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  • Type classes or implicit parameters? What do you prefer and why? [closed]

    - by Petr Pudlák
    I was playing a bit with Scalaz and I realized that Haskell's type classes are very similar to Scala's implicit parameters. While Haskell passes the methods defined by a type class using hidden dictionaries, Scala allows a similar thing using implicit parameters. For example, in Haskell, one could write: incInside :: (Functor f) => f Int -> f Int incInside = fmap (+ 1) and the same function using Scalaz: import scalaz._; import Scalaz._; def incInside[F[_]](x: F[Int])(implicit fn: Functor[F]): F[Int] = fn.fmap(x, (_:Int) + 1); I wonder: If you could choose (i.e. your favorite language would offer both), what would you pick - implicits or type classes? And what are your pros/cons?

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  • Does GNC mean the death of Internet Explorer?

    - by Monika Michael
    From the wikipedia - Google Native Client (NaCl) is a sandboxing technology for running a subset of Intel x86 or ARM native code using software-based fault isolation. It is proposed for safely running native code from a web browser, allowing web-based applications to run at near-native speeds. (Emphasis mine) (Source) Compiled C++ code running in a browser? Are other companies working on a similar offering? What would it mean for the browser landscape?

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  • Confusion related to sigwait in multiprocess system

    - by user34790
    I am having difficulty in understanding IPC in multiprocess system. I have this system where there are three child processes that send two types of signals to their process group. There are four types of signal handling processes responsible for a particular type of signal. There is this monitoring process which waits for both the signals and then processes accordingly. When I run this program for a while, the monitoring process doesn't seem to pick up the signal as well as the signal handling process. I could see in the log that the signal is only being generated but not handled at all. My code is given below #include <cstdlib> #include <iostream> #include <iomanip> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> #include <sys/time.h> #include <signal.h> #include <unistd.h> #include <fcntl.h> #include <cstdio> #include <stdlib.h> #include <stdio.h> #include <pthread.h> using namespace std; double timestamp() { struct timeval tp; gettimeofday(&tp, NULL); return (double)tp.tv_sec + tp.tv_usec / 1000000.; } double getinterval() { srand(time(NULL)); int r = rand()%10 + 1; double s = (double)r/100; } int count; int count_1; int count_2; double time_1[10]; double time_2[10]; pid_t senders[1]; pid_t handlers[4]; pid_t reporter; void catcher(int sig) { printf("Signal catcher called for %d",sig); } int main(int argc, char *argv[]) { void signal_catcher_int(int); pid_t pid,w; int status; if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("1"); return 1; } if(signal(SIGUSR2 ,SIG_IGN) == SIG_ERR) { perror("2"); return 2; } if(signal(SIGINT,signal_catcher_int) == SIG_ERR) { perror("3"); return 2; } //Registering the signal handler for(int i=0; i<4; i++) { if((pid = fork()) == 0) { cout << i << endl; //struct sigaction sigact; sigset_t sigset; int sig; int result = 0; sigemptyset(&sigset); if(i%2 == 0) { if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); return 2; } sigaddset(&sigset, SIGUSR1); sigprocmask(SIG_BLOCK, &sigset, NULL); } else { if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("2"); return 