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  • Tricking the server to load files faster?

    - by Yongho
    If we have a website with multiple images and videos, I've read that it's best to serve them from other domains so that the browser can simultaneously download a bunch of files, rather than waiting one by one for each file to be downloaded. For example, if we have a website http://example.com/, we might consider serving: Videos from http://video.example.com/ Images from http://images.example.com/ etc. Question: can we achieve the simultaneous downloading by tricking the browser into believing that the files are hosted there, or do they actually need to be at that location? We can, for example, pretend to serve video from http://video.example.com/ when actually it's just a clever htaccess rewrite that ACTUALLY serves from http://example.com/video.php. In this case, the video is being served from the main domain but because we refer it as http://video.example.com/, it may think that it's another domain and thus load files simultaneously, rather than one by one. Is this feasible?

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  • i want to search my database for example i want to search the word "google yahoo"

    - by user2926370
    i want to search my database for example i want to search the word "google yahoo" and when i enter that i should able to look the rows which has google and yahoo. It is not required to be in the same order and google besides yahoo. No matter wherever it is in the line and give me a simple logic to it. i can able to query that thing.something like select * from table where column like("%google%yahoo%"). I want to develop this thing in php but how can i insert %. Do i need to use if statement so that i can insert % in between the words whenever i find spaces orelse is there any other logic to do it simpler?

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  • How large is a "buffer" in PostgreSQL

    - by Konrad Garus
    I am using pg_buffercache module for finding hogs eating up my RAM cache. For example when I run this query: SELECT c.relname, count(*) AS buffers FROM pg_buffercache b INNER JOIN pg_class c ON b.relfilenode = c.relfilenode AND b.reldatabase IN (0, (SELECT oid FROM pg_database WHERE datname = current_database())) GROUP BY c.relname ORDER BY 2 DESC LIMIT 10; I discover that sample_table is using 120 buffers. How much is 120 buffers in bytes?

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  • Suggested (simple) approach for drawing large numbers of visual elements in WPF?

    - by Ender
    I'm writing an interface that features a large (~50000px width) "canvas"-type area that is used to display a lot of data in a fairly novel way. This involves lots of lines, rectangles, and text. The user can scroll around to explore the entire canvas. At the moment I'm just using a standard Canvas panel with various Shapes placed on it. This is nice and easy to do: construct a shape, assign some coordinates, and attach it to the Canvas. Unfortunately, it's pretty slow (to construct the children, not to do the actual rendering). I've looked into some alternatives, it's a bit intimidating. I don't need anything fancy - just the ability to efficiently construct and place objects in a coordinate plane. If all I get are lines, colored rectangles, and text, I'll be happy. Do I need Geometry instances inside of Geometry Groups inside of GeometryDrawings inside of some Panel container? Note: I'd like to include text and graphics (i.e. colored rectangles) in the same space, if possible.

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  • What's the fastest way to check if a word from one string is in another string?

    - by Mike Trpcic
    I have a string of words; let's call them bad: bad = "foo bar baz" I can keep this string as a whitespace separated string, or as a list: bad = bad.split(" "); If I have another string, like so: str = "This is my first foo string" What's the fasted way to check if any word from the bad string is within my comparison string, and what's the fastest way to remove said word if it's found? #Find if a word is there bad.split(" ").each do |word| found = str.include?(word) end #Remove the word bad.split(" ").each do |word| str.gsub!(/#{word}/, "") end

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  • Question about Cost in Oracle Explain Plan

    - by Will
    When Oracle is estimating the 'Cost' for certain queries, does it actually look at the amount of data (rows) in a table? For example: If I'm doing a full table scan of employees for name='Bob', does it estimate the cost by counting the amount of existing rows, or is it always a set cost?

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  • What limits scaling in this simple OpenMP program?

    - by Douglas B. Staple
    I'm trying to understand limits to parallelization on a 48-core system (4xAMD Opteron 6348, 2.8 Ghz, 12 cores per CPU). I wrote this tiny OpenMP code to test the speedup in what I thought would be the best possible situation (the task is embarrassingly parallel): // Compile with: gcc scaling.c -std=c99 -fopenmp -O3 #include <stdio.h> #include <stdint.h> int main(){ const uint64_t umin=1; const uint64_t umax=10000000000LL; double sum=0.; #pragma omp parallel for reduction(+:sum) for(uint64_t u=umin; u<umax; u++) sum+=1./u/u; printf("%e\n", sum); } I was surprised to find that the scaling is highly nonlinear. It takes about 2.9s for the code to run with 48 threads, 3.1s with 36 threads, 3.7s with 24 threads, 4.9s with 12 threads, and 57s for the code to run with 1 thread. Unfortunately I have to say that there is one process running on the computer using 100% of one core, so that might be affecting it. It's not my process, so I can't end it to test the difference, but somehow I doubt that's making the difference between a 19~20x speedup and the ideal 48x speedup. To make sure it wasn't an OpenMP issue, I ran two copies of the program at the same time with 24 threads each (one with umin=1, umax=5000000000, and the other with umin=5000000000, umax=10000000000). In that case both copies of the program finish after 2.9s, so it's exactly the same as running 48 threads with a single instance of the program. What's preventing linear scaling with this simple program?

