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• Application built using VS2010 does not work in VS-Express2008 - C

  - by Jamie Keeling

  Hello, I have wrote an application that consists of two projects in a solution, each project contains only 1 .c source file. I was using Visual Studio 2010 Ultimate but due to the University only supporting 2008 I decided to create a blank solution and copy the source files into the new one. After creating a new solution in VS2008 express, creating two projects and re-creating and adding the source files to the projects I ran the application. For some reason only one part of the application does not work, I use CreateProcess() to execute "Project1.exe" from Project 2. This works fine under vs2010 but for some reason it's not working under VS2008 express, GetLastError() is showing an Error 2: File Not Found. This is an image showing the same code in both IDE's: I'm not using anything special and I've made sure that both solutions/projects are using .Net 3.5. I can't work out why it would work for one IDE and not the other. Any suggestions? Thanks!

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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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• mysql subquery strangely slow

  - by aviv

  I have a query to select from another sub-query select. While the two queries look almost the same the second query (in this sample) runs much slower: SELECT user.id ,user.first_name -- user.* FROM user WHERE user.id IN (SELECT ref_id FROM education WHERE ref_type='user' AND education.institute_id='58' AND education.institute_type='1' ); This query takes 1.2s Explain on this query results: id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY user index first_name 152 141192 Using where; Using index 2 DEPENDENT SUBQUERY education index_subquery ref_type,ref_id,institute_id,institute_type,ref_type_2 ref_id 4 func 1 Using where The second query: SELECT -- user.id -- user.first_name user.* FROM user WHERE user.id IN (SELECT ref_id FROM education WHERE ref_type='user' AND education.institute_id='58' AND education.institute_type='1' ); Takes 45sec to run, with explain: id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY user ALL 141192 Using where 2 DEPENDENT SUBQUERY education index_subquery ref_type,ref_id,institute_id,institute_type,ref_type_2 ref_id 4 func 1 Using where Why is it slower if i query only by index fields? Why both queries scans the full length of the user table? Any ideas how to improve? Thanks.

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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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• 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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• 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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• 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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• Efficiency of iteration: NSArray vs C array of pointers?

  - by morgancodes

  I'm working at the audio buffer level, mixing audio signals created by a colleciton of objects. Since I'm looping through these objects at 44.1khz, efficiency is crucial. Is there any difference in the efficiency of iterating over an NSArray vs a C array of pointers? How about NSMutableArray?

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• PostgreSQL: Why does this simple query not use the index?

  - by David

  I have a table t with a column c, which is an int and has a btree index on it. Why does the following query not utilize this index? explain select c from t group by c; The result I get is: HashAggregate (cost=1005817.55..1005817.71 rows=16 width=4) -> Seq Scan on t (cost=0.00..946059.84 rows=23903084 width=4) My understanding of indexes is limited, but I thought such queries were the purpose of indexes.

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• Get Excel.Application object from Process or hwnd in .NET

  - by Abiel

  In C# I am trying to get an instance of an Excel.Application object from a Process object. This seems like it should be really simple yet I cannot figure it out and cannot find an example. To repeat, I have a System.Diagnostics.Process object that I know refers to a running Excel instance. I now need to recover a Microsoft.Office.Interop.Excel.Application object that refers to the process so that I can go about manipulating the Excel application from C#. In case it makes it any simpler, I also have the HWND id and window text associated with the active Excel window. Thanks.

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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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• MySQL Locking Up

  - by Ian

  I've got a innodb table that gets a lot of reads and almost no writes (like, 1 write for every 400,000 reads approx). I'm running into a pretty big problem though when I do INSERT into the table. MySQL completely locks up. It uses 100% cpu, and every single other table (in other databases even) have their statuses set to "Locked" until the INSERT is done. This is a big problem because MySQL stays locked up for up to 4 minutes. I'm using version 5.1.47 (rpm from mysql.com). Any ideas?

