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• Thoughts on GoGrid vs EC2

  - by Jason

  I am currently hosting my SaaS application at GoGrid (Microsoft stack). Here's what I have: Database Server - physical box, 12 GB RAM, 2 X Quad Core CPU (2.13 GHz Xeon E5506) 2 Web / App servers - cloud servers, 2 GB RAM, 2 VCPUs 300 GB monthly bandwidth I am paying around $900 / month for this. My web / app servers are busting at the seams and need to be upgraded to 4 GB of RAM. I also need a firewall, and GoGrid just added this service for an additional $200. After the upgrade, I will be paying around $1,400. I started looking at Amazon EC2, specifically this config: Database server - "High Memory Double Extra Large Instance" - 34 GB RAM, 13 EC2 compute units 2 Web / App servers - "Large Instance" - 7.5 GB RAM, 4 EC2 compute units If I go with 1 year reserved instances, my upfront cost would be $4,500 and my monthly would be $700. This comes to $1,075 / month when amortized. Amazon also includes a firewall for free. Here are my questions: Do any of you have experience running a database (especially SQL Server) on an EC2 instance? How did it perform compared to a dedicated machine? One of my major concerns is with disk I/O. Amazon's description of a compute unit is fairly vague. Any ideas on how the CPU performance on the database servers would compare? I am hoping that the Amazon solution will provide significantly better performance than my current or even improved GoGrid setup. Having a virtual database server would also be nice in terms of availability. Right now I would be in serious trouble if I had any hardware issues. Thanks for any insight...

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• Very slow guards in my monadic random implementation (haskell)

  - by danpriduha

  Hi! I was tried to write one random number generator implementation, based on number class. I also add there Monad and MonadPlus instance. What mean "MonadPlus" and why I add this instance? Because of I want to use guards like here: -- test.hs -- import RandomMonad import Control.Monad import System.Random x = Rand (randomR (1 ::Integer, 3)) ::Rand StdGen Integer y = do a <-x guard (a /=2) guard (a /=1) return a here comes RandomMonad.hs file contents: -- RandomMonad.hs -- module RandomMonad where import Control.Monad import System.Random import Data.List data RandomGen g => Rand g a = Rand (g ->(a,g)) | RandZero instance (Show g, RandomGen g) => Monad (Rand g) where return x = Rand (\g ->(x,g)) (RandZero)>>= _ = RandZero (Rand argTransformer)>>=(parametricRandom) = Rand funTransformer where funTransformer g | isZero x = funTransformer g1 | otherwise = (getRandom x g1,getGen x g1) where x = parametricRandom val (val,g1) = argTransformer g isZero RandZero = True isZero _ = False instance (Show g, RandomGen g) => MonadPlus (Rand g) where mzero = RandZero RandZero `mplus` x = x x `mplus` RandZero = x x `mplus` y = x getRandom :: RandomGen g => Rand g a ->g ->a getRandom (Rand f) g = (fst (f g)) getGen :: RandomGen g => Rand g a ->g -> g getGen (Rand f) g = snd (f g) when I run ghci interpreter, and give following command getRandom y (mkStdGen 2000000000) I can see memory overflow on my computer (1G). It's not expected, and if I delete one guard, it works very fast. Why in this case it works too slow? What I do wrong?

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• Several Objective-C objects become Invalid for no reason, sometimes.

  - by farnsworth

  - (void)loadLocations { NSString *url = @"<URL to a text file>"; NSStringEncoding enc = NSUTF8StringEncoding; NSString *locationString = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:url] usedEncoding:&enc error:nil]; NSArray *lines = [locationString componentsSeparatedByString:@"\n"]; for (int i=0; i<[lines count]; i++) { NSString *line = [lines objectAtIndex:i]; NSArray *components = [line componentsSeparatedByString:@", "]; Restaurant *res = [byID objectForKey:[components objectAtIndex:0]]; if (res) { NSString *resAddress = [components objectAtIndex:3]; NSArray *loc = [NSArray arrayWithObjects:[components objectAtIndex:1], [components objectAtIndex:2]]; [res.locationCoords setObject:loc forKey:resAddress]; } else { NSLog([[components objectAtIndex:0] stringByAppendingString:@" res id not found."]); } } } There are a few weird things happening here. First, at the two lines where the NSArray lines is used, this message is printed to the console- *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSCFDictionary count]: method sent to an uninitialized mutable dictionary object' which is strange since lines is definitely not an NSMutableDictionary, definitely is initialized, and because the app doesn't crash. Also, at random points in the loop, all of the variables that the debugger can see will become Invalid. Local variables, property variables, everything. Then after a couple lines they will go back to their original values. setObject:forKey never has an effect on res.locationCoords, which is an NSMutableDictionary. I'm sure that res, res.locationCoords, and byId are initialized. I also tried adding a retain or copy to lines, same thing. I'm sure there's a basic memory management principle I'm missing here but I'm at a loss.

