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  • Function Composition in C++

    - by Channel72
    There are a lot of impressive Boost libraries such as Boost.Lambda or Boost.Phoenix which go a long way towards making C++ into a truly functional language. But is there a straightforward way to create a composite function from any 2 or more arbitrary functions or functors? If I have: int f(int x) and int g(int x), I want to do something like f . g which would statically generate a new function object equivalent to f(g(x)). This seems to be possible through various techniques, such as those discussed here. Certainly, you can chain calls to boost::lambda::bind to create a composite functor. But is there anything in Boost which easily allows you to take any 2 or more functions or function objects and combine them to create a single composite functor, similar to how you would do it in a language like Haskell?

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  • typedef declaration syntax

    - by mt_serg
    Some days ago I looked at boost sources and found interesting typedef. There is a code from "boost\detail\none_t.hpp": namespace boost { namespace detail { struct none_helper{}; typedef int none_helper::*none_t ; } // namespace detail } // namespace boost I didn't see syntax like that earlier and can't explain the sense of that. This typedef introduces name "none_t" as pointer to int in boost::detail namespace. What the syntax is? And what difference between "typedef int none_helper::*none_t" and for example "typedef int *none_t" ?

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  • Why the performance of following code is degrading when I use threads ?

    - by DotNetBeginner
    Why the performance of following code is degrading when I use threads ? **1.Without threads int[] arr = new int[100000000]; //Array elements - [0][1][2][3]---[100000000-1] addWithOutThreading(arr); // Time required for this operation - 1.16 sec Definition for addWithOutThreading public void addWithOutThreading(int[] arr) { UInt64 result = 0; for (int i = 0; i < 100000000; i++) { result = result + Convert.ToUInt64(arr[i]); } Console.WriteLine("Addition = " + result.ToString()); } **2.With threads int[] arr = new int[100000000]; int part = (100000000 / 4); UInt64 res1 = 0, res2 = 0, res3 = 0, res4 = 0; ThreadStart starter1 = delegate { addWithThreading(arr, 0, part, ref res1); }; ThreadStart starter2 = delegate { addWithThreading(arr, part, part * 2, ref res2); }; ThreadStart starter3 = delegate { addWithThreading(arr, part * 2, part * 3, ref res3); }; ThreadStart starter4 = delegate { addWithThreading(arr, part * 3, part * 4, ref res4); }; Thread t1 = new Thread(starter1); Thread t2 = new Thread(starter2); Thread t3 = new Thread(starter3); Thread t4 = new Thread(starter4); t1.Start(); t2.Start(); t3.Start(); t4.Start(); t1.Join(); t2.Join(); t3.Join(); t4.Join(); Console.WriteLine("Addition = "+(res1+res2+res3+res4).ToString()); // Time required for this operation - 1.30 sec Definition for addWithThreading public void addWithThreading(int[] arr,int startIndex, int endIndex,ref UInt64 result) { for (int i = startIndex; i < endIndex; i++) { result = result + Convert.ToUInt64(arr[i]); } }

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  • Cross-thread Winforms control editing

    - by Motig
    Hey, how can I edit the text in a windows form element if the code that is editing the text 'belongs' to a seperate thread from the one that contains the windows form? I get the exception: Cross-thread operation not valid: Control 'textBox1' accessed from a thread other than the thread it was created on. Thank you.

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  • SOLR - Boost function (bf) to increase score of documents whose date is closest to NOW

    - by Mechanic
    Hi all, I have a solr instance containing documents which have a 'startTime' field ranging from last month to a year from now. I'd like to add a boost query/function to boost the scores of documents whose startTime field is close to the current time. So far I have seen a lot of examples which use rord to add boosts to documents whom are newer but I have never seen an example of something like this. Can anyone tell me how to do it please? Thanks

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  • Why Rails.cache is not thread safe?

    - by Freewind
    I know Rails.cache is ActiveSupport::Cache::MemoryStore, and it is not thread safe. I don't understand, why rails use a thread-unsafe cache as its default? Why not use ActiveSupport::Cache::SynchronizedMemoryStore? In my opinion, in a web site, if a cache is not thread-safe, it almost useless, because the requests are not handled in ONE thread. Do you use Rails.cache in you webapp? And how do you use it?

