Search Results

Search found 47 results on 2 pages for 'textbooks'.

Page 2/2 | < Previous Page | 1 2 

  • What does the >> symbol mean in Haskell.

    - by CharlesS
    I was reading the Guestbook example for Happstack and noticed the symbol which I didn't see before in the textbooks I studied to learn Haskell (for instance see line 23). What is it? Example I could not find it in Google because it ignores the totally (Bing does not but comes up with tons of non-related results). Thanks!

    Read the article

  • Optimizing lifestyle and training

    - by Gabe
    I am a college freshman who has recently discovered a passion for computer science. Having had my first lick of formal python training last semester, I have cast aside my previously hedonist way of life and tunneled my sights on becoming the most rounded and proficient programmer I can be. I know that I'm taking strides in the right direction (I've stopped smoking, I've been exercising every day, I've taught myself C++ and OpenGL, and I've begun training in kung-fu and meditation), yet I am still finding myself struggling to achieve satisfactory results. I would like to be able to spend a good 3-4 hours every day burning through textbooks. I have the time cleared and the resources allocated. The problem lies in the logistics-- I have never taken anything seriously before. Recently I've realized that I am clueless when it comes to taking care of myself and gaining control of my mind, and it drastically hinders my productivity. My question is this: How can I learn to manage my time and take care of myself such that I can spend the maximum amount of time every day studying with steady concentration? Personal tricks would be key here: techniques you use to get yourself to sleep, a diet that yields focus, even computer break stretching routines or active reading techniques. Anything you could think of here would be great. I was a low-life in high school and I have the drive to turn my life around, I'm just quite a bit behind in the way of good habits :)

    Read the article

  • The Fantastic New WebLogic on Oracle Database Appliance 2.9 Release is Here!

    - by JuergenKress
    Last week was a big day in virtualised ODA-land as it saw the launch of WebLogic on ODA 2.9. Admittedly it doesn't sound like a very exciting release but it is one that we at O-box have been looking forward to for quite some time. Let me explain why, then we'll look into the details... The ODA X4-2 has 48 Intel Xeon cores. That is a lot of compute power. Whilst the largest O-box SOA Appliance single environment configuration can in theory use all those cores (currently with 40 vCPU of SOA!) the vast majority of O-box users will want smaller configurations. Prior to 2.9 the Oracle WebLogic implementation only supported one domain per ODA, so the conundrum O-box development faced last year was either: offer customers only one SOA environment on their O-box for now (but have the benefit of a standard, easily supportable WebLogic installation), or build our own WebLogic/OTD OVM templates from scratch. One of our driving goals with O-box is to give the best possible experience and make the appliance as supportable as possible. Therefore we took the gamble that we would stick with the Oracle's one-domain WebLogic configuration initially, and just hope that it would deliver multi-domain support for us in a timely manner (note: this is probably not a strategy that business textbooks would recommend!). Anyway, we've been working closely with Oracle Product Management for a few months now and I'm delighted to see 2.9 as the fruits of their labour. This also neatly ties in with several recent requests for O-box to include OSB as well as SOA/BPEL (which we have always wanted to have in separate domains). The diagram below is the neatest way to summarise what the new 2.9 release will allow us to deliver, i.e. previously only one 3D box was possible: Read the complete article here. WebLogic Partner Community For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Wiki Technorati Tags: oBox,WebLogic on ODA,ODA,WebLogic,WebLogic Community,Oracle,OPN,Jürgen Kress

    Read the article

  • Is dependency injection by hand a better alternative to composition and polymorphism?

    - by Drake Clarris
    First, I'm an entry level programmer; In fact, I'm finishing an A.S. degree with a final capstone project over the summer. In my new job, when there isn't some project for me to do (they're waiting to fill the team with more new hires), I've been given books to read and learn from while I wait - some textbooks, others not so much (like Code Complete). After going through these books, I've turned to the internet to learn as much as possible, and started learning about SOLID and DI (we talked some about Liskov's substitution principle, but not much else SOLID ideas). So as I've learned, I sat down to do to learn better, and began writing some code to utilize DI by hand (there are no DI frameworks on the development computers). Thing is, as I do it, I notice it feels familiar... and it seems like it is very much like work I've done in the past using composition of abstract classes using polymorphism. Am I missing a bigger picture here? Is there something about DI (at least by hand) that goes beyond that? I understand the possibility of having configurations not in code of some DI frameworks having some great benefits as far as changing things without having to recompile, but when doing it by hand, I'm not sure if it's any different than stated above... Some insight into this would be very helpful!

    Read the article

  • Scaling along an arbitrary axis (Dealing with non-uniform scale)

    - by Jon
    I'm trying to build my own little engine to get more familiar with the concepts of 3D programming. I have a transform class that on each frame it creates a Scaling Matrix (S), a Rotation Matrix from a Quaternion (R) and concatenates them together (S*R). Once i have SR, I insert the translation values into the bottom of the three columns. So i end up with a transformation matrix that looks like: [SR SR SR 0] [SR SR SR 0] [SR SR SR 0] [tx ty tz 1] This works perfectly in all cases except when rotating an object that has a non-uniform scale. For example a unit cube with ScaleX = 4, ScaleY = 2, ScaleZ = 1 will give me a rectangular box that is 4 times as wide as the depth and twice as high as the depth. If i then translate this around, the box stays the same and looks normal. The problem happens whenever I try to rotate this scaled box. The shape itself becomes distorted and it appears as though the Scale factors are affecting the object on the World X,Y,Z axis rather than the local X,Y,Z axis of the object. I've done some pretty extensive research through a variety of textbooks (Eberly, Moller/Hoffman, Phar etc) and there isn't a ton there to go off of. Online, most of the answers say to avoid non-uniform scaling which I understand the desire to avoid it, but I'd still like to figure out how to support it. The only thing I can think off is that when constructing a Scale Matrix: [sx 0 0 0] [0 sy 0 0] [0 0 sz 0] [0 0 0 1] This is scaling along the World Axis instead of the object's local Direction, Up and Right vectors or it's local Z, Y, X axis. Does anyone have any tips or ideas on how to handle construction a transformation matrix that allows for non-uniform scaling and rotation? Thanks!