2; } sigaddset(&sigset, SIGUSR2); sigprocmask(SIG_BLOCK, &sigset, NULL); } while(true) { int result = sigwait(&sigset, &sig); if(result == 0) { cout << "The caught signal is " << sig << endl; } } exit(0); } else { cout << "Registerd the handler " << pid << endl; handlers[i] = pid; } } //Registering the monitoring process if((pid = fork()) == 0) { sigset_t sigset; int sig; int result = 0; sigemptyset(&sigset); sigaddset(&sigset, SIGUSR1); sigaddset(&sigset, SIGUSR2); sigprocmask(SIG_BLOCK, &sigset, NULL); while(true) { int result = sigwait(&sigset, &sig); if(result == 0) { cout << "The monitored signal is " << sig << endl; } else { cout << "error" << endl; } } } else { reporter = pid; } sleep(3); //Registering the signal generator for(int i=0; i<1; i++) { if((pid = fork()) == 0) { if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("1"); return 1; } if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); return 2; } srand(time(0)); while(true) { volatile int signal_id = rand()%2 + 1; cout << "Generating the signal " << signal_id << endl; if(signal_id == 1) { killpg(getpgid(getpid()), SIGUSR1); } else { killpg(getpgid(getpid()), SIGUSR2); } int r = rand()%10 + 1; double s = (double)r/100; sleep(s); } exit(0); } else { cout << "Registered the sender " << pid << endl; senders[i] = pid; } } while(w = wait(&status)) { cout << "Wait on PID " << w << endl; } } void signal_catcher_int(int the_sig) { //cout << "Handling the Ctrl C signal " << endl; for(int i=0; i<1; i++) { kill(senders[i],SIGKILL); } for(int i=0; i<4; i++) { kill(handlers[i],SIGKILL); } kill(reporter,SIGKILL); exit(3); } Any suggestions? Here is a sample of the output as well In the beginning Registerd the handler 9544 Registerd the handler 9545 1 Registerd the handler 9546 Registerd the handler 9547 2 3 0 Registered the sender 9550 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 2 The caught signal is 12 The caught signal is 12 The monitored signal is 12 Generating the signal 2 Generating the signal 2 The caught signal is 12 The caught signal is 12 Generating the signal 1 The caught signal is 12 The monitored signal is 10 The monitored signal is 12 Generating the signal 1 Generating the signal 2 The caught signal is 12 Generating the signal 1 Generating the signal 2 10 The monitored signal is 10 The caught signal is 12 Generating the signal 1 The caught signal is 12 The monitored signal is GenThe caught signal is TheThe caught signal is 10 Generating the signal 2 Later on The monitored signal is GenThe monitored signal is 10 Generating the signal 1 Generating the signal 2 The caught signal is 10 The caught signal is 10 The caught signal is 10 The caught signal is 12 Generating the signal 1 Generating the signal 2 Generating the signal 1 Generating the signal 1 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 1 The caught signal is 12 The caught signal is 10 The caught signal is 10 Generating the signal 2 Generating the signal 1 Generating the signal 1 Generating the signal 2 Generating the signal 1 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 1 Generating the signal 2 Generating the signal 1 Generating the signal 2 Generating the signal 2 The caught signal is 10 Generating the signal 2 Generating the signal 1 Generating the signal 1 As you can see initially, the signal was generated and handled both by my signal handlers and monitoring processes. But later on the signal was generated a lot, but it was not quite processes in the same magnitude as before. Further I could see very less signal processing by the monitoring process Can anyone please provide some insights. What's going on?

