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  • What's the best way to get a stored POP3 password out of Outlook 2007?

    - by Tom Morris
    If you have a password for a POP3 account in Outlook 2007 (Windows 7 Home Premium) and you then forget the password, how do you retrieve it? I tried copy-and-paste. No go. I downloaded Mail PassView, but upon installing it, AVG said it was malware, so I removed it. I eventually found the account details by opening up RegEdit, and found it in HKCU\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\Outlook\ (...) but it was encoded in REG_BINARY. I Googled around and found various Visual Basic routines for decoding it but being a Unix dork I had absolutely no idea what to do with said scripts. By this point, I gave up and managed to get hold of the password by another means (it was written down on a piece of paper in the briefcase of the owner of the account - I know, it makes the inner sysadmin rage). I also attempted to write a simple POP3 server in Python and then get Outlook to log on to it, but that didn't really work out (it was about 4am at that point). For future reference, is there an easy and sensible way of doing this? Is Mail PassView actually evil spyware or was AVG just giving me a false positive? (Any chance of Windows 8 having something like OS X's Keychain?)

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  • Can't install mplayer or vlc on ubuntu

    - by mirko4
    I am trying to install Mplayer or VLC player on ubuntu feisty but i can't do it. I try with apt-get: Reading package lists... Done Building dependency tree Reading state information... Done You might want to run `apt-get -f install' to correct these: The following packages have unmet dependencies: mplayer: Depends: libasound2 (> 1.0.16) but 1.0.13-1ubuntu5 is to be installed Depends: libavcodec51 (>= 0.svn20080206-8) but it is not going to be installed or libavcodec-unstripped-51 (>= 0.svn20080206-8) but it is not installable Depends: libavformat52 (>= 0.svn20080206-8) but it is not going to be installed or libavformat-unstripped-52 (>= 0.svn20080206-8) but it is not installable Depends: libavutil49 (>= 0.svn20080206-8) but it is not going to be installed or libavutil-unstripped-49 (>= 0.svn20080206-8) but it is not installable Depends: libcaca0 (>= 0.99.beta14-1) but 0.99.beta11.debian-2build1 is to be installed Depends: libcdparanoia0 (>= 3.10.2+debian) but 3.10+debian~pre0-4build1 is to be installed Depends: libcucul0 (>= 0.99.beta14-1) but 0.99.beta11.debian-2build1 is to be installed Depends: libfaad0 (>= 2.6.1) but it is not going to be installed Depends: libfribidi0 (>= 0.10.9) but 0.10.7-4build1 is to be installed Depends: libgif4 (>= 4.1.6) but it is not going to be installed Depends: libjack0 (>= 0.109.2) but it is not going to be installed Depends: liblzo2-2 but it is not going to be installed Depends: libopenal1 but it is not going to be installed Depends: libpostproc51 (>= 0.svn20080206-8) but it is not going to be installed or libpostproc-unstripped-51 (>= 0.svn20080206-8) but it is not installable Depends: libspeex1 (>= 1.2~beta3-1) but 1.1.12-3 is to be installed Depends: libsvga1 Depends: libswscale0 (>= 0.svn20080206-8) but it is not going to be installed or libswscale-unstripped-0 (>= 0.svn20080206-8) but it is not installable Depends: mplayer-skin python-apt: Depends: libapt-inst-libc6.7-6-1.1 Depends: libapt-pkg-libc6.7-6-4.6 scim-gtk2-immodule: Depends: libscim8c2a (>= 1.4.6) but 1.4.4-7ubuntu1 is to be installed scim-modules-socket: Depends: libscim8c2a (>= 1.4.6) but 1.4.4-7ubuntu1 is to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution). I try apt-get -f install but it doesn't work neither. What to do please help me ?!

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  • Setting umask for all users

    - by Yarin
    I'm trying to set the default umask to 002 for all users including root on my CentOS box. According to this and other answers, this can be achieved by editing /etc/profile. However the comments at the top of that file say: It's NOT a good idea to change this file unless you know what you are doing. It's much better to create a custom.sh shell script in /etc/profile.d/ to make custom changes to your environment, as this will prevent the need for merging in future updates. So I went ahead and created the following file: /etc/profile.d/myapp.sh with the single line: umask 002 Now, when I create a file logged in as root, the file is born with 664 permissions, the way I had hoped. But files created by my Apache wsgi application, or files created with sudo, still default to 644 permissions... $ touch newfile (as root): Result = 664 (Works) $ sudo touch newfile: Result = 644 (Doesn't work) Files created by Apache wsgi app: Result = 644 (Doesn't work) Files created by Python's RotatingFileHandler: Result = 644 (Doesn't work) Why is this happening, and how can I ensure 664 file permissions system wide, no matter what creates the file? UPDATE: I ended up finding a cleaner solution to this on a per-directory basis using ACLs, which I describe here.

