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  • Need to format character precedence in Strings.

    - by Christian
    I'm currently writing a Roman Numeral Converter for the fun of it. The problem works up to the aforementioned character precedence. Since Roman Numerals are not positional, i.e. III does not symbolize 1*whatever base^2 + 1*whatever base^1 + 1*whatever base^0. That of course makes it hard when somebody types in XIV and I need to make sure that the I is not added in this case, but rather subtracted. I'm not sure how to do this. What would be the best approach to tackle this? I have both the Roman Symbols and their respective decimal numbers stored in arrays: const char cRomanArray[] = "IVXLCDM"; const int romanArray[] = { 1, 5, 10, 50, 100, 500, 1000 }; so it wouldn't be too hard for me to brute-force the damn thing by simply checking the precedence within the array, i.e. if the symbol is smaller than the next symbol, i.e. in the exampe 'XIV' if 'I' is smaller than 'V', in which case it would be because I have ordered them in the array, then I could make it subtract the value instead of add. But this seems like a very ugly solution. Are there perhaps any better ones? I was thinking something along the lines of Regular Expressions maybe( forgive me if that sounds like a horrible idea, I haven't used RegExp yet, but it sounds like it could do what I need, and that's to determine the characters in a string.)

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  • How does this Switch statement know which case to execute? (PHP/MySQL)

    - by ggfan
    Here is a code form a PHP+MySQL book I am reading and I am having trouble understanding this code. This code is about checking a file uploaded into a database. (Please excuse any spelling errors if any, I was typing it in) Q1: How does it know which case to echo? In the whole code, there is no mention of each case. Q2: Why do they skip case 5?! Or does it not matter which numbers you use(so I can have case 1, case 18, case 2?) if($_FILES['userfile']['error']>0) { echo 'Problem: '; switch($_FILES['userfile']['error']) { case 1: echo 'File exceeded upload_max_filesize'; break; case 2: echo 'File exceeded max_file_size'; break; case 3: echo 'File only partially uploaded'; break; case 4: echo 'No file uploaded'; break; case 6: echo 'Cannot upload file: no temp directory specified'; break; case 7: echo 'Upload failed: Cannot write to disk'; break; } exit; }

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  • Spring maven libraries

    - by Calm Storm
    I would like to know why some of the libraries are not released during a normal release cycle. For example, from http://repo2.maven.org/maven2/org/springframework/ while spring-core have 3.0.3-RELEASE, spring-remoting and spring-jmx were released only in 2.0.8. Can someone tell me what this would mean? I agree that if there are no changes in the component say spring-jmx then they don't have to release it, but since 90% of the world uses Maven for dependency management can they not just re-release the same libs (of spring-remoting and spring-jmx?) I ask this because I declare my deps like, <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-remoting</artifactId> <version>${spring.version}</version> </dependency> and I would prefer supplying one spring.version instead of keeping version numbers upto date for all components? The four libraries of interest to me are spring-dao, spring-support, spring-jmx, spring-remoting

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  • Cleaner/more effective way to use modulus and creating columned lists

    - by WmasterJ
    I currently have a list (<ul>) of people that I have divided up into two columns. But after finishing the code for it I keept wondering if there is a more effective or clean way to do the same thing. echo "<table class='area_list'><tr>"; // Loop users within areas, divided up in 2 columns $count = count($areaArray); for($i=0 ; $i<$count ; $i++) { // get the modulus value + ceil for uneven numbers $rowCalc = ($i+1) % ceil($count/2); if ($rowCalc == 1) echo "<td><ul>"; // OUTPUT the actual list item echo "<li>{$users[$uid]->profile_lastname}</li>"; if ($rowCalc == 0 && $i!=0) echo "</ul></td>"; } echo "</table>"; Any ideas of how to make this cleaner or do it in another way?

