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• UML Modelling in C++Builder 2010 Professional

  - by Gordon Brandly

  I'd like to do some basic class diagram UML models in the Pro version of C++Builder 2010. Embarcadero has a C++Builder Features Matrix document, one line of which says "UML Code Visualization – at any time, get a UML model view of your source code" and has a check in the "Professional" column of that table -- I assume this means it should be available to me. Yet, when I open an existing project and do a View | Model View, there's nothing in the Model View window. The only diagram I can find is on the Graph tab of the C++ Class Explorer. I wouldn't call that a UML diagram myself -- is that what Embarcadero is referring to? Embarcadero's table shows that many UML diagrams are not available in Pro, but it looks to me like Class Diagrams should be available. Other lines in that same table indicate that both "Full two-way class diagrams with synchronization between code and diagrams" and "Diagram hyper-linking and annotations" are also supposed to be available in Pro. The Class Explorer graph is one-way only as far as I can tell, so I hope they're referring to something else I haven't been able to find so far. Thanks for any insight into this.

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• Java Random Slowdowns on Mac OS cont'd

  - by javajustice

  I asked this question a few weeks ago, but I'm still having the problem and I have some new hints. The original question is here: http://stackoverflow.com/questions/1651887/java-random-slowdowns-on-mac-os Basically, I have a java application that splits a job into independent pieces and runs them in separate threads. The threads have no synchronization or shared memory items. The only resources they do share are data files on the hard disk, with each thread having an open file channel. Most of the time it runs very fast, but occasionally it will run very slow for no apparent reason. If I attach a CPU profiler to it, then it will start running quickly again. If I take a CPU snapshot, it says its spending most of its time in "self time" in a function that doesn't do anything except check a few (unshared unsynchronized) booleans. I don't know how this could be accurate because 1, it makes no sense, and 2, attaching the profiler seems to knock the threads out of whatever mode they're in and fix the problem. Also, regardless of whether it runs fast or slow, it always finishes and gives the same output, and it never dips in total cpu usage (in this case ~1500%), implying that the threads aren't getting blocked. I have tried different garbage collectors, different sizings the parts of the memory space, writing data output to non-raid drives, and putting all data output in threads separate the main worker threads. Does anyone have any idea what kind of problem this could be? Could it be the operating system (OS X 10.6.2) ? I have not been able to duplicate it on a windows machine, but I don't have one with a similar hardware configuration.

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• Does SetFileBandwidthReservation affect memory-mapped file performance?

  - by Ghostrider

  Does this function affect Memory-mapped file performance? Here's the problem I need to solve: I have two applications competing for disk access: "reader" and "updater". Whole system runs on Windows Server 2008 R2 x64 "Updater" constantly accesses disk in a linear manner, updating data. They system is set up in such a way that updater always has infinite data to update. Consider that it is constantly approximating a solution of a huge set of equations that takes up entire 2TB disk drive. Updater uses ReadFile and WriteFile to process data in a linear fashion. "Reader" is occasionally invoked by user to get some pieces of data. Usually user would read several 4kb blocks from the drive and stop. Occasionally user needs to read up to 100mb sequentially. In exceptional cases up to several gigabytes. Reader maps files to memory to get data it needs. What I would like to achieve is for "reader" to have absolute priority so that "updater" would completely stop if needed so that "reader" could get the data user needs ASAP. Is this problem solvable by using SetPriorityClass and SetFileBandwidthReservation calls? I would really hate to put synchronization login in "reader" and "updater" and rather have the OS take care of priorities.

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• Synchronizing screencasting (ffmpeg) and capturing from the webcam (OpenCV)

  - by lyuba

  As from my previous questions, I am trying to build a simple eye tracker. Decided to start from a Linux version (run Ubuntu). To complete this task one should organize screencasting and webcam capturing in such way that frames from both streams exactly match each other and there is the same number of frames in each of them totally. Screencasting fsp fully depends on the camera's fsp, so each time we get the image from the webcam we can potentially grab a screen frame and stay happy. However, all the tools for the fast screencasting, like ffmpeg, for example, return the .avi file as the result and require the fsp already known to be started. From the other side, tools like Java+Robot or ImageMagick seem to require around 20ms to return the .jpg screenshot, which is pretty slow for the task. But they may be requested right after each time the webcam frame is grabbed and provide the needed synchronization. So the sub-questions are: 1. Does the USD camera's frame rate vary during a single session? 2. Are there any tools which provide fast screencasting frame by frame? 3. Is there any way to make ffmpeg push a new frame to the .avi file only when program initiates this request? For my task I may either use C++ or Java. I am, actually, an interface designer, not the driver programmer, and this task seems to be pretty low-level. I would be grateful for any suggestion and tip!

