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  • Android SQLite database gets corrupted

    - by Seu
    There are about 100 people using my Android App right now and every once and while I get a crash report to the server with this stack trace: android.database.sqlite.SQLiteDatabaseCorruptException: database disk image is malformed at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2596) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2621) at android.app.ActivityThread.access$2200(ActivityThread.java:126) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1932) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:123) at android.app.ActivityThread.main(ActivityThread.java:4595) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:521) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) at dalvik.system.NativeStart.main(Native Method) Caused by: android.database.sqlite.SQLiteDatabaseCorruptException: database disk image is malformed at android.database.sqlite.SQLiteQuery.native_fill_window(Native Method) at android.database.sqlite.SQLiteQuery.fillWindow(SQLiteQuery.java:75) at android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:295) at android.database.sqlite.SQLiteCursor.getCount(SQLiteCursor.java:276) at android.database.AbstractCursor.moveToPosition(AbstractCursor.java:171) at android.database.AbstractCursor.moveToFirst(AbstractCursor.java:248) The result is the app crashing and all the data in the DB being lost. One thing to note is that every time I read or write to the database I get a new SQLiteDatabase and close it as soon as I'm done. I thought this would simplify things, but perhaps that's causing the problem? Is it possible this is just a SQLite bug?

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  • Suggestions for doing async I/O with Task Parallel Library

    - by anelson
    I have some high performance file transfer code which I wrote in C# using the Async Programming Model (APM) idiom (eg, BeginRead/EndRead). This code reads a file from a local disk and writes it to a socket. For best performance on modern hardware, it's important to keep more than one outstanding I/O operation in flight whenever possible. Thus, I post several BeginRead operations on the file, then when one completes, I call a BeginSend on the socket, and when that completes I do another BeginRead on the file. The details are a bit more complicated than that but at the high level that's the idea. I've got the APM-based code working, but it's very hard to follow and probably has subtle concurrency bugs. I'd love to use TPL for this instead. I figured Task.Factory.FromAsync would just about do it, but there's a catch. All of the I/O samples I've seen (most particularly the StreamExtensions class in the Parallel Extensions Extras) assume one read followed by one write. This won't perform the way I need. I can't use something simple like Parallel.ForEach or the Extras extension Task.Factory.Iterate because the async I/O tasks don't spend much time on a worker thread, so Parallel just starts up another task, resulting in potentially dozens or hundreds of pending I/O operations; way too much! You can work around that by Waiting on your tasks, but that causes creation of an event handle (a kernel object), and a blocking wait on a task wait handle, which ties up a worker thread. My APM-based implementation avoids both of those things. I've been playing around with different ways to keep multiple read/write operations in flight, and I've managed to do so using continuations that call a method that creates another task, but it feels awkward, and definitely doesn't feel like idiomatic TPL. Has anyone else grappled with an issue like this with the TPL? Any suggestions?

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  • Recover files from corrupt filesystem

    - by Emile 81
    My situation: I have an older 80GB IDE internal hdd, with a few files on that I would like very much to recover: some word documents some latex documents (text files) and pictures (png, jpg, eps files) some other text documents and visual studio project files I had backed them (not the latex ones though) up using svn, but have not committed lately, and would loose a lot of work if I cant recover. the hdd seems to have lost its filesystem, i have no idea how it came about. I know it has/had 3 NTFS partitions, i know the files i want are on the second or third partition. I read http://superuser.com/questions/81877/recover-hard-disk-data Partition Find and Mount did not see all the partitions using intelligent scan TestDisk does (i think), I followed the step by step instructions here, but when I try to list the files it says: "Can't open filesystem, filesystem seems damaged." I'm not sure how to proceed here, as TestDisks wiki does not contain this error message afaik. I don't know if the hdd is gonna fail, or some prog has caused the filesystem to be corrupt, the hdd doesnt make a sound, so i guess that's good. I would like some guidance so I don't accidentally cause more damage. (eg. is it ok to let testdisk write the filesystem to disk? I'm pretty the partitions are listed ok, but not 100%)

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  • Deployed Qt5 Application Doesn't Print or Show Print Dialog