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  • LaTeX book class: Twosided document with wrong margins

    - by fgysin
    I am trying to write my thesis in latex... Cannot get the layout straight though :? I'm using the following document class: \documentclass[11pt,a4paper,twoside,openright]{book} My problem is: on the odd numbered pages there is a big margin right, and a small margin left - it should be the other way round... (for binding & stuff) I am a little puzzled by this - am I just to stupid to see the obvious? The odd page numbers appear on the 'right' page of a bound document, so there needs to be a larger margin left for bindin. Right? Why does LaTeX not behave like this? Here is the full code to produce a small Tex file that shows my problem: \documentclass[11pt,a4paper,twoside,openright]{book} \begin{document} \chapter{blah} Lorem ipsum ius et accumsan tractatos, aliquip deterruisset cu usu. Ea soleat eirmod nostrud eum, est ceteros similique ad, at mea tempor petentium. At decore neglegentur quo, ea ius doming dictas facilis, duo ut porro nostrum suavitate. \end{document}

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  • Distributed development systems

    - by Nathan Adams
    I am interested in a system that allows for distributed development with an authentication piece. What do I mean by that? Ok so lets take SVN, SVN keeps track of revisions and doesn't care who submits, as long as you have the right to submit you can submit, really, to any part in the repository. Where does my system come into play? Being able to granulate access control and give a stackoverflow like feel to the environment. In the system I am describing we have 4 users Bob, Alice, Dan, Joe. Bob is a project managed, Alice and Dan are programmers under Bob and Joe is a random programmer on the internet who wants to help. Ideally in this system, Bob can commit any changes and won't require approval. Alice and Dan can commit to their branches, or a branch, but a commit to the trunk would need approval by Bob. This is where Joe comes in, wants to help, however, you just don't want to give him the keys to the kingdom just yet so to speak, so in my system you would setup a "low user" account. Any commits that Joe makes would need to be approved by Dan, Alice or both. However, in the system, Joe can build up "Karma" where after so many approved commits it would only need approval by one of the programmers, and then eventually no approval would be necessary. Does that make sense and do you know if a system like that exists? Or am I just crazy to even think such a system/environment would be possible?

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  • java RMI connection to server

    - by user85116
    I have a very simple rmi client / server application. I don't use the "rmiregistry" application though, I use this to create the server: server = new RemoteServer(); registry = LocateRegistry.createRegistry(PORT); registry.bind("RemoteServer", server); The client part is: registry = LocateRegistry.getRegistry(IPADDRESS, PORT); remote = (IRemoteServer) registry.lookup("RemoteServer"); Here is the fascinating problem: The application works perfectly when both server and client are running in my (private) local network. As soon as I put the server on a public server, the application hangs for a minute, then gives me the following error: java.rmi.ServerException: RemoteException occurred in server thread; nested exception is: java.rmi.ConnectException: Connection refused to host: 192.168.x.y; nested exception is: java.net.ConnectException: Connection timed out: connect at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source) at sun.rmi.transport.Transport$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.Transport.serviceCall(Unknown Source) at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source ... (the rest is truncated) The key I think is that the client (running on my private network) cannot connect to myself (my address is 192.168.x.y where x.y is some other numbers, but the real error message shows my ip address listed there) If I kill the rmi server on the public internet, then I instantly get a "connection refused to host: a.b.c.d") message, so I know that something at the server end is at least working. Any suggestions? EDIT: just to make this a little more clear: 192.168.x.y is the client address, a.b.c.d is the server address. The stacktrace shows the client cannot connect to the client.

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  • R plot- SGAM plot counts vs. time - how do I get dates on the x-axis?

    - by Nate
    I'd like to plot this vs. time, with the actual dates (years actually, 1997,1998...2010). The dates are in a raw format, ala SAS, days since 1960 (hence as.date conversion). If I convert the dates using as.date to variable x, and do the GAM plot, I get an error. It works fine with the raw day numbers. But I want the plot to display the years (data are not equally spaced). structure(list(site = c(928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L), date = c(13493L, 13534L, 13566L, 13611L, 13723L, 13752L, 13804L, 13837L, 13927L, 14028L, 14082L, 14122L, 14150L, 14182L, 14199L, 16198L, 16279L, 16607L, 16945L, 17545L, 17650L, 17743L, 17868L, 17941L, 18017L, 18092L), y = c(7L, 7L, 17L, 18L, 17L, 17L, 10L, 3L, 17L, 24L, 11L, 5L, 5L, 3L, 5L, 14L, 2L, 9L, 9L, 4L, 7L, 6L, 1L, 0L, 5L, 0L)), .Names = c("site", "date", "y"), class = "data.frame", row.names = c(NA, -26L)) sgam1 <- gam(sites$y ~ s(sites$date)) sgam <- predict(sgam1, se=TRUE) plot(sites$date,sites$y,xaxt="n", xlab='Time', ylab='Counts') x<-as.Date(sites$date, origin="1960-01-01") axis(1, at=1:26,labels=x) lines(sites$date,sgam$fit, lty = 1) lines(sites$date,sgam$fit + 1.96* sgam$se, lty = 2) lines(sites$date,sgam$fit - 1.96* sgam$se, lty = 2) ggplot2 has a solution (it doesn't mind the as.date thing) but it gives me other problems...

