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• Multiple PictureBoxs' C#

  - by Austin Smith

  I'm having a hard time figuring this out. I know pictureBox only lets you display one image a time. I'm trying to create a pictureBox for each image in my collection. For instance if I have ten images in my List, then the method should create ten pictureBox for those respective images so each one is displayes in a pictureBox. I'm not sure which would be better a for loop or a foreach loop instead. every time the loop increments both the varaiables XCoordinate and YCoordinate which are the location of the PictireBox shoulld increase so that the PictureBox won't overlap one another in the Form. The reason for the method is that the number of images in the collection can change everytime the application will run. That's why I'm not creating them manually. So after its done all the pictures in the list should appear in a picture.Box. The box should be all the same size the only difference is the location on the form and the images inside them. Please any help and I will be grateful

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• directory traversal in Java using different regular and enhanced for loops

  - by user3245621

  I have this code to print out all directories and files. I tried to use recursive method call in for loop. With enhanced for loop, the code prints out all the directories and files correctly. But with regular for loop, the code does not work. I am puzzled by the difference between regular and enhanced for loops. public class FileCopy { private File[] childFiles = null; public static void main(String[] args) { FileCopy fileCopy = new FileCopy(); File srcFile = new File("c:\\temp"); fileCopy.copyTree(srcFile); } public void copyTree(File file){ if(file.isDirectory()){ System.out.println(file + " is a directory. "); childFiles = file.listFiles(); /*for(int j=0; j<childFiles.length; j++){ copyTree(childFiles[j]); } This part is not working*/ for(File a: childFiles){ copyTree(a); } return; } else{ System.out.println(file + " is a file. "); return; } } }

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• table in drupal with edit link

  - by user544079

  I have a table created in drupal with the edit link pointing to the input form. But the problem is, it only displays the last row values in the $email and $comment variables. Can anyone suggest how to modify the table display to have the edit link to the corresponding records? function _MYMODULE_sql_to_table($sql) { $html = ""; // execute sql $resource = db_query($sql); // fetch database results in an array $results = array(); while ($row = db_fetch_array($resource)) { $results[] = $row; $email = $row['email']; $comment = $row['comment']; drupal_set_message('Email: '.$email. ' comment: '.$comment); } // ensure results exist if (!count($results)) { $html .= "Sorry, no results could be found."; return $html; } // create an array to contain all table rows $rows = array(); // get a list of column headers $columnNames = array_keys($results[0]); // loop through results and create table rows foreach ($results as $key => $data) { // create row data $row = array( 'edit' => l(t('Edit'),"admin/content/test/$email/$comment/ContactUs", $options=array()),); // loop through column names foreach ($columnNames as $c) { $row[] = array( 'data' => $data[$c], 'class' => strtolower(str_replace(' ', '-', $c)), ); } // add row to rows array $rows[] = $row; } // loop through column names and create headers $header = array(); foreach ($columnNames as $c) { $header[] = array( 'data' = $c, 'class' = strtolower(str_replace(' ', '-', $c)), ); } // generate table html $html .= theme('table', $header, $rows); return $html; } // then you can call it in your code... function _MYMODULE_some_page_callback() { $html = ""; $sql = "select * from {contactus}"; $html .= _MYMODULE_sql_to_table($sql); return $html; }

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• Setting default values for object properties in AS3

  - by Paul T

  I'm an actionscript newbie so please bear with me. Below is a function, and I am curious how to set default property values for objects that are being created in a loop. In the example below, these propeties are the same for each object created in the loop: titleTextField.selectable, titleTextField.wordWrap, titleTextField.x If you pull these properties out of the loop, they are null because the TextField objects have not been created, but it seems silly to have to set them each time. What is the correct way to do this. Thanks! var titleTextFormat:TextFormat = new TextFormat(); titleTextFormat.size = 10; titleTextFormat.font = "Arial"; titleTextFormat.color = 0xfff200; for (var i=0; i<arrThumbPicList.length; i++) { var yPos = 55 * i var titleTextField:TextField = new TextField(); titleTextField.selectable = false; titleTextField.wordWrap = true; titleTextField.text = arrThumbTitles[i]; titleTextField.x = 106; titleTextField.y = 331 + yPos; container.addChild(titleTextField); titleTextField.setTextFormat(titleTextFormat); }

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• How do I reset my pointer to a specific array location?