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• POST XML to server, receive PDF

  - by Shaggy Frog

  Similar to this question, we are developing a Web app where the client clicks a button to receive a PDF from the server. Right now we're using the .ajax() method with jQuery to POST the data the backend needs to generate the PDF (we're sending XML) when the button is pressed, and then the backend is generating the PDF entirely in-memory and sending it back as application/pdf in the HTTP response. One answer to that question requires the server-side save the PDF to disk so it can give back a URL for the client to GET. But I don't want the backend caching content at all. The other answer suggests the use of a jQuery plugin, but when you look at its code, it's actually generating a form element and then submitting the form. That method will not work for us since we are sending XML data in the body of the HTTP request. Is there a way to have the browser open up the PDF without caching the PDF server-side, and without requiring us to throw out our send-data-to-the-server-using-XML solution? (I'd like the browser to behave like it does when a form element is submitted -- a POST is made and then the browser looks at the Content-type header to determine what to do next, like load the PDF in the browser window, a la Safari)

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• C/C++: feedback in analyzing a code example

  - by KaiserJohaan

  Hello, I have a piece of code from an assignment I am uncertain about. I feel confident that I know the answer, but I just want to double-check with the community incase there's something I forgot. The title is basically secure coding and the question is just to explain the results. int main() { unsigned int i = 1; unsigned int c = 1; while (i > 0) { i = i*2; c++; } printf("%d\n", c); return 0; } My reasoning is this: At first glance you could imagine the code would run forever, considering it's initialized to a positive value and ever increasing. This of course is wrong because eventually the value will grow so large it will cause an integer overflow. This in turn is not entirely true either, because eventally it will force the variable 'i' to be signed by making the last bit to 1 and therefore regarded as a negative number, therefore terminating the loop. So it is not writing to unallocated memory and therefore cause integer overflow, but rather violating the data type and therefore causing the loop to terminate. I am quite sure this is the reason, but I just want to double check. Any opinions?

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• java GC periodically enters into several full GC cycles

  - by Peter

  Environment: sun JDK 1.6.0_16 vm settings: -XX:+DisableExplicitGC -XX:+UseConcMarkSweepGC -Xms1024 -Xmx1024M -XX:MaxNewSize=448m -XX:NewSize=448m -XX:SurvivorRatio=4(6 also checked) -XX:MaxPermSize=128M OS: windows server 2003 processor: 4 cores of INTEL XEON 5130, 2000 Hz my application description: high intensity of concurrent(java 5 concurrency used) operations completed each time by commit to oracle. it's about 20-30 threads run non stop, doing tasks. application runs in JBOSS web container. My GC starts work normally, I see a lot of small GCs and all that time CPU shows good load, like all 4 cores loaded to 40-50%, CPU graph is stable. Then , after 1 min of good work, CPU starts drop to 0% on 2 cores from 4, it's graph becomes unstable, goes up and down("teeth"). I see, that my threads work slower(I have monitoring), I see that GC starts produce a lot of FULL GC during that time and next 4-5 minutes this situation remains as is, then for short period of time, like 1 minute, it gets back to normal situation, but shortly after that all bad thing repeats. Question: Why I have so frequent full GC??? How to prevent that? I played with SurvivorRatio - does not help. I noticed, that application behaves normally until first FULL GC occurs, while I have enough memory. Then it runs badly. my GC LOG: starts good then long period of FULL GCs(many of them) 1027.861: [GC 942200K-623526K(991232K), 0.0887588 secs] 1029.333: [GC 803279K(991232K), 0.0927470 secs] 1030.551: [GC 967485K-625549K(991232K), 0.0823024 secs] 1030.634: [GC 625957K(991232K), 0.0763656 secs] 1033.126: [GC 969613K-632963K(991232K), 0.0850611 secs] 1033.281: [GC 649899K(991232K), 0.0378358 secs] 1035.910: [GC 813948K(991232K), 0.3540375 secs] 1037.994: [GC 967729K-637198K(991232K), 0.0826042 secs] 1038.435: [GC 710309K(991232K), 0.1370703 secs] 1039.665: [GC 980494K-972462K(991232K), 0.6398589 secs] 1040.306: [Full GC 972462K-619643K(991232K), 3.7780597 secs] 1044.093: [GC 620103K(991232K), 0.0695221 secs] 1047.870: [Full GC 991231K-626514K(991232K), 3.8732457 secs] 1053.739: [GC 942140K(991232K), 0.5410483 secs] 1056.343: [Full GC 991232K-634157K(991232K), 3.9071443 secs] 1061.257: [GC 786274K(991232K), 0.3106603 secs] 1065.229: [Full GC 991232K-641617K(991232K), 3.9565638 secs] 1071.192: [GC 945999K(991232K), 0.5401515 secs] 1073.793: [Full GC 991231K-648045K(991232K), 3.9627814 secs] 1079.754: [GC 936641K(991232K), 0.5321197 secs]

