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  • Static method,new thread performance question

    - by ylazez
    Hey guys i just have two questions about two methods used in many controllers/servlets in my app: 1-what is the difference between calling a static method in a util class or a non static method (like methods dealing with dates i.e getting current time,converting between timezones), which is better ? 2-what is the difference between calling a method(contain too many logic like sending emails) in the controller directly or running this method in a different thread ?

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  • C++ thread to seperate process

    - by silverbandit91
    Is there any way i can have a thread branch off into it's own independent process? I know there's the CreateProcess function but as far as I can tell, you can only run external applications with it. Is what I'm asking for at all possible?

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  • C++ Win/Linux thread syncronization Event

    - by JP
    Hello I have some code that is cross-platform by unsing #ifdef OS, I have a Queue protected by a CriticalSection on Windows, and by a pthread_mutex_t on Linux. I would like to implement a Wait(timeout) call that would block a thread until something has been enqueued. I though about using WaitForSingleObject on windows but it don't seem to support CriticalSection. Which Win32 and which Linux functions should I use to Wait and Signal for a condition to happen. Thank

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  • Reuse Hibernate session in thread

    - by Marco
    Hello, I've read somewhere that when a session is flushed or a transaction is committed, the session itself is closed by Hibernate. So, how can i reuse an Hibernate Session, in the same thread, that has been previously closed? Thanks

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  • is this class thread safe?

    - by flash
    consider this class,with no instance variables and only methods which are non-synchronous can we infer from this info that this class in Thread-safe? public class test{ public void test1{ // do something } public void test2{ // do something } public void test3{ // do something } }

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  • IS ResultSet thread safe

    - by javatraniee
    Is ResultSet Thread safe? My question arises because in this i have used a different statement for each query i have delsared a ResultSet as an local variable but it gives me a error of Operation not allowed after ResultSet is closed. But my statements are working as i'm using the statements in insert and delete query.I have commented the ResultSet part and have not got the error !! The source code of my program can be referd to , in my earlier Question .

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  • Best Java thread-safe locking mechanism for collections?

    - by Simon
    What would be the least-slow thread-safe mechanism for controlling multiple accesses to a collection in Java? I am adding objects to the top of a collection and i am very unsure what would be the best performing collection. Would it be a vector or a queue? I originally thought an ArrayList would be fast but i ran some experiments and it was very slow. EDIT: In my insertion testing a Vector delared using volatile seems to be the fastest?

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  • Thread-safe get (accessor method)

    - by sonofdelphi
    I'm currently using the following code for thread-safe access of a variable. int gnVariable; void getVariableValue(int *pnValue) { acquireLock(); //Acquires the protection mechanism *pnValue = gnVariable; releaseLock(); //Releasing the protection mechanism } I would like to change my API signature to a more user-friendly int getVariableValue(void); How should I rewrite the function - such that the users of the API don't have to bother about the locking/unlocking details?

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  • java Thread class run() method

    - by JavaUser
    Hi, Thread class has run method to implement the business logic that could be executed in parallel.But I want implement different business logics in a single run method and to run simultaneously.How to get this feature. thanks

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  • pyqt QObject: Cannot create children for a parent that is in a different thread