    - by MustacheMcLimey
    I'm experiencing Qt4 to Qt5 troubles. In my application when the user clicks the print button two things should happen, one is that a PDF gets written to disk (which still works fine in the new version, so I know that some of the printing functions are working properly) and the other is that a QPrintDialog should exec() and then send to a connected printer. I see the dialog when I launch from my development machine. The application launches on the deployed machine, but the QPrintDialog never shows and the document never prints. I am including print support. QT += core gui network webkitwidgets widgets printsupport I have been using Process Explorer to see what DLLs the application uses on my development machine, and I believe that everything is present. My application bundle includes: {myAppPath}\MyApp[MyApp.exe, Qt5PrintSupport.dll, ...] {myAppPath}\plugins\printsupport\windowsprintersupport.dll {myAppPath}\plugins\imageformats[ qgif.dll, qico.dll,qjpeg.dll, qmng.dll, qtga.dll, qtiff.dll, qwbmp.dll ] The following is the relevant code snippet: void PrintableForm::printFile() { //Writes the PDF to disk in every environment pdfCopy(); //Paper Copy only works on my dev machine QPrinter paperPrinter; QPrintDialog printDialog(&paperPrinter,this); if( printDialog.exec() == QDialog::Accepted ) { view->print(&paperPrinter); } this->accept(); } My first thought is that the relevant DLLs are not being found come print time, and that means that my application file system is incorrect, but I have not found anything that shows me a different file structure. Am I on the right track or is there something else wrong with this setup?

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  • Can you use gzip over SSL? And Connection: Keep-Alive headers

    - by magenta
    I'm evaluating the front end performance of a secure (SSL) web app here at work and I'm wondering if it's possible to compress text files (html/css/javascript) over SSL. I've done some googling around but haven't found anything specifically related to SSL. If it's possible, is it even worth the extra CPU cycles since responses are also being encrypted? Would compressing responses hurt performance? Also, I'm wanting to make sure we're keeping the SSL connection alive so we're not making SSL handshakes over and over. I'm not seeing Connection: Keep-Alive in the response headers. I do see Keep-Alive: 115 in the request headers but that's only keeping the connection alive for 115 milliseconds (seems like the app server is closing the connection after a single request is processed?) Wouldn't you want the server to be setting that response header for as long as the session inactivity timeout is? I understand browsers don't cache SSL content to disk so we're serving the same files over and over and over on subsequent visits even though nothing has changed. The main optimization recommendations are reducing the number of http requests, minification, moving scripts to bottom, image optimization, possible domain sharding (though need to weigh the cost of another SSL handshake), things of that nature.

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  • Excel export displaying '#####...'

    - by Cypher
    I'm trying to export an Excel database into .txt (Tab Delimited), but some of my cells are quite large. When I export into a txt some of the cells are exported as '#######....' which is surprisingly useless. Has this happened to anyone else? Do you know an easy fix? Data from one cell of my column: Accounting, African Studies, Agricultural/Bioresource Engineering, Agricultural Economics, Agricultural Science, Anatomy/Cell Biology, Animal Biology, Animal Science, Anthropology, Applied Zoology, Architecture, Art History, Atmospheric/Oceanic Science, Biochemistry, Biology, Botanical Sciences, Canadian Studies, Chemical Engineering, Chemistry/Bio-Organic/Environmental/Materials,ChurchMusicPerformance, Civil Engineering/Applied Mechanics, Classics, Composition, Computer Engineering,ComputerScience, ContemporaryGerman Studies, Dietetics, Early Music Performance, Earth/Planetary Sciences, East Asian Studies, Economics, Electrical Engineering, English Literature/ Drama/Theatre/Cultural Studies, Entrepreneurship, Environment, Environmental Biology, Finance, Food Science, Foundations of Computing, French Language/Linguistics/Literature/Translation, Geography, Geography/ Urban Systems, German, German Language/Literature/Culture, Hispanic Languages/Literature/Culture,History,Humanistic Studies, Industrial Relations, Information Systems, International Business, International Development Studies, Italian Studies/Medieval/Renaissance, Jazz Performance, Jewish Studies, Keyboard Studies, Kindergarten/Elementary Education, Kindergarten/Elementary Education/Jewish Studies,Kinesiology, Labor/Management Relations, Latin American/Caribbean Studies, Linguistics, Literature/Translation, Management Science, Marketing, Materials Engineering,Mathematics,Mathematics/Statistics,Mechanical Engineering, Microbiology, Microbiology/Immunology, Middle Eastern Studies, Mining Engineering, Music, Music Education, MusicHistory,Music Technology,Music Theory,North American Studies, Nutrition,OperationsManagement,OrganizationalBehavior/Human Resources Management, Performing Arts, Philosophy, Physical Education, Physics, Physiology, Plant Sciences, Political Science, Psychology, Quebec Studies, Religious Studies/Scriptures/Interpretations/World Religions,ResourceConservation,Russian, Science for Teachers,Secondary Education, Secondary Education/Music, Secondary Education/Science, SocialWork, Sociology, Software Engineering, Soil Science, Strategic Management, Teaching of French/English as a Second Language, Theology, Wildlife Biology, Wildlife Resources, Women’s Studies.