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• Constructor and Destructors in C++ [Not a question] [closed]

  - by Jack

  I am using gcc. Please tell me if I am wrong - Lets say I have two classes A & B class A { public: A(){cout<<"A constructor"<<endl;} ~A(){cout<<"A destructor"<<endl;} }; class B:public A { public: B(){cout<<"B constructor"<<endl;} ~B(){cout<<"B destructor"<<endl;} }; 1) The first line in B's constructor should be a call to A's constructor ( I assume compiler automatically inserts it). Also the last line in B's destructor will be a call to A's destructor (compiler does it again). Why was it built this way? 2) When I say A * a = new B(); compiler creates a new B object and checks to see if A is a base class of B and if it is it allows 'a' to point to the newly created object. I guess that is why we don't need any virtual constructors. ( with help from @Tyler McHenry , @Konrad Rudolph) 3) When I write delete a compiler sees that a is an object of type A so it calls A's destructor leading to a problem which is solved by making A's destructor virtual. As user - Little Bobby Tables pointed out to me all destructors have the same name destroy() in memory so we can implement virtual destructors and now the call is made to B's destructor and all is well in C++ land. Please comment.

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• Why is my UITableView not being set?

  - by Jamie L

  I checked using the debbuger in the viewDidLoad method and tracerTableView is 0x0 which i assume means it is nil. I don't understand. I should go ahaed say yes I have already checked my nib file and yes all the connections are correct. Here is the header file and the begging of the .m. ///////////// .h file //////////// @interface TrackerListController : UITableViewController { // The mutable (modifiable) dictionary days holds all the data for the days tab NSMutableArray *trackerList; UITableView *tracerTableView; } @property (nonatomic, retain) NSMutableArray *trackerList; @property (nonatomic, retain) IBOutlet UITableView. *tracerTableView; //The addPackage: method is invoked when the user taps the addbutton created at runtime. -(void) addPackage : (id) sender; @end /////////////////////////////////////////////////////////////////////////////////////////////////// ////////////////////////////////////// .m file ////////////////////////////////////// @implementation TrackerListController @synthesize trackerList, tracerTableView; (void)viewDidLoad { [super viewDidLoad]; self.title = @"Package Tracker"; self.navigationItem.leftBarButtonItem = self.editButtonItem; UIBarButtonItem *addButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(addPackage:)]; // Set up the Add custom button on the right of the navigation bar self.navigationItem.rightBarButtonItem = addButton; [addButton release]; // Release the addButton from memory since it is no longer needed }

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• Editing a remote file on-the-fly with PHP

  - by user275074

  Hi, I have a requirement to edit a remote text file on-the-fly, the content of which currently stands at ~1Mb. I have tried a couple of approaches and both seem to be clunky or hog memory which I can't rely on. Thinking out logically what I'm trying to achieve is: FTP to a remote server. Download a copy of the file for backup purposes and store it somewhere locally. Open the remote file and add the necessary lines required. Remove lines from the remote file as per an array of un-required data generated from the local server. Is this possible? I've managed to code steps 1 and 2 but I'm having difficult with 3 and 4. The way I'm doing it now is to use fgets and return the whole string. Really, I don't want to do this as it involves manipulating and re-generating the whole string (and it's large) and then re-inserting it in between two markers in the remote file. Is there no way of manipulating the lines of text in the file on-the-fly?

