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  • Http post with basic authorization don't work in java

    - by glebreutov
    This code work without exceptions but post request does not work. What I do wrong? I use Java 1.6, JBoss 4.2.3 String xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" + "<message><service id=\"210\"/><to>+"+phone+"</to>" + "<body content-type=\"text/plain\">"+message+"</body></message>"; String userPassword = "login:password"; URL url = new URL(ksGateUrl); URLConnection urlc = url.openConnection(); urlc.setDoOutput(true); urlc.setUseCaches(false); urlc.setAllowUserInteraction(false); urlc.setRequestProperty("Authorization", "Basic " + new sun.misc.BASE64Encoder().encode (userPassword.getBytes())); OutputStreamWriter wr = new OutputStreamWriter(urlc.getOutputStream(), "UTF-8"); wr.write(xml); wr.flush();

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  • Forwarding HTTP Request with Direct Server Return

    - by Daniel Crabtree
    I have servers spread across several data centers, each storing different files. I want users to be able to access the files on all servers through a single domain and have the individual servers return the files directly to the users. The following shows a simple example: 1) The user's browser requests http://www.example.com/files/file1.zip 2) Request goes to server A, based on the DNS A record for example.com. 3) Server A analyzes the request and works out that /files/file1.zip is stored on server B. 4) Server A forwards the request to server B. 5) Server B returns file1.zip directly to the user without going through server A. Note: steps 4 and 5 must be transparent to the user and cannot involve sending a redirect to the user as that would violate the requirement of a single domain. From my research, what I want to achieve is called "Direct Server Return" and it is a common setup for load balancing. It is also sometimes called a half reverse proxy. For step 4, it sounds like I need to do MAC Address Translation and then pass the request back onto the network and for servers outside the network of server A tunneling will be required. For step 5, I simply need to configure server B, as per the real servers in a load balancing setup. Namely, server B should have server A's IP address on the loopback interface and it should not answer any ARP requests for that IP address. My problem is how to actually achieve step 4? I have found plenty of hardware and software that can do this for simple load balancing at layer 4, but these solutions fall short and cannot handle the kind of custom routing I require. It seems like I will need to roll my own solution. Ideally, I would like to do the routing / forwarding at the web server level, i.e. in PHP or C# / ASP.net. However, I am open to doing it at a lower level such as Apache or IIS, or at an even lower level, i.e. a custom proxy service in front of everything.

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  • Write transparent HTTP Proxy script in PHP

    - by Leo Izen
    Is there an easy forwarding/transparent php proxy script that I can host on my web server? These are my conditions: I'm using free web hosting, so I have pretty much no control over my machine. Otherwise I could use Perl's HTTP::Proxy module. This means no root password. It does run php though. I already have a server running on port 80. What I mean is I would like to put a php script as index.php on my server that will forward all requests. I don't want a script like PHProxy or Glype where I go to the site, then enter a URL. I want a server so I can enter proxy.example.com:80 in Firefox's or IE's or whatever's proxy settings and it will forward all requests to the server. Preferably (though not fatal if not possible) I would like for it to pass on the USER_AGENT environmental variable (That's the browser) instead of setting itself to be the USER_AGENT I can't start a new Daemon. My server won't allow it. Is there a script that will do this? If so, which?

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  • QR Codes for Files on Google Code

    - by Synetech inc.
    Hi, When you download files from Google Code now (example), in addition to the text version of the SHA1 hash, it includes a QR code of it. The device that the file was downloaded to is the one that has to hash the file. But, if it can download the file (ie, has access to the webpage), it also has access to the text version of the hash, so the QR code seems completely useless—and more work to decode when the raw text is available. How would reading the hash into a mobile phone allow you to verify the file you download to the computer? Or if you download the file to the phone, how would you use the phone to take a picture of the QR code displayed on the webpage on its own screen? Does anyone know what the point to the QR code is or how you would use it to verify the downloaded file (I don’t mean QR codes in general, but specifically in this context).

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  • What to watch out for when writing code at an Interview?

    - by Philip
    Hi, I have read that at a lot of companies you have to write code at an interview. On the one hand I see that it makes sense to ask for a work sample. On the other hand: What kind of code do you expect to be written in 5 minutes? And what if they tell me "Write an algorithm that does this and that" but I cannot think of a smart solution or even write code that doesn't semantically work? I am particularly interested in that question because I do not have that much commercial programming experience, 2 years part-time, one year full-time. (But I am interested in programming languages since nearly 15 years though usually I was more concentrated in playing with the language rather than writing large applications...) And actually I consider my debugging and problem solving skills much better than my coding skills. I sometimes see myself not writing the most beautiful code when looking back, but on the other hand I often come up with solutions for hard problems. And I think I am very good at optimizing, fixing, restructuring existing code, but I have problems with writing new applications from scratch. The software design sucks... ;-) Therefore I don't feel comfortable when thinking about this code writing situation at an interview... So what do the interviewers expect? What kind of information about my code writing are they interested in? Philip

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  • Configuring Oracle HTTP Server 12c for WebLogic Server Domain

    - by Emin Askerov
    Oracle HTTP Server (OHS) 12c 12.1.2 which was released in July 2013 as a part of Oracle Web Tier 12c is the web server component of Oracle Fusion Middleware. In essence this is Apache HTTP Server 2.2.22 (with critical bug fixes from higher versions) which includes modules developed specifically by Oracle. It provides a listener functionality for Oracle WebLogic Server and the framework for hosting static pages, dynamic pages, and applications over the Web. OHS can be easily managed by Weblogic Management Framework, a set of tools which provides administrative capabilities (start, stop, lifecycle operations, etc.) for Oracle Fusion Middleware products. In other words all tools which are familiar to us (Node Manager, WLST, Administration Console, Fusion Middleware Control etc.) presented as a part of Weblogic Management Framework and using for managing Java and System Components both for Weblogic Server and Standalone Domain types. You can familiarize yourself with these terms using related documentation: 1. Introduction to Oracle HTTP Server: http://docs.oracle.com/middleware/1212/webtier/index.html 2. Weblogic Management Framework: http://docs.oracle.com/middleware/1212/core/ASCON/terminology.htm#ASCON11260 In the given post I would like to cover rather simple use case how to configure OHS as web proxy in Weblogic Cluster environment. For example, we have existing Weblogic Domain where some managed servers have been joined to cluster and host business applications. We need to configure web proxy component which will act as entry point, load balancer for our cluster for user requests. Of course, we could install old good Apache HTTP Server and configure mod_wl plugin. However this solution not optimal from manageability perspective: we need to install Apache, install additional plugin then configure it by editing configuration file which is not really convenient for FMW Administrators and often increase time of performing of simple administrative task. Alternatively, we could use OHS as System Component within Weblogic Domain and use full power of Weblogic Management Framework in order to configure, manage and monitor it! I like this idea! What about you? I hope after reading this post you will agree with me. First of all it is necessary to download OHS binaries. You can use this link for downloading: http://www.oracle.com/technetwork/java/webtier/downloads/index2-303202.html As we will use Fusion Middleware Control for managing OHS instances it is necessary to extend your domain with Enterprise Manager and Oracle ADF and JRF templates. This is not topic for focusing in this post, but you could get more information from documentation or one of my previous posts: http://docs.oracle.com/middleware/1212/wls/WLDTR/fmw_templates.htm#sthref64 https://blogs.oracle.com/imc/entry/the_specifics_of_adf_12c Note: you should have properly configured Node Manager utility for managing OHS instances Let’s consider configuration process step by step: 1. Shut down all Weblogic instances of existing domain including Admin Server; 2. Install Oracle HTTP Server. You should use your Fusion Middleware Home Path (e.g. /u01/Oracle/FMW12) for Installation Location and select Colocated HTTP Server option as Installation Type. I will not focus on this topic in this post. All information related to OHS installation you could find here: http://docs.oracle.com/middleware/1212/webtier/WTINS/install_gui.htm#i1082009 3. Next we need to extend our existing domain with OHS component. In order to do this you should do the following: a. Run Fusion Middleware Configuration Wizard (ORACLE_HOME/oracle_common/common/bin/config.sh); b. On the step 1 select Update an existing domain option and point your Fusion Middleware Home Path; c. On the step 2 check Oracle HTTP Server, Oracle Enterprise Manager Plugin for WEBTIER templates; d. Go through other steps without any changes and finish configuration process. 4. Start Admin Server and all managed servers related to your cluster 5. Log in to Enterprise Manager FMW Control using http://<hostname>:<port>/em URL 6. Now we will create OHS instance within our Weblogic Domain Infrastructure. Navigate to Weblogic Domain -> Administration -> Create/Delete OHS menu item; 7. Enter to edit mode, clicking Changes -> Lock&Edit menu item; 8. Create new OHS instance clicking Create button; 9. Define Instance Name (e.g. DevOSH) and Machine parameters; 10. Now we need to define listen port. By default OHS will use 7777 port number for income HTTP requests. We could change it to any free port number we would like to use. In order to do it, right click on our created OHS instance (left hand panel) and navigate to Administration -> Port Configuration; 11. Click on record with port number 7777 and then click Edit button; 12. Change port number value (in our case this will be 8080) and then click OK button; 13. Now we need to edit mod_wl_ohs configuration in order to enable OHS to act as proxy for WebLogic Server Instances/Cluster; 14. In order to do it right click on our created OHS instance (left panel) and navigate to Administration -> mod_wl_ohs Configuration; a. In Weblogic Cluster you should enter cluster address (define <host:port> for all managed servers which participated in cluster), e.g: 192.168.56.2:7004,192.168.56.2:7005 b. Define Weblogic Port parameter at which the Oracle WebLogic Server host is listening for connection requests from the module (or from other servers); c. Check Dynamic Server List option. This will dynamically update cluster list for every request; d. In the Location table define list of endpoint locations which you would like to process. In order to do this click Add Row button and define Location, Weblogic Cluster, Path Trim and Path Prefix parameters (if required); e. Click Apply button in order to save changes. 15. Activate changes clicking Changes ? Activate Changes menu item; 16. Finally we will start configured OHS instance. Right click on OHS instance tree item under Web Tier folder, select Control -> Start Up menu item; 17. Ensure that OHS instance up and running and then test your environment. Run deployed application to your Weblogic Cluster accessing via OHS web proxy; Normal 0 false false false RU X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-fareast-language:EN-US;}