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  • XenServer 5.5 local storage problem

    - by Jason Nerer
    Hi community, I have the following problem with a Citrix XenServer 5.5. I had to physically move the host, so I shut down all machines via console: xe vm-shutdown force=true vm=my-machine-uuis-s After that I shut down the machine itself by issuing: halt After the reboot today the local storage repository is unplugged. I was trying to repair it via XenCenter, but I don't trust this one. So I tried: [root@xenserver ~]# xe pbd-list uuid ( RO) : ef6e2f3b-5825-393c-23e1-391d105c87ec host-uuid ( RO): c4bcf09c-2e52-448f-8210-df5d13bd33a9 sr-uuid ( RO): 2fb3be9c-075c-53ed-acb6-42f0c4ad0614 device-config (MRO): device: /dev/disk/by-id/scsi-SATA_WDC_WD5001ABYS-_WD-WCAS83698154,/dev/disk/by-id/scsi-SATA_WDC_WD5001ABYS-_WD-WCAS83694262 currently-attached ( RO): false To reattach the storage I issued: xe pbd-plug uuid=ef6e2f3b-5825-393c-23e1-391d105c87ec That one is running now for a while but not talking to me. The local repo has around 1TB. Should I wait, or are there any other options to reattach the local repo? What could have caused this problem? Any ideas? Thx. J

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  • File extensions and MIME Types in .NET

    - by Marc Climent
    I want to get a MIME Content-Type from a given extension (preferably without accessing the physical file). I have seen some questions about this and the methods described to perform this can be resumed in: Use registry information. Use urlmon.dll's FindMimeFromData. Use IIS information. Roll your own MIME mapping function. Based on this table, for example. I've been using no.1 for some time but I realized that the information provided by the registry is not consistent and depends on the software installed on the machine. Some extensions, like .zip don't use to have a Content-Type specified. Solution no.2 forces me to have the file on disk in order to read the first bytes, which is something slow but may get good results. The third method is based on Directory Services and all that stuff, which is something I don't like much because I have to add COM references and I'm not sure it's consistent between IIS6 and IIS7. Also, I don't know the performance of this method. Finally, I didn't want to use my own table but at the end seems the best option if I want a decent performance and consistency of the results between platforms (even Mono). Do you think there's a better option than using my own table or one of other described methods are better? What's your experience?

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  • Unable to fetch initial output of "defrag" commad in Windows Server 2008 R2 in WOW64 environment.

    - by Ganesh
    Hi All, [Application & code back ground] I have an MFC application which is executing on Windows Server 2008 R2 in WOW64 environment. In which on user input it defragments the selected drive on the disk. I initiated the process(.i.e. cmd /c defrag –v c:) of defragmentation using the CreateProcess() API, along with this to display output of the process on the main screen I created the pipe using CreatePipe() API. I used PeekNamedPipe() & ReadFile() API to get the output and display. [Problem Area] When the process is launched I am not getting the initial output as below: Microsoft Disk fragmenter Copyright © 2007 Microsoft Crop. Invoking defragmentation on (C:)…. I constantly monitor the output of the process while it is under progress but not able to get any thing as output in the pipe. It seem the process is not doing any thing and appears as if the application is not responding. But after certain period of time, once the process is about to completed I get result along with the initial data. [Sample code] //Pipe created if(0 == ::CreatePipe(&l_hStdOutRead, &l_hStdOutWrite, &l_SecurityAttribute, (DWORD)NULL)) { //Error code } //Process created/launched if (0 == ::CreateProcess(NULL, (LPTSTR)f_csProcessName, &l_stSecurityAttributes, NULL, TRUE, CREATE_NO_WINDOW, NULL,NULL, &l_StartupInfo, &l_CmdPI)) { //Error code } //Read output if (0 == ::PeekNamedPipe(m_hStdOutRead, l_cArrPeekBuffer, (DWORD)NULL, (LPDWORD)NULL, &l_dwAvailable, (LPDWORD)NULL)) { //Return to read again } if (MPLUSFALSE == ::ReadFile(m_hStdOutRead, l_cArrOutput, min(BUFFER_SIZE - 2, l_dwAvailable), &l_dwRead, NULL) || !l_dwRead) { //error code } //Display data. If any one is aware of similar problem or worked on the similar issue please let me know the solution. Thanks in Advance, Ganesh

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  • Opinions on Unladen Swallow?

