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• Optimizing transition/movement smoothness for a 2D flash game.

  - by Tom

  Update 6: Fenomenas suggested me to re-create everything as simple as possible. I had my doubts that this would make any difference as the algorithm remains the same, and performance did not seem to be the issue. Anyway, it was the only suggestion I got so here it is: 30 FPS: http://www.feedpostal.com/test/simple/30/SimpleMovement.html 40 FPS: http://www.feedpostal.com/test/simple/40/SimpleMovement.html 60 FPS: http://www.feedpostal.com/test/simple/60/SimpleMovement.html 100 FPS: http://www.feedpostal.com/test/simple/100/SimpleMovement.html The code: package { import flash.display.Sprite; import flash.events.Event; import flash.events.KeyboardEvent; import flash.utils.getTimer; [SWF(width="800", height="600", frameRate="40", backgroundColor="#000000")] public class SimpleMovement extends Sprite { private static const TURNING_SPEED:uint = 180; private static const MOVEMENT_SPEED:uint = 400; private static const RADIAN_DIVIDE:Number = Math.PI/180; private var playerObject:Sprite; private var shipContainer:Sprite; private var moving:Boolean = false; private var turningMode:uint = 0; private var movementTimestamp:Number = getTimer(); private var turningTimestamp:Number = movementTimestamp; public function SimpleMovement() { //step 1: create player object playerObject = new Sprite(); playerObject.graphics.lineStyle(1, 0x000000); playerObject.graphics.beginFill(0x6D7B8D); playerObject.graphics.drawRect(0, 0, 25, 50); //make it rotate around the center playerObject.x = 0 - playerObject.width / 2; playerObject.y = 0 - playerObject.height / 2; shipContainer = new Sprite(); shipContainer.addChild(playerObject); shipContainer.x = 100; shipContainer.y = 100; shipContainer.rotation = 180; addChild(shipContainer); //step 2: install keyboard hook when stage is ready addEventListener(Event.ADDED_TO_STAGE, stageReady, false, 0, true); //step 3: install rendering update poll addEventListener(Event.ENTER_FRAME, updatePoller, false, 0, true); } private function updatePoller(event:Event):void { var newTime:Number = getTimer(); //turning if (turningMode != 0) { var turningDeltaTime:Number = newTime - turningTimestamp; turningTimestamp = newTime; var rotation:Number = TURNING_SPEED * turningDeltaTime / 1000; if (turningMode == 1) shipContainer.rotation -= rotation; else shipContainer.rotation += rotation; } //movement if (moving) { var movementDeltaTime:Number = newTime - movementTimestamp; movementTimestamp = newTime; var distance:Number = MOVEMENT_SPEED * movementDeltaTime / 1000; var rAngle:Number = shipContainer.rotation * RADIAN_DIVIDE; //convert degrees to radian shipContainer.x += distance * Math.sin(rAngle); shipContainer.y -= distance * Math.cos(rAngle); } } private function stageReady(event:Event):void { //install keyboard hook stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDown, false, 0, true); stage.addEventListener(KeyboardEvent.KEY_UP, keyUp, false, 0, true); } private final function keyDown(event:KeyboardEvent):void { if ((event.keyCode == 87) && (!moving)) //87 = W { movementTimestamp = getTimer(); moving = true; } if ((event.keyCode == 65) && (turningMode != 1)) //65 = A { turningTimestamp = getTimer(); turningMode = 1; } else if ((event.keyCode == 68) && (turningMode != 2)) //68 = D { turningTimestamp = getTimer(); turningMode = 2; } } private final function keyUp(event:KeyboardEvent):void { if ((event.keyCode == 87) && (moving)) moving = false; //87 = W if (((event.keyCode == 65) || (event.keyCode == 68)) && (turningMode != 0)) turningMode = 0; //65 = A, 68 = D } } } The results were as I expected. Absolutely no improvement. I really hope that someone has another suggestion as this thing needs fixing. Also, I doubt it's my system as I have a pretty good one (8GB RAM, Q9550 QuadCore intel, ATI Radeon 4870 512MB). Also, everyone else I asked so far had the same issue with my client. Update 5: another example of a smooth flash game just to demonstrate that my movement definitely is different! See http://www.spel.nl/game/bumpercraft.html Update 4: I traced the time before rendering (EVENT.RENDER) and right after rendering (EVENT.ENTER_FRAME), the results: rendering took: 14 ms rendering took: 14 ms rendering took: 12 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 14 ms rendering took: 12 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 14 ms rendering took: 12 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 14 ms rendering took: 14 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 24 ms rendering took: 18 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 232 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms rendering took: 14 ms rendering took: 16 ms rendering took: 12 ms rendering took: 14 ms rendering took: 12 ms The range is 12-16 ms. During these differences, the shocking/warping/flickering movement was already going on. There is also 1 peak of 232ms, at this time there was a relatively big warp. This is however not the biggest problme, the biggest problem are the continuous small warps during normal movement. Does this give anyone a clue? Update 3: After testing, I know that the following factors are not causing my problem: Bitmap's quality - changed with photoshop to an uglier 8 colours optimized graphic, no improvement at all. Constant rotation of image while turning - disabled it, no improvement at all Browser rendering - tried to use the flash player standalone, no improvement at all I am 100% convinced that the problem lies in either my code or in my algorithm. Please, help me out. It has been almost two weeks (1 week that I asked this question on SO) now and I still have to get my golden answer. Update 1: see bottom for full flex project source and a live demo demonstrating my problem. I'm working on a 2d flash game. Player ships are created as an object: ships[id] = new GameShip(); When movement and rotation information is available, this is being directed to the corresponding ship: ships[id].setMovementMode(1); //move forward Now, within this GameShip object movement works using the "Event.ENTER_FRAME" event: addEventListener(Event.ENTER_FRAME, movementHandler); The following function is then being run: private final function movementHandler(event:Event):void { var newTimeStamp:uint = UtilLib.getTimeStamp(); //set current timeStamp var distance:Number = (newTimeStamp - movementTimeStamp) / 1000 * movementSpeed; //speed = x pixels forward every 1 second movementTimeStamp = newTimeStamp; //update old timeStamp var diagonalChange:Array = getDiagonalChange(movementAngle, distance); //the diagonal position update based on angle and distance charX += diagonalChange[0]; charY += diagonalChange[1]; if (shipContainer) { //when the container is ready to be worked with shipContainer.x = charX; shipContainer.y = charY; } } private final function getDiagonalChange(angle:Number, distance:Number):Array { var rAngle:Number = angle * Math.PI/180; //convert degrees to radian return [Math.sin(rAngle) * distance, (Math.cos(rAngle) * distance) * -1]; } When the object is no longer moving, the event listener will be removed. The same method is being used for rotation. Everything works almost perfect. I've set the project's target FPS to 100 and created a FPS counter. According to the FPS counter, the average FPS in firefox is around 100, while the top is 1000 and the bottom is 22. I think that the bottom and top FPSs are only happening during the initialization of the client (startup). The problem is that the ship appears to be almost perfectly smooth, while it should be just that without the "almost" part. It's almost as if the ship is "flickering" very very fast, you can't actually see it but it's hard to focus on the object while it's moving with your eyes. Also, every now and then, there seems to be a bit of a framerate spike, as if the client is skipping a couple of frames, you then see it quickly warp. It is very difficult to explain what the real problem is, but in general it's that the movement is not perfectly smooth. So, do you have any suggestions on how to make the movement or transition of objects perfectly smooth? Update 1: I re-created the client to demonstrate my problem. Please check it out. The client: http://feedpostal.com/test/MovementTest.html The Actionscript Project (full source): http://feedpostal.com/test/MovementTest.rar An example of a smooth flash game (not created by me): http://www.gamesforwork.com/games/swf/Mission%20Racing_august_10th_2009.swf It took me a pretty long time to recreate this client side version, I hope this will help with solving the problem. Please note: yes, it is actually pretty smooth. But it is definitely not smooth enough.