    - by memomk
    QObject: Cannot create children for a parent that is in a different thread. (Parent is QTextDocument(0x9919018), parent's thread is QThread(0x97331e0), current thread is flooderthread(0x97b4c10) error means ? am sorry because am new to pyqt here is the code : i know the code is finished yet but it should work i guess the problem is with myfun.log function... #! /usr/bin/python # -*- coding: utf-8 -*- import urllib, urllib2, itertools, threading, cookielib, Cookie, sys, time, hashlib, os from PyQt4 import QtCore, QtGui try: _fromUtf8 = QtCore.QString.fromUtf8 except AttributeError: _fromUtf8 = lambda s: s gui=QtGui.QApplication.processEvents texttoset="" class fun(): global texttoset def checkpassword(self): if ui.passwordcheck.isChecked()==True: return 1 else : return 0 def log(self, text): if text != False: firsttext=str(ui.console.toPlainText()) secondtext=firsttext+text+"\n" ui.console.setText(secondtext) log=open("log.log", "a") log.write(text+"\n") log.close() else : firsttext=str(ui.console.toPlainText()) secondtext=firsttext+texttoset+"\n" ui.console.setText(secondtext) log=open("log.log", "a") log.write(texttoset+"\n") log.close() def disable(self): MainWindow.setEnabled(False) pass def enable(self): MainWindow.setEnabled(True) pass def checkmethod(self): if ui.get.isChecked()==True: return 1 elif ui.post.isChecked()==True: return 2 else : return 0 def main(self): connecter() gui() f1.start() gui() time.sleep(3) gui() f2.start() gui() time.sleep(3) gui() f3.start() gui() time.sleep(3) gui() f4.start() gui() time.sleep(3) gui() f5.start() gui() self.sleep(3) gui() f6.start() gui() def killer(self): f1.terminate() f2.terminate() f3.terminate() f4.terminate() f5.terminate() f6.terminate() def close(self): self.killer() os.abort() sys.exit() myfun=fun() def connecter(): QtCore.QObject.connect(f1, QtCore.SIGNAL("log(bool)"), myfun.log) QtCore.QObject.connect(f1, QtCore.SIGNAL("enable()"), myfun.enable) QtCore.QObject.connect(f1, QtCore.SIGNAL("disable()"), myfun.disable) QtCore.QObject.connect(f2, QtCore.SIGNAL("log(bool)"), myfun.log) QtCore.QObject.connect(f2, QtCore.SIGNAL("enable()"), myfun.enable) QtCore.QObject.connect(f2, QtCore.SIGNAL("disable()"), myfun.disable) QtCore.QObject.connect(f3, QtCore.SIGNAL("log(bool)"), myfun.log) QtCore.QObject.connect(f3, QtCore.SIGNAL("enable()"), myfun.enable) QtCore.QObject.connect(f3, QtCore.SIGNAL("disable()"), myfun.disable) QtCore.QObject.connect(f4, QtCore.SIGNAL("log(bool)"), myfun.log) QtCore.QObject.connect(f4, QtCore.SIGNAL("enable()"), myfun.enable) QtCore.QObject.connect(f4, QtCore.SIGNAL("disable()"), myfun.disable) QtCore.QObject.connect(f5, QtCore.SIGNAL("log(bool)"), myfun.log) QtCore.QObject.connect(f5, QtCore.SIGNAL("enable()"), myfun.enable) QtCore.QObject.connect(f5, QtCore.SIGNAL("disable()"), myfun.disable) QtCore.QObject.connect(f6, QtCore.SIGNAL("log(bool)"), myfun.log) QtCore.QObject.connect(f6, QtCore.SIGNAL("enable()"), myfun.enable) QtCore.QObject.connect(f6, QtCore.SIGNAL("disable()"), myfun.disable) x=0 num=0 class flooderthread(QtCore.QThread): global texttoset def __init__(self, x, num): QtCore.QThread.__init__(self) self.x=x self.num=num def log(self, text): texttolog=str(text) time.sleep(1) self.emit(QtCore.SIGNAL("log(bool)"), False) time.sleep(2) def enable(self): time.sleep(1) self.emit(QtCore.SIGNAL("enable()")) def disable(self): time.sleep(1) self.emit(QtCore.SIGNAL("disable()")) def run(self): connecter() self.log("\n\n--------------------------------------------------new session-------------------------------------\n\n") itered=False gui() self.disable() gui() self.log("setting params...") param={ui.dataname1.text():ui.datavalue1.text(),ui.dataname3.text():ui.datavalue3.text(),ui.dataname3.text():ui.datavalue3.text(), } self.log("checking password...") if myfun.checkpassword()==1: itered=True self.log("password is true") else : self.log("password is null ") self.log("itered operation") self.log("setting url") url=str(ui.url.text()) if url[:4]!="http" and url[:3]!