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  • Javascript/PHP and timezones

    - by James
    Hi, I'd like to be able to guess the user's timezone offset and whether or not daylight savings is being applied. Currently, the most definitive code that I've found for this is here: http://www.michaelapproved.com/articles/daylight-saving-time-dst-detect/ So this gives me the offset along with the DST indicator. Now, I want to use these in my PHP scripts in order to ouput the local date/time for the user....but what's best for this? I figure I have 2 options: a) Pick a random timezone which has the same offset and DST setting from the output of timezone_abbreviations_list(). Then call date_timezone_set() with this in order to apply the correct treatment to the time. b) Continue treating the date as UTC but just do some timestamp addition to add the appropriate number of hours on. My feeling is that option B is the best way. The reason for this is that with A, I could be using a timezone which although correct in terms of offset/dst, may have some obscur rules in place behind the scene that could give surprising results (I don't know of any but nonetheless I don't think I can rule it out). I'd then re-check the timezone using Javascript at the start of each session in order to capture when either the user's timezone changes (very unlikely) or they pass in to the DST period. Sorry for the brain dump - I'm really just after some sort of reassurance that the approaches above are valid. Thanks, James.

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  • How to get raw jpeg data (but no metatags / proprietary markers)

    - by CoolAJ86
    I want to get raw jpeg data - no metadata. I'm very confused looking at the jpeg "standards". How correct is my understanding of the marker "tree"? 0xFFD8 - Identifies the file as an image 0xFFE? - EXIF, JFIF, SPIFF, ICC, etc 0x???? - the length of the tag 0xFFD8 - Start of Image 0xFFE0 - should follow SOI as per spec, but often preceded by comments ??? 0x???? - Matrices, tags, random data ??? There are never other markers in-between these markers? Or these include the matrices and such? 0xFFDA - Start of Stream - This is what I want, yes? 0xXXXX - length of stream 0xFFD9 - End of Stream (EOI) 0x???? - Comment tags, extra exif, jfif info??? 0xFFD9 - End of Image 0xFF00 - escaped 0xFF, not to be confused with a marker This has been my reading material: http://en.wikipedia.org/wiki/JPEG http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html http://www.media.mit.edu/pia/Research/deepview/exif.html http://www.faqs.org/faqs/jpeg-faq/part1/section-15.html

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  • Java 7u4 webstart security exception: Class does not match trust level