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• .net real time stream processing - needed huge and fast RAM buffer

  - by mack369

  The application I'm developing communicates with an digital audio device, which is capable of sending 24 different voice streams at the same time. The device is connected via USB, using FTDI device (serial port emulator) and D2XX Drivers (basic COM driver is to slow to handle transfer of 4.5Mbit). Basically the application consist of 3 threads: Main thread - GUI, control, ect. Bus reader - in this thread data is continuously read from the device and saved to a file buffer (there is no logic in this thread) Data interpreter - this thread reads the data from file buffer, converts to samples, does simple sample processing and saves the samples to separate wav files. The reason why I used file buffer is that I wanted to be sure that I won't loose any samples. The application doesn't use recording all the time, so I've chosen this solution because it was safe. The application works fine, except that buffered wave file generator is pretty slow. For 24 parallel records of 1 minute, it takes about 4 minutes to complete the recording. I'm pretty sure that eliminating the use of hard drive in this process will increase the speed much. The second problem is that the file buffer is really heavy for long records and I can't clean this up until the end of data processing (it would slow down the process even more). For RAM buffer I need at lest 1GB to make it work properly. What is the best way to allocate such a big amount of memory in .NET? I'm going to use this memory in 2 threads so a fast synchronization mechanism needed. I'm thinking about a cycle buffer: one big array, the Bus Reader saves the data, the Data Interpreter reads it. What do you think about it? [edit] Now for buffering I'm using classes BinaryReader and BinaryWriter based on a file.

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• Extremely high mysqld CPU usage with no active queries

  - by RadarNyan

  I have a VPS running Ubuntu 12.04 LTS with LEMP stack, followed the guide from Linode Library (since I'm using a Linode) to setup, and everything worked fine until now. I don't know what's wrong, but my CPU usage just goes up since a week ago. Today things getting really bad - I got 74% CPU usage so I went check and found that mysqld taking too much CPU usage (somewhere around 30% ~ 80%) So I did some Google Search, tried disable InnoDB, restart mysql, reset ntp / system clock (Isn't this bug supposed to happen more than a year ago?!) and reboot my VPS, nothing helped. Even with mysql processlist empty, I still get mysqld CPU usage very high. I don't know what I missed and have totally no idea, any advice would be appreciated. Thanks in advance. Update: I got these from running "strace mysqld" write(2, "InnoDB: Unable to lock ./ibdata1"..., 44) = 44 write(2, "InnoDB: Check that you do not al"..., 115) = 115 select(0, NULL, NULL, NULL, {1, 0}^[[A^[[A) = 0 (Timeout) fcntl64(3, F_SETLK64, {type=F_WRLCK, whence=SEEK_SET, start=0, len=0}, 0xbfa496f8) = -1 EAGAIN (Resource temporarily unavailable) hum... I did tried to disable InnoDB and it didn't fix this problem. Any idea? Update2: # ps -e | grep mysqld 13099 ? 00:00:20 mysqld then use "strace -p 13099", the following lines appears repeatedly: fcntl64(12, F_GETFL) = 0x2 (flags O_RDWR) fcntl64(12, F_SETFL, O_RDWR|O_NONBLOCK) = 0 accept(12, {sa_family=AF_FILE, NULL}, [2]) = 14 fcntl64(12, F_SETFL, O_RDWR) = 0 getsockname(14, {sa_family=AF_FILE, path="/var/run/mysqld/mysqld.sock"}, [30]) = 0 fcntl64(14, F_SETFL, O_RDONLY) = 0 fcntl64(14, F_GETFL) = 0x2 (flags O_RDWR) setsockopt(14, SOL_SOCKET, SO_RCVTIMEO, "\36\0\0\0\0\0\0\0", 8) = 0 setsockopt(14, SOL_SOCKET, SO_SNDTIMEO, "<\0\0\0\0\0\0\0", 8) = 0 fcntl64(14, F_SETFL, O_RDWR|O_NONBLOCK) = 0 setsockopt(14, SOL_IP, IP_TOS, [8], 4) = -1 EOPNOTSUPP (Operation not supported) futex(0xb786a584, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0xb786a580, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 1}) = 1 futex(0xb7869998, FUTEX_WAKE_PRIVATE, 1) = 1 poll([{fd=10, events=POLLIN}, {fd=12, events=POLLIN}], 2, -1) = 1 ([{fd=12, revents=POLLIN}]) er... now I totally don't get it x_x help

