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  • An old flaw in X Window System. How does it work?

    - by Legend
    I was going through an article today when it mentioned the following: "We've found many errors over the years. One of the absolute best was the following in the X Window System: if(getuid() != 0 && geteuid == 0) { ErrorF("Only root"); exit(1); } It allowed any local user to get root access. (The tautological check geteuid == 0 was intended to be geteuid() == 0. In its current form, it compress the address of geteuid to 0; given that the function exists, its address is never 0)." The article explained what was wrong with the code but I would like to know what it means to say that "It allowed any local user to get root access". I am not an expert in C but can someone give me an exact context in which this exploit would work? Specifically, what I mean is, lets say I am the local user, how would I get root access if we assume this code to be present somewhere?

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  • Why does XCode keep downloading old deleted profiles and duplicates of the same profile?

    - by Piepants
    If I refresh the profiles in XCode it: a) Pulls down ones that no longer exist. Profiles that have been deleted from the portal and are no longer there b) Pulls down multiple copies of the same profile. If I add a new device and then update the profiles to include that new device. Then XCode will pull down the new updated profile but also the same profile with an older date (even though the portal only shows one, the latest). If I delete them them XCode they re-appear. I'm having problems getting push notifications to work with an ad-hoc distrubtion and so want to ensure I am build with the latest profiles. This behaviour of XCode is irritating at least, and possibly the source of my problems at worst.

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  • Problem with NHibernate and saving - NHibernate doesn't detect changes and uses old values.

    - by Vilx-
    When I do this: Cat x = Session.Load<Cat>(123); x.Name = "fritz"; Session.Flush(); NHibernate detects the change and UPDATEs the DB. But, when I do this: Cat x = new Cat(); Session.Save(x); x.Name = "fritz"; Session.Flush(); I get NULL for name, because that's what was there when I called Session.Save(). Why doesn't NHibernate detect the changes - or better yet, take the values for the INSERT statement at the time of Flush()?

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  • Why a new instance uses logger from old instances?

    - by Roman
    I generate 2 instances in this way: gameManager manager1 = new CTManager(owner,players1,"en"); manager1.start(); gameManager manager2 = new CTManager(owner,players2,"en"); manager2.start(); The start() method of the gameManager looks like that: void start() { game.start(); } When I create the game instance I create a loger: log = Logger.getLogger("TestLog"); (log is a public field of the class in which the game belongs). In the game.start() I run many processes and give them a reference to the corresponding log. So, I expect that manager1 and manager2 will write to different files. But manager2 writes to its own file and to the log file of the manager1. Why can it happen?

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  • Is there any library/software available that can give me useful measurements of image quality?

    - by Thor84no
    I realise measuring image quality in software is going to be really difficult, and I'm not looking for a quick-fix. Googling this is largely showing up research papers and discussions that go a bit over my head, so I was wondering if anyone in the SO community had any experience with doing any rough image quality assessment? I want to use this to scan a few thousand images and whittle it down to a few dozen images that are most likely of poor quality. I could then show these to a user and leave the rest to them. Obviously there are many metrics that can be a part of whether an image is of high/low quality, I'd be happy with anything that could take an image as an input and give some reasonable metrics to any of the basic image quality metrics like sharpness, dynamic range, noise, etc., leaving it up to my software to determine what's acceptable and what isn't. Some of the images are poor quality because they've been up-scaled drastically. If there isn't a way of getting metrics like I suggested above, is there any way to detect that an image has been up-scaled like this?

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  • Is the 'var' keyword bad? Or am I just old school?

    - by WaggingSiberian
    Recently I overheard junior developer ask "why do you use 'var' so much?". The mid-level developer responded "I use VAR all the time. I love it! I don't have to figure out the type." I didn't have the time or energy to get into a religious war and hey, I'm still the new guy here :-) I understand var has its place. LINQ comes to mind. But I have also always been told the use of var represents lazy programming and I should just use the correct type to begin with. If it's an int, define it as an int, not a var. When reviewing code, seeing the type makes it easier to follow. My opinion is, it's just lazy but there are exceptions. Var also reminds me of the VB/VBA variant type. It also had its place. I recall (from many years ago) its usage being less-than-desirable type and it was rather resource hungry. Am I just being stuck in my ways? Should we start using var all the time as my co-worker does?