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  • Rawr Code Clone Analysis&ndash;Part 0

    - by Dylan Smith
    Code Clone Analysis is a cool new feature in Visual Studio 11 (vNext).  It analyzes all the code in your solution and attempts to identify blocks of code that are similar, and thus candidates for refactoring to eliminate the duplication.  The power lies in the fact that the blocks of code don't need to be identical for Code Clone to identify them, it will report Exact, Strong, Medium and Weak matches indicating how similar the blocks of code in question are.   People that know me know that I'm anal enthusiastic about both writing clean code, and taking old crappy code and making it suck less. So the possibilities for this feature have me pretty excited if it works well - and thats a big if that I'm hoping to explore over the next few blog posts. I'm going to grab the Rawr source code from CodePlex (a World Of Warcraft gear calculator engine program), run Code Clone Analysis against it, then go through the results one-by-one and refactor where appropriate blogging along the way.  My goals with this blog series are twofold: Evaluate and demonstrate Code Clone Analysis Provide some concrete examples of refactoring code to eliminate duplication and improve the code-base Here are the initial results:   Code Clone Analysis has found: 129 Exact Matches 201 Strong Matches 300 Medium Matches 193 Weak Matches Also indicated is that there was a total of 45,181 potentially duplicated lines of code that could be eliminated through refactoring.  Considering the entire solution only has 109,763 lines of code, if true, the duplicates lines of code number is pretty significant. In the next post we’ll start examining some of the individual results and determine if they really do indicate a potential refactoring.

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  • How do you stay productive when dealing with extremely badly written code?

    - by gaearon
    I don't have much experience in working in software industry, being self-taught and having participated in open source before deciding to take a job. Now that I work for money, I also have to deal with some unpleasant stuff, which is normal of course. Recently I was assigned to add logging to a large SharePoint project which is written by some programmer who obviously was learning to code on the job. After 2 years of collaboration, the client switched to our company, but the damage was done, and now somehow I need to maintain this code. Not that the code was too hard to read. Despite problems - each project has one class with several copy-pasted methods, enormous if nestings, Systems Hungarian, undisposed connections — it's still readable. However, I found myself absolutely unproductive despite working on something as simple as adding logging. Basically, I just need to go through the code step by step and add some trace calls. However, the idiocy of the code is so annoying that I get tired within 10 minutes of starting. In the beginning, I used to add using constructs, reduce nesting by reversing if's, rename the variables to readable names—but the project is large, and eventually I gave up. I know this is not the task I should be doing, but at least reducing the mess gave me some kind of psychological reward so I could keep going. Now the trick stopped working, and I still have 60% of my work to do. I started having headaches after work, and I no longer get the feeling of satisfaction I used to get - which would usually allow me to code for 10 hours straight and still feel fresh. This is not just one big rant, for I really do have an actual question: Is there a way to stay productive and not to fight the windmills? Is there some kind of psychological trick to stay focused on the task, instead of thinking “How stupid is that?” each time I see another clever trick by the previous programmer? The problem with adding logging is that I actually have to understand what the code does, and doing so hurts my brain in an unpleasant fashion.

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  • Which reference provides your definition of "elegant" or "beautiful" code?

    - by Donnied
    This question is phrased in a very specific way - it asks for references. There was a similar question posted which was closed because it was considered a duplicate to a good code question. The Programmers FAQ points out that answers should have references - or its just an unproductive sharing of (seemingly) baseless opinions. There is a difference between shortest code and most elegant code. This becomes clear in several seminal texts: Dijkstra, E. W. (1972). The humble programmer. Communications of the ACM, 15(10), 859–866. Kernighan, B. W., & Plauger, P. J. (1974). Programming style: Examples and counterexamples. ACM Comput. Surv., 6(4), 303–319. Knuth, D. E. (1984). Literate programming. The Computer Journal, 27(2), 97–111. doi:10.1093/comjnl/27.2.97 They all note the importance of clarity over brevity. Kernighan & Plauger (1974) provide descriptions of "good" code, but "good code" is certainly not synonymous with "elegant". Knuth (1984) describes the impo rtance of exposition and "excellence of style" to elegant programs. He cites Hoare - who describes that code should be self documenting. Dijkstra (1972) indicates that beautiful programs optimize efficiency but are not opaque. This sort of conversation is qulaitatively different than a random sharing of opinions. Therefore, the question - Which reference provides your definition of "elegant" or "beautiful" code? "Which *reference*" is not subjective - anything else will most likely shut the thread down, so please supply *references* not opinions.

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  • How would you react if someone told you your code is a mess?

    - by newbie
    I am a good programmer, or so I thought before. I always love to program. And I want to learn many things about programming to make me a better programmer. I studied programming for 1 year and now I am working as a programmer for almost 2 years. So in short, I have almost 3 years programming experience. Our team is composed of 5 programmers, and 4 of us are new, 1 has more than 3 year experience. We've been working for a program for almost a year now and nobody ever review my code and I was given a page to work with. We never had a code review and we are all new so we don't know what is a clean code looks like. I think programmers learn by themselves? We deployed our program to the program without thorough testing. Now it is tight and we need an approval and code review first before we make changes with the code. For the first time, someone reviews my code and he says it is a mess. I feel so sad and hurt. I really love programming and making them say something like that really hurts me. I really want to improve myself. But it seems like I'm not a genius programmer like in the movies. Can you give me advise on how to be better? Have you ever experience something criticizing your code and you feel really hurt? What do you do on those events.. Thank you

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  • Copy-and-Pasted Test Code: How Bad is This?