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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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• bad_application error starting erlang gen_server application

  - by user313475

  I have written a simple erlang app using gen_server. When starting it with application:start(myapp), I get the following tuple... {error,{bad_application,{application,myapp ... (rest of my application config). There are no other error or warning messages. I have also tried to google examples of how to configure gen_server and also the error itself. I am surprised at how little information there is out there. I could start trying to debug OTP?? Any pointers would be appreciated.

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• Scalability of Ruby on Rails versus PHP

  - by Daniel

  Can anyone comment on which is more scalable between RoR and PHP? I have heard that RoR is less scalable than PHP since RoR has a little more overhead with its MVC framework while PHP is more low level and lighter. This is a bit vague - can anyone explain better?

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• Optimizing a shared buffer in a producer/consumer multithreaded environment

  - by Etan

  I have some project where I have a single producer thread which writes events into a buffer, and an additional single consumer thread which takes events from the buffer. My goal is to optimize this thing for a single machine to achieve maximum throughput. Currently, I am using some simple lock-free ring buffer (lock-free is possible since I have only one consumer and one producer thread and therefore the pointers are only updated by a single thread). #define BUF_SIZE 32768 struct buf_t { volatile int writepos; volatile void * buffer[BUF_SIZE]; volatile int readpos;) }; void produce (buf_t *b, void * e) { int next = (b->writepos+1) % BUF_SIZE; while (b->readpos == next); // queue is full. wait b->buffer[b->writepos] = e; b->writepos = next; } void * consume (buf_t *b) { while (b->readpos == b->writepos); // nothing to consume. wait int next = (b->readpos+1) % BUF_SIZE; void * res = b->buffer[b->readpos]; b->readpos = next; return res; } buf_t *alloc () { buf_t *b = (buf_t *)malloc(sizeof(buf_t)); b->writepos = 0; b->readpos = 0; return b; } However, this implementation is not yet fast enough and should be optimized further. I've tried with different BUF_SIZE values and got some speed-up. Additionaly, I've moved writepos before the buffer and readpos after the buffer to ensure that both variables are on different cache lines which resulted also in some speed. What I need is a speedup of about 400 %. Do you have any ideas how I could achieve this using things like padding etc?

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• Avoid having a huge collection of ids by calling a DAO.getAll()

  - by Michael Bavin

  Instead of returning a List<Long> of ids when calling PersonDao.getAll() we wanted not to have an entire collection of ids in memory. Seems like returning a org.springframework.jdbc.support.rowset.SqlRowSet and iterate over this rowset would not hold every object in memory. The only problem here is i cannot cast this row to my entity. Is there a better way for this?

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• ~1 second TcpListener Pending()/AcceptTcpClient() lag

  - by cpf

  Probably just watch this video: http://screencast.com/t/OWE1OWVkO As you see, the delay between a connection being initiated (via telnet or firefox) and my program first getting word of it. Here's the code that waits for the connection public IDLServer(System.Net.IPAddress addr,int port) { Listener = new TcpListener(addr, port); Listener.Server.NoDelay = true;//I added this just for testing, it has no impact Listener.Start(); ConnectionThread = new Thread(ConnectionListener); ConnectionThread.Start(); } private void ConnectionListener() { while (Running) { while (Listener.Pending() == false) { System.Threading.Thread.Sleep(1); }//this is the part with the lag Console.WriteLine("Client available");//from this point on everything runs perfectly fast TcpClient cl = Listener.AcceptTcpClient(); Thread proct = new Thread(new ParameterizedThreadStart(InstanceHandler)); proct.Start(cl); } } (I was having some trouble getting the code into a code block) I've tried a couple different things, could it be I'm using TcpClient/Listener instead of a raw Socket object? It's not a mandatory TCP overhead I know, and I've tried running everything in the same thread, etc.

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• Implementing a 'Send Feedback' feature in a Java desktop application

  - by William

  I would like to implement a 'Send Feedback' option in a Java desktop application. One which will pop up a box for the user to enter a comment, then send it to us along with a screenshot of the application window. How would be the best way to communicate the data to us? Two obvious solutions spring to mind: Email - I'm thinking that the application would connect to an SMTP server set-up by us, with the username/password somehow hidden in the code. SMTP over SSL for security (not of the data being sent, but of the SMTP username/password). Web service - pretty self explanatory. Which of these would be best, or is there a better alternative?