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  • What are you supposed to do with old SVN branches?

    - by John
    We had a SVN branch recently that had been merged back to trunk, and some more work on that feature/functional area was needed. I suggested using the same branch but was told you shouldn't re-use a branch once it has been integrated into trunk (a reference in SVN docs was given, I can't find it now). That suggests a branch is fairly useless once you merge back to trunk, so my question is once a branch is no longer needed, should it simply be deleted or kept?

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  • Why is the 'var' keyword bad? Or am I just old school?

    - by WaggingSiberian
    Recently I overheard junior developer ask "why do you use 'var' so much?". The mid-level developer responded "I use VAR all the time. I love it! I don't have to figure out the type." I didn't have the time or energy to get into a religious war and hey, I'm still the new guy here :-) I understand var has its place. LINQ comes to mind. But I have also always been told the use of var represents lazy programming and I should just use the correct type to begin with. If it's an int, define it as an int, not a var. When reviewing code, seeing the type makes it easier to follow. My opinion is, it's just lazy but there are exception. Var also reminds me of the VB/VBA variant type. It also had its place. I recall (from many years ago) its usage being less-than-desirable type and it was rather resource hungry. Am I just being stuck in my ways? Should we start using var all the time as my co-worker does?

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  • VS 2008, is there a way to search properties like the old vb6/EVB? CTRL+SHIFT?

    - by Davery
    I really miss the CTRL+SHIFT+CHAR searching of a property in VS 2008 that older IDE's had... typing CTRL+SHIFT+T got you to "tabindex" then Tag when pressed again. They dropped it in VS 2002 I believe, and the closest I could find to restoring any functionality like it was acorn's property window filter, which isn't exactly functional. Does anyone know of a way to get this functionality back? I hate having to browse through 30-40 properties in design mode, when a CTRL+SHIFT+T would get me right to text. Thanks!

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  • Problems setting vertical scrollbar value in a datagrid (old one, not the better DataGridView).

    - by user365581
    I need to save the selected row and the vertical scrollBar's position after a refresh. This is how I do it: int currRow = myGrid.CurrentRowIndex; int vScrollPos = ((ScrollBar)myGrid.Controls[1]).Value // some code that refreshes the data among other things myGrid.CurrentRowIndex = currRow; // this sets the property myGrid.Select(currRow); // this selects in UI (both commands required) ((ScrollBar)myGrid.Controls[1]).Value = vScrollPos; Here's my problem: The grid always jumps to a place where the selected row is at the bottom. setting the current row makes it happen - similar to EnsureVisible of newer grid implementations. But after that there's the vScrollBar repositioning - and it just doesn't work right. In debug I see that the scroll bar value gets updated. In the UI, if I hit the down/up arrow on the scrollbar it suddenly jumps to the right place - But if I don't click anything the grid is just in the wrong position. I tried refreshing the grid/scroll bar to force a redraw, but it doesn't help. The actual grid position is just not in sync with the vertical ScrollBar's value. Any ideas?

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  • Databound Label text displays old data upon save. Re-open record and data is correct?

    - by Mike Hestness
    I have a windows forms application. I have a main form and I have a button on this form to set a "Qualified" date/time stamp. I have a Databound label control that I set the value when the user clicks the button. This date/time stamp is working as far as displaying but when you click the save button it either shows blank or the previous date/time. If you then then close the record and re-open it the new date/time value is displayed so the data is getting to the database it's just not persisting in the dataset as new data?? Not sure why the databinding isn't refreshing the value. I have noticed this behavior even if I use a textbox, same thing if I do it programatically. If I manually type in a value it persists?? Here is the code I'm using in the click event of my button: string result = string.Empty; string jobOrderID = UnitOfWork.MasterDSBS.MJOBO[0].JC_IDNO.ToString(); string timeNow = DateTime.Now.ToString(); //Call Web service to make the update RadServices.Service1 rsWeb = new RadServices.Service1(); result = rsWeb.SetQualifiedDate(timeNow, jobOrderID ); //Changed the qualified label text. _btnQualify.Text = "Qualified"; rlQualifiedDate.Text = timeNow;

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  • What steps can you take to ensure sane build environments when compiling software?

