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• ATI (fglrx) Dual monitor / laptop hot-plugging

  - by Brendan Piater

  I feel like I've gone back 5 years on my desktop today. I'll try not dump to much frustration here... I been running 12.04 since alpha with the ATI open source drivers and the gnome 3 desktop. I been generally very happy with them with only small issues along the way. Now of course it does not support 3D acceleration 100%, so games like my newly purchased Amnesia from the Humble bundle would not play. OK, no worries, the ATI driver is in the repos so let me have a go I thought. With all this testing that's been done with multi-monitor support, what could go wrong...? How I use my computer: It's laptop, with a HD 3670 card in it. I spend about 50% of the time working directly on the laptop (at home) and about 50% of the time working with an additional display connected (at work), multi desktop environment. What happening now: installed drivers things seemed to working, save some small other bugs (not critical) this morning I take my machine and plug the additional monitor into it, and nothing happens... ok fine. open "displays" try configure dual display, won't work open ati config "thing" (cause it is a thing, a crap thing) and set-up monitors there reboot it says (oh ffs, really.... ok) reboot, login and wow, I got a gnome 2 desktop (presume gnome 3 fall back) and no multi-monitor...great. (screenshot: http://ubuntuone.com/5tFe3QNFsTSIGvUSVLsyL7 ) after getting into a situation where I had to Ctrl + Alt + Del to get out of a frozen display, I eventually manage to set-up a single display desktop on the "main" monitor ok.. time to go home... unplug monitor... nothing happens.. oh boy here we go... try displays again, nothing, just hangs the display.. great. crash all the apps and reboot... So it's been a trying day... What I really hope is that someone else has figured out how to avoid this PAIN. Please help with a solution that: allows me run fglrx (so I can run the games I want) allows me to hot-plug a monitor to my laptop and remove it again allows me to change the display so include the hot-plugged monitor (preferable automatically like it did with the open drivers) Next best if that's not possible: switch between laptop only display and monitor only display easily (i.e. not having to reboot/logout/suspened etc) Really appreciate the time of anyone that has a solution. Thanks in advance. Regards Brendan PS: I guess I should file a bug about this too, so some direction as to the best place to file this would be appreciated too.

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• Library to fake intermittent failures according to tester-defined policy?

  - by crosstalk

  I'm looking for a library that I can use to help mock a program component that works only intermittently - usually, it works fine, but sometimes it fails. For example, suppose I need to read data from a file, and my program has to avoid crashing or hanging when a read fails due to a disk head crash. I'd like to model that by having a mock data reader function that returns mock data 90% of the time, but hangs or returns garbage otherwise. Or, if I'm stress-testing my full program, I could turn on debugging code in my real data reader module to make it return real data 90% of the time and hang otherwise. Now, obviously, in this particular example I could just code up my mock manually to test against a random() routine. However, I was looking for a system that allows implementing any failure policy I want, including: Fail randomly 10% of the time Succeed 10 times, fail 4 times, repeat Fail semi-randomly, such that one failure tends to be followed by a burst of more failures Any policy the tester wants to define Furthermore, I'd like to be able to change the failure policy at runtime, using either code internal to the program under test, or external knobs or switches (though the latter can be implemented with the former). In pig-Java, I'd envision a FailureFaker interface like so: interface FailureFaker { /** Return true if and only if the mocked operation succeeded. Implementors should override this method with versions consistent with their failure policy. */ public boolean attempt(); } And each failure policy would be a class implementing FailureFaker; for example there would be a PatternFailureFaker that would succeed N times, then fail M times, then repeat, and a AlwaysFailFailureFaker that I'd use temporarily when I need to simulate, say, someone removing the external hard drive my data was on. The policy could then be used (and changed) in my mock object code like so: class MyMockComponent { FailureFaker faker; public void doSomething() { if (faker.attempt()) { // ... } else { throw new RuntimeException(); } } void setFailurePolicy (FailureFaker policy) { this.faker = policy; } } Now, this seems like something that would be part of a mocking library, so I wouldn't be surprised if it's been done before. (In fact, I got the idea from Steve Maguire's Writing Solid Code, where he discusses this exact idea on pages 228-231, saying that such facilities were common in Microsoft code of that early-90's era.) However, I'm only familiar with EasyMock and jMockit for Java, and neither AFAIK have this function, or something similar with different syntax. Hence, the question: Do such libraries as I've described above exist? If they do, where have you found them useful? If you haven't found them useful, why not?

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• No GRUB Screen or recovery mode on Boot after 12.04 Upgrade

