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• Tomcat stops responding to JK requests

  - by Bruno Reis

  Hello. I have a nasty issue with load-balanced Tomcat servers that are hanging up. Any help would be greatly appreciated. The system I'm running Tomcat 6.0.26 on HotSpot Server 14.3-b01 (Java 1.6.0_17-b04) on three servers sitting behind another server that acts as load balancer. The load balancer runs Apache (2.2.8-1) + MOD_JK (1.2.25). All of the servers are running Ubuntu 8.04. The Tomcat's have 2 connectors configured: an AJP one, and a HTTP one. The AJP is to be used with the load balancer, while the HTTP is used by the dev team to directly connect to a chosen server (if we have a reason to do so). I have Lambda Probe 1.7b installed on the Tomcat servers to help me diagnose and fix the problem soon to be described. The problem Here's the problem: after about 1 day the application servers are up, JK Status Manager starts reporting status ERR for, say, Tomcat2. It will simply get stuck on this state, and the only fix I've found so far is to ssh the box and restart Tomcat. I must also mention that JK Status Manager takes a lot longer to refresh when there's a Tomcat server in this state. Finally, the "Busy" count of the stuck Tomcat on JK Status Manager is always high, and won't go down per se -- I must restart the Tomcat server, wait, then reset the worker on JK. Analysis Since I have 2 connectors on each Tomcat (AJP and HTTP), I still can connect to the application through the HTTP one. The application works just fine like this, very, very fast. That is perfectly normal, since I'm the only one using this server (as JK stopped delegating requests to this Tomcat). To try to better understand the problem, I've taken a thread dump from a Tomcat which is not responding anymore, and from another one that has been restarted recently (say, 1 hour before). The instance that is responding normally to JK shows most of the TP-ProcessorXXX threads in "Runnable" state, with the following stack trace: java.net.SocketInputStream.socketRead0 ( native code ) java.net.SocketInputStream.read ( SocketInputStream.java:129 ) java.io.BufferedInputStream.fill ( BufferedInputStream.java:218 ) java.io.BufferedInputStream.read1 ( BufferedInputStream.java:258 ) java.io.BufferedInputStream.read ( BufferedInputStream.java:317 ) org.apache.jk.common.ChannelSocket.read ( ChannelSocket.java:621 ) org.apache.jk.common.ChannelSocket.receive ( ChannelSocket.java:559 ) org.apache.jk.common.ChannelSocket.processConnection ( ChannelSocket.java:686 ) org.apache.jk.common.ChannelSocket$SocketConnection.runIt ( ChannelSocket.java:891 ) org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run ( ThreadPool.java:690 ) java.lang.Thread.run ( Thread.java:619 ) The instance that is stuck show most (all?) of the TP-ProcessorXXX threads in "Waiting" state. These have the following stack trace: java.lang.Object.wait ( native code ) java.lang.Object.wait ( Object.java:485 ) org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run ( ThreadPool.java:662 ) java.lang.Thread.run ( Thread.java:619 ) I don't know of the internals of Tomcat, but I would infer that the "Waiting" threads are simply threads sitting on a thread pool. So, if they are threads waiting inside of a thread pool, why wouldn't Tomcat put them to work on processing requests from JK? Solution? So, as I've stated before, the only fix I've found is to stop the Tomcat instance, stop the JK worker, wait the latter's busy count slowly go down, start Tomcat again, and enable the JK worker once again. What is causing this problem? How should I further investigate it? What can I do to solve it? Thanks in advance.

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• Dynamically sized UIWebView in a UITableViewCell with auto layout - constraint violation

  - by Orion Edwards

  I've got a UITableViewCell which contains a UIWebView. The table view cell adjusts it's height depending on the web view contents. I've got it all working fine, however when the view loads, I get a constraint violation exception in the debugger (the app continues running and functionally works fine, but I'd like to resolve this exception if possible). How I've got it set up: The TableView sets the cell height like this: -(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath { if(indexPath.section == 0) { [_topCell layoutIfNeeded]; CGFloat finalHeight = [_topCell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height; return finalHeight + 1; } The cell constraints are as follows: Arbitrary 7px offset from the cell's contentView (top) to the webView Web view has arbitrary fixed height constraint of 62px (will expand later once content loads) Arbitrary 8px offset from the webView to the cell's contentView (bottom) in my viewDidLoad, I tell the webView to go and load a URL, and in the webViewDidFinishLoad, I update the web view height constraint, like this -(void)webViewDidFinishLoad:(UIWebView *)webView { CGSize fittingSize = [webView sizeThatFits:CGSizeZero]; // fittingSize is approx 500 [self.tableView beginUpdates]; // Exceptions happen on the following line setting the constant _topCell.webViewHeightConstraint.constant = fittingSize.height; [_topCell layoutSubviews]; [self.tableView endUpdates]; } The exception looks like this: Unable to simultaneously satisfy constraints. Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) ( "<NSLayoutConstraint:0x10964b250 V:[webView(62)] (Names: webView:0x109664a00 )>", "<NSLayoutConstraint:0x109243d30 V:|-(7)-[webView] (Names: webView:0x109664a00, cellContent:0x1092436f0, '|':cellContent:0x1092436f0 )>", "<NSLayoutConstraint:0x109243f80 V:[webView]-(8)-| (Names: cellContent:0x1092436f0, webView:0x109664a00, '|':cellContent:0x1092436f0 )>", "<NSAutoresizingMaskLayoutConstraint:0x10967c210 h=--& v=--& V:[cellContent(78)] (Names: cellContent:0x1092436f0 )>" ) Will attempt to recover by breaking constraint <NSLayoutConstraint:0x10964b250 V:[webView(62)] (Names: webView:0x109664a00 )> This seems a bit weird. It's implied that the constraint which sets the height of the web view is going to be broken, however the web view does get it's height correctly set, and the tableview renders perfectly well. From my guesses, it looks like the newly increased web view height constraint (it's about 500px after the web view loads) is going to conflict with the <NSAutoresizingMaskLayoutConstraint:0x10967c210 h=--& v=--& V:[cellContent(78)] setting the cell height to 78 (put there by interface builder). This makes sense, however I don't want that cell content to have a fixed height of 78px, I want it to increase it's height, and functionally, it actually does this, just with these exceptions. I've tried setting _topCell.contentView.translatesAutoresizingMaskIntoConstraints = NO; to attempt to remove the NSAutoresizingMaskLayoutConstraint - this stops the exceptions, but then all the other layout is screwed up and the web view is about 10px high in the middle of the table view for no reason. I've also tried setting _topCell.contentView.autoresizingMask |= UIViewAutoresizingFlexibleHeight; in the viewDidLoad to hopefully affect the contentView 78px height constraint, but this has no effect Any help would be much appreciated

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• Blackjack game reshuffling problem

  - by Jam

  I am trying to make a blackjack game where before each new round, the program checks to make sure that the deck has 7 cards per player. And if it doesn't, the deck clears, repopulates, and reshuffles. I have most of the problem down, but for some reason at the start of every deal it reshuffles the deck more than once, and I can't figure out why. Help, please. Here's what I have so far: (P.S. the imported cards and games modules aren't part of the problem, I'm fairly sure my problem lies in the deal() function of my BJ_Deck class.) import cards, games class BJ_Card(cards.Card): """ A Blackjack Card. """ ACE_VALUE = 1 def get_value(self): if self.is_face_up: value = BJ_Card.RANKS.index(self.rank) + 1 if value > 10: value = 10 else: value = None return value value = property(get_value) class BJ_Deck(cards.Deck): """ A Blackjack Deck. """ def populate(self): for suit in BJ_Card.SUITS: for rank in BJ_Card.RANKS: self.cards.append(BJ_Card(rank, suit)) def deal(self, hands, per_hand=1): for rounds in range(per_hand): for hand in hands: if len(self.cards)>=7*(len(hands)): top_card=self.cards[0] self.give(top_card, hand) else: print "Reshuffling the deck." self.cards=[] self.populate() self.shuffle() top_card=self.cards[0] self.give(top_card, hand) class BJ_Hand(cards.Hand): """ A Blackjack Hand. """ def init(self, name): super(BJ_Hand, self).init() self.name = name def __str__(self): rep = self.name + ":\t" + super(BJ_Hand, self).__str__() if self.total: rep += "(" + str(self.total) + ")" return rep def get_total(self): # if a card in the hand has value of None, then total is None for card in self.cards: if not card.value: return None # add up card values, treat each Ace as 1 total = 0 for card in self.cards: total += card.value # determine if hand contains an Ace contains_ace = False for card in self.cards: if card.value == BJ_Card.ACE_VALUE: contains_ace = True # if hand contains Ace and total is low enough, treat Ace as 11 if contains_ace and total <= 11: # add only 10 since we've already added 1 for the Ace total += 10 return total total = property(get_total) def is_busted(self): return self.total > 21 class BJ_Player(BJ_Hand): """ A Blackjack Player. """ def is_hitting(self): response = games.ask_yes_no("\n" + self.name + ", do you want a hit? (Y/N): ") return response == "y" def bust(self): print self.name, "busts." self.lose() def lose(self): print self.name, "loses." def win(self): print self.name, "wins." def push(self): print self.name, "pushes." class BJ_Dealer(BJ_Hand): """ A Blackjack Dealer. """ def is_hitting(self): return self.total < 17 def bust(self): print self.name, "busts." def flip_first_card(self): first_card = self.cards[0] first_card.flip() class BJ_Game(object): """ A Blackjack Game. """ def init(self, names): self.players = [] for name in names: player = BJ_Player(name) self.players.append(player) self.dealer = BJ_Dealer("Dealer") self.deck = BJ_Deck() self.deck.populate() self.deck.shuffle() def get_still_playing(self): remaining = [] for player in self.players: if not player.is_busted(): remaining.append(player) return remaining # list of players still playing (not busted) this round still_playing = property(get_still_playing) def __additional_cards(self, player): while not player.is_busted() and player.is_hitting(): self.deck.deal([player]) print player if player.is_busted(): player.bust() def play(self): # deal initial 2 cards to everyone self.deck.deal(self.players + [self.dealer], per_hand = 2) self.dealer.flip_first_card() # hide dealer's first card for player in self.players: print player print self.dealer # deal additional cards to players for player in self.players: self.__additional_cards(player) self.dealer.flip_first_card() # reveal dealer's first if not self.still_playing: # since all players have busted, just show the dealer's hand print self.dealer else: # deal additional cards to dealer print self.dealer self.__additional_cards(self.dealer) if self.dealer.is_busted(): # everyone still playing wins for player in self.still_playing: player.win() else: # compare each player still playing to dealer for player in self.still_playing: if player.total > self.dealer.total: player.win() elif player.total < self.dealer.total: player.lose() else: player.push() # remove everyone's cards for player in self.players: player.clear() self.dealer.clear() def main(): print "\t\tWelcome to Blackjack!\n" names = [] number = games.ask_number("How many players? (1 - 7): ", low = 1, high = 8) for i in range(number): name = raw_input("Enter player name: ") names.append(name) print game = BJ_Game(names) again = None while again != "n": game.play() again = games.ask_yes_no("\nDo you want to play again?: ") main() raw_input("\n\nPress the enter key to exit.")