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• Canceling a WSK I/O operation when driver is unloading

  - by eaducac

  I've been learning how to write drivers with the Windows DDK recently. After creating a few test drivers experimenting with system threads and synchronization, I decided to step it up a notch and write a driver that actually does something, albeit something useless. Currently, my driver connects to my other computer using Winsock Kernel and just loops and echoes back whatever I send to it until it gets the command "exit", which causes it to break out of the loop. In my loop, after I call WskReceive() to get some data from the other computer, I use KeWaitForMultipleObjects() to wait for either of two SynchronizationEvents. BlockEvent gets set by my IRP's CompletionRoutine() to let my thread know that it's received some data from the socket. EndEvent gets set by my DriverUnload() routine to tell the thread that it's being unloaded and it needs to terminate. When I send the "exit" command, the thread terminates with no problems, and I can safely unload the driver afterward. If I try to stop the driver while it's still waiting on data from the other computer, however, it blue screens with the error DRIVER_UNLOADED_WITHOUT_CANCELLING_PENDING_OPERATIONS. After I get the EndEvent but before I exit the loop, I've tried canceling the IRP with IoCancelIrp() and completing it with IoCompleteRequest(), but both of those give me DRIVER_IRQL_NOT_LESS_OR_EQUAL errors. I then tried calling WskDisconnect(), hoping that would cause the receive operation to complete, but that took me back to the CANCELLING_PENDING_OPERATIONS error. How do I cancel my pending I/O operation from my WSK socket at the IRQL I'm running at when the driver is unloaded?

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• Why does my PC successfully boot only when unplugged for more than a few minutes?

  - by philg

  I have an HP Pavilion Elite desktop computer, model HPE-490t. I like it because it didn’t cost too much, boots itself from an SSD, came with 16 GB of RAM, and has 6 CPU cores for editing video and camera RAW images. It has one behavioral quirk that I cannot explain, however. The recent power interruptions here in the Northeast got the machine into a state where it could not be restarted. It would power up for a second or two, shut down, and then power up again, never being able to get to the point of showing anything on the monitor. I unplugged it for about 10 seconds and plugged it back in. Same behavior (fails to boot). I unplugged it and walked away for an hour, then plugged it back in and it worked perfectly! I think something similar happened after installing a second hard disk drive into this machine. So the question is why does the computer behave differently depending on how long it has been unplugged? Where is energy stored that affects the machine’s ability to boot? Capacitors in the power supply? Battery on the motherboard (there is one for the clock, but that wouldn’t be exhausted by being unplugged for an hour, I don’t think)?

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• Atomic swap in GNU C++

  - by Steve

  I want to verify that my understanding is correct. This kind of thing is tricky so I'm almost sure I am missing something. I have a program consisting of a real-time thread and a non-real-time thread. I want the non-RT thread to be able to swap a pointer to memory that is used by the RT thread. From the docs, my understanding is that this can be accomplished in g++ with: // global Data *rt_data; Data *swap_data(Data *new_data) { #ifdef __GNUC__ // Atomic pointer swap. Data *old_d = __sync_lock_test_and_set(&rt_data, new_data); #else // Non-atomic, cross your fingers. Data *old_d = rt_data; rt_data = new_data; #endif return old_d; } This is the only place in the program (other than initial setup) where rt_data is modified. When rt_data is used in the real-time context, it is copied to a local pointer. For old_d, later on when it is sure that the old memory is not used, it will be freed in the non-RT thread. Is this correct? Do I need volatile anywhere? Are there other synchronization primitives I should be calling? By the way I am doing this in C++, although I'm interested in whether the answer differs for C. Thanks ahead of time.