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  • Measuring performance indicators on a cluster

    - by Aditya Singh
    My architecture is based on Amazon. A ELB load balancer balances POST requests among m1.large instances. Every instance has a nginx server on port 80 which distributes the requests to 4 python-tornado servers on backend which handle the request. These tornado servers are taking about 5 - 10ms to respond to one request but this is the internal compute time of every request. I want to put this thing on test and i want to measure the response time from ELB to upstream and back and how does it vary when the QPS throughput is increased and plot a graph of Time vs. QPS vs. Latency and other factors like CPU and Memory. Is there a software to do that or should i log everything somewhere with latency checks and then analyze the whole log to get the stuff out. I would also need to write a self-monitor which keeps checking the whole response time. Is it possible to do it with a script from within the server. If so, will it be accurate ?

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  • More advanced 'Apple Automator' like software?

    - by OrangeBox
    What I'm looking for is a program similar to Automator or A Better Finder Rename but more extensive / advanced. In my situation we have two files with the same name, one is a MOV the other an XML. We want to use some of the metadata within the XML to rename both files. Then we want to re-arrange the contents of the XML file so that it is compatible with another piece of software we use (I think this process is called mapping?) Essentially some software that takes a bunch of variable from existing file and performs file actions to them. I imagine this would be an easy task using apple-script, but I'm wondering if there is a OSX application similar to Automator that can do the above? Questions are: Is there software that can do the above? Could Automator achieve this? What is the technical name of this kind of process? If no such software exists, what would be the best kind of script to use? eg. Make an Apple Script, python script etc.

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  • How to speed up request/response to django using apache or another solution?

    - by jbcurtin
    Hey all, I'm mainly a developer, but every now and again I jump into the sys-admin position. For the most part I've gotten away with deploying php and python apps using apache. I write today because I'm starting to research faster alternatives to apache, yet still have some of the core features I require like put and delete methods and the ability to connect to a socket via apache. ( This I have not tried, but might be a nice whistle if I ever employ comet on my apps. ) As you've probably guessed, I use javascript exclusively for all my websites utilizing deep linking for SEO support. The main areas that I'm looking to increase performance is the connection between the django apps and the web server to the client response. Every day I work my best to keep the smallest memory foot print as possible, however I am getting to the end of my rope when it comes to working with apache. In general, keep in mind that I'm just starting this research so I'm looking more for material to read then solutions at this moment. My main questions: Am I missing something about apache that makes it faster then everything else? What would be a good server environment to deploy just static files one? What are some of the leading open-source and paid alternatives?

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  • How do I encapsulate the application server from the web and database servers?

    - by SNyamathi
    So I've been doing some reading and it seems like the best practice would be to have separate database, application, and web servers. There are a few things that I've failed to understand - please feel free to recommend any reading materials that would address these topics. Database (assume MySQL) Application server communication: Does the database server do any sort of checks on the SQL commands sent / returned, or is it just a "dumb pipe" that responds to SQL commands by spitting back data? Application server (assume Tomcat) Web Server Almost the reverse here, is it the web server that is more of a pipe to the internet that forwards requests to the application server and spits back responses? I'm not wording this well, but I'm trying to ask - is it the application server that is responsible for validating data received by from requests? ex: Parsing POSTs Validating user logins Encrypting decrypting data Furthermore, how do these two servers communicate? I'm trying to keep things as flexible as possible here, so while I could write a web server in Java and use Java to communicate between the web and app server, that doesn't sound very modular. What if I want to use Python or some other language to replace the web server later on? What if I want to make a non-web facing application used in house written in C++ or something.

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  • Postgresql Data Aggregation over WAN Securely

    - by Zach
    Hey guys, Need some advice on how to proceed with this situation: My current scenario is that I have several postgresql (50+) boxes deployed throughout various locations and data centers and a beefy postgresql box setup at a homebase location. All of the deployed boxes have identical database layouts. I'm looking for a solution that would allow for a few things. I realize some of these options overlap and some might only contain mutually exclusive solutions. However, I'm interested to hear your thoughts :) Remotely query the deployed boxes and pull the results back to the homebase box for processing. Nightly (remote) "sync" or dump the deployed boxes' databases to a master database on the homebase box. Remotely push a table entry to all of the deployed boxes from the homebase box. Ensure security of data in transit, and remotely deployed boxes. Up to this point I've been floating on a homebrew multithreaded python/perl system that SSH's into these boxes remotely, which are ACL'ed off to the homebase server and pulls (or pushes) the raw query results over the ssh connection. I have even touched #2 (remote syncing) as I know that would get nasty really quick. I'm interested in any ideas for a more elegant solution that can scale up and stick to my FreeBSD/Linux environment.

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  • Linux Distro - GUI similar to Windows

    - by DeaconDesperado
    I am in the process of refurbing several older laptop machines for use by a couple college guys we have in training to learn basic web development in python. These are students who intern at my company and are hoping to do some work when the summer comes building simple client-oriented webapps (learning the basics of OOP, MVC webapp design in flask, etc.). We're trying to function as the "practical" side of their education. I would like to get them set up on these machines we have sitting about, but I'd like to use a linux distro that would have a gui that closely approximates what they are being compelled to use at school (windows.) I don't really have much of a preference as far as GUI goes since much of what we'll be learning together is accomplished on the command line. I just see this as an easier adjustment for them while they are still reliant on a graphical environment. In the past I'd go straight for Ubuntu, but since they started using the Unity GUI the responsiveness overall can be pretty clunky on older machines, especially since these machines (there are four of them) run the gambit on specs (though all are at least 1.0Ghz and none have anything better than basic integrated video.) Has anyone had to setup a similar working environment in Mint, bare Debian or Zorin? Thanks.