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• Extracting a Rails application into a plugin or engine

  - by Globalkeith

  I have a Rails 2.3 application which I would like to extract into a plugin, or engine. The application has user authentication, and basic cms capabilities supported by ancestry plugin. I want to extract the logic for the application into a plugin/engine so that I can use this code for future projects, with a different "skin" or "theme" if required. I'm not entirely sure I actually understand the difference between plugin and engine concepts, so that would be a good first point. What is the best approach, are there any good starting points, links, explanations, examples that I should follow. Also, with the release of R3 to consider, is there anything that I should be aware of for that, with regards to plugins etc. I am going to start off by watching Ryan's http://railscasts.com/episodes/149-rails-engines but obviously thats over a year old now, so one of the challenges I'm faced with is finding the most up to date and relevant information on this subject. All tips and help gratefully received.

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• Is there a way to rewrite the SQL query efficiently

  - by user320587

  hi, I have two tables with following definition TableA TableB ID1 ID2 ID3 Value1 Value ID1 Value1 C1 P1 S1 S1 C1 P1 S2 S2 C1 P1 S3 S3 C1 P1 S5 S4 S5 The values are just examples in the table. TableA has a clustered primary key ID1, ID2 & ID3 and TableB has p.k. ID1 I need to create a table that has the missing records in TableA based on TableB The select query I am trying to create should give the following output C1 P1 S4 To do this, I have the following SQL query SELECT DISTINCT TableA.ID1, TableA.ID2, TableB.ID1 FROM TableA a, TableB b WHERE TableB.ID1 NOT IN ( SELECT DISTINCT [ID3] FROM TableA aa WHERE a.ID1 == aa.ID1 AND a.ID2 == aa.ID2 ) Though this query works, it performs poorly and my final TableA may have upto 1M records. is there a way to rewrite this more efficiently. Thanks for any help, Javid

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• any faster alternative??

  - by kaushik

  I have to read a file from a particular line number and i know the line number say "n": i have been thinking of two choice: 1)for i in range(n) fname.readline() k=readline() print k 2)i=0 for line in fname: dictionary[i]=line i=i+1 but i want to know faster alternative as i might have to perform this on different files 20000 times. is there is any other better alternatives?? thanking u

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• Know of any Java garbage collection log analysis tools?

  - by braveterry

  I'm looking for a tool or a script that will take the console log from my web app, parse out the garbage collection information and display it in a meaningful way. I'm starting up on a Sun Java 1.4.2 JVM with the following flags: -verbose:gc -XX:+PrintGCTimeStamps -XX:+PrintGCDetails The log output looks like this: 54.736: [Full GC 54.737: [Tenured: 172798K->18092K(174784K), 2.3792658 secs] 257598K->18092K(259584K), [Perm : 20476K->20476K(20480K)], 2.4715398 secs] Making sense of a few hundred of these kinds of log entries would be much easier if I had a tool that would visually graph garbage collection trends.

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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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• Visual Studio detaches from application as soon as debugging starts

  - by rwmnau

  I have a web application that I've always been able to run in Visual Studio and it debugs just fine (breakpoints work, I can pause execution, etc). Recently, the behavior changed suddenly, and a few things happen: I start debugging, it lauches IE and loads the application, but after a few seconds (sometimes the page hasn't even displayed yet), Visual Studio acts as if debugging has stopped - I'm able to edit code in VS again, and the "Play" button on the toolbar is enabled. The application continues to run in the IE window just spawned, but I'm not attached to it During this few seconds that VS is "debugging", because it detaches, my breakpoints show as hollow - as if I'm set to "Release" mode and they won't be hit. In fact, I have a breakpoint set in Page_Load, and it skips right by. I've checked, and I'm set to debug mode, though the compile mode dropdown is missing from my toolbar (I checked in the build properties to ensure I was in debug mode). Can anybody shed some light here?

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