="ftp": self.log("url error exiting the whole function") self.log("please set a valide protocole!!") gui() self.enable() gui() return 1 pass else : self.log("valid url") gui() self.log("url is "+url) self.log("setting proxy") proxy="http://"+ui.proxyuser.text()+":"+ui.proxypass.text()+"@"+ui.proxyhost.text()+":"+ui.proxyport.text() self.log("proxy is "+proxy) gui() self.log("preparing params...") urlparam=urllib.urlencode(param) gui() self.log("params are "+urlparam) self.log("setting up headers...") header={'User-Agent':str(ui.useragent.toPlainText())} self.log("headers are "+ str(header)) self.log("setting up proxy handler..") proxyhandler=urllib2.ProxyHandler({"http":str(proxy)}) self.log("checking method") if myfun.checkmethod()==1: self.log("method is get..") self.log("setting request..") finalurl=url+urlparam gui() self.log("final url is"+finalurl) req=urllib2.Request(finalurl, None, headers) elif myfun.checkmethod()==2: self.log("method is post...") self.log("setting request..") finalurl=url gui() self.log("final url is "+finalurl) req=urllib2.Request(finalurl, urlparam, header) else : self.log("error has been accourded") self.log("please select a method!!") gui() self.log("exiting the whole functions") gui() self.enable() return 1 pass self.log("intilizing cookies..") c1=Cookie.SimpleCookie() c1[str(ui.cookiename1.text())]=str(ui.cookievalue1.text()) c1[str(ui.cookiename1.text())]['path']='/' c1[str(ui.cookiename2.text())]=str(ui.cookievalue2.text()) c1[str(ui.cookiename2.text())]['path']='/' c1[str(ui.cookiename3.text())]=str(ui.cookievalue3.text()) c1[str(ui.cookiename3.text())]['domain']=url c1[str(ui.cookiename3.text())]['path']='/' c1[str(ui.cookiename4.text())]=str(ui.cookievalue4.text()) c1[str(ui.cookiename4.text())]['domain']=url c1[str(ui.cookiename4.text())]['path']='/' self.log("cookies are.. :"+str(c1)) cj=cookielib.CookieJar() cj.set_cookie(c1) opener = urllib2.build_opener(proxyhandler, urllib2.HTTPCookieProcessor(cj)) self.log("insatlling opener") urllib2.install_opener(opener) self.log("setting the two operations....") if itered==Fasle: self.log("starting the flooding loop") gui() while true: try: gui() opener.open(req) except e: self.log("error connecting : "+e.reason) self.log("will continue....") continue gui() elif itered==True: pass f1=flooderthread(1, 1) f2=flooderthread(2, 2) f3=flooderthread(3, 3) f4=flooderthread(4, 4) f5=flooderthread(5, 5) f6=flooderthread(6, 6) class Ui_MainWindow(object): def setupUi(self, MainWindow): MainWindow.setObjectName(_fromUtf8("MainWindow")) MainWindow.setMinimumSize(QtCore.QSize(838, 500)) MainWindow.setMaximumSize(QtCore.QSize(838, 500)) MainWindow.setWindowTitle(QtGui.QApplication.translate("MainWindow", "memo flooder", None, QtGui.QApplication.UnicodeUTF8)) self.centralwidget = QtGui.QWidget(MainWindow) self.centralwidget.setObjectName(_fromUtf8("centralwidget")) self.console=QtGui.QTextEdit(self.centralwidget) self.console.setGeometry(10, 350, 800,130) self.console.setReadOnly(True) self.console.setObjectName("console") self.groupBox = QtGui.QGroupBox(self.centralwidget) self.groupBox.setGeometry(QtCore.QRect(30, 50, 71, 80)) self.groupBox.setTitle(QtGui.QApplication.translate("MainWindow", "method:", None, QtGui.QApplication.UnicodeUTF8)) self.groupBox.setObjectName(_fromUtf8("groupBox")) self.post = QtGui.QRadioButton(self.groupBox) self.post.setGeometry(QtCore.QRect(10, 20, 61, 22)) self.post.setText(QtGui.QApplication.translate("MainWindow", "post", None, QtGui.QApplication.UnicodeUTF8)) self.post.setChecked(True) self.post.setObjectName(_fromUtf8("post")) self.get = QtGui.QRadioButton(self.groupBox) self.get.setGeometry(QtCore.QRect(10, 50, 51, 22)) self.get.setText(QtGui.QApplication.translate("MainWindow", "get", None, QtGui.QApplication.UnicodeUTF8)) self.get.setObjectName(_fromUtf8("get")) self.url = QtGui.QLineEdit(self.centralwidget) self.url.setGeometry(QtCore.QRect(70, 20, 671, 27)) self.url.setInputMethodHints(QtCore.Qt.ImhUrlCharactersOnly) self.url.setObjectName(_fromUtf8("url")) self.groupBox_2 = QtGui.QGroupBox(self.centralwidget) self.groupBox_2.setGeometry(QtCore.QRect(110, 50, 371, 111)) self.groupBox_2.setTitle(QtGui.QApplication.translate("MainWindow", "data:", None, QtGui.QApplication.UnicodeUTF8)) self.groupBox_2.setObjectName(_fromUtf8("groupBox_2")) self.dataname1 = QtGui.QLineEdit(self.groupBox_2) self.dataname1.setGeometry(QtCore.QRect(20, 30, 101, 27)) self.dataname1.setObjectName(_fromUtf8("dataname1")) self.label = QtGui.QLabel(self.groupBox_2) self.label.setGeometry(QtCore.QRect(40, 10, 67, 17)) self.label.setText(QtGui.QApplication.translate("MainWindow", "name:", None, QtGui.QApplication.UnicodeUTF8)) self.label.setObjectName(_fromUtf8("label")) self.dataname2 = QtGui.QLineEdit(self.groupBox_2) self.dataname2.setGeometry(QtCore.QRect(130, 30, 113, 27)) self.dataname2.setObjectName(_fromUtf8("dataname2")) self.dataname3 = QtGui.QLineEdit(self.groupBox_2) self.dataname3.setGeometry(QtCore.QRect(250, 30, 113, 27)) self.dataname3.setObjectName(_fromUtf8("dataname3")) self.label_2 = QtGui.QLabel(self.groupBox_2) self.label_2.setGeometry(QtCore.QRect(40, 60, 67, 17)) self.label_2.setText(QtGui.QApplication.translate("MainWindow", "value:", None, QtGui.QApplication.UnicodeUTF8)) self.label_2.setObjectName(_fromUtf8("label_2")) self.datavalue1 = QtGui.QLineEdit(self.groupBox_2) self.datavalue1.setGeometry(QtCore.QRect(20, 80, 101, 27)) self.datavalue1.setObjectName(_fromUtf8("datavalue1")) self.datavalue2 = QtGui.QLineEdit(self.groupBox_2) self.datavalue2.setGeometry(QtCore.QRect(130, 80, 113, 27)) self.datavalue2.setObjectName(_fromUtf8("datavalue2")) self.datavalue3 = QtGui.QLineEdit(self.groupBox_2) self.datavalue3.setGeometry(QtCore.QRect(250, 80, 113, 27)) self.datavalue3.setObjectName(_fromUtf8("datavalue3")) self.groupBox_4 = QtGui.QGroupBox(self.centralwidget) self.groupBox_4.setGeometry(QtCore.QRect(670, 50, 151, 111)) self.groupBox_4.setTitle(QtGui.QApplication.translate("MainWindow", "password:", None, QtGui.QApplication.UnicodeUTF8)) self.groupBox_4.setObjectName(_fromUtf8("groupBox_4")) self.passname = QtGui.QLineEdit(self.groupBox_4) self.passname.setGeometry(QtCore.QRect(10, 30, 113, 27)) self.passname.setObjectName(_fromUtf8("passname")) self.passvalue = QtGui.QLineEdit(self.groupBox_4) self.passvalue.setGeometry(QtCore.QRect(10, 80, 113, 27)) self.passvalue.setObjectName(_fromUtf8("passvalue")) self.passwordcheck = QtGui.QCheckBox(self.centralwidget) self.passwordcheck.setGeometry(QtCore.QRect(670, 180, 97, 22)) self.passwordcheck.setText(QtGui.QApplication.translate("MainWindow", "password", None, QtGui.QApplication.UnicodeUTF8)) self.passwordcheck.setChecked(True) self.passwordcheck.setObjectName(_fromUtf8("passwordcheck")) self.groupBox_5 = QtGui.QGroupBox(self.centralwidget) self.groupBox_5.setGeometry(QtCore.QRect(29, 169, 441, 81)) self.groupBox_5.setTitle(QtGui.QApplication.translate("MainWindow", "proxy:", None, QtGui.QApplication.UnicodeUTF8)) self.groupBox_5.setObjectName(_fromUtf8("groupBox_5")) self.proxyhost = QtGui.QLineEdit(self.groupBox_5) self.proxyhost.setGeometry(QtCore.QRect(20, 30, 113, 27)) self.proxyhost.setObjectName(_fromUtf8("proxyhost")) self.proxyport = QtGui.QLineEdit(self.groupBox_5) self.proxyport.setGeometry(QtCore.QRect(140, 30, 51, 27)) self.proxyport.setInputMethodHints(QtCore.Qt.ImhDigitsOnly|QtCore.Qt.ImhPreferNumbers) self.proxyport.setObjectName(_fromUtf8("proxyport")) self.proxyuser = QtGui.QLineEdit(self.groupBox_5) self.proxyuser.setGeometry(QtCore.QRect(200, 30, 113, 27)) self.proxyuser.setObjectName(_fromUtf8("proxyuser")) self.proxypass = QtGui.QLineEdit(self.groupBox_5) self.proxypass.setGeometry(QtCore.QRect(320, 30, 113, 27)) self.proxypass.setObjectName(_fromUtf8("proxypass")) self.label_4 = QtGui.QLabel(self.groupBox_5) self.label_4.setGeometry(QtCore.QRect(100, 10, 67, 17)) self.label_4.setText(QtGui.QApplication.translate("MainWindow", "host", None, QtGui.QApplication.UnicodeUTF8)) self.label_4.setObjectName(_fromUtf8("label_4")) self.label_5 = QtGui.QLabel(self.groupBox_5) self.label_5.setGeometry(QtCore.QRect(150, 