    - by Glstunna
    We began to notice that with Java 7 (particularly with update 4), that all our users began to see this with our Webstart app: [14:42:58,422] AWT-EventQueue-0(DEBUG) java.lang.SecurityException: class "CLASSNAME" does not match trust level of other classes in the same package [14:42:58,422] AWT-EventQueue-0(DEBUG) at com.sun.deploy.security.CPCallbackHandler$ChildElement.checkResource(Unknown Source) [14:42:58,422] AWT-EventQueue-0(DEBUG) at com.sun.deploy.security.DeployURLClassPath$JarLoader.checkResource(Unknown Source) [14:42:58,422] AWT-EventQueue-0(DEBUG) at com.sun.deploy.security.DeployURLClassPath$JarLoader.getResource(Unknown Source) [14:42:58,422] AWT-EventQueue-0(DEBUG) at com.sun.deploy.security.DeployURLClassPath.getResource(Unknown Source) [14:42:58,422] AWT-EventQueue-0(DEBUG) at java.net.URLClassLoader$1.run(Unknown Source) [14:42:58,422] AWT-EventQueue-0(DEBUG) at java.net.URLClassLoader$1.run(Unknown Source) [14:42:58,422] AWT-EventQueue-0(DEBUG) at java.security.AccessController.doPrivileged(Native Method) [14:42:58,422] AWT-EventQueue-0(DEBUG) at java.net.URLClassLoader.findClass(Unknown Source) [14:42:58,422] AWT-EventQueue-0(DEBUG) at com.sun.jnlp.JNLPClassLoader.findClass(Unknown Source) [14:42:58,422] AWT-EventQueue-0(DEBUG) at java.lang.ClassLoader.loadClass(Unknown Source) [14:42:58,422] AWT-EventQueue-0(DEBUG) at java.lang.ClassLoader.loadClass(Unknown Source)...More Where CLASSNAME = pretty much every class at random points from several jars in the app execution, breaking several behavior. If our users were to use Java 6, they have no problems! Just 7 (update 4). We sign ALL our jars, both the main application jar and it's library jars. i.e Users launching our webstart app see the blue shield instead of yellow or red. This is obviously an issue as users are more frequently now upgrading to Java 7. I have tried to force our app to use Java 6 on the user machine either by using a previous installation(works), or installing a new one....with the j2se version="1.6" tag around resources but this causes it's own problems that would probably be best to make into it's own thread (the auto-jre-installation part). Did Oracle break Webstart security with Java 7u4? How do I solve this securityexception issue?

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  • weighted matching algorithm in Perl

    - by srk
    Problem : We have equal number of men and women.each men has a preference score toward each woman. So do the woman for each man. each of the men and women have certain interests. Based on the interest we calculate the preference scores. So initially we have an input in a file having x columns. First column is the person(men/woman) id. id are nothing but 0.. n numbers.(first half are men and next half woman) the remaining x-1 columns will have the interests. these are integers too. now using this n by x-1 matrix... we have come up with a n by n/2 matrix. the new matrix has all men and woman as their rows and scores for opposite sex in columns. We have to sort the scores in descending order, also we need to know the id of person related to the scores after sorting. So here i wanted to use hash table. once we get the scores we need to make up pairs.. for which we need to follow some rules. My trouble is with the second matrix of n by n/2 that needs to give information of which man/woman has how much preference on a woman/man. I need these scores sorted so that i know who is the first preferred woman/man, 2nd preferred and so on for a man/woman. I hope to get good suggestions on the data structures i use.. I prefer php or perl. Thank you in advance

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  • MVC Paging and Sorting Patterns: How to Page or Sort Re-Using Form Criteria

    - by CRice
    What is the best ASP.NET MVC pattern for paging data when the data is filtered by form criteria? This question is similar to: http://stackoverflow.com/questions/1425000/preserve-data-in-net-mvc but surely there is a better answer? Currently, when I click the search button this action is called: [AcceptVerbs(HttpVerbs.Post)] public ActionResult Search(MemberSearchForm formSp, int? pageIndex, string sortExpression) {} That is perfect for the initial display of the results in the table. But I want to have page number links or sort expression links re-post the current form data (the user entered it the first time - persisted because it is returned as viewdata), along with extra route params 'pageIndex' or 'sortExpression', Can an ActionLink or RouteLink (which I would use for page numbers) post the form to the url they specify? <%= Html.RouteLink("page 2", "MemberSearch", new { pageIndex = 1 })%> At the moment they just do a basic redirect and do not post the form values so the search page loads fresh. In regular old web forms I used to persist the search params (MemberSearchForm) in the ViewState and have a GridView paging or sorting event reuse it.

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  • Using multiple sockets, is non-blocking or blocking with select better?

    - by JPhi1618
    Lets say I have a server program that can accept connections from 10 (or more) different clients. The clients send data at random which is received by the server, but it is certain that at least one client will be sending data every update. The server cannot wait for information to arrive because it has other processing to do. Aside from using asynchronous sockets, I see two options: Make all sockets non-blocking. In a loop, call recv on each socket and allow it to fail with WSAEWOULDBLOCK if there is no data available and if I happen to get some data, then keep it. Leave the sockets as blocking. Add all sockets to a fd_set and call select(). If the return value is non-zero (which it will be most of the time), loop through all the sockets to find the appropriate number of readable sockets with FD_ISSET() and only call recv on the readable sockets. The first option will create a lot more calls to the recv function. The second method is a bigger pain from a programming perspective because of all the FD_SET and FD_ISSET looping. Which method (or another method) is preferred? Is avoiding the overhead on letting recv fail on a non-blocking socket worth the hassle of calling select()? I think I understand both methods and I have tried both with success, but I don't know if one way is considered better or optimal. Only knowledgeable replies please!