  - by Nick

  I tried the live boot CD and boot-repair, also loaded the Desktop install CD, and it looks like all partitions check out OK. However, when I try to boot Linux (the only bootable partition on the computer) I get a blank screen. Every so often the screen give me something akin to: Assuming write through cache Asking for cache data failed it appears to start booting, then hangs. Ctrl+Alt+Delete shuts down the machine The last message during boot is "STarting TiMidity++ ALSA midi emulation... [OK]" I used boot-repair to generate a boot info report. One thing looks odd to me- it reports a missing core.img on /dev/sda1. Here is the full info: Boot Info Script 0.61.full + Boot-Repair extra info [Boot-Info August 2nd 2012] ============================= Boot Info Summary: =============================== = Grub2 (v1.99) is installed in the MBR of /dev/sda and looks at sector 1 of the same hard drive for core.img. core.img is at this location and looks for (,msdos1)/boot/grub on this drive. = Windows is installed in the MBR of /dev/sdb. sda1: __________________________________________ File system: ext4 Boot sector type: Grub2 (v1.99) Boot sector info: Grub2 (v1.99) is installed in the boot sector of sda1 and looks at sector 18406911 of the same hard drive for core.img, but core.img can not be found at this location. Operating System: Ubuntu 12.04.1 LTS Boot files: /boot/grub/grub.cfg /etc/fstab /boot/extlinux/extlinux.conf /boot/grub/core.img sda2: __________________________________________ File system: Extended Partition Boot sector type: - Boot sector info: sda5: __________________________________________ File system: swap Boot sector type: - Boot sector info: sdb1: __________________________________________ File system: ntfs Boot sector type: Windows XP: NTFS Boot sector info: No errors found in the Boot Parameter Block. Operating System: Boot files: ============================ Drive/Partition Info: ============================= Drive: sda _______________________________________ Disk /dev/sda: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders, total 312581808 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes Partition Boot Start Sector End Sector # of Sectors Id System /dev/sda1 * 63 307,339,514 307,339,452 83 Linux /dev/sda2 307,339,515 312,576,704 5,237,190 5 Extended /dev/sda5 307,339,578 312,576,704 5,237,127 82 Linux swap / Solaris Drive: sdb _______________________________________ Disk /dev/sdb: 320.1 GB, 320072933376 bytes 255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes Partition Boot Start Sector End Sector # of Sectors Id System /dev/sdb1 2,048 625,142,447 625,140,400 7 NTFS / exFAT / HPFS "blkid" output: ____________________________________ Device UUID TYPE LABEL /dev/loop0 squashfs /dev/sda1 11b4d633-7863-40b2-a6ca-da5f82c3ad0b ext4 /dev/sda5 cb8d65f4-8cf9-4088-b804-e3dea2151033 swap /dev/sdb1 349E7C109E7BC8BE ntfs Personal1 ================================ Mount points: ================================= Device Mount_Point Type Options /dev/sdb1 /media/Personal1 fuseblk (rw,nosuid,nodev,allow_other,blksize=4096,default_permissions) /dev/sr0 /live/image iso9660 (ro,noatime) ...(a bunch of config file info- let me know if anyone wants to see it!) But usually I just get "Cannot Display This Video Mode", which I know means the video output is not usable by the monitor. I'm looking for a way to get into a recovery mode.I'd really like to avoid wiping the drive. Any thoughts?

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• Why is multithreading often preferred for improving performance?

  - by user1849534

  I have a question, it's about why programmers seems to love concurrency and multi-threaded programs in general. I'm considering 2 main approaches here: an async approach basically based on signals, or just an async approach as called by many papers and languages like the new C# 5.0 for example, and a "companion thread" that manages the policy of your pipeline a concurrent approach or multi-threading approach I will just say that I'm thinking about the hardware here and the worst case scenario, and I have tested this 2 paradigms myself, the async paradigm is a winner at the point that I don't get why people 90% of the time talk about multi-threading when they want to speed up things or make a good use of their resources. I have tested multi-threaded programs and async program on an old machine with an Intel quad-core that doesn't offer a memory controller inside the CPU, the memory is managed entirely by the motherboard, well in this case performances are horrible with a multi-threaded application, even a relatively low number of threads like 3-4-5 can be a problem, the application is unresponsive and is just slow and unpleasant. A good async approach is, on the other hand, probably not faster but it's not worst either, my application just waits for the result and doesn't hangs, it's responsive and there is a much better scaling going on. I have also discovered that a context change in the threading world it's not that cheap in real world scenario, it's in fact quite expensive especially when you have more than 2 threads that need to cycle and swap among each other to be computed. On modern CPUs the situation it's not really that different, the memory controller it's integrated but my point is that an x86 CPUs is basically a serial machine and the memory controller works the same way as with the old machine with an external memory controller on the motherboard. The context switch is still a relevant cost in my application and the fact that the memory controller it's integrated or that the newer CPU have more than 2 core it's not bargain for me. For what i have experienced the concurrent approach is good in theory but not that good in practice, with the memory model imposed by the hardware, it's hard to make a good use of this paradigm, also it introduces a lot of issues ranging from the use of my data structures to the join of multiple threads. Also both paradigms do not offer any security abut when the task or the job will be done in a certain point in time, making them really similar from a functional point of view. According to the X86 memory model, why the majority of people suggest to use concurrency with C++ and not just an async approach ? Also why not considering the worst case scenario of a computer where the context switch is probably more expensive than the computation itself ?

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• Why does switching users completely hang my system every time?

  - by Stéphane

  I have a fresh install of 11.04 64bit, with 2 administrator accounts and 4 normal accounts. The 4 normal accounts (the kids' accounts) don't have passwords, they can login simply by clicking on their names. When any of the users -- either admin or normal -- tries to switch to another account by clicking in the top-right corner of the screen and selecting another user, the screen goes black and the entire system locks up. Even CTRL+ALT+F1 through F7 does nothing. This is reproducible 100% of the time on this system. I can ssh into the box when the console locks up, and by running top, I see that Xorg is consuming about 100% of the CPU. Looking at the output of "ps axfu" in bash while the system is in this "locked up" state, here is the lightdm and X process tree: USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1153 0.0 0.1 183508 4292 ? Ssl Dec26 0:00 lightdm root 2187 0.4 4.6 265976 164168 tty7 Ss+ 00:43 0:21 \_ /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch stephane 2612 0.0 0.3 266400 10736 ? Ssl 01:52 0:00 \_ /usr/bin/gnome-session --session=ubuntu stephane 2650 0.0 0.0 12264 276 ? Ss 01:52 0:00 | \_ /usr/bin/ssh-agent /usr/bin/dbus-launch --exit-with-session /usr/bin/gnome-session --session=ubuntu stephane 2703 0.8 3.0 562068 106548 ? Sl 01:52 0:08 | \_ compiz stephane 2801 0.0 0.0 4264 584 ? Ss 01:52 0:00 | | \_ /bin/sh -c /usr/bin/compiz-decorator stephane 2802 0.0 0.3 265744 13772 ? Sl 01:52 0:00 | | \_ /usr/bin/unity-window-decorator ...cut... root 3024 80.6 0.3 107928 13088 tty8 Rs+ 01:53 12:34 \_ /usr/bin/X :1 -auth /var/run/lightdm/root/:1 -nolisten tcp vt8 -novtswitch That last process, pid #3024 in this case, is what has the CPU pegged. In case it matters (I suspect it might) here is what I think may be the relevant information for my video card, taken from /var/log/Xorg.0.log: [ 3392.653] (II) Loading /usr/lib/x86_64-linux-gnu/xorg/extra-modules/extra-modules.dpkg-tmp/modules/extensions/libglx.so [ 3392.653] (II) Module glx: vendor="FireGL - AMD Technologies Inc." [ 3392.653] compiled for 6.9.0, module version = 1.0.0 ... [ 3392.655] (II) LoadModule: "fglrx" [ 3392.655] (II) Loading /usr/lib/x86_64-linux-gnu/xorg/extra-modules/extra-modules.dpkg-tmp/modules/drivers/fglrx_drv.so [ 3392.672] (II) Module fglrx: vendor="FireGL - ATI Technologies Inc." [ 3392.672] compiled for 1.4.99.906, module version = 8.88.7 [ 3392.672] Module class: X.Org Video Driver ... [ 3392.759] (==) fglrx(0): ATI 2D Acceleration Architecture enabled [ 3392.759] (--) fglrx(0): Chipset: "AMD Radeon HD 6410D" (Chipset = 0x9644) Lastly: I did see this posting: Change user on 11.10 hangs system ...but I checked, and the libpam-smbpass package isn't installed on this system.