    Read the article

  • Studying MySQL, SQLite source code to learn about RDBMS implementation

    - by Yang
    I know implementing database is a huge topic, but I want to have a basic understanding of how database systems work (e.g. memory management, binary tree, transaction, sql parsing, multi-threading, partitions, etc) by investigating the source code of the database. Since there are a few already proven very robust open source databases like mysql, sqlite and so on. However, the code are very complicated and I have no clue where to start. Also I find that the old school database textbooks are only explaining the theory, not the implementation details. Can anyone suggest how I should get started and if there are any books that emphasis on the technology and techniques of building dbms used in modern database industry?

    Read the article

  • mysql, sqlite database source code

    - by Yang
    hi guys, i know implementing database is a huge topic, but i want to have a basic understanding of how database systems works (e.g. memory management, binary tree, transaction, sql parsing, multi-threading, partitions, etc) by investigating the source code of the database, since there are a few already proven very robust open source databases like mysql, sqlite and so on. however, the code are very complicated and i have no clue where to start. also i find that the old school database textbooks are only explaining the theory, not the implementation details. Can anyone suggest how should i get started and is there any books that emphasis on the technology and techniques of building dbms used in modern database industry? Thank in advance!

    Read the article

  • SQL? "Show me all the Activities that can be performed by User X."

    - by Casey Fulton
    I'm at my wits end. I've searched like crazy, read plenty of database textbooks and God knows how many online guides, blogs and forums. Can someone put me out of my misery? PseudoSchema Diagram (Warning: although pretty, not in a format even remotely approaching ER diagrams! Primary keys are bold, foreign keys are italics.) Given the above set of tables relating Users to Groups to Privileges, and then a set of Activities that can each require a Privilege to perform, how do you find out this: Show me all the Activities that can be performed by User X. That is: User X is a member of groups G and F; groups G and F correlate to privileges P, Q, R and S; show me all the activities that require privileges either P, Q, R or S. How do you do this?

    Read the article

  • Creating problem-sets with answers in Latex

    - by ARV
    Hello everyone. I want to typeset Mathematical problem-sets in Latex. My requirements are as follows: When I type them in, I want the questions and the answers to be next to each other in the source-code so that fixing errors, etc. can be done easily. However, when the document is typeset, I want the answers to appear in a separate "Answers" section just the way they do in textbooks. Does anyone know of a way to do this? Many thanks in advance!

    Read the article

  • How do you structure computer science University notes?

    - by Sai Perchard
    I am completing a year of postgraduate study in CS next semester. I am finishing a law degree this year, and I will use this to briefly explain what I mean when I refer to the 'structure' of University notes. My preferred structure for authoring law notes: Word Two columns 0.5cm margins (top, right, bottom, middle, left) Body text (10pt, regular), 3 levels of headings (14/12/10pt, bold), 3 levels of bulleted lists Color A background for cases Color B background for legislation I find that it's crucial to have a good structure from the outset. My key advice to a law student would be to ensure styles allows cases and legislation to be easily identified from supporting text, and not to include too much detail regarding the facts of cases. More than 3 levels of headings is too deep. More than 3 levels of a bulleted list is too deep. In terms of CS, I am interested in similar advice; for example, any strategies that have been successfully employed regarding structure, and general advice regarding note taking. Has latex proved better than Word? Code would presumably need to be stylistically differentiated, and use a monospaced font - perhaps code could be written in TextMate so that it could be copied to retain syntax highlighting? (Are notes even that useful in a CS degree? I am tempted to simply use a textbook. They are crucial in law.) I understand that different people may employ varying techniques and that people will have personal preferences, however I am interested in what these different techniques are. Update Thank you for the responses so far. To clarify, I am not suggesting that the approach should be comparable to that I employ for law. I could have been clearer. The consensus so far seems to be - just learn it. Structure of notes/notes themselves are not generally relevant. This is what I was alluding to when I said I was just tempted to use a textbook. Re the comment that said textbooks are generally useless - I strongly disagree. Sure, perhaps the recommended textbook is useless. But if I'm going to learn a programming language, I will (1) identify what I believe to be the best textbook, and (2) read it. I was unsure if the combination of theory with code meant that lecture notes may be a more efficient way to study for an exam. I imagine that would depend on the subject. A subject specifically on a programming language, reading a textbook and coding would be my preferred approach. But I was unsure if, given a subject containing substantive theory that may not be covered in a single textbook, people may have preferences regarding note taking and structure.

    Read the article

  • Need help identifing what resources (eg. In MIT OpenCourseWare) can help me prepare for a test [closed]

    - by jiewmeng
    I am entering uni soon. I can sit for a placement test to see if I elegible for exemptions. The details are http://www.comp.nus.edu.sg/undergraduates/TestScope11_12.html Or CS2100 Computer Organisation (please click title) The objective of this module is to familiarise students with the fundamentals of computing devices. Through this module students will understand the basics of data representation, and how the various parts of a computer work, separately and with each other. This allows students to understand the issues in computing devices, and how these issues affect the implementation of solutions. Topics covered include data representation systems, combinational and sequential circuit design techniques, assembly language, processor execution cycles, pipelining, memory hierarchy and input/output systems. Recommended Textbooks Digital Design: Principles and Practices [DDPP] by John F. Wakerly, Prentice-Hall. ISBN 0-13-324500-4. Computer Organizations and Design (The hardware/software interface) by David A. Patterson and John L. Hennessy. CS2105 Introduction to Computer Networks (please click title) This course aims to provide a broad introduction to computer networks and some appreciations of network application programming. It covers a range of topics including basic data communication and computer network concepts, protocols, networked computing concepts and principles, network applications development and network security. The emphasis of teaching is on the working principles and application of computer networks. As an integral part of the course, tutorials and practical assignments enforcing learning will also be given. These assignments provide an early exposure in network application programming and they should be able to complete by using personal computers and school's network facilities. Topics included: An overview of computer networks and the Internet Basic data communications Application layer Transport layer Network layer and routing Link layer and local area networks Recommended Textbook James F. Kurose & Keith W. Ross, Computer networking: A top-down approach featuring internet, Addison Wesley, 2001 I am wondering what resources eg. MIT OpenCourseWare or other universities resources are available to help he perpare for these particular modubles. I am thinking does the Networking one look like CCNA? The computer oragization. Its like electronics, assembly etc? I learnt some electronics in Poly but looking at the sample papers, uni looks very different... I have about 1 month to prepare if I want any chance of exempting from these modules :) any help?