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  • Tricky file parsing. Inconsistent Delimeters

    - by Ben Truby
    I need to parse a file with the following format. 0000000 ...ISBN.. ..Author.. ..Title.. ..Edit.. ..Year.. ..Pub.. ..Comments.. NrtlExt Nrtl Next Navg NQoH UrtlExt Urtl Uext Uavg UQoH ABS NEB MBS FOL ABE0001 0-679-73378-7 ABE WOMAN IN THE DUNES (INT'L ED) 1st 64 RANDOM 0.00 13.90 0.00 10.43 0 21.00 10.50 6.44 3.22 2 2.00 0.50 2.00 2.00 ABS The ID and ISBN are not a problem, the title is. There is no set length for these fields, and there are no solid delimiters- the space can be used for most of the file. Another issue is that there is not always an entry in the comments field. When there is, there are spaced within the content. So I can get the first two, and the last fourteen. I need some help figuring out how to parse the middle six fields. This file was generated by an older program that I cannot change. I am using php to parse this file.

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  • Telephone Number to Geolocation UK

    - by David Toy
    Is there a service that provides latitude and longitude for UK phone numbers? For example: Query: 0141 574 xxx, Returns: (55.8659829, -4.2602205) [Glasgow City Centre] Allow me to stress that I am not looking for a reverse-directory-enquires. I am more interested in 'local area' for things like weather by phone or "Where's my nearest Pizza Shop?" If this service doesn't exist your suggestions on how to implement it or where to get data from would also be incredibly useful. I am aware that Ofcom provides a list of area codes with a place name [1] suitable for geolocation, but I have my concerns about resolution. I see this as a particular problem in smaller towns and rural areas where an area code will cover a large geographical area. Second Example: Area Code: 01555, Ofcom: Lanark However: 01555 860xxx is Crossford (4 miles W of Lanark) 01555 77xxxx is Carluke (5 miles NW) 01555 89xxxx is Lesmahagow (5 miles SW) 01555 840xxx is Carnwath (7 miles NE) Therefore 01555 covers about ~80 sq miles. That's not particularly local. [1] Ofcom Area Code Tool: http://www.ofcom.org.uk/consumer/2009/09/telephone-area-codes-tool/

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  • Matching Regular Expression in Javascript and PHP problem...

    - by Frankie
    I can't figure out how to get the same result from my Javscript as I do from my PHP. In particular, Javascript always leaves out the backslashes. Please ignore the random forward and backslashes; I put them there so that I can cover my basis on a windows system or any other system. Output: Input String: "/root\wp-cont ent\@*%'i@$@%$&^(@#@''mage6.jpg:" /root\wp-content\image6.jpg (PHP Output) /rootwp-contentimage6.jpg (Javscript Output) I would appreciate any help! PHP: <?php $path ="/root\wp-cont ent\@*%'i@$@%$&^(@#@''mage6.jpg:"; $path = preg_replace("/[^a-zA-Z0-9\\\\\/\.-]/", "", $path); echo $path; ?> Javascript: <script type="text/javascript"> var path = "/root\wp-cont ent\@*%'i@$@%$&^(@#@''mage6.jpg:"; //exact same string as PHP var regx = /[^a-zA-Z0-9\.\/-]/g; path = path.replace(regx,""); document.write("<br>"+path); </script>

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  • Error while compiling Hello world program for CUDA