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• Why does creating dynamic bodies in JBox2D freeze my app?

  - by Amplify91

  My game hangs/freezes when I create dynamic bullet objects with Box2D and I don't know why. I am making a game where the main character can shoot bullets by the user tapping on the screen. Each touch event spawns a new FireProjectileEvent that is handled properly by an event queue. So I know my problem is not trying to create a new body while the box2d world is locked. My bullets are then created and managed by an object pool class like this: public Projectile getProjectile(){ for(int i=0;i<mProjectiles.size();i++){ if(!mProjectiles.get(i).isActive){ return mProjectiles.get(i); } } return mSpriteFactory.createProjectile(); } mSpriteFactory.createProjectile() leads to the physics component of the Projectile class creating its box2d body. I have narrowed the issue down to this method and it looks like this: public void create(World world, float x, float y, Vec2 vertices[], boolean dynamic){ BodyDef bodyDef = new BodyDef(); if(dynamic){ bodyDef.type = BodyType.DYNAMIC; }else{ bodyDef.type = BodyType.STATIC; } bodyDef.position.set(x, y); mBody = world.createBody(bodyDef); PolygonShape dynamicBox = new PolygonShape(); dynamicBox.set(vertices, vertices.length); FixtureDef fixtureDef = new FixtureDef(); fixtureDef.shape = dynamicBox; fixtureDef.density = 1.0f; fixtureDef.friction = 0.0f; mBody.createFixture(fixtureDef); mBody.setFixedRotation(true); } If the dynamic parameter is set to true my game freezes before crashing, but if it is false, it will create a projectile exactly how I want it just doesn't function properly (because a projectile is not a static object). Why does my program fail when I try to create a dynamic object at runtime but not when I create a static one? I have other dynamic objects (like my main character) that work fine. Any help would be greatly appreciated. This is a screenshot of a method profile I did: Especially notable is number 8. I'm just still unsure what I'm doing wrong. Other notes: I am using JBox2D 2.1.2.2. (Upgraded from 2.1.2.1 to try to fix this problem) When the application freezes, if I hit the back button, it appears to move my game backwards by one update tick. Very strange.

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• Why is my dual-boot Ubuntu partition showing up as a peripheral "root.disk"?

  - by Don

  I recently installed Ubuntu 12.04, which I had been booting from a usb key, as a dual-boot on my machine running Windows 7. From what I had read online while researching, I was prepared to have to shrink the Windows partition and all that. But I never had to - it really was just a few clicks here and there and it was installed. I'm still pretty confused about it, but whatever, it worked, and the two peacefully coexist on my machine, and I have broken things to fix before I worry about fixing unbroken things. So yesterday I got it in my head to look at my partitions (I was considering making an all new partition to install the Windows 8 Release Preview). What I saw confused me. Here's a screenshot of the disk utility. At this moment, there is nothing connected to my computer, and nothing in any of the optical drives/ports/card readers/etc. Can you help me figure out what's going on here? Don's Machine is, I believe, my Windows partition - that's the name I assigned my machine from Windows Explorer. PQSERVICE is from what I can find online also Windows, but having to do with backup. And SYSTEM REQUIRED, if I browse it in Ubuntu, is definitely something to do with booting, and I believe it is also Windows'. According to the sizes shown, those three together should use up my 500 GB HD. Then further down, as a "peripheral device", it lists that 31 GB disk. This is obviously my Ubuntu (Model:Linux Loop:root.disk), but why is it showing up as a peripheral? So, to sum up those questions and to add some more random ones I had: Why is Ubuntu showing up as a peripheral device? If the Windows sections take up all 500 GB, where does Ubuntu live? If I renamed the disk partitions, would my life become a nightmare (seriously - can I safely rename them)? Why didn't I have to resize the Windows partition in the first place? Would giving Ubuntu more space improve its performance (it hangs alot)? Is it possible to have a partition for each OS (Windows 7 & 8, Ubuntu), a partition for files, and a separate partition for backups? Is this towards the good or bad idea end of the spectrum? @Elfy, would that explain why it keeps hanging? I guess I'll backup my files, rip it out, and reinstall it correctly later on today.