  - by ohtanya

  I am a brand new programming student, so please forgive my ignorance. My assignment states: Write a program that declares an array of 10 integers. Write a loop that accepts 10 values from the keyboard and write another loop that displays the 10 values. Do not use any subscripts within the two loops; use pointers only. Here is my code: #include "stdafx.h" #include <iostream> using namespace std; int main() { const int NUM = 10; int values[NUM]; int *p = &values[0]; int x; for(x = 0; x < NUM; ++x, ++p) { cout << "Enter a value: "; cin >> *p; } for(x = 0; x < NUM; ++x, ++p) { cout << *p << " "; } return 0; } I think I know where my problem is. After my first loop, my pointer is at values[10], but I need to get it back to values[0] to display them. How can I do that?

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• Differentiate Between UITableView Editing States?

  - by Josh Kahane

  I have been looking at trying to differentiate between editing states in my UITableView. I need to call a method only when in editing mode after tapping the edit button, so when you get your cell slide in and you see the little circular delete icons but NOT when the user swipes to delete. Is there anyway I can differentiate between the two? Thanks. EDIT: Solution thanks to Rodrigo Both each cell and the entire tableview has an 'editing' BOOL value, so I loop through all the cells and if more than one of them is editing then we know the whole table is (the user tapped the edit button), however if only one is editing then we know that the user has swiped a cell, editing that individual one, this lets me deal with each editing state individually! - (void)setEditing:(BOOL)editing animated:(BOOL)animated { [super setEditing:editing animated:animated]; int i = 0; //When editing loop through cells and hide status image so it doesn't block delete controls. Fade back in when done editing. for (customGuestCell *cell in self.tableView.visibleCells) { if (cell.isEditing) { i += 1; } } if (i > 1) { for (customGuestCell *cell in self.tableView.visibleCells) { if (editing) { // loop through the visible cells and animate their imageViews [UIView beginAnimations:nil context:nil]; [UIView setAnimationDuration:0.4]; cell.statusImg.alpha = 0; [UIView commitAnimations]; } } } else if (!editing) { for (customGuestCell *cell in self.tableView.visibleCells) { [UIView beginAnimations:nil context:nil]; [UIView setAnimationDuration:0.4]; cell.statusImg.alpha = 1.0; [UIView commitAnimations]; } } }

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• Runtime of optimized Primehunter

  - by Setton

  Ok so I need some serious runtime help here! This method should take in an int value, check its primality, and return true if the number is indeed a prime. I understand why the loop only needs to go up to i squared, I understand that the worst case scenario is the case in which either the number is prime (or a multiple of a prime). But I don't understand how to quantify the actual runtime. I have done the loop myself by hand to try to understand the pattern or correlation of the number (n) and how many loops occur, but I literally feel like I keep falling into the same trap every time. I need a new way of thinking about this! I have a hint: "Think about the SIZE of the integer" which makes me want to quantify the literal number of integers in a number in relation to how many iterations it does in the for loop (floor log(n)) +1). BUT IT'S NOT WORKIIIING?! I KNOW it isn't square root n, obviously. I'm asking for Big O notation. public class PrimeHunter { public static boolean isPrime(int n) { boolean answer = (n > 1) ? true : false; //runtime = linear runtime for (int i = 2; i * i <= n; i++) //runtime = ????? { if (n % i == 0) //doesn't occur if it is a prime { answer = false; break; } } return answer; //runtime = linear runtime } }

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• Setting Timeouts: SQL Server 2008/IIS 7.5

