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  • How to fix high Load_Cycle_Count laptop drive (TOSHIBA MK6006GAH in Vaio TX1XP)?

    - by Sam Brightman
    Hoping someone knows exactly what's going on here. It seems this drive has some combination of aggressive power saving settings and Ubuntu defaults that has massively increased the Load_Cycle_Count for the drive: https://wiki.ubuntu.com/DanielHahler/Bug59695 So the drive is now so slow that it cannot boot because it takes long enough to access the data that the kernel will not recognise it properly. I'm not worried about the data on the drive, but would really like to keep the laptop functioning. There is some indication that this is possible because the figure is still low 200,000s and most drives supposedly go to 600,000. Additionally, SMART tests pass and consider the drive healthy and without errors. But the really surprising thing was when I ran mhdd... Every single read came up red (slow) until I pressed 'R' for reset drive. I noticed the next read was normal speed, so held down 'R'. Magically the drive read perfectly for as long as I held the key BUT resumed slow (and noisy) seeking/reading after releasing. I don't think the source code to mhdd is available, so I'm not exactly sure what this means (besides, I don't know enough low-level HDD stuff either). It seems like the drive should be able to work, but is stuck trying to power save or something. There are no BIOS options on the laptop. Does anyone know how I can stop the drive from doing extremely slow/noisy operations like this? Or is constantly resetting the drive also damanging, and only causing it to work well by luck (i.e. not a suggestion that it's fixable)?

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  • How to Mount a USB "Thumb" Drive as "Fixed" in Windows (For Indexing)

    - by AMissico
    I have over 8GB in my "Code Library" that I maintain on a 64GB ScanDisk Ultra Backup USB Device. Windows Search 4.0 (installed on Windows XP) can index removable drives, but Windows 7 (which uses Windows Search 4.0) cannot because the USB device identifies itself as a Removable drive and Windows 7 refuses to index removable drives. How can I mount the USB Thumb Drive as Fixed instead of Removable? All suggestions welcome and greatly appreciated.

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  • Install Ubuntu 12.04 on Drive "D"?

    - by Bill Jones
    I have a Dell Inspiron 531S that originally came loaded with Windows Vista. A couple years ago I purchased a copy of Windows 7, formatted the hard drive and installed the updated operating system. In the process I formatted the 10 GB recovery drive partition on drive D as it was no longer needed for Windows Vista. I would really like to install Ubuntu 12.04 LTS alongside Windows 7 using the empty 10 GB drive D:. I have two questions. (1) Can Ubuntu be installed on a separate partition, a drive removed from the boot sector on drive C:? (2) If so would Grub be installed in the boot sector and properly select Windows 7 on drive C: or Ubuntu 12.04 on drive D?

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  • Combine Local Disk to another hard drive

    - by admintech
    I have a 150gb local disk on my Windows 7 x64 ultimate computer, i recently bought another 150gb hard drive and wish to merge/combine the 2 together to form 1 300gb hard drive. Is this possible to do without losing all the data on it? And i have thought about SATA but was curious if there was a faster easier option before i go ahead and take my pc apart

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  • Hard drive corrupts when fiddling with partitions.

    - by Archagon
    I've had problems with my hard drive ever since I got it a year ago. For the most part, it works fine, but whenever I try to do anything with partitions, be it adding, deleting, or resizing, some of the data in my other partitions inevitably corrupts. I've tried formatting my entire drive, but to no avail. What's going on?

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  • In a Virtual Machine, is the Virtual Processor using RAM or part of the Processor?

    - by Jason H
    I am running a 15" MacBook Pro (2.66GHz) and 4GB of RAM. I am considering downgrading to a 13 MacBook Pro (2.4GHz) with 8GB of RAM. Most of what I do at work is through Windows and I need to run it virtually. So my real question is when running a virtual machine will the virtual processor be utilizing RAM or part of the hosts processor? My assumption is that it will utilize the allocated RAM but I have seen zero documentation to support that.

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  • Resource Pool sharing in Hyper-V Virtual Machines

    - by user67905
    I understand that we can install Hyper-V on one server and run a number of Virtual Machines on it, upto the limit of resources of that server. I want to know if it is possible to install Hyper-V lumped on two or more servers, so that the Virtual Machines can use the underlying resources pool of both the servers? And also if that same is possible for an “n” number of servers, instead of just 2 servers.