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• SSH from external network refused

  - by wulfsdad

  I've installed open-ssh-server on my home computer(running Lubuntu 12.04.1) in order to connect to it from school. This is how I've set up the sshd_config file: # Package generated configuration file # See the sshd_config(5) manpage for details # What ports, IPs and protocols we listen for #Port 22 Port 2222 # Use these options to restrict which interfaces/protocols sshd will bind to #ListenAddress :: #ListenAddress 0.0.0.0 Protocol 2 # HostKeys for protocol version 2 HostKey /etc/ssh/ssh_host_rsa_key HostKey /etc/ssh/ssh_host_dsa_key HostKey /etc/ssh/ssh_host_ecdsa_key #Privilege Separation is turned on for security UsePrivilegeSeparation yes # Lifetime and size of ephemeral version 1 server key KeyRegenerationInterval 3600 ServerKeyBits 768 # Logging SyslogFacility AUTH #LogLevel INFO LogLevel VERBOSE # Authentication: LoginGraceTime 120 PermitRootLogin no StrictModes yes RSAAuthentication yes PubkeyAuthentication yes #AuthorizedKeysFile %h/.ssh/authorized_keys # Don't read the user's ~/.rhosts and ~/.shosts files IgnoreRhosts yes # For this to work you will also need host keys in /etc/ssh_known_hosts RhostsRSAAuthentication no # similar for protocol version 2 HostbasedAuthentication no # Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication #IgnoreUserKnownHosts yes # To enable empty passwords, change to yes (NOT RECOMMENDED) PermitEmptyPasswords no # Change to yes to enable challenge-response passwords (beware issues with # some PAM modules and threads) ChallengeResponseAuthentication no # Change to no to disable tunnelled clear text passwords #PasswordAuthentication yes # Kerberos options #KerberosAuthentication no #KerberosGetAFSToken no #KerberosOrLocalPasswd yes #KerberosTicketCleanup yes # GSSAPI options #GSSAPIAuthentication no #GSSAPICleanupCredentials yes X11Forwarding no X11DisplayOffset 10 PrintMotd no PrintLastLog yes TCPKeepAlive yes #UseLogin no #MaxStartups 10:30:60 #Banner /etc/issue.net Banner /etc/sshbanner.net # Allow client to pass locale environment variables AcceptEnv LANG LC_* Subsystem sftp /usr/lib/openssh/sftp-server # Set this to 'yes' to enable PAM authentication, account processing, # and session processing. If this is enabled, PAM authentication will # be allowed through the ChallengeResponseAuthentication and # PasswordAuthentication. Depending on your PAM configuration, # PAM authentication via ChallengeResponseAuthentication may bypass # the setting of "PermitRootLogin without-password". # If you just want the PAM account and session checks to run without # PAM authentication, then enable this but set PasswordAuthentication # and ChallengeResponseAuthentication to 'no'. UsePAM yes #specify which accounts can use SSH AllowUsers onlyme I've also configured my router's port forwarding table to include: LAN Ports: 2222-2222 Protocol: TCP LAN IP Address: "IP Address" displayed by viewing "connection information" from right-click menu of system tray Remote Ports[optional]: n/a Remote IP Address[optional]: n/a I've tried various other configurations as well, using primary and secondary dns, and also with specifying remote ports 2222-2222. I've also tried with TCP/UDP (actually two rules because my router requires separate rules for each protocol). With any router port forwarding configuration, I am able to log in with ssh -p 2222 -v localhost But, when I try to log in from school using ssh -p 2222 onlyme@IP_ADDRESS I get a "No route to host" message. Same thing when I use the "Broadcast Address" or "Default Route/Primary DNS". When I use the "subnet mask", ssh just hangs. However, when I use the "secondary DNS" I recieve a "Connection refused" message. :^( Someone please help me figure out how to make this work.

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• Evolution laggy due to IMAP -profile or due to some odd Sync -issue?

  - by Izzy

  I'm fighting with Evolution. Basically it's working fine -- but it is very slow to react in certain situations. Helper questions Could it be that changing away from Bonobo has to do with slowing-down? There might be some trouble with the new engine and "asynchronous actions". What to do about it? Are there e.g. any configuration files? I want to get the previous "working mood" back. How can I speed this thing up? Different scenarios when sending a mail, the composer window hangs there inactive for a couple of seconds, everything grayed out. Though there is a green check mark saying it's sent, I'm not sure a) why it's still blocking everything and b) whether I could simply close it without "breaking"/"losing" anything. In earlier versions, the composer window was closing pretty fast, and one could see the message being stored into the local "outbox" until it was sent, and one could immediately continue with the next task. I prefer that behaviour over the current, where I cannot do anything in the application until the window closes. switching between modules. Coming from mail and switching to the address book takes a couple of seconds. Same for switching to the calendar. I read about different "possible causes" and tried a few things: I only have 3 local address books, so no networking should be involved here. To make sure, I switched to offline mode and then tried to access the address book. No noticeable difference. I use 3 Google Calendars. Switching to offline mode made a minor difference, but so minor that it also could be "imagination" since one might have expected this in this case according to some reports, disabling the tasks should help. Well, it didn't in my case, as I don't use them regularly (just two local items stored here) Maybe I should also mention that I'm using the KDE4 desktop (so no Unity or Gnome, though both is installed on the computer). And I did not have this issue before I updated to 12.04.

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• All hail the Excel Queen

  - by Tim Dexter

  An excellent question this past week from dear ol Blighty; actually from Brian at Nextgen Clearing Ltd in the big smoke (London). Brian was developing an excel template and wanted to be able to reference the data fields multiple times inside the Excel template. Damn good question and I of course has some wacky solutions, from macros and cell referencing in Excel to pre-processing the data with an XSL stylesheet to copy the data multiple times so it could be referenced multiple times. All completely outlandish, enter our Queen of Excel, Shirley from the development team. Shirley is singlehandedly responsible for the Excel templates, I put her through six months of hell a few years back, with a host of Excel template requirements. She was more than up to the challenge and has developed some great features. One of those, is the ability to use the hidden XDO_METADATA sheet to map the data to custom named fields so they can be used multiple times in the template. So simple and very neat! Excel template and regular Excel users will know that you can only use the naming function once ie the names have to be unique across the workbook so you can not reuse a cell/group name. To get around this you can just come up with as many cell names as you want and map them in the XDO_METADATA sheet to the data columns/fields in your XML data set:. For example: XDO_?DEPTNO_SUMMARY?  <?DEPTNO?> XDO_?DNAME_SUMMARY?  <?DNAME?> XDO_GROUP_?G_D_DETAIL? <xsl:for-each-group select=".//G_D" group-by="./DEPTNO"> XDO_?DEPTNO_DETAIL? <?DEPTNO?> As you can see DEPTNO has been referenced twice and mapped to different named values in the left hand column. These values can then be used to name individual cells in the Excel template. You'll also notice a mix of Publisher <? ...?> and native XSL commands. So the world is your oyster on the mapping and the complexity you might need for calculations or string manipulation. Shirley has kindly built out a sample Excel template, data and result here so you can see how it all hangs together. the XDO_METADATA sheet is hidden, just right click on the sheet names and use the Unhide command to show it.

