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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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  • Find the highest number of occurences in a column in SQL

    - by Ronnie
    Given this table: Order custName description to_char(price) A desa $14 B desb $14 C desc $21 D desd $65 E dese $21 F desf $78 G desg $14 H desh $21 I am trying to display the whole row where prices have the highest occurances, in this case $14 and $21 I believe there needs to be a subquery. So i started out with this: select max(count(price)) from orders group by price which gives me 3. after some time i didn't think that was helpful. i believe i needed the value 14 and 21 rather the the count so i can put that in the where clause. but I'm stuck how to display that. any help?

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  • Is it possible to combine these 3 mySQL queries?

    - by Greenie
    I know the $downloadfile - and I want the $user_id. By trial and error I found that this does what I want. But it's 3 separate queries and 3 while loops. I have a feeling there is a better way. And yes, I only have a very little idea about what I'm doing :) $result = pod_query("SELECT ID FROM wp_posts WHERE guid LIKE '%/$downloadfile'"); while ($row = mysql_fetch_assoc($result)) { $attachment = $row['ID']; } $result = pod_query("SELECT pod_id FROM wp_pods_rel WHERE tbl_row_id = '$attachment'"); while ($row = mysql_fetch_assoc($result)) { $pod_id = $row['pod_id']; } $result = pod_query("SELECT tbl_row_id FROM wp_pods_rel WHERE tbl_row_id = '$pod_id' AND field_id = '28'"); while ($row = mysql_fetch_assoc($result)) { $user_id = $row['pod_id']; }

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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 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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  • table lock while creating table using select

    - by shal
    Using mysql version 5.0.18 I am creating a table TT, Client 1 set autocommit = false; start transaction Create table TT select * from PT; PT has tow columns pk bigint not null,name varchar(20) Client 2 set autocommit = false start transaction insert into PT values(123,'text'); While inserting a row in PT , it is waiting for the table Client 1 to commit. I am unable to insert the row. why? Is it possible to insert the row without waiting for Client 1 to commit.

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  • fastest way to crawl recursive ntfs directories in C++

    - by Peter Parker
    I have written a small crawler to scan and resort directory structures. It based on dirent(which is a small wrapper around FindNextFileA) In my first benchmarks it is surprisingy slow: around 123473ms for 4500 files(thinkpad t60p local samsung 320 GB 2.5" HD). 121481 files found in 123473 milliseconds Is this speed normal? This is my code: int testPrintDir(std::string strDir, std::string strPattern="*", bool recurse=true){ struct dirent *ent; DIR *dir; dir = opendir (strDir.c_str()); int retVal = 0; if (dir != NULL) { while ((ent = readdir (dir)) != NULL) { if (strcmp(ent->d_name, ".") !=0 && strcmp(ent->d_name, "..") !=0){ std::string strFullName = strDir +"\\"+std::string(ent->d_name); std::string strType = "N/A"; bool isDir = (ent->data.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) !=0; strType = (isDir)?"DIR":"FILE"; if ((!isDir)){ //printf ("%s <%s>\n", strFullName.c_str(),strType.c_str());//ent->d_name); retVal++; } if (isDir && recurse){ retVal += testPrintDir(strFullName, strPattern, recurse); } } } closedir (dir); return retVal; } else { /* could not open directory */ perror ("DIR NOT FOUND!"); return -1; } }

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  • How to decide on what hardware to deploy web application

    - by Yuval A
    Suppose you have a web application, no specific stack (Java/.NET/LAMP/Django/Rails, all good). How would you decide on which hardware to deploy it? What rules of thumb exist when determining how many machines you need? How would you formulate parameters such as concurrent users, simultaneous connections and DB read/write ratio to a decision on how much, and which, hardware you need? Any resources on this issue would be very helpful...

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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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  • How can one fetch partial objects in NHibernate?

    - by mark
    Dear ladies and sirs. I have an object O with 2 fields - A and B. How can I fetch O from the database so that only the field A is fetched? Of course, my real application has objects with many more fields, but two fields are enough to understand the principal. I am using NHibernate 2.1. Thanks.

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  • Zend Framework table Relationships

    - by Uffo
    I have a table with over 4 million rows, I want to split this table in more tables, i.e one table with 50k rows. I also need to perform a search on these tables, whats the best way to do it? with JOIN, or? do you have some better ideas? Best Regards,

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  • How to shift pixels of a pixmap efficient in Qt4

    - by stanleyxu2005
    Hello, I have implemented a marquee text widget using Qt4. I painted the text content onto a pixmap first. And then paint a portion of this pixmap onto a paint device by calling painter.drawTiledPixmap(offsetX, offsetY, myPixmap) My Imagination is that, Qt will fill the whole marquee text rectangle with the content from myPixmap. Is there a ever faster way, to shift all existing content to left by 1px and than fill the newly exposed 1px wide and N-px high area with the content from myPixmap?

