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  • Writing a DBMS in Python

    - by Matt Luongo
    Hey guys, I'm working on a basic DBMS as a pet project and planning to prototype in Python. I figure there's a reason there are only a few Python databases, and my gut agrees that my favorite language will be too slow to act as an honest performing database, but I'm looking forward to using it to learn what I need quickly. Would someone please contradict me? Is Python as ill-suited right now for this sort of thing as I think?

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  • Hibernate orm for a view

    - by EugeneP
    How do you ORM a view? Is there any difference with a table in terms of reverse engineering? In my case, I have a whole pile of joined tables that will be read-only in an application. So, if I need sort of a 1 Object with all collections in proper order, instead of long chains of relationships - collection with another etc, it'll be simpler. What do you think and how do you accomplish this?

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  • mysql query for getting all messages that belong to user's contacts

    - by aharon
    So I have a database that is setup sort of like this (simplified, and in terms of the tables, all are InnoDBs): Users: contains based user authentication information (uid, username, encrypted password, et cetera) Contacts: contains two rows per relationship that exists between users as (uid1, uid2), (uid2, uid1) to allow for a good 1:1 relationship (must be mutual) between users Messages: has messages that consist of a blob, owner-id, message-id (auto_increment) So my question is, what's the best MySQL query to get all messages that belong to all the contacts of a specific user? Is there an efficient way to do this?

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  • Read variable-length records from a buffer - weird memory issues

    - by bsg
    Hi, I'm trying to implement an i/o intensive quicksort (C++ qsort) on a very large dataset. In the interests of speed, I'd like to read in a chunk of data at a time into a buffer and then use qsort to sort it inside the buffer. (I am currently working with text files but would like to move to binary soon.) However, my data is composed of variable-length records, and qsort needs to be told the length of the record in order to sort. Is there any way to standardize this? The only thing I could think of was rather convoluted: my program currently reads from the buffer until it hits a linefeed character ('10' in ascii), transferring each character over to another array. When it finds a linefeed (the delimiter in the input file), it fills the number of spaces remaining in the buffer for that record (record size is set to 30) with null characters. This way, I should end up with a buffer full of fixed-size records to give qsort. I know there are several problems with my approach, one being that it's just clumsy, another that the record size might conceivably be larger than 30, but is generally much less. Is there a better way of doing this? As well, my current code doesn't even work. When I debug it, it seems to be transferring characters from one buffer to the other, but when I try to print out the buffer, it contains only the first record. Here is my code: FILE *fp; unsigned char *buff; unsigned char *realbuff; FILE *inputFiles[NUM_INPUT_FILES]; buff = (unsigned char *) malloc(2048); realbuff = (unsigned char *) malloc(NUM_RECORDS * RECORD_SIZE); fp = fopen("postings0.txt", "r"); if(fp) { fread(buff, 1, 2048, fp); /*for(int i=0; i <30; i++) cout << buff[i] <<endl;*/ int y=0; int recordcounter = 0; //cout << buff; for(int i=0;i <100; i++) { if(buff[i] != char(10)) { realbuff[y] = buff[i]; y++; recordcounter++; } else { if(recordcounter < RECORD_SIZE) for(int j=recordcounter; j < RECORD_SIZE;j++) { realbuff[y] = char(0); y++; } recordcounter = 0; } } cout << realbuff <<endl; cout << buff; } else cout << "sorry"; Thank you very much, bsg

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  • What's a good library to do computational geometry (like CGAL) in a garbage-collected language?

    - by Squash Monster
    I need a library to handle computational geometry in a project, especially boolean operations, but just about every feature is useful. The best library I can find for this is CGAL, but this is the sort of project I would hesitate to make without garbage collection. What language/library pairs can you recommend? So far my best bet is importing CGAL into D. There is also a project for making Python bindings for CGAL, but it's very incomplete.