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• Why C++ people loves multithreading when it comes to performances?

  - by user1849534

  I have a question, it's about why programmers seems to love concurrency and multi-threaded programs in general. I'm considering 2 main approach here: an async approach basically based on signals, or just an async approach as called by many papers and languages like the new C# 5.0 for example, and a "companion thread" that maanges the policy of your pipeline a concurrent approach or multi-threading approach I will just say that I'm thinking about the hardware here and the worst case scenario, and I have tested this 2 paradigms myself, the async paradigm is a winner at the point that I don't get why people 90% of the time talk about concurrency when they wont to speed up things or make a good use of their resources. I have tested multi-threaded programs and async program on an old machine with an Intel quad-core that doesn't offer a memory controller inside the CPU, the memory is managed entirely by the motherboard, well in this case performances are horrible with a multi-threaded application, even a relatively low number of threads like 3-4-5 can be a problem, the application is unresponsive and is just slow and unpleasant. A good async approach is, on the other hand, probably not faster but it's not worst either, my application just waits for the result and doesn't hangs, it's responsive and there is a much better scaling going on. I have also discovered that a context change in the threading world it's not that cheap in real world scenario, it's infact quite expensive especially when you have more than 2 threads that need to cycle and swap among each other to be computed. On modern CPUs the situation it's not really that different, the memory controller it's integrated but my point is that an x86 CPUs is basically a serial machine and the memory controller works the same way as with the old machine with an external memory controller on the motherboard. The context switch is still a relevant cost in my application and the fact that the memory controller it's integrated or that the newer CPU have more than 2 core it's not bargain for me. For what i have experienced the concurrent approach is good in theory but not that good in practice, with the memory model imposed by the hardware, it's hard to make a good use of this paradigm, also it introduces a lot of issues ranging from the use of my data structures to the join of multiple threads. Also both paradigms do not offer any security abut when the task or the job will be done in a certain point in time, making them really similar from a functional point of view. According to the X86 memory model, why the majority of people suggest to use concurrency with C++ and not just an async aproach ? Also why not considering the worst case scenario of a computer where the context switch is probably more expensive than the computation itself ?

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• Application stuck in TCP retransmit

  - by SandeepJ

  I am running Linux kernel 3.13 (Ubuntu 14.04) on two Virtual Machines each of which operates inside two different servers running ESXi 5.1. There is a zeromq client-server application running between the two VMs. After running for about 10-30 minutes, this application consistently hangs due to inability to retransmit a lost packet. When I run the same setup over Ubuntu 12.04 (Linux 3.11), the application never fails If you notice below, "ss" (socket statistics) shows 1 packet lost, sk_wmem_queued of 14110 (i.e. w14110) and a high rto (120000). State Recv-Q Send-Q Local Address:Port Peer Address:Port ESTAB 0 12350 192.168.2.122:41808 192.168.2.172:55550 timer:(on,16sec,10) uid:1000 ino:35042 sk:ffff880035bcb100 <- skmem:(r0,rb648720,t0,tb1164800,f2274,w14110,o0,bl0) ts sack cubic wscale:7,7 rto:120000 rtt:7.5/3 ato:40 mss:8948 cwnd:1 ssthresh:21 send 9.5Mbps unacked:1 retrans:1/10 lost:1 rcv_rtt:1476 rcv_space:37621 Since this has happened so consistently, I was able to capture the TCP log in wireshark. I found that the packet which is lost does get retransmitted and even acknowledged by the TCP in the other OS (the sequence number is seen in the ACK), but the sender doesn't seem to understand this ACK and continues retransmitting. MTU is 9000 on both virtual machines and througout the route. The packets being sent are large in size. As I said earlier, this does not happen on Ubuntu 12.04 (kernel 3.11). So I did a diff on the TCP config options (seen via "sysctl -a |grep tcp ") between 14.04 and 12.04 and found the following differences. I also noticed that net.ipv4.tcp_mtu_probing=0 in both configurations. Left side is 3.11, right side is 3.13 <<net.ipv4.tcp_abc = 0 <<net.ipv4.tcp_cookie_size = 0 <<net.ipv4.tcp_dma_copybreak = 4096 14c11 << net.ipv4.tcp_early_retrans = 2 --- >> net.ipv4.tcp_early_retrans = 3 17c14 << net.ipv4.tcp_fastopen = 0 >> net.ipv4.tcp_fastopen = 1 20d16 << net.ipv4.tcp_frto_response = 0 26,27c22 << net.ipv4.tcp_max_orphans = 16384 << net.ipv4.tcp_max_ssthresh = 0 >> net.ipv4.tcp_max_orphans = 4096 29,30c24,25 << net.ipv4.tcp_max_tw_buckets = 16384 << net.ipv4.tcp_mem = 94377 125837 188754 >> net.ipv4.tcp_max_tw_buckets = 4096 >> net.ipv4.tcp_mem = 23352 31138 46704 34a30 >> net.ipv4.tcp_notsent_lowat = -1 My question to the networking experts on this forum : Are there any other debugging tools or options I can install/enable to dig further into why this TCP retransmit failure is occurring so consistently ? Are there any configuration changes which might account for this weird behaviour.