  - by Julie

  We have recently migrated from a Win 2003/SQL Server 2000 system to Win 2008 64 bit R2, SQL Server 2008 R2. Our websites are in classic asp, and this can't be changed to another scripting language at this time. On the old server, if I got stuck in some kind of endless loop, the page would throw an error. On the new server, I have a page that has some sort of looping problem, that even though the SQL SP is called only once (and runs fine run as a query on the server) it pegs SQL server and therefore locks all of our websites. I'll get my code figured out, no biggie. But I need to make sure the server times out when this happens. (The page I'm working on runs fine with certain instances of the query, and locks with others using a different query variable. I can't have something like that sneak up on me on a page I haven't touched for three years.) I can't figure out how an SP that runs once on the server, from an ASP page, is tying up SQL server this way. It's obviously some sort of a timeout issue, but I can't figure out where/which timeout values to change. I actually have to remote desktop to the server and kill the process in SQL server. I'm afraid I'm a generalist, and server management is not my thing, even though it's my responsibility, so I am almost certain to have questions about any answer that I receive. How can I track this down? What settings do I need to change? More info: It's not SQL Server On our test site, I created an ASP file that just did an endless loop (do while 1=1) and had the same problem - the other websites wouldn't load - without SQL server being involved. So I think the reason the process was hanging is that the page wasn't timing out as it should, and so the connection to SQL was never closed. Killing the process in SQL server would reset the page somehow. For my intentional endless loop, I had to refresh the app pool to get rid of it. This points more to either IIS or the ASP settings. The ASP timeouts are set to whatever the default were when the server was first loaded. I still can't figure out why one file is locking up all websites, though. Again, that didn't happen on the old server.

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• Partimage and autocheck problem when restoring Windows XP from image

  - by Xolstice

  I'm trying to create an image of Windows XP and clone it to several partitions on the same hard drive using Partimage. I seem to be running into a problem when I restore the image onto another partition - when I boot into the OS from the partition I just restored, it brings up this message during the boot sequence: autochk program not found - skipping autocheck, and then after this, the OS reboots the PC and the whole process repeats itself in an infinite loop. After doing some Google search, it is suggested that this loop was caused by the partition being hidden or the mountmgr.sys file is missing. I checked my configuration and verified that this was not the case. I'm just wondering: Has anyone else experienced this and is there a solution for it? Is this what happens when you try to restore the image to a different partition on the same hard disk or is Partimage itself the problem? Should I be trying out a different partition cloning software?

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• File open fails initially when trying to open a file located on a win2k8 share but eventually can su

  - by Ruddy Douglass

  Core of the problem: I receive "(0x80070002) The system cannot find the file specified" for roughly 8 to 9 seconds before it can open it successfully. In a nutshell, we have two COM components. Component A calls into Component B and asks for a UNC filename to write to - the filename returned doesn't exist yet, but the path does - it then does its work, creates and populates the file, and tells Component B its done by making another com call. At that point Component B will call MoveFile to rename the file to its "official" name. This code has worked for (literally) years. Its works fine on win2k3. Its works fine when its running on win2k8 and points to a share on a win2k3 server. It also runs fine, if the share is actually located on the same win2k8 machine that the code is running on. But if you run it on win2k8 and point it to a share on a different win2k8 server, it fails. Both Component A & component B exist in their own Windows Service running with as a domain admin account. The shares are configured for "Everyone/Full control" in all test environments, similarly so are the underlying folders that the share points to. All machines are in the same domain. During debugging I realized the file actually does exist by the time I get to checking manually for it - after several iterations it occurred to me that the file doesn't "show up" until some delay passes by - so I put in the loop below in component B as shown below: int nCounter = 0; while (true) { CFileStatus fs; if (CFile::GetStatus(tempname, fs)) break; SleepEx(100, FALSE); nCounter++; } This code does, in fact, exit and nCounter is generally between 80 & 90 iterations when it does -- indicating the file "appears" approx 8 to 9 seconds later. Once that loop exits the code can successfully rename the file and all further processing appears to work. I put a CFile::GetStatus in component A immediately before it calls into Component B and that indicates success - it can see the file and get its true size yet the call into component b made immediately after can not see the file until the above indicated delay passes. I have verified the pathnames are precisely the same, even though it would clearly have to be for the calls to eventually succeed after a pause of 8 to 9 seconds... When something like this occurs I always assume there is a bug in my code until proven otherwise, but given (a) this code has executed properly for a very long time and (other than my diagnostic loop added) has not changed, and (b) it works in all environments except the win2k8 - win2k8 share, I'm guessing there is some OS issue in here that i do not understand. Any insight would be helpful. Thanks!