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  • Java IDE written in pure Java?

    - by Darestium
    Is there a Java IDE written in Java? I just got my year 9 DET laptop today at school, and there are all sorts of restrictions set in place. Somewhat annoyingly, you cannot run any executable other than the ones already installed on the system (for some reason they haven't disabled the use of Command Prompt, PowerShell, or strangely enough, regedit). They allow you to run Java executables, so I thought that would be the only way to be able to program on my crappy laptop at school (when I have finished all my work, naturally) :D Edit: By written in Java, I also mean that the executable, that is used to run the program, has the file extension ".jar", thus running on the JVM. Edit 2: I tried the DrJava IDE, and it worked great, thanks (I can compile and execute programs)! Regarding running Eclipse as through the command line using the command "java -jar "C:/Users.../org.eclipse..."". This results in an error producing a log saying file, the main error is: MESSAGE An error occurred while automatically activating bundle org.eclipse.ui.workbench (182). How do I fix this error (I much perfer working with Eclipse than any other IDE)? Edit 3: Regarding my last edit, just disregard it :D. I fixed the problem by downloading the latest version of Eclipse.

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  • SQL, moving million records from a database to other database [migrated]

    - by Ryoma
    I am a C# developer, I am not really good with SQL. I have a simple questions here. I need to move more than 50 millions records from a database to other database. I tried to use the import function in ms SQL, however it got stuck because the log was full (I got an error message The transaction log for database 'mydatabase' is full due to 'LOG_BACKUP'). The database recovery model was set to simple. My friend said that importing millions records using task-import data will cause the log to be massive and told me to use loop instead to transfer the data, does anyone know how and why? thanks in advance

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  • Recaptcha php problem [closed]

    - by Sam Gabriel
    Hey guys, I'm using recaptcha and I've got a problem, when a user clicks the signup button it redirects him to the sign up verification page, and here is the code, found on the very top of the web code, that checks the recaptcha entered data. <?php require_once('recaptchalib.php'); $privatekey = "***"; $resp = recaptcha_check_answer ($privatekey, $_SERVER["REMOTE_ADDR"], $_POST["recaptcha_challenge_field"], $_POST["recaptcha_response_field"]); if (!$resp->is_valid) { header('location: signup.php'); } ?> But it seems whatever I type in in the recaptcha box, be it right or wrong, I get redirected to the signup.php page. Here is the recaptcha code in the signup.php page: <?php ini_set('display_errors', 'On'); error_reporting(E_ALL | E_STRICT); require_once('recaptchalib.php'); $publickey = "***"; echo recaptcha_get_html($publickey); ?>

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  • Class Design -- Multiple Calls from One Method or One Call from Multiple Methods?

    - by Andrew
    I've been working on some code recently that interfaces with a CMS we use and it's presented me with a question on class design that I think is applicable in a number of situations. Essentially, what I am doing is extracting information from the CMS and transforming this information into objects that I can use programatically for other purposes. This consists of two steps: Retrieve the data from the CMS (we have a DAL that I use, so this is essentially just specifying what data from the CMS I want--no connection logic or anything like that) Map the parsed data to my own [C#] objects There are basically two ways I can approach this: One call from multiple methods public void MainMethodWhereIDoStuff() { IEnumerable<MyObject> myObjects = GetMyObjects(); // Do other stuff with myObjects } private static IEnumerable<MyObject> GetMyObjects() { IEnumerable<CmsDataItem> cmsDataItems = GetCmsDataItems(); List<MyObject> mappedObjects = new List<MyObject>(); // do stuff to map the CmsDataItems to MyObjects return mappedObjects; } private static IEnumerable<CmsDataItem> GetCmsDataItems() { List<CmsDataItem> cmsDataItems = new List<CmsDataItem>(); // do stuff to get the CmsDataItems I want return cmsDataItems; } Multiple calls from one method public void MainMethodWhereIDoStuff() { IEnumerable<CmsDataItem> cmsDataItems = GetCmsDataItems(); IEnumerable<MyObject> myObjects = GetMyObjects(cmsDataItems); // do stuff with myObjects } private static IEnumerable<MyObject> GetMyObjects(IEnumerable<CmsDataItem> itemsToMap) { // ... } private static IEnumerable<CmsDataItem> GetCmsDataItems() { // ... } I am tempted to say that the latter is better than the former, as GetMyObjects does not depend on GetCmsDataItems, and it is explicit in the calling method the steps that are executed to retrieve the objects (I'm concerned that the first approach is kind of an object-oriented version of spaghetti code). On the other hand, the two helper methods are never going to be used outside of the class, so I'm not sure if it really matters whether one depends on the other. Furthermore, I like the fact that in the first approach the objects can be retrieved from one line-- most likely anyone working with the main method doesn't care how the objects are retrieved, they just need to retrieve the objects, and the "daisy chained" helper methods hide the exact steps needed to retrieve them (in practice, I actually have a few more methods but am still able to retrieve the object collection I want in one line). Is one of these methods right and the other wrong? Or is it simply a matter of preference or context dependent?