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  • Virtual session on windows xp

    - by dotnet-practitioner
    What is the easiest way to install , setup, and run virtual session on my fresh install on my windows xp computer? I want to be able to browse , install a new software in a new virtual session instead of machine itself. What is available out there? What kind of software it would take and are there any free solutions out there? Easiest solution would be very helpful for me.

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  • Hard drive is working fine then next boot up shows up as a unformatted.

    - by evolvd
    The drive is a Samsung Spinpoint F3 HD103SJ 1TB. There are no SMART errors and the drive sounds healthy. Restarted the computer from the drive working fine and then noticed that the drive had the same drive letter but has RAW as the file system. I have a few file/partition recovery software titles available but since doing any scans on this drive takes about 2.5 hours I wanted to know if any one had any advice.

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  • how to return my losed drive

    - by sama
    the drive D in my computer has been losd i opend my computer but i didnot find it i don't know wher it is and i don't know how to return it i go to disck manaement i found it as a free space then i try to make it NTFS but it was needed to format it but i don't want to format it i need the data can any one help me to return my drive without losing my data

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  • Installing Windows XP through Pen Drive

    - by OrangeRind
    I want to install Windows XP on My desktop computer (only XP) but my cd drive has gone bust. I have tried to search for installation tutorials but I found only those in which people tell me how to install it ON the pen drive rather than FROM the pendrive. Please help out! Thanks in Advance

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  • Re-format thumb drive

    - by wizlog
    I was trying to put the Windows 8 Consumer Preview onto a thumb drive, when I was asked if I was OK with wiping it (I said yes I as it was blank). I had to sleep my computer during the wiping, and now I can't do anything with my dive. When I put it into my computer: When I click format disk: In short, the disk never reformats (I get an error message letting me know that Windows was unable to format the drive). Whats going on, and how do I fix it?

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  • win 7 back up utility cant detect external drive on a netbook

    - by decoder101
    im trying to image a new HP netbook via the windows 7 BACK UP util. however, it doesnt detect the external drive, although it's seen in my computer and BIOS. i tried using HP recovery manager with recovery disc creation but it says, no burning device installed although there is one... anyone successful in using the win7 back up utility? ive been tinkering this for a while but i cant make it right using an external dvd drive. unless i'll plug in an external hdd/

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  • Is a 1TB drive too big for a boot drive?

    - by CT
    Can the drive you choose to boot off affect performance? Would I receive faster boot/shutdown times if I were to choose a smaller drive? How would partitions affect performance/boot speed? Assuming all drives are the same RPM, lets say 7200.

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  • Hard drive restore on reboot on windows embedded

    - by sav
    My company has an old out of service device with windows embedded on it that we want to re purpose. Any changes to the drive (SD Card with 2 partitions), (ie: installed software, ip address, system settings, files) are reset/deleted when we reboot the device. We can successfully make changes to the drive by plugging it into a PC, but that has its limitations and we would like to be able to use our device. Can anyone tell us more about the technology used for doing this and how/if we can disable it?

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  • Can't Remove Logical Drive/Array from HP P400