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• Are there pitfalls to using static class/event as an application message bus

  - by Doug Clutter

  I have a static generic class that helps me move events around with very little overhead: public static class MessageBus<T> where T : EventArgs { public static event EventHandler<T> MessageReceived; public static void SendMessage(object sender, T message) { if (MessageReceived != null) MessageReceived(sender, message); } } To create a system-wide message bus, I simply need to define an EventArgs class to pass around any arbitrary bits of information: class MyEventArgs : EventArgs { public string Message { get; set; } } Anywhere I'm interested in this event, I just wire up a handler: MessageBus<MyEventArgs>.MessageReceived += (s,e) => DoSomething(); Likewise, triggering the event is just as easy: MessageBus<MyEventArgs>.SendMessage(this, new MyEventArgs() {Message="hi mom"}); Using MessageBus and a custom EventArgs class lets me have an application wide message sink for a specific type of message. This comes in handy when you have several forms that, for example, display customer information and maybe a couple forms that update that information. None of the forms know about each other and none of them need to be wired to a static "super class". I have a couple questions: fxCop complains about using static methods with generics, but this is exactly what I'm after here. I want there to be exactly one MessageBus for each type of message handled. Using a static with a generic saves me from writing all the code that would maintain the list of MessageBus objects. Are the listening objects being kept "alive" via the MessageReceived event? For instance, perhaps I have this code in a Form.Load event: MessageBus<CustomerChangedEventArgs>.MessageReceived += (s,e) => DoReload(); When the Form is Closed, is the Form being retained in memory because MessageReceived has a reference to its DoReload method? Should I be removing the reference when the form closes: MessageBus<CustomerChangedEventArgs>.MessageReceived -= (s,e) => DoReload();

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• Silverlight performance with many loaded controls

  - by gius

  I have a SL application with many DataGrids (from Silverlight Toolkit), each on its own view. If several DataGrids are opened, changing between views (TabItems, for example) takes a long time (few seconds) and it freezes the whole application (UI thread). The more DataGrids are loaded, the longer the change takes. These DataGrids that slow the UI chanage might be on other places in the app and not even visible at that moment. But once they are opened (and loaded with data), they slow showing other DataGrids. Note that DataGrids are NOT disposed and then recreated again, they still remain in memory, only their parent control is being hidden and visible again. I have profiled the application. It shows that agcore.dll's SetValue function is the bottleneck. Unfortunately, debug symbols are not available for this Silverlight native library responsible for drawing. The problem is not in the DataGrid control - I tried to replace it with XCeed's grid and the performance when changing views is even worse. Do you have any idea how to solve this problem? Why more opened controls slow down other controls? I have created a sample that shows this issue: http://cenud.cz/PerfTest.zip UPDATE: Using VS11 profiler on the sample provided suggests that the problem could be in MeasureOverride being called many times (for each DataGridCell, I guess). But still, why is it slower as more controls are loaded elsewhere? Is there a way to improve the performance?

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• Implementing list position locator in C++?

  - by jfrazier

  I am writing a basic Graph API in C++ (I know libraries already exist, but I am doing it for the practice/experience). The structure is basically that of an adjacency list representation. So there are Vertex objects and Edge objects, and the Graph class contains: list<Vertex *> vertexList list<Edge *> edgeList Each Edge object has two Vertex* members representing its endpoints, and each Vertex object has a list of Edge* members representing the edges incident to the Vertex. All this is quite standard, but here is my problem. I want to be able to implement deletion of Edges and Vertices in constant time, so for example each Vertex object should have a Locator member that points to the position of its Vertex* in the vertexList. The way I first implemented this was by saving a list::iterator, as follows: vertexList.push_back(v); v->locator = --vertexList.end(); Then if I need to delete this vertex later, then rather than searching the whole vertexList for its pointer, I can call: vertexList.erase(v->locator); This works fine at first, but it seems that if enough changes (deletions) are made to the list, the iterators will become out-of-date and I get all sorts of iterator errors at runtime. This seems strange for a linked list, because it doesn't seem like you should ever need to re-allocate the remaining members of the list after deletions, but maybe the STL does this to optimize by keeping memory somewhat contiguous? In any case, I would appreciate it if anyone has any insight as to why this happens. Is there a standard way in C++ to implement a locator that will keep track of an element's position in a list without becoming obsolete? Much thanks, Jeff

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• Swing GUI using JNI crashes

  - by Div

  Hi, A java swing application(GUI) using JNI code to communicate with native C code. The Swing application launches properly and works fine. The GUI is used to start some customized system level tests(io,memory,cpu) and show their progress. The tests have to be left running at-least overnight to get the results. But, the next morning, GUI crashes and throws following message. Any pointers on source of the issue will be greatly appreciated. Java version: java 1.5 / java 1.6 OS: Solaris 10. Thanks, Div =============MESSAGES================== # uname -a SunOS Generic_127127-11 sun4v sparc SUNW, # # # # An unexpected error has been detected by HotSpot Virtual Machine: # # SIGSEGV (0xb) at pc=0xff268924, pid=9473, tid=272 # # Java VM: Java HotSpot(TM) Server VM (1.5.0_14-b03 mixed mode) # Problematic frame: # C [libc.so.1+0x68924] strstr+0x20 # # An error report file with more information is saved as hs_err_pid9473.log # # If you would like to submit a bug report, please visit: # HotSpot Virtual Machine Error Reporting Page # ============================= Another machine: # A fatal error has been detected by the Java Runtime Environment: # # SIGSEGV (0xb) at pc=0xff231fd0, pid=1406, tid=180 # # JRE version: 6.0_18-b07 # Java VM: Java HotSpot(TM) Server VM (16.0-b13 mixed mode solaris-sparc ) # Problematic frame: # C [libc.so.1+0x31fd0] strcpy+0x70 # # An error report file with more information is saved as: # /usr/sunvts/bin/hs_err_pid1406.log #