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• SQL Server &ndash; Undelete a Table and Restore a Single Table from Backup

  - by Mladen Prajdic

  This post is part of the monthly community event called T-SQL Tuesday started by Adam Machanic (blog|twitter) and hosted by someone else each month. This month the host is Sankar Reddy (blog|twitter) and the topic is Misconceptions in SQL Server. You can follow posts for this theme on Twitter by looking at #TSQL2sDay hashtag. Let me start by saying: This code is a crazy hack that is to never be used unless you really, really have to. Really! And I don’t think there’s a time when you would really have to use it for real. Because it’s a hack there are number of things that can go wrong so play with it knowing that. I’ve managed to totally corrupt one database. :) Oh… and for those saying: yeah yeah.. you have a single table in a file group and you’re restoring that, I say “nay nay” to you. As we all know SQL Server can’t do single table restores from backup. This is kind of a obvious thing due to different relational integrity (RI) concerns. Since we have to maintain that we have to restore all tables represented in a RI graph. For this exercise i say BAH! to those concerns. Note that this method “works” only for simple tables that don’t have LOB and off rows data. The code can be expanded to include those but I’ve tried to leave things “simple”. Note that for this to work our table needs to be relatively static data-wise. This doesn’t work for OLTP table. Products are a perfect example of static data. They don’t change much between backups, pretty much everything depends on them and their table is one of those tables that are relatively easy to accidentally delete everything from. This only works if the database is in Full or Bulk-Logged recovery mode for tables where the contents have been deleted or truncated but NOT when a table was dropped. Everything we’ll talk about has to be done before the data pages are reused for other purposes. After deletion or truncation the pages are marked as reusable so you have to act fast. The best thing probably is to put the database into single user mode ASAP while you’re performing this procedure and return it to multi user after you’re done. How do we do it? We will be using an undocumented but known DBCC commands: DBCC PAGE, an undocumented function sys.fn_dblog and a little known DATABASE RESTORE PAGE option. All tests will be on a copy of Production.Product table in AdventureWorks database called Production.Product1 because the original table has FK constraints that prevent us from truncating it for testing. -- create a duplicate table. This doesn't preserve indexes!SELECT *INTO AdventureWorks.Production.Product1FROM AdventureWorks.Production.Product   After we run this code take a full back to perform further testing.   First let’s see what the difference between DELETE and TRUNCATE is when it comes to logging. With DELETE every row deletion is logged in the transaction log. With TRUNCATE only whole data page deallocations are logged in the transaction log. Getting deleted data pages is simple. All we have to look for is row delete entry in the sys.fn_dblog output. But getting data pages that were truncated from the transaction log presents a bit of an interesting problem. I will not go into depths of IAM(Index Allocation Map) and PFS (Page Free Space) pages but suffice to say that every IAM page has intervals that tell us which data pages are allocated for a table and which aren’t. If we deep dive into the sys.fn_dblog output we can see that once you truncate a table all the pages in all the intervals are deallocated and this is shown in the PFS page transaction log entry as deallocation of pages. For every 8 pages in the same extent there is one PFS page row in the transaction log. This row holds information about all 8 pages in CSV format which means we can get to this data with some parsing. A great help for parsing this stuff is Peter Debetta’s handy function dbo.HexStrToVarBin that converts hexadecimal string into a varbinary value that can be easily converted to integer tus giving us a readable page number. The shortened (columns removed) sys.fn_dblog output for a PFS page with CSV data for 1 extent (8 data pages) looks like this: -- [Page ID] is displayed in hex format. -- To convert it to readable int we'll use dbo.HexStrToVarBin function found at -- http://sqlblog.com/blogs/peter_debetta/archive/2007/03/09/t-sql-convert-hex-string-to-varbinary.aspx -- This function must be installed in the master databaseSELECT Context, AllocUnitName, [Page ID], DescriptionFROM sys.fn_dblog(NULL, NULL)WHERE [Current LSN] = '00000031:00000a46:007d' The pages at the end marked with 0x00—> are pages that are allocated in the extent but are not part of a table. We can inspect the raw content of each data page with a DBCC PAGE command: -- we need this trace flag to redirect output to the query window.DBCC TRACEON (3604); -- WITH TABLERESULTS gives us data in table format instead of message format-- we use format option 3 because it's the easiest to read and manipulate further onDBCC PAGE (AdventureWorks, 1, 613, 3) WITH TABLERESULTS   Since the DBACC PAGE output can be quite extensive I won’t put it here. You can see an example of it in the link at the beginning of this section. Getting deleted data back When we run a delete statement every row to be deleted is marked as a ghost record. A background process periodically cleans up those rows. A huge misconception is that the data is actually removed. It’s not. Only the pointers to the rows are removed while the data itself is still on the data page. We just can’t access it with normal means. To get those pointers back we need to restore every deleted page using the RESTORE PAGE option mentioned above. This restore must be done from a full backup, followed by any differential and log backups that you may have. This is necessary to bring the pages up to the same point in time as the rest of the data.  