    Read the article

  • What economic books would you suggest for learning about economic valuation of goods and simulations thereof?

    - by Rushyo
    I'm looking to create an economic model for a game based on goods created procedurally. Every natural resource and produced good would be procedurally generated, with certain goods being assigned certain uses. Fakesium might be used for the production of Weapon A and produced from Fakesium factories which use Dilithium and Widgets as reagents, where Widgets are also the product of Foo and Bar The problem is not creating the resources and their various production utlities - but getting the game's AI empires and merchants to (Addendum: somewhat) correctly value the goods according to their scarcity, utility and production costs. I need to create a simulation of goods which allows the various game factions to assign a common value denominator (credits) to each resource, depending on how much its worth to that empire. I see the simulation being something like: "I have a high requirement for Weapon A. Since I don't have much of Fakesium, which is needed for Weapon A - I must have a high demand for Fakesium. If I can acquire Fakesium, devalue it. If not, increase its value - and also increase demand for Dilithium and Widgets too." This is very naive - because it may be much much cheaper for the empire to simply purchase Dilithium and Widgets directly rather than purchasing Fakesium, for example. Another example is two resources might allow the creation of Weapon A (Fakesium and Lieron), so we'd need to consider that. I've been scratching my head over the problem and it keeps growing. By the time the player joins the world, I'd expect enough iterations of this process to have occurred that prices would have largely normalised - and would then only trigger rarely to compensate for major changes (eg. if the player blows up the world's only Foo mine!) Could anyone suggest resources (books, largely) which outline this style of modelling, preferably in the context of simulations? Since this problem would never occur outside fantasy worlds, I figured this is probably the most likely place to find people who have encountered similar problems and I'm sure there's people who know of good places for Games Developers to start looking at less specific economic theory too. Additionally, does anyone know of any developers with blogs whose games or research applications perform similar modelling? EDIT: I think I should underline that I'm not looking for optimal solutions. I'm looking to make the actors impulsive - making rudimentary decisions based on fuzzy inputs about what they care about or don't. I'm aiming to understand the problem area better not derive answers. All the textbooks I've found seem to be about real-world economics or how to solve complex theoretical problems, neither of which are terribly relevant to the actor's decision making.

    Read the article

  • Is it smart to take a year off from school to get experience?

    - by user134147
    firstly I apologize if this question is not appropriate for the site, but I've seen other similar (though slightly deviant) questions on this sight before and I know the people here are the most qualified to answer my question. Anyways, I'm currently between my sophomore and junior years at a 4 year university, and after a bit of deliberation I've decided on computer science as a major (BA, by the way, as a BS would require me to stay at least an extra year the way our program is set up). I've been interested now in programming for a few months and I've developed a passion for it in a very short time. I began learning C++, migrating to Java recently when I learned my school focuses on this language. Now, I should mention that the concept of higher education has never sat well with me, so part of my motivation for wanting to take time off is to truly challenge myself and see what I can accomplish when I actually try at something. The autodidact in me finds it difficult to focus on my passions while trying to keep a high GPA in unrelated classes. However, I understand the times we live in and therefore would plan to complete my degree after this year. So my question is whether or not the skills I learn in a year off from college could justify the time off from school. Unfortunately, I don't believe I know enough yet to gain any professional experience (internship, etc.) so I would mostly focus my time on learning Java and another language, possibly Wordpress (to gain an understanding of web programming concepts as I have not yet decided what field I want to get into, and to make some money to fund my off-year), and to delve into security concepts, which also interest me. I'm hoping I could work on projects, such as simple applications or contributions to open source software during this time to enhance my resume once I do finish school, so I can find a job out of college easier. I do not want to be the new hire who knows nothing beyond the concepts of his Java textbooks. Does anyone have any input about these thoughts of mine, or any ideas for where I should focus my studies or how high I might set the bar for my work? Thanks a lot everyone!

    Read the article

  • Cheap desktop computer in 19" rack-mountable form-factor?

    - by Alex Basson
    I'm a high school teacher at a small private school. As of this year, we have SMARTBoards in every classroom (though I've had one in the class I share for two years now). The classrooms themselves don't have computers in them, so we teachers bring our laptops to class and connect them to the boards. This has several disadvantages: This takes a few minutes while we wait for the board to boot up and then orient the board to our individual laptop -- we have to do this every time b/c different teachers have different laptops requiring different orientations. This isn't ideal because when you only have 43 minutes per class period, waiting five minutes just to get started is a real waste. Carrying your laptop to class doesn't sound so bad until you consider that we're also carrying textbooks and piles of student papers, and we're carrying it all through crowded high school hallways. More than one laptop has fallen THUNK to the floor, with dire consequences. We feel we could eliminate the need to use our laptops with the SMARTBoards if we had a dedicated computer in each classroom hooked up to the board at all times. Each board set-up is connected to a podium with a standard 19" rack in it, currently housing a power supply and DVD player. There're plenty of rack spaces available. So I'm thinking: maybe we could get some inexpensive computers in a 19" rack-mountable form factor, install them in the podiums, and connect them to the boards on a permanent basis. Any suggestions?