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• Win32: IProgressDialog will not disappear until you mouse over it.

  - by Ian Boyd

  i'm using the Win32 progress dialog. The damnest thing is that when i call: progressDialog.StopProgressDialog(); it doesn't disappear. It stays on screen until the user moves her mouse over it - then it suddenly disappers. The call to StopProgressDialog returns right away (i.e. it's not a synchronous call). i can prove this by doing things after the call has returned: private void button1_Click(object sender, EventArgs e) { //Force red background to prove we've started this.BackColor = Color.Red; this.Refresh(); //Start a progress dialog IProgressDialog pd = (IProgressDialog)new ProgressDialog(); pd.StartProgressDialog(this.Handle, null, PROGDLG.Normal, IntPtr.Zero); //The long running operation System.Threading.Thread.Sleep(10000); //Stop the progress dialog pd.SetLine(1, "Stopping Progress Dialog", false, IntPtr.Zero); pd.StopProgressDialog(); pd = null; //Return form to normal color to prove we've stopped. this.BackColor = SystemColors.Control; this.Refresh(); } The form: starts gray turns red to show we've stared turns back to gray color to show we've called stop So the call to StopProgressDialog has returned, except the progress dialog is still sitting there, mocking me, showing the message: Stopping Progress Dialog Doesn't Appear for 10 seconds Additionally, the progress dialog does not appear on screen until the System.Threading.Thread.Sleep(10000); ten second sleep is over. Not limited to .NET WinForms The same code also fails in Delphi, which is also an object wrapper around Window's windows: procedure TForm1.Button1Click(Sender: TObject); var pd: IProgressDialog; begin Self.Color := clRed; Self.Repaint; pd := CoProgressDialog.Create; pd.StartProgressDialog(Self.Handle, nil, PROGDLG_NORMAL, nil); Sleep(10000); pd.SetLine(1, StringToOleStr('Stopping Progress Dialog'), False, nil); pd.StopProgressDialog; pd := nil; Self.Color := clBtnFace; Self.Repaint; end; PreserveSig An exception would be thrown if StopProgressDialog was failing. Most of the methods in IProgressDialog, when translated into C# (or into Delphi), use the compiler's automatic mechanism of converting failed COM HRESULTS into a native language exception. In other words the following two signatures will throw an exception if the COM call returned an error HRESULT (i.e. a value less than zero): //C# void StopProgressDialog(); //Delphi procedure StopProgressDialog; safecall; Whereas the following lets you see the HRESULT's and react yourself: //C# [PreserveSig] int StopProgressDialog(); //Delphi function StopProgressDialog: HRESULT; stdcall; HRESULT is a 32-bit value. If the high-bit is set (or the value is negative) it is an error. i am using the former syntax. So if StopProgressDialog is returning an error it will be automatically converted to a language exception. Note: Just for SaG i used the [PreserveSig] syntax, the returned HRESULT is zero; MsgWait? The symptom is similar to what Raymond Chen described once, which has to do with the incorrect use of PeekMessage followed by MsgWaitForMultipleObjects: "Sometimes my program gets stuck and reports one fewer record than it should. I have to jiggle the mouse to get the value to update. After a while longer, it falls two behind, then three..." But that would mean that the failure is in IProgressDialog, since it fails equally well on CLR .NET WinForms and native Win32 code.

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• In Ruby, how to I read memory values from an external process?

  - by grg-n-sox

  So all I simply want to do is make a Ruby program that reads some values from known memory address in another process's virtual memory. Through my research and basic knowledge of hex editing a running process's x86 assembly in memory, I have found the base address and offsets for the values in memory I want. I do not want to change them; I just want to read them. I asked a developer of a memory editor how to approach this abstract of language and assuming a Windows platform. He told me the Win32API calls for OpenProcess, CreateProcess, ReadProcessMemory, and WriteProcessMemory were the way to go using either C or C++. I think that the way to go would be just using the Win32API class and mapping two instances of it; One for either OpenProcess or CreateProcess, depending on if the user already has th process running or not, and another instance will be mapped to ReadProcessMemory. I probably still need to find the function for getting the list of running processes so I know which running process is the one I want if it is running already. This would take some work to put all together, but I am figuring it wouldn't be too bad to code up. It is just a new area of programming for me since I have never worked this low level from a high level language (well, higher level than C anyways). I am just wondering of the ways to approach this. I could just use a bunch or Win32API calls, but that means having to deal with a bunch of string and array pack and unpacking that is system dependant I want to eventually make this work cross-platform since the process I am reading from is produced from an executable that has multiple platform builds, (I know the memory address changes from system to system. The idea is to have a flat file that contains all memory mappings so the Ruby program can just match the current platform environment to the matching memory mapping.) but from the looks of things I'll just have to make a class that wraps whatever is the current platform's system shared library memory related function calls. For all I know, there could already exist a Ruby gem that takes care of all of this for me that I am just not finding. I could also possibly try editing the executables for each build to make it so whenever the memory values I want to read from are written to by the process, it also writes a copy of the new value to a space in shared memory that I somehow have Ruby make an instance of a class that is a pointer under the hood to that shared memory address and somehow signal to the Ruby program that the value was updated and should be reloaded. Basically a interrupt based system would be nice, but since the purpose of reading these values is just to send to a scoreboard broadcasted from a central server, I could just stick to a polling based system that sends updates at fixed time intervals. I also could just abandon Ruby altogether and go for C or C++ but I do not know those nearly as well. I actually know more x86 than C++ and I only know C as far as system independent ANSI C and have never dealt with shared system libraries before. So is there a gem or lesser known module available that has already done this? If not, then any additional information as to how to accomplish this would be nice. I guess, long story short, how do I do all this? Thanks in advance, Grg PS: Also a confirmation that those Win32API calls should be aimed at the kernel32.dll library would be nice.

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• Can the STREAM and GUPS (single CPU) benchmark use non-local memory in NUMA machine

  - by osgx

  Hello I want to run some tests from HPCC, STREAM and GUPS. They will test memory bandwidth, latency, and throughput (in term of random accesses). Can I start Single CPU test STREAM or Single CPU GUPS on NUMA node with memory interleaving enabled? (Is it allowed by the rules of HPCC - High Performance Computing Challenge?) Usage of non-local memory can increase GUPS results, because it will increase 2- or 4- fold the number of memory banks, available for random accesses. (GUPS typically limited by nonideal memory-subsystem and by slow memory bank opening/closing. With more banks it can do update to one bank, while the other banks are opening/closing.) Thanks. UPDATE: (you may nor reorder the memory accesses that the program makes). But can compiler reorder loops nesting? E.g. hpcc/RandomAccess.c /* Perform updates to main table. The scalar equivalent is: * * u64Int ran; * ran = 1; * for (i=0; i<NUPDATE; i++) { * ran = (ran << 1) ^ (((s64Int) ran < 0) ? POLY : 0); * table[ran & (TableSize-1)] ^= stable[ran >> (64-LSTSIZE)]; * } */ for (j=0; j<128; j++) ran[j] = starts ((NUPDATE/128) * j); for (i=0; i<NUPDATE/128; i++) { /* #pragma ivdep */ for (j=0; j<128; j++) { ran[j] = (ran[j] << 1) ^ ((s64Int) ran[j] < 0 ? POLY : 0); Table[ran[j] & (TableSize-1)] ^= stable[ran[j] >> (64-LSTSIZE)]; } } The main loop here is for (i=0; i<NUPDATE/128; i++) { and the nested loop is for (j=0; j<128; j++) {. Using 'loop interchange' optimization, compiler can convert this code to for (j=0; j<128; j++) { for (i=0; i<NUPDATE/128; i++) { ran[j] = (ran[j] << 1) ^ ((s64Int) ran[j] < 0 ? POLY : 0); Table[ran[j] & (TableSize-1)] ^= stable[ran[j] >> (64-LSTSIZE)]; } } It can be done because this loop nest is perfect loop nest. Is such optimization prohibited by rules of HPCC?

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• Find optimal/good-enough strategy and AI for the game 'Proximity'?