    - by Myles
    This is my first post here. Thank you in advance for any assistance with this matter. I'm trying to remove a logical drive (logical drive 2) and an array (array "B") from my Smart Array P400. The host is a DL580 G5 running 64-bit Red Hat Enterprise Linux Server release 5.7 (Tikanga). I am unable to remove the array using either hpacucli or cpqacuxe. I believe it is because of "OS Status: LOCKED". The file system that lives on this array has been unmounted. I do not want to reboot the host. Is there some way to "release" this logical drive so I can remove the array? Note that I do not need to preserve the data on logical drive 2. I intend to physically remove the drives from the machine and replace them with larger drives. I'm using the cciss kernel module that ships with Red Hat 5.7. Here is some information pertaining to the host and the P400 configuration: [root@gort ~]# cat /etc/redhat-release Red Hat Enterprise Linux Server release 5.7 (Tikanga) [root@gort ~]# uname -a Linux gort 2.6.18-274.el5 #1 SMP Fri Jul 8 17:36:59 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux [root@gort ~]# rpm -qa | egrep '^(hp|cpq)' cpqacuxe-9.30-15.0 hp-health-9.25-1551.7.rhel5 hpsmh-7.1.2-3 hpdiags-9.3.0-466 hponcfg-3.1.0-0 hp-snmp-agents-9.25-2384.8.rhel5 hpacucli-9.30-15.0 [root@gort ~]# hpacucli HP Array Configuration Utility CLI 9.30.15.0 Detecting Controllers...Done. Type "help" for a list of supported commands. Type "exit" to close the console. => ctrl all show config detail Smart Array P400 in Slot 0 (Embedded) Bus Interface: PCI Slot: 0 Cache Serial Number: PA82C0J9SVW34U RAID 6 (ADG) Status: Enabled Controller Status: OK Hardware Revision: D Firmware Version: 7.22 Rebuild Priority: Medium Expand Priority: Medium Surface Scan Delay: 15 secs Surface Scan Mode: Idle Wait for Cache Room: Disabled Surface Analysis Inconsistency Notification: Disabled Post Prompt Timeout: 0 secs Cache Board Present: True Cache Status: OK Cache Ratio: 25% Read / 75% Write Drive Write Cache: Disabled Total Cache Size: 256 MB Total Cache Memory Available: 208 MB No-Battery Write Cache: Disabled Cache Backup Power Source: Batteries Battery/Capacitor Count: 1 Battery/Capacitor Status: OK SATA NCQ Supported: True Logical Drive: 1 Size: 136.7 GB Fault Tolerance: RAID 1 Heads: 255 Sectors Per Track: 32 Cylinders: 35132 Strip Size: 128 KB Full Stripe Size: 128 KB Status: OK Caching: Enabled Unique Identifier: 600508B100184A395356573334550002 Disk Name: /dev/cciss/c0d0 Mount Points: /boot 101 MB, /tmp 7.8 GB, /usr 3.9 GB, /usr/local 2.0 GB, /var 3.9 GB, / 2.0 GB, /local 113.2 GB OS Status: LOCKED Logical Drive Label: A0027AA78DEE Mirror Group 0: physicaldrive 1I:1:2 (port 1I:box 1:bay 2, SAS, 146 GB, OK) Mirror Group 1: physicaldrive 1I:1:1 (port 1I:box 1:bay 1, SAS, 146 GB, OK) Drive Type: Data Array: A Interface Type: SAS Unused Space: 0 MB Status: OK Array Type: Data physicaldrive 1I:1:1 Port: 1I Box: 1 Bay: 1 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM57RF40000983878FX Model: HP DG146BB976 Current Temperature (C): 29 Maximum Temperature (C): 35 PHY Count: 2 PHY Transfer Rate: Unknown, Unknown physicaldrive 1I:1:2 Port: 1I Box: 1 Bay: 2 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM55VQC000098388524 Model: HP DG146BB976 Current Temperature (C): 29 Maximum Temperature (C): 36 PHY Count: 2 PHY Transfer Rate: Unknown, Unknown Logical Drive: 2 Size: 546.8 GB Fault Tolerance: RAID 5 Heads: 255 Sectors Per Track: 32 Cylinders: 65535 Strip Size: 64 KB Full Stripe Size: 256 KB Status: OK Caching: Enabled Parity Initialization Status: Initialization Completed Unique Identifier: 600508B100184A395356573334550003 Disk Name: /dev/cciss/c0d1 Mount Points: None OS Status: LOCKED Logical Drive Label: A5C9C6F81504 Drive Type: Data Array: B Interface Type: SAS Unused Space: 0 MB Status: OK Array Type: Data physicaldrive 1I:1:3 Port: 1I Box: 1 Bay: 3 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM2H5PE00009802NK19 Model: HP DG146ABAB4 Current Temperature (C): 30 Maximum Temperature (C): 37 PHY Count: 1 PHY Transfer Rate: Unknown physicaldrive 1I:1:4 Port: 1I Box: 1 Bay: 4 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM28YY400009750MKPJ Model: HP DG146ABAB4 Current Temperature (C): 31 Maximum Temperature (C): 36 PHY Count: 1 PHY Transfer Rate: 3.0Gbps physicaldrive 2I:1:5 Port: 2I Box: 1 Bay: 5 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM2FGYV00009802N3GN Model: HP DG146ABAB4 Current Temperature (C): 30 Maximum Temperature (C): 38 PHY Count: 1 PHY Transfer Rate: Unknown physicaldrive 2I:1:6 Port: 2I Box: 1 Bay: 6 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM8AFAK00009920MMV1 Model: HP DG146BB976 Current Temperature (C): 31 Maximum Temperature (C): 41 PHY Count: 2 PHY Transfer Rate: Unknown, Unknown physicaldrive 2I:1:7 Port: 2I Box: 1 Bay: 7 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM2FJQD00009801MSHQ Model: HP DG146ABAB4 Current Temperature (C): 29 Maximum Temperature (C): 39 PHY Count: 1 PHY Transfer Rate: Unknown