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  • Security in a private web service

    - by Oni
    I am developing a web site and a web service for a small on-line game. Technically, I'll be using Express (node.js) and MongoDB+Redis for the databases. This the structure I came up with: One Express server that will server as the Web Service. This will connect to the databases. One Express server that will provide the web site. It will connect to the Web Service to retrieve and push the information. iOS and Android application will be able to interact with the WebService. Taking into account: It is a small game. The information transferred is not critical. There will NOT be third party applications. At least for the moment. My concern is about which level of security I should use in each of the scenarios: Security of the user playing through web browser Security of the applications and the Web Server connecting to the WS. I have take a look at the different options and: OAuth and/or Https is too much for this scenario, isn't it? Will be a good option to hash the user and password with MD5(or similar) and some salt? I would like to get some directions and investigate by my own rather than getting a response like "you should you use this node.js module..." Thanks in advance,

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  • what is best book to learn optimized programming in java [closed]

    - by Abhishek Simon
    Possible Duplicate: Is there a canonical book for learning Java as an experienced developer? Let me elaborate a little: I used to be a C/C++ programmer where I used data structure concept like trees, queues stack etc and tried to optimize as much as possible, minimum no. of loops, variables and tried to make it efficient. It's been a couple of years that I started writing java codes, but it is simply not that efficient in terms of performance, memory intensive etc. To the point: I want to enter programming challenges using java so I need to improve my approach at things I program. So please suggest me some books that can help me learn to program better and have a chance in solving challenges in programming.

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  • Which Java web framework do you recommend for intranet webapp (not content website)?

    - by pregzt
    I'm about to start development of small purpose build intranet web application for small software vendor. It will be administration console of the server managing licenses for off-the-shelf software installed by users. There will be a few users who need to be able to sign in, issue a batch of license codes, revoke some, renew outdated, resolve issues, etc. Bear in mind that my customer requires Java for this solution. I'm seasoned Java programmer and before I used different frameworks to implement webapps, mainly Apache Struts in the past and Spring MVC recently. I was wondering what else could you recommend for such specific intranet webapp. I looked at using Google Web Toolkit (possibly with SmartGWT) Ext JS for fancy widgets in UI and REST back-end in SpringMVC SpringMVC with JQueryUI Could you please think of any piece of recommendation with regard to the choice I'm going to made?

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  • HTML Parsing for multiple input files using java code [closed]

    - by mkp
    FileReader f0 = new FileReader("123.html"); StringBuilder sb = new StringBuilder(); BufferedReader br = new BufferedReader(f0); while((temp1=br.readLine())!=null) { sb.append(temp1); } String para = sb.toString().replaceAll("<br>","\n"); String textonly = Jsoup.parse(para).text(); System.out.println(textonly); FileWriter f1=new FileWriter("123.txt"); char buf1[] = new char[textonly.length()]; textonly.getChars(0,textonly.length(),buf1,0); for(i=0;i<buf1.length;i++) { if(buf1[i]=='\n') f1.write("\r\n"); f1.write(buf1[i]); } I've this code but it is taking only one file at a time. I want to select multiple files. I've 2000 files and I've given them numbering name from 1 to 2000 as "1.html". So I want to give for loop like for(i=1;i<=2000;i++) and after executing separate txt file should be generated.

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  • Don Knuth and MMIXAL vs. Chuck Moore and Forth -- Algorithms and Ideal Machines -- was there cross-pollination / influence in their ideas / work?