    - by joshin4colours
    My current job is mostly writing GUI test code for various applications that we work on. However, I find that I tend to copy and paste a lot of code within tests. The reason for this is that the areas I'm testing tend to be similar enough to need repetition but not quite similar enough to encapsulate code into methods or objects. I find that when I try to use classes or methods more extensively, tests become more cumbersome to maintain and sometimes outright difficult to write in the first place. Instead, I usually copy a big chunk of test code from one section and paste it to another, and make any minor changes I need. I don't use more structured ways of coding, such as using more OO-principles or functions. Do other coders feel this way when writing test code? Obviously I want to follow DRY and YAGNI principles, but I find that test code (automated test code for GUI testing anyway) can make these principles tough to follow. Or do I just need more coding practice and a better overall system of doing things? EDIT: The tool I'm using is SilkTest, which is in a proprietary language called 4Test. As well, these tests are mostly for Windows desktop applications, but I also have tested web apps using this setup as well.

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  • Authenticating to Google Search Appliance using Basic HTTP auth and ASP.NET (VB)

    - by Chainlink
    I've run into a snag though which has to do with authentication between the Google Search Appliance and ASP. Normally, when asking for secure pages from the search appliance, the search appliance asks for credentials, then uses these credentials to try and access the secure results. If this attempt is successful, the page shows up in the results list. Since ASP is contacting the search appliance on the client's behalf, it will need to collect credentials and pass them along to the search appliance. I have tried a couple of different documented ways of accomplishing this, but they don't seem to work. Below is the code I have tried: 'Bypass SSL since discovery.gov.mb.ca does not have valid SSL cert (NOT PRODUCTION SAFE) ServerCertificateValidationCallback = New System.Net.Security.RemoteCertificateValidationCallback(AddressOf customXertificateValidation) googleUrl = "https://removed.com" Dim rdr As New XmlTextReader(googleUrl) Dim resolver As New XmlUrlResolver() Dim myCred As New System.Net.NetworkCredential("USERNAME", "PASSWORD", Nothing) Dim credCache As New CredentialCache() credCache.Add(New Uri(googleUrl), "Basic", myCred) resolver.Credentials = credCache rdr.XmlResolver = resolver doc = New System.Xml.XPath.XPathDocument(rdr) path = doc.CreateNavigator() Private Function customXertificateValidation(ByVal sender As Object, ByVal certificate As System.Security.Cryptography.X509Certificates.X509Certificate, ByVal chain As System.Security.Cryptography.X509Certificates.X509Chain, ByVal sslPolicyErrors As Net.Security.SslPolicyErrors) As Boolean Return True End Function

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  • Custom webserver caching

    - by Mark Kinsella
    I'm working with a custom webserver on an embedded system and having some problems correctly setting my HTTP Headers for caching. Our webserver is generating all dynamic content as XML and we're using semi-static XSL files to display it with some dynamic JSON requests thrown in for good measure along with semi-static images. I say "semi-static" because the problems occur when we need to do a firmware update which might change the XSL and image files. Here's what needs to be done: cache the XSL and image files and do not cache the XML and JSON responses. I have full control over the HTTP response and am currently: Using ETags with the XSL and image files, using the modified time and size to generate the ETag Setting Cache-Control: no-cache on the XML and JSON responses As I said, everything works dandy until a firmware update when the XSL and image files are sometimes cached. I've seen it work fine with the latest versions of Firefox and Safari but have had some problems with IE. I know one solution to this problem would be simply rename the XSL and image files after each version (eg. logo-v1.1.png, logo-v1.2.png) and set the Expires header to a date in the future but this would be difficult with the XSL files and I'd like to avoid this. Note: There is a clock on the unit but requires the user to set it and might not be 100% reliable which is what might be causing my caching issues when using ETags. What's the best practice that I should employ? I'd like to avoid as many webserver requests as possible but invalidating old XSL and image files after a software update is the #1 priority.

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  • Email Tracking - GMail

    - by Abs
    Hello all, I am creating my own email tracking system for email marketing tracking. I have been able to determine each persons email client they are using by using the http referrer but for some reason GMAIL does not send a HTTP_REFERRER at all! So I am trying to find another way of identifying when gmail requests a transparent image from my server. I get the following headers print_r($_SERVER);: DOCUMENT_ROOT = /usr/local/apache/htdocs GATEWAY_INTERFACE = CGI/1.1 HTTP_ACCEPT = */* HTTP_ACCEPT_CHARSET = ISO-8859-1,utf-8;q=0.7,*;q=0.3 HTTP_ACCEPT_ENCODING = gzip,deflate,sdch HTTP_ACCEPT_LANGUAGE = en-GB,en-US;q=0.8,en;q=0.6 HTTP_CONNECTION = keep-alive HTTP_COOKIE = __utmz=156230011.1290976484.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); __utma=156230011.422791272.1290976484.1293034866.1293050468.7 HTTP_HOST = xx.xxx.xx.xxx HTTP_USER_AGENT = Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.10 (KHTML, like Gecko) Chrome/8.0.552.237 Safari/534.10 PATH = /bin:/usr/bin QUERY_STRING = i=MTA= REDIRECT_STATUS = 200 REMOTE_ADDR = xx.xxx.xx.xxx REMOTE_PORT = 61296 REQUEST_METHOD = GET Is there anything of use in that list? Or is there something else I can do to actually get the http referrer, if not how are other ESPs managing to find whether gmail was used to view an email? Btw, I appreciate it if we can hold back on whether this is ethical or not as many ESPs do this already, I just don't want to pay for their service and I want to do it internally. Thanks all for any implementation advice. Update Just thought I would update this question and make it clearer in light of the bounty. I would like to find out when a user opens my email when sent to a GMail inbox. Assume, I have the usual transparent image tracking and the user does not block images. I would like to do this with the single request and the header details I get when the transparent image is requested.

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  • This code is working properly in Dev C++ .But on Linux platform it is giving problem with the moveme