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• activemessaging with stomp and activemq.prefetchSize=1

  - by Clint Miller

  I have a situation where I have a single activemq broker with 2 queues, Q1 and Q2. I have two ruby-based consumers using activemessaging. Let's call them C1 and C2. Both consumers subscribe to each queue. I'm setting activemq.prefetchSize=1 when subscribing to each queue. I'm also setting ack=client. Consider the following sequence of events: 1) A message that triggers a long-running job is published to queue Q1. Call this M1. 2) M1 is dispatched to consumer C1, kicking off a long operation. 3) Two messages that trigger short jobs are published to queue Q2. Call these M2 and M3. 4) M2 is dispatched to C2 which quickly runs the short job. 5) M3 is dispatched to C1, even though C1 is still running M1. It's able to dispatch to C1 because prefetchSize=1 is set on the queue subscription, not on the connection. So the fact that a Q1 message has already been dispatched doesn't stop one Q2 message from being dispatched. Since activemessaging consumers are single-threaded, the net result is that M3 sits and waits on C1 for a long time until C1 finishes processing M1. So, M3 is not processed for a long time, despite the fact that consumer C2 is sitting idle (since it quickly finishes with message M2). Essentially, whenever a long Q1 job is run and then a whole bunch of short Q2 jobs are created, exactly one of the short Q2 jobs gets stuck on a consumer waiting for the long Q1 job to finish. Is there a way to set prefetchSize at the connection level rather than at the subscription level? I really don't want any messages dispatched to C1 while it is processing M1. The other alternative is that I could create a consumer dedicated to processing Q1 and then have other consumers dedicated to processing Q2. But, I'd rather not do that since Q1 messages are infrequent--Q1's dedicated consumers would sit idle most of the day tying up memory.

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• How to optimize Conway's game of life for CUDA?

  - by nlight

  I've written this CUDA kernel for Conway's game of life: global void gameOfLife(float* returnBuffer, int width, int height) { unsigned int x = blockIdx.x*blockDim.x + threadIdx.x; unsigned int y = blockIdx.y*blockDim.y + threadIdx.y; float p = tex2D(inputTex, x, y); float neighbors = 0; neighbors += tex2D(inputTex, x+1, y); neighbors += tex2D(inputTex, x-1, y); neighbors += tex2D(inputTex, x, y+1); neighbors += tex2D(inputTex, x, y-1); neighbors += tex2D(inputTex, x+1, y+1); neighbors += tex2D(inputTex, x-1, y-1); neighbors += tex2D(inputTex, x-1, y+1); neighbors += tex2D(inputTex, x+1, y-1); __syncthreads(); float final = 0; if(neighbors < 2) final = 0; else if(neighbors 3) final = 0; else if(p != 0) final = 1; else if(neighbors == 3) final = 1; __syncthreads(); returnBuffer[x + y*width] = final; } I am looking for errors/optimizations. Parallel programming is quite new to me and I am not sure if I get how to do it right. The rest of the app is: Memcpy input array to a 2d texture inputTex stored in a CUDA array. Output is memcpy-ed from global memory to host and then dealt with. As you can see a thread deals with a single pixel. I am unsure if that is the fastest way as some sources suggest doing a row or more per thread. If I understand correctly NVidia themselves say that the more threads, the better. I would love advice on this on someone with practical experience.

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• How many users are sufficient to make a heavy load for web application

  - by galymzhan

  I have a web application, which has been suffering high load recent days. The application runs on single server which has 8-core Intel CPU and 4gb of RAM. Software: Drupal 5 (Apache 2, PHP5, MySQL5) running on Debian. After reaching 500 authenticated and 200 anonymous users (simultaneous), the application drastically decreases its performance up to total failure. The biggest load comes from authenticated users, who perform activities, causing insert/update/deletes on db. I think mysql is a bottleneck. Is it normal to slow down on such number of users? EDIT: I forgot to mention that I did some kind of profiling. I runned commands top, htop and they showed me that all memory was being used by MySQL! After some time MySQL starts to perform terribly slow, site goes down, and we have to restart/stop apache to reduce load. Administrators said that there was about 200 active mysql connections at that moment. The worst point is that we need to solve this ASAP, I can't do deep profiling analysis/code refactoring, so I'm considering 2 ways: my tables are MyIsam, I heard they use table-level locking which is very slow, is it right? could I change it to Innodb without worry? what if I take MySQL, and move it to dedicated machine with a lot of RAM?