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  • PassEnv does not find ENV variables

    - by quodlibetor
    I've got this /etc/profile.d/myfile.sh: export MYVAR=myval I also have a PassEnv MYVAR line in a <virtualhost> section of an apache conf dir. That lets me do things like: $ echo $MYVAR myval $ python >>> import os; os.getenv('MYVAR') 'myval' $ sudo echo $MYVAR myval $ sudo -i root# echo $MYVAR myval But then, despite that being the case I get: root# /sbin/service httpd restart /sbin/service httpd restart Stopping httpd: [ OK ] Starting httpd: [Mon Oct 22 14:44:02 2012] [warn] PassEnv variable MYVAR was undefined [ OK ] And all of my attempts to access MYVAR from within my wsgi scripts just don't work. Thoughts? Am I doing something obviously wrong? EDIT for more detail I've got a swarm of computers/VMs and a swarm of developers working on a swarm of projects. I need a simple central place to keep environment information, the most common is the "environment" (dev/stage/prod). The scheme that we've got (modifying *.wsgi programmatically) is turning out to be more fragile than we'd like. The main options that I see are: put things in the shell environment put things in other config files Getting things into the shell environment is the best, because we won't need to write yet more duplicated "what is my environment" code.

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  • How to create a WHM/cPanel account, without creating a new sub-domain?

    - by Cyclops
    I have a basic VPS (full root access), with WHM/cPanel, and am learning the ropes. I'm trying to create a new account for an existing domain (mysite.com), and so far WHM won't let me - it either wants a sub-domain or fake domain, but won't allow two accounts for one domain. In the beginning, there was only the root account, and it wouldn't let me login to cPanel - a quick chat with tech support, and I am informed that I need to create a second account, which I did. So now I have an account, call it ns1me, for domain mysite.com. Now I want to create a django account. I go through the same process, but WHM won't allow me to use mysite.com as the domain for django. The docs recommend a sub-domain, so I fill the box in with django.mysite.com. I then realize that has actually created a sub-domain - going to django.mysite.com shows me its home directory, along with helpful information about what version of Apache, Python, and other mods its running (thanks, Apache). I really don't want a sub-domain, so that's out. Another chat with tech support, and they recommend a fake domain name, as it won't create anything. Sure enough, using a domain of djangomysite.com works, and WHM allows me to create a django account. But of course, I can't send email to [email protected] (where I could to [email protected]). What I want, is to be able to create a second account, associated with mysite.com (so I can run cPanel logged in as django, send email to [email protected], etc) - without creating a whole new sub-domain, or fake domain.

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  • Where is SQLite on Nokia N810? How to get?

    - by klausnrooster
    I need SQLite3 with the TCL interface for a simple command-line app I use on all my PCs and want to use on my new (to me) Nokia N810. But "find" does not find any SQLite on the Nokia N810. Several apps use it, supposedly, like the maps/gps (poi.db), and others. I got sudo gainroot before using find, tried with wildcards * and dot . No luck. I guess it's embedded in the apps that use it? The N810's app manager doesn't offer SQLite. Apt-get has it and then fails with error: "Unable to fetch some archives, ..." The "update" and "--fix-missing" options do not help. I don't really want to get scratchbox and compile SQLite and TCL extension for it from sources. I looked at README and it seems like it might be straightforward. However [1] it's not clear what scratchbox download I would need (there are dozens in the Index of /download/files/sbox-releases/hathor/deb/i386), [2] I've never compiled any C sources successfully before, [3] and the whole mess entails a lot of learning curve for what is a very small one-off personal project. http://www.gronmayer.com/ has a few (sqlite (v. 2.8.17-4), libsqlite0 (v. 2.8.17-4), and libsqlite0-dev (v. 2.8.17-4)) but they appear to part of some huge package, may or may not include the TCL interface, ... and no I don't want to port my tiny app to Python. Is there some option I've overlooked? Must I get scratchbox and compile for ARM myself? Thanks for your time.

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  • Different font SIZES in a Text Editor, based on Script(Alphabet) type (ie. per Unicode Code-Block)

    - by fred.bear
    Some non-Latin-based scripts(alphabets) have more detail in their glyphs than do the Latin-based-script equivalents, and typically need a larger font to give the same degree of legibility (resolution-wise). Sometimes, both script types need to be present in the same file. Notepad++ allows different font SIZES (and colour, etc) courtesy of syntax-highlighting. This allows me to display larger-fonted non-Latin-based script in a // BIG-FONT comment. Although this has been quite handy for me in some situations, it is quite limited. A Word Processor can handle this scenario, but I'm not interested in that. I want a nice simple(?) plain(?) Text Editor to do it... on a per script-type basis... eg. mixing Latin-1 and Devanagari (and Mandarin, and ... Such a thing may not exits, but Notepad++ has shown that a simple(?) plain(?) Text Editor is capable of it. Does anyone know of such a Text Editor? ...Q. Why not a Word Processor? ...A. Because GCC and Python don't like that format! but UTF-8 is fine.