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• AutoHotKey - change mouse position and click a specific key every time window comes up

  - by John

  I'm a newbie to AHK, learning the basics. I'm using Notepad as an example - I want to hit the Cancel key every time I close Notepad and it asks if I want to Save/Don't Save/Cancel. I've come up with the script below and it works once but then I have to reload the script to do it again. I want it to hit Cancel every time the question box comes up. I thought Loop would work but am doing something wrong. Any ideas why, anyone? Loop IfWinExist Notepad, { WinWait Notepad WinActivate Click 312, 109 return }

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• File open fails initially when trying to open a file located on a win2k8 share but eventually can su

  - by Ruddy Douglass

  Core of the problem: I receive "(0x80070002) The system cannot find the file specified" for roughly 8 to 9 seconds before it can open it successfully. In a nutshell, we have two COM components. Component A calls into Component B and asks for a UNC filename to write to - the filename returned doesn't exist yet, but the path does - it then does its work, creates and populates the file, and tells Component B its done by making another com call. At that point Component B will call MoveFile to rename the file to its "official" name. This code has worked for (literally) years. Its works fine on win2k3. Its works fine when its running on win2k8 and points to a share on a win2k3 server. It also runs fine, if the share is actually located on the same win2k8 machine that the code is running on. But if you run it on win2k8 and point it to a share on a different win2k8 server, it fails. Both Component A & component B exist in their own Windows Service running with as a domain admin account. The shares are configured for "Everyone/Full control" in all test environments, similarly so are the underlying folders that the share points to. All machines are in the same domain. During debugging I realized the file actually does exist by the time I get to checking manually for it - after several iterations it occurred to me that the file doesn't "show up" until some delay passes by - so I put in the loop below in component B as shown below: int nCounter = 0; while (true) { CFileStatus fs; if (CFile::GetStatus(tempname, fs)) break; SleepEx(100, FALSE); nCounter++; } This code does, in fact, exit and nCounter is generally between 80 & 90 iterations when it does -- indicating the file "appears" approx 8 to 9 seconds later. Once that loop exits the code can successfully rename the file and all further processing appears to work. I put a CFile::GetStatus in component A immediately before it calls into Component B and that indicates success - it can see the file and get its true size yet the call into component b made immediately after can not see the file until the above indicated delay passes. I have verified the pathnames are precisely the same, even though it would clearly have to be for the calls to eventually succeed after a pause of 8 to 9 seconds... When something like this occurs I always assume there is a bug in my code until proven otherwise, but given (a) this code has executed properly for a very long time and (other than my diagnostic loop added) has not changed, and (b) it works in all environments except the win2k8 - win2k8 share, I'm guessing there is some OS issue in here that i do not understand. Any insight would be helpful. Thanks!

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• Redirect subdomain to hidden folder using mod_rewrite

  - by radious

  Hello! I want to keep my blog in subfolder domain_com/htdocs/blog and access it using blog.domain.com. I can obtain it using apache's mod_rewrite: RewriteEngine On RewriteBase / RewriteCond %{HTTP_HOST} ^blog\.domain\.com RewriteCond %{HTTP_HOST} !^/blog RewriteRule ^(.*)$ /blog/$1 [L] But I also want to redirect hxxp://domain.com/blog to hxxp://blog.domain.com (simply because I want to hide it from users). Simple redirection like: RewriteCond %{HTTP_HOST} ^wojtyniak\.com$ RewriteRule %{REQUEST_URI} ^/foo RewriteRule ^(.*)$ http://foo.wojtyniak.com [L,R=301] causes redirection loop. Is there any way to make such a redirection without loop? Big thanks! PS. Sorry for those hxxp thing, but serverfault thinks these are link and doesn't allow me to post more than one.

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• Windows XP Pro SP3 stop error code 0x000000F4

  - by Andrew Ford

  I have a system running Windows XP Pro SP3. My wife is the primary user of this system, and the last several days in a row, when she tries to log in to the system it gives her a BSOD with the stop error code 0x000000F4. The rest of the error codes change every time she tries to log on, but that one seems to stay constant. The error it gives me is: A process or thread crucial to system operation has unexpectedly exited or been terminated. The machine will also get stuck in a boot loop, where it keeps giving me the screen saying that windows did not start successfully, and to choose how to start windows. I have tried Safe Mode, Last known Good Config, and Normally, and all have resulted in either a return to the boot loop, or BSOD. What might this mean? How can I fix it, without doing a clean install?

