritance, unlike Java. I've started designing+developing my own programming language for educational, recreational, and potentially useful purposes. At first, I've decided to base it off Java. This implied that I would have all the code be written inside classes, and that code compiles to classes, which are loaded by the VM. However, I've excluded features such as interfaces and abstract classes, because I found no need for them. They seemed to be enforcing a paradigm, and I'd like my language not to do that. I wanted to keep the classes as the compilation unit though, because it seemed convenient to implement, familiar, and I just liked the idea. Then I noticed that I'm basically left with a glorified module system, where classes could be used either as "namespaces", providing constants and functions using the static directive, or as templates for objects that need to be instantiated ("actual" purpose of classes in other languages). Now I'm left wondering: what are the benefits of having classes as compilation units? (Also, any general commentary on my design would be much appreciated.)

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  • Need ideas on how to give my levels structure

    - by akuritsu
    I am making an iOS game for a project at school. It is going to be a tiny bit like Fruit Ninja, as in it will have different things on the screen, and when you hit them, they die, and you get points. The trouble is that unlike Fruit Ninja, my game will have different types of sprites, all doing different things (moving different places, doing different things, etc). The one thing that is bad about having all of these sprites that do different things is that it is hard for them to look neat on the screen all together. I was planning on having a couple of different gamemodes: Time Trial You have 120 seconds to kill as many sprites as possible. Survival You have three lives, every time you try to hit a sprite and miss, you lose a life. ???? Whatever I think of. I am a rookie to game design in general, and I don't know the best way to make my game look good, and play well. I could have all of these sprites on the screen at the same time, or I could have them come in waves, for example 10 of sprite_a come on, and once they are killed, 10 of sprite_b come on, etc... Please give me your opinion about which one I should code. If you have any other suggestions for either a third gamemode, or a completely different way to make the levels, feel free to tell me.

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  • Web Applications Desktop Integrator (WebADI) Feature for Install Base Mass Update in 12.1.3

    - by LuciaC
    Purpose The integration of WebADI technology with the Install Base Mass Update function is designed to make creation and update of bulk item instances much easier than in the past. What is it? WebADI is an Excel-based desktop application where users can download an Excel template with item instances pre-populated based on search criteria.  Users can create and update item instances in the Excel sheet and finally upload the Excel data using an "upload" option available in the Excel menu. On upload, the modified data will bulk upload to interface tables which are processed by an asynchronous concurrent program that users can monitor for the uploaded results. Advantage: This allows users to work in a disconnected Environment: session time outs can be avoided, as once a template is downloaded the user can work in a disconnected environment and once all updates are done the new input can be uploaded. Also the data can be saved for later update and upload. For more details review the following: R12.1.3 Install Base WebADI Mass Update Feature (Doc ID 1535936.1) How To Use Install Base WebADI Mass Update Feature In Release 12.1.3 (Doc ID 1536498.1).

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  • MySQL documentation writer wanted

    - by stefanhinz
    As MySQL is thriving and growing, we're looking for an experienced technical writer located in Europe or North America to join the MySQL documentation team.For this job, we need the best and most dedicated people around. You will be part of a geographically distributed documentation team responsible for the technical documentation of all MySQL products. Team members are expected to work independently, requiring discipline and excellent time-management skills as well as the technical facilities to communicate across the Internet.Candidates should be prepared to work intensively with our engineers and support personnel. The overall team is highly distributed across different geographies and time zones. Our source format is DocBook XML. We're not just writing documentation, but also handling publication. This means you should be familiar with DocBook, and willing to learn our publication infrastructure.Candidates should therefore be interested not just in writing but also in the technical aspects of publishing documentation. Regarding your initial areas of authoring, those would be MySQL Cluster, MySQL Enterprise Monitor and Backup, and various parts of the MySQL server documentation (also known as the MySQL Reference Manual). This means you should be familiar with MySQL in general, and preferably also with MySQL Cluster and the MySQL Enterprise offerings.Other qualifications: Native English speaker 3 or more years previous experience in writing software documentation Excellent written and oral communication skills Ability to provide (online) samples of your work, e.g. books or articles Curiosity to learn new technologies Familiarity with distributed working environments and versioning systems such as SVN Comfortable with working on multiple operating systems, particularly Windows, Mac OS X, and Linux Ability to administer own workstations and test environment If you're interested, contact me under [email protected].

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  • Marking Discussions as Answered

    As a contributor to a number of projects on CodePlex I really like the fact that the discussions feature exists but also I need ways to help me sort the discussions threads so I can make sure no-one is getting forgotten about. Seems like a lot of you agreed as the feature request Provide feature to allow Coordinators to mark Discussions threads as 'Answered' is our number 2 voted feature right now with 178 votes.  Today we rolled out the first iteration of “answer” support to discussions. In this first iteration we wanted to keep it simple and lightweight. The original poster of the thread along with project owners, developers or editors can mark any post to the thread as an answer. You can have any number of answers marked in a thread and it’s very quick to mark or unmark a post as an answer.  We deliberately keep the answers in the originally posted order so that you can see them in context with the discussion thread. When viewing discussions the default view is still to see everything, but you can easily filter by “Unanswered”.  You can even save that as a bookmark so as someone interested in the project can quickly jump to the unanswered discussion threads to go help out on. As I mention, we kept this first pass of the answering feature as simple and as lightweight as possible so that we can get some feedback on it. Head on over to the issue tracking this feature if you have any thoughts once you have used it for a bit or feel free to respond in the comments. I already have a couple of things I think we want to do such as a refresh of the look and feel of discussions in general along, make it easier to navigate to posts that are marked an answered and surface posts that you do that were marked as answered in your profile page - but if you have ideas then please let us know.