    - by vartec
    What are your opinions and expectations on Google's Unladen Swallow? From their project plan: We want to make Python faster, but we also want to make it easy for large, well-established applications to switch to Unladen Swallow. Produce a version of Python at least 5x faster than CPython. Python application performance should be stable. Maintain source-level compatibility with CPython applications. Maintain source-level compatibility with CPython extension modules. We do not want to maintain a Python implementation forever; we view our work as a branch, not a fork. And even sweeter: In addition, we intend to remove the GIL and fix the state of multithreading in Python. We believe this is possible through the implementation of a more sophisticated GC It almost looks too good to be true, like the best of PyPy and Stackless combined. More info: Jesse Noller: "Pycon: Unladen-Swallow" ArsTechnica: "Google searches for holy grail of Python performance" Update: as DNS pointed out, there was related question: http://stackoverflow.com/questions/695370/what-is-llvm-and-how-is-replacing-python-vm-with-llvm-increasing-speeds-5x

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  • C# File IO with Streams - Best Memory Buffer Size

    - by AJ
    Hi, I am writing a small IO library to assist with a larger (hobby) project. A part of this library performs various functions on a file, which is read / written via the FileStream object. On each StreamReader.Read(...) pass, I fire off an event which will be used in the main app to display progress information. The processing that goes on in the loop is vaired, but is not too time consuming (it could just be a simple file copy, for example, or may involve encryption...). My main question is: What is the best memory buffer size to use? Thinking about physical disk layouts, I could pick 2k, which would cover a CD sector size and is a nice multiple of a 512 byte hard disk sector. Higher up the abstraction tree, you could go for a larger buffer which could read an entire FAT cluster at a time. I realise with today's PC's, I could go for a more memory hungry option (a couple of MiB, for example), but then I increase the time between UI updates and the user perceives a less responsive app. As an aside, I'm eventually hoping to provide a similar interface to files hosted on FTP / HTTP servers (over a local network / fastish DSL). What would be the best memory buffer size for those (again, a "best-case" tradeoff between perceived responsiveness vs. performance). Thanks in advance for any ideas, Adam

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  • Database structure - is mySQL the right choice?

    - by Industrial
    Hi everyone, We are currently planning the database structure of a quite complex e-commerce web app that has flexibility as it's main cornerstone. Our app features a large amount of data (products) and we have run into a slight headache trying to keep performance high without compromizing normalization rules in the database, or leaving our highly beloved flexibility concept behind when integrating product options (also widely known as product attributes or parameters). Based on various references and sources available, we have made up lists on pros and cons of all major and well known database patterns to solve this. After comparing these, we have come up with two final alternatives: EAV (Entity-attribute-value model) : Pros: Database is used for all sorting. Cons: All related queries will include a number of joins between multiple tables in order to complete the collection of data. SLOB (Serialized LOB, also known as Facade?) : Pros: Very flexible. Keeping the number of necessary joins low compared to a EAV design pattern. Easy to update/add/remove data from each product. Cons: All sorting will be done by the application instead of the database. Will use lots of performance (memory?) when big datasets is processed by a large number of users. Our main questions: Which pattern/structure would you use, or maybe even a different solution? Is there better databases besides mySQL available nowadays to accomplish what we want? Thanks a lot! Reference: http://stackoverflow.com/questions/695752/product-table-many-kinds-of-product-each-product-has-many-parameters

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  • Saturated addition of two signed Java 'long' values