    - by footy
    I am using Ubuntu 12.10 and have sucessfully installed CUDA 5.0 and its sample kits too. I have also run sudo apt-get install nvidia-cuda-toolkit Below is my hello world program for CUDA: #include <stdio.h> /* Core input/output operations */ #include <stdlib.h> /* Conversions, random numbers, memory allocation, etc. */ #include <math.h> /* Common mathematical functions */ #include <time.h> /* Converting between various date/time formats */ #include <cuda.h> /* CUDA related stuff */ __global__ void kernel(void) { } /* MAIN PROGRAM BEGINS */ int main(void) { /* Dg = 1; Db = 1; Ns = 0; S = 0 */ kernel<<<1,1>>>(); /* PRINT 'HELLO, WORLD!' TO THE SCREEN */ printf("\n Hello, World!\n\n"); /* INDICATE THE TERMINATION OF THE PROGRAM */ return 0; } /* MAIN PROGRAM ENDS */ The following error occurs when I compile it with nvcc -g hello_world_cuda.cu -o hello_world_cuda.x /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `main': /home/adarshakb/Documents/hello_world_cuda.cu:16: undefined reference to `cudaConfigureCall' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `__cudaUnregisterBinaryUtil': /usr/include/crt/host_runtime.h:172: undefined reference to `__cudaUnregisterFatBinary' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `__sti____cudaRegisterAll_51_tmpxft_000033f1_00000000_4_hello_world_cuda_cpp1_ii_b81a68a1': /tmp/tmpxft_000033f1_00000000-1_hello_world_cuda.cudafe1.stub.c:1: undefined reference to `__cudaRegisterFatBinary' /tmp/tmpxft_000033f1_00000000-1_hello_world_cuda.cudafe1.stub.c:1: undefined reference to `__cudaRegisterFunction' /tmp/tmpxft_000033f1_00000000-13_hello_world_cuda.o: In function `cudaError cudaLaunch<char>(char*)': /usr/lib/nvidia-cuda-toolkit/include/cuda_runtime.h:958: undefined reference to `cudaLaunch' collect2: ld returned 1 exit status I am also making sure that I use gcc and g++ version 4.4 ( As 4.7 there is some problem with CUDA)

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  • nedmalloc: where does mem<fm come from?

    - by Suma
    While implementing nedmalloc into my application, I am frequently hitting a situation when nedmalloc refuses to free a block of memory, claiming it did not allocate it. While debugging I have come up to the point I see a particular condition which is failing, all other (including magic numbers) succeed. The condition is this: if((size_t)mem-(size_t)fm>=(size_t)1<<(SIZE_T_BITSIZE-1)) return 0; On Win32 this seems to be equivalent to: if((int)((size_t)mem-(size_t)fm)<0) return 0; Which seems to be the same as: if((size_t)mem<(size_t)fm) return 0; In my case I really see mem < fm. What I do not understand now is, where does this condition come from. I cannot find anything which would guarantee the fm <= m anywhere in code. Yet, "select isn't broken": I doubt it would really be a bug in nedmalloc, most likely I am doing something wrong somewhere, but I cannot find it. Once I turn debugging features of nedmalloc on, the problem goes away. If someone here understands inner working of nedmalloc, could you please explain to me why is fm <= m?

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  • average case running time of linear search algorithm

    - by Brahadeesh
    Hi all. I am trying to derive the average case running time for deterministic linear search algorithm. The algorithm searches an element x in an unsorted array A in the order A[1], A[2], A[3]...A[n]. It stops when it finds the element x or proceeds until it reaches the end of the array. I searched on wikipedia and the answer given was (n+1)/(k+1) where k is the number of times x is present in the array. I approached in another way and am getting a different answer. Can anyone please give me the correct proof and also let me know whats wrong with my method? E(T)= 1*P(1) + 2*P(2) + 3*P(3) ....+ n*P(n) where P(i) is the probability that the algorithm runs for 'i' time (i.e. compares 'i' elements). P(i)= (n-i)C(k-1) * (n-k)! / n! Here, (n-i)C(k-1) is (n-i) Choose (k-1). As the algorithm has reached the ith step, the rest of k-1 x's must be in the last n-i elements. Hence (n-i)C(k-i). (n-k)! is the total number of ways of arranging the rest non x numbers, and n! is the total number of ways of arranging the n elements in the array. I am not getting (n+1)/(k+1) on simplifying.

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  • List of objects or parallel arrays of properties?