    Read the article

  • Ti Launchpad

    - by raysmithequip
    Just thought I would get a couple of notes up here for reference to anyone that is interested...it is now Feb 2011 and I have not been posting here enough to remember this blog. Back in Nov 2010 I ordered the Ti launchpad msp430, it is a little target board kit replete with a mini USB cable, two very inexpensive programmable mcu's and a couple of pin headers with a couple of led's on board, a spi connector some on board jumpers and two programmable micro switches....all for less than $5.00...INCLUDING SHIPPING!!....not bad when the ardruino's are running around 20.00 for the target board, atmega328 and cable off of eBay...I wont even mention the microchip pic right now.  Naw, for $5.00 the Ti launchpad kit is about the cheapest fun around...if-uns your a geek that is... Well, the launchpad was backordered for almost two months, came like Xmas eve in fact...I had almost forgotten it!! And really, it was way late and not my idea of an Xmas present for myself.  That would of been the web expressions 4 I bought a few weeks back.  With all the holidays, I did not even look at it till last week, in fact I passed the wrapped board around at my local ham club meeting during points of personal privilege....some oh's and ahhs but mostly duhs...I actually ordered it to avoid downloading the huge code compressor studio 4 (CCS) that was supposed to be included on the cd.  No cd.  I had already downloaded IAR  another programming IDE for these little micro bugs. In my spare time I toyed with IAR and the launchpad board but after about two days of playing delete the driver with windows I decided to just download CCS 4, the code limited version, and give that a shot......CCS 4, is a good rewrite from the earlier versions, it is based on Eclipse as an IDE and includes the drivers for the msp430 target board I received in the kit.  Once installed I quickly configured the debugger for the target chip which was already plugged into the dip socket at the factory, msp430G2131 from he drop down list and clicked ok...I was in!! The CCS4 is full of bells and whistles compared to the IAR, which I would of preferred for the simplicity.  But the code compressor studio really does have it all!!..the code limited version is free, and of all things will give you java script editor box.  The whole layout in debugger mode reminds me of any modern programmer IDE...I mean sure give me Tex anytime but you simply must admire all the boxes and options included in the GUI.  It was a simple matter to check the assembly code in the flash and ram memory that came preloaded for the launchpad kit.  Assembly.  I am right now looking for my old assembly textbooks...sure I remember how to use mov and add etc but a couple of the commands are a little more than vague anymore.  Still, these little mcu's are about 50 cents each and might just work in a couple of projects I have lined up for the near future.  I may document the code here.  Luckily, I plan to write the code in c++ for the main project but if it has to be assembly, no prob.  For reference, the program that came already on the 2131 in the kit was a temperature indicator that alternately flashed red and green leds and changed the intensity of either depending on whether the temp was rising or falling...neat.  Neat enough that it might be worthwhile banging out a little GUI in windows 7 to test the new user device system calls, maybe put a temp gauge widget up on the desktop...just to keep from getting bored.  If you see some assembly code on this blog, you know I was doing something with one of the many mcu's out there.....thats all for now, more to follow...a bit later, of course.

    Read the article

  • Nested Routes and Parameters for Rails URLs (Best Practice)

    - by viatropos
    Hey there, I have a decent understanding of RESTful urls and all the theory behind not nesting urls, but I'm still not quite sure how this looks in an enterprise application, like something like Amazon, StackOverflow, or Google... Google has urls like this: http://code.google.com/apis/ajax/ http://code.google.com/apis/maps/documentation/staticmaps/ https://www.google.com/calendar/render?tab=mc Amazon like this: http://www.amazon.com/books-used-books-textbooks/b/ref=sa_menu_bo0?ie=UTF8&node=283155&pf_rd_p=328655101&pf_rd_s=left-nav-1&pf_rd_t=101&pf_rd_i=507846&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1PK4ZKN4YWJJ9B86ANC9 http://www.amazon.com/Ruby-Programming-Language-David-Flanagan/dp/0596516177/ref=sr_1_1?ie=UTF8&s=books&qid=1258755625&sr=1-1 And StackOverflow like this: http://stackoverflow.com/users/169992/viatropos http://stackoverflow.com/questions/tagged/html http://stackoverflow.com/questions/tagged?tagnames=html&sort=newest&pagesize=15 So my question is, what is best practice in terms of creating urls for systems like these? When do you start storing parameters in the url, when don't you? These big companies don't seem to be following the rules so hotly debated in the ruby community (that you should almost never nest URLs for example), so I'm wondering how you go about implementing your own urls in larger scale projects because it seems like the idea of not nesting urls breaks down at anything larger than a blog. Any tips?

    Read the article

  • Learning Basic Mathematics

    - by NeedsToKnow
    I'm going to just come out and say it. I'm 20 and can't do maths. Two years ago I passed the end-of-high-school mathematics exam (but not at school), and did pretty well. Since then, I haven't done a scrap of mathematics. I wondered just how bad I had gotten, so I was looking at some simple algebra problems. You know, the kind you learn halfway through highschool. 5(-3x - 2) - (x - 3) = -4(4x + 5) + 13 Couldn't do them. I've got half a year left until I start a Computer Science undergraduate degree. I love designing and creating programs, and I remember I loved mathematics back when I did it. Basically, I've had a pretty bad education, but I want to be knowledgable in these areas. I was thinking of buying some high school textbooks and reading them, but I'm not sure this is the right way to go. I need to start off at some basic level and work towards a greater understanding. My question is: What should I study, how should I study, and what books can you recommend? Thanks!

    Read the article

  • Is there really such a thing as "being good at math"?

    - by thezhaba
    Aside from gifted individuals able to perform complex calculations in their head, I'm wondering if proficiency in mathematics, namely calculus and algebra, has really got to do with one's natural inclination towards sciences, if you can put it that way. A number of students in my calculus course pick up material in seemingly no time whereas I, personally, have to spend time thinking about and understanding most concepts. Even then, if a question that requires a bit more 'imagination' comes up I don't always recognize the concepts behind it, as is the case with calculus proofs, for instance. Nevertheless, I refuse to believe that I'm simply not made for it. I do very well in programming and software engineering courses where a lot of students struggle. At first I could not grasp what they found to be so difficult, but eventually I realized that having previous programming experience is a great asset -- once I've seen and made practical use of the programming concepts learning about them in depth in an academic setting became much easier as I have then already seen their use "in the wild". I suppose I'm hoping that something similar happens with mathematics -- perhaps once the practical idea behind a concept (which authors of textbooks sure do a great job of concealing..) is evident, understanding the seemingly dry and symbolic ideas and proofs would be more obvious? I'm really not sure. All I'm sure of is I'd like to get better at calculus, but I don't yet understand why some of us pick it up easily while others have to spend considerable amounts of time on it and still not have complete understanding if an unusual problem is given.