    - by finnw
    How can one add two long values (call them x and y) in Java so that if the result overflows then it is clamped to the range Long.MIN_VALUE..Long.MAX_VALUE? For adding ints one can perform the arithmetic in long precision and cast the result back to an int, e.g.: int saturatedAdd(int x, int y) { long sum = (long) x + (long) y; long clampedSum = Math.max((long) Integer.MIN_VALUE, Math.min(sum, (long) Integer.MAX_VALUE)); return (int) clampedSum; } or import com.google.common.primitives.Ints; int saturatedAdd(int x, int y) { long sum = (long) x + (long) y; return Ints.saturatedCast(sum); } but in the case of long there is no larger primitive type that can hold the intermediate (unclamped) sum. Since this is Java, I cannot use inline assembly (in particular SSE's saturated add instructions.) It can be implemented using BigInteger, e.g. static final BigInteger bigMin = BigInteger.valueOf(Long.MIN_VALUE); static final BigInteger bigMax = BigInteger.valueOf(Long.MAX_VALUE); long saturatedAdd(long x, long y) { BigInteger sum = BigInteger.valueOf(x).add(BigInteger.valueOf(y)); return bigMin.max(sum).min(bigMax).longValue(); } however performance is important so this method is not ideal (though useful for testing.) I don't know whether avoiding branching can significantly affect performance in Java. I assume it can, but I would like to benchmark methods both with and without branching. Related: http://stackoverflow.com/questions/121240/saturating-addition-in-c

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  • Write asynchronously to file in perl

    - by Stefhen
    Basically I would like to: Read a large amount of data from the network into an array into memory. Asynchronously write this array data, running it thru bzip2 before it hits the disk. repeat.. Is this possible? If this is possible, I know that I will have to somehow read the next pass of data into a different array as the AIO docs say that this array must not be altered before the async write is complete. I would like to background all of my writes to disk in order as the bzip2 pass is going to take much longer than the network read. Is this doable? Below is a simple example of what I think is needed, but this just reads a file into array @a for testing. use warnings; use strict; use EV; use IO::AIO; use Compress::Bzip2; use FileHandle; use Fcntl; my @a; print "loading to array...\n"; while(<>) { $a[$. - 1] = $_; } print "array loaded...\n"; my $aio_w = EV::io IO::AIO::poll_fileno, EV::WRITE, \&IO::AIO::poll_cb; aio_open "./out", O_WRONLY || O_NONBLOCK, 0, sub { my $fh = shift or die "error while opening: $!\n"; aio_write $fh, undef, undef, $a, -1, sub { $_[0] > 0 or die "error: $!\n"; EV::unloop; }; }; EV::loop EV::LOOP_NONBLOCK;

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  • What is the best Binary Decision Diagram library for Java?

    - by reprogrammer
    A Binary Decision Diagram (BDD) is a data structure to represent boolean functions. I'd like use this data structure in a Java program. My search for Java based BDD libraries resulted into the following packages. Java Decision Diagram Libraries JavaBDD JDD JBDD bddbddb If you know of any other BDD libraries available for Java programs, please let me know so that I add it to the list above. If you have used any of these libraries, please tell me about your experience with the library. In particular, I'd like you to compare the available libraries along the following dimensions. Quality. Is the library mature and reasonably bug free? Performance. How do you evaluate the performance of the library? Support. Could you easily get support whenever you encountered a problem with the library? Was the library well documented? Ease of use. Was the API well designed? Could you install and use the library quickly and easily? Please mention the version of the library that you are evaluating.

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  • Software development metrics and reporting

    - by David M
    I've had some interesting conversations recently about software development metrics, in particular how they can be used in a reasonably large organisation to help development teams work better. I know there have been Stack Overflow questions about which metrics are good to use - like this one, but my question is more about which metrics are useful to which stakeholders, and at what level of aggregation. As an example, my view is that code coverage is a useful metric in the following ways (and maybe others): For a team's own internal use when combined with other measurements. For facilitating/enabling/mentoring teams, where it might be instructive when considered on a team-by-team basis as a trend (e.g. if team A and B have coverage this month of 75 and 50, I'd be more concerned with team A than B if the previous month they'd had 80 and 40). For senior management when presented as an aggregated statistic across a number of teams or a whole department. But I don't think it's useful for senior management to see this on a team-by-team basis, as this encourages artifical attempts to bolster coverage with tests that merely exercise, rather than test, code. I'm in an organisation with a couple of levels in its management hierarchy, but where the vast majority of managers are technically minded and able (with many still getting their hands dirty). Some of the development teams are leading the way in driving towards agile development practices, but others lag, and there is now a serious mandate from the top for this to be the way the organisation works. A couple of us are starting a programme to encourage this. In this sort of an organisation, what sort of metrics do you think are useful, to whom, why, and at what level of aggregation? I don't want people to feel their performance is being assessed based on a metric that they can artificially influence; at the same time, the senior management are going to want some sort of evidence that progress is being made. What advice or caveats can you provide based on experience in your own organisations? EDIT We are definitely wanting to use metrics as a tool for organisational improvement not as a tool for individual performance measurement.