  - by smci

  'Proximity' is a strategy game of territorial domination similar to Othello, Go and Risk. Two players, uses a 10x12 hex grid. Game invented by Brian Cable in 2007. Seems to be a worthy game for discussing a) optimal algorithm then b) how to build an AI. Strategies are going to be probabilistic or heuristic-based, due to the randomness factor, and the insane branching factor (20^120). So it will be kind of hard to compare objectively. A compute time limit of 5s per turn seems reasonable. Game: Flash version here and many copies elsewhere on the web Rules: here Object: to have control of the most armies after all tiles have been placed. Each turn you received a randomly numbered tile (value between 1 and 20 armies) to place on any vacant board space. If this tile is adjacent to any ally tiles, it will strengthen each tile's defenses +1 (up to a max value of 20). If it is adjacent to any enemy tiles, it will take control over them if its number is higher than the number on the enemy tile. Thoughts on strategy: Here are some initial thoughts; setting the computer AI to Expert will probably teach a lot: minimizing your perimeter seems to be a good strategy, to prevent flips and minimize worst-case damage like in Go, leaving holes inside your formation is lethal, only more so with the hex grid because you can lose armies on up to 6 squares in one move low-numbered tiles are a liability, so place them away from your main territory, near the board edges and scattered. You can also use low-numbered tiles to plug holes in your formation, or make small gains along the perimeter which the opponent will not tend to bother attacking. a triangle formation of three pieces is strong since they mutually reinforce, and also reduce the perimeter Each tile can be flipped at most 6 times, i.e. when its neighbor tiles are occupied. Control of a formation can flow back and forth. Sometimes you lose part of a formation and plug any holes to render that part of the board 'dead' and lock in your territory/ prevent further losses. Low-numbered tiles are obvious-but-low-valued liabilities, but high-numbered tiles can be bigger liabilities if they get flipped (which is harder). One lucky play with a 20-army tile can cause a swing of 200 (from +100 to -100 armies). So tile placement will have both offensive and defensive considerations. Comment 1,2,4 seem to resemble a minimax strategy where we minimize the maximum expected possible loss (modified by some probabilistic consideration of the value ß the opponent can get from 1..20 i.e. a structure which can only be flipped by a ß=20 tile is 'nearly impregnable'.) I'm not clear what the implications of comments 3,5,6 are for optimal strategy. Interested in comments from Go, Chess or Othello players. (The sequel ProximityHD for XBox Live, allows 4-player -cooperative or -competitive local multiplayer increases the branching factor since you now have 5 tiles in your hand at any given time, of which you can only play one. Reinforcement of ally tiles is increased to +2 per ally.)

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• copying link id to an input field

  - by zurna

  The code works fine when links are images. But I have a problem when there are flash movies. Another page opens with undefined in the address bar when it needs to copy the link id to imagesID input box. <script type="text/javascript"> var $input = $("#imagesID"); // <-- your input field $('a.thumb').click(function() { var value = $input.val(); var id = $(this).attr('id'); if (value.match(id)) { value = value.replace(id + ';', ''); } else { value += id + ';'; } $input.val(value); }); </script> <ul class="thumbs"> <li> <a class="thumb" id="62"> <img src="/FLPM/media/images/2A9L1V2X_sm.jpg" alt="Dock" id="62" class="floatLeft" /> </a> <br /> <a href="?Process=&IMAGEID=62" class="thumb"><span class="floatLeft">DELETE</span></a> </li> <li> <a class="thumb" id="61"> <img src="/FLPM/media/images/0E7Q9Z0C_sm.jpg" alt="Desert Landscape" id="61" class="floatLeft" /> </a> <br /> <a href="?Process=&IMAGEID=61" class="thumb"><span class="floatLeft">DELETE</span></a> </li> <li> <a class="thumb" id="60"> <img src="/FLPM/media/images/8R5D7M8O_sm.jpg" alt="Creek" id="60" class="floatLeft" /> </a> <br /> <a href="?Process=&IMAGEID=60" class="thumb"><span class="floatLeft">DELETE</span></a> </li> <li> <a class="thumb" id="59"> <object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://active.macromedia.com/flash4/cabs/swflash.cab#version=4,0,0,0" id="59" width="150" height="100" style="float:left; border:5px solid #CCCCCC; margin:5px 10px 10px 0;"> <param name="scale" value="exactfit"> <param name="AllowScriptAccess" value="always" /> <embed name="name" src="http://www.refinethetaste.com/FLPM/media/flashes/7P4A6K7M.swf" quality="high" scale="exactfit" width="150" height="100" type="application/x-shockwave-flash" AllowScriptAccess="always" pluginspage="http://www.macromedia.com/shockwave/download/index.cgi? P1_Prod_Version=ShockwaveFlash"> </embed> </object> </a> <br /> <a href="?Process=&IMAGEID=59" class="thumb"><span class="floatLeft">DELETE</span></a> </li> </ul>

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• How to directly rotate CVImageBuffer image in IOS 4 without converting to UIImage?

  - by Ian Charnas

  I am using OpenCV 2.2 on the iPhone to detect faces. I'm using the IOS 4's AVCaptureSession to get access to the camera stream, as seen in the code that follows. My challenge is that the video frames come in as CVBufferRef (pointers to CVImageBuffer) objects, and they come in oriented as a landscape, 480px wide by 300px high. This is fine if you are holding the phone sideways, but when the phone is held in the upright position I want to rotate these frames 90 degrees clockwise so that OpenCV can find the faces correctly. I could convert the CVBufferRef to a CGImage, then to a UIImage, and then rotate, as this person is doing: Rotate CGImage taken from video frame However that wastes a lot of CPU. I'm looking for a faster way to rotate the images coming in, ideally using the GPU to do this processing if possible. Any ideas? Ian Code Sample: -(void) startCameraCapture { // Start up the face detector faceDetector = [[FaceDetector alloc] initWithCascade:@"haarcascade_frontalface_alt2" withFileExtension:@"xml"]; // Create the AVCapture Session session = [[AVCaptureSession alloc] init]; // create a preview layer to show the output from the camera AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session]; previewLayer.frame = previewView.frame; previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill; [previewView.layer addSublayer:previewLayer]; // Get the default camera device AVCaptureDevice* camera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]; // Create a AVCaptureInput with the camera device NSError *error=nil; AVCaptureInput* cameraInput = [[AVCaptureDeviceInput alloc] initWithDevice:camera error:&error]; if (cameraInput == nil) { NSLog(@"Error to create camera capture:%@",error); } // Set the output AVCaptureVideoDataOutput* videoOutput = [[AVCaptureVideoDataOutput alloc] init]; videoOutput.alwaysDiscardsLateVideoFrames = YES; // create a queue besides the main thread queue to run the capture on dispatch_queue_t captureQueue = dispatch_queue_create("catpureQueue", NULL); // setup our delegate [videoOutput setSampleBufferDelegate:self queue:captureQueue]; // release the queue. I still don't entirely understand why we're releasing it here, // but the code examples I've found indicate this is the right thing. Hmm... dispatch_release(captureQueue); // configure the pixel format videoOutput.videoSettings = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA], (id)kCVPixelBufferPixelFormatTypeKey, nil]; // and the size of the frames we want // try AVCaptureSessionPresetLow if this is too slow... [session setSessionPreset:AVCaptureSessionPresetMedium]; // If you wish to cap the frame rate to a known value, such as 10 fps, set // minFrameDuration. videoOutput.minFrameDuration = CMTimeMake(1, 10); // Add the input and output [session addInput:cameraInput]; [session addOutput:videoOutput]; // Start the session [session startRunning]; } - (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection { // only run if we're not already processing an image if (!faceDetector.imageNeedsProcessing) { // Get CVImage from sample buffer CVImageBufferRef cvImage = CMSampleBufferGetImageBuffer(sampleBuffer); // Send the CVImage to the FaceDetector for later processing [faceDetector setImageFromCVPixelBufferRef:cvImage]; // Trigger the image processing on the main thread [self performSelectorOnMainThread:@selector(processImage) withObject:nil waitUntilDone:NO]; } }

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• Windows NT Service shutdown issues

  - by Jeremiah Gowdy

  I have developed middleware that provides RPC functionality to multiple client applications on multiple platforms within our organization. The middleware is written in C# and runs as a Windows NT Service. It handles things like file access to network shares, database access, etc. The middleware is hosted on two high end systems running Windows Server 2008 R2. When one of our server administrators goes to reboot the machine, primarily to do Windows Updates, there are serious problems with how the system behaves in regards to my NT Service. My service is designed to immediately stop listening for new connections, immediately start refusing new requests on existing connections, and otherwise shut down as rapidly as possible in the case of an OnStop or OnShutdown request from the SCM. Still, to maintain system integrity, operations that are currently in progress are allowed to continue for a reasonable time. Usually the server shuts down inside of 30 seconds (when the service is manually stopped for example). However, when the system is instructed to restart, my service immediately loses access to network drives and UNC paths, causing data integrity problems for any open files and partial writes to those locations. My service does list Workstation (and thus SMB Redirector) as a dependency, so I would think that my service would need to be stopped prior to Workstation/Redirector being stopped if Windows were honoring those dependencies. Basically, my application is forced to crash and burn, failing remote procedure calls and eventually being forced to terminate by the operating system after a timeout period has elapsed (seems to be on the order of 20-30 seconds). Unlike a Windows application, my Windows NT Service doesn't seem to have any power to stop a system shutdown in progress, delay the system shutdown, or even just the opportunity to save out any pending network share disk writes before being forcibly disconnected and shutdown. How is an NT Service developer supposed to have any kind of application integrity in this environment? Why is it that Forms Applications get all of the opportunity to finish their business prior to shutdown, while services seem to get no such benefits? I have tried: Calling SetProcessShutdownParameters via p/invoke to try to notify my application of the shutdown sooner to avoid Redirector shutting down before I do. Calling ServiceBase.RequestAdditionalTime with a value less than or equal to the two minute limit. Tweaking the WaitToKillServiceTimeout Everything I can think of to make my service shutdown faster. But in the end, I still get ~30 seconds of problematic time in which my service doesn't even seem to have been notified of an OnShutdown event yet, but requests are failing due to redirector no longer servicing my network share requests. How is this issue meant to be resolved? What can I do to delay or stop the shutdown, or at least be allowed to shut down my active tasks without Redirector services disappearing out from under me? I can understand what Microsoft is trying to do to prevent services from dragging their feet and showing shutdowns, but that seems like a great goal for Windows client operating systems, not for servers. I don't want my servers to shutdown fast, I want operational integrity and graceful shutdowns. Thanks in advance for any help you can provide. PS in regards to writing my own middleware, this is for a telephony application with sub-second "soft-realtime" response time requirements. It does make sense, and it's not a point I'm looking to debate. :)