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  • Code runs 6 times slower with 2 threads than with 1

    - by Edward Bird
    So I have written some code to experiment with threads and do some testing. The code should create some numbers and then find the mean of those numbers. I think it is just easier to show you what I have so far. I was expecting with two threads that the code would run about 2 times as fast. Measuring it with a stopwatch I think it runs about 6 times slower! void findmean(std::vector<double>*, std::size_t, std::size_t, double*); int main(int argn, char** argv) { // Program entry point std::cout << "Generating data..." << std::endl; // Create a vector containing many variables std::vector<double> data; for(uint32_t i = 1; i <= 1024 * 1024 * 128; i ++) data.push_back(i); // Calculate mean using 1 core double mean = 0; std::cout << "Calculating mean, 1 Thread..." << std::endl; findmean(&data, 0, data.size(), &mean); mean /= (double)data.size(); // Print result std::cout << " Mean=" << mean << std::endl; // Repeat, using two threads std::vector<std::thread> thread; std::vector<double> result; result.push_back(0.0); result.push_back(0.0); std::cout << "Calculating mean, 2 Threads..." << std::endl; // Run threads uint32_t halfsize = data.size() / 2; uint32_t A = 0; uint32_t B, C, D; // Split the data into two blocks if(data.size() % 2 == 0) { B = C = D = halfsize; } else if(data.size() % 2 == 1) { B = C = halfsize; D = hsz + 1; } // Run with two threads thread.push_back(std::thread(findmean, &data, A, B, &(result[0]))); thread.push_back(std::thread(findmean, &data, C, D , &(result[1]))); // Join threads thread[0].join(); thread[1].join(); // Calculate result mean = result[0] + result[1]; mean /= (double)data.size(); // Print result std::cout << " Mean=" << mean << std::endl; // Return return EXIT_SUCCESS; } void findmean(std::vector<double>* datavec, std::size_t start, std::size_t length, double* result) { for(uint32_t i = 0; i < length; i ++) { *result += (*datavec).at(start + i); } } I don't think this code is exactly wonderful, if you could suggest ways of improving it then I would be grateful for that also.

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  • Why does dojo parsing time depend on css and images availability?

    - by Kniganapolke
    I have been profiling javascript on my page that uses dojo widgets. I don't use explicit parsing - the parser runs on page load. What I noticed is that if I clear browser cache before refreshing the page, dojo parsing takes much more time than if all the files are already cached. Note that we build all the required dojo modules into a layer (a single file), so we don't lazy-load any js files. I wonder if dojo parsing process depends on images and css resources, as far as I know it only instantiates widgets and injects dom nodes. Do you have any ideas why dojo parser runs longer (2-3 times longer in my case) when the cache is cleared?

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  • SQL Server query problem

    - by user335160
    I want to achieved the results shown in the attached image. The Table Structure and Data are the ffg below: Table Relationship Overall IB Limit->one to many-> Facility Limit Facility Limit->one to many-> Facility Sub Limit Tables Structure and Data Overall IB Limit Id SCAF Reference Approval Date 1 NEW-001 January 1, 2011 2 NEW-002 January 2, 2011 3 NEW-003 January 3, 2011 ---------------------------- Facility Limit Id OverallIBLimitId Product Type 1 1 RPA 2 1 CG 3 2 RPA 4 3 CG ---------------------------- Facility Sub Limit Id FacilityLimitId Sub-Limit Type Amount Tenor Status Status Date 1 1 RPA at max 2,000,0000.00 2 months Approved January 5, 2011 2 1 Oil 3,000,0000.00 3 yrs Approved January 5, 2011 3 2 CG at minor 4,000,0000.00 1 yr Approved January 5, 2011 4 2 CG at max 5,000,0000.00 6 months Approved January 5, 2011 5 2 Flood Component 1 5,000,0000.00 6 months Approved January 5, 2011 6 2 Flood Component 2 6,000,0000.00 3 yrs Approved January 5, 2011 7 3 RPA at minor 1,000,0000.00 6 months Approved January 5, 2011 8 4 One-Off 1,000,0000.00 6 months Approved January 5, 2011