    Read the article

  • Questions about the Backpropogation Algorithm

    - by Colemangrill
    I have a few questions concerning backpropogation. I'm trying to learn the fundamentals behind neural network theory and wanted to start small, building a simple XOR classifier. I've read a lot of articles and skimmed multiple textbooks - but I can't seem to teach this thing the pattern for XOR. Firstly, I am unclear about the learning model for backpropogation. Here is some pseudo-code to represent how I am trying to train the network. [Lets assume my network is setup properly (ie: multiple inputs connect to a hidden layer connect to an output layer and all wired up properly)]. SET guess = getNetworkOutput() // Note this is using a sigmoid activation function. SET error = desiredOutput - guess SET delta = learningConstant * error * sigmoidDerivative(guess) For Each Node in inputNodes For Each Weight in inputNodes[n] inputNodes[n].weight[j] += delta; // At this point, I am assuming the first layer has been trained. // Then I recurse a similar function over the hidden layer and output layer. // The prime difference being that it further divi's up the adjustment delta. I realize this is probably not enough to go off of, and I will gladly expound on any part of my implementation. Using the above algorithm, my neural network does get trained, kind of. But not properly. The output is always XOR 1 1 [smallest number] XOR 0 0 [largest number] XOR 1 0 [medium number] XOR 0 1 [medium number] I can never train the [1,1] [0,0] to be the same value. If you have any suggestions, additional resources, articles, blogs, etc for me to look at I am very interested in learning more about this topic. Thank you for your assistance, I appreciate it greatly!

    Read the article

  • Looking for a book which teaches how to write applications (as opposed to writng code)

    - by rumtscho
    I am not a developer. I have coded for fun and for university projects in several languages, and during an internship, I have written code which is still in use by a department of Fortune Global 500 company. I also have extensive theoretical knowledge of software engineering - process models, architecture, project management, UI construction using Lauesen's virtual windows... you get the picture. But I am not involved with software development in my job. I recently decided to start coding for fun again, and now I have some free days to do it. But this time, I want to do it right. I want to write a real, useful application, install it on my devices and use it myself. Also I want to publish it for others to use, should they want to do so. I am vaguely aware that there is more to writing an application than to writing code. There is stuff like version control software, decision for the right IDE, having a suite of unit tests, producing an installation package - and probably lots of other things I never thought of but which must be taken care of in a proper application, as opposed to a bunch of classes I am running from my IDE. All this is stuff I should know before I start, but I have not learned it. Coding books touch on some of the subjects like IDE choice, but don't go into detail, and are not exhaustive. Theoretical software engineering textbooks are even less helpful. So is there a book which teaches exactly that? I know that I can find information on each of these topics on the Internet, but I'd rather have a systematic book exhaustively listing all the things I should take care of if I want to create a good application, and offering the currently accepted solutions for them. In the best case, it will be language- and platform independent, but if you know of a good book focusing on a specific platform, I would like to know about it too. I know I want a lot, but given how important such knowledge is and how many people need it, surely somebody must have written such a book?