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• Minimal deployment of couchdb on windows

  - by MartinStettner

  Hi, I'd like to use couchdb for a client-only application on Windows (the document-oriented structure and the synchronization features would be perfect for me). There is a Windows installer package here, but the installer itself has about 45 MB, when installed it takes more than 100 MB on my HD. This is far to much for my (relatively small) application. I noticed that there are a lot of "src" directories in the couchdb/lib subdirs. I've been experimenting with removing some of them and it didn't seem to break the system. Now I'm wondering what would be the "minimal" set of files (preferably binary-only) that would be needed in order to run a local couchdb server. Are there already any efforts to create such a deployment-friendly installer? Or could anyone give some (even very general) hints how to create it? How much disk space would be minimally required for such an installation? Needless to say that I'm not at all familiar with neither the couchdb internals nor the Erlang system :). But perhaps I could figure out if I got some direction (or I could stop trying if someone told me that this would be impossible or didn't make sense at all ...) Thanks anyway!

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• How can I get Haproxy to not log local requests?

  - by coneybeare

  I am trying to clean out some of the log clutter from my machines and am starting by removing requests that are generated from the server themselves. I have cache warmers running around the clock and I don't want these polluting the logs. I was able to get apache to stop logging local requests by adding a dontlog for the local IP: SetEnvIf Remote_Addr "RE\.DA\.CT\.ED" dontlog CustomLog "|logger -p local3.info -t http" combined env=!dontlog and now I am looking for something similar to put in a configuration for the Haproxy log. How can I prevent 127.0.0.1 requests from writing to the Haproxy log? UPDATE: 2/15/11 I use the excellent loggly service to pull out logs in the cloud, but I am seeing tons of logs like this: 2011 Feb 15 06:09:42.000 ip-10-251-194-96 http: RE.DA.CT.ED - - [15/Feb/2011:06:09:42 -0500] "HEAD /search/Nevad/predictive/txt HTTP/1.0" 200 - "-" "Wget/1.10.2 (Red Hat modified)" 2011 Feb 15 06:09:42.000 127.0.0.1 haproxy[10390]: 127.0.0.1:58408 [15/Feb/2011:06:09:42] www i-5dd7a331.0 0/0/0/8/8 200 210 - - --NI 0/0/0 0/0 "HEAD /search/Nevad/predictive/txt HTTP/1.1" and I want them gone. This question focuses on how to remove that haproxy log line from writing to the server side log in the first place.

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• Is Stream.Write thread-safe?

  - by Mike Spross

  I'm working on a client/server library for a legacy RPC implementation and was running into issues where the client would sometimes hang when waiting to a receive a response message to an RPC request message. It turns out the real problem was in my message framing code (I wasn't handling message boundaries correctly when reading data off the underlying NetworkStream), but it also made me suspicious of the code I was using to send data across the network, specifically in the case where the RPC server sends a large amount of data to a client as the result of a client RPC request. My send code uses a BinaryWriter to write a complete "message" to the underlying NetworkStream. The RPC protocol also implements a heartbeat algorithm, where the RPC server sends out PING messages every 15 seconds. The pings are sent out by a separate thread, so, at least in theory, a ping can be sent while the server is in the middle of streaming a large response back to a client. Suppose I have a Send method as follows, where stream is a NetworkStream: public void Send(Message message) { //Write the message to a temporary stream so we can send it all-at-once MemoryStream tempStream = new MemoryStream(); message.WriteToStream(tempStream); //Write the serialized message to the stream. //The BinaryWriter is a little redundant in this //simplified example, but here because //the production code uses it. byte[] data = tempStream.ToArray(); BinaryWriter bw = new BinaryWriter(stream); bw.Write(data, 0, data.Length); bw.Flush(); } So the question I have is, is the call to bw.Write (and by implication the call to the underlying Stream's Write method) atomic? That is, if a lengthy Write is still in progress on the sending thread, and the heartbeat thread kicks in and sends a PING message, will that thread block until the original Write call finishes, or do I have to add explicit synchronization to the Send method to prevent the two Send calls from clobbering the stream?