    - by AKE
    Question: To what extent is it known (or believed) that Chuck Moore and Don Knuth had influence on each other's thoughts on ideal machines, or their work on algorithms? I'm interested in citations, interviews, articles, links, or any other sort of evidence. It could also be evidence of the form of A and B here suggest that Moore might have borrowed or influenced C and D from Knuth here, or vice versa. (Opinions are of course welcome, but references / links would be better!) Context: Until fairly recently, I have been primarily familiar with Knuth's work on algorithms and computing models, mostly through TAOCP but also through his interviews and other writings. However, the more I have been using Forth, the more I am struck by both the power of a stack-based machine model, and the way in which the spareness of the model makes fundamental algorithmic improvements more readily apparent. A lot of what Knuth has done in fundamental analysis of algorithms has, it seems to me, a very similar flavour, and I can easily imagine that in a parallel universe, Knuth might perhaps have chosen Forth as his computing model. That's the software / algorithms / programming side of things. When it comes to "ideal computing machines", Knuth in the 70s came up with the MIX computer model, and then, collaborating with designers of state-of-the-art RISC chips through the 90s, updated this with the modern MMIX model and its attendant assembly language MMIXAL. Meanwhile, Moore, having been using and refining Forth as a language, but using it on top of whatever processor happened to be in the computer he was programming, began to imagine a world in which the efficiency and value of stack-based programming were reflected in hardware. So he went on in the 80s to develop his own stack-based hardware chips, defining the term MISC (Minimal Instruction Set Computers) along the way, and ending up eventually with the first Forth chip, the MuP21. Both are brilliant men with keen insight into the art of programming and algorithms, and both work at the intersection between algorithms, programs, and bare metal hardware (i.e. hardware without the clutter of operating systems). Which leads me to the headlined question... Question:To what extent is it known (or believed) that Chuck Moore and Don Knuth had influence on each other's thoughts on ideal machines, or their work on algorithms?

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  • Learning Asynchronous programming

    - by xenoterracide
    Asynchronous non-blocking event driven programming seems to be all the rage. I have a basic conceptual understanding of what this all means. However what I'm not sure is when and where my code can benefit from being asynchronous, or how to make blocking IO, non-blocking. I'm sure that I can simply use a library to do this, but I'm more interested in more in depth concepts, and the various ways to implement it myself. Are there any comprehensive/definitive books, or other resources on this subject (like GoF for Design Patterns, or K&R for C, tldp for things like bash)? (Note: I'm not sure if this is actually functionally an identical question to my question on Learning event driven programming)

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  • Codeigniter Open Source Applications for Coding References

    - by Hafizul Amri
    I choose codeigniter to be my first framework to work with. Now I'm looking for open source applications built based on this framework to be my references for good coding practices and standards. From my previous experiences in application development, it was hard for me to maintain, upgrade, or modify existing applications due to my bad coding practices. Do you have any suggestion of application based on codeigniter framework for me to be referred? So that it can help me to write better coding by referring to their good and maybe best coding pratices. Thank you!

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  • Constructor vs setter validations

    - by Jimmy
    I have the following class : public class Project { private int id; private String name; public Project(int id, String name, Date creationDate, int fps, List<String> frames) { if(name == null ){ throw new NullPointerException("Name can't be null"); } if(id == 0 ){ throw new IllegalArgumentException("id can't be zero"); } this.name = name; this.id = id; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } } I have three questions: Do I use the class setters instead of setting the fields directly. One of the reason that I set it directly, is that in the code the setters are not final and they could be overridden. If the right way is to set it directly and I want to make sure that the name filed is not null always. Should I provide two checks, one in the constructor and one in the setter. I read in effective java that I should use NullPointerException for null parameters. Should I use IllegalArgumentException for other checks, like id in the example.

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  • Why should I use Zend_Application?

    - by Billy ONeal
    I've been working on a Zend Framework application which currently does a bunch of things through Zend Application and a few resource plugins written for it. However, looking at this codebase now, it seems to me that using Zend_Application just makes things more complicated; and a plain, more "traditional" bootstrap file would do a better job of being transparent. This is even more the case because the individual components of Zend -- Zend_Controller, Zend_Navigation, etc. -- don't reference Zend_Application at all. Therefore they do things like "Well just call setRoute and be on your way," and the user is left scratching their head as to how to implement that in terms of the application.ini configuration file. This is not to say that one can't figure out what's going on by doing spelunking through the ZF source code. My problem with that approach is that it's to easy to depend on something that's an implementation detail, rather than a contract, and that all it seems to do is add an extra layer of indirection that one must wade through to understand an application. I look at pre ZF 1.8 example code, before Zend_Application existed, and everywhere I see plain bootstrap files that setup the MVC framework and get on their way. The code is clear and easy to understand, even if it is a bit repetitive. I like the DRY concept that Application gets you, but particularly when I'm assuming first people looking at the app's code aren't really familiar with Zend at all, I'm considering blowing away any dependence I have on Zend_Application and returning to a traditional bootstrap file. Now, my concern here is that I don't have much experience doing this, and I don't want to get rid of Zend_Application if it does something particularly important of which I am unaware, or something of that nature. Is there a really good reason I should keep it around?