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  • Use bug tracker to get things done and manage personal tasks?

    - by Frank
    This is slightly off-topic, but can only be answered by programmers and is useful to many programmers: Do you think it is useful to use a bug tracking system to keep track of personal todo items and to Get Things Done? I have not tried that; in fact, I don't have much experience with bug tracking systems. For my todo lists, I have played around with Google Tasks and Remember The Milk, but both of them have shortcomings: Google Tasks: I like that you can create todo lists easily, can reorder items in the list and easily create hierarchies. But it is way too simplistic and does not allow to tag tasks or move tasks from one list to another. Remember The Milk: It is nice and sleek, but you cannot create hierarchies of tasks, cannot arbitrarily reorder tasks and cannot set dependencies of tasks. That's where a bug tracking system should come in: Since I think (maybe too much?) like a programmer, my tasks have a natural hierarchy and a tree of dependencies, like in a Makefile. Here are two examples: The task of writing my thesis is done when several milestones are done. Some of these milestones can run in parallel (writing background chapter, running experiments A, running experiments B), others depend on each other (writing main chapter depends on first getting results from experiments A). The same is true for more personal goals: I want to host a dinner party, which requires finding a good date, finishing the guest list, making invitations, finding nice recipes, cooking, ... For me, all these tasks involve hierarchical dependencies and milestones that bug tracking systems should be able to handle? Here is an article that explains how to do advanced GTD with Remember The Milk, but he has to use several workarounds: (1) add a general tag 'wait' to tasks that are waiting for others to be completed but you cannot enter the IDs of the tasks that they are waiting for, (2) starting some special tasks with "." so that they are at the top of the alphabetically sorted list and signal that others are 'below' it as subgoals. Bug tracking systems should be able to handle these things much more naturally? Does anyone have experience and can recommend a lightweight bug tracking system that might be good for this? Other requirements: Should run as web app, should allow me to tag a task with several tags (like 'work', 'fun', 'short-task', 'errands', ...).

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  • How to split HTML code with javascript or JQuery

    - by Dean
    Hi I'm making a website using JSP and servlets and I have to now break up a list of radio buttons to insert a textarea and a button. I have got the button and textarea to hide and show when you click on the radio button it shows the text area and button. But this only appears at the top and when there are hundreds on the page this will become awkward so i need a way for it to appear underneath. Here is what my HTML looks like when complied: <form action="addSpotlight" method="POST"> <table> <tr><td><input type="radio" value="29" name="publicationIDs" ></td><td>A System For Dynamic Server Allocation in Application Server Clusters, IEEE International Symposium on Parallel and Distributed Processsing with Applications, 2008</td> </tr> <tr><td><input type="radio" value="30" name="publicationIDs" ></td><td>Analysing BitTorrent's Seeding Strategies, 7th IEEE/IFIP International Conference on Embedded and Ubiquitous Computing (EUC-09), 2009</td> </tr> <tr><td><input type="radio" value="31" name="publicationIDs" ></td><td>The Effect of Server Reallocation Time in Dynamic Resource Allocation, UK Performance Engineering Workshop 2009, 2009</td> </tr> <tr><td><input type="radio" value="32" name="publicationIDs" ></td><td>idk, hello, 1992</td> </tr> <tr><td><input type="radio" value="33" name="publicationIDs" ></td><td>sad, safg, 1992</td> </tr> <div class="abstractWriteup"><textarea name="abstract"></textarea> <input type="submit" value="Add Spotlight"></div> </table> </form> Now here is what my JSP looks like: <form action="addSpotlight" method="POST"> <table> <%int i = 0; while(i<ids.size()){%> <tr><td><input type="radio" value="<%=ids.get(i)%>" name="publicationIDs" ></td><td><%=info.get(i)%></td> </tr> <%i++; }%> <div class="abstractWriteup"><textarea name="abstract"></textarea> <input type="submit" value="Add Spotlight"></div> </table> </form> Thanks in Advance Dean

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  • Advice for Architecture Design Logic for software application