    - by Chris Adams
    Hi guys, I've been stuck with a compilation problem when building a standardised virtual machine on CentOS 5.4, and I'm in the dark here as to a) why this error is occurring, and b) how to fix it, and in the hope that someone else stumbles across this problem too, I'm hoping someone can help me find the solution here. I'm getting a configure: error: newly created file is older than distributed files! error when trying to compile Ruby Enterprise like below when I try to run the installer, and the solutions offered to on the forums (of checking the tine, and touching the files to update the time associated with them) don't seem to be helping here. What steps can I take to work out what the cause of this problem? [vagrant@vagrant-centos-5 ruby-enterprise-1.8.7-2009.10]$ sudo ./installer Welcome to the Ruby Enterprise Edition installer This installer will help you install Ruby Enterprise Edition 1.8.7-2009.10. Don't worry, none of your system files will be touched if you don't want them to, so there is no risk that things will screw up. You can expect this from the installation process: 1. Ruby Enterprise Edition will be compiled and optimized for speed for this system. 2. Ruby on Rails will be installed for Ruby Enterprise Edition. 3. You will learn how to tell Phusion Passenger to use Ruby Enterprise Edition instead of regular Ruby. Press Enter to continue, or Ctrl-C to abort. Checking for required software... * C compiler... found at /usr/bin/gcc * C++ compiler... found at /usr/bin/g++ * The 'make' tool... found at /usr/bin/make * Zlib development headers... found * OpenSSL development headers... found * GNU Readline development headers... found -------------------------------------------- Target directory Where would you like to install Ruby Enterprise Edition to? (All Ruby Enterprise Edition files will be put inside that directory.) [/opt/ruby-enterprise] : -------------------------------------------- Compiling and optimizing the memory allocator for Ruby Enterprise Edition In the mean time, feel free to grab a cup of coffee. ./configure --prefix=/opt/ruby-enterprise --disable-dependency-tracking checking build system type... i686-pc-linux-gnu checking host system type... i686-pc-linux-gnu checking for a BSD-compatible install... /usr/bin/install -c checking whether build environment is sane... configure: error: newly created file is older than distributed files! Check your system clock This is a virtual machine running on virtualbox, and the time of the host and the virtual machine are identical, and up to date. I've also tried running this after updating time with an ntp-client, so no avail. I tried this after reading this post here of someone having a similar problem [vagrant@vagrant-centos-5 ruby-enterprise-1.8.7-2009.10]$ date Tue Apr 27 08:09:05 BST 2010 The other approach I've tried is to touch the top level the files in the build folder like suggested here, but this hasn't worked either (an to be honest, I'm not sure why it would have worked either) [vagrant@vagrant-centos-5 ruby-enterprise-1.8.7-2009.10]$ sudo touch ruby-enterprise-1.8.7-2009.10/* I'm not sure what I can do next here - the problem seems to be the bash configure script that returns this error error: newly created file is older than distributed files!, at line :2214 { echo "$as_me:$LINENO: checking whether build environment is sane" >&5 echo $ECHO_N "checking whether build environment is sane... $ECHO_C" >&6; } # Just in case sleep 1 echo timestamp > conftest.file # Do `set' in a subshell so we don't clobber the current shell's # arguments. Must try -L first in case configure is actually a # symlink; some systems play weird games with the mod time of symlinks # (eg FreeBSD returns the mod time of the symlink's containing # directory). if ( set X `ls -Lt $srcdir/configure conftest.file 2> /dev/null` if test "$*" = "X"; then # -L didn't work. set X `ls -t $srcdir/configure conftest.file` fi rm -f conftest.file if test "$*" != "X $srcdir/configure conftest.file" \ && test "$*" != "X conftest.file $srcdir/configure"; then # If neither matched, then we have a broken ls. This can happen # if, for instance, CONFIG_SHELL is bash and it inherits a # broken ls alias from the environment. This has actually # happened. Such a system could not be considered "sane". { { echo "$as_me:$LINENO: error: ls -t appears to fail. Make sure there is not a broken alias in your environment" >&5 echo "$as_me: error: ls -t appears to fail. Make sure there is not a broken alias in your environment" >&2;} { (exit 1); exit 1; }; } fi ### PROBLEM LINE #### # this line is the problem line - this is returned true, sometimes it isn't and I can't # see a pattern that that determines when this will test will pass or not. test "$2" = conftest.file ) then # Ok. : else { { echo "$as_me:$LINENO: error: newly created file is older than distributed files! Check your system clock" >&5 echo "$as_me: error: newly created file is older than distributed files! Check your system clock" >&2;} { (exit 1); exit 1; }; } fi the thing that makes this really frustrating is that this script works sometimes, when the VM has been running for an hour or so it works, but not at boot. There's nothing I see in the crontab that suggests any hourly tasks are run that might change the state of the system enough make a difference to this script working. I'm totally at a loss when it comes to debugging beyond here. What's the best approach to take here? Thanks

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  • nm-applet gone?