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  • Best Practice, objects design ASP.NET MVC

    - by DoomStone
    Hello Stackoverflow I have a code design question that have been torbeling me for a while, you see I’m doing a refactoring of my website Cosplay Denmark, a site where cospalyers can upload images of them self in their costumes. The original site was done in php, Zend MVC, but my refactoring is being done in ASP.NET MVC 2. If you take the site http://www.cosplaydanmark.dk/Costumes/ (You can switch to English in the left column (Sprog)) Here you see a list of all the anime’s we have on the site with images, we show the name, how many different characters and how many images there are under this anime. http://www.cosplaydanmark.dk/Costumes/Bleach If you click on an anime will you get a list of characters within the given anime which we have images in, here do we show the character name, how many galleries and how many images. http://www.cosplaydanmark.dk/Costumes/Bleach/Ichigo_Kurosaki/ If you click on the character name, will you get a list of the galleries under the given character in the given anime. Here we have some information about the gallery, such as image count. http://www.cosplaydanmark.dk/Costumes/Bleach/Ichigo_Kurosaki/Admi/ Should you click the gallery do you get a list of the images in the gallery. My database look like this at the moment. As you can might imagine there are a lot of different query’s to create the site, on the first site I need to do a select on the on the “animes” table and for each result, I need to do a count select on characters and galleries. My plan to create this will be one of the following Where the IList, would be a lazy load list. But I can’t decide what would be the best solution for this would be, also if there is a better way of doing this. My priority is to have good performance with a minimum lose of features and code upkeep. I’m using a service pattern with a linq to sql repository. My design is not absolute, I’m willing to change it if it could increase performance :D I hope that I have describe my question good enough for you to understand what I mean, but ask away if there are anything I have missed.

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  • Scalable / Parallel Large Graph Analysis Library?

    - by Joel Hoff
    I am looking for good recommendations for scalable and/or parallel large graph analysis libraries in various languages. The problems I am working on involve significant computational analysis of graphs/networks with 1-100 million nodes and 10 million to 1+ billion edges. The largest SMP computer I am using has 256 GB memory, but I also have access to an HPC cluster with 1000 cores, 2 TB aggregate memory, and MPI for communication. I am primarily looking for scalable, high-performance graph libraries that could be used in either single or multi-threaded scenarios, but parallel analysis libraries based on MPI or a similar protocol for communication and/or distributed memory are also of interest for high-end problems. Target programming languages include C++, C, Java, and Python. My research to-date has come up with the following possible solutions for these languages: C++ -- The most viable solutions appear to be the Boost Graph Library and Parallel Boost Graph Library. I have looked briefly at MTGL, but it is currently slanted more toward massively multithreaded hardware architectures like the Cray XMT. C - igraph and SNAP (Small-world Network Analysis and Partitioning); latter uses OpenMP for parallelism on SMP systems. Java - I have found no parallel libraries here yet, but JGraphT and perhaps JUNG are leading contenders in the non-parallel space. Python - igraph and NetworkX look like the most solid options, though neither is parallel. There used to be Python bindings for BGL, but these are now unsupported; last release in 2005 looks stale now. Other topics here on SO that I've looked at have discussed graph libraries in C++, Java, Python, and other languages. However, none of these topics focused significantly on scalability. Does anyone have recommendations they can offer based on experience with any of the above or other library packages when applied to large graph analysis problems? Performance, scalability, and code stability/maturity are my primary concerns. Most of the specialized algorithms will be developed by my team with the exception of any graph-oriented parallel communication or distributed memory frameworks (where the graph state is distributed across a cluster).

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  • Efficient Context-Free Grammar parser, preferably Python-friendly

    - by Max Shawabkeh
    I am in need of parsing a small subset of English for one of my project, described as a context-free grammar with (1-level) feature structures (example) and I need to do it efficiently . Right now I'm using NLTK's parser which produces the right output but is very slow. For my grammar of ~450 fairly ambiguous non-lexicon rules and half a million lexical entries, parsing simple sentences can take anywhere from 2 to 30 seconds, depending it seems on the number of resulting trees. Lexical entries have little to no effect on performance. Another problem is that loading the (25MB) grammar+lexicon at the beginning can take up to a minute. From what I can find in literature, the running time of the algorithm used to parse such a grammar (Earley or CKY) should be linear to the size of the grammar and cubic to the size of the input token list. My experience with NLTK indicates that ambiguity is what hurts the performance most, not the absolute size of the grammar. So now I'm looking for a CFG parser to replace NLTK. I've been considering PLY but I can't tell whether it supports feature structures in CFGs, which are required in my case, and the examples I've seen seem to be doing a lot of procedural parsing rather than just specifying a grammar. Can anybody show me an example of PLY both supporting feature structs and using a declarative grammar? I'm also fine with any other parser that can do what I need efficiently. A Python interface is preferable but not absolutely necessary.