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• How to code a 'Next in Results' within search results in PHP

  - by thebluefox

  Right, bit of a head scratcher, although I've got a feeling there's an obvious answer and I'm just not seeing the wood for the trees. Baiscally, using Solr as a search engine for my site, bringing back 15 results per page. When you click on a result, you get a detail page, that has a "Next in Results" link on it, which obviously forwards you on to the next result. Whats the best way of doing this? I've come up with a few solutions but they're either too inpractical or just don't work. I could store all the ids in a session array, then grab the one after the current one and put that in the link. But with possibly hundreds/thousands of results, the memory that array would need, and the performance hit of dealing with it isn't practical. I could take the same approach and put it into the db, but I'll still have to deal with a potentially huge array when I grab them out of the db. Or; I could do the search again, only returning the id's, and grab the one after the one we're currently looking at. I think this could be the best option? Although it does seem kind of messy, namely because of when I have to select the id thats on a different 'page' (ie the 16th, 31st etc result). Unless I pass through where it was in the results, and select from there, but that still doesn't seem like the right way to do it. I'm really sorry if this is just complete nonsense, any help is massively appreciated as always, Cheers guys!

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• What does the windbg command "kd" do?

  - by Oskar

  I ran kd by mistake and got some output that inteerested me, a reference to a line of code in my module that I can't see on the call stack of any thread. The lines weren't the beginnning of the method so I don't think the reference is to a function pointer, but possibly the result of an exception being stored in memory??? Of course, that happens to be what I'm looking for... Update: The stack trace of the exception is: 0:000> kb *** Stack trace for last set context - .thread/.cxr resets it ChildEBP RetAddr Args to Child 0174f168 734ea84f 2cb9e950 00000000 2cb9e950 kernel32!LoadTimeZoneInformation+0x2b 0174f1c4 734ead92 00000022 00000001 000685d0 msvbvm60! RUN_INSTMGR::ExecuteInitTerm+0x178 0174f1f8 734ea9ee 00000000 0000002f 2dbc2abc msvbvm60! RUN_INSTMGR::CreateObjInstanceWithParts+0x1e4 0174f278 7350414e 2cb9e96c 00000000 0174f2f0 msvbvm60! RUN_INSTMGR::CreateObjInstance+0x14d 0174f2e4 734fa071 00000000 2cb9e96c 0174f2fc msvbvm60!RcmConstructObjectInstance+0x75 0174f31c 00976ef1 2cb9e950 00591bc0 0174fddc msvbvm60!__vbaNew+0x21 and into our code (create a new Form derived class) the dds output: 0:000> dds esp-0x40 esp+0x100 0174f05c 00000000 0174f060 00000000 0174f064 00000000 0174f068 00000000 0174f06c 00000000 0174f070 00000000 0174f074 00000000 0174f078 00000000 0174f07c 00000000 0174f080 00000000 0174f084 00000000 0174f088 00000000 0174f08c 00000000 0174f090 00000000 0174f094 00000000 0174f098 00000000 0174f09c 007f4f9b ourDll!formDerivedClass::Form_Initialize+0x10b [C:\Buildbox\formDerivedClass.frm @ 1452] etc which seems to indicate that Initialize is being called even though it isn't on the stack trace of either this exception or any of the threads. As suggested, it might all be a mismatch between pdbs and dlls, but it seems a coincidence that we end up in the right classes and methods

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• How do I rewrite a for loop with a shared dependency using actors

  - by Thomas Rynne

  We have some code which needs to run faster. Its already profiled so we would like to make use of multiple threads. Usually I would setup an in memory queue, and have a number of threads taking jobs of the queue and calculating the results. For the shared data I would use a ConcurrentHashMap or similar. I don't really want to go down that route again. From what I have read using actors will result in cleaner code and if I use akka migrating to more than 1 jvm should be easier. Is that true? However, I don't know how to think in actors so I am not sure where to start. To give a better idea of the problem here is some sample code: case class Trade(price:Double, volume:Int, stock:String) { def value(priceCalculator:PriceCalculator) = (priceCalculator.priceFor(stock)-> price)*volume } class PriceCalculator { def priceFor(stock:String) = { Thread.sleep(20)//a slow operation which can be cached 50.0 } } object ValueTrades { def valueAll(trades:List[Trade], priceCalculator:PriceCalculator):List[(Trade,Double)] = { trades.map { trade => (trade,trade.value(priceCalculator)) } } def main(args:Array[String]) { val trades = List( Trade(30.5, 10, "Foo"), Trade(30.5, 20, "Foo") //usually much longer ) val priceCalculator = new PriceCalculator val values = valueAll(trades, priceCalculator) } } I'd appreciate it if someone with experience using actors could suggest how this would map on to actors.