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• How to display escaped characters in tmux status bar

  - by walrus

  i am running tmux from a tty on an embedded linux device. (NOT a terminal emulator) because the screen is rather small, i want to add some "icons" to the tmux status bar. to achieve this, i have simply created a font with the appropriate glyphs for things like battery, or wifi. i can load the font, and display the characters with calls that use an escape to the line drawing characters like so: echo -e "\xe\234\xf" \xe escapes me into line drawing character mode, \234 is my created character, and \xf returns me to normal character mode so my terminal doesnt start getting goofy. this works perfectly if i enter the command at the terminal whether tmux is started or not. the issue arises if i then try to use it in my ~/.tmux.conf file for the status bar. i currently have a line like this: set -g status-right "#(echo -e "\xe\234\xf") #(/script/to/output/powerlevel) this simply outputs \xe\234\xf powerlevel this goes the same if i try printf over echo. this is the output i would expect to get on the terminal if i made the call without passing -e to echo, or without enclosing the statement with quotes. i then decided to wrap the calls to the echo or printf in a shell script. again, the script works when called from the terminal, but not in tmux's status bar. now i get the unprintable character "?" instead of my icon, like this: ? powerlevel this is what i would expect if i did not use the line drawing escapes previously mentioned above, or if i tried to copy and paste the character as text using tmux. in addition, the calling of these character scripts screws up the rest of my status-right, as the clock has about 6 digits for minutes when it is called (though it correctly only updates two of them). how can i make tmux respect the escape characters? any help or insight is greatly appreciated.

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• C++ Switch won't compile with externally defined variable used as case

  - by C Nielsen

  I'm writing C++ using the MinGW GNU compiler and the problem occurs when I try to use an externally defined integer variable as a case in a switch statement. I get the following compiler error: "case label does not reduce to an integer constant". Because I've defined the integer variable as extern I believe that it should compile, does anyone know what the problem may be? Below is an example: test.cpp #include <iostream> #include "x_def.h" int main() { std::cout << "Main Entered" << std::endl; switch(0) { case test_int: std::cout << "Case X" << std::endl; break; default: std::cout << "Case Default" << std::endl; break; } return 0; } x_def.h extern const int test_int; x_def.cpp const int test_int = 0; This code will compile correctly on Visual C++ 2008. Furthermore a Montanan friend of mine checked the ISO C++ standard and it appears that any const-integer expression should work. Is this possibly a compiler bug or have I missed something obvious? Here's my compiler version information: Reading specs from C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/specs Configured with: ../gcc-3.4.5-20060117-3/configure --with-gcc --with-gnu-ld --with-gnu-as --host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls --enable-languages=c,c++,f77,ada,objc,java --disable-win32-registry --disable-shared --enable-sjlj-exceptions --enable-libgcj --disable-java-awt --without-x --enable-java-gc=boehm --disable-libgcj-debug --enable-interpreter --enable-hash-synchronization --enable-libstdcxx-debug Thread model: win32 gcc version 3.4.5 (mingw-vista special r3)

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• Thread Safety of C# List<T> for readers

  - by ILIA BROUDNO

  I am planning to create the list once in a static constructor and then have multiple instances of that class read it (and enumerate through it) concurrently without doing any locking. In this article http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx MS describes the issue of thread safety as follows: Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe. A List can support multiple readers concurrently, as long as the collection is not modified. Enumerating through a collection is intrinsically not a thread-safe procedure. In the rare case where an enumeration contends with one or more write accesses, the only way to ensure thread safety is to lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization. The "Enumerating through a collection is intrinsically not a thread-safe procedure." Statement is what worries me. Does this mean that it is thread safe for readers only scenario, but as long as you do not use enumeration? Or is it safe for my scenario?

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• How to interrupt a thread performing a blocking socket connect?

  - by Jason R

  I have some code that spawns a pthread that attempts to maintain a socket connection to a remote host. If the connection is ever lost, it attempts to reconnect using a blocking connect() call on its socket. Since the code runs in a separate thread, I don't really care about the fact that it uses the synchronous socket API. That is, until it comes time for my application to exit. I would like to perform some semblance of an orderly shutdown, so I use thread synchronization primitives to wake up the thread and signal for it to exit, then perform a pthread_join() on the thread to wait for it to complete. This works great, unless the thread is in the middle of a connect() call when I command the shutdown. In that case, I have to wait for the connect to time out, which could be a long time. This makes the application appear to take a long time to shut down. What I would like to do is to interrupt the call to connect() in some way. After the call returns, the thread will notice my exit signal and shut down cleanly. Since connect() is a system call, I thought that I might be able to intentionally interrupt it using a signal (thus making the call return EINTR), but I'm not sure if this is a robust method in a POSIX threads environment. Does anyone have any recommendations on how to do this, either using signals or via some other method? As a note, the connect() call is down in some library code that I cannot modify, so changing to a non-blocking socket is not an option.