However the restore doesn’t magically connect the restored page back to the original table. It simply replaces the current page with the one from the backup. After the restore we use the DBCC PAGE to read data directly from all data pages and insert that data into a temporary table. To finish the RESTORE PAGE  procedure we finally have to take a tail log backup (simple backup of the transaction log) and restore it back. We can now insert data from the temporary table to our original table by hand. Getting truncated data back When we run a truncate the truncated data pages aren’t touched at all. Even the pointers to rows stay unchanged. Because of this getting data back from truncated table is simple. we just have to find out which pages belonged to our table and use DBCC PAGE to read data off of them. No restore is necessary. Turns out that the problems we had with finding the data pages is alleviated by not having to do a RESTORE PAGE procedure. Stop stalling… show me The Code! This is the code for getting back deleted and truncated data back. It’s commented in all the right places so don’t be afraid to take a closer look. Make sure you have a full backup before trying this out. Also I suggest that the last step of backing and restoring the tail log is performed by hand. USE masterGOIF OBJECT_ID('dbo.HexStrToVarBin') IS NULL RAISERROR ('No dbo.HexStrToVarBin installed. Go to http://sqlblog.com/blogs/peter_debetta/archive/2007/03/09/t-sql-convert-hex-string-to-varbinary.aspx and install it in master database' , 18, 1) SET NOCOUNT ONBEGIN TRY DECLARE @dbName VARCHAR(1000), @schemaName VARCHAR(1000), @tableName VARCHAR(1000), @fullBackupName VARCHAR(1000), @undeletedTableName VARCHAR(1000), @sql VARCHAR(MAX), @tableWasTruncated bit; /* THE FIRST LINE ARE OUR INPUT PARAMETERS In this case we're trying to recover Production.Product1 table in AdventureWorks database. My full backup of AdventureWorks database is at e:\AW.bak */ SELECT @dbName = 'AdventureWorks', @schemaName = 'Production', @tableName = 'Product1', @fullBackupName = 'e:\AW.bak', @undeletedTableName = '##' + @tableName + '_Undeleted', @tableWasTruncated = 0, -- copy the structure from original table to a temp table that we'll fill with restored data @sql = 'IF OBJECT_ID(''tempdb..' + @undeletedTableName + ''') IS NOT NULL DROP TABLE ' + @undeletedTableName + ' SELECT *' + ' INTO ' + @undeletedTableName + ' FROM [' + @dbName + '].[' + @schemaName + '].[' + @tableName + ']' + ' WHERE 1 = 0' EXEC (@sql) IF OBJECT_ID('tempdb..#PagesToRestore') IS NOT NULL DROP TABLE #PagesToRestore /* FIND DATA PAGES WE NEED TO RESTORE*/ CREATE TABLE #PagesToRestore ([ID] INT IDENTITY(1,1), [FileID] INT, [PageID] INT, [SQLtoExec] VARCHAR(1000)) -- DBCC PACE statement to run later RAISERROR ('Looking for deleted pages...', 10, 1) -- use T-LOG direct read to get deleted data pages INSERT INTO #PagesToRestore([FileID], [PageID], [SQLtoExec]) EXEC('USE [' + @dbName + '];SELECT FileID, PageID, ''DBCC TRACEON (3604); DBCC PAGE ([' + @dbName + '], '' + FileID + '', '' + PageID + '', 3) WITH TABLERESULTS'' as SQLToExecFROM (SELECT DISTINCT LEFT([Page ID], 4) AS FileID, CONVERT(VARCHAR(100), ' + 'CONVERT(INT, master.dbo.HexStrToVarBin(SUBSTRING([Page ID], 6, 20)))) AS PageIDFROM sys.fn_dblog(NULL, NULL)WHERE AllocUnitName LIKE ''%' + @schemaName + '.' + @tableName + '%'' ' + 'AND Context IN (''LCX_MARK_AS_GHOST'', ''LCX_HEAP'') AND Operation in (''LOP_DELETE_ROWS''))t');SELECT *FROM #PagesToRestore -- if upper EXEC returns 0 rows it means the table was truncated so find truncated pages IF (SELECT COUNT(*) FROM #PagesToRestore) = 0 BEGIN RAISERROR ('No deleted pages found. Looking for truncated pages...', 10, 1) -- use T-LOG read to get truncated data pages INSERT INTO #PagesToRestore([FileID], [PageID], [SQLtoExec]) -- dark magic happens here -- because truncation simply deallocates pages we have to find out which pages were deallocated. -- we can find this out by looking at the PFS page row's Description column. -- for every deallocated extent the Description has a CSV of 8 pages in that extent. -- then it's just a matter of parsing it. -- we also remove the pages in the extent that weren't allocated to the table itself -- marked with '0x00-->00' EXEC ('USE [' + @dbName + '];DECLARE @truncatedPages TABLE(DeallocatedPages VARCHAR(8000), IsMultipleDeallocs BIT);INSERT INTO @truncatedPagesSELECT REPLACE(REPLACE(Description, ''Deallocated '', ''Y''), ''0x00-->00 '', ''N'') + '';'' AS DeallocatedPages, CHARINDEX('';'', Description) AS IsMultipleDeallocsFROM (SELECT DISTINCT LEFT([Page ID], 4) AS FileID, CONVERT(VARCHAR(100), CONVERT(INT, master.dbo.HexStrToVarBin(SUBSTRING([Page ID], 6, 20)))) AS PageID, DescriptionFROM sys.fn_dblog(NULL, NULL)WHERE Context IN (''LCX_PFS'') AND Description LIKE ''Deallocated%'' AND AllocUnitName LIKE ''%' + @schemaName + '.' + @tableName + '%'') t;SELECT FileID, PageID , ''DBCC TRACEON (3604); DBCC PAGE ([' + @dbName + '], '' + FileID + '', '' + PageID + '', 3) WITH TABLERESULTS'' as SQLToExecFROM (SELECT LEFT(PageAndFile, 1) as WasPageAllocatedToTable , SUBSTRING(PageAndFile, 2, CHARINDEX('':'', PageAndFile) - 2 ) as FileID , CONVERT(VARCHAR(100), CONVERT(INT, master.dbo.HexStrToVarBin(SUBSTRING(PageAndFile, CHARINDEX('':'', PageAndFile) + 1, LEN(PageAndFile))))) as PageIDFROM ( SELECT SUBSTRING(DeallocatedPages, delimPosStart, delimPosEnd - delimPosStart) as PageAndFile, IsMultipleDeallocs FROM ( SELECT *, CHARINDEX('';'', DeallocatedPages)*(N-1) + 1 AS delimPosStart, CHARINDEX('';'', DeallocatedPages)*N AS delimPosEnd FROM @truncatedPages t1 CROSS APPLY (SELECT TOP (case when t1.IsMultipleDeallocs = 1 then 8 else 1 end) ROW_NUMBER() OVER(ORDER BY number) as N FROM master..spt_values) t2 )t)t)tWHERE WasPageAllocatedToTable = ''Y''') SELECT @tableWasTruncated = 1 END DECLARE @lastID INT, @pagesCount INT SELECT @lastID = 1, @pagesCount = COUNT(*) FROM #PagesToRestore SELECT @sql = 'Number of pages to restore: ' + CONVERT(VARCHAR(10), @pagesCount) IF @pagesCount = 0 RAISERROR ('No data pages to restore.', 18, 1) ELSE RAISERROR (@sql, 10, 1) -- If the table was truncated we'll read the data directly from data pages without restoring from backup IF @tableWasTruncated = 0 BEGIN -- RESTORE DATA PAGES FROM FULL BACKUP IN BATCHES OF 200 WHILE @lastID <= @pagesCount BEGIN -- create CSV string of pages to restore SELECT @sql = STUFF((SELECT ',' + CONVERT(VARCHAR(100), FileID) + ':' + CONVERT(VARCHAR(100), PageID) FROM #PagesToRestore WHERE ID BETWEEN @lastID AND @lastID + 200 ORDER BY ID FOR XML PATH('')), 1, 1, '') SELECT @sql = 'RESTORE DATABASE [' + @dbName + '] PAGE = ''' + @sql + ''' FROM DISK = ''' + @fullBackupName + '''' RAISERROR ('Starting RESTORE command:' , 10, 1) WITH NOWAIT; RAISERROR (@sql , 10, 1) WITH NOWAIT; EXEC(@sql); RAISERROR ('Restore DONE' , 10, 1) WITH NOWAIT; SELECT @lastID = @lastID + 200 END /* If you have any differential or transaction log backups you should restore them here to bring the previously restored data pages up to date */ END DECLARE @dbccSinglePage TABLE ( [ParentObject] NVARCHAR(500), [Object] NVARCHAR(500), [Field] NVARCHAR(500), [VALUE] NVARCHAR(MAX) ) DECLARE @cols NVARCHAR(MAX), @paramDefinition NVARCHAR(500), @SQLtoExec VARCHAR(1000), @FileID VARCHAR(100), @PageID VARCHAR(100), @i INT = 1 -- Get deleted table columns from information_schema view -- Need sp_executeSQL because database name can't be passed in as variable SELECT @cols = 'select @cols = STUFF((SELECT '', ['' + COLUMN_NAME + '']''FROM ' + @dbName + '.INFORMATION_SCHEMA.COLUMNSWHERE TABLE_NAME = ''' + @tableName + ''' AND TABLE_SCHEMA = ''' + @schemaName + '''ORDER BY ORDINAL_POSITIONFOR XML PATH('''')), 1, 2, '''')', @paramDefinition = N'@cols nvarchar(max) OUTPUT' EXECUTE sp_executesql @cols, @paramDefinition, @cols = @cols OUTPUT -- Loop through all the restored data pages, -- read data from them and insert them into temp table -- which you can then insert into the orignial deleted table DECLARE dbccPageCursor CURSOR GLOBAL FORWARD_ONLY FOR SELECT [FileID], [PageID], [SQLtoExec] FROM #PagesToRestore ORDER BY [FileID], [PageID] OPEN dbccPageCursor; FETCH NEXT FROM dbccPageCursor INTO @FileID, @PageID, @SQLtoExec; WHILE @@FETCH_STATUS = 0 BEGIN RAISERROR ('---------------------------------------------', 10, 1) WITH NOWAIT; SELECT @sql = 'Loop iteration: ' + CONVERT(VARCHAR(10), @i); RAISERROR (@sql, 10, 1) WITH NOWAIT; SELECT @sql = 'Running: ' + @SQLtoExec RAISERROR (@sql, 10, 1) WITH NOWAIT; -- if something goes wrong with DBCC execution or data gathering, skip it but print error BEGIN TRY INSERT INTO @dbccSinglePage EXEC (@SQLtoExec) -- make the data insert magic happen here IF (SELECT CONVERT(BIGINT, [VALUE]) FROM @dbccSinglePage WHERE [Field] LIKE '%Metadata: ObjectId%') = OBJECT_ID('['+@dbName+'].['+@schemaName +'].['+@tableName+']') BEGIN DELETE @dbccSinglePage WHERE NOT ([ParentObject] LIKE 'Slot % Offset %' AND [Object] LIKE 'Slot % Column %') SELECT @sql = 'USE tempdb; ' + 'IF (OBJECTPROPERTY(object_id(''' + @undeletedTableName + '''), ''TableHasIdentity'') = 1) ' + 'SET IDENTITY_INSERT ' + @undeletedTableName + ' ON; ' + 'INSERT INTO ' + @undeletedTableName + '(' + @cols + ') ' + STUFF((SELECT ' UNION ALL SELECT ' + STUFF((SELECT ', ' + CASE WHEN VALUE = '[NULL]' THEN 'NULL' ELSE '''' + [VALUE] + '''' END FROM ( -- the unicorn help here to correctly set ordinal numbers of columns in a data page -- it's turning STRING order into INT order (1,10,11,2,21 into 1,2,..10,11...21) SELECT [ParentObject], [Object], Field, VALUE, RIGHT('00000' + O1, 6) AS ParentObjectOrder, RIGHT('00000' + REVERSE(LEFT(O2, CHARINDEX(' ', O2)-1)), 6) AS ObjectOrder FROM ( SELECT [ParentObject], [Object], Field, VALUE, REPLACE(LEFT([ParentObject], CHARINDEX('Offset', [ParentObject])-1), 'Slot ', '') AS O1, REVERSE(LEFT([Object], CHARINDEX('Offset ', [Object])-2)) AS O2 FROM @dbccSinglePage WHERE t.ParentObject = ParentObject )t)t ORDER BY ParentObjectOrder, ObjectOrder FOR XML PATH('')), 1, 2, '') FROM @dbccSinglePage t GROUP BY ParentObject FOR XML PATH('') ), 1, 11, '') + ';' RAISERROR (@sql, 10, 1) WITH NOWAIT; EXEC (@sql) END END TRY BEGIN CATCH SELECT @sql = 'ERROR!!!' + CHAR(10) + CHAR(13) + 'ErrorNumber: ' + ERROR_NUMBER() + '; ErrorMessage' + ERROR_MESSAGE() + CHAR(10) + CHAR(13) + 'FileID: ' + @FileID + '; PageID: ' + @PageID RAISERROR (@sql, 10, 1) WITH NOWAIT; END CATCH DELETE @dbccSinglePage SELECT @sql = 'Pages left to process: ' + CONVERT(VARCHAR(10), @pagesCount - @i) + CHAR(10) + CHAR(13) + CHAR(10) + CHAR(13) + CHAR(10) + CHAR(13), @i = @i+1 RAISERROR (@sql, 10, 1) WITH NOWAIT; FETCH NEXT FROM dbccPageCursor INTO @FileID, @PageID, @SQLtoExec; END CLOSE dbccPageCursor; DEALLOCATE dbccPageCursor; EXEC ('SELECT ''' + @undeletedTableName + ''' as TableName; SELECT * FROM ' + @undeletedTableName)END TRYBEGIN CATCH SELECT ERROR_NUMBER() AS ErrorNumber, ERROR_MESSAGE() AS ErrorMessage IF CURSOR_STATUS ('global', 'dbccPageCursor') >= 0 BEGIN CLOSE dbccPageCursor; DEALLOCATE dbccPageCursor; ENDEND CATCH-- if the table was deleted we need to finish the restore page sequenceIF @tableWasTruncated = 0BEGIN -- take a log tail backup and then restore it to complete page restore process DECLARE @currentDate VARCHAR(30) SELECT @currentDate = CONVERT(VARCHAR(30), GETDATE(), 112) RAISERROR ('Starting Log Tail backup to c:\Temp ...', 10, 1) WITH NOWAIT; PRINT ('BACKUP LOG [' + @dbName + '] TO DISK = ''c:\Temp\' + @dbName + '_TailLogBackup_' + @currentDate + '.trn''') EXEC ('BACKUP LOG [' + @dbName + '] TO DISK = ''c:\Temp\' + @dbName + '_TailLogBackup_' + @currentDate + '.trn''') RAISERROR ('Log Tail backup done.', 10, 1) WITH NOWAIT; RAISERROR ('Starting Log Tail restore from c:\Temp ...', 10, 1) WITH NOWAIT; PRINT ('RESTORE LOG [' + @dbName + '] FROM DISK = ''c:\Temp\' + @dbName + '_TailLogBackup_' + @currentDate + '.trn''') EXEC ('RESTORE LOG [' + @dbName + '] FROM DISK = ''c:\Temp\' + @dbName + '_TailLogBackup_' + @currentDate + '.trn''') RAISERROR ('Log Tail restore done.', 10, 1) WITH NOWAIT;END-- The last step is manual. Insert data from our temporary table to the original deleted table The misconception here is that you can do a single table restore properly in SQL Server. You can't. But with little experimentation you can get pretty close to it. One way to possible remove a dependency on a backup to retrieve deleted pages is to quickly run a similar script to the upper one that gets data directly from data pages while the rows are still marked as ghost records. It could be done if we could beat the ghost record cleanup task.