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  • Using XML as data storage

    - by Kian Mayne
    I was thinking about the XML format and the following quote: “XML is not a database. It was never meant to be a database. It is never going to be a database. Relational databases are proven technology with more than 20 years of implementation experience. They are solid, stable, useful products. They are not going away. XML is a very useful technology for moving data between different databases or between databases and other programs. However, it is not itself a database. Don't use it like one.“ -Effective XML: 50 Specific Ways to Improve Your XML by Elliotte Rusty Harold (page 230, Part 4, Item 41, 2nd paragraph) This seems to really stress that XML should not be used for data storage and should only be used for program to program interoperability. Personally, I disagree and .NET's app.config file that's used to store a program's settings is an example of data storage in an XML file. However for databases rather than configurations etc XML should not be used. To develop my point, I will use two examples: A) Data about customers with fields that are all on one level i.e. there are a number of fields all relating to one customer with no children B) Data about configuration of an application where nested fields and properties make a lot of sense So my question is, Is this still a valid statement and is it now acceptable to store data using XML? EDIT: I've sent an email to the author of that quote to ask for his input/extra context.

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  • How to document/verify consistent layering?

    - by Morten
    I have recently moved to the dark side: I am now a CUSTOMER of software development -- mainly websites. With this new role comes new concerns. As a programmer i know how solid an application becomes when it is properly layered, and I want to use this knowledge in my new job. I don't want business logic in my presentation layer, and certainly not presentation stuff in my data layer. Thus, I want to be able to demand from my supllier that they document the level of layering, and how neat and consistent the layering is. The big question is: How is the level of layering documented to me as a customer, and is that a reasonable demmand for me to have, so I don't have to look in the code (I'm not supposed to do that anymore)?

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  • Optimizing hash lookup & memory performance in Go

    - by Moishe
    As an exercise, I'm implementing HashLife in Go. In brief, HashLife works by memoizing nodes in a quadtree so that once a given node's value in the future has been calculated, it can just be looked up instead of being re-calculated. So eg. if you have a node at the 8x8 level, you remember it by its four children (each at the 2x2 level). So next time you see an 8x8 node, when you calculate the next generation, you first check if you've already seen a node with those same four children. This is extended up through all levels of the quadtree, which gives you some pretty amazing optimizations if eg. you're 10 levels above the leaves. Unsurprisingly, it looks like the perfmance crux of this is the lookup of nodes by child-node values. Currently I have a hashmap of {&upper_left_node,&upper_right_node,&lower_left_node,&lower_right_node} -> node So my lookup function is this: func FindNode(ul, ur, ll, lr *Node) *Node { var node *Node var ok bool nc := NodeChildren{ul, ur, ll, lr} node, ok = NodeMap[nc] if ok { return node } node = &Node{ul, ur, ll, lr, 0, ul.Level + 1, nil} NodeMap[nc] = node return node } What I'm trying to figure out is if the "nc := NodeChildren..." line causes a memory allocation each time the function is called. If it does, can I/should I move the declaration to the global scope and just modify the values each time this function is called? Or is there a more efficient way to do this? Any advice/feedback would be welcome. (even coding style nits; this is literally the first thing I've written in Go so I'd love any feedback)

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  • Is it normal needing time to understand code i wrote recently

    - by user1478167
    By recently i mean some weeks ago. I am trying to continue a project i left 2 weeks ago and i need time to understand some functions i wrote(not copied from somewhere) and it takes me time. Normally i don't need to because my functions,methods etc are black boxes but when i need to change something it's really hard. Does this mean i write bad code? I am still in school and i am the only who writes/uses the code so i don't have feedback, but i am afraid that if it is difficult for me to understand it, it would be 10 times more difficult for someone else. What should i do? I write a lot of comments but most of the time are useless when reviewing. Do you have any suggestions?