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  • What is the most efficient way to store a mapping "key -> event stream"?

    - by jkff
    Suppose there are ~10,000's of keys, where each key corresponds to a stream of events. I'd like to support the following operations: push(key, timestamp, event) - pushes event to the event queue for key, marked with the given timestamp. It is guaranteed that event timestamps for a particular key are pushed in sorted or almost sorted order. tail(key, timestamp) - get all events for key since the given timestamp. Usually the timestamp requests for a given key are almost monotonically increasing, almost synchronously with pushes for the same key. This stuff has to be persistent (although it is not absolutely necessary to persist pushes immediately and to keep tails with pushes strictly in sync), so I'm going to use some kind of database. What is the optimal kind of database structure for this task? Would it be better to use a relational database, a key-value storage, or something else?

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  • Pros and Cons of using SqlCommand Prepare in C#?

    - by MadBoy
    When i was reading books to learn C# (might be some old Visual Studio 2005 books) I've encountered advice to always use SqlCommand.Prepare everytime I execute SQL call (whether its' a SELECT/UPDATE or INSERT on SQL SERVER 2005/2008) and I pass parameters to it. But is it really so? Should it be done every time? Or just sometimes? Does it matter whether it's one parameter being passed or five or twenty? What boost should it give if any? Would it be noticeable at all (I've been using SqlCommand.Prepare here and skipped it there and never had any problems or noticeable differences). For the sake of the question this is my usual code that I use, but this is more of a general question. public static decimal pobierzBenchmarkKolejny(string varPortfelID, DateTime data, decimal varBenchmarkPoprzedni, decimal varStopaOdniesienia) { const string preparedCommand = @"SELECT [dbo].[ufn_BenchmarkKolejny](@varPortfelID, @data, @varBenchmarkPoprzedni, @varStopaOdniesienia) AS 'Benchmark'"; using (var varConnection = Locale.sqlConnectOneTime(Locale.sqlDataConnectionDetailsDZP)) //if (varConnection != null) { using (var sqlQuery = new SqlCommand(preparedCommand, varConnection)) { sqlQuery.Prepare(); sqlQuery.Parameters.AddWithValue("@varPortfelID", varPortfelID); sqlQuery.Parameters.AddWithValue("@varStopaOdniesienia", varStopaOdniesienia); sqlQuery.Parameters.AddWithValue("@data", data); sqlQuery.Parameters.AddWithValue("@varBenchmarkPoprzedni", varBenchmarkPoprzedni); using (var sqlQueryResult = sqlQuery.ExecuteReader()) if (sqlQueryResult != null) { while (sqlQueryResult.Read()) { //sqlQueryResult["Benchmark"]; } } } }

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  • WCF high instance count: anyone knows negative sideffects?

    - by Alex
    Hi there! Did anyone experience or know of negative side effects from having a high service instance count like 60k? Aside from the memory consumption of course. I am planning to increase the threshold for the maximum allowed instance count in our production environments. I am basically sick of severe production incidents just because "something" forgot to close a proxy properly. I plan to go to something like 60k instances which will allow the service to survive using default session timeouts at a call rate average for our clients. Thanks, Alex

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  • Is opening too many datacontexts bad?

    - by ryudice
    I've been checking my application with linq 2 sql profiler, and I noticed that it opens a lot of datacontexts, most of them are opened by the linq datasource I used, since my repositories use only the instance stored in Request.Items, is it bad to open too many datacontext? and how can I make my linqdatasource to use the datacontext that I store in Request.Items for the duration of the request? thanks for any help!

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  • Why the difference in speed?

    - by AngryHacker
    Consider this code: function Foo(ds as OtherDLL.BaseObj) dim lngRowIndex as long dim lngColIndex as long for lngRowIndex = 1 to ubound(ds.Data, 2) for lngColIndex = 1 to ds.Columns.Count Debug.Print ds.Data(lngRowIndex, lngColIndex) next next end function OK, a little context. Parameter ds is of type OtherDLL.BaseObj which is defined in a referenced ActiveX DLL. ds.Data is a variant 2-dimensional array (one dimension carries the data, the other one carries the column index. ds.Columns is a Collection of columns in 'ds.Data`. Assuming there are at least 400 rows of data and 25 columns, this code takes about 15 seconds to run on my machine. Kind of unbelievable. However if I copy the variant array to a local variable, so: function Foo(ds as OtherDLL.BaseObj) dim lngRowIndex as long dim lngColIndex as long dim v as variant v = ds.Data for lngRowIndex = 1 to ubound(v, 2) for lngColIndex = 1 to ds.Columns.Count Debug.Print v(lngRowIndex, lngColIndex) next next end function the entire thing processes in barely any noticeable time (basically close to 0). Why?