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• How to efficiently convert String, integer, double, datetime to binary and vica versa?

  - by Ben

  Hi, I'm quite new to C# (I'm using .NET 4.0) so please bear with me. I need to save some object properties (their properties are int, double, String, boolean, datetime) to a file. But I want to encrypt the files using my own encryption, so I can't use FileStream to convert to binary. Also I don't want to use object serialization, because of performance issues. The idea is simple, first I need to somehow convert objects (their properties) to binary (array), then encrypt (some sort of xor) the array and append it to the end of the file. When reading first decrypt the array and then somehow convert the binary array back to object properties (from which I'll generate objects). I know (roughly =) ) how to convert these things by hand and I could code it, but it would be useless (too slow). I think the best way would be just to get properties' representation in memory and save that. But I don't know how to do it using C# (maybe using pointers?). Also I though about using MemoryStream but again I think it would be inefficient. I am thinking about class Converter, but it does not support toByte(datetime) (documentation says it always throws exception). For converting back I think the only options is class Converter. Note: I know the structure of objects and they will not change, also the maximum String length is also known. Thank you for all your ideas and time. EDIT: I will be storing only parts of objects, in some cases also parts of different objects (a couple of properties from one object type and a couple from another), thus I think that serialization is not an option for me.

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• Building a control-flow graph from an AST with a visitor pattern using Java

  - by omegatai

  Hi guys, I'm trying to figure out how to implement my LEParserCfgVisitor class as to build a control-flow graph from an Abstract-Syntax-Tree already generated with JavaCC. I know there are tools that already exist, but I'm trying to do it in preparation for my Compilers final. I know I need to have a data structure that keeps the graph in memory, and I want to be able to keep attributes like IN, OUT, GEN, KILL in each node as to be able to do a control-flow analysis later on. My main problem is that I haven't figured out how to connect the different blocks together, as to have the right edge between each blocks depending on their nature: branch, loops, etc. In other words, I haven't found an explicit algorithm that could help me build my visitor. Here is my empty Visitor. You can see it works on basic langage expressions, like if, while and basic operations (+,-,x,^,...) public class LEParserCfgVisitor implements LEParserVisitor { public Object visit(SimpleNode node, Object data) { return data; } public Object visit(ASTProgram node, Object data) { data = node.childrenAccept(this, data); return data; } public Object visit(ASTBlock node, Object data) { } public Object visit(ASTStmt node, Object data) { } public Object visit(ASTAssignStmt node, Object data) { } public Object visit(ASTIOStmt node, Object data) { } public Object visit(ASTIfStmt node, Object data) { } public Object visit(ASTWhileStmt node, Object data) { } public Object visit(ASTExpr node, Object data) { } public Object visit(ASTAddExpr node, Object data) { } public Object visit(ASTFactExpr node, Object data) { } public Object visit(ASTMultExpr node, Object data) { } public Object visit(ASTPowerExpr node, Object data) { } public Object visit(ASTUnaryExpr node, Object data) { } public Object visit(ASTBasicExpr node, Object data) { } public Object visit(ASTFctExpr node, Object data) { } public Object visit(ASTRealValue node, Object data) { } public Object visit(ASTIntValue node, Object data) { } public Object visit(ASTIdentifier node, Object data) { } } Can anyone give me a hand? Thanks!

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• Why are references compacted inside Perl lists?

  - by parkan

  Putting a precompiled regex inside two different hashes referenced in a list: my @list = (); my $regex = qr/ABC/; push @list, { 'one' => $regex }; push @list, { 'two' => $regex }; use Data::Dumper; print Dumper(\@list); I'd expect: $VAR1 = [ { 'one' => qr/(?-xism:ABC)/ }, { 'two' => qr/(?-xism:ABC)/ } ]; But instead we get a circular reference: $VAR1 = [ { 'one' => qr/(?-xism:ABC)/ }, { 'two' => $VAR1->[0]{'one'} } ]; This will happen with indefinitely nested hash references and shallowly copied $regex. I'm assuming the basic reason is that precompiled regexes are actually references, and references inside the same list structure are compacted as an optimization (\$scalar behaves the same way). I don't entirely see the utility of doing this (presumably a reference to a reference has the same memory footprint), but maybe there's a reason based on the internal representation Is this the correct behavior? Can I stop it from happening? Aside from probably making GC more difficult, these circular structures create pretty serious headaches. For example, iterating over a list of queries that may sometimes contain the same regular expression will crash the MongoDB driver with a nasty segfault (see https://rt.cpan.org/Public/Bug/Display.html?id=58500)