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• change owner/uid of mount point upon mount

  - by Shiplu

  The scenario is like this. Bob has a computer. It crashed. Now he only has the hdd. The hdd is in ext3 format. He go to his office and told the sys admin John to mount this hdd and put the mount point in his home directory. John used the following fstab entries. # Bobs harddisk /media/TAPE4/Bobs-hdd.img /home/bob/myhdd/windows ntfs ro,loop,offset=32256 0 0 /media/TAPE4/Bobs-hdd.img /home/bob/myhdd/linux ext3 ro,loop,offset=14048810496 0 0 /media/TAPE4/Bobs-hdd.img /home/bob/myhdd/extra ntfs ro,loop,offset=28015335936 0 0 Bob was happy. He could access his old extra and windows. Specially the Documents and Settings in windows was helpful for him. But he found a problem. He is a web developer and all his websites are in linux/home/bob/public_html directory. When he tried to access that public_html directory he got permission_denied. He executed ls -lh he saw this. drwxr-xr-x 2 john john 4.0K Nov 9 2011 Desktop drwxr-xr-x 3 john john 4.0K Aug 12 2011 Documents drwxr-xr-x 3 john john 4.0K Aug 21 2011 public_html He contacted John thinking he might be mistakenly did this. But John couldn't find a way why this happend? Then one thing came into his mind file system hardly store username. They store uids. So he executed ls -ln drwxr-xr-x 2 1000 1000 4096 Nov 9 2011 Desktop drwxr-xr-x 3 1000 1000 4096 Aug 12 2011 Documents drwxr-xr-x 3 1000 1000 4096 Aug 21 2011 public_html John thinks 1000 is the first uid on a linux system. As he is the admin of the current system. He created his account first. so Johns uid was 1000. Bob also setup his private system and crated his account first. So Bobs uid was 1000 too. So thats an expected behavior. But problem remains. How can Bob access those websites in public_html?

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• Booting a Windows 7 installation on different hardware

  - by tomfanning

  I'm in a situation where I could do with very quickly migrating a Windows 7 (RTM x64) installation from one machine to another. What options are open to me in terms of getting W7 to boot after the drive is picked up and moved from one box to another? I thought it was supposed to be a little less sensitive to this kind of move than XP, but it doesn't work - it is stuck in a reboot loop and never reaches a GUI. Tried a few things so far, none of which have worked: Changed SATA mode in the BIOS of the target machine between ATA and AHCI run Windows 7 Startup Repair tried safe mode, no change (I will keep this list up to date as suggestions come in) UPDATE: I can confirm this reboot loop is due to STOP error 0x0000007B, and these codes follow: 0xFFFFF880009A98E8 0xFFFFFFFFC0000034 0x0000000000000000 0x0000000000000000 UPDATE: I didn't get anywhere on this and I ended up just rebuilding the machine. I think it should be theoretically possible, so I'm going to leave the question open in case someone comes along in future with an answer.

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• What's the utility of the return command in autohotkey?

  - by Shashank Sawant

  In the instances where the return command returns a value, the utility is obvious. I have seen the return command being used even when it is seemingly unnecessary. Let me show the following examples: Example 1: Loop { if a_index > 25 break ; Terminate the loop if a_index < 20 continue ; Skip the below and start a new iteration MsgBox, a_index = %a_index% ; This will display only the numbers 20 through 25 } Example 2: IfWinExist, Untitled - Notepad { WinActivate ; Automatically uses the window found above. return } Why is the return command used in Example 2 but is not used in Example 1? Both examples are copy-pasted/modified-pasted from the autohotkey.com's documentation.

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• Can't `mount -o loop` an ISO from an NFS share (RHEL)

  - by warren

  I have a large NFS share with a variety of software ISOs on it. I've only tried this on Red Hat Enterprise Linux, but when trying to do the following, the mount comes back with an error indicating no permissions to mount. Why would this be happening? NFS is mounted thusly: mediaserver:path/to/isos /media/nfs This is the mount call that fails mount -o loop /media/nfs/product.iso /tmp/product If I copy the ISO, there is no issue. The NFS share is mounted rw. How can I loop mount the ISO from the NFS share without copying it first?