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  • cuda/thrust: Trying to sort_by_key 2.8GB of data in 6GB of gpu RAM throws bad_alloc

    - by Sven K
    I have just started using thrust and one of the biggest issues I have so far is that there seems to be no documentation as to how much memory operations require. So I am not sure why the code below is throwing bad_alloc when trying to sort (before the sorting I still have 50% of GPU memory available, and I have 70GB of RAM available on the CPU)--can anyone shed some light on this? #include <thrust/device_vector.h> #include <thrust/sort.h> #include <thrust/random.h> void initialize_data(thrust::device_vector<uint64_t>& data) { thrust::fill(data.begin(), data.end(), 10); } #define BUFFERS 3 int main(void) { size_t N = 120 * 1024 * 1024; char line[256]; try { std::cout << "device_vector" << std::endl; typedef thrust::device_vector<uint64_t> vec64_t; // Each buffer is 900MB vec64_t c[3] = {vec64_t(N), vec64_t(N), vec64_t(N)}; initialize_data(c[0]); initialize_data(c[1]); initialize_data(c[2]); std::cout << "initialize_data finished... Press enter"; std::cin.getline(line, 0); // nvidia-smi reports 48% memory usage at this point (2959MB of // 6143MB) std::cout << "sort_by_key col 0" << std::endl; // throws bad_alloc thrust::sort_by_key(c[0].begin(), c[0].end(), thrust::make_zip_iterator(thrust::make_tuple(c[1].begin(), c[2].begin()))); std::cout << "sort_by_key col 1" << std::endl; thrust::sort_by_key(c[1].begin(), c[1].end(), thrust::make_zip_iterator(thrust::make_tuple(c[0].begin(), c[2].begin()))); } catch(thrust::system_error &e) { std::cerr << "Error: " << e.what() << std::endl; exit(-1); } return 0; }

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  • Cleanest way to build an SQL string in Java

    - by Vidar
    I want to build an SQL string to do database manipulation (updates, deletes, inserts, selects, that sort of thing) - instead of the awful string concat method using millions of "+"'s and quotes which is unreadable at best - there must be a better way. I did think of using MessageFormat - but its supposed to be used for user messages, although I think it would do a reasonable job - but I guess there should be something more aligned to SQL type operations in the java sql libraries. Would Groovy be any good? Any help much appreciated.

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  • Hosting a VST/DX instrument in C#/C++?

    - by James D
    I'm trying to get a read on the effort level involved in building a barebones virtual instrument host in C++ or C# but I haven't been able to get any hard information. Does anybody know any good starter apps, tutorials, helper libraries for this sort of thing? If it matters, the goal would be to a) accept incoming MIDI events and b) dispatch them to the virtual instrument. In C++ or C#, if possible. Thanks!

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  • .NET XBox Live Account API

    - by Adam Haile
    Is there a .NET API available to get data from your XBox Live account? All I'm really interested in is who's online, but messages would be cool too. And some sort of event driven notifications of user sign-on would be great, but I'll poll if need be.

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  • Service Layer which can switch between Web Service Layer and Data Access Layer

    - by Blake Blackwell
    I am building an application that will function as a client-server application, and also as a disconnected client application. I will be using WPF (browser app for client-server application). When interacting with the server's database, I will need to connect using WCF web services. When connecting with the localized database, I will need to connect using the local db's data access layer. What methods/patterns exist for this sort of architecture?

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  • I want to scrape a site using GAE and post the results into a Google Entity

    - by cozza
    I want to scrape this URL : https://www.xstreetsl.com/modules.php?searchSubmitImage_x=0&searchSubmitImage_y=0&SearchLocale=0&name=Marketplace&SearchKeyword=business&searchSubmitImage.x=0&searchSubmitImage.y=0&SearchLocale=0&SearchPriceMin=&SearchPriceMax=&SearchRatingMin=&SearchRatingMax=&sort=&dir=asc Go into each of the links and extract out various pieces of information e.g. permissions, prims etc then post the results into a Entity on google app engine. I want to know the best way to go about it? Chris

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  • jQuery plugin to put a twitter feed on my site

    - by Horace Loeb
    I want to put the first n entries from my twitter feed on my blog with the usual enhancements: Convert URLs to real links Remove @ replies I realize this wouldn't be too difficult to code from scratch with $.getJSON, but since this sort of thing is so common, I was wondering if there was a neat plugin that would handle everything for me.