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• How do I make my page respect h1 css addition? [migrated]

  - by Adobe

  I add h1 { margin-top:100px; } to the end of the css, but the page doesn't change. But if I add to the html of some h1: <h1 style="margin-top:100px;"><a class="toc-backref" href="#id4">KHotKeys</a><a class="headerlink" href="#khotkeys" title="Permalink to this headline">¶</a></h1> Then it does. I'm not css pro, and I guess the problem is somewhere in the css file. Here it is: div.clearer { clear: both; } /* -- relbar ---------------------------------------------------------------- */ div.related { width: 100%; font-size: 90%; } div.related h3 { display: none; } div.related ul { margin: 0; padding: 0 0 0 10px; list-style: none; } div.related li { display: inline; } div.related li.right { float: right; margin-right: 5px; } /* -- sidebar --------------------------------------------------------------- */ div.sphinxsidebarwrapper { padding: 10px 5px 0 10px; } div.sphinxsidebar { float: left; width: 230px; margin-left: -100%; font-size: 90%; } div.sphinxsidebar ul { list-style: none; } div.sphinxsidebar ul ul, div.sphinxsidebar ul.want-points { margin-left: 20px; list-style: square; } div.sphinxsidebar ul ul { margin-top: 0; margin-bottom: 0; } div.sphinxsidebar form { margin-top: 10px; } div.sphinxsidebar input { border: 1px solid #98dbcc; font-family: sans-serif; font-size: 1em; } div.sphinxsidebar input[type="text"] { width: 160px; } div.sphinxsidebar input[type="submit"] { width: 30px; } img { border: 0; } /* -- search page ----------------------------------------------------------- */ ul.search { margin: 10px 0 0 20px; padding: 0; } ul.search li { padding: 5px 0 5px 20px; background-image: url(file.png); background-repeat: no-repeat; background-position: 0 7px; } ul.search li a { font-weight: bold; } ul.search li div.context { color: #888; margin: 2px 0 0 30px; text-align: left; } ul.keywordmatches li.goodmatch a { font-weight: bold; } /* -- index page ------------------------------------------------------------ */ table.contentstable { width: 90%; } table.contentstable p.biglink { line-height: 150%; } a.biglink { font-size: 1.3em; } span.linkdescr { font-style: italic; padding-top: 5px; font-size: 90%; } /* -- general index --------------------------------------------------------- */ table.indextable { width: 100%; } table.indextable td { text-align: left; vertical-align: top; } table.indextable dl, table.indextable dd { margin-top: 0; margin-bottom: 0; } table.indextable tr.pcap { height: 10px; } table.indextable tr.cap { margin-top: 10px; background-color: #f2f2f2; } img.toggler { margin-right: 3px; margin-top: 3px; cursor: pointer; } div.modindex-jumpbox { border-top: 1px solid #ddd; border-bottom: 1px solid #ddd; margin: 1em 0 1em 0; padding: 0.4em; } div.genindex-jumpbox { border-top: 1px solid #ddd; border-bottom: 1px solid #ddd; margin: 1em 0 1em 0; padding: 0.4em; } /* -- general body styles --------------------------------------------------- */ a.headerlink { visibility: hidden; } h1:hover > a.headerlink, h2:hover > a.headerlink, h3:hover > a.headerlink, h4:hover > a.headerlink, h5:hover > a.headerlink, h6:hover > a.headerlink, dt:hover > a.headerlink { visibility: visible; } div.body p.caption { text-align: inherit; } div.body td { text-align: left; } .field-list ul { padding-left: 1em; } .first { margin-top: 0 !important; } p.rubric { margin-top: 30px; font-weight: bold; } img.align-left, .figure.align-left, object.align-left { clear: left; float: left; margin-right: 1em; } img.align-right, .figure.align-right, object.align-right { clear: right; float: right; margin-left: 1em; } img.align-center, .figure.align-center, object.align-center { display: block; margin-left: auto; margin-right: auto; } .align-left { text-align: left; } .align-center { text-align: center; } .align-right { text-align: right; } /* -- sidebars -------------------------------------------------------------- */ div.sidebar { margin: 0 0 0.5em 1em; border: 1px solid #ddb; padding: 7px 7px 0 7px; background-color: #ffe; width: 40%; float: right; } p.sidebar-title { font-weight: bold; } /* -- topics ---------------------------------------------------------------- */ div.topic { border: 1px solid #ccc; padding: 7px 7px 0 7px; margin: 10px 0 10px 0; } p.topic-title { font-size: 1.1em; font-weight: bold; margin-top: 10px; } /* -- admonitions ----------------------------------------------------------- */ div.admonition { margin-top: 10px; margin-bottom: 10px; padding: 7px; } div.admonition dt { font-weight: bold; } div.admonition dl { margin-bottom: 0; } p.admonition-title { margin: 0px 10px 5px 0px; font-weight: bold; } div.body p.centered { text-align: center; margin-top: 25px; } /* -- tables ---------------------------------------------------------------- */ table.docutils { border: 0; border-collapse: collapse; } table.docutils td, table.docutils th { padding: 1px 8px 1px 5px; border-top: 0; border-left: 0; border-right: 0; border-bottom: 1px solid #aaa; } table.field-list td, table.field-list th { border: 0 !important; } table.footnote td, table.footnote th { border: 0 !important; } th { text-align: left; padding-right: 5px; } table.citation { border-left: solid 1px gray; margin-left: 1px; } table.citation td { border-bottom: none; } /* -- other body styles ----------------------------------------------------- */ ol.arabic { list-style: decimal; } ol.loweralpha { list-style: lower-alpha; } ol.upperalpha { list-style: upper-alpha; } ol.lowerroman { list-style: lower-roman; } ol.upperroman { list-style: upper-roman; } dl { margin-bottom: 15px; } dd p { margin-top: 0px; } dd ul, dd table { margin-bottom: 10px; } dd { margin-top: 3px; margin-bottom: 10px; margin-left: 30px; } dt:target, .highlighted { background-color: #fbe54e; } dl.glossary dt { font-weight: bold; font-size: 1.1em; } .field-list ul { margin: 0; padding-left: 1em; } .field-list p { margin: 0; } .refcount { color: #060; } .optional { font-size: 1.3em; } .versionmodified { font-style: italic; } .system-message { background-color: #fda; padding: 5px; border: 3px solid red; } .footnote:target { background-color: #ffa; } .line-block { display: block; margin-top: 1em; margin-bottom: 1em; } .line-block .line-block { margin-top: 0; margin-bottom: 0; margin-left: 1.5em; } .guilabel, .menuselection { font-family: sans-serif; } .accelerator { text-decoration: underline; } .classifier { font-style: oblique; } /* -- code displays --------------------------------------------------------- */ pre { overflow: auto; overflow-y: hidden; /* fixes display issues on Chrome browsers */ } td.linenos pre { padding: 5px 0px; border: 0; background-color: transparent; color: #aaa; } table.highlighttable { margin-left: 0.5em; } table.highlighttable td { padding: 0 0.5em 0 0.5em; } tt.descname { background-color: transparent; font-weight: bold; font-size: 1.2em; } tt.descclassname { background-color: transparent; } tt.xref, a tt { background-color: transparent; font-weight: bold; } h1 tt, h2 tt, h3 tt, h4 tt, h5 tt, h6 tt { background-color: transparent; } .viewcode-link { float: right; } .viewcode-back { float: right; font-family: sans-serif; } div.viewcode-block:target { margin: -1px -10px; padding: 0 10px; } /* -- math display ---------------------------------------------------------- */ img.math { vertical-align: middle; } div.body div.math p { text-align: center; } span.eqno { float: right; } /* -- printout stylesheet --------------------------------------------------- */ @media print { div.document, div.documentwrapper, div.bodywrapper { margin: 0 !important; width: 100%; } div.sphinxsidebar, div.related, div.footer, #top-link { display: none; } } body { font-family: sans-serif; font-size: 100%; background-color: #11303d; color: #000; margin: 0; padding: 0; } div.document { background-color: #d4e9f7; } div.documentwrapper { float: left; width: 100%; } div.bodywrapper { margin: 0 0 0 230px; } div.body { background-color: #ffffff; color: #222222; padding: 0 20px 30px 20px; } div.footer { color: #ffffff; width: 100%; padding: 9px 0 9px 0; text-align: center; font-size: 75%; } div.footer a { color: #ffffff; text-decoration: underline; } div.related { background-color: #191a19; line-height: 30px; color: #ffffff; } div.related a { color: #ffffff; } div.sphinxsidebar { top: 30px; bottom: 60px; margin: 0; position: fixed; overflow: auto; height: auto; } div.sphinxsidebar h3 { font-family: 'Trebuchet MS', sans-serif; color: #3a3a3a; font-size: 1.4em; font-weight: normal; margin: 0; padding: 0; } div.sphinxsidebar h3 a { color: #3a3a3a; } div.sphinxsidebar h4 { font-family: 'Trebuchet MS', sans-serif; color: #3a3a3a; font-size: 1.3em; font-weight: normal; margin: 5px 0 0 0; padding: 0; } div.sphinxsidebar p { color: #3a3a3a; } div.sphinxsidebar p.topless { margin: 5px 10px 10px 10px; } div.sphinxsidebar ul { margin: 10px; padding: 0; color: #3a3a3a; } div.sphinxsidebar ul li { margin-top: .2em; } div.sphinxsidebar a { color: #3a8942; } div.sphinxsidebar input { border: 1px solid #3a8942; font-family: sans-serif; font-size: 1em; } /* -- body styles ----------------------------------------------------------- */ a { color: #355f7c; text-decoration: none; } a:hover { text-decoration: underline; } div.body p, div.body dd, div.body li { text-align: left; line-height: 130%; margin-top: 0px; margin-bottom: 0px; } div.body h1, div.body h2, div.body h3, div.body h4, div.body h5, div.body h6 { font-family: 'Trebuchet MS', sans-serif; background-color: #f2f2f2; font-weight: normal; color: #20435c; border-top: 2px solid #cccccc; border-bottom: 1px solid #cccccc; margin: 30px -20px 20px -20px; padding: 3px 0 3px 10px; } div.body h1 { margin-top: 0; font-size: 200%; } div.body h2 { font-size: 160%; } div.body h3 { font-size: 140%; padding-left: 20px; } div.body h4 { font-size: 120%; padding-left: 20px; } div.body h5 { font-size: 110%; padding-left: 20px; } div.body h6 { font-size: 100%; padding-left: 20px; } a.headerlink { color: #c60f0f; font-size: 0.8em; padding: 0 4px 0 4px; text-decoration: none; } a.headerlink:hover { background-color: #c60f0f; color: white; } div.body p, div.body dd, div.body li { text-align: left; line-height: 110%; } div.admonition p.admonition-title + p { display: inline; } div.note { background-color: #eee; border: 1px solid #ccc; } div.seealso { background-color: #ffc; border: 1px solid #ff6; } div.topic { background-color: #eee; } div.warning { background-color: #ffe4e4; border: 1px solid #f66; } p.admonition-title { display: inline; } p.admonition-title:after { content: ":"; } pre { padding: 0px; background-color: #ffffff; color: #000000; line-height: 120%; border: 0px solid #ffffff; border-left: none; border-right: none; white-space: pre-wrap; /* word-wrap: break-word; */ /* width:100px; */ } tt { background-color: #ecf0f3; padding: 0 1px 0 1px; font-size: 110%; } .warning tt { background: #efc2c2; } .note tt { background: #d6d6d6; } body { width:150%; }