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  • php and mysql listing databases and looping through results

    - by Jacksta
    Beginner help needed :) I am doign an example form a php book which lists tables in databases. I am getting an error on line 36: $db_list .= "$table_list"; <?php //connect to database $connection = mysql_connect("localhost", "admin_cantsayno", "cantsayno") or die(mysql_error()); //list databases $dbs = @mysql_list_dbs($connection) or die(mysql_error()); //start first bullet list $db_list = "<ul>"; $db_num = 0; //loop through results of functions while ($db_num < mysql_num_rows($dbs)) { //get database names and make each a list point $db_names[$db_num] = mysql_tablename($dbs, $db_num); $db_list .= "<li>$db_names[$db_num]"; //get table names and make another list $tables = @mysql_list_tables($db_names[$db_num]) or die(mysql_error()); $table_list = "<ul>"; $table_num = 0; //loop through results of function while ($table_num < mysql_num_rows($tables)){ //get table names and make each bullet point $table_names[$table_num] = mysql_tablename($tables, $table_num); $table_list .= "<li>$table_names[$table_num]"; $table_num++; } //close inner bullet list and increment number to continue $table_list .= "</ul>" $db_list .= "$table_list"; $db_num++; } //close outer bullet list $db_list .= "</ul>"; ?> <html> <head> <title>MySQL Tables</title> </head> <body> <p><strong>Data bases and tables on local host</strong></p> <? echo "$db_list"; ?> </body>

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  • WebCenter Content Web Search Performance: Do you really need that folder path info?

    - by Nicolas Montoya
    End-users want content at their fingertips at the speed of thought if possible. When running search operations in the WebCenter Conter Web Interface every second or fraction of a second improvement does matter. When doing some trace analysis on the systemdatabase tracing on a customer environment, we came across some SQL queries that were unnecessarily being triggered! These were related to determining the folder path for every entry part of the search result set. However, this folder path was not even being used as part of the displayed information in the user interface.Why was the folder path information being collected when it was not even displayed in the UI? We found that the configuration parameter 'FolderPathInSearchResults' was set to 'true' under Administration > Admin Server > General Configuration > Additional Configuration Variables as shown below:When executing a quicksearch by keyword we were getting 100 out of 2280 entries in the first page of the result set.When thera 'FolderPathInSearchResults' configuration parameter is set to 'true', the following queries appear in the systemdatabase tracing:100 executions for a query on the FolderFiles table for each of the documents displayed in the first page:>systemdatabase/6       12.13 11:17:48.188      IdcServer-199   1.45 ms. SELECT * FROM FolderFiles WHERE dDocName='SLC02VGVUSORAC140641' AND fLinkRank=0[Executed. Returned row(s): true]382 executions for a query of the folders tables - most of the documents that match the keyword criteria are at a folder depth level of three or four:>systemdatabase/6       12.13 11:17:48.114      IdcServer-199   2.57 ms. SELECT FolderFolders.*,FolderMetaDefaults.* FROM FolderFolders,FolderMetaDefaults WHERE FolderFolders.fFolderGUID=FolderMetaDefaults.fFolderGUID(+) AND((FolderFolders.fFolderGUID = '1EB8E527E19B09ED3FE82EE310AEA13A' ) )[Executed.Returned row(s): true]By setting this 'FolderPathInSearchResults' configuration parameter to 'false', the above queries were no longer reported in the Server Output System Audit Information.Now, let's consider a practical scenario:Search result set page = 100Average folder depth der document in the search result set: 5The number of folder path related queries will be: 100 + 5*500 = 600If each query takes slightly over 3 ms. You would have 2000 ms (2 seconds) spent in server time to get this information.The overall performance impact goes beyond seerver time execution, as this information needs to travel from the server to the browser. If the documents are further nested into the folder hierarchy, additional hundreds of queries may be executed. If folder path is not being displayed in the end-user interface profile, your system may be better of with the 'FolderPathInSearchResults' configuration parameter disabled.

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  • Does the order of columns matter in a group by clause?

    - by Jeff Meatball Yang
    If I have two columns, one with very high cardinality and one with very low cardinality (unique # of values), does it matter in which order I group by? Here's an example: select dimensionName, dimensionCategory, sum(someFact) from SomeFact f join SomeDim d on f.dimensionKey = d.dimensionKey group by d.dimensionName, -- large number of unique values d.dimensionCategory -- small number of unique values Are there situations where it matters?

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