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  • Changing App.config at Runtime

    - by born to hula
    I'm writing a test winforms / C# / .NET 3.5 application for the system we're developing and we fell in the need to switch between .config files at runtime, but this is turning out to be a nightmare. Here's the scene: the Winforms application is aimed at testing a WebApp, divided into 5 subsystems. The test proccess works with messages being sent between the subsystems, and for this proccess to be sucessful each subsystem got to have its own .config file. For my Test Application I wrote 5 separate configuration files. I wish I was able to switch between these 5 files during runtime, but the problem is: I can programatically edit the application .config file inumerous times, but these changes will only take effect once. I've been searching a long time for a form to address this problem but I still wasn't sucessful. I know the problem definition may be a bit confusing but I would really appreciate it if someone helped me. Thanks in advance! --- UPDATE 01-06-10 --- There's something I didn't mention before. Originally, our system is a Web Application with WCF calls between each subsystem. For performance testing reasons (we're using ANTS 4), we had to create a local copy of the assemblies and reference them from the test project. It may sound a bit wrong, but we couldn't find a satisfying way to measure performance of a remote application. --- End Update --- Here's what I'm doing: public void UpdateAppSettings(string key, string value) { XmlDocument xmlDoc = new XmlDocument(); xmlDoc.Load(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile); foreach (XmlElement item in xmlDoc.DocumentElement) { foreach (XmlNode node in item.ChildNodes) { if (node.Name == key) { node.Attributes[0].Value = value; break; } } } xmlDoc.Save(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile); System.Configuration.ConfigurationManager.RefreshSection("section/subSection"); }

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  • java distributed cache for low latency, high availability

    - by Shahbaz
    I've never used distributed caches/DHTs like memcached, jboss cache, ehcache, etc. I'm wondering which, if any, is appropriate for my use. First, I'm not doing web applications (as most of these project seem to be geared towards web apps). I write servers (Order Management Systems actually) for financial trading firms. The servers themselves are not too complicated. They need to receive information (market data, orders, executions, etc.) rout them to their destination while possibly transforming some of these messages. I am looking at these products to solve the following problems: * Safe repository of the state of the server. I'd rather build the logic of my application as a bunch of transformers (similar to Apache Camel) and store the state in a 'safe' place * This repository should be distributed: in case one of these data stores crashes, one or two more should be up and I should be able to switch to them seamlessly * This repository should be fast. Single digits milliseconds count here, in other words, systems which consume/process this data are automated systems, not humans clicking on links. This system needs to have high-throughput and low latency. By sending my data outside the process, I am necessarily slowing performance, but I am trying to balance absolute raw speed and absolute protection of data. * This repository should be safe. Similar to the point about several on-line backups, this system needs to write data to disk (potentially more than one disk). I'd really like to stop writing my own 'transaction servers.' Am I correct to be looking into projects such as jboss cache, ehcache, etc.? Thanks

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  • What are alternatives to Win32 PulseEvent() function?

    - by Bill
    The documentation for the Win32 API PulseEvent() function (kernel32.dll) states that this function is “… unreliable and should not be used by new applications. Instead, use condition variables”. However, condition variables cannot be used across process boundaries like (named) events can. I have a scenario that is cross-process, cross-runtime (native and managed code) in which a single producer occasionally has something interesting to make known to zero or more consumers. Right now, a well-known named event is used (and set to signaled state) by the producer using this PulseEvent function when it needs to make something known. Zero or more consumers wait on that event (WaitForSingleObject()) and perform an action in response. There is no need for two-way communication in my scenario, and the producer does not need to know if the event has any listeners, nor does it need to know if the event was successfully acted upon. On the other hand, I do not want any consumers to ever miss any events. In other words, the system needs to be perfectly reliable – but the producer does not need to know if that is the case or not. The scenario can be thought of as a “clock ticker” – i.e., the producer provides a semi-regular signal for zero or more consumers to count. And all consumers must have the correct count over any given period of time. No polling by consumers is allowed (performance reasons). The ticker is just a few milliseconds (20 or so, but not perfectly regular). Raymen Chen (The Old New Thing) has a blog post pointing out the “fundamentally flawed” nature of the PulseEvent() function, but I do not see an alternative for my scenario from Chen or the posted comments. Can anyone please suggest one? Please keep in mind that the IPC signal must cross process boundries on the machine, not simply threads. And the solution needs to have high performance in that consumers must be able to act within 10ms of each event.