    - by welp
    nm-applet seems to have disappeared from my system. I am running 12.10. Here's what I get when I check my package manager logs: ? ~ grep network-manager /var/log/dpkg.log 2012-10-06 10:37:08 upgrade network-manager-gnome:amd64 0.9.6.2-0ubuntu5 0.9.6.2-0ubuntu6 2012-10-06 10:37:08 status half-configured network-manager-gnome:amd64 0.9.6.2-0ubuntu5 2012-10-06 10:37:08 status unpacked network-manager-gnome:amd64 0.9.6.2-0ubuntu5 2012-10-06 10:37:08 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu5 2012-10-06 10:37:08 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu5 2012-10-06 10:37:08 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu5 2012-10-06 10:37:08 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu5 2012-10-06 10:37:08 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu5 2012-10-06 10:37:08 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu5 2012-10-06 10:37:08 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu5 2012-10-06 10:37:09 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu5 2012-10-06 10:37:09 status unpacked network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-06 10:37:09 status unpacked network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-06 10:39:50 configure network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-06 10:39:50 status unpacked network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-06 10:39:50 status unpacked network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-06 10:39:50 status half-configured network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-06 10:39:50 status installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-28 22:27:23 status installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-28 22:27:23 remove network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-28 22:27:23 status half-configured network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-28 22:27:23 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-28 22:27:23 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-28 22:27:23 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-28 22:27:23 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-28 22:27:23 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-28 22:27:23 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-28 22:27:23 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-28 22:27:23 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-28 22:27:23 status config-files network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-28 22:27:23 status config-files network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:03 install network-manager-gnome:amd64 0.9.6.2-0ubuntu6 0.9.6.2-0ubuntu6 2012-10-31 19:58:03 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:03 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:03 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:03 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:03 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:03 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:03 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:03 status half-installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:03 status unpacked network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:03 status unpacked network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:06 configure network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:06 status unpacked network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:07 status unpacked network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:07 status half-configured network-manager-gnome:amd64 0.9.6.2-0ubuntu6 2012-10-31 19:58:07 status installed network-manager-gnome:amd64 0.9.6.2-0ubuntu6 ? ~ Unfortunately, I cannot find network-manager-applet package at all: ? ~ apt-cache search network-manager-applet ? ~ Here are the contents of /etc/apt/sources.list: ? ~ cat /etc/apt/sources.list # deb cdrom:[Ubuntu 12.04 LTS _Precise Pangolin_ - Release amd64 (20120425)]/ dists/precise/main/binary-i386/ # deb cdrom:[Ubuntu 12.04 LTS _Precise Pangolin_ - Release amd64 (20120425)]/ dists/precise/restricted/binary-i386/ # deb cdrom:[Ubuntu 12.04 LTS _Precise Pangolin_ - Release amd64 (20120425)]/ precise main restricted # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to # newer versions of the distribution. deb http://gb.archive.ubuntu.com/ubuntu/ quantal main restricted deb-src http://gb.archive.ubuntu.com/ubuntu/ quantal main restricted ## Major bug fix updates produced after the final release of the ## distribution. deb http://gb.archive.ubuntu.com/ubuntu/ quantal-updates main restricted deb-src http://gb.archive.ubuntu.com/ubuntu/ quantal-updates main restricted ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu ## team. Also, please note that software in universe WILL NOT receive any ## review or updates from the Ubuntu security team. deb http://gb.archive.ubuntu.com/ubuntu/ quantal universe deb-src http://gb.archive.ubuntu.com/ubuntu/ quantal universe deb http://gb.archive.ubuntu.com/ubuntu/ quantal-updates universe deb-src http://gb.archive.ubuntu.com/ubuntu/ quantal-updates universe ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu ## team, and may not be under a free licence. Please satisfy yourself as to ## your rights to use the software. Also, please note that software in ## multiverse WILL NOT receive any review or updates from the Ubuntu ## security team. deb http://gb.archive.ubuntu.com/ubuntu/ quantal multiverse deb-src http://gb.archive.ubuntu.com/ubuntu/ quantal multiverse deb http://gb.archive.ubuntu.com/ubuntu/ quantal-updates multiverse deb-src http://gb.archive.ubuntu.com/ubuntu/ quantal-updates multiverse ## N.B. software from this repository may not have been tested as ## extensively as that contained in the main release, although it includes ## newer versions of some applications which may provide useful features. ## Also, please note that software in backports WILL NOT receive any review ## or updates from the Ubuntu security team. deb http://gb.archive.ubuntu.com/ubuntu/ quantal-backports main restricted universe multiverse deb-src http://gb.archive.ubuntu.com/ubuntu/ quantal-backports main restricted universe multiverse deb http://security.ubuntu.com/ubuntu quantal-security main restricted deb-src http://security.ubuntu.com/ubuntu quantal-security main restricted deb http://security.ubuntu.com/ubuntu quantal-security universe deb-src http://security.ubuntu.com/ubuntu quantal-security universe deb http://security.ubuntu.com/ubuntu quantal-security multiverse deb-src http://security.ubuntu.com/ubuntu quantal-security multiverse ## Uncomment the following two lines to add software from Canonical's ## 'partner' repository. ## This software is not part of Ubuntu, but is offered by Canonical and the ## respective vendors as a service to Ubuntu users. # deb http://archive.canonical.com/ubuntu precise partner # deb-src http://archive.canonical.com/ubuntu precise partner ## This software is not part of Ubuntu, but is offered by third-party ## developers who want to ship their latest software. deb http://extras.ubuntu.com/ubuntu quantal main deb-src http://extras.ubuntu.com/ubuntu quantal main ? ~ Right now, I can't think of anything else. Happy to provide more info upon request.