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• .NET Code Evolution

  - by Alois Kraus

  Originally posted on: http://geekswithblogs.net/akraus1/archive/2013/07/24/153504.aspxAt my day job I do look at a lot of code written by other people. Most of the code is quite good and some is even a masterpiece. And there is also code which makes you think WTF… oh it was written by me. Hm not so bad after all. There are many excuses reasons for bad code. Most often it is time pressure followed by not enough ambition (who cares) or insufficient training. Normally I do care about code quality quite a lot which makes me a (perceived) slow worker who does write many tests and refines the code quite a lot because of the design deficiencies. Most of the deficiencies I do find by putting my design under stress while checking for invariants. It does also help a lot to step into the code with a debugger (sometimes also Windbg). I do this much more often when my tests are red. That way I do get a much better understanding what my code really does and not what I think it should be doing. This time I do want to show you how code can evolve over the years with different .NET Framework versions. Once there was  time where .NET 1.1 was new and many C++ programmers did switch over to get rid of not initialized pointers and memory leaks. There were also nice new data structures available such as the Hashtable which is fast lookup table with O(1) time complexity. All was good and much code was written since then. At 2005 a new version of the .NET Framework did arrive which did bring many new things like generics and new data structures. The “old” fashioned way of Hashtable were coming to an end and everyone used the new Dictionary<xx,xx> type instead which was type safe and faster because the object to type conversion (aka boxing) was no longer necessary. I think 95% of all Hashtables and dictionaries use string as key. Often it is convenient to ignore casing to make it easy to look up values which the user did enter. An often followed route is to convert the string to upper case before putting it into the Hashtable. Hashtable Table = new Hashtable(); void Add(string key, string value) { Table.Add(key.ToUpper(), value); } This is valid and working code but it has problems. First we can pass to the Hashtable a custom IEqualityComparer to do the string matching case insensitive. Second we can switch over to the now also old Dictionary type to become a little faster and we can keep the the original keys (not upper cased) in the dictionary. Dictionary<string, string> DictTable = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase); void AddDict(string key, string value) { DictTable.Add(key, value); } Many people do not user the other ctors of Dictionary because they do shy away from the overhead of writing their own comparer. They do not know that .NET has for strings already predefined comparers at hand which you can directly use. Today in the many core area we do use threads all over the place. Sometimes things break in subtle ways but most of the time it is sufficient to place a lock around the offender. Threading has become so mainstream that it may sound weird that in the year 2000 some guy got a huge incentive for the idea to reduce the time to process calibration data from 12 hours to 6 hours by using two threads on a dual core machine. Threading does make it easy to become faster at the expense of correctness. Correct and scalable multithreading can be arbitrarily hard to achieve depending on the problem you are trying to solve. Lets suppose we want to process millions of items with two threads and count the processed items processed by all threads. A typical beginners code might look like this: int Counter; void IJustLearnedToUseThreads() { var t1 = new Thread(ThreadWorkMethod); t1.Start(); var t2 = new Thread(ThreadWorkMethod); t2.Start(); t1.Join(); t2.Join(); if (Counter != 2 * Increments) throw new Exception("Hmm " + Counter + " != " + 2 * Increments); } const int Increments = 10 * 1000 * 1000; void ThreadWorkMethod() { for (int i = 0; i < Increments; i++) { Counter++; } } It does throw an exception with the message e.g. “Hmm 10.222.287 != 20.000.000” and does never finish. The code does fail because the assumption that Counter++ is an atomic operation is wrong. The ++ operator is just a shortcut for Counter = Counter + 1 This does involve reading the counter from a memory location into the CPU, incrementing value on the CPU and writing the new value back to the memory location. When we do look at the generated assembly code we will see only inc dword ptr [ecx+10h] which is only one instruction. Yes it is one instruction but it is not atomic. All modern CPUs have several layers of caches (L1,L2,L3) which try to hide the fact how slow actual main memory accesses are. Since cache is just another word for redundant copy it can happen that one CPU does read a value from main memory into the cache, modifies it and write it back to the main memory. The problem is that at least the L1 cache is not shared between CPUs so it can happen that one CPU does make changes to values which did change in meantime in the main memory. From the exception you can see we did increment the value 20 million times but half of the changes were lost because we did overwrite the already changed value from the other thread. This is a very common case and people do learn to protect their  data with proper locking.   void Intermediate() { var time = Stopwatch.StartNew(); Action acc = ThreadWorkMethod_Intermediate; var ar1 = acc.BeginInvoke(null, null); var ar2 = acc.BeginInvoke(null, null); ar1.AsyncWaitHandle.WaitOne(); ar2.AsyncWaitHandle.WaitOne(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Intermediate did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Intermediate() { for (int i = 0; i < Increments; i++) { lock (this) { Counter++; } } } This is better and does use the .NET Threadpool to get rid of manual thread management. It does give the expected result but it can result in deadlocks because you do lock on this. This is in general a bad idea since it can lead to deadlocks when other threads use your class instance as lock object. It is therefore recommended to create a private object as lock object to ensure that nobody else can lock your lock object. When you read more about threading you will read about lock free algorithms. They are nice and can improve performance quite a lot but you need to pay close attention to the CLR memory model. It does make quite weak guarantees in general but it can still work because your CPU architecture does give you more invariants than the CLR memory model. For a simple counter there is an easy lock free alternative present with the Interlocked class in .NET. As a general rule you should not try to write lock free algos since most likely you will fail to get it right on all CPU architectures. void Experienced() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); t1.Wait(); t2.Wait(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Experienced did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Experienced() { for (int i = 0; i < Increments; i++) { Interlocked.Increment(ref Counter); } } Since time does move forward we do not use threads explicitly anymore but the much nicer Task abstraction which was introduced with .NET 4 at 2010. It is educational to look at the generated assembly code. The Interlocked.Increment method must be called which does wondrous things right? Lets see: lock inc dword ptr [eax] The first thing to note that there is no method call at all. Why? Because the JIT compiler does know very well about CPU intrinsic functions. Atomic operations which do lock the memory bus to prevent other processors to read stale values are such things. Second: This is the same increment call prefixed with a lock instruction. The only reason for the existence of the Interlocked class is that the JIT compiler can compile it to the matching CPU intrinsic functions which can not only increment by one but can also do an add, exchange and a combined compare and exchange operation. But be warned that the correct usage of its methods can be tricky. If you try to be clever and look a the generated IL code and try to reason about its efficiency you will fail. Only the generated machine code counts. Is this the best code we can write? Perhaps. It is nice and clean. But can we make it any faster? Lets see how good we are doing currently. Level Time in s IJustLearnedToUseThreads Flawed Code Intermediate 1,5 (lock) Experienced 0,3 (Interlocked.Increment) Master 0,1 (1,0 for int[2]) That lock free thing is really a nice thing. But if you read more about CPU cache, cache coherency, false sharing you can do even better. int[] Counters = new int[12]; // Cache line size is 64 bytes on my machine with an 8 way associative cache try for yourself e.g. 64 on more modern CPUs void Master() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Master, 0); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Master, Counters.Length - 1); t1.Wait(); t2.Wait(); Counter = Counters[0] + Counters[Counters.Length - 1]; if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Master did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Master(object number) { int index = (int) number; for (int i = 0; i < Increments; i++) { Counters[index]++; } } The key insight here is to use for each core its own value. But if you simply use simply an integer array of two items, one for each core and add the items at the end you will be much slower than the lock free version (factor 3). Each CPU core has its own cache line size which is something in the range of 16-256 bytes. When you do access a value from one location the CPU does not only fetch one value from main memory but a complete cache line (e.g. 16 bytes). This means that you do not pay for the next 15 bytes when you access them. This can lead to dramatic performance improvements and non obvious code which is faster although it does have many more memory reads than another algorithm. So what have we done here? We have started with correct code but it was lacking knowledge how to use the .NET Base Class Libraries optimally. Then we did try to get fancy and used threads for the first time and failed. Our next try was better but it still had non obvious issues (lock object exposed to the outside). Knowledge has increased further and we have found a lock free version of our counter which is a nice and clean way which is a perfectly valid solution. The last example is only here to show you how you can get most out of threading by paying close attention to your used data structures and CPU cache coherency. Although we are working in a virtual execution environment in a high level language with automatic memory management it does pay off to know the details down to the assembly level. Only if you continue to learn and to dig deeper you can come up with solutions no one else was even considering. I have studied particle physics which does help at the digging deeper part. Have you ever tried to solve Quantum Chromodynamics equations? Compared to that the rest must be easy ;-). Although I am no longer working in the Science field I take pride in discovering non obvious things. This can be a very hard to find bug or a new way to restructure data to make something 10 times faster. Now I need to get some sleep ….

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• Hard disk with bad clusters

  - by Dan

  I have been trying to backup some files up to DVD recently, and the burn process failed saying the CRC check failed for certain files. I then tried to browse to these files in Windows explorer and my whole machine locks up and I have to reboot. I ran check disk without the '/F /R' arguments and it told me I had bad sectors. So I re-ran it with the arguments and check disk fails during the 'Chkdsk is verifying usn journal' stage with this error: Insufficient disk space to fix the usn journal $j data stream The hard disk is a 300GB Partition on a 400GB Disk, and there is 160GBs of free space on the partition. My os (Windows 7) is installed on the other partition and is running fine. Any idea how I fix this? or repair it enough to copy my files off it?