    - by srinija
    #include<stdio.h> #include<GL/glut.h> #include<stdlib.h> GLfloat v[3][24]={{100.0,300.0,350.0,50.0,100.0,120.0,120.0,100.0,260.0,280.0, 280.0,260.0,140.0,160.0,160.0,140.0,180.0,200.0,200.0,180.0, 220.0,240.0,240.0,220.0},{100.0,100.0,200.0,200.0,160.0, 160.0,180.0,180.0,160.0,160.0,180.0,180.0,160.0,160.0,180.0, 180.0,160.0,160.0,180.0,180.0,160.0,160.0,180.0,180.0}, {1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0, 1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0}}; GLfloat v1[3][16]={{50.0,350.0,350.0,50.0,100.0,300.0,300.0,100.0,125.0,175.0, 175.0,125.0,225.0,275.0,275.0,225.0},{200.0,200.0,210.0, 210.0,210.0,210.0,240.0,240.0,240.0,240.0,310.0,310.0,240.0, 240.0,310.0,310.0},{1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0,1.0, 1.0,1.0,1.0,1.0,1.0,1.0}}; GLfloat colors[4][3]={{0.0,0.0,1.0},{0.9961,0.9961,0.65625},{1.0,0.0,1.0}, {1.0,.0,1.0}}; static float q,w,e; static float fq,fw,fe; static GLfloat wa=0,wb=0,wc=0,ba,bb,bc; int flag; void myinit(void) { glClearColor(0.506,.7,1,0.0); glPointSize(2.0); glLoadIdentity(); glOrtho(0.0,499.0,0.0,499.0,-300.0,300.0); } void draw_top_boxes(GLint i,GLint j) { glColor3f(1.0,0.0,0.0); glBegin(GL_POLYGON); glColor3fv(colors[j]); // to draw the boat glVertex2f(v1[0][i+0],v1[1][i+0]); glColor3fv(colors[j+1]); glVertex2f(v1[0][i+1],v1[1][i+1]); glColor3fv(colors[j+2]); glVertex2f(v1[0][i+2],v1[1][i+2]); glColor3fv(colors[j+3]); glVertex2f(v1[0][i+3],v1[1][i+3]); glEnd(); } void draw_polygon(GLint i) { glBegin(GL_POLYGON); // to draw the boat glColor3f(0.0,0.0,0.0); glColor3fv(colors[0]); glVertex2f(v[0][i+0],v[1][i+0]); glColor3fv(colors[1]); glVertex2f(v[0][i+1],v[1][i+1]); glColor3fv(colors[2]); glVertex2f(v[0][i+2],v[1][i+2]); glColor3fv(colors[3]); glVertex2f(v[0][i+3],v[1][i+3]); glEnd(); } void draw_boat() { draw_polygon(0); draw_polygon(4); draw_polygon(8); draw_polygon(12); draw_polygon(16); draw_polygon(20); draw_top_boxes(0,0); draw_top_boxes(4,0); draw_top_boxes(8,0); draw_top_boxes(12,0); glFlush(); glPopMatrix(); glPopMatrix(); } void draw_water() { GLfloat i; GLfloat x=0,y=103,j=0; GLfloat k; glPushMatrix(); glTranslatef(wa,wb,wc); glPushMatrix(); glColor3f(0,0,1); for(k=y;k>0;k-=6) { for(i=1;i<30;i++) { glBegin(GL_LINES); glVertex2f(j,k); glVertex2f(j+10,k); glEnd(); j=j+20; } j=0; } glPopMatrix(); glPopMatrix(); } void draw_fishes() { glPushMatrix(); glTranslatef(fq,12.0,fe); glPushMatrix(); glColor3f(.99609375,0.2578125,0.2578125); glBegin(GL_TRIANGLES); glVertex2f(100,80); glVertex2f(100,60); glVertex2f(85,70); glEnd(); glColor3f(.99609375,0.2578125,0.2578125); glBegin(GL_TRIANGLES); glVertex2f(100,70); glVertex2f(110,75); glVertex2f(110,65); glEnd(); glColor3f(0,0,0); glBegin(GL_POINTS); glVertex2f(90,71); glEnd(); glColor3f(.99609375,0.2578125,0.2578125); glBegin(GL_TRIANGLES); glVertex2f(200,80); glVertex2f(200,60); glVertex2f(185,70); glEnd(); glColor3f(.99609375,0.2578125,0.2578125); glBegin(GL_TRIANGLES); glVertex2f(200,70); glVertex2f(210,75); glVertex2f(210,65); glEnd(); glColor3f(0,0,0); glBegin(GL_POINTS); glVertex2f(190,71); glEnd(); glPopMatrix(); glPopMatrix(); glFlush(); } void draw_cloud() { GLfloat m=100,n=400,o=10; for(int i=0;i<7;i++) { glPushMatrix(); glColor3f(1.0,1.0,1.0); if(i==1) glTranslated(125,415,10); else if(i==3||i==5) glTranslated(m,n+5,o); else glTranslated(m,n,o); glutSolidSphere(20.0,5000,150); glPopMatrix(); m+=10; } } void draw_square() { glColor3f(0,0.5,0.996); glBegin(GL_POLYGON); glVertex2f(0,0); glVertex2f(1000,0); glVertex2f(0,300); glVertex2f(1000,300); glEnd(); glFlush(); } void draw_brotate() { glPushMatrix(); glColor3f(0.96,0.5,0.25); //to draw body of the bird glTranslated(300,400,10); glScalef(3,1,1); glutSolidSphere(6,50000,15); glPopMatrix(); glPushMatrix(); glTranslated(323,400,10); glutSolidSphere(5,50000,15); glPopMatrix(); glColor3f(0,0,0); glBegin(GL_POINTS); glVertex2f(325,401); glEnd(); glColor3f(0.96,0.5,0.25); //to draw wings glBegin(GL_LINES); glVertex2f(294,394); glVertex2f(286,389); glEnd(); glBegin(GL_LINES); glVertex2f(286,389); glVertex2f(295,391); glEnd(); glBegin(GL_LINES); glVertex2f(295,391); glVertex2f(285,385); glEnd(); glBegin(GL_LINES); glVertex2f(285,385); glVertex2f(309,395); glEnd(); glBegin(GL_LINES); glVertex2f(294,406); glVertex2f(286,411); glEnd(); glBegin(GL_LINES); glVertex2f(286,411); glVertex2f(295,409); glEnd(); glBegin(GL_LINES); glVertex2f(295,409); glVertex2f(285,415); glEnd(); glBegin(GL_LINES); glVertex2f(285,415); glVertex2f(309,406); glEnd(); glColor3f(0.96,0.5,0.25); } void draw_bird() { GLfloat x=200,y=400,z=10; draw_brotate(); glBegin(GL_LINES); //draw legs of the bird glVertex2f(285,402); glVertex2f(275,402); glEnd(); glBegin(GL_LINES); glVertex2f(285,398); glVertex2f(275,398); glEnd(); glBegin(GL_LINES); glVertex2f(275,402); glVertex2f(270,405); glEnd(); glBegin(GL_LINES); glVertex2f(275,402); glVertex2f(270,398); glEnd(); glBegin(GL_LINES); glVertex2f(275,398); glVertex2f(273,400); glEnd(); glBegin(GL_LINES); glVertex2f(275,398); glVertex2f(270,395); glEnd(); glBegin(GL_LINES); glVertex2f(323,405); glVertex2f(323,407); glEnd(); glPushMatrix(); glTranslatef(323,409,10); glutSolidSphere(2,200,20); glPopMatrix(); glBegin(GL_TRIANGLES); glVertex2f(328,400); glVertex2f(331,397); glVertex2f(327,398.5); glEnd(); glFlush(); } void drawstars() { glColor3f(1.0,1.0,1.0); glBegin(GL_POINTS); glVertex3f(300.0,400.0,10.0); glVertex3f(200,400.0,10.0); glVertex3f(150,450.0,10.0); glVertex3f(100,470.0,10.0); glVertex3f(50,450.0,10.0); glVertex3f(50,350.0,10.0); glVertex3f(90,365.0,10.0); glVertex3f(350,450.0,10.0); glVertex3f(275,470.0,10.0); glVertex3f(280,430.0,10.0); glVertex3f(250,400.0,10.0); glVertex3f(450,450.0,10.0); glVertex3f(430,430.0,10.0); glVertex3f(430,470.0,10.0); glVertex3f(300,450.0,10.0); glVertex3f(265,380.0,10.0); glVertex3f(235,450.0,10.0); glEnd(); } void draw_all() { glClear(GL_COLOR_BUFFER_BIT); if(flag==0) { glDisable(GL_LIGHTING); //immp one draw_square(); draw_cloud(); glClearColor(0.506,.7,1,0.0); glTranslatef(q,w,e); glPushMatrix(); glColor3f(1.0,0.0,0.0); draw_boat(); draw_fishes(); glPushMatrix(); glColor3f(1.0,1.0,0.0); glTranslated(400,400,10); glutSolidSphere(20.0,5000,150); glPopMatrix(); } if(flag==1) { glDisable(GL_LIGHTING); //imp one draw_square(); draw_cloud(); glClearColor(0.9960,0.7070,0.3164,0.0); glTranslatef(q,w,e); glPushMatrix(); glColor3f(1.0,0.0,0.0); draw_boat(); draw_fishes(); glPushMatrix(); glColor3f(1.0,1.0,0.0); glTranslated(400,400,10); glutSolidSphere(20.0,500,100); glPopMatrix(); } if(flag==2) { // just try and change values in these arrays, specially the position array drawstars(); glEnable(GL_LIGHTING); glEnable(GL_LIGHT0); // GLfloat emission[]={0.1,0.1,0.1,0.0}; GLfloat diffuse[] = { 0.40, 0.40,0.40, 1.0 }; GLfloat ambiance[] = { 0.5, 0.5,0.5, 1.0 }; GLfloat specular[] = { 1.3, 1.3,.3, 1.0 }; GLfloat intensity[]={500.0}; GLfloat position[] = { 10,30,-30,1.0 }; glLightfv (GL_LIGHT0, GL_POSITION, position); glLightfv (GL_LIGHT0, GL_DIFFUSE,diffuse); glLightfv (GL_LIGHT0, GL_AMBIENT,ambiance); glLightModeli(GL_LIGHT_MODEL_LOCAL_VIEWER,GL_TRUE); glLightfv (GL_LIGHT0, GL_SPECULAR,specular); glLightfv (GL_LIGHT0, GL_INTENSITY,intensity); glColor3f(0,0.5,0.996); glBegin(GL_POLYGON); glVertex2f(0,0); glVertex2f(1000,0); glVertex2f(0,150); glVertex2f(1000,150); glEnd(); glTranslatef(q,w,e); glPushMatrix(); glColor3f(1.0,0.0,0.0); draw_boat(); draw_fishes(); glDisable(GL_LIGHTING); glDisable(GL_LIGHT0); draw_cloud(); glClearColor(0.0,0.0,0.0,0.0); glPushMatrix(); glColor3f(1.0,1.0,1.0); glTranslated(400,400,10); glutSolidSphere(20.0,500,100); glPopMatrix(); glColor3f(1.0,1.0,1.0); glBegin(GL_POINTS); glVertex3f(300.0,400.0,10.0); glEnd(); } glPushMatrix(); glTranslatef(ba,bb,bc); glPushMatrix(); draw_bird(); glPopMatrix(); glPopMatrix(); GLfloat i; glPushMatrix(); GLfloat x=0,y=100,j=0; int k; //draw_water(); q+=25; fq-=3.5; if(q>=440.0) //470 q=-390.0; //400 if(fq<=-300) //500 fq=400.0; //400 wa-=1; if(wa<=(-20)) wa=-0.5; ba+=6; if(ba>=500) ba=-400; glFlush(); glutSwapBuffers(); } void display(void) { draw_all(); } void color_menu(int id) { switch(id) { case 1: flag=0;break; case 2: flag=1;break; case 3: flag=2;break; case 4: exit(0); break; } glutPostRedisplay(); } void main_menu(int id) { switch(id) { case 1: break; case 2:exit(0);break; glutPostRedisplay(); } } int main(int argc,char **argv) { int sub_menu; glutInit(&argc,argv); glutInitDisplayMode(GLUT_RGB|GLUT_DOUBLE); glutInitWindowSize(1000,1000); glutInitWindowPosition(0,0); glutCreateWindow("Ship"); sub_menu=glutCreateMenu(color_menu); glutAddMenuEntry("Morning",1); glutAddMenuEntry("Evening",2); glutAddMenuEntry("Night",3); glutAddMenuEntry("Quit",4); glutCreateMenu(main_menu); glutAddSubMenu("View",sub_menu); glutAddMenuEntry("Quit",2); glutAttachMenu(GLUT_RIGHT_BUTTON); glutDisplayFunc(display); glutIdleFunc(display); myinit(); glutMainLoop(); glFlush(); }