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• VMware vSwitches and spanning tree

  - by dunxd

  I have two redundant core switches I want to connect to a new vSwitch I am setting up on a VMware ESX host. The switch will have two physical NICs each of which will connect to one of the core switches. The core switches are connected. If this was a physical switch, I would worry about connecting it to both core switches, because this would create a network loop. Do I need to worry about this for a VMware virtual switch? VMware's documentation says it is not possible to connect two vSwitches in a loop, therefore STP is not required. However, I am worried about connecting two physical switches together via a vSwitch.

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• SQL SERVER – Subquery or Join – Various Options – SQL Server Engine knows the Best

  - by pinaldave

  This is followup post of my earlier article SQL SERVER – Convert IN to EXISTS – Performance Talk, after reading all the comments I have received I felt that I could write more on the same subject to clear few things out. First let us run following four queries, all of them are giving exactly same resultset. USE AdventureWorks GO -- use of = SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID = ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- use of in SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID IN ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- use of exists SELECT * FROM HumanResources.Employee E WHERE EXISTS ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- Use of Join SELECT * FROM HumanResources.Employee E INNER JOIN HumanResources.EmployeeAddress EA ON E.EmployeeID = EA.EmployeeID GO Let us compare the execution plan of the queries listed above. Click on image to see larger image. It is quite clear from the execution plan that in case of IN, EXISTS and JOIN SQL Server Engines is smart enough to figure out what is the best optimal plan of Merge Join for the same query and execute the same. However, in the case of use of Equal (=) Operator, SQL Server is forced to use Nested Loop and test each result of the inner query and compare to outer query, leading to cut the performance. Please note that here I no mean suggesting that Nested Loop is bad or Merge Join is better. This can very well vary on your machine and amount of resources available on your computer. When I see Equal (=) operator used in query like above, I usually recommend to see if user can use IN or EXISTS or JOIN. As I said, this can very much vary on different system. What is your take in above query? I believe SQL Server Engines is usually pretty smart to figure out what is ideal execution plan and use it. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Joins, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Is recursion really bad?

  - by dotneteer

  After my previous post about the stack space, it appears that there is perception from the feedback that recursion is bad and we should avoid deep recursion. After writing a compiler, I know that the modern computer and compiler are complex enough and one cannot automatically assume that a hand crafted code would out-perform the compiler optimization. The only way is to do some prototype to find out. So why recursive code may not perform as well? Compilers place frames on a stack. In additional to arguments and local variables, compiles also need to place frame and program pointers on the frame, resulting in overheads. So why hand-crafted code may not performance as well? The stack used by a compiler is a simpler data structure and can grow and shrink cleanly. To replace recursion with out own stack, our stack is allocated in the heap that is far more complicated to manage. There could be overhead as well if the compiler needs to mark objects for garbage collection. Compiler also needs to worry about the memory fragmentation. Then there is additional complexity: CPUs have registers and multiple levels of cache. Register access is a few times faster than in-CPU cache access and is a few 10s times than on-board memory access. So it is up to the OS and compiler to maximize the use of register and in-CPU cache. For my particular problem, I did an experiment to rewrite my c# version of recursive code with a loop and stack approach. So here are the outcomes of the two approaches:   Recursive call Loop and Stack Lines of code for the algorithm 17 46 Speed Baseline 3% faster Readability Clean Far more complex So at the end, I was able to achieve 3% better performance with other drawbacks. My message is never assuming your sophisticated approach would automatically work out better than a simpler approach with a modern computer and compiler. Gage carefully before committing to a more complex approach.

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• How does an optimizing compiler react to a program with nested loops?

  - by D.Singh

  Say you have a bunch of nested loops. public void testMethod() { for(int i = 0; i<1203; i++){ //some computation for(int k=2; k<123; k++){ //some computation for(int j=2; j<12312; j++){ //some computation for(int l=2; l<123123; l++){ //some computation for(int p=2; p<12312; p++){ //some computation } } } } } } When the above code reaches the stage where the compiler will try to optimize it (I believe it's when the intermediate language needs to converted to machine code?), what will the compiler try to do? Is there any significant optimization that will take place? I understand that the optimizer will break up the loops by means of loop fission. But this is only per loop isn't it? What I mean with my question is will it take any action exclusively based on seeing the nested loops? Or will it just optimize the loops one by one? If the Java VM complicates the explanation then please just assume that it's C or C++ code.