    Read the article

  • eBooks on iPad vs. Kindle: More Debate than Smackdown

    - by andrewbrust
    When the iPad was presented at its San Francisco launch event on January 28th, Steve Jobs spent a significant amount of time explaining how well the device would serve as an eBook reader. He showed the iBooks reader application and iBookstore and laid down the gauntlet before Amazon and its beloved Kindle device. Almost immediately afterwards, criticism came rushing forth that the iPad could never beat the Kindle for book reading. The curious part of that criticism is that virtually no one offering it had actually used the iPad yet. A few weeks later, on April 3rd, the iPad was released for sale in the United States. I bought one on that day and in the few additional weeks that have elapsed, I’ve given quite a workout to most of its capabilities, including its eBook features. I’ve also spent some time with the Kindle, albeit a first-generation model, to see how it actually compares to the iPad. I had some expectations going in, but I came away with conclusions about each device that were more scenario-based than absolute. I present my findings to you here.   Vital Statistics Let’s start with an inventory of each device’s underlying technology. The iPad has a color, backlit LCD screen and an on-screen keyboard. It has a battery which, on a full charge, lasts anywhere from 6-10 hours. The Kindle offers a monochrome, reflective E Ink display, a physical keyboard and a battery that on my first gen loaner unit can go up to a week between charges (Amazon claims the battery on the Kindle 2 can last up to 2 weeks on a single charge). The Kindle connects to Amazon’s Kindle Store using a 3G modem (the technology and network vary depending on the model) that incurs no airtime service charges whatsoever. The iPad units that are on-sale today work over WiFi only. 3G-equipped models will be on sale shortly and will command a $130 premium over their WiFi-only counterparts. 3G service on the iPad, in the U.S. from AT&T, will be fee-based, with a 250MB plan at $14.99 per month and an unlimited plan at $29.99. No contract is required for 3G service. All these tech specs aside, I think a more useful observation is that the iPad is a multi-purpose Internet-connected entertainment device, while the Kindle is a dedicated reading device. The question is whether those differences in design and intended use create a clear-cut winner for reading electronic publications. Let’s take a look at each device, in isolation, now.   Kindle To me, what’s most innovative about the Kindle is its E Ink display. E Ink really looks like ink on a sheet of paper. It requires no backlight, it’s fully visible in direct sunlight and it causes almost none of the eyestrain that LCD-based computer display technology (like that used on the iPad) does. It’s really versatile in an all-around way. Forgive me if this sounds precious, but reading on it is really a joy. In fact, it’s a genuinely relaxing experience. Through the Kindle Store, Amazon allows users to download books (including audio books), magazines, newspapers and blog feeds. Books and magazines can be purchased either on a single-issue basis or as an annual subscription. Books, of course, are purchased singly. Oddly, blogs are not free, but instead carry a monthly subscription fee, typically $1.99. To me this is ludicrous, but I suppose the free 3G service is partially to blame. Books and magazine issues download quickly. Magazine and blog subscriptions cause new issues or posts to be pushed to your device on an automated basis. Available blogs include 9000-odd feeds that Amazon offers on the Kindle Store; unless I missed something, arbitrary RSS feeds are not supported (though there are third party workarounds to this limitation). The shopping experience is integrated well, has an huge selection, and offers certain graphical perks. For example, magazine and newspaper logos are displayed in menus, and book cover thumbnails appear as well. A simple search mechanism is provided and text entry through the physical keyboard is relatively painless. It’s very easy and straightforward to enter the store, find something you like and start reading it quickly. If you know what you’re looking for, it’s even faster. Given Kindle’s high portability, very reliable battery, instant-on capability and highly integrated content acquisition, it makes reading on whim, and in random spurts of downtime, very attractive. The Kindle’s home screen lists all of your publications, and easily lets you select one, then start reading it. Once opened, publications display in crisp, attractive text that is adjustable in size. “Turning” pages is achieved through buttons dedicated to the task. Notes can be recorded, bookmarks can be saved and pages can be saved as clippings. I am not an avid book reader, and yet I found the Kindle made it really fun, convenient and soothing to read. There’s something about the easy access to the material and the simplicity of the display that makes the Kindle seduce you into chilling out and reading page after page. On the other hand, the Kindle has an awkward navigation interface. While menus are displayed clearly on the screen, the method of selecting menu items is tricky: alongside the right-hand edge of the main display is a thin column that acts as a second display. It has a white background, and a scrollable silver cursor that is moved up or down through the use of the device’s scrollwheel. Picking a menu item on the main display involves scrolling the silver cursor to a position parallel to that menu item and pushing the scrollwheel in. This navigation technique creates a disconnect, literally. You don’t really click on a selection so much as you gesture toward it. I got used to this technique quickly, but I didn’t love it. It definitely created a kind of anxiety in me, making me feel the need to speed through menus and get to my destination document quickly. Once there, I could calm down and relax. Books are great on the Kindle. Magazines and newspapers much less so. I found the rendering of photographs, and even illustrations, to be unacceptably crude. For this reason, I expect that reading textbooks on the Kindle may leave students wanting. I found that the original flow and layout of any publication was sacrificed on the Kindle. In effect, browsing a magazine or newspaper was almost impossible. Reading the text of individual articles was enjoyable, but having to read this way made the whole experience much more “a la carte” than cohesive and thematic between articles. I imagine that for academic journals this is ideal, but for consumer publications it imposes a stripped-down, low-fidelity experience that evokes a sense of deprivation. In general, the Kindle is great for reading text. For just about anything else, especially activity that involves exploratory browsing, meandering and short-attention-span reading, it presents a real barrier to entry and adoption. Avid book readers will enjoy the Kindle (if they’re not already). It’s a great device for losing oneself in a book over long sittings. Multitaskers who are more interested in periodicals, be they online or off, will like it much less, as they will find compromise, and even sacrifice, to be palpable.   iPad The iPad is a very different device from the Kindle. While the Kindle is oriented to pages of text, the iPad orbits around applications and their interfaces. Be it the pinch and zoom experience in the browser, the rich media features that augment content on news and weather sites, or the ability to interact with social networking services like Twitter, the iPad is versatile. While it shares a slate-like form factor with the Kindle, it’s effectively an elegant personal computer. One of its many features is the iBook application and integration of the iBookstore. But it’s a multi-purpose device. That turns out to be good and bad, depending on what you’re reading. The iBookstore is great for browsing. It’s color, rich animation-laden user interface make it possible to shop for books, rather than merely search and acquire them. Unfortunately, its selection is rather sparse at the moment. If you’re looking for a New York Times bestseller, or other popular titles, you should be OK. If you want to read something more specialized, it’s much harder. Unlike the awkward navigation interface of the Kindle, the iPad offers a nearly flawless touch-screen interface that seduces the user into tinkering and kibitzing every bit as much as the Kindle lulls you into a deep, concentrated read. It’s a dynamic and interactive device, whereas the Kindle is static and passive. The iBook reader is slick and fun. Use the iPad in landscape mode and you can read the book in 2-up (left/right 2-page) display; use it in portrait mode and you can read one page at a time. Rather than clicking a hardware button to turn pages, you simply drag and wipe from right-to-left to flip the single or right-hand page. The page actually travels through an animated path as it would in a physical book. The intuitiveness of the interface is uncanny. The reader also accommodates saving of bookmarks, searching of the text, and the ability to highlight a word and look it up in a dictionary. Pages display brightly and clearly. They’re easy to read. But the backlight and the glare made me less comfortable than I was with the Kindle. The knowledge that completely different applications (including the Web and email and Twitter) were just a few taps away made me antsy and very tempted to task-switch. The knowledge that battery life is an issue created subtle discomfort. If the Kindle makes you feel like you’re in a library reading room, then the iPad makes you feel, at best, like you’re under fluorescent lights at a Barnes and Noble or Borders store. If you’re lucky, you’d be on a couch or at a reading table in the store, but you might also be standing up, in the aisles. Clearly, I didn’t find this conducive to focused and sustained reading. But that may have more to do with my own tendency to read periodicals far more than books, and my neurotic . And, truth be known, the book reading experience, when not explicitly compared to Kindle’s, was still pleasant. It is also important to point out that Kindle Store-sourced books can be read on the iPad through a Kindle reader application, from Amazon, specific to the device. This offered a less rich experience than the iBooks reader, but it was completely adequate. Despite the Kindle brand of the reader, however, it offered little in terms of simulating the reading experience on its namesake device. When it comes to periodicals, the iPad wins hands down. Magazines, even if merely scanned images of their print editions, read on the iPad in a way that felt similar to reading hard copy. The full color display, touch navigation and even the ability to render advertisements in their full glory makes the iPad a great way to read through any piece of work that is measured in pages, rather than chapters. There are many ways to get magazines and newspapers onto the iPad, including the Zinio reader, and publication-specific applications like the Wall Street Journal’s and Popular Science’s. The New York Times’ free Editors’ Choice application offers a Times Reader-like interface to a subset of the Gray Lady’s daily content. The completely Web-based but iPad-optimized Times Skimmer site (at www.nytimes.com/timesskimmer) works well too. Even conventional Web sites themselves can be read much like magazines, given the iPad’s ability to zoom in on the text and crop out advertisements on the margins. While the Kindle does have an experimental Web browser, it reminded me a lot of early mobile phone browsers, only in a larger size. For text-heavy sites with simple layout, it works fine. For just about anything else, it becomes more trouble than it’s worth. And given the way magazine articles make me think of things I want to look up online, I think that’s a real liability for the Kindle.   Summing Up What I came to realize is that the Kindle isn’t so much a computer or even an Internet device as it is a printer. While it doesn’t use physical paper, it still renders its content a page at a time, just like a laser printer does, and its output appears strikingly similar. You can read the rendered text, but you can’t interact with it in any way. That’s why the navigation requires a separate cursor display area. And because of the page-oriented rendering behavior, turning pages causes a flash on the display and requires a sometimes long pause before the next page is rendered. The good side of this is that once the page is generated, no battery power is required to display it. That makes for great battery life, optimal viewing under most lighting conditions (as long as there is some light) and low-eyestrain text-centric display of content. The Kindle is highly portable, has an excellent selection in its store and is refreshingly distraction-free. All of this is ideal for reading books. And iPad doesn’t offer any of it. What iPad does offer is versatility, variety, richness and luxury. It’s flush with accoutrements even if it’s low on focused, sustained text display. That makes it inferior to the Kindle for book reading. But that also makes it better than the Kindle for almost everything else. As such, and given that its book reading experience is still decent (even if not superior), I think the iPad will give Kindle a run for its money. True book lovers, and people on a budget, will want the Kindle. People with a robust amount of discretionary income may want both devices. Everyone else who is interested in a slate form factor e-reading device, especially if they also wish to have leisure-friendly Internet access, will likely choose the iPad exclusively. One thing is for sure: iPad has reduced Kindle’s market, and may have shifted its mass market potential to a mere niche play. If Amazon is smart, it will improve its iPad-based Kindle reader app significantly. It can then leverage the iPad channel as a significant market for the Kindle Store. After all, selling the eBooks themselves is what Amazon should care most about.