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  • ERROR: Linux route add command failed: external program exited with error status: 4

    - by JohnMerlino
    A remote machine running fedora uses openvpn, and multiple developers were successfully able to connect to it via their client openvpn. However, I am running Ubuntu 12.04 and I am having trouble connecting to the server via vpn. I copied ca.crt, home.key, and home.crt from the server to my local machine to /etc/openvpn folder. My client.conf file looks like this: ############################################## # Sample client-side OpenVPN 2.0 config file # # for connecting to multi-client server. # # # # This configuration can be used by multiple # # clients, however each client should have # # its own cert and key files. # # # # On Windows, you might want to rename this # # file so it has a .ovpn extension # ############################################## # Specify that we are a client and that we # will be pulling certain config file directives # from the server. client # Use the same setting as you are using on # the server. # On most systems, the VPN will not function # unless you partially or fully disable # the firewall for the TUN/TAP interface. ;dev tap dev tun # Windows needs the TAP-Win32 adapter name # from the Network Connections panel # if you have more than one. On XP SP2, # you may need to disable the firewall # for the TAP adapter. ;dev-node MyTap # Are we connecting to a TCP or # UDP server? Use the same setting as # on the server. ;proto tcp proto udp # The hostname/IP and port of the server. # You can have multiple remote entries # to load balance between the servers. remote xx.xxx.xx.130 1194 ;remote my-server-2 1194 # Choose a random host from the remote # list for load-balancing. Otherwise # try hosts in the order specified. ;remote-random # Keep trying indefinitely to resolve the # host name of the OpenVPN server. Very useful # on machines which are not permanently connected # to the internet such as laptops. resolv-retry infinite # Most clients don't need to bind to # a specific local port number. nobind # Downgrade privileges after initialization (non-Windows only) ;user nobody ;group nogroup # Try to preserve some state across restarts. persist-key persist-tun # If you are connecting through an # HTTP proxy to reach the actual OpenVPN # server, put the proxy server/IP and # port number here. See the man page # if your proxy server requires # authentication. ;http-proxy-retry # retry on connection failures ;http-proxy [proxy server] [proxy port #] # Wireless networks often produce a lot # of duplicate packets. Set this flag # to silence duplicate packet warnings. ;mute-replay-warnings # SSL/TLS parms. # See the server config file for more # description. It's best to use # a separate .crt/.key file pair # for each client. A single ca # file can be used for all clients. ca ca.crt cert home.crt key home.key # Verify server certificate by checking # that the certicate has the nsCertType # field set to "server". This is an # important precaution to protect against # a potential attack discussed here: # http://openvpn.net/howto.html#mitm # # To use this feature, you will need to generate # your server certificates with the nsCertType # field set to "server". The build-key-server # script in the easy-rsa folder will do this. ns-cert-type server # If a tls-auth key is used on the server # then every client must also have the key. ;tls-auth ta.key 1 # Select a cryptographic cipher. # If the cipher option is used on the server # then you must also specify it here. ;cipher x # Enable compression on the VPN link. # Don't enable this unless it is also # enabled in the server config file. comp-lzo # Set log file verbosity. verb 3 # Silence repeating messages ;mute 20 But when I start server and look in /var/log/syslog, I notice the following error: May 27 22:13:51 myuser ovpn-client[5626]: /sbin/route add -net 10.27.12.1 netmask 255.255.255.252 gw 10.27.12.37 May 27 22:13:51 myuser ovpn-client[5626]: ERROR: Linux route add command failed: external program exited with error status: 4 May 27 22:13:51 myuser ovpn-client[5626]: /sbin/route add -net 172.27.12.0 netmask 255.255.255.0 gw 10.27.12.37 May 27 22:13:51 myuser ovpn-client[5626]: /sbin/route add -net 10.27.12.1 netmask 255.255.255.255 gw 10.27.12.37 And I am unable to connect to the server via openvpn: $ ssh [email protected] ssh: connect to host xxx.xx.xx.130 port 22: No route to host What may I be doing wrong?

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  • A Taxonomy of Numerical Methods v1