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  • Blank page shown in Mozilla Firefox

    - by Arun
    I have a jsf page which works perfectly fine[Both in IE and Mozilla Firefox] when the application is deployed locally. But i deploy it at the client place and I try to access the page in mozilla FF i get a blank page but it shows up properly in IE. Now if i do a remote desktop connection to the system where the application is deployed and try to access the same page i get to see the page correctly in both mozilla ff & IE Is this due to some sort of network issue specific to mozilla?

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  • Are vb.net eventArgs maintained at a "system" level?

    - by GregH
    I have a custom developed control I am using that somebody else wrote. For some reason, when the control was written, they did not write an event handler for the "mouseDown" event so when I mouseDown on the control, no event is fired. What I am basically trying to do is capture which mouse button (left or right) is pressed when the control is clicked on. Is there any sort of system level objects that maintain system state (including which mouse buttons are currently being pressed regardless of the control being clicked upon?)

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  • C++ Program Always Crashes While doing a std::string assign

    - by bbazso
    I have been trying to debug a crash in my application that crashes (i.e. asserts a * glibc detected free(): invalid pointer: 0x000000000070f0c0 **) while I'm trying to do a simple assign to a string. Note that I'm compiling on a linux system with gcc 4.2.4 with an optimization level set to -O2. With -O0 the application no longer crashes. E.g. std::string abc; abc = "testString"; but if I changed the code as follows it no longer crashes std::string abc("testString"); So again I scratched my head! But the interesting pattern was that the crash moved later on in the application, AGAIN at another string. I found it weird that the application was continuously crashing on a string assign. A typical crash backtrace would look as follows: #0 0x00007f2c2663bfb5 in raise () from /lib64/libc.so.6 (gdb) bt #0 0x00007f2c2663bfb5 in raise () from /lib64/libc.so.6 #1 0x00007f2c2663dbc3 in abort () from /lib64/libc.so.6 #2 0x00000000004d8cb7 in people_streamingserver_sighandler (signum=6) at src/peoplestreamingserver.cpp:487 #3 <signal handler called> #4 0x00007f2c2663bfb5 in raise () from /lib64/libc.so.6 #5 0x00007f2c2663dbc3 in abort () from /lib64/libc.so.6 #6 0x00007f2c26680ce0 in ?? () from /lib64/libc.so.6 #7 0x00007f2c270ca7a0 in std::string::assign (this=0x7f2c21bc8d20, __str=<value optimized out>) at /home/bbazso/ThirdParty/sources/gcc-4.2.4/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:238 #8 0x00007f2c21bd874a in PEOPLESProtocol::GetStreamName (this=<value optimized out>, pRawPath=0x2342fd8 "rtmp://127.0.0.1/mp4:pop.mp4", lStreamName=@0x7f2c21bc8d20) at /opt/trx-HEAD/gcc/4.2.4/lib/gcc/x86_64-pc-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/basic_string.h:491 #9 0x00007f2c21bd9daa in PEOPLESProtocol::SignalProtocolCreated (pProtocol=0x233a4e0, customParameters=@0x7f2c21bc8de0) at peoplestreamer/src/peoplesprotocol.cpp:240 This was really weird behavior and so I started to poke around further in my application to see if there was some sort of memory corruption (either heap or stack) error that could be occurring that could be causing this weird behavior. I even checked for ptr corruptions and came up empty handed. In addition to visual inspection of the code I also tried the following tools: Valgrind using both memcheck and exp-ptrcheck electric fence libsafe I compiled with -fstack-protector-all in gcc I tried MALLOC_CHECK_ set to 2 I ran my code through lint checks as well as cppcheck (to check for mistakes) And I stepped through the code using gdb So I tried a lot of stuff and still came up empty handed. So I was wondering if it could be something like a linker issue or a library issue of some sort that could be causing this problem. Are there any know issues with the std::string that make is susceptible to crashing in -O2 or maybe it has nothing to do with the optimization level? But the only pattern that I can see thus far in my problem is that it always seems to crash on a string and so I was wondering if anyone knew of any issues that my be causing this type of behavior. Thanks a lot!