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• How to resolve CGDirectDisplayID changing issues on newer multi-GPU Apple laptops in Core Foundation

  - by Dave Gallagher

  In Mac OS X, every display gets a unique CGDirectDisplayID number assigned to it. You can use CGGetActiveDisplayList() or [NSScreen screens] to access them, among others. Per Apple's docs: A display ID can persist across processes and system reboot, and typically remains constant as long as certain display parameters do not change. On newer mid-2010 MacBook Pro's, Apple started using auto-switching Intel/nVidia graphics. Laptops have two GPU's, a low-powered Intel, and a high-powered nVidia. Previous dual-GPU laptops (2009 models) didn't have auto-GPU switching, and required the user to make a settings change, logoff, and then logon again to make a GPU switch occur. Even older systems only had one GPU. There's an issue with the mid-2010 models where CGDirectDisplayID's don't remain the same when a display switches from one GPU to the next. For example: Laptop powers on. Built-In LCD Screen is driven by Intel chipset. Display ID: 30002 External Display is plugged in. Built-In LCD Screen switches to nVidia chipset. It's display ID changes: 30004 External Display is driven by nVidia chipset. ...at this point, the Intel chipset is dormant... User unplugs External Display. Built-In LCD Screen switches back to Intel chipset. It's display ID changes back to original: 30002 My question is, how can I match an old display ID to a new display ID when they alter due to a GPU change? Thought about: I've noticed that the display ID only changes by 2, but I don't have enough test Mac's available to determine if this is common to all new MacBook Pro's, or just mine. Kind of a kludge if "just check for display ID's which are +/-2 from one another" works, anyway. Tried: CGDisplayRegisterReconfigurationCallback(), which notifies before-and-after when displays are going to change, has no matching logic. Putting something like this inside a method registered with it doesn't work: // Run before display settings change: CGDirectDisplayID directDisplayID = ...; io_service_t servicePort = CGDisplayIOServicePort(directDisplayID); CFDictionaryRef oldInfoDict = IODisplayCreateInfoDictionary(servicePort, kIODisplayMatchingInfo); // ...display settings change... // Run after display settings change: CGDirectDisplayID directDisplayID = ...; io_service_t servicePort = CGDisplayIOServicePort(directDisplayID); CFDictionaryRef newInfoDict = IODisplayCreateInfoDictionary(servicePort, kIODisplayMatchingInfo); BOOL match = IODisplayMatchDictionaries(oldInfoDict, newInfoDict, 0); if (match) NSLog(@"Displays are a match"); else NSLog(@"Displays are not a match"); What's happening above is I'm caching oldInfoDict before display settings change, letting them change, and then comparing it to newInfoDict by using IODisplayMatchDictionaries(), which will say either "yes, both displays are the same!" or "no, both displays are not the same." Unfortunately, it does not return YES if GPU's have changed for a monitor. Example of the dictionary's it's comparing: // oldInfoDict (Display ID: 30002) oldInfoDict: { DisplayProductID = 40144; DisplayVendorID = 1552; IODisplayLocation = "IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/IGPU@2/AppleIntelFramebuffer/display0/AppleBacklightDisplay"; } // newInfoDict (Display ID: 30004) newInfoDict: { DisplayProductID = 40144; DisplayVendorID = 1552; IODisplayLocation = "IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/P0P2@1/IOPCI2PCIBridge/GFX0@0/NVDA,Display-A@0/NVDA/display0/AppleBacklightDisplay"; } As you can see, the IODisplayLocation key changes when GPU's are switched, hence IODisplayMatchDictionaries() doesn't work. I can, theoretically, compared just the DisplayProductID and DisplayVendorID keys, but I'm writing end-user software, and am worried of a situation where users have two or more identical monitors plugged in. Any help is greatly appreciated! :)

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• Two UIViews, one UIViewController (in one UINavigationController)

  - by jdandrea

  Given an iPhone app with a UITableViewController pushed onto a UINavigationController, I would like to add a right bar button item to toggle between the table view and an "alternate" view of the same data. Let's also say that this other view uses the same data but is not a UITableView. Now, I know variations on this question already exist on Stack Overflow. However, in this case, that alternate view would not be pushed onto the UINavigationController. It would be visually akin to flipping the current UIViewController's table view over and revealing the other view, then being able to flip back. In other words, it's intended to take up a single spot in the UINavigationController hierarchy. Moreover, whatever selection you ultimately make from within either view will push a common UIViewController onto the UINavigationController stack. Still more info: We don't want to use a separate UINavigationController just to handle this pair of views, and we don't want to split these apart via a UITabBarController either. Visually and contextually, the UX is meant to show two sides of the same coin. It's just that those two sides happen to involve their own View Controllers in normal practice. Now … it turns out I have already gone and quickly set this up to see how it might work! However, upon stepping back to examine it, I get the distinct impression that I went about it in a rather non-MVC way, which of course concerns me a bit. Here's what I did at a high level. Right now, I have a UIViewController (not a UITableViewController) that handles all commonalities between the two views, such as fetching the raw data. I also have two NIBs, one for each view, and two UIView objects to go along with them. (One of them is a UITableView, which is a kind of UIView.) I switch between the views using animation (easy enough). Also, in an effort to keep things encapsulated, the now-split-apart UITableView (not the UIViewController!) acts as its own delegate and data source, fetching data from the VC. The VC is set up as a weak, non-retained object in the table view. In parallel, the alternate view gets at the raw data from the VC in the exact same way. So, there are a few things that smell funny here. The weak linking from child to parent, while polite, seems like it might be wrong. Making a UITableView the table's data source and delegate also seems odd to me, thinking that a view controller is where you want to put that per Apple's MVC diagrams. As it stands now, it would appear as if the view knows about the model, which isn't good. Loading up both views in advance also seems odd, because lazy loading is no longer in effect. Losing the benefits of a UITableViewController (like auto-scrolling to cells with text fields) is also a bit frustrating, and I'd rather not reinvent the wheel to work around that as well. Given all of the above, and given we want that "flip effect" in the context of a single spot on a single UINavigationController, and given that both views are two sides of the same coin, is there a better, more obvious way to design this that I'm just happening to miss completely? Clues appreciated!

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• DSP - Problems using the inverse Fast Fourier Transform

  - by Trap

  I've been playing around a little with the Exocortex implementation of the FFT, but I'm having some problems. First, after calculating the inverse FFT of an unchanged frequency spectrum obtained by a previous forward FFT, one would expect to get the original signal back, but this is not the case. I had to figure out that I needed to scale the FFT output to about 1 / fftLength to get the amplitudes ok. Why is this? Second, whenever I modify the amplitudes of the frequency bins before calling the iFFT the signal gets distorted at low frequencies. However, this does not happen if I attenuate all the bins by the same factor. Let me put a very simplified example of the output buffer of a 4-sample FFT: // Bin 0 (DC) FFTOut[0] = 0.0000610351563 FFTOut[1] = 0.0 // Bin 1 FFTOut[2] = 0.000331878662 FFTOut[3] = 0.000629425049 // Central bin FFTOut[4] = -0.0000381469727 FFTOut[5] = 0.0 // Bin 3, this is a negative frequency bin. FFTOut[6] = 0.000331878662 FFTOut[7] = -0.000629425049 The output is composed of pairs of floats, each representing the real and imaginay parts of a single bin. So, bin 0 (array indexes 0, 1) would represent the real and imaginary parts of the DC frequency. As you can see, bins 1 and 3 both have the same values, (except for the sign of the Im part), so I guess these are the negative frequency values, and finally indexes (4, 5) would be the central frequency bin. To attenuate the frequency bin 1 this is what I do: // Attenuate the 'positive' bin FFTOut[2] *= 0.5; FFTOut[3] *= 0.5; // Attenuate its corresponding negative bin. FFTOut[6] *= 0.5; FFTOut[7] *= 0.5; For the actual tests I'm using a 1024-length FFT and I always provide all the samples so no 0-padding is needed. // Attenuate var halfSize = fftWindowLength / 2; float leftFreq = 0f; float rightFreq = 22050f; for( var c = 1; c < halfSize; c++ ) { var freq = c * (44100d / halfSize); // Calc. positive and negative frequency locations. var k = c * 2; var nk = (fftWindowLength - c) * 2; // This kind of attenuation corresponds to a high-pass filter. // The attenuation at the transition band is linearly applied, could // this be the cause of the distortion of low frequencies? var attn = (freq < leftFreq) ? 0 : (freq < rightFreq) ? ((freq - leftFreq) / (rightFreq - leftFreq)) : 1; mFFTOut[ k ] *= (float)attn; mFFTOut[ k + 1 ] *= (float)attn; mFFTOut[ nk ] *= (float)attn; mFFTOut[ nk + 1 ] *= (float)attn; } Obviously I'm doing something wrong but can't figure out what or where.

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• How do you stop scripters from slamming your website hundreds of times a second?