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• Why does chkdsk produce "Correcting error in index $I30 for file 33267" and then freeze?

  - by wcpro

  I am running chkdsk like this: chkdsk k: /x I get this error: Correcting error in index $I30 for file 33267. What does it mean? Here's the full problem: Microsoft Windows [Version 6.1.7600] Copyright (c) 2009 Microsoft Corporation. All rights reserved. C:\Windows\system32>chkdsk e: /r The type of the file system is NTFS. Volume label is RodDrobo. CHKDSK is verifying files (stage 1 of 5)... 162048 file records processed. File verification completed. 0 large file records processed. 0 bad file records processed. 0 EA records processed. 0 reparse records processed. CHKDSK is verifying indexes (stage 2 of 5)... 10 percent complete. (167130 of 208124 index entries processed) Correcting error in index $I30 for file 33267. Correcting error in index $I30 for file 33267. <--- it always reaches this spot, then hangs forever

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• MultiView 2000 terminal emulator not printing correctly to Generic/Text Printer on Windows 7

  - by FantaFan

  Guys & gals, Hope someone can shed some light on this. I am downloading reports from an AIX-based system by directing them to a TT printer which the terminal emulator (MultiView 2000) intercepts and directs to the default printer on the local system. This local printer is configured as a vanilla Generic/Text printer attached to a FILE port. When I print from AIX, the output is spooled down and the local printer prompts for a file name into which to save the file...but not under Windows 7. This has worked fine for many years, on both Win2K and WinXP. However, on Windows 7 the output gets spooled as a file into spool\PRINTERS (and looks as expected) but the print job then hangs with a status of "Error - Printing" and never prompts for a file name. I have to cancel the job. The Generic/Text printer works as expected with other applications. I have tried setting the printer to print directly rather than spooling but this only serves to hang the terminal session too. I've also tried to run the emulator in Windows 2000 Compatibility Mode and as Administrator in case it was something like that but with no luck. As you might expect, it does work fine in XP Mode (as long as I print to a printer defined therein and not the host's printer) but operationally this isn't going to be an option. Obviously this emulation software is a decade old (at least) and I could just cross/upgrade all the users (at a cost) but, before I do so, has anyone seen this sort of behaviour before and found some sort of fix? Remote OS: AIX 5 Client OS: Windows 7 Pro (32-bit) Printer: Generic/Text on a FILE port TE Software: MultiView 2000 (320-bit) Thanks in advance.

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• Generic/Text Printer on Windows 7 not prompting for file name

  - by FantaFan

  Guys & gals, Hope someone can shed some light on this. I am downloading reports from an AIX-based system by directing them to a TT printer which the terminal emulator (MultiView 2000) intercepts and directs to the default printer on the local system. This local printer is configured as a vanilla Generic/Text printer attached to a FILE port. When I print from AIX, the output is spooled down and the local printer prompts for a file name into which to save the file...but not under Windows 7. This has worked fine for many years, on both Win2K and WinXP. However, on Windows 7 the output gets spooled as a file into spool\PRINTERS (and looks as expected) but the print job then hangs with a status of "Error - Printing" and never prompts for a file name. I have to cancel the job. The Generic/Text printer works as expected with other applications. I have tried setting the printer to print directly rather than spooling but this only serves to hang the terminal session too. I've also tried to run the emulator in Windows 2000 Compatibility Mode and as Administrator in case it was something like that but with no luck. As you might expect, it does work fine in XP Mode (as long as I print to a printer defined therein and not the host's printer) but operationally this isn't going to be an option. Obviously this emulation software is a decade old (at least) and I could just cross/upgrade all the users (at a cost) but, before I do so, has anyone seen this sort of behaviour before and found some sort of fix? Remote OS: AIX 5 Client OS: Windows 7 Pro (32-bit) Printer: Generic/Text on a FILE port TE Software: MultiView 2000 (32-bit) Thanks in advance.

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• Cisco AnyConnect on IOS 12.4(20)T

  - by natacado

  There are plenty of tutorials on setting up AnyConnect on an ASA unit, and a handful of links noting that IOS 12.4(15) and later support AnyConnect, but I can't seem to find any good documentation about how to setup AnyConnect on IOS; most tutorials assume you only want a clientless VPN on IOS. the best I've found is this document on Cisco's site, but it's not working for me in practice - see below. This is all on a Cisco 881W: router#show version | include Version Cisco IOS Software, C880 Software (C880DATA-UNIVERSALK9-M), Version 12.4(20)T1, RELEASE SOFTWARE (fc3) ROM: System Bootstrap, Version 12.4(15r)XZ2, RELEASE SOFTWARE (fc1) The old SSL VPN Client seems to install just fine: router#show webvpn install status svc SSLVPN Package SSL-VPN-Client version installed: CISCO STC win2k+ 1.0.0 1,1,4,176 Thu 08/16/2007 12:37:00.43 However, when I install the AnyConnect client, after authenticating it hangs for a while during the self-update process, and stops with an error that the "AnyConnect package unavailable or corrupted." When I try to install the AnyConnect package on the router, I'm told that it's an invalid archive: router(config)#webvpn install svc flash:/webvpn/anyconnect-win-2.3.2016-k9.pkg SSLVPN Package SSL-VPN-Client (seq:2): installed Error: Invalid Archive Does anyone have a good sample on how to get the 2.x AnyConnect clients working with a Cisco device running IOS?