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  • Dropped WD External Harddisk, now it's shown as "Not initialized"

    - by Phelios
    So, the WD my passport external harddisk is dropped, and after that, the computer is unable to read it anymore. I was hopping if I can just find another case to try if the harddisk is still readable, but looks like the hard drive itself is not a normal SATA or PATA drive. I think it's modified. So, I can't find another case that I can try on. In the computer, I still can see the drive in the "Disk Management", but it's shown as Uninitialized, no size, and no drive letter. I've also tried a couple of recovery tools. Some can't detect at all, there is one (find and mount software) that can detect but shows 0 size. None of them can recover the data. WD is willing to replace it with a new one, but I still need to recover the data. Any way I can recover the data? UPDATE: I tried initialized it from the windows Disk Manager, but it give error "The request could not be performed because of an I/O device error."

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  • What's the relationship between meta-circular interpreters, virtual machines and increased performance?

    - by Gomi
    I've read about meta-circular interpreters on the web (including SICP) and I've looked into the code of some implementations (such as PyPy and Narcissus). I've read quite a bit about two languages which made great use of metacircular evaluation, Lisp and Smalltalk. As far as I understood Lisp was the first self-hosting compiler and Smalltalk had the first "true" JIT implementation. One thing I've not fully understood is how can those interpreters/compilers achieve so good performance or, in other words, why is PyPy faster than CPython? Is it because of reflection? And also, my Smalltalk research led me to believe that there's a relationship between JIT, virtual machines and reflection. Virtual Machines such as the JVM and CLR allow a great deal of type introspection and I believe they make great use it in Just-in-Time (and AOT, I suppose?) compilation. But as far as I know, Virtual Machines are kind of like CPUs, in that they have a basic instruction set. Are Virtual Machines efficient because they include type and reference information, which would allow language-agnostic reflection? I ask this because many both interpreted and compiled languages are now using bytecode as a target (LLVM, Parrot, YARV, CPython) and traditional VMs like JVM and CLR have gained incredible boosts in performance. I've been told that it's about JIT, but as far as I know JIT is nothing new since Smalltalk and Sun's own Self have been doing it before Java. I don't remember VMs performing particularly well in the past, there weren't many non-academic ones outside of JVM and .NET and their performance was definitely not as good as it is now (I wish I could source this claim but I speak from personal experience). Then all of a sudden, in the late 2000s something changed and a lot of VMs started to pop up even for established languages, and with very good performance. Was something discovered about the JIT implementation that allowed pretty much every modern VM to skyrocket in performance? A paper or a book maybe?

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  • Looking for definitive answer to accessing a network drive/NAS/SMB drive via Windows 7 HOME and Windows 7 Professional. Is it possible and how?