    - by Prasad
    Hi, I have a framework of basic to complex set of objects/classes (C++) running into around 500. With some rules and regulations - all these objects can communicate with each other and hence can cover most of the common queries in the domain. My Dream: I want to provide these objects as icons/glyphs (as I learnt recently) on a workspace. All these objects can be dragged/dropped into the workspace. They have to communicate only through their methods(interface) and in addition to few iterative and conditional statements. All these objects are arranged finally to execute a protocol/workflow/dataflow/process. After drawing the flow, the user clicks the Execute/run button. All the user interaction should be multi-touch enabled. The best way to show my dream is : Jeff Han's Multitouch Video. consider Jeff is playing with my objects instead of the google maps. :-) it should be like playing a jigsaw puzzle. Objective: how can I achieve the following while working on this final product: a) the development should be flexible to enable provision for web services b) the development should enable easy web application development c) The development should enable client-server architecture - d) further it should also enable mouse based drag/drop desktop application like Adobe programs etc. I mean to say: I want to economize on investments. Now I list my efforts till now in design : a) Created an Editor (VB) where the user writes (manually) the object / class code b) On Run/Execute, the code is copied into a main() function and passed to interpreter. c) Catch the output and show it in the console. The interpreter can be separated to become a server and the Editor can become the client. This needs lot of standard client-server architecture work. But some how I am not comfortable in the tightness of this system. Without interpreter is there much faster and better embeddable solution to this? - other than writing a special compiler for these objects. Recently learned about AXIS-C++ can help me - looks like - a friend suggested. Is that the way to go ? Here are my questions: (pl. consider me a self taught programmer and NOT my domain) a) From the stage of C++ objects to multi-touch product, how can I make sure I will develop the parallel product/service models as well.? What should be architecture aspects I should consider ? b) What technologies are best suited for this? c) If I am thinking of moving to Cloud Computing, how difficult/ how redundant / how unnecessary my efforts will be ? d) How much time in months would it take to get the first beta ? I take the liberty to ask if any of the experts here are interested in this project, please email me: [email protected] Thank you for any help. Looking forward.

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  • How do I correct "Commit Failed. File xxx is out of date. xxx path not found."

    - by Ryan Taylor
    I have recently run into a particularly sticky issue regarding committing the result of a merge in subversion. Our Subversion server is @ 1.5.0 and my TortoiseSVN client is now @ 1.6.1. I am trying to merge a feature branch back into my trunk. The merge appears to work okay; however, the commit fails with the following error message. Commit failed (details follow): File 'flex/src/com/penbay/invision/portal/services/http/soap/ReportServices/GetAllBldgsParamsByRegionBySiteResultEvent.as' is out of date '/svn/ibis/!svn/wrk/531d459d-80fa-ea46-bfb4-940d79ee6d2e/visualization/trunk/source/flex/src/com/penbay/invision/portal/services/http/soap/ReportServices/GetAllBldgsParamsByRegionBySiteResultEvent.as' path not found You have to update your working copy first. My working trunk is up to date. I have even checked out a new one into a different folder to make sure there wasn't any local cruft messing with the merge. I have done some more research into this and I think part of the problem is user error. I think our problems are: We had some developers committing work with a subversion client before 1.5 and some after. I believe this has the potential to corrupt the merge info. In other branches we have performed partial merges. That is, we did not always perform merges at the root of the branch. This was to facilitate updating Flex and .NET efforts within the same branch. We performed cyclic (reflexive) merges on our branch. This was done because we had multiple parallel branches and we wanted to periodically update our branch with the latest code in trunk. All of these things are explicitly not recommended by the Subversion book/team. We have learned our lesson and now know the best practices. However, we first need to merge and commit our latest branch. What it the best way to correct the problems we are encountering? Would deleting all the merge info in the trunk and branch be a viable solution? No. I have done this but it does not resolve the error that I am getting above.

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  • C++ Unlocking a std::mutex before calling std::unique_lock wait

    - by Sant Kadog
    I have a multithreaded application (using std::thread) with a manager (class Tree) that executes some piece of code on different subtrees (embedded struct SubTree) in parallel. The basic idea is that each instance of SubTree has a deque that store objects. If the deque is empty, the thread waits until a new element is inserted in the deque or the termination criteria is reached. One subtree can generate objects and push them in the deque of another subtree. For convenience, all my std::mutex, std::locks and std::variable_condition are stored in a struct called "locks". The class Tree creates some threads that run the following method (first attempt) : void Tree::launch(SubTree & st, Locks & locks ) { /* some code */ std::lock_guard<std::mutex> deque_lock(locks.deque_mutex_[st.id_]) ; // lock the access to the deque of subtree st if (st.deque_.empty()) // check that the deque is still empty { // some threads are still running, wait for them to terminate std::unique_lock<std::mutex> wait_lock(locks.restart_mutex_[st.id_]) ; locks.restart_condition_[st.id_].wait(wait_lock) ; } /* some code */ } The problem is that "deque_lock" is still locked while the thread is waiting. Hence no object can be added in the deque of the current thread by a concurrent one. So I turned the lock_guard into a unique_lock and managed the lock/unlock manually : void launch(SubTree & st, Locks & locks ) { /* some code */ std::unique_lock<std::mutex> deque_lock(locks.deque_mutex_[st.id_]) ; // lock the access to the deque of subtree st if (st.deque_.empty()) // check that the deque is still empty { deque_lock.unlock() ; // unlock the access to the deque to enable the other threads to add objects // DATA RACE : nothing must happen to the unprotected deque here !!!!!! // some threads are still running, wait for them to terminate std::unique_lock<std::mutex> wait_lock(locks.restart_mutex_[st.id_]) ; locks.restart_condition_[st.id_].wait(wait_lock) ; } /* some code */ } The problem now, is that there is a data race, and I would like to make sure that the "wait" instruction is performed directly after the "deque_lock.unlock()" one. Would anyone know a way to create such a critical instruction sequence with the standard library ? Thanks in advance.