    - by JoshReuben
    Numerical Analysis – When, What, (but not how) Once you understand the Math & know C++, Numerical Methods are basically blocks of iterative & conditional math code. I found the real trick was seeing the forest for the trees – knowing which method to use for which situation. Its pretty easy to get lost in the details – so I’ve tried to organize these methods in a way that I can quickly look this up. I’ve included links to detailed explanations and to C++ code examples. I’ve tried to classify Numerical methods in the following broad categories: Solving Systems of Linear Equations Solving Non-Linear Equations Iteratively Interpolation Curve Fitting Optimization Numerical Differentiation & Integration Solving ODEs Boundary Problems Solving EigenValue problems Enjoy – I did ! Solving Systems of Linear Equations Overview Solve sets of algebraic equations with x unknowns The set is commonly in matrix form Gauss-Jordan Elimination http://en.wikipedia.org/wiki/Gauss%E2%80%93Jordan_elimination C++: http://www.codekeep.net/snippets/623f1923-e03c-4636-8c92-c9dc7aa0d3c0.aspx Produces solution of the equations & the coefficient matrix Efficient, stable 2 steps: · Forward Elimination – matrix decomposition: reduce set to triangular form (0s below the diagonal) or row echelon form. If degenerate, then there is no solution · Backward Elimination –write the original matrix as the product of ints inverse matrix & its reduced row-echelon matrix à reduce set to row canonical form & use back-substitution to find the solution to the set Elementary ops for matrix decomposition: · Row multiplication · Row switching · Add multiples of rows to other rows Use pivoting to ensure rows are ordered for achieving triangular form LU Decomposition http://en.wikipedia.org/wiki/LU_decomposition C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-lu-decomposition-for-solving.html Represent the matrix as a product of lower & upper triangular matrices A modified version of GJ Elimination Advantage – can easily apply forward & backward elimination to solve triangular matrices Techniques: · Doolittle Method – sets the L matrix diagonal to unity · Crout Method - sets the U matrix diagonal to unity Note: both the L & U matrices share the same unity diagonal & can be stored compactly in the same matrix Gauss-Seidel Iteration http://en.wikipedia.org/wiki/Gauss%E2%80%93Seidel_method C++: http://www.nr.com/forum/showthread.php?t=722 Transform the linear set of equations into a single equation & then use numerical integration (as integration formulas have Sums, it is implemented iteratively). an optimization of Gauss-Jacobi: 1.5 times faster, requires 0.25 iterations to achieve the same tolerance Solving Non-Linear Equations Iteratively find roots of polynomials – there may be 0, 1 or n solutions for an n order polynomial use iterative techniques Iterative methods · used when there are no known analytical techniques · Requires set functions to be continuous & differentiable · Requires an initial seed value – choice is critical to convergence à conduct multiple runs with different starting points & then select best result · Systematic - iterate until diminishing returns, tolerance or max iteration conditions are met · bracketing techniques will always yield convergent solutions, non-bracketing methods may fail to converge Incremental method if a nonlinear function has opposite signs at 2 ends of a small interval x1 & x2, then there is likely to be a solution in their interval – solutions are detected by evaluating a function over interval steps, for a change in sign, adjusting the step size dynamically. Limitations – can miss closely spaced solutions in large intervals, cannot detect degenerate (coinciding) solutions, limited to functions that cross the x-axis, gives false positives for singularities Fixed point method http://en.wikipedia.org/wiki/Fixed-point_iteration C++: http://books.google.co.il/books?id=weYj75E_t6MC&pg=PA79&lpg=PA79&dq=fixed+point+method++c%2B%2B&source=bl&ots=LQ-5P_taoC&sig=lENUUIYBK53tZtTwNfHLy5PEWDk&hl=en&sa=X&ei=wezDUPW1J5DptQaMsIHQCw&redir_esc=y#v=onepage&q=fixed%20point%20method%20%20c%2B%2B&f=false Algebraically rearrange a solution to isolate a variable then apply incremental method Bisection method http://en.wikipedia.org/wiki/Bisection_method C++: http://numericalcomputing.wordpress.com/category/algorithms/ Bracketed - Select an initial interval, keep bisecting it ad midpoint into sub-intervals and then apply incremental method on smaller & smaller intervals – zoom in Adv: unaffected by function gradient à reliable Disadv: slow convergence False Position Method http://en.wikipedia.org/wiki/False_position_method C++: http://www.dreamincode.net/forums/topic/126100-bisection-and-false-position-methods/ Bracketed - Select an initial interval , & use the relative value of function at interval end points to select next sub-intervals (estimate how far between the end points the solution might be & subdivide based on this) Newton-Raphson method http://en.wikipedia.org/wiki/Newton's_method C++: http://www-users.cselabs.umn.edu/classes/Summer-2012/csci1113/index.php?page=./newt3 Also known as Newton's method Convenient, efficient Not bracketed – only a single initial guess is required to start iteration – requires an analytical expression for the first derivative of the function as input. Evaluates the function & its derivative at each step. Can be extended to the Newton MutiRoot method for solving multiple roots Can be easily applied to an of n-coupled set of non-linear equations – conduct a Taylor Series expansion of a function, dropping terms of order n, rewrite as a Jacobian matrix of PDs & convert to simultaneous linear equations !!! Secant Method http://en.wikipedia.org/wiki/Secant_method C++: http://forum.vcoderz.com/showthread.php?p=205230 Unlike N-R, can estimate first derivative from an initial interval (does not require root to be bracketed) instead of inputting it Since derivative is approximated, may converge slower. Is fast in practice as it does not have to evaluate the derivative at each step. Similar implementation to False Positive method Birge-Vieta Method http://mat.iitm.ac.in/home/sryedida/public_html/caimna/transcendental/polynomial%20methods/bv%20method.html C++: http://books.google.co.il/books?id=cL1boM2uyQwC&pg=SA3-PA51&lpg=SA3-PA51&dq=Birge-Vieta+Method+c%2B%2B&source=bl&ots=QZmnDTK3rC&sig=BPNcHHbpR_DKVoZXrLi4nVXD-gg&hl=en&sa=X&ei=R-_DUK2iNIjzsgbE5ID4Dg&redir_esc=y#v=onepage&q=Birge-Vieta%20Method%20c%2B%2B&f=false combines Horner's method of polynomial evaluation (transforming into lesser degree polynomials that are more computationally efficient to process) with Newton-Raphson to provide a computational speed-up Interpolation Overview Construct new data points for as close as possible fit within range of a discrete set of known points (that were obtained via sampling, experimentation) Use Taylor Series Expansion of a function f(x) around a specific value for x Linear Interpolation http://en.wikipedia.org/wiki/Linear_interpolation C++: http://www.hamaluik.com/?p=289 Straight line between 2 points à concatenate interpolants between each pair of data points Bilinear Interpolation http://en.wikipedia.org/wiki/Bilinear_interpolation C++: http://supercomputingblog.com/graphics/coding-bilinear-interpolation/2/ Extension of the linear function for interpolating functions of 2 variables – perform linear interpolation first in 1 direction, then in another. Used in image processing – e.g. texture mapping filter. Uses 4 vertices to interpolate a value within a unit cell. Lagrange Interpolation http://en.wikipedia.org/wiki/Lagrange_polynomial C++: http://www.codecogs.com/code/maths/approximation/interpolation/lagrange.php For polynomials Requires recomputation for all terms for each distinct x value – can only be applied for small number of nodes Numerically unstable Barycentric Interpolation http://epubs.siam.org/doi/pdf/10.1137/S0036144502417715 C++: http://www.gamedev.net/topic/621445-barycentric-coordinates-c-code-check/ Rearrange the terms in the equation of the Legrange interpolation by defining weight functions that are independent of the interpolated value of x Newton Divided Difference Interpolation http://en.wikipedia.org/wiki/Newton_polynomial C++: http://jee-appy.blogspot.co.il/2011/12/newton-divided-difference-interpolation.html Hermite Divided Differences: Interpolation polynomial approximation for a given set of data points in the NR form - divided differences are used to approximately calculate the various differences. For a given set of 3 data points , fit a quadratic interpolant through the data Bracketed functions allow Newton divided differences to be calculated recursively Difference table Cubic Spline Interpolation http://en.wikipedia.org/wiki/Spline_interpolation C++: https://www.marcusbannerman.co.uk/index.php/home/latestarticles/42-articles/96-cubic-spline-class.html Spline is a piecewise polynomial Provides smoothness – for interpolations with significantly varying data Use weighted coefficients to bend the function to be smooth & its 1st & 2nd derivatives are continuous through the edge points in the interval Curve Fitting A generalization of interpolating whereby given data points may contain noise à the curve does not necessarily pass through all the points Least Squares Fit http://en.wikipedia.org/wiki/Least_squares C++: http://www.ccas.ru/mmes/educat/lab04k/02/least-squares.c Residual – difference between observed value & expected value Model function is often chosen as a linear combination of the specified functions Determines: A) The model instance in which the sum of squared residuals has the least value B) param values for which model best fits data Straight Line Fit Linear correlation between independent variable and dependent variable Linear Regression http://en.wikipedia.org/wiki/Linear_regression C++: http://www.oocities.org/david_swaim/cpp/linregc.htm Special case of statistically exact extrapolation Leverage least squares Given a basis function, the sum of the residuals is determined and the corresponding gradient equation is expressed as a set of normal linear equations in matrix form that can be solved (e.g. using LU Decomposition) Can be weighted - Drop the assumption that all errors have the same significance –-> confidence of accuracy is different for each data point. Fit the function closer to points with higher weights Polynomial Fit - use a polynomial basis function Moving Average http://en.wikipedia.org/wiki/Moving_average C++: http://www.codeproject.com/Articles/17860/A-Simple-Moving-Average-Algorithm Used for smoothing (cancel fluctuations to highlight longer-term trends & cycles), time series data analysis, signal processing filters Replace each data point with average of neighbors. Can be simple (SMA), weighted (WMA), exponential (EMA). Lags behind latest data points – extra weight can be given to more recent data points. Weights can decrease arithmetically or exponentially according to distance from point. Parameters: smoothing factor, period, weight basis Optimization Overview Given function with multiple variables, find Min (or max by minimizing –f(x)) Iterative approach Efficient, but not necessarily reliable Conditions: noisy data, constraints, non-linear models Detection via sign of first derivative - Derivative