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  • Pirates, Treasure Chests and Architectural Mapping

    Pirate 1: Why do pirates create treasure maps? Pirate 2: I do not know.Pirate 1: So they can find their gold. Yes, that was a bad joke, but it does illustrate a point. Pirates are known for drawing treasure maps to their most prized possession. These documents detail the decisions pirates made in order to hide and find their chests of gold. The map allows them to trace the steps they took originally to hide their treasure so that they may return. As software engineers, programmers, and architects we need to treat software implementations much like our treasure chest. Why is software like a treasure chest? It cost money, time,  and resources to develop (Usually) It can make or save money, time, and resources (Hopefully) If we operate under the assumption that software is like a treasure chest then wouldn’t make sense to document the steps, rationale, concerns, and decisions about how it was designed? Pirates are notorious for documenting where they hide their treasure.  Shouldn’t we as creators of software do the same? By documenting our design decisions and rationale behind them will help others be able to understand and maintain implemented systems. This can only be done if the design decisions are correctly mapped to its corresponding implementation. This allows for architectural decisions to be traced from the conceptual model, architectural design and finally to the implementation. Mapping gives software professional a method to trace the reason why specific areas of code were developed verses other options. Just like the pirates we need to able to trace our steps from the start of a project to its implementation,  so that we will understand why specific choices were chosen. The traceability of a software implementation that actually maps back to its originating design decisions is invaluable for ensuring that architectural drifting and erosion does not take place. The drifting and erosion is prevented by allowing others to understand the rational of why an implementation was created in a specific manor or methodology The process of mapping distinct design concerns/decisions to the location of its implemented is called traceability. In this context traceability is defined as method for connecting distinctive software artifacts. This process allows architectural design models and decisions to be directly connected with its physical implementation. The process of mapping architectural design concerns to a software implementation can be very complex. However, most design decision can be placed in  a few generalized categories. Commonly Mapped Design Decisions Design Rationale Components and Connectors Interfaces Behaviors/Properties Design rational is one of the hardest categories to map directly to an implementation. Typically this rational is mapped or document in code via comments. These comments consist of general design decisions and reasoning because they do not directly refer to a specific part of an application. They typically focus more on the higher level concerns. Components and connectors can directly be mapped to architectural concerns. Typically concerns subdivide an application in to distinct functional areas. These functional areas then can map directly back to their originating concerns.Interfaces can be mapped back to design concerns in one of two ways. Interfaces that pertain to specific function definitions can be directly mapped back to its originating concern(s). However, more complicated interfaces require additional analysis to ensure that the proper mappings are created. Depending on the complexity some Behaviors\Properties can be translated directly into a generic implementation structure that is ready for business logic. In addition, some behaviors can be translated directly in to an actual implementation depending on the complexity and architectural tools used. Mapping design concerns to an implementation is a lot of work to maintain, but is doable. In order to ensure that concerns are mapped correctly and that an implementation correctly reflects its design concerns then one of two standard approaches are usually used. All Changes Come From ArchitectureBy forcing all application changes to come through the architectural model prior to implementation then the existing mappings will be used to locate where in the implementation changes need to occur. Allow Changes From Implementation Or Architecture By allowing changes to come from the implementation and/or the architecture then the other area must be kept in sync. This methodology is more complex compared to the previous approach.  One reason to justify the added complexity for an application is due to the fact that this approach tends to detect and prevent architectural drift and erosion. Additionally, this approach is usually maintained via software because of the complexity. Reference:Taylor, R. N., Medvidovic, N., & Dashofy, E. M. (2009). Software architecture: Foundations, theory, and practice Hoboken, NJ: John Wiley & Sons  