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  • how to implement a "soft barrier" in multithreaded c++

    - by Jason
    I have some multithreaded c++ code with the following structure: do_thread_specific_work(); update_shared_variables(); //checkpoint A do_thread_specific_work_not_modifying_shared_variables(); //checkpoint B do_thread_specific_work_requiring_all_threads_have_updated_shared_variables(); What follows checkpoint B is work that could have started if all threads have reached only checkpoint A, hence my notion of a "soft barrier". Typically multithreading libraries only provide "hard barriers" in which all threads must reach some point before any can continue. Obviously a hard barrier could be used at checkpoint B. Using a soft barrier can lead to better execution time, especially since the work between checkpoints A and B may not be load-balanced between the threads (i.e. 1 slow thread who has reached checkpoint A but not B could be causing all the others to wait at the barrier just before checkpoint B). I've tried using atomics to synchronize things and I know with 100% certainty that is it NOT guaranteed to work. For example using openmp syntax, before the parallel section start with: shared_thread_counter = num_threads; //known at compile time #pragma omp flush Then at checkpoint A: #pragma omp atomic shared_thread_counter--; Then at checkpoint B (using polling): #pragma omp flush while (shared_thread_counter > 0) { usleep(1); //can be removed, but better to limit memory bandwidth #pragma omp flush } I've designed some experiments in which I use an atomic to indicate that some operation before it is finished. The experiment would work with 2 threads most of the time but consistently fail when I have lots of threads (like 20 or 30). I suspect this is because of the caching structure of modern CPUs. Even if one thread updates some other value before doing the atomic decrement, it is not guaranteed to be read by another thread in that order. Consider the case when the other value is a cache miss and the atomic decrement is a cache hit. So back to my question, how to CORRECTLY implement this "soft barrier"? Is there any built-in feature that guarantees such functionality? I'd prefer openmp but I'm familiar with most of the other common multithreading libraries. As a workaround right now, I'm using a hard barrier at checkpoint B and I've restructured my code to make the work between checkpoint A and B automatically load-balancing between the threads (which has been rather difficult at times). Thanks for any advice/insight :)

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  • How to catch 'exceptions' for out of order execution in Workflow Foundation 4?

    - by Alex Key
    Hi, I am attempting to model a worklfow using a "WCF Workflow Service" in .net / vs 2010 that needs to handle out of order execution gracefully (but not allow it - if thath makes sense!?) For example I have 2 receive activities one called Initialize and the other called GetValue inside a FlowChart. In most cases Initialize should be called first and GetValue after (as modled in the flow chart). However if GetValue is executed before Initialize I do not want to return an "out of order" exception (although when I look at the WCF test client, I can't actually see an exception). But instead a custom exception saying something like "you must initialize first". In theory I could model this with lots of parallel activities and conditions to check if Initialized / Running / Terminated etc. But the business process I am modelling if very very similar to a state machine... except it must handle people executing things in the wrong order. Ideally I would like to catch the "out of order" exception (thought I don't think it's really an exception as such), check the 'exception' to see which function was attempted to run and then handle it. I have done some research around enabling AllowBufferedReceive. However I don't want to be able to execute out of order (I don't think), but instead give a detailed response if it does happen. I've looked at the new beta state machine template for WF 4 - but i'm not sure if it does what i'm after? I'm not sure if I have the wrong end of the stick, so any help would be greatly appreciated. [EDIT] To help clarify... Sorry it's a tricky one to explain. The standard I am trying to implement (the e-learning standard SCORM RTE) is structured like a state machine i.e. certain functions can only be executed in certain states. However the standard specifies that if the calling clients tries to execute a function that it is not meant to, then a warning should be issued... for example "you cannot use GetValue(), because you have not yet Initialized". Ideally I'd like to structure the workflow as the theoretical state machine and not need to have to use multiple if/else's to handle all the scenarios where something could be executed out-of-order. I'd like to catch a out-of-order exception (but I don't think there is such an exception - as it's not in the debugger) and rethrow it.

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  • Help me understand this "Programming pearls" bitsort program

    - by ardsrk
    Jon Bentley in Column 1 of his book programming pearls introduces a technique for sorting a sequence of non-zero positive integers using bit vectors. I have taken the program bitsort.c from here and pasted it below: /* Copyright (C) 1999 Lucent Technologies */ /* From 'Programming Pearls' by Jon Bentley */ /* bitsort.c -- bitmap sort from Column 1 * Sort distinct integers in the range [0..N-1] */ #include <stdio.h> #define BITSPERWORD 32 #define SHIFT 5 #define MASK 0x1F #define N 10000000 int a[1 + N/BITSPERWORD]; void set(int i) { int sh = i>>SHIFT; a[i>>SHIFT] |= (1<<(i & MASK)); } void clr(int i) { a[i>>SHIFT] &= ~(1<<(i & MASK)); } int test(int i){ return a[i>>SHIFT] & (1<<(i & MASK)); } int main() { int i; for (i = 0; i < N; i++) clr(i); /*Replace above 2 lines with below 3 for word-parallel init int top = 1 + N/BITSPERWORD; for (i = 0; i < top; i++) a[i] = 0; */ while (scanf("%d", &i) != EOF) set(i); for (i = 0; i < N; i++) if (test(i)) printf("%d\n", i); return 0; } I understand what the functions clr, set and test are doing and explain them below: ( please correct me if I am wrong here ). clr clears the ith bit set sets the ith bit test returns the value at the ith bit Now, I don't understand how the functions do what they do. I am unable to figure out all the bit manipulation happening in those three functions. Please help.