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  • Trace/BPT trap when running feedparser inside a Thread object

    - by simao
    Hello, I am trying to run a Thread to parse a list of links using the universal feed parser, but when I start the thread I get a Trace/BPT trap. Here's the code I am using: class parseRssFiles(Thread): def __init__ (self,rssLinks): Thread.__init__(self) self.rssLinks = rssLinks def run(self): self.rssContents = [ feedparser.parse(link) for link in rssLinks] Is there any other way to do this? Link to the report generated by Mac OS X 10.6.2: http://simaom.com/trace.txt Thanks

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  • java.lang.OutOfMemoryError: unable to create new native thread

    - by Brad
    I consistently get this exception when trying to run my Junit tests on my mac: java.lang.OutOfMemoryError: unable to create new native thread at java.lang.Thread.start0(Native Method) at java.lang.Thread.start(Thread.java:658) at java.util.concurrent.ThreadPoolExecutor.addIfUnderMaximumPoolSize(ThreadPoolExecutor.java:727) at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:657) at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:92) at com.google.appengine.tools.development.ApiProxyLocalImpl$PrivilegedApiAction.run(ApiProxyLocalImpl.java:197) at com.google.appengine.tools.development.ApiProxyLocalImpl$PrivilegedApiAction.run(ApiProxyLocalImpl.java:184) at java.security.AccessController.doPrivileged(Native Method) at com.google.appengine.tools.development.ApiProxyLocalImpl.doAsyncCall(ApiProxyLocalImpl.java:172) at com.google.appengine.tools.development.ApiProxyLocalImpl.makeAsyncCall(ApiProxyLocalImpl.java:138) The same set of unit tests pass perfectly fine on ubuntu and windows. Some information about my system resources on the mac: $ ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited file size (blocks, -f) unlimited max locked memory (kbytes, -l) unlimited max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 1 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) 266 virtual memory (kbytes, -v) unlimited $ java -version java version "1.6.0_24" Java(TM) SE Runtime Environment (build 1.6.0_24-b07-334-10M3326) Java HotSpot(TM) 64-Bit Server VM (build 19.1-b02-334, mixed mode) The reason I dont think this is an application issue is because the same tests pass in different environments. I have tried setting heap to 1024m, 512m and setting the stack to 64k and 128k (and each of these combinations) with no luck. My open files was originally 256 and I have bumped this to 1024. I have been googling around for a bit and all posts say to decrease heap size and increase stack size but that doesnt seem to help. Anyone have anymore ideas? EDIT: Here are is some environment information on my ubuntu box: $ ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 20 file size (blocks, -f) unlimited pending signals (-i) 16382 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) unlimited virtual memory (kbytes, -v) unlimited file locks (-x) unlimited $ java -version java version "1.6.0_24" Java(TM) SE Runtime Environment (build 1.6.0_24-b07) Java HotSpot(TM) 64-Bit Server VM (build 19.1-b02, mixed mode)

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  • Why is the setContextClassLoader() method placed on Thread ?

    - by Roman
    Why is the setContextClassLoader() method placed on thread ? What different thread have different classloaders? The question is what if i extended a classloader , loaded there some new classes. to the my custom classloader. Now , I want it to be the context classloader , so I call the method (Thread.currentThread().setContextClassLoader(loader)). Are these new classes awailable only in the context of the current Thread ? ( or how does it work ?) Thanks

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  • open source thread script to use?

    - by noname
    im building a forum and now im gonna code the thread page. is there any open source thread script to use that resembles stackoverflow:s thread page with the actual thread, the replies and the comments? one which you could customize? i bet a lot of users have created such scripts, would be great to not having to reinvent the wheel. or is it a lot easier to code it yourself?

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  • TextBox and Thread

    - by gloris
    Why doesn't this work? The program stops on: this.textBox1.Text = "(New text)"; Thread demoThread; private void Form1_Load(object sender, EventArgs e) { this.demoThread = new Thread(new ThreadStart(this.ThreadProcUnsafe)); this.demoThread.Start(); textBox1.Text = "Written by the main thread."; } private void ThreadProcUnsafe() { while (true) { Thread.Sleep(2000); this.textBox1.Text = "(New text)"; } }

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  • how to put a thread in Wait in Android

    - by Brijesh Masrani
    I have a thread running in my program When Mouse-down Event generates I want to put that thread in wait() and in Mouse-up I want to Notify that thread But when I tried to do this It is giving me error like "Object not locked by Thread" so can anyone help me how to solve this..