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  • Objective C and ios development training courses feedback

    - by Mutuelinvestor
    I'm thinking about taking an Objective C / iphone/ipad development training course. Pragmatic Studio and Big Nerd Ranch appear to be the key players. I'd love to hear any feed back from anyone who has completed training with Pragmatic, Big Nerd or others. I'd interested in quality of instruction, how much you learned, strengths, weaknesses and any other valuable insights. Its a pretty big financial commitment for me and I want to get the most bang for my buck. Thanks in advance for your input.

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  • How to store generated eigen faces for future face recognition?

    - by user3237134
    My code works in the following manner: 1.First, it obtains several images from the training set 2.After loading these images, we find the normalized faces,mean face and perform several calculation. 3.Next, we ask for the name of an image we want to recognize 4.We then project the input image into the eigenspace, and based on the difference from the eigenfaces we make a decision. 5.Depending on eigen weight vector for each input image we make clusters using kmeans command. Source code i tried: clear all close all clc % number of images on your training set. M=1200; %Chosen std and mean. %It can be any number that it is close to the std and mean of most of the images. um=60; ustd=32; %read and show images(bmp); S=[]; %img matrix for i=1:M str=strcat(int2str(i),'.jpg'); %concatenates two strings that form the name of the image eval('img=imread(str);'); [irow icol d]=size(img); % get the number of rows (N1) and columns (N2) temp=reshape(permute(img,[2,1,3]),[irow*icol,d]); %creates a (N1*N2)x1 matrix S=[S temp]; %X is a N1*N2xM matrix after finishing the sequence %this is our S end %Here we change the mean and std of all images. We normalize all images. %This is done to reduce the error due to lighting conditions. for i=1:size(S,2) temp=double(S(:,i)); m=mean(temp); st=std(temp); S(:,i)=(temp-m)*ustd/st+um; end %show normalized images for i=1:M str=strcat(int2str(i),'.jpg'); img=reshape(S(:,i),icol,irow); img=img'; end %mean image; m=mean(S,2); %obtains the mean of each row instead of each column tmimg=uint8(m); %converts to unsigned 8-bit integer. Values range from 0 to 255 img=reshape(tmimg,icol,irow); %takes the N1*N2x1 vector and creates a N2xN1 matrix img=img'; %creates a N1xN2 matrix by transposing the image. % Change image for manipulation dbx=[]; % A matrix for i=1:M temp=double(S(:,i)); dbx=[dbx temp]; end %Covariance matrix C=A'A, L=AA' A=dbx'; L=A*A'; % vv are the eigenvector for L % dd are the eigenvalue for both L=dbx'*dbx and C=dbx*dbx'; [vv dd]=eig(L); % Sort and eliminate those whose eigenvalue is zero v=[]; d=[]; for i=1:size(vv,2) if(dd(i,i)>1e-4) v=[v vv(:,i)]; d=[d dd(i,i)]; end end %sort, will return an ascending sequence [B index]=sort(d); ind=zeros(size(index)); dtemp=zeros(size(index)); vtemp=zeros(size(v)); len=length(index); for i=1:len dtemp(i)=B(len+1-i); ind(i)=len+1-index(i); vtemp(:,ind(i))=v(:,i); end d=dtemp; v=vtemp; %Normalization of eigenvectors for i=1:size(v,2) %access each column kk=v(:,i); temp=sqrt(sum(kk.^2)); v(:,i)=v(:,i)./temp; end %Eigenvectors of C matrix u=[]; for i=1:size(v,2) temp=sqrt(d(i)); u=[u (dbx*v(:,i))./temp]; end %Normalization of eigenvectors for i=1:size(u,2) kk=u(:,i); temp=sqrt(sum(kk.^2)); u(:,i)=u(:,i)./temp; end % show eigenfaces; for i=1:size(u,2) img=reshape(u(:,i),icol,irow); img=img'; img=histeq(img,255); end % Find the weight of each face in the training set. omega = []; for h=1:size(dbx,2) WW=[]; for i=1:size(u,2) t = u(:,i)'; WeightOfImage = dot(t,dbx(:,h)'); WW = [WW; WeightOfImage]; end omega = [omega WW]; end % Acquire new image % Note: the input image must have a bmp or jpg extension. % It should have the same size as the ones in your training set. % It should be placed on your desktop ed_min=[]; srcFiles = dir('G:\newdatabase\*.jpg'); % the folder in which ur images exists for b = 1 : length(srcFiles) filename = strcat('G:\newdatabase\',srcFiles(b).name); Imgdata = imread(filename); InputImage=Imgdata; InImage=reshape(permute((double(InputImage)),[2,1,3]),[irow*icol,1]); temp=InImage; me=mean(temp); st=std(temp); temp=(temp-me)*ustd/st+um; NormImage = temp; Difference = temp-m; p = []; aa=size(u,2); for i = 1:aa pare = dot(NormImage,u(:,i)); p = [p; pare]; end InImWeight = []; for i=1:size(u,2) t = u(:,i)'; WeightOfInputImage = dot(t,Difference'); InImWeight = [InImWeight; WeightOfInputImage]; end noe=numel(InImWeight); % Find Euclidean distance e=[]; for i=1:size(omega,2) q = omega(:,i); DiffWeight = InImWeight-q; mag = norm(DiffWeight); e = [e mag]; end ed_min=[ed_min MinimumValue]; theta=6.0e+03; %disp(e) z(b,:)=InImWeight; end IDX = kmeans(z,5); clustercount=accumarray(IDX, ones(size(IDX))); disp(clustercount); QUESTIONS: 1.It is working fine for M=50(i.e Training set contains 50 images) but not for M=1200(i.e Training set contains 1200 images).It is not showing any error.There is no output.I waited for 10 min still there is no output. I think it is going infinite loop.What is the problem?Where i was wrong? 2.Instead of running the training set everytime how eigen faces generated are stored so that stored eigen faces are used for future face recoginition for a new input image.So it reduces wastage of time.