    - by Headcrab
    The question is, basically: what would be more preferable, both performance-wise and design-wise - to have a list of objects of a Python class or to have several lists of numerical properties? I am writing some sort of a scientific simulation which involves a rather large system of interacting particles. For simplicity, let's say we have a set of balls bouncing inside a box so each ball has a number of numerical properties, like x-y-z-coordinates, diameter, mass, velocity vector and so on. How to store the system better? Two major options I can think of are: to make a class "Ball" with those properties and some methods, then store a list of objects of the class, e. g. [b1, b2, b3, ...bn, ...], where for each bn we can access bn.x, bn.y, bn.mass and so on; to make an array of numbers for each property, then for each i-th "ball" we can access it's 'x' coordinate as xs[i], 'y' coordinate as ys[i], 'mass' as masses[i] and so on; To me it seems that the first option represents a better design. The second option looks somewhat uglier, but might be better in terms of performance, and it could be easier to use it with numpy and scipy, which I try to use as much as I can. I am still not sure if Python will be fast enough, so it may be necessary to rewrite it in C++ or something, after initial prototyping in Python. Would the choice of data representation be different for C/C++? What about a hybrid approach, e.g. Python with C++ extension?

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  • Crash on iOS when system purges memory and closes a UIViewController

    - by Amiramix
    My application is crashing when one of the views is purged from memory because of low-memory condition. At least this is what I understand from the crashlog. It happens on numerous screens but only when opening a Facebook dialog (using the Facebook SDK). Basically, looks like the system sometimes runs out of memory when we need to present a Facebook dialog (e.g. to let user post something on the Facebook timeline). Date/Time: 2012-03-14 19:47:33.819 +0000 OS Version: iPhone OS 5.1 (9B176) Report Version: 104 Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x30000008 Crashed Thread: 0 Thread 0 name: Dispatch queue: com.apple.main-thread Thread 0 Crashed: 0 libobjc.A.dylib 0x30f2bf78 objc_msgSend + 16 1 MyApp 0x00003c0e -LTBaseViewController viewDidUnload (LTBaseViewController.m:145) 2 MyApp 0x00004ea2 -LTBaseTableViewController viewDidUnload (LTBaseTableViewController.m:90) 3 UIKit 0x33766bd8 -[UIViewController unloadViewForced:] + 244 4 UIKit 0x338ae492 -[UIViewController purgeMemoryForReason:] + 58 5 Foundation 0x3071a4f8 __57-NSNotificationCenter addObserver:selector:name:object:_block_invoke_0 + 12 6 CoreFoundation 0x30e95540 ___CFXNotificationPost_block_invoke_0 + 64 7 CoreFoundation 0x30e21090 _CFXNotificationPost + 1400 8 Foundation 0x3068e3e4 -NSNotificationCenter postNotificationName:object:userInfo: + 60 9 Foundation 0x3068fc14 -NSNotificationCenter postNotificationName:object: + 24 10 UIKit 0x3387926a -UIApplication _performMemoryWarning + 74 11 UIKit 0x33879364 -UIApplication _receivedMemoryNotification + 168 12 libdispatch.dylib 0x36a12252 _dispatch_source_invoke + 510 13 libdispatch.dylib 0x36a0fb1e _dispatch_queue_invoke$VARIANT$up + 42 14 libdispatch.dylib 0x36a0fe64 _dispatch_main_queue_callback_4CF$VARIANT$up + 152 15 CoreFoundation 0x30e9c2a6 __CFRunLoopRun + 1262 16 CoreFoundation 0x30e1f49e CFRunLoopRunSpecific + 294 17 CoreFoundation 0x30e1f366 CFRunLoopRunInMode + 98 18 GraphicsServices 0x33fb6432 GSEventRunModal + 130 19 UIKit 0x336f5e76 UIApplicationMain + 1074 20 MyApp 0x00004818 main (main.m:16) 21 MyApp 0x000023b4 0x1000 + 5044 I checked and there are almost no memory leaks, e.g. when testing the app for an hour the total memory leaked was around 2-3Kb caused by some string-copying libraries. So I don't believe this is caused by the application. I guess that when the phone is not restarted for some time there are applications running in the background and when using Facebook SDK the memory becomes a problem and the system tries to recover the memory from random applications, including my application. My question is, how can I prevent this crash from happening? How should I handle unloadViewForced on a view controller to make the app more robust in low-memory conditions? And lastly, am I right that this crashlog suggests the crash occurred because the system tried to free memory and my application didn't handle it properly? Any help greatly appreciated.