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• Disadvantages of MySQL Row Locking

  - by Nyxynyx

  I am using row locking (transactions) in MySQL for creating a job queue. Engine used is InnoDB. SQL Query START TRANSACTION; SELECT * FROM mytable WHERE status IS NULL ORDER BY timestamp DESC LIMIT 1 FOR UPDATE; UPDATE mytable SET status = 1; COMMIT; According to this webpage, The problem with SELECT FOR UPDATE is that it usually creates a single synchronization point for all of the worker processes, and you see a lot of processes waiting for the locks to be released with COMMIT. Question: Does this mean that when the first query is executed, which takes some time to finish the transaction before, when the second similar query occurs before the first transaction is committed, it will have to wait for it to finish before the query is executed? If this is true, then I do not understand why the row locking of a single row (which I assume) will affect the next transaction query that would not require reading that locked row? Additionally, can this problem be solved (and still achieve the effect row locking does for a job queue) by doing a UPDATE instead of the transaction? UPDATE mytable SET status = 1 WHERE status IS NULL ORDER BY timestamp DESC LIMIT 1

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• Sudden and frequent hangs on desktop computer: mobo or CPU fault?

  - by djechelon

  I have a desktop computer equipped with an ASUS Crosshair 2 Formula and a Phenom x6 3.2GHz CPU. My problem is that often the computer will hang all of a sudden, completely stopping responding. When that occurs, reset key is inoperative and power button turns the computer off but is unable to turn it back on. I have to physically disconnect power cable. The problem can occur anytime, when I'm booting Windows, when I'm logging in, when I'm listening to a song, when I'm browsing Internet, etc. It always occurs after very few minutes of 3D gameplay I thought it was a video card fault. I had 3 8800GTX so I could try all combinations of them: didn't fix I thought it was a RAM problem: I tried running with only a subset of my DDR2 banks but didn't fix. Almost every time I have to reset and reconfigure BIOS (without AHCI, Win7 won't boot, so I need to restore a few things). If I enable AMD Live, Cool&Quiet or other things from CPU configuration menu I'll be sure that the computer won't reach Windows desktop in 99% of cases (it randomly hangs somewhere in the boot process or even in the BIOS POST). Another interesting thing is that during the POST process the computer always takes unusually long time detecting USB devices (LCD POSTer shows USB INIT), and I've also tried disconnecting all USB devices but didn't take less time to POST BIOS revision is 2702, the latest. Today I found a different behaviour once: during boot screen I got a BSOD with error Stop 0x00000101 A clock interrupt was not received on a secondary processor within the allocated time interval, and this is usually related to overclocking, but I never overclocked my CPU. Judging from the description of my problem, hoping someone had the same and fixed, and since I don't have a spare CPU or motherboard for replacement, I'd like to ask if you think this is a problem with faulty CPU or faulty motherboard, and if I can perform additional tests (I mean software tests because of my lack of spare components) to identify the component to replace.

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• Multi threading in WCF RIA Services

  - by synergetic

  I use WCF RIA Services to update customer database. In domain service: public void UpdateCustomer(Customer customer) { this.ObjectContext.Customers.AttachAsModified(customer); syncCustomer(customer); } After update, a database trigger launches and depending on the columns updated it may insert a new record in CustomerChange table. syncCustomer(customer) method is executed to check for a new record in the CustomerChange table and if found it will create a text file which contains customer information and forwards that file to external system for import. Now this synchronization may take a time so I wanted to execute it in different thread. So: private void syncCustomer(Customer customer) { this.ObjectContext.SaveChanges(); new Thread(() => syncCustomerInfo(customer.CustomerID)) { IsBackground = true }.Start(); } private void syncCustomerInfo(int customerID) { //Thread.Sleep(2000); //does real job here ... ... } The problem is in most cases syncCustomerInfo method cannot find any new CustomerChange record even if it was definitely there. If I force thread sleep then it finds a new record. I also looked Entity Framework events but the only event provided by object context is SavingChanges which occur before changes are saved. Please suggest me what else to try.

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• What is happening in Crockford's object creation technique?