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• Project Server 2007 install issue - ProjectEventService won't start

  - by Brian Meinertz

  Trying to install PS2007 with SP1 on Server 2003. The install goes fine, but when running the SharePoint Configuration Wizard, it fails at stage 6 of 12 with the error: Failed to register SharePoint Services. An exception of type System.InvalidOperationException was thrown. Additional exception information: Cannot start service ProjectEventService on computer '.'. From the PSCDiagnostics log: Exception: System.InvalidOperationException: Cannot start service ProjectEventService on computer '.'. --- System.ComponentModel.Win32Exception: The service did not respond to the start or control request in a timely fashion. The ProjectEventService (Microsoft Office Project Server Event) won't even start manually using the Network Service account. Starting the service with a domain account works, but subsequently running the Config Wizard causes the service to be removed and re-provisioned to run using the Network Service account, which again fails. Presumably Network Service needs elevated permissions, but even adding it to the local Admin group makes no difference. Anyone come across this sort of issue before?

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• Cisco ASA 5510 ASDM: Setting up multiple public static ip addresses on a single interface and route

  - by ssjaken

  HI, i have a cisco ASA 5510 using ASDM version 6.3 We have a webserver that is been written very specifically and i was given super direct "DO NOT DEVIATE" directions. This server has to get traffic from 3 different PUBLIC ip's that we own. (our isp gave use a block of 12 static addresses) on 4 different ports. there are the directions i was given externalIP1:22 - 172.17.5.50:22 - SSH externalIP1:443 - 172.17.5.50:23040 - SIT externalIP2:443 - 172.17.5.50:33040 - STAGE externalIP3:443 - 172.17.5.50:43040 - PROD My first question is, using ASDM (my contract employer demands i use ASDM over CLI) how do i get three public addresses to work on one interface. We are authenticating on PPPoE. I know create a virtual interface with the static address but when i do i cannot ping the address from another offsite machine. secondly, where would i put the traffic redirect in. would i go ahead and create ACL's or just make NAT routes. Thanks.

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• How to connect to a SOCKS Proxy from an iPhone/iPod Touch?

  - by GeneQ

  I like to surf securely and privately via a SOCKS proxy which I created via SSH tunneling, on the Mac. I used the SSH client on my Mac to achieve this. Then I thought, since the iPhone OS is essentially Mac OS, the same trick might work also on the iPhone. I managed to create a SSh tunnel on my iPhone via the Terminal (iPhone's Terminal). (Yes, it's jail-broken) ssh -D [port] [email protected] At this stage my iPhone is SOCKS proxy. However, there doesn't seem to be a way in the iPhone networking preference panel to specify a SOCKS proxy. Someone suggest creating a Proxy Auto-Contig (PAC) file to workaround this, but that sounds complicated. Any ideas how to make iPhone use it's own SOCKS proxy?

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• How to sysprep SQL Server Express?

  - by Jim

  We plan to deploy Hyper-V VHD with Windows Server 2008 R2 and SQL Server 2012 Express installed to multiple hosts. From my understanding, the correct way to do this is to install SQL Server in prepartion mode, sysprep Windows, then complete SQL Server installation when the VHD is deployed. I mostly followed the process in this blog post: http://sethusrinivasan.com/category/sysprep/ However, after the VHD is deployed, I'm unable to complete the SQL Server installation. It keeps saying "Upgrade matrix is incorrect". It seems that it's trying to upgrade itself to Enterprise edition (I was asked for product key during install, but I skipped it). Could anyone share their experience in deploying VHDs with SQL Server (we're fine with either SQL Server 2008 R2 or 2012)? I think the source of my issue is because I can't select "Express Edition" when entering the product key at the completion stage, so the installation is trying to do an upgrade to Enterprise Edition. I have no idea why the drop down list is empty.

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• Parallel Desktops: installing Parallel Tools on Ubuntu

  - by Patrick

  hi, I get the following error when I try to install Parallel Tools on my Ubuntu in Parallel Desktop. I follow the istructions, running sh install from terminal: I follow the UI istructions and then the installation stops with this error message: E: Couldn't find package dkms Fri May 7 14:34:20 PDT 2010 Start installation or upgrade of Guest Tools Installed Guest Tools were not found Perform installation into the /usr/lib/parallels-tools directory cat: /usr/lib/parallels-tools/kmods/../version: No such file or directory Start installation of prl_eth kernel module make: Entering directory `/usr/lib/parallels-tools/kmods' cd prl_eth/pvmnet && make make[1]: Entering directory `/usr/lib/parallels-tools/kmods/prl_eth/pvmnet' make -C /lib/modules/2.6.32-21-generic/build M=/usr/lib/parallels-tools/kmods/prl_eth/pvmnet make[2]: Entering directory `/usr/src/linux-headers-2.6.32-21-generic' LD /usr/lib/parallels-tools/kmods/prl_eth/pvmnet/built-in.o CC [M] /usr/lib/parallels-tools/kmods/prl_eth/pvmnet/pvmnet.o LD [M] /usr/lib/parallels-tools/kmods/prl_eth/pvmnet/prl_eth.o Building modules, stage 2. MODPOST 1 modules WARNING: modpost: missing MODULE_LICENSE() in /usr/lib/parallels-tools/kmods/prl_eth/pvmnet/prl_eth.o thanks

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• Project Server 2007 install issue - ProjectEventService won't start

  - by Brian Meinertz

  Trying to install PS2007 with SP1 on Server 2003. The install goes fine, but when running the SharePoint Configuration Wizard, it fails at stage 6 of 12 with the error: Failed to register SharePoint Services. An exception of type System.InvalidOperationException was thrown. Additional exception information: Cannot start service ProjectEventService on computer '.'. From the PSCDiagnostics log: Exception: System.InvalidOperationException: Cannot start service ProjectEventService on computer '.'. --- System.ComponentModel.Win32Exception: The service did not respond to the start or control request in a timely fashion. The ProjectEventService (Microsoft Office Project Server Event) won't even start manually using the Network Service account. Starting the service with a domain account works, but subsequently running the Config Wizard causes the service to be removed and re-provisioned to run using the Network Service account, which again fails. Presumably Network Service needs elevated permissions, but even adding it to the local Admin group makes no difference. Anyone come across this sort of issue before?

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• replace laptop hard disk

  - by 5YrsLaterDBA

  I have bought a ACER Aspire 5736Z-4790 laptop for my parents. It just passed the warranty. I think the hard disk is bad now. I cannot open/copy some of my files. It will crash (blue screen) when I do chkdsk /f/r in the stage 4 of 5 which is verifying file data. I can hear a strange noise when it is reading the bad sectors (I guess because it hangs there.) I am thinking replace the hard disk. should I buy the same hard disk or any SATA laptop hard disk will be ok? BTW, is there a way to repair it (with software)?

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• /var/run/httpd.pid missing...

  - by user38043

  Recently one of our web servers httpd stopped working and I haven't been able to find the problem. Today I sat down and went through every directory in the httpd.conf and have found an issue. the /var/run/httpd.pid is missing from the folder. All other files are there and seem to be fine. I cannot create a new file with the same name in vi and I have no idea what could have caused this. I imagine it was caused by a cold reboot at some stage as no other extraordinary processes have been run on this server at the time it went down. I am running CentOS 3. How can I reinstate this file?

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• Using virt-install to mount multiple cdrom drives/images

  - by Dana the Sane

  I would like to create a windows xp guest from the windows xp upgrade cd I have, along with one of a few full versions I have around. However, when I reach the stage in the installer where I am prompted to insert a full version cd, the installer can't find it, i.e.: Setup could not read the CD you inserted, or the CD is not a valid Windows CD.. Is there a work-around for this?, my Googling didn't uncover anything. I've tried various combinations of mounting .iso files and specifying disks, such as: $sudo virt-install --accelerate --connect qemu:///system -n xpsp1 -r 2048 --disk ./vm/winxp_sp1.iso,device=cdrom --disk ./vm/windows.qcow2,size=12 --vnc --noautoconsole --os-type windows --os-variant winxp --vcpus 2 -c /dev/cdrom --check-cpu If I try to specify multiple cdrom drives, I receive an error: virt-install --accelerate --connect qemu:///system -n xpsp1 -r 2048 --disk ./vm/winxp_sp1.iso,device=cdrom --disk /dev/cdrom,device=cdrom --disk ./vm/windows.qcow2,size=12 --vnc --noautoconsole --os-type windows --os-variant winxp --vcpus 2 --check-cpu Starting install... ERROR IDE CDROM must use 'hdc', but target in use.