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• can't get php mail() working on Ubuntu desktop version with sendmail and postfix

  - by EricP

  I'm running Ubuntu 9.10 LAMP and trying to do a simple email test with PHP and I'm not getting any emails sent. mail("[email protected]", "eric-linux test", "test") or die("can't send mail"); I get no errors from PHP when running that script. In my php.ini file is: sendmail_path = /usr/lib/sendmail -t -i $ sudo ps aux | grep sendmail eric 2486 0.0 0.4 8368 2344 pts/0 T 14:52 0:00 sendmail -s “Hello world” [email protected] eric 8747 0.0 0.3 5692 1616 pts/2 T 16:18 0:00 sendmail eric 8749 0.0 0.3 5692 1636 pts/2 T 16:18 0:00 sendmail start eric 9190 0.0 0.3 5692 1636 pts/2 T 19:12 0:00 sendmail start eric 9192 0.0 0.3 5692 1616 pts/2 T 19:12 0:00 sendmail eric 9425 0.0 0.3 5692 1620 pts/1 T 19:37 0:00 sendmail eric 9427 0.0 0.3 6584 1636 pts/1 T 19:37 0:00 sendmail restart eric 9429 0.0 0.3 5692 1636 pts/1 T 19:38 0:00 /usr/lib/sendmail restart eric 9432 0.0 0.1 3040 804 pts/1 R+ 19:38 0:00 grep --color=auto sendmail When I run $ sendmail start it just hangs there doing nothing. I installed postfix also to see if it would help, but it didn't. I tried to see port 25: eric@eric-linux:~$ telnet localhost 25 Trying ::1... Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. 220 eric-linux ESMTP Postfix (Ubuntu) thanks

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• OSX telnet not working from localhost

  - by Stewie

  Telnet from my mac OSx doesn't work while it works from the AWS instances and other networks. I have no local firewalls. Nothing related in /var/log/system In the below transcript, the telnet hangs at "Trying 74.125.136.26..." I have tried many different addresses across multiple domains.. same result ! Rocky-Balboas-MacBook-Pro:~ rocky$ Rocky-Balboas-MacBook-Pro:~ rocky$ dig gmail.com MX +short 30 alt3.gmail-smtp-in.l.google.com. 40 alt4.gmail-smtp-in.l.google.com. 10 alt1.gmail-smtp-in.l.google.com. 20 alt2.gmail-smtp-in.l.google.com. 5 gmail-smtp-in.l.google.com. Rocky-Balboas-MacBook-Pro:~ rocky$ telnet alt2.gmail-smtp-in.l.google.com 25 Trying 74.125.136.26... ^C Rocky-Balboas-MacBook-Pro:~ rocky$ telnet localhost 80 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. ^C Connection closed by foreign host. Rocky-Balboas-MacBook-Pro:~ rocky$ edit: let the telnet command run and here are the results telnet: connect to address 74.125.136.27: Operation timed out Trying 2a00:1450:4013:c01::1a... telnet: connect to address 2a00:1450:4013:c01::1a: No route to host telnet: Unable to connect to remote host

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• Indefinite hang when restoring SQL 2005 database on a SQL 2008 server in EC2

  - by erinloy

  I'm trying to restore a 25 GB database backup taken from a Windows 2003/SQL 2005 machine to a Windows 2008/SQL 2008 machine in the Amazon EC2 cloud, using a .bak file and the SQL Management Studio. SQL Management Studio reports the restore reaches 100% complete, and then just hangs indefinitely (24+ hours) using a lot of CPU, until I restart the SQL Server service. Upon restart, SQL again uses a lot of CPU activity for what seems to be an indefinite amount of time, but the DB never comes online. Here are some details: - I have created two EBS volumes, one for DATA and one for LOGS, and I have set the default directories in SQL Server to the \DATA and \LOG directory on these respective volumes. (I wonder if the issue could be related to this, but the DB is too big to restore on the root drive.) - I have given the SQL Server user group full access to these directories. - The server can create a new empty test DB in these directories just fine, and can backup and restore the test DB. - I have tried both restoring of a .bak file and attaching directly to copies of the original .mdf/.ldf files, and the result is the same in both cases. - Both the .bak restore and the .mdf/.ldf attach occur from/to the EBS volumes. - I've also tried the above via SQL script, and "WITH RECOVERY", with no difference in the result, just less UI. - The backup contains two full text indexes. - I have to use "WITH MOVE" for most of the files in the backup. - There's nothing wrong with the backup or .mdf/.ldf files, as this works just fine on a Windows 2003/SQL 2005 machine in the Amazon EC2, but not Windows 2008/SQL 2008. - The DB is NOT marked as "Restoring" in the SQL Management Studio - it is just listed as a normal database, but throws errors when I try to do anything with it (expand the object browser tree, view properties, etc.) Any ideas?

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• Upgrading Ubuntu to 9.04 breaks ATI video card driver, VESA and ati/radeon drivers

  - by Neil

  I upgraded my Ubuntu 8.10 to 9.04, and it not only broke the ATI proprietary fglrx driver, but also the ability to use the VESA or open-source ati or radeon drivers. I have an ATI RV610 which is an ATI Radeon HD 2400 XT. I have Linux Kernel 2.6.27-14-generic and 2.6.28-13-generic. With fglrx, vesa, ati and radeon, the Xserver hangs the machine as soon as it starts by invoking X or startx, which is seen by observing that caps lock doesn't work. There's nothing useful in /var/log/Xorg.0.log, no errors at all. This is with either kernel. When I download a new proprietary driver from ATI, I install it successfully on kernel 2.6.27, and it doesn't hang when X starts up, but it just shows a blank screen and does nothing. I also can't CTRL+ALT+Backspace out of X at this point. In all the years I've used ATI's Linux drivers, this has happened almost every time I've upgraded my kernel, but it's been fixable with much effort. This time I'm really stuck. Does anyone know how to fix these problems?