10, 67, 17)) self.label_5.setText(QtGui.QApplication.translate("MainWindow", "port", None, QtGui.QApplication.UnicodeUTF8)) self.label_5.setObjectName(_fromUtf8("label_5")) self.label_6 = QtGui.QLabel(self.groupBox_5) self.label_6.setGeometry(QtCore.QRect(200, 10, 67, 17)) self.label_6.setText(QtGui.QApplication.translate("MainWindow", "username", None, QtGui.QApplication.UnicodeUTF8)) self.label_6.setObjectName(_fromUtf8("label_6")) self.label_7 = QtGui.QLabel(self.groupBox_5) self.label_7.setGeometry(QtCore.QRect(320, 10, 67, 17)) self.label_7.setText(QtGui.QApplication.translate("MainWindow", "password", None, QtGui.QApplication.UnicodeUTF8)) self.label_7.setObjectName(_fromUtf8("label_7")) self.groupBox_6 = QtGui.QGroupBox(self.centralwidget) self.groupBox_6.setGeometry(QtCore.QRect(30, 260, 531, 91)) self.groupBox_6.setTitle(QtGui.QApplication.translate("MainWindow", "cookies:", None, QtGui.QApplication.UnicodeUTF8)) self.groupBox_6.setObjectName(_fromUtf8("groupBox_6")) self.cookiename1 = QtGui.QLineEdit(self.groupBox_6) self.cookiename1.setGeometry(QtCore.QRect(10, 20, 113, 27)) self.cookiename1.setObjectName(_fromUtf8("cookiename1")) self.cookiename2 = QtGui.QLineEdit(self.groupBox_6) self.cookiename2.setGeometry(QtCore.QRect(140, 20, 113, 27)) self.cookiename2.setObjectName(_fromUtf8("cookename2")) self.cookiename3 = QtGui.QLineEdit(self.groupBox_6) self.cookiename3.setGeometry(QtCore.QRect(270, 20, 113, 27)) self.cookiename3.setObjectName(_fromUtf8("cookiename3")) self.cookiename4 = QtGui.QLineEdit(self.groupBox_6) self.cookiename4.setGeometry(QtCore.QRect(390, 20, 113, 27)) self.cookiename4.setObjectName(_fromUtf8("cookiename4")) self.cookievalue1 = QtGui.QLineEdit(self.groupBox_6) self.cookievalue1.setGeometry(QtCore.QRect(10, 50, 113, 27)) self.cookievalue1.setObjectName(_fromUtf8("cookievalue1")) self.cookievalue2 = QtGui.QLineEdit(self.groupBox_6) self.cookievalue2.setGeometry(QtCore.QRect(140, 50, 113, 27)) self.cookievalue2.setObjectName(_fromUtf8("cookievalue2")) self.cookievalue3 = QtGui.QLineEdit(self.groupBox_6) self.cookievalue3.setGeometry(QtCore.QRect(270, 50, 113, 27)) self.cookievalue3.setObjectName(_fromUtf8("cookievalue3")) self.cookievalue4 = QtGui.QLineEdit(self.groupBox_6) self.cookievalue4.setGeometry(QtCore.QRect(390, 50, 113, 27)) self.cookievalue4.setObjectName(_fromUtf8("cookievalue4")) self.groupBox_7 = QtGui.QGroupBox(self.centralwidget) self.groupBox_7.setGeometry(QtCore.QRect(570, 260, 251, 80)) self.groupBox_7.setTitle(QtGui.QApplication.translate("MainWindow", "useragents:", None, QtGui.QApplication.UnicodeUTF8)) self.groupBox_7.setObjectName(_fromUtf8("groupBox_7")) self.useragent = QtGui.QTextEdit(self.groupBox_7) self.useragent.setGeometry(QtCore.QRect(10, 20, 211, 51)) self.useragent.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOn) self.useragent.setObjectName(_fromUtf8("useragent")) self.start = QtGui.QPushButton(self.centralwidget) self.start.setGeometry(QtCore.QRect(750, 20, 71, 27)) self.start.setText(QtGui.QApplication.translate("MainWindow", "start", None, QtGui.QApplication.UnicodeUTF8)) self.start.setObjectName(_fromUtf8("start")) self.label_3 = QtGui.QLabel(self.centralwidget) self.label_3.setGeometry(QtCore.QRect(30, 20, 67, 17)) self.label_3.setText(QtGui.QApplication.translate("MainWindow", "url :", None, QtGui.QApplication.UnicodeUTF8)) self.label_3.setObjectName(_fromUtf8("label_3")) MainWindow.setCentralWidget(self.centralwidget) QtCore.QObject.connect(self.start, QtCore.SIGNAL(_fromUtf8("clicked(bool)")), myfun.main) QtCore.QObject.connect(self.passwordcheck, QtCore.SIGNAL(_fromUtf8("clicked(bool)")), self.groupBox_4.setEnabled) QtCore.QMetaObject.connectSlotsByName(MainWindow) def __del__(): myfun.killer() os.abort() sys.exit() app = QtGui.QApplication(sys.argv) MainWindow = QtGui.QMainWindow() ui = Ui_MainWindow() ui.setupUi(MainWindow) myfun.log("\n\n--------------------------------------------------new session-------------------------------------\n\n") MainWindow.show() sys.exit(app.exec_())