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  • Wednesday at Oracle OpenWorld 2012 - Must See Session: “Cloud and On-Premises Applications Integration, Using Oracle Integration Adapters”

    - by Lionel Dubreuil
    Don’t miss this “CON8642 - Cloud and On-Premises Applications Integration, Using Oracle Integration Adapters“ with Ramkumar Menon - Senior Product Manager, Oracle: Date: Wednesday, Oct 3 Time: 1:15 PM - 2:15 PM Location: Moscone South – 310 Oracle integration adapters in Oracle Fusion Middleware offer organizations a service-oriented approach to unlocking the information assets that have evolved in most IT environments. This session provides a detailed overview of their features and product architecture and an update on the 11g release. It also examines the changing application and technology landscape and how the integration adapters will continue to provide connectivity and harness information from diverse enterprise applications and technologies—both on-premises and in the cloud. Objectives for this session are to: Present an Oracle integration adapters overview Describe key use cases Provide an update on the 11g release and future roadmap Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif";}

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  • How to divide work to a network of computers?

    - by Morpork
    Imagine a scenario as follows: Lets say you have a central computer which generates a lot of data. This data must go through some processing, which unfortunately takes longer than to generate. In order for the processing to catch up with real time, we plug in more slave computers. Further, we must take into account the possibility of slaves dropping out of the network mid-job as well as additional slaves being added. The central computer should ensure that all jobs are finished to its satisfaction, and that jobs dropped by a slave are retasked to another. The main question is: What approach should I use to achieve this? But perhaps the following would help me arrive at an answer: Is there a name or design pattern to what I am trying to do? What domain of knowledge do I need to achieve the goal of getting these computers to talk to each other? (eg. will a database, which I have some knowledge of, be enough or will this involve sockets, which I have yet to have knowledge of?) Are there any examples of such a system? The main question is a bit general so it would be good to have a starting point/reference point. Note I am assuming constraints of c++ and windows so solutions pointing in that direction would be appreciated.

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  • What is involved with writing a lobby server?

    - by Kira
    So I'm writing a Chess matchmaking system based on a Lobby view with gaming rooms, general chat etc. So far I have a working prototype but I have big doubts regarding some things I did with the server. Writing a gaming lobby server is a new programming experience to me and so I don't have a clear nor precise programming model for it. I also couldn't find a paper that describes how it should work. I ordered "Java Network Programming 3rd edition" from Amazon and still waiting for shipment, hopefully I'll find some useful examples/information in this book. Meanwhile, I'd like to gather your opinions and see how you would handle some things so I can learn how to write a server correctly. Here are a few questions off the top of my head: (may be more will come) First, let's define what a server does. It's primary functionality is to hold TCP connections with clients, listen to the events they generate and dispatch them to the other players. But is there more to it than that? Should I use one thread per client? If so, 300 clients = 300 threads. Isn't that too much? What hardware is needed to support that? And how much bandwidth does a lobby consume then approx? What kind of data structure should be used to hold the clients' sockets? How do you protect it from concurrent modification (eg. a player enters or exists the lobby) when iterating through it to dispatch an event without hurting throughput? Is ConcurrentHashMap the correct answer here, or are there some techniques I should know? When a user enters the lobby, what mechanism would you use to transfer the state of the lobby to him? And while this is happening, where do the other events bubble up? Screenshot : http://imageshack.us/photo/my-images/695/sansrewyh.png/

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  • Approach to Authenticate Clients to TCP Server

    - by dab
    I'm writing a Server/Client application where clients will connect to the server. What I want to do, is make sure that the client connecting to the server is actually using my protocol and I can "trust" the data being sent from the client to the server. What I thought about doing is creating a sort of hash on the client's machine that follows a particular algorithm. What I did in a previous version was took their IP address, the client version, and a few other attributes of the client and sent it as a calculated hash to the server, who then took their IP, and the version of the protocol the client claimed to be using, and calculated that number to see if they matched. This works ok until you get clients that connect from within a router environment where their internal IP is different from their external IP. My fix for this was to pass the client's internal IP used to calculate this hash with the authentication protocol. My fear is this approach is not secure enough. Since I'm passing the data used to create the "auth hash". Here's an example of what I'm talking about: Client IP: 192.168.1.10, Version: 2.4.5.2 hash = 2*4*5*1 * (1+9+2) * (1+6+8) * (1) * (1+0) Client Connects to Server client sends: auth hash ip version Server calculates that info, and accepts or denies the hash. Before I go and come up with another algorithm to prove a client can provide data a server (or use this existing algorithm), I was wondering if there are any existing, proven, and secure systems out there for generating a hash that both sides can generate with general knowledge. The server won't know about the client until the very first connection is established. The protocol's intent is to manage a network of clients who will be contributing data to the server periodically. New clients will be added simply by connecting the client to the server and "registering" with the server. So a client connects to the server for the first time, and registers their info (mac address or some other kind of unique computer identifier), then when they connect again, the server will recognize that client as a previous person and associate them with their data in the database.

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  • Move a player to another team, with players stored in one arraylist and teams in another using java

    - by user1056758
    Basically I have a team class, which has an array list that store the players in. In the driver class theres an arraylist that stores the teams. Anyhow I've worked out how to add a player to a specific team and like wise remove a player from said team. Where I'm hitting problems is when I try to transfer one player to another. My understanding is to scan through the first team,and get the player. Then some how add this player to another, by scanning through the chosen team and add to it? I've tried this way but it seems to replace the original player with the new player in both teams. My other approach would be to somehow return the parameters of the player object, create another with the return parameters, remove the orignal then add the new instance in the other team? Really not quite generally how I can go about this, been trying all afternoon! If someone could offer me a general idea, then I can go off and apply the understanding to practice. Many thanks

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