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  • multithreading with database

    - by Darsin
    I am looking out for a strategy to utilize multithreading (probably asynchronous delegates) to do a synchronous operation. I am new to multithreading so i will outline my scenario first. This synchronous operation right now is done for one set of data (portfolio) based on the the parameters provided. The (psudeo-code) implementation is given below: public DataSet DoTests(int fundId, DateTime portfolioDate) { // Get test results for the portfolio // Call the database adapter method, which in turn is a stored procedure, // which in turns runs a series of "rule" stored procs and fills a local temp table and returns it back. DataSet resultsDataSet = GetTestResults(fundId, portfolioDate); try { // Do some local processing on the results DoSomeProcessing(resultsDataSet); // Save the results in Test, TestResults and TestAllocations tables in a transaction. // Sets a global transaction which is provided to all the adapter methods called below // It is defined in the Base class StartTransaction("TestTransaction"); // Save Test and get a testId int testId = UpdateTest(resultsDataSet); // Adapter method, uses the same transaction // Update testId in the other tables in the dataset UpdateTestId(resultsDataSet, testId); // Update TestResults UpdateTestResults(resultsDataSet); // Adapter method, uses the same transaction // Update TestAllocations UpdateTestAllocations(resultsDataSet); // Adapter method, uses the same transaction // It is defined in the base class CommitTransaction("TestTransaction"); } catch { RollbackTransaction("TestTransaction"); } return resultsDataSet; } Now the requirement is to do it for multiple set of data. One way would be to call the above DoTests() method in a loop and get the data. I would prefer doing it in parallel. But there are certain catches: StartTransaction() method creates a connection (and transaction) every time it is called. All the underlying database tables, procedures are the same for each call of DoTests(). (obviously). Thus my question are: Will using multithreading anyway improve performance? What are the chances of deadlock especially when new TestId's are being created and the Tests, TestResults and TestAllocations are being saved? How can these deadlocked be handled? Is there any other more efficient way of doing the above operation apart from looping over the DoTests() method repeatedly?

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  • Several client waiting for the same event

    - by ff8mania
    I'm developing a communication API to be used by a lot of generic clients to communicate with a proprietary system. This proprietary system exposes an API, and I use a particular classes to send and wait messages from this system: obviously the system alert me that a message is ready using an event. The event is named OnMessageArrived. My idea is to expose a simple SendSyncMessage(message) method that helps the user/client to simply send a message and the method returns the response. The client: using ( Communicator c = new Communicator() ) { response = c.SendSync(message); } The communicator class is done in this way: public class Communicator : IDisposable { // Proprietary system object ExternalSystem c; String currentRespone; Guid currentGUID; private readonly ManualResetEvent _manualResetEvent; private ManualResetEvent _manualResetEvent2; String systemName = "system"; String ServerName = "server"; public Communicator() { _manualResetEvent = new ManualResetEvent(false); //This methods are from the proprietary system API c = SystemInstance.CreateInstance(); c.Connect(systemName , ServerName); } private void ConnectionStarter( object data ) { c.OnMessageArrivedEvent += c_OnMessageArrivedEvent; _manualResetEvent.WaitOne(); c.OnMessageArrivedEvent-= c_OnMessageArrivedEvent; } public String SendSync( String Message ) { Thread _internalThread = new Thread(ConnectionStarter); _internalThread.Start(c); _manualResetEvent2 = new ManualResetEvent(false); String toRet; int messageID; currentGUID = Guid.NewGuid(); c.SendMessage(Message, "Request", currentGUID.ToString()); _manualResetEvent2.WaitOne(); toRet = currentRespone; return toRet; } void c_OnMessageArrivedEvent( int Id, string root, string guid, int TimeOut, out int ReturnCode ) { if ( !guid.Equals(currentGUID.ToString()) ) { _manualResetEvent2.Set(); ReturnCode = 0; return; } object newMessage; c.FetchMessage(Id, 7, out newMessage); currentRespone = newMessage.ToString(); ReturnCode = 0; _manualResetEvent2.Set(); } } I'm really noob in using waithandle, but my idea was to create an instance that sends the message and waits for an event. As soon as the event arrived, checks if the message is the one I expect (checking the unique guid), otherwise continues to wait for the next event. This because could be (and usually is in this way) a lot of clients working concurrently, and I want them to work parallel. As I implemented my stuff, at the moment if I run client 1, client 2 and client 3, client 2 starts sending message as soon as client 1 has finished, and client 3 as client 2 has finished: not what I'm trying to do. Can you help me to fix my code and get my target? Thanks!