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  • Thread Synchronisation 101

    - by taspeotis
    Previously I've written some very simple multithreaded code, and I've always been aware that at any time there could be a context switch right in the middle of what I'm doing, so I've always guarded access the shared variables through a CCriticalSection class that enters the critical section on construction and leaves it on destruction. I know this is fairly aggressive and I enter and leave critical sections quite frequently and sometimes egregiously (e.g. at the start of a function when I could put the CCriticalSection inside a tighter code block) but my code doesn't crash and it runs fast enough. At work my multithreaded code needs to be a tighter, only locking/synchronising at the lowest level needed. At work I was trying to debug some multithreaded code, and I came across this: EnterCriticalSection(&m_Crit4); m_bSomeVariable = true; LeaveCriticalSection(&m_Crit4); Now, m_bSomeVariable is a Win32 BOOL (not volatile), which as far as I know is defined to be an int, and on x86 reading and writing these values is a single instruction, and since context switches occur on an instruction boundary then there's no need for synchronising this operation with a critical section. I did some more research online to see whether this operation did not need synchronisation, and I came up with two scenarios it did: The CPU implements out of order execution or the second thread is running on a different core and the updated value is not written into RAM for the other core to see; and The int is not 4-byte aligned. I believe number 1 can be solved using the "volatile" keyword. In VS2005 and later the C++ compiler surrounds access to this variable using memory barriers, ensuring that the variable is always completely written/read to the main system memory before using it. Number 2 I cannot verify, I don't know why the byte alignment would make a difference. I don't know the x86 instruction set, but does mov need to be given a 4-byte aligned address? If not do you need to use a combination of instructions? That would introduce the problem. So... QUESTION 1: Does using the "volatile" keyword (implicity using memory barriers and hinting to the compiler not to optimise this code) absolve a programmer from the need to synchronise a 4-byte/8-byte on x86/x64 variable between read/write operations? QUESTION 2: Is there the explicit requirement that the variable be 4-byte/8-byte aligned? I did some more digging into our code and the variables defined in the class: class CExample { private: CRITICAL_SECTION m_Crit1; // Protects variable a CRITICAL_SECTION m_Crit2; // Protects variable b CRITICAL_SECTION m_Crit3; // Protects variable c CRITICAL_SECTION m_Crit4; // Protects variable d // ... }; Now, to me this seems excessive. I thought critical sections synchronised threads between a process, so if you've got one you can enter it and no other thread in that process can execute. There is no need for a critical section for each variable you want to protect, if you're in a critical section then nothing else can interrupt you. I think the only thing that can change the variables from outside a critical section is if the process shares a memory page with another process (can you do that?) and the other process starts to change the values. Mutexes would also help here, named mutexes are shared across processes, or only processes of the same name? QUESTION 3: Is my analysis of critical sections correct, and should this code be rewritten to use mutexes? I have had a look at other synchronisation objects (semaphores and spinlocks), are they better suited here? QUESTION 4: Where are critical sections/mutexes/semaphores/spinlocks best suited? That is, which synchronisation problem should they be applied to. Is there a vast performance penalty for choosing one over the other? And while we're on it, I read that spinlocks should not be used in a single-core multithreaded environment, only a multi-core multithreaded environment. So, QUESTION 5: Is this wrong, or if not, why is it right? Thanks in advance for any responses :)