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  • How to use routing in a ASP MVC website to localize in two languages - But keeping exiting URLs

    - by Anders Pedersen
    We have a couple ASP MVC websites just using the standard VS templates default settings - Working as wanted. But now I want to localize these website ( They are now in Dutch and I will add the English language ) I would like to use routing and not Resource because: 1. Languages will differ in content, numbers of pages, etc. 2. The content is mostly text. I would like the URLs to look some thing like this - www.domain.com/en/Home/Index, www.domain.nl/nl/Home/Index. But the last one should also work with - www.domain.nl/Home/Index - Witch is the exciting URLs. I have implemented Phil Haacks areas ViewEngine from this blogpost - http://haacked.com/archive/2008/11/04/areas-in-aspnetmvc.aspx. But only putting the English website in the areas and keeping the Dutch in old structure. Witch are served as Phils default fallback. But the problem is here that I have to duplicate my controllers for both language's. So I tried the work method described in this tread - http://stackoverflow.com/questions/1712167/asp-net-mvc-localization-route. It works OK with the ?en? and /nl/ but not with the old URLs. When using this code in the global.asax the URL without the culture isn't working. public static void RegisterRoutes(RouteCollection routes) { //routes.IgnoreRoute("{resource}.axd/{*pathInfo}"); routes.MapRoute( "Default", // Route name "{culture}/{controller}/{action}/{id}", // URL with parameters new { culture = "nl-NL", controller = "Home", action = "Index", id = "" } // Parameter defaults ); routes.MapRoute( "DefaultWitoutCulture", // Route name "{controller}/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = "" } // Parameter defaults ); } I properly overlooking some thing simple but I can't get this to work for me. Or are there a better way of doing this?

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  • Code Golf: Morse code

    - by LiraNuna
    The challenge The shortest code by character count, that will input a string using only alphabetical characters (upper and lower case), numbers, commas, periods and question mark, and returns a representation of the string in Morse code. The Morse code output should consist of a dash (-, ascii 0x2D) for a long beep (aka 'dah') and a dot (., ascii 0x2E) for short beep (aka 'dit'). Each letter should be separated by a space (' ', ascii 0x20), and each word should be separated by a forward slash (/, ascii 0x2F). Morse code table: Test cases: Input: Hello world Output: .... . .-.. .-.. --- / .-- --- .-. .-.. -.. Input: Hello, Stackoverflow. Output: .... . .-.. .-.. --- --..-- / ... - .- -.-. -.- --- ...- . .-. ..-. .-.. --- .-- .-.-.- Code count includes input/output (i.e full program).

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  • How is it that json serialization is so much faster than yaml serialization in python?

    - by guidoism
    I have code that relies heavily on yaml for cross-language serialization and while working on speeding some stuff up I noticed that yaml was insanely slow compared to other serialization methods (e.g., pickle, json). So what really blows my mind is that json is so much faster that yaml when the output is nearly identical. >>> import yaml, cjson; d={'foo': {'bar': 1}} >>> yaml.dump(d, Dumper=yaml.SafeDumper) 'foo: {bar: 1}\n' >>> cjson.encode(d) '{"foo": {"bar": 1}}' >>> import yaml, cjson; >>> timeit("yaml.dump(d, Dumper=yaml.SafeDumper)", setup="import yaml; d={'foo': {'bar': 1}}", number=10000) 44.506911039352417 >>> timeit("yaml.dump(d, Dumper=yaml.CSafeDumper)", setup="import yaml; d={'foo': {'bar': 1}}", number=10000) 16.852826118469238 >>> timeit("cjson.encode(d)", setup="import cjson; d={'foo': {'bar': 1}}", number=10000) 0.073784112930297852 PyYaml's CSafeDumper and cjson are both written in C so it's not like this is a C vs Python speed issue. I've even added some random data to it to see if cjson is doing any caching, but it's still way faster than PyYaml. I realize that yaml is a superset of json, but how could the yaml serializer be 2 orders of magnitude slower with such simple input?

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