  - by davebug

  [update] I've accepted an answer, as lc deserves the bounty due to the well thought-out answer, but sadly, I believe we're stuck with our original worst case scenario: CAPTCHA everyone on purchase attempts of the crap. Short explanation: caching / web farms make it impossible for us to actually track hits, and any workaround (sending a non-cached web-beacon, writing to a unified table, etc.) slows the site down worse than the bots would. There is likely some pricey bit of hardware from Cisco or the like that can help at a high level, but it's hard to justify the cost if CAPTCHAing everyone is an alternative. I'll attempt to do a more full explanation in here later, as well as cleaning this up for future searchers (though others are welcome to try, as it's community wiki). I've added bounty to this question and attempted to explain why the current answers don't fit our needs. First, though, thanks to all of you who have thought about this, it's amazing to have this collective intelligence to help work through seemingly impossible problems. I'll be a little more clear than I was before: This is about the bag o' crap sales on woot.com. I'm the president of Woot Workshop, the subsidiary of Woot that does the design, writes the product descriptions, podcasts, blog posts, and moderates the forums. I work in the css/html world and am only barely familiar with the rest of the developer world. I work closely with the developers and have talked through all of the answers here (and many other ideas we've had). Usability of the site is a massive part of my job, and making the site exciting and fun is most of the rest of it. That's where the three goals below derive. CAPTCHA harms usability, and bots steal the fun and excitement out of our crap sales. To set up the scenario a little more, bots are slamming our front page tens of times a second screenscraping (and/or scanning our rss) for the Random Crap sale. The moment they see that, it triggers a second stage of the program that logs in, clicks I want One, fills out the form, and buys the crap. In current (2/6/2009) order of votes: lc: On stackoverflow and other sites that use this method, they're almost always dealing with authenticated (logged in) users, because the task being attempted requires that. On Woot, anonymous (non-logged) users can view our home page. In other words, the slamming bots can be non-authenticated (and essentially non-trackable except by IP address). So we're back to scanning for IPs, which a) is fairly useless in this age of cloud networking and spambot zombies and b) catches too many innocents given the number of businesses that come from one IP address (not to mention the issues with non-static IP ISPs and potential performance hits to trying to track this). Oh, and having people call us would be the worst possible scenario. Can we have them call you? BradC Ned Batchelder's methods look pretty cool, but they're pretty firmly designed to defeat bots built for a network of sites. Our problem is bots are built specifically to defeat our site. Some of these methods could likely work for a short time until the scripters evolved their bots to ignore the honeypot, screenscrape for nearby label names instead of form ids, and use a javascript-capable browser control. lc again "Unless, of course, the hype is part of you

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• Code golf: Word frequency chart

  - by ChristopheD

  The challenge: Build an ASCII chart of the most commonly used words in a given text. The rules: Only accept a-z and A-Z (alphabetic characters) as part of a word. Ignore casing (She == she for our purpose). Ignore the following words (quite arbitary, I know): the, and, of, to, a, i, it, in, or, is Clarification: considering don't: this would be taken as 2 different 'words' in the ranges a-z and A-Z: (don and t). Optionally (it's too late to be formally changing the specifications now) you may choose to drop all single-letter 'words' (this could potentially make for a shortening of the ignore list too). Parse a given text (read a file specified via command line arguments or piped in; presume us-ascii) and build us a word frequency chart with the following characteristics: Display the chart (also see the example below) for the 22 most common words (ordered by descending frequency). The bar width represents the number of occurences (frequency) of the word (proportionally). Append one space and print the word. Make sure these bars (plus space-word-space) always fit: bar + [space] + word + [space] should be always <= 80 characters (make sure you account for possible differing bar and word lenghts: e.g.: the second most common word could be a lot longer then the first while not differing so much in frequency). Maximize bar width within these constraints and scale the bars appropriately (according to the frequencies they represent). An example: The text for the example can be found here (Alice's Adventures in Wonderland, by Lewis Carroll). This specific text would yield the following chart: _________________________________________________________________________ |_________________________________________________________________________| she |_______________________________________________________________| you |____________________________________________________________| said |____________________________________________________| alice |______________________________________________| was |__________________________________________| that |___________________________________| as |_______________________________| her |____________________________| with |____________________________| at |___________________________| s |___________________________| t |_________________________| on |_________________________| all |______________________| this |______________________| for |______________________| had |_____________________| but |____________________| be |____________________| not |___________________| they |__________________| so For your information: these are the frequencies the above chart is built upon: [('she', 553), ('you', 481), ('said', 462), ('alice', 403), ('was', 358), ('that ', 330), ('as', 274), ('her', 248), ('with', 227), ('at', 227), ('s', 219), ('t' , 218), ('on', 204), ('all', 200), ('this', 181), ('for', 179), ('had', 178), (' but', 175), ('be', 167), ('not', 166), ('they', 155), ('so', 152)] A second example (to check if you implemented the complete spec): Replace every occurence of you in the linked Alice in Wonderland file with superlongstringstring: ________________________________________________________________ |________________________________________________________________| she |_______________________________________________________| superlongstringstring |_____________________________________________________| said |______________________________________________| alice |________________________________________| was |_____________________________________| that |______________________________| as |___________________________| her |_________________________| with |_________________________| at |________________________| s |________________________| t |______________________| on |_____________________| all |___________________| this |___________________| for |___________________| had |__________________| but |_________________| be |_________________| not |________________| they |________________| so The winner: Shortest solution (by character count, per language). Have fun! Edit: Table summarizing the results so far (2012-02-15) (originally added by user Nas Banov): Language Relaxed Strict ========= ======= ====== GolfScript 130 143 Perl 185 Windows PowerShell 148 199 Mathematica 199 Ruby 185 205 Unix Toolchain 194 228 Python 183 243 Clojure 282 Scala 311 Haskell 333 Awk 336 R 298 Javascript 304 354 Groovy 321 Matlab 404 C# 422 Smalltalk 386 PHP 450 F# 452 TSQL 483 507 The numbers represent the length of the shortest solution in a specific language. "Strict" refers to a solution that implements the spec completely (draws |____| bars, closes the first bar on top with a ____ line, accounts for the possibility of long words with high frequency etc). "Relaxed" means some liberties were taken to shorten to solution. Only solutions shorter then 500 characters are included. The list of languages is sorted by the length of the 'strict' solution. 'Unix Toolchain' is used to signify various solutions that use traditional *nix shell plus a mix of tools (like grep, tr, sort, uniq, head, perl, awk).

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• My server app works strangely. What could be the reason(s)?

  - by Poni

  Hi! I've written a server app (two parts actually; proxy server and a game server) using C++ (board game). It uses IOCP as the sockets interface. For that app I've also written a "client simulator" (hereafter "client") app that spawns many client connections, where each of them plays, in very high speed, getting the CPU to be 100% utilized. So, that's how it goes in terms of topology: Game server - holds the game state. Real players do not connect it directly but through the proxy server. When a player joins a game, the proxy actually asks for it on behalf of that player, and the game server spawns a "player instance" for that player, and from now on, every notification between the game server and the player is being passed through the proxy. Proxy server - holds TCP connections with the real players. Players communicate with the game server through it only. Client simulator - connects to the proxy only. When running the server (again, it's actually two server apps) & client locally it all works just fine. I'm talking about 40k+ player instances in which all of them are active in a game. On the other hand, when running the server remotely with, say, 1000 clients who play things getting strange. For example, I run it as said above. Then with Task Manager I kill the client simulator app ("End Process Tree"). Then it seems like the buffer of the remote server got modified by another thread, or in other words, a memory corruption has been occurred. The server crashes because it got an unknown message id (it's a custom protocol where each message has it's own unique number). To make things clear, here is how I run the apps: PC1 - game server and clients simulator (because the clients will connect the proxy). PC2 - proxy server. The strangest thing is this: Only the remote side gets "corrupted". Remote in terms that it's not the PC I use to code the app (VC++ 2008). Let's call the PC I use to code the apps "PC1". Now for example, if this time I ran the game server on PC1 (it means that proxy server on PC2 and clients simulator on PC1), then the proxy server crashes with an "unknown message id" error. Another variation is when I run the proxy server on PC1 (again, the dev machine), the game server and the clients simulator on PC2, then the game server on PC2 gets crashed. As for the IOCP config: The servers' internal connections use the default receive/send buffer sizes. Tried even with setting them to 1MB, but no luck. I have three PCs in total; 2 x Vista 64bit <<-- one of those is the dev machine. The other is connected through WiFi. 1 x WinXP 32bit They're all connected in a "full duplex" manner. What could be the reason? Tried about everything; Stack tracing, recording some actions (like read/write logging).. I want to stress that only the PC I'm not using to code the apps crashes (actually the server app "role" which is running on it - sometimes the game server and sometimes the proxy server). At first I thought that maybe the wireless PC has problems (it's wireless..) but: TCP has it's own mechanisms to make sure the packet is delivered properly. Also, a crash also happens when trying it with the two PCs that are physically connected (Vista vs. XP). Another option is that the Windows DLLs versions might have problems, but then again, one of the tests is Vista vs. Vista, and the other is Vista vs. XP. Any idea?

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• surfaceDestroyed called out of turn

  - by Avasulthiris

  I'm currently developing on minimum sdk version 3 (Android 1.5 - cupcake) and I'm having a strange unexplained issue that I have not been able to solve on my own. It is now becoming a rather urgent issue as I've already missed 1 deadline... I'm writing a high-level library to make long term android development easier and quicker. The one specific module has to capture images for a application... I've gotten everything right so far over the last couple months, except this one little thing and I don't know what to do any more: When I use the Camera object and implement a SurfaceHolder.Callback, the methods surfaceCreated() and surfaceChanged() are called one after the other. Then when the activity finishes, surfaceDestroyed() is called. This is how it should be, but when I stick the exact same code in my library (plain Java library that references the Android API - not in an activity), surfaceDestroyed() is called directly after created and changed. As a result - the camera object is closed before I can use it and the application force closes. What a pain. I can't do anything! This method call is controlled by the device.. Why does the surface close for no reason? Even when I post it to run on the activity thread through my own invokeAndWait(Runnable) method, like I do for many other things. I have 5 different working examples of different ways and implementations of capturing images in android but I still get the same issue when I plug it into my library. I don't understand what the difference is. The code is pretty much the same - and I post all the related code to the UI thread so its not a thread handling issue or anything like that. I've rewritten it about 20 times in different ways - same issue every time.. The only other way to approach it that I know of is creating a new Camera and setting it to the VideoView. The android source (c++ native code) however provides no Camera constructor, only an open() method which automatically forwards the camera's state to 'prepared' but I can only set the camera to the VideoView from the 'initialized' state. Pretty silly, I know, but there is no way around it unless I modify the Android library source code haha. not an option! The API does not allow for this method - you are expected to use it like my first example. So essentially - i just need to understand exactly why surfaceDestroyed() is called out of turn and if there is anything I can do to avoid it closing? If i can just understand the exact logic behind it and how it works! The documentation isn't much help! Secondly, if someone knows of any alternative ways to do it, as my second example, but hopefully one which the API actually allows for? haha Thanks guys. I would post code, but its fairly complicated, a couple thousand lines for this specific class and it would probably take a couple days to explain with all the threading and event listeners and what not. I just need help with this 1 single thing. Please let me know if you have any questions.