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  • Performance issues when using SSD for a developer notebook (WAMP/LAMP stack)?

    - by András Szepesházi
    I'm a web application developer using my notebook as a standalone development environment (WAMP stack). I just switched from a Core2-duo Vista 32 bit notebook with 2Gb RAM and SATA HDD, to an i5-2520M Win7 64 bit with 4Gb RAM and 128 GB SDD (Corsair P3 128). My initial experience was what I expected, fast boot, quick load of all the applications (Eclipse takes now 5 seconds as opposed to 30s on my old notebook), overall great experience. Then I started to build up my development stack, both as LAMP (using VirtualBox with a debian guest) and WAMP (windows native apache + mysql + php). I wanted to compare those two. This still all worked great out, then I started to pull in my projects to these stacks. And here came the nasty surprise, one of those projects produced a lot worse response times than on my old notebook (that was true for both the VirtualBox and WAMP stack). Apache, php and mysql configurations were practically identical in all environments. I started to do a lot of benchmarking and profiling, and here is what I've found: All general benchmarks (Performance Test 7.0, HDTune Pro, wPrime2 and some more) gave a big advantage to the new notebook. Nothing surprising here. Disc specific tests showed that read/write operations peaked around 380M/160M for the SSD, and all the different sized block operations also performed very well. Started apache performance benchmarking with Apache Benchmark for a small static html file (10 concurrent threads, 500 iterations). Old notebook: min 47ms, median 111ms, max 156ms New WAMP stack: min 71ms, median 135ms, max 296ms New LAMP stack (in VirtualBox): min 6ms, median 46ms, max 175ms Right here I don't get why the native WAMP stack performed so bad, but at least the LAMP environment brought the expected speed. Apache performance measurement for non-cached php content. The php runs a loop of 1000 and generates sha1(uniqid()) inisde. Again, 10 concurrent threads, 500 iterations were used for the benchmark. Old notebook: min 0ms, median 39ms, max 218ms New WAMP stack: min 20ms, median 61ms, max 186ms New LAMP stack (in VirtualBox): min 124ms, median 704ms, max 2463ms What the hell? The new LAMP performed miserably, and even the new native WAMP was outperformed by the old notebook. php + mysql test. The test consists of connecting to a database and reading a single record form a table using INNER JOIN on 3 more (indexed) tables, repeated 100 times within a loop. Databases were identical. 10 concurrent threads, 100 iterations were used for the benchmark. Old notebook: min 1201ms, median 1734ms, max 3728ms New WAMP stack: min 367ms, median 675ms, max 1893ms New LAMP stack (in VirtualBox): min 1410ms, median 3659ms, max 5045ms And the same test with concurrency set to 1 (instead of 10): Old notebook: min 1201ms, median 1261ms, max 1357ms New WAMP stack: min 399ms, median 483ms, max 539ms New LAMP stack (in VirtualBox): min 285ms, median 348ms, max 444ms Strictly for my purposes, as I'm using a self contained development environment (= low concurrency) I could be satisfied with the second test's result. Though I have no idea why the VirtualBox environment performed so bad with higher concurrency. Finally I performed a test of including many php files. The application that I mentioned at the beginning, the one that was performing so bad, has a heavy bootstrap, loads hundreds of small library and configuration files while initializing. So this test does nothing else just includes about 100 files. Concurrency set to 1, 100 iterations: Old notebook: min 140ms, median 168ms, max 406ms New WAMP stack: min 434ms, median 488ms, max 604ms New LAMP stack (in VirtualBox): min 413ms, median 1040ms, max 1921ms Even if I consider that VirtualBox reached those files via shared folders, and that slows things down a bit, I still don't see how could the old notebook outperform so heavily both new configurations. And I think this is the real root of the slow performance, as the application uses even more includes, and the whole bootstrap will occur several times within a page request (for each ajax call, for example). To sum it up, here I am with a brand new high-performance notebook that loads the same page in 20 seconds, that my old notebook can do in 5-7 seconds. Needless to say, I'm not a very happy person right now. Why do you think I experience these poor performance values? What are my options to remedy this situation?