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  • Parsing a CSV File to a Rails Database

    - by Schroedinger
    G'day guys, I'm using fasterCSV and a rake script to parse a csv with about 30 columns into my rails db for a 'Trade' item. The script works fine when all of the values are set to strings, but when I change it to a decimal, int or other value, everything goes to hell. Wondering if fasterCSV has built in int etc parsing or whether I'll have to manage these within my model. Basically, I'm given a giant amount of trades data, need to import it, and then need to provide feedback with say the average trade volume, the times, etc. I understand I can do that all with the wonderful records provided to me by activeRecord but wondered if there was an easier way to populate a rather large Database with a given CSV? Several of the fields don't have values for certain rows, fasterCSV seems to work perfectly when they're all strings, but not when I try to get decimal or other.

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  • STL find performs bettern than hand-crafter loop

    - by dusha
    Hello all, I have some question. Given the following C++ code fragment: #include <boost/progress.hpp> #include <vector> #include <algorithm> #include <numeric> #include <iostream> struct incrementor { incrementor() : curr_() {} unsigned int operator()() { return curr_++; } private: unsigned int curr_; }; template<class Vec> char const* value_found(Vec const& v, typename Vec::const_iterator i) { return i==v.end() ? "no" : "yes"; } template<class Vec> typename Vec::const_iterator find1(Vec const& v, typename Vec::value_type val) { return find(v.begin(), v.end(), val); } template<class Vec> typename Vec::const_iterator find2(Vec const& v, typename Vec::value_type val) { for(typename Vec::const_iterator i=v.begin(), end=v.end(); i<end; ++i) if(*i==val) return i; return v.end(); } int main() { using namespace std; typedef vector<unsigned int>::const_iterator iter; vector<unsigned int> vec; vec.reserve(10000000); boost::progress_timer pt; generate_n(back_inserter(vec), vec.capacity(), incrementor()); //added this line, to avoid any doubts, that compiler is able to // guess the data is sorted random_shuffle(vec.begin(), vec.end()); cout << "value generation required: " << pt.elapsed() << endl; double d; pt.restart(); iter found=find1(vec, vec.capacity()); d=pt.elapsed(); cout << "first search required: " << d << endl; cout << "first search found value: " << value_found(vec, found)<< endl; pt.restart(); found=find2(vec, vec.capacity()); d=pt.elapsed(); cout << "second search required: " << d << endl; cout << "second search found value: " << value_found(vec, found)<< endl; return 0; } On my machine (Intel i7, Windows Vista) STL find (call via find1) runs about 10 times faster than the hand-crafted loop (call via find2). I first thought that Visual C++ performs some kind of vectorization (may be I am mistaken here), but as far as I can see assembly does not look the way it uses vectorization. Why is STL loop faster? Hand-crafted loop is identical to the loop from the STL-find body. I was asked to post program's output. Without shuffle: value generation required: 0.078 first search required: 0.008 first search found value: no second search required: 0.098 second search found value: no With shuffle (caching effects): value generation required: 1.454 first search required: 0.009 first search found value: no second search required: 0.044 second search found value: no Many thanks, dusha. P.S. I return the iterator and write out the result (found or not), because I would like to prevent compiler optimization, that it thinks the loop is not required at all. The searched value is obviously not in the vector.

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  • How can I limit the number of connections to an mssql server from my tomcat deployed java applicatio

    - by CJ
    Hi, I have an application that is deployed on tomcat on server A and sends queries to a huge variety of mssql databases on an server B. I am concerned that my application could overload this mssql database server and would like some way to preventing it making requests to connect to any database on that server if some arbitrary number of connections were already in existence and unclosed. I am looking at using connection pooling but am under the impression that this will only pool connections to a specific database on the mssql server, I want to control the total of these combined connections that will occur to many different databases (incidentally I can only find out the names of individual db's dynamically as they change day to day). Will connection pooling take care of this for me, are am I looking at this from the wrong perspective? I have no access to the configuration of the mssql server. Links to tutorials or working examples of your suggested solution are most welcome! Thanks, Caroline

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  • SQL Server: query database user roles for all databases in server

    - by atricapilla
    I would like to make a query for database user roles for all databases in my sql server instance. I modified a query from sp_helpuser: select u.name ,case when (r.principal_id is null) then 'public' else r.name end ,l.default_database_name ,u.default_schema_name ,u.principal_id from sys.database_principals u left join (sys.database_role_members m join sys.database_principals r on m.role_principal_id = r.principal_id) on m.member_principal_id = u.principal_id left join sys.server_principals l on u.sid = l.sid where u.type <> 'R' How can I modify this to query from all databases? What is the link between sys.databases and sys.database_principals?