  - by Chris Noe

  There are only 3 lines of code, and yet I'm having trouble fully grasping this: Object.create = function (o) { function F() {} F.prototype = o; return new F(); }; newObject = Object.create(oldObject); (from Prototypal Inheritance) 1) Object.create() starts out by creating an empty function called F. I'm thinking that a function is a kind of object. Where is this F object being stored? Globally I guess. 2) Next our oldObject, passed in as o, becomes the prototype of function F. Function (i.e., object) F now "inherits" from our oldObject, in the sense that name resolution will route through it. Good, but I'm curious what the default prototype is for an object, Object? Is that also true for a function-object? 3) Finally, F is instantiated and returned, becoming our newObject. Is the "new" operation strictly necessary here? Doesn't F already provide what we need, or is there a critical difference between function-objects and non-function-objects? Clearly it won't be possible to have a constructor function using this technique. What happens the next time Object.create() is called? Is global function F overwritten? Surely it is not reused, because that would alter previously configured objects. And what happens if multiple threads call Object.create(), is there any sort of synchronization to prevent race conditions on F?

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• how to diagnose a hard system seizure? Dell+Ubuntu

  - by rob

  I've got Ubuntu 9.10 on a Dell Vostro 420 desktop, a little over a year old, which I use for plain vanilla work stuff (email, web, terminal, text editor). Every now and then, at totally random times, it completely freezes on me. Hard. Mouse and keyboard stop working, cursor stops blinking, clock stops moving. All I can do is hold down the power button on the front of the box to shut it off. Sometimes it happens after several months of continuous uptime; sometimes it happens a few minutes after a reboot, while all I've done is open a terminal to look at log files, or maybe firefox to do a google search. Each time, there is nothing at all in /var/log/messages at the time of the crash. This makes it seem like a hardware problem, and indeed a few months ago I opened the box and wiggled everything and the problem went away for a while. But now it's back. I went in and checked everything, took out each RAM card and reseated. No luck. I ran all the system diagnostics (the long version) and everything passed with flying colors. Something is messed up in this box, but without any useful logs or failed tests, how in the world am I going to find it? And of course, Dell's not gonna help me cause I went and replaced Windows with Ubuntu. What steps would you take next to track down this problem?

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• How to compare two file structures in PHP?

  - by OM The Eternity

  I have a function which gives me the complete file structure upto n-level, function getDirectory($path = '.', $ignore = '') { $dirTree = array (); $dirTreeTemp = array (); $ignore[] = '.'; $ignore[] = '..'; $dh = @opendir($path); while (false !== ($file = readdir($dh))) { if (!in_array($file, $ignore)) { if (!is_dir("$path/$file")) { //display of file and directory name with their modification time $stat = stat("$path/$file"); $statdir = stat("$path"); $dirTree["$path"][] = $file. " === ". date('Y-m-d H:i:s', $stat['mtime']) . " Directory == ".$path."===". date('Y-m-d H:i:s', $statdir['mtime']) ; } else { $dirTreeTemp = getDirectory("$path/$file", $ignore); if (is_array($dirTreeTemp))$dirTree = array_merge($dirTree, $dirTreeTemp); } } } closedir($dh); return $dirTree; } $ignore = array('.htaccess', 'error_log', 'cgi-bin', 'php.ini', '.ftpquota'); //function call $dirTree = getDirectory('.', $ignore); //file structure array print print_r($dirTree); Now here my requirement is , I have two sites The Development/Test Site- where i do testing of all the changes The Production Site- where I finally post all the changes as per test in development site Now, for example, I have tested an image upload in the Development/test site, and i found it appropriate to publish on Production site then i will completely transfer the Development/Test DB detail to Production DB, but now I want to compare the files structure as well to transfer the corresponding image file to Production folder. There could be the situation when I update the image by editing the image and upload it with same name, now in this case the image file would be already present there, which will restrict the use of "file_exist" logic, so for these type of situations....HOW CAN I COMPARE THE TWO FILE STRUCTURE TO GET THE SYNCHRONIZATION DONE AS PER REQUIREMENT??