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  • Is using a dedicated thread just for sending gpu commands a good idea?

    - by tigrou
    The most basic game loop is like this : while(1) { update(); draw(); swapbuffers(); } This is very simple but have a problem : some drawing commands can be blocking and cpu will wait while he could do other things (like processing next update() call). Another possible solution i have in mind would be to use two threads : one for updating and preparing commands to be sent to gpu, and one for sending these commands to the gpu : //first thread while(1) { update(); render(); // use gamestate to generate all needed triangles and commands for gpu // put them in a buffer, no command is send to gpu // two buffers will be used, see below pulse(); //signal the other thread data is ready } //second thread while(1) { wait(); // wait for second thread for data to come send_data_togpu(); // send prepared commands from buffer to graphic card swapbuffers(); } also : two buffers would be used, so one buffer could be filled with gpu commands while the other would be processed by gpu. Do you thing such a solution would be effective ? What would be advantages and disadvantages of such a solution (especially against a simpler solution (eg : single threaded with triple buffering enabled) ?

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  • Tuning Default WorkManager - Advantages and Disadvantages

    - by Murali Veligeti
    Before discussing on Tuning Default WorkManager, lets have a brief introduction on What is Default WorkManger Before Weblogic Server 9.0 release, we had the concept of Execute Queues. WebLogic Server (before WLS 9.0), processing was performed in multiple execute queues. Different classes of work were executed in different queues, based on priority and ordering requirements, and to avoid deadlocks. In addition to the default execute queue, weblogic.kernel.default, there were pre-configured queues dedicated to internal administrative traffic, such as weblogic.admin.HTTP and weblogic.admin.RMI.Users could control thread usage by altering the number of threads in the default queue, or configure custom execute queues to ensure that particular applications had access to a fixed number of execute threads, regardless of overall system load. From WLS 9.0 release onwards WebLogic Server uses is a single thread pool (single thread pool which is called Default WorkManager), in which all types of work are executed. WebLogic Server prioritizes work based on rules you define, and run-time metrics, including the actual time it takes to execute a request and the rate at which requests are entering and leaving the pool.The common thread pool changes its size automatically to maximize throughput. The queue monitors throughput over time and based on history, determines whether to adjust the thread count. For example, if historical throughput statistics indicate that a higher thread count increased throughput, WebLogic increases the thread count. Similarly, if statistics indicate that fewer threads did not reduce throughput, WebLogic decreases the thread count. This new strategy makes it easier for administrators to allocate processing resources and manage performance, avoiding the effort and complexity involved in configuring, monitoring, and tuning custom executes queues. The Default WorkManager is used to handle thread management and perform self-tuning.This Work Manager is used by an application when no other Work Managers are specified in the application’s deployment descriptors. In many situations, the default Work Manager may be sufficient for most application requirements. WebLogic Server’s thread-handling algorithms assign each application its own fair share by default. Applications are given equal priority for threads and are prevented from monopolizing them. The default work-manager, as its name tells, is the work-manager defined by default.Thus, all applications deployed on WLS will use it. But sometimes, when your application is already in production, it's obvious you can't take your EAR / WAR, update the deployment descriptor(s) and redeploy it.The default work-manager belongs to a thread-pool, as initial thread-pool comes with only five threads, that's not much. If your application has to face a large number of hits, you may want to start with more than that.Well, that's quite easy. You have  two option to do so.1) Modify the config.xmlJust add the following line(s) in your server definition : <server> <name>AdminServer</name> <self-tuning-thread-pool-size-min>100</self-tuning-thread-pool-size-min> <self-tuning-thread-pool-size-max>200</self-tuning-thread-pool-size-max> [...] </server> 2) Adding some JVM parameters Add the following system property in setDomainEnv.sh/setDomainEnv.cmd or startWebLogic.sh/startWebLogic.cmd : -Dweblogic.threadpool.MinPoolSize=100 -Dweblogic.threadpool.MaxPoolSize=100 Reboot WLS and see the option has been taken into account . Disadvantage: So far its fine. But here there is an disadvantage in tuning Default WorkManager. Internally Weblogic Server has many work managers configured for different types of work.  if we run out of threads in the self-tuning pool(because of system property -Dweblogic.threadpool.MaxPoolSize) due to being undersized, then important work that WLS might need to do could be starved.  So, while limiting the self-tuning would limit the default WorkManager and internally it also limits all other internal WorkManagers which WLS uses.So the best alternative is to override the default WorkManager that means creating a WorkManager for the Application and assign the WorkManager for the application instead of tuning the Default WorkManager.

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  • Propel-load-data is causing an error

    - by Jon Winstanley
    I am trying to load fixtures but myproject is erroring at the CLI and starting the indexer process. I have tried: Rebuilding the schema and model Emptying the database and starting again Clearing the cache Validating the YML file and trying much simpler data-dumps My platform is Symfony 1.0 on Windows Some also seems to have had the same issue in the past. C:\web\my_project>symfony propel-load-data backend >> propel load data from "C:\web\my_project\data\fixtures" PHP Warning: session_start(): Cannot send session cookie - headers already sent by (output started at C:\php\PEAR\symfony\vendor\pake\pakeFunction.php:366) in C:\php\PEAR\symfony\storage\sfSessionStorage.class.php on line 77 Warning: session_start(): Cannot send session cookie - headers already sent by (output started at C:\php\PEAR\symfony\vendor\pake\pakeFunction.php:366) in C:\php\PEAR\symfony\storage\sfSessionStorage.class.php on line 77 PHP Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at C:\php\PEAR\symfony\vendor\pake\pakeFunction.php:366) in C:\php\PEAR\symfony\storage\sfSessionStorage.class.php on line 77 Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at C:\php\PEAR\symfony\vendor\pake\pakeFunction.php:366) in C:\php\PEAR\symfony\storage\sfSessionStorage.class.php on line 77

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  • Device Driver IRQL and Thread/Context Switches

    - by Christian Hoglund
    Hi, I'm new to Windows device driver programming. I know that certain operations can only be performed at IRQL PASSIVE_LEVEL. For example, Microsoft have this sample code of how to write to a file from a kernel driver: if (KeGetCurrentIrql() != PASSIVE_LEVEL) return STATUS_INVALID_DEVICE_STATE; Status = ZwCreateFile(...); My question is this: What is preventing the IRQL from being raised after the KeGetCurrentIrql() check above? Say a context or thread swithch occurs, couldn't the IRQL suddenly be DISPATCH_LEVEL when it gets back to my driver which would then result in a system crash? If this is NOT possible then why not just check the IRQL in the DriverEntry function and be done with it once for all?

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  • Is Interop.Domino dll thread safe ?