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  • Fixed strptime exception with thread lock, but slows down the program

    - by eWizardII
    I have the following code, which when is running inside of a thread (the full code is here - https://github.com/eWizardII/homobabel/blob/master/lovebird.py) for null in range(0,1): while True: try: with open('C:/Twitter/tweets/user_0_' + str(self.id) + '.json', mode='w') as f: f.write('[') threadLock.acquire() for i, seed in enumerate(Cursor(api.user_timeline,screen_name=self.ip).items(200)): if i>0: f.write(", ") f.write("%s" % (json.dumps(dict(sc=seed.author.statuses_count)))) j = j + 1 threadLock.release() f.write("]") except tweepy.TweepError, e: with open('C:/Twitter/tweets/user_0_' + str(self.id) + '.json', mode='a') as f: f.write("]") print "ERROR on " + str(self.ip) + " Reason: ", e with open('C:/Twitter/errors_0.txt', mode='a') as a_file: new_ii = "ERROR on " + str(self.ip) + " Reason: " + str(e) + "\n" a_file.write(new_ii) break Now without the thread lock I generate the following error: Exception in thread Thread-117: Traceback (most recent call last): File "C:\Python27\lib\threading.py", line 530, in __bootstrap_inner self.run() File "C:/Twitter/homobabel/lovebird.py", line 62, in run for i, seed in enumerate(Cursor(api.user_timeline,screen_name=self.ip).items(200)): File "build\bdist.win-amd64\egg\tweepy\cursor.py", line 110, in next self.current_page = self.page_iterator.next() File "build\bdist.win-amd64\egg\tweepy\cursor.py", line 85, in next items = self.method(page=self.current_page, *self.args, **self.kargs) File "build\bdist.win-amd64\egg\tweepy\binder.py", line 196, in _call return method.execute() File "build\bdist.win-amd64\egg\tweepy\binder.py", line 182, in execute result = self.api.parser.parse(self, resp.read()) File "build\bdist.win-amd64\egg\tweepy\parsers.py", line 75, in parse result = model.parse_list(method.api, json) File "build\bdist.win-amd64\egg\tweepy\models.py", line 38, in parse_list results.append(cls.parse(api, obj)) File "build\bdist.win-amd64\egg\tweepy\models.py", line 49, in parse user = User.parse(api, v) File "build\bdist.win-amd64\egg\tweepy\models.py", line 86, in parse setattr(user, k, parse_datetime(v)) File "build\bdist.win-amd64\egg\tweepy\utils.py", line 17, in parse_datetime date = datetime(*(time.strptime(string, '%a %b %d %H:%M:%S +0000 %Y')[0:6])) File "C:\Python27\lib\_strptime.py", line 454, in _strptime_time return _strptime(data_string, format)[0] File "C:\Python27\lib\_strptime.py", line 300, in _strptime _TimeRE_cache = TimeRE() File "C:\Python27\lib\_strptime.py", line 188, in __init__ self.locale_time = LocaleTime() File "C:\Python27\lib\_strptime.py", line 77, in __init__ raise ValueError("locale changed during initialization") ValueError: locale changed during initialization The problem is with thread lock on, each thread runs itself serially basically, and it takes way to long for each loop to run for there to be any advantage to having a thread anymore. So if there isn't a way to get rid of the thread lock, is there a way to have it run the for loop inside of the try statement faster?

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  • High data on recv-q buffer and thread lock on java.io.BufferedInputStream in linux