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• Oracle - UPSERT with update not executed for unmodified values

  - by Buthrakaur

  I'm using following update or insert Oracle statement at the moment: BEGIN UPDATE DSMS SET SURNAME = :SURNAME, FIRSTNAME = :FIRSTNAME, VALID = :VALID WHERE DSM = :DSM; IF (SQL%ROWCOUNT = 0) THEN INSERT INTO DSMS (DSM, SURNAME, FIRSTNAME, VALID) VALUES (:DSM, :SURNAME, :FIRSTNAME, :VALID); END IF; END; This runs fine except that the update statement performs dummy update if the data is same as the parameter values provided. I would not mind the dummy update in normal situation, but there's a replication/synchronization system build over this table using triggers on tables to capture updated records and executing this statement frequently for many records simply means that I'd cause huge traffic in triggers and the sync system. Is there any simple method how to reformulate this code that the update statement wouldn't update record if not necessary without using following IF-EXISTS check code which I find not sleek enough and maybe also not most efficient for this task? DECLARE CNT NUMBER; BEGIN SELECT COUNT(1) INTO CNT FROM DSMS WHERE DSM = :DSM; IF SQL%FOUND THEN UPDATE DSMS SET SURNAME = :SURNAME, FIRSTNAME = :FIRSTNAME, VALID = :VALID WHERE DSM = :DSM AND (SURNAME != :SURNAME OR FIRSTNAME != :FIRSTNAME OR VALID != :VALID); ELSE INSERT INTO DSMS (DSM, SURNAME, FIRSTNAME, VALID) VALUES (:DSM, :SURNAME, :FIRSTNAME, :VALID); END IF; END;

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• Ubuntu xrandr rotate issue

  - by user83544

  I've just bought a second monitor for my PC which happens to be a pivot monitor. I've already read lots of forums related to my problem but haven't come across a solution - I have the same symptoms as dozens of posts but no matter whatever I try it just doesn't work. I've already changed the xorg.conf file and added in the device section just under Driver "nvidia" the following for my second monitor: Option "RandRRotation" "on" When I save and reboot I try to rotate my screen with the nvidia X server settings by choosing the second monitor and clicking either "left" or "right" for the rotation. It immediately exits the nvidia settings window and does nothing. I tried within the terminal by typing: xrandr -o right I get the following error: X Error of failed request: BadMatch (invalid parameter attributes) Major opcode of failed request: 154 (RANDR) Minor opcode of failed request: 2 (RRSetScreenConfig) Serial number of failed request: 14 Current serial number in output stream: 14 I actually manage to rotate it with Option "Rotate" "CCW" instead of "RandRRotation". The problem with this solution is that you get the second monitor in the right position, but any window you open on that screen is practically unchangeable. You can't change the size nor move it, making it useless for reading PDFs, which is the main reason why I bought this second screen to help me write my thesis. Any help is really appreciated. sudo lshw -c video hiram@hiram-linux:~$ sudo lshw -c video *-display description: VGA compatible controller product: nVidia Corporation vendor: nVidia Corporation physical id: 0 bus info: pci@0000:01:00.0 version: a1 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress vga_controller bus_master cap_list rom configuration: driver=nvidia latency=0 resources: irq:16 memory:f8000000-f9ffffff memory:d8000000-dfffffff memory:d4000000-d7ffffff ioport:dc00(size=12 memory:fbd80000-fbdfffff

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• clocksource tsc unstable

  - by amorfis

  Ok, now I have real server fault ;) After some time from booting (about one minute) my server hangs. All I can do is hard reset. Then after restart in /var/log/kern.log I can find: Jul 29 22:38:57 leonidas kernel: [ 90.729598] longhaul: Failed to set requested frequency! Jul 29 22:38:57 leonidas kernel: [ 90.731252] longhaul: Enabling "Ignore Revision ID" option. Jul 29 22:38:57 leonidas kernel: [ 91.201461] longhaul: Failed to set requested frequency! Jul 29 22:38:57 leonidas kernel: [ 91.201482] longhaul: Disabling ACPI C3 support. Jul 29 22:38:57 leonidas kernel: [ 91.204230] longhaul: Disabling "Ignore Revision ID" option. Jul 29 22:38:58 leonidas kernel: [ 91.416133] longhaul: Failed to set requested frequency! Jul 29 22:38:58 leonidas kernel: [ 91.416152] longhaul: Enabling "Ignore Revision ID" option. Jul 29 22:38:58 leonidas kernel: [ 91.960048] Clocksource tsc unstable (delta = -105611479 ns) I found some resources on the net, and it said to change clocksource, or disable ACPI. I tried disabling ACPI but it didn't help (but I noticed there was longer time before hanging). I can't change clock to hpet, because my system doesn't have such one. Output of cat /sys/devices/system/clocksource/clocksource0/available_clocksource: acpi_pm jiffies tsc My system is ubuntu server on VIA Epia hardware.

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