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• Looking for a function that will split profits/loss equally between 2 business partners.

  - by Hamish Grubijan

  This is not homework, for I am not a student. This is for my general curiosity. I apologize if I am reinventing the wheel here.The function I seek can be defined as follows (language agnostic): int getPercentageOfA(double moneyA, double workA, double moneyB, double workB) { // Perhaps you may assume that workA == 0 // Compute result return result; } Suppose Alice and Bob want to do business together ... such as ... selling used books. Alice is only interested in investing money in it and nothing else. Bob might invest some money, but he might have no $ available to invest. He will, however, put in the effort in finding a seller, a buyer, and doing maintenance. There are no tools, education, health insurance costs, or other expenses to consider. Both Alice and Bob wish to split the profits "equally" (A different weight like 40/60 for advanced users). Both are entrepreneurs, so they deal with low ROI/wage, and high income alike. There is no fixed wage, minimum wage, fixed ROI, or minimum ROI. They try to find the best deal possible, assume risks and go for it. Now, let's stick with the 50/50 model. If Alice invests $100, Bob invests work, and they will end up with a profit (or loss) of $60, they will split it equally - either both get $30 for their efforts/investments, or Bob ends up owing $30 to Alice. A second possibility: Both Alice and Bob invest 100, then Bob does all the work, and they end up splitting $60 profit. It looks like Alice should get only $15, because $30 of that profit came from Bob's investment and Bob's effort, so Alice shall have none of it, and the other $30 is to be split 50/50. Both of the examples above are trivial even when A and B want to split it 35/65 or what have you. Now it gets more complicated: What if Alice invests $70, and Bob invests $30 + does all of the work. It appears simple: (70,30) = (30,30) + (40,0) ... but, if only we knew how to weigh the two parts relative to each other. Another complicated (I think) example: what if Alice and Bob invest $70 and $30 respectively, and also put in an equal amount of work? I have a few data points: When A and B put in the same amount of work and the same $ - 50/50. When A puts in 100% of the money, and B does 100% of the work - 50/50. When A does all of the work and puts in all of the money - 100 for A / 0 for B (and vice-versa). When A puts in 50% of the money, and B puts in 50% of the money as well as does all of the work - 25 for A, and 75 for B (and vice-versa). If I fix things such that always workA = 0%, workB = 100% of the total work, then getPercentageOfA becomes a function: height z given x and y. The question is - how do you extrapolate this function between these several points? What is this function? If you can cover the cases when workA does not have to be 0% of the total work, and when investment vs work is split as 85/15 or using some other model, then what would the new function be?

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• DSP - Filtering in the frequency domain via FFT

  - by Trap

  I've been playing around a little with the Exocortex implementation of the FFT, but I'm having some problems. Whenever I modify the amplitudes of the frequency bins before calling the iFFT the resulting signal contains some clicks and pops, especially when low frequencies are present in the signal (like drums or basses). However, this does not happen if I attenuate all the bins by the same factor. Let me put an example of the output buffer of a 4-sample FFT: // Bin 0 (DC) FFTOut[0] = 0.0000610351563 FFTOut[1] = 0.0 // Bin 1 FFTOut[2] = 0.000331878662 FFTOut[3] = 0.000629425049 // Bin 2 FFTOut[4] = -0.0000381469727 FFTOut[5] = 0.0 // Bin 3, this is the first and only negative frequency bin. FFTOut[6] = 0.000331878662 FFTOut[7] = -0.000629425049 The output is composed of pairs of floats, each representing the real and imaginay parts of a single bin. So, bin 0 (array indexes 0, 1) would represent the real and imaginary parts of the DC frequency. As you can see, bins 1 and 3 both have the same values, (except for the sign of the Im part), so I guess bin 3 is the first negative frequency, and finally indexes (4, 5) would be the last positive frequency bin. Then to attenuate the frequency bin 1 this is what I do: // Attenuate the 'positive' bin FFTOut[2] *= 0.5; FFTOut[3] *= 0.5; // Attenuate its corresponding negative bin. FFTOut[6] *= 0.5; FFTOut[7] *= 0.5; For the actual tests I'm using a 1024-length FFT and I always provide all the samples so no 0-padding is needed. // Attenuate var halfSize = fftWindowLength / 2; float leftFreq = 0f; float rightFreq = 22050f; for( var c = 1; c < halfSize; c++ ) { var freq = c * (44100d / halfSize); // Calc. positive and negative frequency indexes. var k = c * 2; var nk = (fftWindowLength - c) * 2; // This kind of attenuation corresponds to a high-pass filter. // The attenuation at the transition band is linearly applied, could // this be the cause of the distortion of low frequencies? var attn = (freq < leftFreq) ? 0 : (freq < rightFreq) ? ((freq - leftFreq) / (rightFreq - leftFreq)) : 1; // Attenuate positive and negative bins. mFFTOut[ k ] *= (float)attn; mFFTOut[ k + 1 ] *= (float)attn; mFFTOut[ nk ] *= (float)attn; mFFTOut[ nk + 1 ] *= (float)attn; } Obviously I'm doing something wrong but can't figure out what. I don't want to use the FFT output as a means to generate a set of FIR coefficients since I'm trying to implement a very basic dynamic equalizer. What's the correct way to filter in the frequency domain? what I'm missing? Thanks in advance.

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• C++/msvc6 application crashes due to heap corruption, any hints?

  - by David Alfonso

  Hello all, let me say first that I'm writing this question after months of trying to find out the root of a crash happening in our application. I'll try to detail as much as possible what I've already found out about it. About the application It runs on Windows XP Professional SP2. It's built with Microsoft Visual C++ 6.0 with Service Pack 6. It's MFC based. It uses several external dlls (e.g. Xerces, ZLib or ACE). It has high performance requirements. It does a lot of network and hard disk I/O, but it's also cpu intensive. It has an exception handling mechanism which generates a minidump when an unhandled exception occurs. Facts about the crash It only happens on multiprocessor/multicore machines and under heavy loads of work. It happens at random (neither we nor our client have found a pattern yet). We cannot reproduce the crash on our testing lab. It only happens on some production systems (but always in multicore machines) It always ends up crashing at the same point, although the complete stack is not always the same. Let me add the stack of the crashing thread (obtained using WinDbg, sorry we don't have symbols) ChildEBP RetAddr Args to Child WARNING: Stack unwind information not available. Following frames may be wrong. 030af6c8 7c9206eb 77bfc3c9 01a80000 00224bc3 MyApplication+0x2a85b9 030af960 7c91e9c0 7c92901b 00000ab4 00000000 ntdll!RtlAllocateHeap+0xeac (FPO: [Non-Fpo]) 030af98c 7c9205c8 00000001 00000000 00000000 ntdll!ZwWaitForSingleObject+0xc (FPO: [3,0,0]) 030af9c0 7c920551 01a80898 7c92056d 313adfb0 ntdll!RtlpFreeToHeapLookaside+0x22 (FPO: [2,0,4]) 030afa8c 4ba3ae96 000307da 00130005 00040012 ntdll!RtlFreeHeap+0x1e9 (FPO: [Non-Fpo]) 030afacc 77bfc2e3 0214e384 3087c8d8 02151030 0x4ba3ae96 030afb00 7c91e306 7c80bfc1 00000948 00000001 msvcrt!free+0xc8 (FPO: [Non-Fpo]) 030afb20 0042965b 030afcc0 0214d780 02151218 ntdll!ZwReleaseSemaphore+0xc (FPO: [3,0,0]) 030afb7c 7c9206eb 02e6c471 02ea0000 00000008 MyApplication+0x2965b 030afe60 7c9205c8 02151248 030aff38 7c920551 ntdll!RtlAllocateHeap+0xeac (FPO: [Non-Fpo]) 030afe74 7c92056d 0210bfb8 02151250 02151250 ntdll!RtlpFreeToHeapLookaside+0x22 (FPO: [2,0,4]) 030aff38 77bfc2de 01a80000 00000000 77bfc2e3 ntdll!RtlFreeHeap+0x647 (FPO: [Non-Fpo]) 7c92056d c5ffffff ce7c94be ff7c94be 00ffffff msvcrt!free+0xc3 (FPO: [Non-Fpo]) 7c920575 ff7c94be 00ffffff 12000000 907c94be 0xc5ffffff 7c920579 00ffffff 12000000 907c94be 90909090 0xff7c94be *** WARNING: Unable to verify checksum for xerces-c_2_7.dll *** ERROR: Symbol file could not be found. Defaulted to export symbols for xerces-c_2_7.dll - 7c92057d 12000000 907c94be 90909090 8b55ff8b MyApplication+0xbfffff 7c920581 907c94be 90909090 8b55ff8b 08458bec xerces_c_2_7 7c920585 90909090 8b55ff8b 08458bec 04408b66 0x907c94be 7c920589 8b55ff8b 08458bec 04408b66 0004c25d 0x90909090 7c92058d 08458bec 04408b66 0004c25d 90909090 0x8b55ff8b The address MyApplication+0x2a85b9 corresponds to a call to erase() of a std::list. What I have tried so far Reviewing all the code related to the point where the crash ends happening. Trying to enable pageheap on our testing lab though nothing useful has been found by now. We have substituted the std::list for a C array and then it crashes in other part of the code (although it is related code, it's not in the code where the old list resided). Coincidentally, now it crashes in another erase, though this time of a std::multiset. Let me copy the stack contained in the dump: ntdll.dll!_RtlpCoalesceFreeBlocks@16() + 0x124e bytes ntdll.dll!_RtlFreeHeap@12() + 0x91f bytes msvcrt.dll!_free() + 0xc3 bytes MyApplication.exe!006a4fda() [Frames below may be incorrect and/or missing, no symbols loaded for MyApplication.exe] MyApplication.exe!0069f305() ntdll.dll!_NtFreeVirtualMemory@16() + 0xc bytes ntdll.dll!_RtlpSecMemFreeVirtualMemory@16() + 0x1b bytes ntdll.dll!_ZwWaitForSingleObject@12() + 0xc bytes ntdll.dll!_RtlpFreeToHeapLookaside@8() + 0x26 bytes ntdll.dll!_RtlFreeHeap@12() + 0x114 bytes msvcrt.dll!_free() + 0xc3 bytes c5ffffff() Possible solutions (that I'm aware of) which cannot be applied "Migrate the application to a newer compiler": We are working on this but It's not a solution at the moment. "Enable pageheap (normal or full)": We can't enable pageheap on production machines as this affects performance heavily. I think that's all I remember now, if I have forgotten something I'll add it asap. If you can give me some hint or propose some possible solution, don't hesitate to answer! Thank you in advance for your time and advice.