    - by Sagar Patel
    We have a java application running on linux (ubuntu server). We have been facing high recv-q problem since quite some time. Application gets hang and does not read data from socket every few hours. In thread dump, we have found below stack trace. "Receiver-146" daemon prio=10 tid=0x00007fb3fc010000 nid=0x7642 runnable [0x00007fb5906c5000] java.lang.Thread.State: RUNNABLE at java.net.SocketInputStream. socketRead0(Native Method) at java.net.SocketInputStream.read(SocketInputStream.java:150) at java.net.SocketInputStream.read(SocketInputStream.java:121) at java.io.BufferedInputStream.fill(BufferedInputStream.java:235) at java.io.BufferedInputStream.read1(BufferedInputStream.java:275) at java.io.BufferedInputStream.read(BufferedInputStream.java:334) - locked <0x00000007688f1ff0> (a java.io.BufferedInputStream) at org.smpp.TCPIPConnection.receive(TCPIPConnection.java:413) at org.smpp.ReceiverBase.receivePDUFromConnection(ReceiverBase.java:197) at org.smpp.Receiver.receiveAsync(Receiver.java:351) at org.smpp.ReceiverBase.process(ReceiverBase.java:96) at org.smpp.util.ProcessingThread.run(ProcessingThread.java:199) at java.lang.Thread.run(Thread.java:722) We are not able to trace the exact reason behind this? Kindly help. We are using 16 core machine and load on the system is around 30-40 at the time of issue. We use command ss dst <ip> to find out recv-q. Recently we have been facing issues with recv-q size getting hung, were in receive buffer gets stuck at some point of time. But recvQ size is not decreasing and as a result we are losing a lot of hits from the other side, our application is not accepting any data.

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  • Automatically running thread stopped after the application idling for more than 1 hour

    - by U Liyanage
    I have a web application which runs on IIS 6.0 and it has a thread that runs on the applicaion startup. That thread will run continously after the application startup with a sleep time of 10 seconds (This will update the application cache from getting the data from DB). But once the application is idle for more than 1 hour this thread is no longer running. Please give me a solution for continously run this thread.

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  • logging one thread in Java using log4j

    - by Javier
    I have an web application written in Java, and I have a thread-pool. The application is huge, and I cannot make major changes, for example, I cannot change log4j. I am executing a batch process in the thread pool, and I want to log everything that goes is executed to execute that process. There will always be just one thread active in the thread pool. Any ideas of how can I do that?

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  • What happens to thread as onDestroy is called when device is rotated

    - by Lakshmie
    I would like to know as to what will happen to the thread which has been created by an activity and the device is rotated. I have observed that the onDestroy method is called when this happens. Will the thread be killed too? If the thread is not killed, how can I reassociate the thread with the activity as a new instance of the activity is created on rotation. Thanks, Lakshmie

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  • To find a determinate of Matrix using Boost library in c++

    - by user314097
    Hi, I' am required to convert a MATLAB function into C++, and this requires me to find determinate of a matrix. I was told that use of BOOST library would make my job easier. I went through the documentation of BOOST Library, but couldn't find much info about the same. If anyone could give a template for the above operation, It would be of lot of help and would be greatly appreciated. Thanks Regards

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  • C# start a static thread

    - by user595605
    I have a Queue of items I want to process in a thread, and any instance of a class can add items to the Queue to be processed. My idea for doing this is to have a static Thread in the class that processes the items, the only problem is that I don't know where to start this thread, since I can't start it in its initialization. Is there a way I can start a static thread? Or should I be changing the architecture completely?

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  • How to detect GUI thread on Android?

    - by ParDroid
    Is there a robust way to detect if Thread.currentThread() is the Android system GUI-thread in an application? I would like to put some asserts in my model code that asserts that only one thread (eg the gui-thread) accesses my state, to assure that no kind of synchronization is neccesary.

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  • Controlling form elements from a different thread in Windows Mobile

    - by d1k_is
    Trying to get a thread to change form controls in Windows Mobile. Throws an unsupported exception. Does this mean it cant be done at all? If not, how do I go about this? Forms are created in the Parent/Main thread then a thread is created to do some work in the background but I want to make it so the Background thread can update the form to show its completed...

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  • C++ Multithreading on Unix

    - by Roger
    I have two related questions: 1) Are there any good books for multithreading in C++, especially now that C++11 contains multithreading in the standard library? 2) I have the Wrox Programming on Unix book (1000 pages fat red one) and within it, it uses the Unix Thread class. How does this code relate to boost and the C++11 multithreading libraries? Is it better/worse/just specific to Unix etc? Is the performance the same?

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  • w WARN: Thread pool pressure. Using current thread for a work item.

    - by GrumpyOldDBA
    The skill set needed by a DBA can be quite diverse at times and a run in with SSRS 2005 probably illustrates the point quite well. I don't have skills in IIS although I was responsible for the design and deployment of an online mortage application site some years ago.I had to get hands on with IIS5, firewalls, intrusion systems, ISA Server, dmzs, NAT, IP and lots of other acronyms so I have an understanding of these things but never had to do anything other than set up and configure IIS - no...(read more)

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