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• Problem booting virtual machine after converting VMDK to VHD

  - by vg1890

  I used the VMWare VCenter Converter Standalone Client to convert a physical drive on my old PC to a virtual drive. The conversion worked fine and I ended up with a valid VMDK file. Next, I wanted to convert the VMDK to a VHD for use with Microsoft Virtual PC, since that's what I use on my new box. I used WinImage for the conversion and that worked fine, too. I can access the files from the virtual drive through WinImage. However, when I create a new virtual machine using Virtual PC and add the existing VHD file, the machine doesn't boot. The initial boot screen flashes with the amount of RAM and then the screen goes black. If I turn off the VM and reboot in safe mode I can see the drivers being loaded until eventually it gets to crcdisk.sys and hangs indefinitely. Any ideas how to fix this? I'm not opposed to starting over from scratch if there's another method to turn my physical machine into a Virtual PC VM. Thanks! EDIT - I should add that the virtual drive is a system boot drive and not a secondary drive. EDIT - I tried booting from the install CD and doing a repair. The result was that the system could not be repaired due to a "driver error."

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• CloneZilla PXE Boot Without NFS

  - by John

  I am trying to setup CloneZilla to be bootable via PXE without using NFS. I do not have NFS running on our PXE server and would like to keep it that way. However, most of the information that I have found online indicates that you need to setup NFS in order to PXE boot CloneZilla. I believe that I am pretty close in getting it to work, but am not sure where to go next. Listed below are the different PXE menu option configurations that I have used so far. LABEL Clonezilla Live MENU LABEL Clonezilla Live KERNEL utilities/clonezilla/vmlinuz APPEND initrd=utilities/clonezilla/initrd.img boot=live live-config noswap nolocales edd=on nomodeset ocs_live_run="ocs-live-general" ocs_live_extra_param="" ocs_live_keymap="" ocs_live_batch="no" o$ I have also tried the following append lines, without success: APPEND initrd=utilities/clonezilla/initrd.img boot=live union=aufs noswap noprompt vga=788 fetch=tftp://10.130.155.23/filesystem.squashfs APPEND initrd=utilities/clonezilla/initrd.img boot=live union=aufs noswap noprompt vga=normal nomodeset nosplash fetch=tftp://10.130.155.23/filesystem.squashfs Each of them have resulted in a no go with the following error: "Unable to find a live file system on the network". It looks like it gets to the point of trying to load the filesystem.squashfs file, hangs, and then throws the error. Any help would be greatly appreciated.

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• What is causing random hard freezes on my system? Kaspersky?

  - by Christian Ivicevic

  The last few weeks I experienced a new strange behavior of my computer. Sometimes Windows 7 just freezes with no real reason at all. While listening to music for example the playback hangs and you can hear a very nasty sound. Neither mouse nor keyboard input is handled and everything is just stuck. Using Ubuntu this does not happen, so I think it is just a matter of driver issues or a Windows 7 bug. Furthermore I am really suspicious about Kaspersky (Internet Security 11) and so I let it perform a complete virus scan while no other app is running. At about 50% it happened again and I needed to restart the computer by holding the power button the bad way... A really weird thing is that playing Skyrim this happened once, however music playback did not stop. Only the framerate dropped to 0 and sometimes for a few seconds I am able to move. Therefore I am really confused as furthermore no bluescreen pops up. Memtest told me that everything seems to be alright... Can anyone explain me which data you need about my hardware and software (and which tools tools to use to gather the informatik) to be able to provide any help on my problem?

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• ubuntu 9.04 pptp broken after a power failure

  - by kevin42

  I have a small Ubuntu 9.04 router setup as a NAT box and a PPTP server. After a power failure everything except the PPTP server still works. A windows client gets to "registering your computer on the network" but then says Error 742: The remote computer does not support the required data encryption type. I did some research and I think the problem is with the ppp_mppe module. When I try to run 'modprobe ppp_mppe' it hangs indefinitely. What would cause this hang? Any ideas how I can troubleshoot this further? Thanks for the help! UPDATE: I am still having the problem, however I have found some more information. When the first user tries to connect to pptp, the process list shows modprobe sha1 running, and one instance of modprobe ppp_mppe for each connection attempt. If I killall modprobe at this point the next connection attempt works, and everything is fine until the next reboot. I'm planning to do a clean install at some point in the future but I'd really like to get to the real cause of this.

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• MySQL remote access not working - Port Close?

  - by dave.zap

  I am not able to get a remote connection established to MySQL. From my pc I am able to telnet to 3306 on the existing server, but when I try the same with the new server it hangs for few minutes then returns # mysql -utest3 -h [server ip] -p Enter password: ERROR 2003 (HY000): Can't connect to MySQL server on '[server ip]' (110) Here is some output from the server. # nmap -sT -O localhost -p 3306 ... PORT STATE SERVICE 3306/tcp closed mysql ... # netstat -anp | grep mysql tcp 0 0 [server ip]:3306 0.0.0.0:* LISTEN 6349/mysqld unix 2 [ ACC ] STREAM LISTENING 12286 6349/mysqld /DATA/mysql/mysql.sock # netstat -anp | grep 3306 tcp 0 0 [server ip]:3306 0.0.0.0:* LISTEN 6349/mysqld unix 3 [ ] STREAM CONNECTED 3306 1411/audispd # lsof -i TCP:3306 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME mysqld 6349 mysql 10u IPv4 12285 0t0 TCP [domain]:mysql (LISTEN) I am running... OS CentOS release 5.8 (Final) mysql 5.5.28 (Remi) Note: Internal connections to mysql work fine. I have disabled IPtables, the box has no other firewall, it runs Apache on port 80 and ssh no problem. Had followed this tutorial - http://www.cyberciti.biz/tips/how-do-i-enable-remote-access-to-mysql-database-server.html I have bound the IP address in my.cnf user=mysql bind-address = [sever ip] port=3306 I even started over by deleting the mysql folder in my datastore and running mysql_install_db --datadir=/DATA/mysql --force Then recreated all the users as per the manual... http://dev.mysql.com/doc/refman/5.5/en/adding-users.html I have created one test user CREATE USER 'test'@'%' IDENTIFIED BY '[password]'; GRANT ALL PRIVILEGES ON *.* TO 'test'@'%' WITH GRANT OPTION; FLUSH PRIVILEGES; So all I can see is that the port is not really open. Where else might I look? thanks

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