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• Strange error when Bootcamp attempts to create partition for Windows

  - by mozillalives

  I get a strange error when I tell Bootcamp to create a partition for Windows. I get to the Create a Partition stage. I select 20GB for Windows leaving 91GB (39GB free) for OS X. I then click Partition and it gives me the following error The disk cannot be partitioned because some files cannot be moved. Back up the disk and use Disk Utility to format it as a single Mac OS Extended (Journaled) volume. Restore your information to the disk and try using Boot Camp Assistant again. My disk is formatted in Mac OS Extended (Journaled), I have closed all applications (besides Bootcamp Assistant) and I have even restarted and tried again to see if that might help. Nothing. I can't get it to partition. I also tried to create the partition using Disk Utility and I got the following error Partition failed Partition failed with the error: Could not modify partition map because filesystem verification failed Any ideas? BTW - I am running OS X 10.6.2

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• Best practice for authenticating DMZ against AD in LAN

  - by Sergei

  We have few customer facing servers in DMZ that also have user accounts , all accounts are in shadow password file. I am trying to consolidate user logons and thinking about letting LAN users to authenticate against Active Directory.Services needing authentication are Apache, Proftpd and ssh. After consulting security team I have setup authentication DMZ that has LDAPS proxy that in turn contacts another LDAPS proxy (proxy2) in LAN and this one passes authentication info via LDAP (as LDAP bind) to AD controller.Second LDAP proxy only needed because AD server refuses speak TLS with our secure LDAP implemetation. This works for Apache using appropriate module.At a later stage I may try to move customer accounts from servers to LDAP proxy so they are not scattered around servers. For SSH I joined proxy2 to Windows domain so users can logon using their windows credentials.Then I created ssh keys and copied them to DMZ servers using ssh-copy, to enable passwordless logon once users are authenticated. Is this a good way to implement this kind of SSO?Did I miss any security issues here or maybe there is a better way ofachieving my goal?

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• What else is needed to get iptables to log into this file I created?

  - by anthony01

  I want to create the logging of iptables DROP's and intrusion attemps. First, I put --log-prefix "iptables: " at the end of every iptables rules in my iptables rules file. But this doesn't work, as it says there is a syntax error. So where should I put that command? (I would want to have it included in the saved rules file) Secondly, I created a file iptables.conf within /etc/rsyslog.d/, and I put the following inside of it: :msg, startswith, "iptables: " -/var/log/iptables.log & ~ I assume that at this stage, I'm supposed to restart the rsyslog daemon. What else is needed to do what I'm attempting? Thanks a lot

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• When to increase AWS RDS MySQL Server instance to larger CPU/RAM?

  - by rksprst

  I'm wondering at what stage do I need to increase the image for the RDS MySQL server to a larger CPU/RAM instance. The CPU utilization graph is near 0. The Avg Free Memory is around 150MB. The Avg Swap Usage is 420MB. Read Latency is 0-20ms/op it spikes up randomly. Avg write latency is on average 5ms/op but spikes up to 10-20ms/op. Are there some common rules here that I should follow? Thanks!

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• Roaming profile migration failed using Windows explorer manual copy

  - by Albert Widjaja

  Hi All, I'm at the final stage of migrating an old demoted DC server, now I'm stuck in migrating/copying the roaming profiles of the users from the old win2k server (oldServer1) into the new win2k3 server (newServer1) there are lots of profiles which points into the old server: \\oldServer1\profiles\user1 \\oldServer1\profiles\user2 \\oldServer1\profiles\user3 . . . \\oldServer1\profiles\userN in the ProfilePath I'd like to move it into: \\newServer1\profiles\user1 \\newServer1\profiles\user2 \\newServer1\profiles\user3 . . . \\newServer1\profiles\userN I tried to copy paste from my DOMAIN\Administrator account but it is failed to copy ? i cannot even browse inside the directory of user1 until userN ? is there any fastest way to do the copy process rather than "taking ownership" for each of those directory one by one ? [hopefully by taking ownership the user will still be able to use their profile normally] Thanks.

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• How to grow from single server setup

  - by Jenkz

  I'm looking for resources on how to grow our server setup. We currently have one dedicated server with Rackspace in the UK of the following spec: HPDL385_G2_PrevGen HP Single Dual Core Opteron 2214 (2.2Ghz) 4GB RAM 2x 10,000 SCSI Drives in RAID 1 Our traffic is up to 550,000 UVs per month. The site runs off a PHP and MySQL setup. The database gets an absolute hammering, we have many complex queries joining multilpe tables. We are using APC for PHP caching. I'm getting to the stage where I've done as much DB and query optimisation as I can and wonder what the next step should be...... I've looked at memcache, but I've got the impression that his requires a large amount of RAM and ideally a dedicated box.... So is the next step to have two boxes; one for database, one for Apache? Or is there a step I've overlooked. Our load is usually around the 2 mark, but right now it's up at 20!

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• How to grow from single server setup

  - by Jenkz

  I'm looking for resources on how to grow our server setup. We currently have one dedicated server with Rackspace in the UK of the following spec: HPDL385_G2_PrevGen HP Single Dual Core Opteron 2214 (2.2Ghz) 4GB RAM 2x 10,000 SCSI Drives in RAID 1 Our traffic is up to 550,000 UVs per month. The site runs off a PHP and MySQL setup. The database gets an absolute hammering, we have many complex queries joining multilpe tables. We are using APC for PHP caching. I'm getting to the stage where I've done as much DB and query optimisation as I can and wonder what the next step should be...... I've looked at memcache, but I've got the impression that his requires a large amount of RAM and ideally a dedicated box.... So is the next step to have two boxes; one for database, one for Apache? Or is there a step I've overlooked. Our load is usually around the 2 mark, but right now it's up at 20!

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• zfs rename/move root filesystem into child

  - by Anton

  Similar question exists but the solution (using mv) is awful because in this case it works as "copy, then remove" rather than pure "move". So, I created a pool: zpool create tank /dev/loop0 and rsynced my data from another storage in there directly so that my data is now in /tank. zfs list NAME USED AVAIL REFER MOUNTPOINT tank 591G 2.10T 591G /tank Now I've realized that I need my data to be in a child filesystem, not in /tank filesystem directly. So how do I move or rename the existing root filesystem so that it becomes a child within the pool? Simple rename won't work: zfs rename tank tank/mydata cannot rename to 'tank/mydata': datasets must be within same pool (Btw, why does it complain the datasets are not within same pool when if fact I only have one pool?) I know there are solutions that involve copying all the data (mv, or sending the whole dataset to another device and back), but shouldn't there be a simple elegant way? Just noting that I do not care of snapshots at this stage (there are none yet to care of).

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• Why does Windows run CHKDSK on every boot?

  - by khris

  Every time I turn on my PC, I get the following message: Checking file system on E: The type of the file systen is NTFS. One of your disks need to be checked for consistency. You may cancel the disk check, but it is strongly recommended that you continue. Windows will now check the disk. CHKDSK is verifying files (stage 1 of 3)... 0 percent completed I allow CHKDSK to to complete, but Windows does not load. This message appears every time I boot my computer. Could someone explain me why this message appears and what I should do to make it disappear?

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• __modver_version_show undefined error when building linux kernel 3.0.4 version

  - by Jie Liu

  I tried to build the linux kernel 3.0.4 on ubuntu 11.10 in virtualbox. Here are my steps: Download the source code tar xjvf linux-source-3.0.0.tar.bz2 cd linux-source-3.0.0 make menuconfig, changed nothing but used the default config and save to .config make Actually I think it should be 3.0.4 because from the Makefile I could see VERSION = 3 PATCHLEVEL = 0 SUBLEVEL = 4 EXTRAVERSION = Then at stage 2 which is to make modules, an error happened: ERROR: "__modver_version_show" [drivers/staging/rts5139/rts5139.ko] undefined! make[1]: *** [__modpost] Error 1 make: *** [modules] Error 2 Perhaps because 3.0.4 is a new release so that I can not find any same problem asked nor any solution to it.

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• Microsoft Robotics Studio in Ubuntu, with Wine ?

  - by Arkapravo

  I am using Ubuntu 9.10 and I am a bit of a robotics enthusiast. I have used KiKS (in MATLAB for simulating Khepera robots), MobotSim (in Windows, simulates a point like robot using a BASIC editor) and Player/Stage (with C/C++ on Ubuntu 9.04). My question, can MS Robotics Studio be installed in Ubuntu Linux using Wine (I am using 1.1.31) ? Has anyone done it ? Any other way to install MS Robotics Studio in Unix (Any flavour) ? Thanks for your reply !

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