    - by anup-24
    Hi , I am using Interop.Domino dll version 1.2 in c# application, and using multithreading to access multiple NSF file at same time by creating new session for each thread created (Max 5 threads at a time). For the large NSF files, I was getting the Notes error like memory segment overflow. To overcome this problem, i used Marshal.ReleaseComObject(object) to release the necessary Notesdocument, and NotesView object where ever possible. Now, the issues is like, i am able to access 2 NSF files but the rest threads are going in dll exceptions as few Notes object are getting null. Kindly provide me some help.... Thanks for help.

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  • Threading Issue with WCF Service

    - by helixed
    I'm new to both WCF and threading, so please bear with me. I have a WCF service set up. The service has multiple threads, all of which act upon a single array. This works without a problem so far. However, this service has a method, which, when called, will return the array. My questions: The array is serialized when it is transferred to the client by WCF. Is this a thread safe operation? In other words, can I count on WCF to block all threads from accessing this array while it's being serialized? If I can't count on WCF to do this, then how can I implement it manually? I don't really understand how WCF would facilitate this since the serialization happens after I return from my method call. How can I guarantee a thread will not modify the array after it's been returned by my method but before WCF serializes it?

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  • WPF -- Event Threading, GUI updating question

    - by LSTayon
    I'm trying to send two events to the main window so that I can show some kind of animation that will let the user know that I'm updating the data. This is an ObservableCollection object so the OnPropertyChanged is immediately picked up by the bindings on the main window. The sleep is only in there so that the user can see the animation. However, the first OnPropetyChanged is never seen. I'm assuming this is because we're in a single thread here and the timer_Tick has to finish before the GUI updates. Any suggetions? In VB6 land we would use a DoEvents or a Form.Refresh. Thanks! private void timer_Tick(object sender, EventArgs e) { Loading = "Before: " + DateTime.Now.ToString(); OnPropertyChanged("Loading"); LoadData(); Thread.Sleep(1000); //Loading = Visibility.Hidden; Loading = "After: " + DateTime.Now.ToString(); OnPropertyChanged("Loading"); }

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  • Timer or Thread?

    - by Pradeep Singh
    I have a method(say method1) that writes to database(sqlserver)and another method(say method2) that tries to access the same database after some time and updates the data row that was created by method1. The problem arises when method1 fails to access db due to the LAN being disconnected (this is not an exception this is a scenario that will definitely arise in my software, getting into details will make the question too complex) if method1 fails to access db method2 cannot work. What I want to do is to make method1 store values to local db instead of server if the LAN is disconnected and as soon as it enters value in local db the application should start trying to access the server after ever 10-15 seconds. What should I use timer or create a new thread?

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  • Thread and two dimensional array in objective C?

    - by mactonny
    Hey, guys, I am just starting to wrap my head around objective C and I am doing a little project on Iphone. And I just encountered a weird problem. I had to deal with images in my program so I have a lot local variables declared like temp[width][height]. If I am not using NSThread to perform image processing, it works all fine. However, if I use NSThread, it'll keep giving me EXC_BAD_ACCESS on whenever I try to access a 2-D array declared like temp[widht][height]. So I have to allocate memory from heap in order to have a 2-D array. That'll solve the problem but I still don't get it. My first thought would be stack over flow, but it worked all fine with one thread. I just don't get it.

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  • How do I let main thread wait for the Timer.timer

    - by Kelvin
    Hi I am using System.Timer.Timer I always get NULL after running my programme and it only works if I add this.sleep(6000). Suppose the reason is the main thread ends but the timer hasn't finished ... Here is the class and I call the class from my main form. Class class1 { string finalResult = ""; public string getNumber() { RunTimer(); return finalResult; } pubic void RunTimer () { timer = new System.Timers.Timer(6000); timer.Interval = 1000; timer.Elapsed += new System.Timers.ElapsedEventHandler(cal); timer.Start(); } private void cal(object sender,System.Timers.ElapsedEventArgs e) { finalResult = READFROMCOMPORT; } }

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  • process thread scheduling

    - by arvind
    I have the following query regarding the scheduling of process threads. a) If my process A has 3 threads then can these threads be scheduled concurrently on the different CPUs in SMP m/c or they will be given time slice on the same cpu. b) Suppose I have two processes A with 3 threads and Process B with 2 threads (all threads are of same priority) then cpu time allocated to each thread (time slice) is dependent on the number of threads in the process or not? Correct me if I am wrong is it so that cpu time is allocated to process which is then shared among its threads i.e. time slice given to process A threads is less than that of Process B threads.

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  • How do I run different threads in Java?

    - by Cris Carter
    Hey. I'm having some problems with threads. I understand how they work, but since they all use the same method, how do I run different threads that do completely different things, but at the same time? To me, it seems that they always use the same standard method which makes them do the same thing. So, let's say I have a big .txt file where I want to go through each line and do something to the line. In this case, I would like to have each thread do 1/10th of the .txt file, but I don't understand how the threads can communicate with each other, and how they could organize so each thread does the right part? Could anyone explain or help me with this? Would be very much appreciated!

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