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  • Most efficient way to rebuild a tree structure from data

    - by Ahsan
    Have a question on recursively populating JsTree using the .NET wrapper available via NuGet. Any help would be greatly appreciated. the .NET class JsTree3Node has a property named Children which holds a list of JsTree3Nodes, and the pre-existing table which contains the node structure looks like this NodeId ParentNodeId Data AbsolutePath 1 NULL News /News 2 1 Financial /News/Financial 3 2 StockMarket /News/Financial/StockMarket I have a EF data context from the the database, so my code currently looks like this. var parentNode = new JsTree3Node(Guid.NewGuid().ToString()); foreach(var nodeItem in context.Nodes) { parentNode.Children.Add(nodeItem.Data); // What is the most efficient logic to do this recursively? } as the inline comment says in the above code, what would be the most efficient way to load the JStree data on to the parentNode object. I can change the existing node table to suite the logic so feel free to suggest any changes to improve performance.

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  • Should each app have its own database, or should small apps be merged into one?

    - by King
    We have a bunch of small to medium sized apps, each of which has its own database (MSSQL Server). There was a suggestion that we consoldate the 'related' databases into a smaller set amount of larger databases. They don't particularly share a lot of data, they would just be under a similar business group. For example, using a 'Finance' DB to hold the tables and procedures for finance apps. Would it be appropriate to use a different schema for each app? E.g. App1.SomeTable App1.SomeOtherTable AppTwo.SomeTable What are the pros and cons of this approach? What should I watch out for? Thanks

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  • Should I organize my folders by business domain or by technical domain?

    - by Florian Margaine
    For example, if I'm using some MVC-like architecture, which folder structure should I use: domain1/ controller model view domain2/ controller model view Or: controllers/ domain1 domain2 models/ domain1 domain2 views/ domain1 domain2 I deliberately left out file extensions to keep this question language-agnostic. Personally, I'd prefer to separate by business domain (gut feeling), but I see that most/many frameworks separate by technical domain. Why whould I choose one over the other?

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