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• 2D Procedural Terrain with box2d Assets

  - by Alex

  I'm making a game that invloves a tire moving through terrain that is generated randomly over 1000 points. The terrain is always a downwards incline like so: The actual box2d terrain extends one screen width behind and infront of the circular character. I'm now at a stage where I need to add gameplay elements to the terrain such as chasms or physical objects (like the demo polygon in the picture) and am not sure of the best way to structure the procedural generation of the terrain and objects. I currently have a very simple for loop like so: for(int i = 0; i < kMaxHillPoints; i++) { hillKeyPoints[i] = CGPointMake(terrainX, terrainY); if(i%50 == 0) { i += [self generateCasmAtIndex:i]; } terrainX += winsize.width/20; terrainY -= random() % ((int) winsize.height/20); } With the generateCasmAtIndex function add points to the hillKeyPoints array and incrementing the for loop by the required amount. If I want to generate box2d objects as well for specific terrain elements, I'll also have to keep track of the current position of the player and have some sort of array of box2d objects that need to be created at certain locations. I am not sure of an efficient way to accomplish this procedural generation of terrain elements with accompanying box2d objects. My thoughts are: 1) Have many functions for each terrain element (chasm, jump etc.) which add elements to be drawn to an array that is check on each game step - similar to what I've shown above. 2) Create an array of terrain element objects that string together and are looped over to create the terrain and generate the box2d objects. Each object would hold an array of points to be drawn and and array of accompanying box2d objects. Any help on this is much appreciated as I cannot see a 'clean' solution.

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• C string question

  - by user208454

  I am writing a simple c program which reverses a string, taking the string from argv[1]. Here is the code: #include <stdio.h> #include <stdlib.h> #include <string.h> char* flip_string(char *string){ int i = strlen(string); int j = 0; // Doesn't really matter all I wanted was the same size string for temp. char* temp = string; puts("This is the original string"); puts(string); puts("This is the \"temp\" string"); puts(temp); for(i; i>=0; i--){ temp[j] = string[i] if (j <= strlen(string)) { j++; } } return(temp); } int main(int argc, char *argv[]){ puts(flip_string(argv[1])); printf("This is the end of the program\n"); } That's basically it, the program compiles and everything but does not return the temp string in the end (just blank space). In the beginning it prints temp fine when its equal to string. Furthermore if I do a character by character printf of temp in the for loop the correct temp string in printed i.e. string - reversed. just when I try to print it to standard out (after the for loop/ or in the main) nothing happens only blank space is printed.

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• Glenn Fiedler's fixed timestep with fake threads

  - by kaoD

  I've implemented Glenn Fiedler's Fix Your Timestep! quite a few times in single-threaded games. Now I'm facing a different situation: I'm trying to do this in JavaScript. I know JS is single-threaded, but I plan on using requestAnimationFrame for the rendering part. This leaves me with two independent fake threads: simulation and rendering (I suppose requestAnimationFrame isn't really threaded, is it? I don't think so, it would BREAK JS.) Timing in these threads is independent too: dt for simulation and render is not the same. If I'm not mistaken, simulation should be up to Fiedler's while loop end. After the while loop, accumulator < dt so I'm left with some unspent time (dt) in the simulation thread. The problem comes in the draw/interpolation phase: const double alpha = accumulator / dt; State state = currentState*alpha + previousState * ( 1.0 - alpha ); render( state ); In my render callback, I have the current timestamp to which I can subtract the last-simulated-in-physics-timestamp to have a dt for the current frame. Should I just forget about this dt and draw using the physics thread's dt? It seems weird, since, well, I want to interpolate for the unspent time between simulation and render too, right? Of course, I want simulation and rendering to be completely independent, but I can't get around the fact that in Glenn's implementation the renderer produces time and the simulation consumes it in discrete dt sized chunks. A similar question was asked in Semi Fixed-timestep ported to javascript but the question doesn't really get to the point, and answers there point to removing physics from the render thread (which is what I'm trying to do) or just keeping physics in the render callback too (which is what I'm trying to avoid.)

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