of saddle points will be 0 Local minima Bisection method Similar method for finding a root for a non-linear equation Start with an interval that contains a minimum Golden Search method http://en.wikipedia.org/wiki/Golden_section_search C++: http://www.codecogs.com/code/maths/optimization/golden.php Bisect intervals according to golden ratio 0.618.. Achieves reduction by evaluating a single function instead of 2 Newton-Raphson Method Brent method http://en.wikipedia.org/wiki/Brent's_method C++: http://people.sc.fsu.edu/~jburkardt/cpp_src/brent/brent.cpp Based on quadratic or parabolic interpolation – if the function is smooth & parabolic near to the minimum, then a parabola fitted through any 3 points should approximate the minima – fails when the 3 points are collinear , in which case the denominator is 0 Simplex Method http://en.wikipedia.org/wiki/Simplex_algorithm C++: http://www.codeguru.com/cpp/article.php/c17505/Simplex-Optimization-Algorithm-and-Implemetation-in-C-Programming.htm Find the global minima of any multi-variable function Direct search – no derivatives required At each step it maintains a non-degenerative simplex – a convex hull of n+1 vertices. Obtains the minimum for a function with n variables by evaluating the function at n-1 points, iteratively replacing the point of worst result with the point of best result, shrinking the multidimensional simplex around the best point. Point replacement involves expanding & contracting the simplex near the worst value point to determine a better replacement point Oscillation can be avoided by choosing the 2nd worst result Restart if it gets stuck Parameters: contraction & expansion factors Simulated Annealing http://en.wikipedia.org/wiki/Simulated_annealing C++: http://code.google.com/p/cppsimulatedannealing/ Analogy to heating & cooling metal to strengthen its structure Stochastic method – apply random permutation search for global minima - Avoid entrapment in local minima via hill climbing Heating schedule - Annealing schedule params: temperature, iterations at each temp, temperature delta Cooling schedule – can be linear, step-wise or exponential Differential Evolution http://en.wikipedia.org/wiki/Differential_evolution C++: http://www.amichel.com/de/doc/html/ More advanced stochastic methods analogous to biological processes: Genetic algorithms, evolution strategies Parallel direct search method against multiple discrete or continuous variables Initial population of variable vectors chosen randomly – if weighted difference vector of 2 vectors yields a lower objective function value then it replaces the comparison vector Many params: #parents, #variables, step size, crossover constant etc Convergence is slow – many more function evaluations than simulated annealing Numerical Differentiation Overview 2 approaches to finite difference methods: · A) approximate function via polynomial interpolation then differentiate · B) Taylor series approximation – additionally provides error estimate Finite Difference methods http://en.wikipedia.org/wiki/Finite_difference_method C++: http://www.wpi.edu/Pubs/ETD/Available/etd-051807-164436/unrestricted/EAMPADU.pdf Find differences between high order derivative values - Approximate differential equations by finite differences at evenly spaced data points Based on forward & backward Taylor series expansion of f(x) about x plus or minus multiples of delta h. Forward / backward difference - the sums of the series contains even derivatives and the difference of the series contains odd derivatives – coupled equations that can be solved. Provide an approximation of the derivative within a O(h^2) accuracy There is also central difference & extended central difference which has a O(h^4) accuracy Richardson Extrapolation http://en.wikipedia.org/wiki/Richardson_extrapolation C++: http://mathscoding.blogspot.co.il/2012/02/introduction-richardson-extrapolation.html A sequence acceleration method applied to finite differences Fast convergence, high accuracy O(h^4) Derivatives via Interpolation Cannot apply Finite Difference method to discrete data points at uneven intervals – so need to approximate the derivative of f(x) using the derivative of the interpolant via 3 point Lagrange Interpolation Note: the higher the order of the derivative, the lower the approximation precision Numerical Integration Estimate finite & infinite integrals of functions More accurate procedure than numerical differentiation Use when it is not possible to obtain an integral of a function analytically or when the function is not given, only the data points are Newton Cotes Methods http://en.wikipedia.org/wiki/Newton%E2%80%93Cotes_formulas C++: http://www.siafoo.net/snippet/324 For equally spaced data points Computationally easy – based on local interpolation of n rectangular strip areas that is piecewise fitted to a polynomial to get the sum total area Evaluate the integrand at n+1 evenly spaced points – approximate definite integral by Sum Weights are derived from Lagrange Basis polynomials Leverage Trapezoidal Rule for default 2nd formulas, Simpson 1/3 Rule for substituting 3 point formulas, Simpson 3/8 Rule for 4 point formulas. For 4 point formulas use Bodes Rule. Higher orders obtain more accurate results Trapezoidal Rule uses simple area, Simpsons Rule replaces the integrand f(x) with a quadratic polynomial p(x) that uses the same values as f(x) for its end points, but adds a midpoint Romberg Integration http://en.wikipedia.org/wiki/Romberg's_method C++: http://code.google.com/p/romberg-integration/downloads/detail?name=romberg.cpp&can=2&q= Combines trapezoidal rule with Richardson Extrapolation Evaluates the integrand at equally spaced points The integrand must have continuous derivatives Each R(n,m) extrapolation uses a higher order integrand polynomial replacement rule (zeroth starts with trapezoidal) à a lower triangular matrix set of equation coefficients where the bottom right term has the most accurate approximation. The process continues until the difference between 2 successive diagonal terms becomes sufficiently small. Gaussian Quadrature http://en.wikipedia.org/wiki/Gaussian_quadrature C++: http://www.alglib.net/integration/gaussianquadratures.php Data points are chosen to yield best possible accuracy – requires fewer evaluations Ability to handle singularities, functions that are difficult to evaluate The integrand can include a weighting function determined by a set of orthogonal polynomials. Points & weights are selected so that the integrand yields the exact integral if f(x) is a polynomial of degree <= 2n+1 Techniques (basically different weighting functions): · Gauss-Legendre Integration w(x)=1 · Gauss-Laguerre Integration w(x)=e^-x · Gauss-Hermite Integration w(x)=e^-x^2 · Gauss-Chebyshev Integration w(x)= 1 / Sqrt(1-x^2) Solving ODEs Use when high order differential equations cannot be solved analytically Evaluated under boundary conditions RK for systems – a high order differential equation can always be transformed into a coupled first order system of equations Euler method http://en.wikipedia.org/wiki/Euler_method C++: http://rosettacode.org/wiki/Euler_method First order Runge–Kutta method. Simple recursive method – given an initial value, calculate derivative deltas. Unstable & not very accurate (O(h) error) – not used in practice A first-order method - the local error (truncation error per step) is proportional to the square of the step size, and the global error (error at a given time) is proportional to the step size In evolving solution between data points xn & xn+1, only evaluates derivatives at beginning of interval xn à asymmetric at boundaries Higher order Runge Kutta http://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods C++: http://www.dreamincode.net/code/snippet1441.htm 2nd & 4th order RK - Introduces parameterized midpoints for more symmetric solutions à accuracy at higher computational cost Adaptive RK – RK-Fehlberg – estimate the truncation at each integration step & automatically adjust the step size to keep error within prescribed limits. At each step 2 approximations are compared – if in disagreement to a specific accuracy, the step size is reduced Boundary Value Problems Where solution of differential equations are located at 2 different values of the independent variable x à more difficult, because cannot just start at point of initial value – there may not be enough starting conditions available at the end points to produce a unique solution An n-order equation will require n boundary conditions – need to determine the missing n-1 conditions which cause the given conditions at the other boundary to be satisfied Shooting Method http://en.wikipedia.org/wiki/Shooting_method C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-shooting-method-for-solving.html Iteratively guess the missing values for one end & integrate, then inspect the discrepancy with the boundary values of the other end to adjust the estimate Given the starting boundary values u1 & u2 which contain the root u, solve u given the false position method (solving the differential equation as an initial value problem via 4th order RK), then use u to solve the differential equations. Finite Difference Method For linear & non-linear systems Higher order derivatives require more computational steps – some combinations for boundary conditions may not work though Improve the accuracy by increasing the number of mesh points Solving EigenValue Problems An eigenvalue can substitute a matrix when doing matrix multiplication à convert matrix multiplication into a polynomial EigenValue For a given set of equations in matrix form, determine what are the solution eigenvalue & eigenvectors Similar Matrices - have same eigenvalues. Use orthogonal similarity transforms to reduce a matrix to diagonal form from which eigenvalue(s) & eigenvectors can be computed iteratively Jacobi method http://en.wikipedia.org/wiki/Jacobi_method C++: http://people.sc.fsu.edu/~jburkardt/classes/acs2_2008/openmp/jacobi/jacobi.html Robust but Computationally intense – use for small matrices < 10x10 Power Iteration http://en.wikipedia.org/wiki/Power_iteration For any given real symmetric matrix, generate the largest single eigenvalue & its eigenvectors Simplest method – does not compute matrix decomposition à suitable for large, sparse matrices Inverse Iteration Variation of power iteration method – generates the smallest eigenvalue from the inverse matrix Rayleigh Method http://en.wikipedia.org/wiki/Rayleigh's_method_of_dimensional_analysis Variation of power iteration method Rayleigh Quotient Method Variation of inverse iteration method Matrix Tri-diagonalization Method Use householder algorithm to reduce an NxN symmetric matrix to a tridiagonal real symmetric matrix vua N-2 orthogonal transforms     Whats Next Outside of Numerical Methods there are lots of different types of algorithms that I’ve learned over the decades: Data Mining – (I covered this briefly in a previous post: http://geekswithblogs.net/JoshReuben/archive/2007/12/31/ssas-dm-algorithms.aspx ) Search & Sort Routing Problem Solving Logical Theorem Proving Planning Probabilistic Reasoning Machine Learning Solvers (eg MIP) Bioinformatics (Sequence Alignment, Protein Folding) Quant Finance (I read Wilmott’s books – interesting) Sooner or later, I’ll cover the above topics as well.