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  • PHP, jQuery and Ajax Object Orientation

    - by pastylegs
    I'm a fairly experienced programmer getting my head around PHP and Ajax for the first time, and I'm having a bit of trouble figuring out how to incorperate object oriented PHP into my ajax webapp. I have an admin page (admin.php) that will load and write information (info.xml) from an XML file depending on the users selection of a form on the admin page. I have decided to use an object (ContentManager.php) to manage the loading and writing of the XML file to disk, i.e : class ContentManager{ var $xml_attribute_1 ... function __construct(){ //load the xml file from disk and save its contents into variables $xml_attribute = simplexml_load_file(/path/to/xml) } function get_xml_contents(){ return xml_attribute; } function write_xml($contents_{ } function print_xml(){ } } I create the ContentManager object in admin.php like so <?php include '../includes/CompetitionManager.php'; $cm = new CompetitionManager() ?> <script> ...all my jquery </script> <html> ... all my form elements </html> So now I want to use AJAX to allow the user to retrieve information from the XML file via the ContentManger app using an interface (ajax_handler.php) like so <?php if(_POST[]=="get_a"){ }else if() } ... ?> I understand how this would work if I wasn't using objects, i.e. the hander php file would do a certain action depending on a variable in the .post request, but with my setup, I can't see how I can get a reference to the ContentManager object I have created in admin.php in the ajax_handler.php file? Maybe my understanding of php object scope is flawed. Anyway, if anyone can make sense of what I'm trying to do, I would appreciate some help!

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  • Better why of looping to detect change.

    - by Dremation
    As of now I'm using a while(true) method to detect changes in memory. The problem with this is it's kill the applications performance. I have a list of 30 pointers that need checked as rapidly as possible for changes, without sacrificing a huge performance loss. Anyone have ideas on this? memScan = new Thread(ScanMem); public static void ScanMem() { int i = addy.Length; while (true) { Thread.Sleep(30000); //I do this to cut down on cpu usage for (int j = 0; j < i; j++) { string[] values = addy[j].Split(new char[] { Convert.ToChar(",") }); //MessageBox.Show(values[2]); try { if (Memory.Scanner.getIntFromMem(hwnd, (IntPtr)Convert.ToInt32(values[0], 16), 32).ToString() != values[1].ToString()) { //Ok, it changed lets do our work //work if (Globals.Working) return; SomeFunction("Results: " + values[2].ToString(), "Memory"); Globals.Working = true; }//end if }//end try catch { } }//end for }//end while }//end void

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  • Product Catalog Schema design

    - by FlySwat
    I'm building a proof of concept schema for a product catalog to possibly replace a very aging and crufty one we use. In our business, we sell both physical materials and services (one time and reoccurring charges). The current catalog schema has each distinct category broken out into individual tables, while this is nicely normalized and performs well, it is fairly difficult to extend. Adding a new attribute to a particular product involves changing the table schema and backpopulating old data. An idea I've been toying with has been something along the line of a base set of entity tables in 3rd normal form, these will contain the facts that are common among ALL products. Then, I'd like to build an Attribute-Entity-Value schema that allows each entity type to be extended in a flexible way using just data and no schema changes. Finally, I'd like to denormalize this data model into materialized views for each individual entity type. This views are what the application would access. We also have many tables that contain business rules and compatibility rules. These would join against the base entity tables instead of the views. My big concerns here are: Performance - Attribute-Entity-Value schemas are flexible, but typically perform poorly, should I be concerned? More Performance - Denormalizing using materialized views may have some risks, I'm not positive on this yet. Complexity - While this schema is flexible and maintainable using just data, I worry that the complexity of the design might make future schema changes difficult. For those who have designed product catalogs for large scale enterprises, am I going down the totally wrong path? Is there any good best practice schema design reading available for product catalogs?

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