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  • Tool for debugging KVO/Bindings in Cocoa

    - by Raphael Sebbe
    Is there any tool to log current observers of a given object, in the spirit of what "gdb info gc-roots" does? I found "gdb info gc-references" could do that (sort of) as a by-product of its original purpose, but that won't work with non garbage collected apps. Thanks!

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  • G++, compiler warnings, c++ templates

    - by Ian
    During the compilatiion of the C++ program those warnings appeared: c:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bc:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bits/stl_algo.h:2317: instantiated from `void std::partial_sort(_RandomAccessIterator, _RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Object<double>**, std::vector<Object<double>*, std::allocator<Object<double>*> > >, _Compare = sortObjects<double>]' c:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bits/stl_algo.h:2506: instantiated from `void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Object<double>**, std::vector<Object<double>*, std::allocator<Object<double>*> > >, _Size = int, _Compare = sortObjects<double>]' c:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bits/stl_algo.h:2589: instantiated from `void std::sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Object<double>**, std::vector<Object<double>*, std::allocator<Object<double>*> > >, _Compare = sortObjects<double>]' io/../structures/objects/../../algorithm/analysis/../../structures/list/ObjectsList.hpp:141: instantiated from `void ObjectsList <T>::sortObjects(unsigned int, T, T, T, T, unsigned int) [with T = double]' I do not why, because all objects have only template parameter T, their local variables are also T. The only place, where I am using double is main. There are objects of type double creating and adding into the ObjectsList... Object <double> o1; ObjectsList <double> olist; olist.push_back(o1); .... T xmin = ..., ymin = ..., xmax = ..., ymax = ...; unsigned int n = ...; olist.sortAllObjects(xmin, ymin, xmax, ymax, n); and comparator template <class T> class sortObjects { private: unsigned int n; T xmin, ymin, xmax, ymax; public: sortObjects ( const T xmin_, const T ymin_, const T xmax_, const T ymax_, const int n_ ) : xmin ( xmin_ ), ymin ( ymin_ ), xmax ( xmax_ ), ymax ( ymax_ ), n ( n_ ) {} bool operator() ( const Object <T> *o1, const Object <T> *o2 ) const { T dmax = (std::max) ( xmax - xmin, ymax - ymin ); T x_max = ( xmax - xmin ) / dmax; T y_max = ( ymax - ymin ) / dmax; ... return ....; } representing ObjectsList method: template <class T> void ObjectsList <T> ::sortAllObjects ( const T xmin, const T ymin, const T xmax, const T ymax, const unsigned int n ) { std::sort ( objects.begin(), objects.end(), sortObjects <T> ( xmin, ymin, xmax, ymax, n ) ); }

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  • Why the double.Parse throw error in live server and how to track?

    - by Kovu
    Hi, I build a website, that: reads data from a website by HttpWebRequest Sort all Data Parse values of the data and give out newly On local server it works perfect, but when I push it to my live server, the double.Parse fails with an error. So: - how to track what the double.parse is trying to parse? - how to debug live server? Lang is ASP.Net / C#.net 2.0

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  • Email notification when an error occurs

    - by user279521
    I need to design a bug alert system, where the web support team is notified via email when a user of our website encounters an error of any sort (database exception, or a 404) What would be the best way to design this section of the project? Any ideas would be appreciated.

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