    Read the article

  • how to export bind and keyframe bone poses from blender to use in OpenGL

    - by SaldaVonSchwartz
    EDIT: I decided to reformulate the question in much simpler terms to see if someone can give me a hand with this. Basically, I'm exporting meshes, skeletons and actions from blender into an engine of sorts that I'm working on. But I'm getting the animations wrong. I can tell the basic motion paths are being followed but there's always an axis of translation or rotation which is wrong. I think the problem is most likely not in my engine code (OpenGL-based) but rather in either my misunderstanding of some part of the theory behind skeletal animation / skinning or the way I am exporting the appropriate joint matrices from blender in my exporter script. I'll explain the theory, the engine animation system and my blender export script, hoping someone might catch the error in either or all of these. The theory: (I'm using column-major ordering since that's what I use in the engine cause it's OpenGL-based) Assume I have a mesh made up of a single vertex v, along with a transformation matrix M which takes the vertex v from the mesh's local space to world space. That is, if I was to render the mesh without a skeleton, the final position would be gl_Position = ProjectionMatrix * M * v. Now assume I have a skeleton with a single joint j in bind / rest pose. j is actually another matrix. A transform from j's local space to its parent space which I'll denote Bj. if j was part of a joint hierarchy in the skeleton, Bj would take from j space to j-1 space (that is to its parent space). However, in this example j is the only joint, so Bj takes from j space to world space, like M does for v. Now further assume I have a a set of frames, each with a second transform Cj, which works the same as Bj only that for a different, arbitrary spatial configuration of join j. Cj still takes vertices from j space to world space but j is rotated and/or translated and/or scaled. Given the above, in order to skin vertex v at keyframe n. I need to: take v from world space to joint j space modify j (while v stays fixed in j space and is thus taken along in the transformation) take v back from the modified j space to world space So the mathematical implementation of the above would be: v' = Cj * Bj^-1 * v. Actually, I have one doubt here.. I said the mesh to which v belongs has a transform M which takes from model space to world space. And I've also read in a couple textbooks that it needs to be transformed from model space to joint space. But I also said in 1 that v needs to be transformed from world to joint space. So basically I'm not sure if I need to do v' = Cj * Bj^-1 * v or v' = Cj * Bj^-1 * M * v. Right now my implementation multiples v' by M and not v. But I've tried changing this and it just screws things up in a different way cause there's something else wrong. Finally, If we wanted to skin a vertex to a joint j1 which in turn is a child of a joint j0, Bj1 would be Bj0 * Bj1 and Cj1 would be Cj0 * Cj1. But Since skinning is defined as v' = Cj * Bj^-1 * v , Bj1^-1 would be the reverse concatenation of the inverses making up the original product. That is, v' = Cj0 * Cj1 * Bj1^-1 * Bj0^-1 * v Now on to the implementation (Blender side): Assume the following mesh made up of 1 cube, whose vertices are bound to a single joint in a single-joint skeleton: Assume also there's a 60-frame, 3-keyframe animation at 60 fps. The animation essentially is: keyframe 0: the joint is in bind / rest pose (the way you see it in the image). keyframe 30: the joint translates up (+z in blender) some amount and at the same time rotates pi/4 rad clockwise. keyframe 59: the joint goes back to the same configuration it was in keyframe 0. My first source of confusion on the blender side is its coordinate system (as opposed to OpenGL's default) and the different matrices accessible through the python api. Right now, this is what my export script does about translating blender's coordinate system to OpenGL's standard system: # World transform: Blender -> OpenGL worldTransform = Matrix().Identity(4) worldTransform *= Matrix.Scale(-1, 4, (0,0,1)) worldTransform *= Matrix.Rotation(radians(90), 4, "X") # Mesh (local) transform matrix file.write('Mesh Transform:\n') localTransform = mesh.matrix_local.copy() localTransform = worldTransform * localTransform for col in localTransform.col: file.write('{:9f} {:9f} {:9f} {:9f}\n'.format(col[0], col[1], col[2], col[3])) file.write('\n') So if you will, my "world" matrix is basically the act of changing blenders coordinate system to the default GL one with +y up, +x right and -z into the viewing volume. Then I also premultiply (in the sense that it's done by the time we reach the engine, not in the sense of post or pre in terms of matrix multiplication order) the mesh matrix M so that I don't need to multiply it again once per draw call in the engine. About the possible matrices to extract from Blender joints (bones in Blender parlance), I'm doing the following: For joint bind poses: def DFSJointTraversal(file, skeleton, jointList): for joint in jointList: bindPoseJoint = skeleton.data.bones[joint.name] bindPoseTransform = bindPoseJoint.matrix_local.inverted() file.write('Joint ' + joint.name + ' Transform {\n') translationV = bindPoseTransform.to_translation() rotationQ = bindPoseTransform.to_3x3().to_quaternion() scaleV = bindPoseTransform.to_scale() file.write('T {:9f} {:9f} {:9f}\n'.format(translationV[0], translationV[1], translationV[2])) file.write('Q {:9f} {:9f} {:9f} {:9f}\n'.format(rotationQ[1], rotationQ[2], rotationQ[3], rotationQ[0])) file.write('S {:9f} {:9f} {:9f}\n'.format(scaleV[0], scaleV[1], scaleV[2])) DFSJointTraversal(file, skeleton, joint.children) file.write('}\n') Note that I'm actually grabbing the inverse of what I think is the bind pose transform Bj. This is so I don't need to invert it in the engine. Also note I went for matrix_local, assuming this is Bj. The other option is plain "matrix", which as far as I can tell is the same only that not homogeneous. For joint current / keyframe poses: for kfIndex in keyframes: bpy.context.scene.frame_set(kfIndex) file.write('keyframe: {:d}\n'.format(int(kfIndex))) for i in range(0, len(skeleton.data.bones)): file.write('joint: {:d}\n'.format(i)) currentPoseJoint = skeleton.pose.bones[i] currentPoseTransform = currentPoseJoint.matrix translationV = currentPoseTransform.to_translation() rotationQ = currentPoseTransform.to_3x3().to_quaternion() scaleV = currentPoseTransform.to_scale() file.write('T {:9f} {:9f} {:9f}\n'.format(translationV[0], translationV[1], translationV[2])) file.write('Q {:9f} {:9f} {:9f} {:9f}\n'.format(rotationQ[1], rotationQ[2], rotationQ[3], rotationQ[0])) file.write('S {:9f} {:9f} {:9f}\n'.format(scaleV[0], scaleV[1], scaleV[2])) file.write('\n') Note that here I go for skeleton.pose.bones instead of data.bones and that I have a choice of 3 matrices: matrix, matrix_basis and matrix_channel. From the descriptions in the python API docs I'm not super clear which one I should choose, though I think it's the plain matrix. Also note I do not invert the matrix in this case. The implementation (Engine / OpenGL side): My animation subsystem does the following on each update (I'm omitting parts of the update loop where it's figured out which objects need update and time is hardcoded here for simplicity): static double time = 0; time = fmod((time + elapsedTime),1.); uint16_t LERPKeyframeNumber = 60 * time; uint16_t lkeyframeNumber = 0; uint16_t lkeyframeIndex = 0; uint16_t rkeyframeNumber = 0; uint16_t rkeyframeIndex = 0; for (int i = 0; i < aClip.keyframesCount; i++) { uint16_t keyframeNumber = aClip.keyframes[i].number; if (keyframeNumber <= LERPKeyframeNumber) { lkeyframeIndex = i; lkeyframeNumber = keyframeNumber; } else { rkeyframeIndex = i; rkeyframeNumber = keyframeNumber; break; } } double lTime = lkeyframeNumber / 60.; double rTime = rkeyframeNumber / 60.; double blendFactor = (time - lTime) / (rTime - lTime); GLKMatrix4 bindPosePalette[aSkeleton.jointsCount]; GLKMatrix4 currentPosePalette[aSkeleton.jointsCount]; for (int i = 0; i < aSkeleton.jointsCount; i++) { F3DETQSType& lPose = aClip.keyframes[lkeyframeIndex].skeletonPose.joints[i]; F3DETQSType& rPose = aClip.keyframes[rkeyframeIndex].skeletonPose.joints[i]; GLKVector3 LERPTranslation = GLKVector3Lerp(lPose.t, rPose.t, blendFactor); GLKQuaternion SLERPRotation = GLKQuaternionSlerp(lPose.q, rPose.q, blendFactor); GLKVector3 LERPScaling = GLKVector3Lerp(lPose.s, rPose.s, blendFactor); GLKMatrix4 currentTransform = GLKMatrix4MakeWithQuaternion(SLERPRotation); currentTransform = GLKMatrix4TranslateWithVector3(currentTransform, LERPTranslation); currentTransform = GLKMatrix4ScaleWithVector3(currentTransform, LERPScaling); GLKMatrix4 inverseBindTransform = GLKMatrix4MakeWithQuaternion(aSkeleton.joints[i].inverseBindTransform.q); inverseBindTransform = GLKMatrix4TranslateWithVector3(inverseBindTransform, aSkeleton.joints[i].inverseBindTransform.t); inverseBindTransform = GLKMatrix4ScaleWithVector3(inverseBindTransform, aSkeleton.joints[i].inverseBindTransform.s); if (aSkeleton.joints[i].parentIndex == -1) { bindPosePalette[i] = inverseBindTransform; currentPosePalette[i] = currentTransform; } else { bindPosePalette[i] = GLKMatrix4Multiply(inverseBindTransform, bindPosePalette[aSkeleton.joints[i].parentIndex]); currentPosePalette[i] = GLKMatrix4Multiply(currentPosePalette[aSkeleton.joints[i].parentIndex], currentTransform); } aSkeleton.skinningPalette[i] = GLKMatrix4Multiply(currentPosePalette[i], bindPosePalette[i]); } Finally, this is my vertex shader: #version 100 uniform mat4 modelMatrix; uniform mat3 normalMatrix; uniform mat4 projectionMatrix; uniform mat4 skinningPalette[6]; uniform lowp float skinningEnabled; attribute vec4 position; attribute vec3 normal; attribute vec2 tCoordinates; attribute vec4 jointsWeights; attribute vec4 jointsIndices; varying highp vec2 tCoordinatesVarying; varying highp float lIntensity; void main() { tCoordinatesVarying = tCoordinates; vec4 skinnedVertexPosition = vec4(0.); for (int i = 0; i < 4; i++) { skinnedVertexPosition += jointsWeights[i] * skinningPalette[int(jointsIndices[i])] * position; } vec4 skinnedNormal = vec4(0.); for (int i = 0; i < 4; i++) { skinnedNormal += jointsWeights[i] * skinningPalette[int(jointsIndices[i])] * vec4(normal, 0.); } vec4 finalPosition = mix(position, skinnedVertexPosition, skinningEnabled); vec4 finalNormal = mix(vec4(normal, 0.), skinnedNormal, skinningEnabled); vec3 eyeNormal = normalize(normalMatrix * finalNormal.xyz); vec3 lightPosition = vec3(0., 0., 2.); lIntensity = max(0.0, dot(eyeNormal, normalize(lightPosition))); gl_Position = projectionMatrix * modelMatrix * finalPosition; } The result is that the animation displays wrong in terms of orientation. That is, instead of bobbing up and down it bobs in and out (along what I think is the Z axis according to my transform in the export clip). And the rotation angle is counterclockwise instead of clockwise. If I try with a more than one joint, then it's almost as if the second joint rotates in it's own different coordinate space and does not follow 100% its parent's transform. Which I assume it should from my animation subsystem which I assume in turn follows the theory I explained for the case of more than one joint. Any thoughts?

    Read the article

< Previous Page | 1 2