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  • Why is autorelease especially dangerous/expensive for iPhone applications?

    - by e.James
    I'm looking for a primary source (or a really good explanation) to back up the claim that the use of autorelease is dangerous or overly expensive when writing software for the iPhone. Several developers make this claim, and I have even heard that Apple does not recommend it, but I have not been able to turn up any concrete sources to back it up. SO references: autorelease-iphone Why does this create a memory leak (iPhone)? Note: I can see, from a conceptual point of view, that autorelease is slightly more expensive than a simple call to release, but I don't think that small penalty is enough to make Apple recommend against it. What's the real story?

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  • .NET Data Provider for SqlServer

    - by DMcKenna
    Has anybody managed to get the ".NET Data Provider for SqlServer" to actually work within perfmon.exe. I have a .NET app that uses nhibernate to interact with sql server 2005 db. All I want to do is to view the NumberOfActiveConnectionPools, NumberOfActiveConnections and the NumberOfFreeConnections within perfmon.exe Can somebody explain to me how exactly I get this to work? Regards, David

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  • Unicorn: Which number of worker processes to use?

    - by blackbird07
    I am running a Ruby on Rails app on a virtual Linux server that is capped at 1GB RAM. Currently, I am constantly hitting the limit and would like to optimize memory utilization. One option I am looking at is reducing the number of unicorn workers. So what is the best way to determine the number of unicorn workers to use? The current setting is 10 workers, but the maximum number of requests per second I have seen on Google Analytics Real-Time is 3 (only scored once at a peak time; in 99% of the time not going above 1 request per second). So is it a save assumption that I can - for now - go with 4 workers, leaving room for unexpected amounts of requests? What are the metrics I should have a look at for determining the number of workers and what are the tools I can use for that on my Ubuntu machine?

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  • Python: how to run several scripts (or functions) at the same time under windows 7 multicore processor 64bit

    - by Gianni
    sorry for this question because there are several examples in Stackoverflow. I am writing in order to clarify some of my doubts because I am quite new in Python language. i wrote a function: def clipmyfile(inFile,poly,outFile): ... # doing something with inFile and poly and return outFile Normally I do this: clipmyfile(inFile="File1.txt",poly="poly1.shp",outFile="res1.txt") clipmyfile(inFile="File2.txt",poly="poly2.shp",outFile="res2.txt") clipmyfile(inFile="File3.txt",poly="poly3.shp",outFile="res3.txt") ...... clipmyfile(inFile="File21.txt",poly="poly21.shp",outFile="res21.txt") I had read in this example Run several python programs at the same time and i can use (but probably i wrong) from multiprocessing import Pool p = Pool(21) # like in your example, running 21 separate processes to run the function in the same time and speed my analysis I am really honest to say that I didn't understand the next step. Thanks in advance for help and suggestion Gianni

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  • Should the code being tested compile to a DLL or an executable file?

    - by uriDium
    I have a solution with two projects. One for project for the production code and another project for the unit tests. I did this as per the suggestions I got here from SO. I noticed that in the Debug Folder that it includes the production code in executable form. I used NUnit to run the tests after removing the executable and they all fail trying to find the executable. So it definitely is trying to find it. I then did a quick read to find out which is better, a DLL or an executable. It seems that an DLL is much faster as they share memory space where communication between executables is slower. Unforunately our production code needs to be an exectuable. So the unit tests will be slightly slower. I am not too worried about that. But the project does rely on code written in another library which is also in executable format at the moment. Should the projects that expose some sort of SDK rather be compiled to an DLL and then the projects that use the SDK be compiled to executable?

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  • Fast read of certain bytes of multiple files in C/C++

    - by Alejandro Cámara
    I've been searching in the web about this question and although there are many similar questions about read/write in C/C++, I haven't found about this specific task. I want to be able to read from multiple files (256x256 files) only sizeof(double) bytes located in a certain position of each file. Right now my solution is, for each file: Open the file (read, binary mode): fstream fTest("current_file", ios_base::out | ios_base::binary); Seek the position I want to read: fTest.seekg(position*sizeof(test_value), ios_base::beg); Read the bytes: fTest.read((char *) &(output[i][j]), sizeof(test_value)); And close the file: fTest.close(); This takes about 350 ms to run inside a for{ for {} } structure with 256x256 iterations (one for each file). Q: Do you think there is a better way to implement this operation? How would you do it?

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