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• Implementing java FixedTreadPool status listener

  - by InsertNickHere

  Hi there, it's about an application which is supposed to process (VAD, Loudness, Clipping) a lot of soundfiles (e.g. 100k). At this time, I create as many worker threads (callables) as I can put into memory, and then run all with a threadPool.invokeAll(), write results to file system, unload processed files and continue at step 1. Due to the fact it's an app with a GUI, i don't want to user to feel like the app "is not responding" while processing all soundfiles. (which it does at this time cause invokeAll is blocking). Im not sure what is a "good" way to fix this. It shall not be possible for the user to do other things while processing, but I'd like to show a progress bar like "10 of 100000 soundfiles are done". So how do I get there? Do I have to create a "watcher thread", so that every worker hold a callback on it? I'm quite new to multi threading, and don't get the idea of such a mechanisem.. If you need to know: I'm using SWT/JFace. Regards, InsertNickHere

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• Getting wierd issue with TO_NUMBER function in Oracle

  - by Fazal

  I have been getting an intermittent issue when executing to_number function in the where clause on a varchar2 column if number of records exceed a certain number n. I used n as there is no exact number of records on which it happens. On one DB it happens after n was 1 million on another when it was 0.1. million. E.g. I have a table with 10 million records say Table Country which has field1 varchar2 containing numberic data and Id If I do a query as an example select * from country where to_number(field1) = 23 and id 1 and id < 100000 This works But if i do the query select * from country where to_number(field1) = 23 and id 1 and id < 100001 It fails saying invalid number Next I try the query select * from country where to_number(field1) = 23 and id 2 and id < 100001 It works again As I only got invalid number it was confusing, but in the log file it said Memory Notification: Library Cache Object loaded into SGA Heap size 3823K exceeds notification threshold (2048K) KGL object name :with sqlplan as ( select c006 object_owner, c007 object_type,c008 object_name from htmldb_collections where COLLECTION_NAME='HTMLDB_QUERY_PLAN' and c007 in ('TABLE','INDEX','MATERIALIZED VIEW','INDEX (UNIQUE)')), ws_schemas as( select schema from wwv_flow_company_schemas where security_group_id = :flow_security_group_id), t as( select s.object_owner table_owner,s.object_name table_name, d.OBJECT_ID from sqlplan s,sys.dba_objects d It seems its related to SGA size, but google did not give me much help on this. Does anyone have any idea about this issue with TO_NUMBER or oracle functions for large data?

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• Want to display a 3D model on the iPhone: how to get started?

  - by JeremyReimer

  I want to display and rotate a single 3D model, preferably textured, on the iPhone. Doesn't have to zoom in and out, or have a background, or anything. I have the following: an iPhone a MacBook the iPhone SDK Blender My knowledge base: I can make 3D models in various 3D programs (I'm most comfortable with 3D Studio Max, which I once took a course on, but I've used others) General knowledge of procedural programming from years ago (QuickBasic - I'm old!) Beginner's knowledge of object-oriented programming from going through simple Java and C# tutorials (Head Start C# book and my wife's intro to OOP course that used Java) I have managed to display a 3D textured model and spin it using a tutorial in C# I got off the net (I didn't just copy and paste, I understand basically how it works) and the XNA game development library, using Visual Studio on Windows. What I do not know: Much about Objective C Anything about OpenGL or OpenGL ES, which the iPhone apparently uses Anything about XCode My main problem is that I don't know where to start! All the iPhone books I found seem to be about creating GUI applications, not OpenGL apps. I found an OpenGL book but I don't know how much, if any, applies to iPhone development. And I find the Objective C syntax somewhat confusing, with the weird nested method naming, things like "id" that don't make sense, and the scary thought that I have to do manual memory management. Where is the best place to start? I couldn't find any tutorials for this sort of thing, but maybe my Google-Fu is weak. Or maybe I should start with learning Objective C? I know of books like Aaron Hillgrass', but I've also read that they are outdated and much of the sample code doesn't work on the iPhone SDK, plus it seems geared towards the Model-View-Controller paradigm which doesn't seem that suited for 3D apps. Basically I'm confused about what my first steps should be.

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