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• C++ MySQL++ Delete query statement brain killer question

  - by shauny

  Hello all, I'm relatively new to the MySQL++ connector in C++, and have an really annoying issue with it already! I've managed to get stored procedures working, however i'm having issues with the delete statements. I've looked high and low and have found no documentation with examples. First I thought maybe the code needs to free the query/connection results after calling the stored procedure, but of course MySQL++ doesn't have a free_result method... or does it? Anyways, here's what I've got: #include <iostream> #include <stdio.h> #include <queue> #include <deque> #include <sys/stat.h> #include <mysql++/mysql++.h> #include <boost/thread/thread.hpp> #include "RepositoryQueue.h" using namespace boost; using namespace mysqlpp; class RepositoryChecker { private: bool _isRunning; Connection _con; public: RepositoryChecker() { try { this->_con = Connection(false); this->_con.set_option(new MultiStatementsOption(true)); this->_con.set_option(new ReconnectOption(true)); this->_con.connect("**", "***", "***", "***"); this->ChangeRunningState(true); } catch(const Exception& e) { this->ChangeRunningState(false); } } /** * Thread method which runs and creates the repositories */ void CheckRepositoryQueues() { //while(this->IsRunning()) //{ std::queue<RepositoryQueue> queues = this->GetQueue(); if(queues.size() > 0) { while(!queues.empty()) { RepositoryQueue &q = queues.front(); char cmd[256]; sprintf(cmd, "svnadmin create /home/svn/%s/%s/%s", q.GetPublicStatus().c_str(), q.GetUsername().c_str(), q.GetRepositoryName().c_str()); if(this->DeleteQueuedRepository(q.GetQueueId())) { printf("query deleted?\n"); } printf("Repository created!\n"); queues.pop(); } } boost::this_thread::sleep(boost::posix_time::milliseconds(500)); //} } protected: /** * Gets the latest queue of repositories from the database * and returns them inside a cool queue defined with the * RepositoryQueue class. */ std::queue<RepositoryQueue> GetQueue() { std::queue<RepositoryQueue> queues; Query query = this->_con.query("CALL sp_GetRepositoryQueue();"); StoreQueryResult result = query.store(); RepositoryQueue rQ; if(result.num_rows() > 0) { for(unsigned int i = 0;i < result.num_rows(); ++i) { rQ = RepositoryQueue((unsigned int)result[i][0], (unsigned int)result[i][1], (String)result[i][2], (String)result[i][3], (String)result[i][4], (bool)result[i][5]); queues.push(rQ); } } return queues; } /** * Allows the thread to be shut off. */ void ChangeRunningState(bool isRunning) { this->_isRunning = isRunning; } /** * Returns the running value of the active thread. */ bool IsRunning() { return this->_isRunning; } /** * Deletes the repository from the mysql queue table. This is * only called once it has been created. */ bool DeleteQueuedRepository(unsigned int id) { char cmd[256]; sprintf(cmd, "DELETE FROM RepositoryQueue WHERE Id = %d LIMIT 1;", id); Query query = this->_con.query(cmd); return (query.exec()); } }; I've removed all the other methods as they're not needed... Basically it's the DeleteQueuedRepository method which isn't working, the GetQueue works fine. PS: This is on a Linux OS (Ubuntu server) Many thanks, Shaun

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• Languages and VMs: Features that are hard to optimize and why

  - by mrjoltcola

  I'm doing a survey of features in preparation for a research project. Name a mainstream language or language feature that is hard to optimize, and why the feature is or isn't worth the price paid, or instead, just debunk my theories below with anecdotal evidence. Before anyone flags this as subjective, I am asking for specific examples of languages or features, and ideas for optimization of these features, or important features that I haven't considered. Also, any references to implementations that prove my theories right or wrong. Top on my list of hard to optimize features and my theories (some of my theories are untested and are based on thought experiments): 1) Runtime method overloading (aka multi-method dispatch or signature based dispatch). Is it hard to optimize when combined with features that allow runtime recompilation or method addition. Or is it just hard, anyway? Call site caching is a common optimization for many runtime systems, but multi-methods add additional complexity as well as making it less practical to inline methods. 2) Type morphing / variants (aka value based typing as opposed to variable based) Traditional optimizations simply cannot be applied when you don't know if the type of someting can change in a basic block. Combined with multi-methods, inlining must be done carefully if at all, and probably only for a given threshold of size of the callee. ie. it is easy to consider inlining simple property fetches (getters / setters) but inlining complex methods may result in code bloat. The other issue is I cannot just assign a variant to a register and JIT it to the native instructions because I have to carry around the type info, or every variable needs 2 registers instead of 1. On IA-32 this is inconvenient, even if improved with x64's extra registers. This is probably my favorite feature of dynamic languages, as it simplifies so many things from the programmer's perspective. 3) First class continuations - There are multiple ways to implement them, and I have done so in both of the most common approaches, one being stack copying and the other as implementing the runtime to use continuation passing style, cactus stacks, copy-on-write stack frames, and garbage collection. First class continuations have resource management issues, ie. we must save everything, in case the continuation is resumed, and I'm not aware if any languages support leaving a continuation with "intent" (ie. "I am not coming back here, so you may discard this copy of the world"). Having programmed in the threading model and the contination model, I know both can accomplish the same thing, but continuations' elegance imposes considerable complexity on the runtime and also may affect cache efficienty (locality of stack changes more with use of continuations and co-routines). The other issue is they just don't map to hardware. Optimizing continuations is optimizing for the less-common case, and as we know, the common case should be fast, and the less-common cases should be correct. 4) Pointer arithmetic and ability to mask pointers (storing in integers, etc.) Had to throw this in, but I could actually live without this quite easily. My feelings are that many of the high-level features, particularly in dynamic languages just don't map to hardware. Microprocessor implementations have billions of dollars of research behind the optimizations on the chip, yet the choice of language feature(s) may marginalize many of these features (features like caching, aliasing top of stack to register, instruction parallelism, return address buffers, loop buffers and branch prediction). Macro-applications of micro-features don't necessarily pan out like some developers like to think, and implementing many languages in a VM ends up mapping native ops into function calls (ie. the more dynamic a language is the more we must lookup/cache at runtime, nothing can be assumed, so our instruction mix is made up of a higher percentage of non-local branching than traditional, statically compiled code) and the only thing we can really JIT well is expression evaluation of non-dynamic types and operations on constant or immediate types. It is my gut feeling that bytecode virtual machines and JIT cores are perhaps not always justified for certain languages because of this. I welcome your answers.

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• Why i cannot get the frame of a UIView in order to move it? The view is defined.

  - by Jann

  I am creating a nav-based app with a view that floats at the bottom of the screen (Alpha .7 most of the time). I create it like this... // stuff to create the tabbar/nav bar. // THIS ALL WORKS... // then add it to subview. [window addSubview:tabBarController.view]; // need this last line to display the window (and tab bar controller) [window makeKeyAndVisible]; // Okay, here is the code i am using to create a grey-ish strip exactly `zlocationAccuracyHeight` pixels high at `zlocationAccuracyVerticalStartPoint` starting point vertically. CGRect locationManagerAccuracyUIViewFrame = CGRectMake(0,zlocationAccuracyVerticalStartPoint,[[UIScreen mainScreen] bounds].size.width,zlocationAccuracyHeight); self.locationManagerAccuracyUIView = [[UIView alloc] initWithFrame:locationManagerAccuracyUIViewFrame]; self.locationManagerAccuracyUIView.autoresizingMask = (UIViewAutoresizingFlexibleWidth); self.locationManagerAccuracyUIView.backgroundColor = [UIColor darkGrayColor]; [self.locationManagerAccuracyUIView setAlpha:0]; CGRect locationManagerAccuracyLabelFrame = CGRectMake(0, 0,[[UIScreen mainScreen] bounds].size.width,zlocationAccuracyHeight); locationManagerAccuracyLabel = [[UILabel alloc] initWithFrame:locationManagerAccuracyLabelFrame]; if ([myGizmoClass useLocationServices] == 0) { locationManagerAccuracyLabel.text = @"GPS Accuracy: Using Manual Location"; } else { locationManagerAccuracyLabel.text = @"GPS Accuracy: One Moment Please..."; } locationManagerAccuracyLabel.font = [UIFont boldSystemFontOfSize:12]; locationManagerAccuracyLabel.textAlignment = UITextAlignmentCenter; locationManagerAccuracyLabel.textColor = [UIColor whiteColor]; locationManagerAccuracyLabel.backgroundColor = [UIColor clearColor]; [locationManagerAccuracyLabel setAlpha:0]; [self.locationManagerAccuracyUIView addSubview: locationManagerAccuracyLabel]; [window addSubview: self.locationManagerAccuracyUIView]; this all works (i am not sure about the order i create the uiview in ... meaning i am creating the frame, the view, creating the "accuracy text" and adding that to the view, then adding the uiview as a subview of the window . It works and seems correct in my logic. So, here is the tough part. I have a timer that i am testing with. I am trying to float the uiview up by 30 pix. here is that code: [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:0.3]; CGRect rect = [ self.locationManagerAccuracyUIView frame]; NSLog(@"ORIGIN: %d x %d (%@)\n",rect.origin.x,rect.origin.y,rect); rect.origin.y -= 30; [UIView commitAnimations]; The problem? rect is nill, rect.origin.x and rect.origin.y are both zero. Can anyone tell me why? Here is how i set up self.locationManagerAccuracyUIView in my files: Delegate.h UIView *locationManagerAccuracyUIView; UILabel *locationManagerAccuracyLabel; ... @property (nonatomic, retain) IBOutlet UIView *locationManagerAccuracyUIView; @property (nonatomic, retain) IBOutlet UILabel *locationManagerAccuracyLabel; Delegate.m ... @synthesize locationManagerAccuracyUIView; @synthesize locationManagerAccuracyLabel; ... BTW: Other places in another timer i DO set the alpha to fade in and out and THAT works! So locationManagerAccuracyUIView is valid and defined as a view... For instance: [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:0.5]; [locationManagerAccuracyLabel setAlpha:1]; [UIView commitAnimations]; [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:0.5]; [self.locationManagerAccuracyUIView setAlpha:.7]; [UIView commitAnimations]; ...and it DOES work. Can anyone help me? As an aside: I know, when typing this I used self.locationManagerAccuracyUIView and locationManagerAccuracyUIView interchangeably to see if for some reason that was the issue. It is not. :) Thx