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  • Can someone clarify what this Joel On Software quote means?

    - by Bob
    I was reading Joel On Software today and ran across this quote: Without understanding functional programming, you can't invent MapReduce, the algorithm that makes Google so massively scalable. The terms Map and Reduce come from Lisp and functional programming. MapReduce is, in retrospect, obvious to anyone who remembers from their 6.001-equivalent programming class that purely functional programs have no side effects and are thus trivially parallelizable. What does he mean when he says functional programs have no side effects? And how does this make parallelizing trivial?

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  • App_Code in Web Client Software Factory, Is it a good idea.

    - by Blithe
    Hi guys, Just want to hear some opinion on adding App_Code in Web Client Software Factory (WCSF) project. The main purpose is to put reusable UI rendering codes which can be use by various pages. For WCSF, I guess only controller can share across pages within a module which does not seems to be a good place for UI stuff. Suggestions? :)

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  • Any software for pattern-matching and -rewriting source code?

    - by Steven A. Lowe
    I have some old software (in a language that's not dead but is dead to me ;-)) that implements a basic pattern-matching and -rewriting system for source code. I am considering resurrecting this code, translating it into a modern language, and open-sourcing the project as a refactoring power-tool. Before I go much further, I want to know if anything like this exists already (my google-fu is fanning air on this tonight). Here's how it works: the pattern-matching part matches source-code patterns spanning multiple lines of code using a template with binding variables, the pattern-rewriting part uses a template to rewrite the matched code, inserting the contents of the bound variables from the matching template matching and rewriting templates are associated (1:1) by a simple (unconditional) rewrite rule the software operates on the abstract syntax tree (AST) of the input application, and outputs a modified AST which can then be regenerated into new source code for example, suppose we find a bunch of while-loops that really should be for-loops. The following template will match the while-loop pattern: Template oldLoopPtrn int @cnt@ = 0; while (@cnt@ < @max@) { … @body@ ++@cnt@; } End_Template while the following template will specify the output rewrite pattern: Template newLoopPtrn for(int @cnt@ = 0; @cnt@ < @max@; @cnt@++) { @body@ } End_Template and a simple rule to associate them Rule oldLoopPtrn --> newLoopPtrn so code that looks like this int i=0; while(i<arrlen) { printf("element %d: %f\n",i,arr[i]); ++i; } gets automatically rewritten to look like this for(int i = 0; i < arrlen; i++) { printf("element %d: %f\n",i,arr[i]); } The closest thing I've seen like this is some of the code-refactoring tools, but they seem to be geared towards interactive rewriting of selected snippets, not wholesale automated changes. I believe that this kind of tool could supercharge refactoring, and would work on multiple languages (even HTML/CSS). I also believe that converting and polishing the code base would be a huge project that I simply cannot do alone in any reasonable amount of time. So, anything like this out there already? If not, any obvious features (besides rewrite-rule conditions) to consider? EDIT: The one feature of this system that I like very much is that the template patterns are fairly obvious and easy to read because they're written in the same language as the target source code, not in some esoteric mutated regex/BNF format.

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