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  • Log4j: Issues about the FallbackErrorHandler

    - by rdogpink
    I am working on a client-server-application and wanted to implement a flexible Loggingframework, so I chose log4j, which doesn´t really evolve anymore, but it is still handy framework. Because the Logging happens along the network, i wanted a solution for the case, that the network drive isn´t available, so the Logger has to change its destination file(s). Now I wanted to use the FallbackErrorHandler (configured with a XML-File) from the Log4j-library and the implementation worked: When my network drive isn´t available, it switches to a local Logfile, so no logging should be lost. But I headded two problems since yesterday and couldn´t figure or find out, how to solve it. No return to initial Logging Configuration: When the network drive is on again and the Logger could write to the old destinations, log4j still logs at the local drive and I can´t figure out, how to notify the original (primary) Logger to start again. I also tried to attach a second Appender to the ErrorHandler, which should mirror the failed primary Logger, that it tries to write on the network destination and when the network is on again, it logs in both files, on the local and on the network drive. But unfortunately it didn´t work out, I only got a failure message that the ErrorHandler-content doesn´t fit. log4j:WARN The content of element type "errorHandler" must match "(param*,root-ref?,logger-ref*,appender-ref?)". This is the responsible code. <appender name="TraceAppender" class="org.apache.log4j.DailyRollingFileAppender"> <!-- The second appender-ref "TestAppender" leads to the error. --> <errorHandler class="org.apache.log4j.varia.FallbackErrorHandler"> <logger-ref ref="com.idoh"/> <appender-ref ref="TraceFallbackAppender"/> <appender-ref ref="TestAppender"/> </errorHandler> <param name="datePattern" value=".yyyy-MM-dd" /> <param name="file" value="logs/Trace.txt" /> <layout class="org.apache.log4j.PatternLayout"> <param name="ConversionPattern" value="%-6r %d{HH:mm:ss,SSS} [%t] %-5p - %m%n"/> </layout> </appender> So, how could I trigger log4j to reset to initial configuration or hold a second appender parallel to the "Local-Logger". My Application should work by itself and shouldn´t have to be restarted often. First Error message is swallowed: I recognized, that the first message, which leads to the switching between the primary logger and the FallbackErrorHandler (for example a logging-request to a readonly-File), is swallowed, so neither the primary logger logs it (because it can´t) nor the backup-Logger knows what it missed. So anybody else ran in this problem and could solve it? Or has any suggestions?

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  • objective C convert NSString to unsigned

    - by user1501354
    I have changed my question. I want to convert an NSString to an unsigned int. Why? Because I want to do parallel payment in PayPal. Below I have given my coding in which I want to convert the NSString to an unsigned int. My query is: //optional, set shippingEnabled to TRUE if you want to display shipping //options to the user, default: TRUE [PayPal getPayPalInst].shippingEnabled = TRUE; //optional, set dynamicAmountUpdateEnabled to TRUE if you want to compute //shipping and tax based on the user's address choice, default: FALSE [PayPal getPayPalInst].dynamicAmountUpdateEnabled = TRUE; //optional, choose who pays the fee, default: FEEPAYER_EACHRECEIVER [PayPal getPayPalInst].feePayer = FEEPAYER_EACHRECEIVER; //for a payment with multiple recipients, use a PayPalAdvancedPayment object PayPalAdvancedPayment *payment = [[PayPalAdvancedPayment alloc] init]; payment.paymentCurrency = @"USD"; // A payment note applied to all recipients. payment.memo = @"A Note applied to all recipients"; //receiverPaymentDetails is a list of PPReceiverPaymentDetails objects payment.receiverPaymentDetails = [NSMutableArray array]; NSArray *emailArray = [NSArray arrayWithObjects:@"[email protected]",@"[email protected]", nil]; for (int i = 1; i <= 2; i++) { PayPalReceiverPaymentDetails *details = [[PayPalReceiverPaymentDetails alloc] init]; // Customize the payment notes for one of the three recipient. if (i == 2) { details.description = [NSString stringWithFormat:@"Component %d", i]; } details.recipient = [NSString stringWithFormat:@"%@",[emailArray objectAtIndex:i-1]]; unsigned order; if (i==1) { order = [[feeArray objectAtIndex:0] unsignedIntValue]; } if (i==2) { order = [[amountArray objectAtIndex:0] unsignedIntValue]; } //subtotal of all items for this recipient, without tax and shipping details.subTotal = [NSDecimalNumber decimalNumberWithMantissa:order exponent:-4 isNegative:FALSE]; //invoiceData is a PayPalInvoiceData object which contains tax, shipping, and a list of PayPalInvoiceItem objects details.invoiceData = [[PayPalInvoiceData alloc] init]; //invoiceItems is a list of PayPalInvoiceItem objects //NOTE: sum of totalPrice for all items must equal details.subTotal //NOTE: example only shows a single item, but you can have more than one details.invoiceData.invoiceItems = [NSMutableArray array]; PayPalInvoiceItem *item = [[PayPalInvoiceItem alloc] init]; item.totalPrice = details.subTotal; [details.invoiceData.invoiceItems addObject:item]; [payment.receiverPaymentDetails addObject:details]; } [[PayPal getPayPalInst] advancedCheckoutWithPayment:payment]; Can anybody tell me how to do this conversion? Thanks and regards in advance.

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