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  • Customize Firefox Status Bar?

    - by Steven Penny
    For web browsing I use Pale Moon. Pale Moon has a Status Bar, similar to what is now known as the Add-on Bar in Firefox. With Pale Moon when I hover over a link URL is shown in the status bar URL is shown instantly Entire width of status bar is allowed for URL, if necessary With Firefox when I hover over a link URL is shown in a tooltip in lower left corner URL is shown after intentional delay Only half the browser window width is allowed for URL Is there a way to make Firefox behave more like Pale Moon? No Status-4-Evar answers I realize Status-4-Evar might be the best solution here but I wish to see what, if any other options are out there. I will also accept well thought out and referenced answers as to why the Firefox way is "better".

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  • Torque and maui node status

    - by Lafada
    I am new for torque and maui. I was checking for node state to looking for which nodes are free and which nodes are in use. For torque one command is pbsnodes. Which gives status and other info related to node. When I was checking for maui then I found command diagnose -n which also shows status of the node. I was wondering between these 2 status. Both are giving different status for the same situation. When I do man pbsnodes I got the possible states for node "free", "offline", "down", "reserve", "job-exclusive", "job-sharing", "busy", "time-shared", or "state-unknown" But this type of different state I cant find for diagnose -n. How pbsnodes and diagnose -n get the status for node. Is there any database like xCAT use for torque or maui? Thx in advance for your valuable time.

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  • SQL SERVER – Detecting guest User Permissions – guest User Access Status

    - by pinaldave
    Earlier I wrote the blog post SQL SERVER – Disable Guest Account – Serious Security Issue, and I got many comments asking questions related to the guest user. Here are the comments of Manoj: 1) How do we know if the uest user is enabled or disabled? 2) What is the default for guest user in SQL Server? Default settings for guest user When SQL Server is installed by default, the guest user is disabled for security reasons. If the guest user is not properly configured, it can create a major security issue. You can read more about this here. Identify guest user status There are multiple ways to identify guest user status: Using SQL Server Management Studio (SSMS) You can expand the database node >> Security >> Users. If you see the RED arrow pointing downward, it means that the guest user is disabled. Using sys.sysusers Here is a simple script. If you notice column dbaccess as 1, it means that the guest user is enabled and has access to the database. SELECT name, hasdbaccess FROM sys.sysusers WHERE name = 'guest' Using sys.database_principals and sys.server_permissions This script is valid in SQL Server 2005 and a later version. This is my default method recently. SELECT name, permission_name, state_desc FROM sys.database_principals dp INNER JOIN sys.server_permissions sp ON dp.principal_id = sp.grantee_principal_id WHERE name = 'guest' AND permission_name = 'CONNECT' Using sp_helprotect Just run the following stored procedure which will give you all the permissions associated with the user. sp_helprotect @username = 'guest' Disable Guest Account REVOKE CONNECT FROM guest Additionally, the guest account cannot be disabled in master and tempdb; it is always enabled. There is a special need for this. Let me ask a question back at you: In which scenario do you think this will be useful to keep the guest, and what will the additional configuration go along with the scenario? Note: Special mention to Imran Mohammed for being always there when users need help. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Security, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • How would you know if you've written readable and easily maintainable code?

    - by KyelJmD
    How would one know if the code he has created is easily maintainable and readable? Of course in your point of view (the one who actually wrote the code) your code is readable and maintainable, but we should be true to ourselves here. How would we know if we've written pretty messy and unmaintainable code? Are there any constructs or guidelines to know if we have developed a messy piece of software?

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  • Apache proxy is modifying the HTTP status code

    - by jarnbjo
    I am using Apache as a proxy frontend for a Java web application, which is deployed on WebSphere. The web application is using custom status codes (55x) to signal specific errors to the clients. When accessing the web application directly through the WebSphere HTTP listener, everything works as expected, but when these requests are proxied through an Apache load balancer, the status codes are modified by Apache and replaced with a generic 500 error code (internal server error). In Apache's access.log, the correct status code is logged: <IP> - - [11/Nov/2011:17:24:53 +0100] "POST <URL> HTTP/1.1" 551 36 But the actual response received by the client starts like this (logged with tcpdump): HTTP/1.1 500 Internal Server Error ... Followed by the real status code in the response content: ... Error 551: Berichteter Fehler: 551 ... Is there an obvious reason for this behaviour or does someone have a suggestion on how to modify the Apache configuration to forward the "real" status code instead of 500?

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  • What is the oldest living piece of unaltered production code? [closed]

    - by user1598390
    It's come to my mind that parts of the code in, say, Unix, has maybe passed unaltered from one version or flavor into another. Maybe some pieces of the source code of the ls command is the same, unaltered, than was written years ago. Have any of you read or learn about this ? What would be the oldest living piece of unaltered production code still running, passing from version through version of a program or system ? Will the code we write outlive us for decades ?

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