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• Adding a div layer on top of a jquery carousel. Tough one.

  - by wilwaldon

  Hey everyone, I have a tough one, well it's tough for me because I'm kinda new to the whole jQuery carousel thing, never built one before this project. Here's my problem. If you go to the TEST SITE you will see a scroller with a blue background about half way down the page. If you mouse onto the "data analytics" slide you should see a black box fade in. Here is my dilemma. I want that black box to be a menu that's connected to the data analytics slide. I've done a mock up for you so you can see what I'm talking about. Here is my scroller code. I'm using jCarousel. <div class="carousel"> <ul> <li> <div id="homeslide1"> testers sdfasdfasdfas asdftjhs iasndkad kasdnf <a href="#" id="#homeslide1-toggle">Close this</a> </div> <a href="#" id="homeslide1-show"><img src="<?php bloginfo('template_url'); ?>/images/home_data_analytics.jpg" width="200" height="94" /></a> </li> <li><img src="<?php bloginfo('template_url'); ?>/images/home_oem_partnerships.jpg" width="200" height="94" /></li> <li><img src="<?php bloginfo('template_url'); ?>/images/home_reporting.jpg" width="200" height="92" /></li> <li><img src="<?php bloginfo('template_url'); ?>/images/home_returning_lost_customers.jpg" width="200" height="92" /></li> <li><img src="<?php bloginfo('template_url'); ?>/images/home_sales.jpg" width="200" height="92" /></li> <li><img src="<?php bloginfo('template_url'); ?>/images/home_service_retention.jpg" width="200" height="92" /></li> </ul> Here is my scroller css /*HOMEPAGE SCROLLER*/ .carousel {!important padding:10px; width: 890px; margin: 0px 0px 0px 26px;} .carousel ul li element.style{height: 94px;} .carousel ul{width: 200px; padding: 5px;} .carouselitem{height: 94px;} .prev{background: url(images/home_left_scroll.png); height: 94px; width: 16px; text-indent: -999px; outline: none; cursor:pointer; float: left;} .next{background: url(images/home_right_scroll.png); height: 94px; width: 16px; text-indent: -999px; outline: none; cursor:pointer; float: right;} .carousel ul li{ padding: 0px 3px 0px 3px; margin: 0px; height:!important 94px; } .home_right_arrow{ width: 16px; float: right;} .home_left_arrow{ width: 16px; float: left;} .homeslide1{ width: 200px; height: 94px;} I've tried all sorts of z-index tricks but can't seem to figure it out on my own. If you solve this riddle I'll buy you a beer if we ever meet up. I'll also give you a high five through the internet. Is there a simple way to do this via jQuery? If so could you point me in the right direction? Thanks so much.

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• Insane SmartGWT + GWT situation... Error on instantiating ListGridRecord?

  - by Xandel

  Hi all, I am asking this here in the hope that someone has maybe come across this situation too... I have posted this on the SmartGWT forum: I am having an issue when trying to instantiate a ListGridRecord object on my server side. I am using the ListGrid on the client side, I want to use GWT's RPC to pass back an array of ListGridRecord objects to populate the grid with. I know that SmartGWT is designed to link to a datasource but I want full control over when I populate the grid and this shouldn't be as much of a nightmare as it is to do. I have searched high and low and cannot find anyone complaining about the same thing. The exception however (listed below) has come up (in my search findings) as a possible memory error - where increasing the memory (-Xmx512m argument) has apparently solved the problem. It did not, however, sort out mine. If anyone can shed any light on this I would greatly appreciate it! Here are my details: Developing using Eclipse Galileo on Ubuntu 9.04 (Jaunty) and GWT 2.0.3, I built the initial GWT project using the webAppCreator bundled with the GWT 2.0.3 release and imported the project into Eclipse as described on the GWT Getting Started Page (as using the GWT Eclipse plugin caused even more nightmares when trying to connect to a database - this is apparently due to using the Google App Engine and turning it off as all the posts suggested only causes ClassNotFound exceptions). The line that causes the error is literally: ListGridRecord a = new ListGridRecord(); The error I get is the following: 00:00:25.916 [WARN] Exception while dispatching incoming RPC call com.google.gwt.user.server.rpc.UnexpectedException : Service method 'public abstract java.lang.String za.co.company.product.client.service.EmployeeServi ce.getAllEmployeeAsListGridRecord()' threw an unexpected exception: java.lang.UnsatisfiedLinkError: com.smartgwt.client.util.LogUtil.setJSNIErrorHandl er()V at com.google.gwt.user.server.rpc.RPC.encodeResponseF orFailure(RPC.java:378) at com.google.gwt.user.server.rpc.RPC.invokeAndEncode Response(RPC.java:581) at com.google.gwt.user.server.rpc.RemoteServiceServle t.processCall(RemoteServiceServlet.java:188) at com.google.gwt.user.server.rpc.RemoteServiceServle t.processPost(RemoteServiceServlet.java:224) at com.google.gwt.user.server.rpc.AbstractRemoteServi ceServlet.doPost(AbstractRemoteServiceServlet.java :62) at javax.servlet.http.HttpServlet.service(HttpServlet .java:637) at javax.servlet.http.HttpServlet.service(HttpServlet .java:717) at org.mortbay.jetty.servlet.ServletHolder.handle(Ser vletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler.handle(Se rvletHandler.java:362) at org.mortbay.jetty.security.SecurityHandler.handle( SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(Se ssionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(Co ntextHandler.java:729) at org.mortbay.jetty.webapp.WebAppContext.handle(WebA ppContext.java:405) at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152) at org.mortbay.jetty.handler.RequestLogHandler.handle (RequestLogHandler.java:49) at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:324) at org.mortbay.jetty.HttpConnection.handleRequest(Htt pConnection.java:505) at org.mortbay.jetty.HttpConnection$RequestHandler.co ntent(HttpConnection.java:843) at org.mortbay.jetty.HttpParser.parseNext(HttpParser. java:647) at org.mortbay.jetty.HttpParser.parseAvailable(HttpPa rser.java:211) at org.mortbay.jetty.HttpConnection.handle(HttpConnec tion.java:380) at org.mortbay.io.nio.SelectChannelEndPoint.run(Selec tChannelEndPoint.java:395) at org.mortbay.thread.QueuedThreadPool$PoolThread.run (QueuedThreadPool.java:488) Caused by: java.lang.UnsatisfiedLinkError: com.smartgwt.client.util.LogUtil.setJSNIErrorHandl er()V at com.smartgwt.client.util.LogUtil.setJSNIErrorHandl er(Native Method) at com.smartgwt.client.core.JsObject.(JsObjec t.java:30) at za.co.company.product.server.service.EmployeeServi ceImpl.getAllEmployeeAsListGridRecord(EmployeeServ iceImpl.java:83) at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Native MethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(De legatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at com.google.gwt.user.server.rpc.RPC.invokeAndEncode Response(RPC.java:562) at com.google.gwt.user.server.rpc.RemoteServiceServle t.processCall(RemoteServiceServlet.java:188) at com.google.gwt.user.server.rpc.RemoteServiceServle t.processPost(RemoteServiceServlet.java:224) at com.google.gwt.user.server.rpc.AbstractRemoteServi ceServlet.doPost(AbstractRemoteServiceServlet.java :62) at javax.servlet.http.HttpServlet.service(HttpServlet .java:637) at javax.servlet.http.HttpServlet.service(HttpServlet .java:717) at org.mortbay.jetty.servlet.ServletHolder.handle(Ser vletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler.handle(Se rvletHandler.java:362) at org.mortbay.jetty.security.SecurityHandler.handle( SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(Se ssionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(Co ntextHandler.java:729) at org.mortbay.jetty.webapp.WebAppContext.handle(WebA ppContext.java:405) at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152) at org.mortbay.jetty.handler.RequestLogHandler.handle (RequestLogHandler.java:49) at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:324) at org.mortbay.jetty.HttpConnection.handleRequest(Htt pConnection.java:505) at org.mortbay.jetty.HttpConnection$RequestHandler.co ntent(HttpConnection.java:843) at org.mortbay.jetty.HttpParser.parseNext(HttpParser. java:647) at org.mortbay.jetty.HttpParser.parseAvailable(HttpPa rser.java:211) at org.mortbay.jetty.HttpConnection.handle(HttpConnec tion.java:380) at org.mortbay.io.nio.SelectChannelEndPoint.run(Selec tChannelEndPoint.java:395) at org.mortbay.thread.QueuedThreadPool$PoolThread.run (QueuedThreadPool.java:488) Thanks in advance! Xandel

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