    - by Rob
    I want to be able to access my Lacie 2Big network drive in Windows 7 Explorer. I have a machine with Windows 7 Home and one with Windows 7 Professional. Neither Windows 7, home or pro, can access the drive. The Windows 7 Home machine displays the drive in its Explorer, with the capacity, but on clicking the icon, I get another window, blank with the busy pointer which does not eventually stop. The drive is working perfectly. How do I know this? Because I can access it with no problems on my Apple Mac, Windows XP home and Ubuntu machines on the same network as the Windows 7 machines. Except for the Windows XP home machine that required Lacie ethernet agent program, the Mac and the Ubuntu machines needed no setup, the drive appeared like any other drive. So my 2 questions: Is it possible to access a network share drive, e.g. a NAS like Lacie 2big in Windows 7 Home Premium and Windows 7 Professional. If so how? I read on Microsoft's own forums and elsewhere that network sharing drives, e.g. via SambaSMB is NOT possible on Windows 7 Home. Is this true? http://social.technet.microsoft.com/Forums/en-US/w7itprovirt/thread/e08c3500-a722-4b44-b644-64f94f63c8e5/ This question is a more comprehensive re-write of my earlier question: Windows 7 / TCP/IP network share guide - looking for to resolve failure to mount lacie network drive but works on XP,Linux,Mac. ...where I haven't received a solving answer, and I have tried to find a solution myself. Lacie themselves haven't offered a definitive solving answer either, but I suspect it's not just their drives but SMB/network share/NAS in general... This is utterly pathetic that Windows 7 home cannot access something as simple as a network drive, especially given that Windows XP home can. My research so far: Apparently it is possible on Windows 7 Professional, via the Local Security Policy, only on Windows 7 Professional, not Windows 7 Home: http://www.sevenforums.com/tutorials/7357-local-security-policy-editor-open.html http://answers.microsoft.com/en-us/windows/forum/windows_7-security/accessing-local-security-policy-in-windows-7-home/0c8300d0-1d23-4de0-9b37-935c01a7d17a http://social.technet.microsoft.com/Forums/en-US/w7itprosecurity/thread/14fc5037-3386-4973-b5d8-2167272ff5ad/ http://www.tomshardware.com/forum/75-63-windows-samba-issue Another solution offered is editing the registry, doesn't look promising to me, fiddly and not guaranteed, hard to produce a complete solution I think, given that everyone's registry can vary. Registry key edit solutons: https://www.lacie.com/uk/mystuff/ticket/ticket.htm?tid=101278940 http://networksecurity.farzadbanifatemi.com/security-policy/how-to-access-local-security-policy-windows-7-home-premium Related: Does Windows 7 Home Premium support backing up to a network share Network Copy to Windows 7 File Share Fails and Kills Network Connection

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  • C++ virtual functions.Problem with vtable

    - by adivasile
    I'm doing a little project in C++ and I've come into some problems regarding virtual functions. I have a base class with some virtual functions: #ifndef COLLISIONSHAPE_H_ #define COLLISIONSHAPE_H_ namespace domino { class CollisionShape : public DominoItem { public: // CONSTRUCTOR //------------------------------------------------- // SETTERS //------------------------------------------------- // GETTERS //------------------------------------------------- virtual void GetRadius() = 0; virtual void GetPosition() = 0; virtual void GetGrowth(CollisionShape* other) = 0; virtual void GetSceneNode(); // OTHER //------------------------------------------------- virtual bool overlaps(CollisionShape* shape) = 0; }; } #endif /* COLLISIONSHAPE_H_ */ and a SphereShape class which extends CollisionShape and implements the methods above /* SphereShape.h */ #ifndef SPHERESHAPE_H_ #define SPHERESHAPE_H_ #include "CollisionShape.h" namespace domino { class SphereShape : public CollisionShape { public: // CONSTRUCTOR //------------------------------------------------- SphereShape(); SphereShape(CollisionShape* shape1, CollisionShape* shape2); // DESTRUCTOR //------------------------------------------------- ~SphereShape(); // SETTERS //------------------------------------------------- void SetPosition(); void SetRadius(); // GETTERS //------------------------------------------------- cl_float GetRadius(); cl_float3 GetPosition(); SceneNode* GetSceneNode(); cl_float GetGrowth(CollisionShape* other); // OTHER //------------------------------------------------- bool overlaps(CollisionShape* shape); }; } #endif /* SPHERESHAPE_H_ */ and the .cpp file: /*SphereShape.cpp*/ #include "SphereShape.h" #define max(a,b) (a>b?a:b) namespace domino { // CONSTRUCTOR //------------------------------------------------- SphereShape::SphereShape(CollisionShape* shape1, CollisionShape* shape2) { } // DESTRUCTOR //------------------------------------------------- SphereShape::~SphereShape() { } // SETTERS //------------------------------------------------- void SphereShape::SetPosition() { } void SphereShape::SetRadius() { } // GETTERS //------------------------------------------------- void SphereShape::GetRadius() { } void SphereShape::GetPosition() { } void SphereShape::GetSceneNode() { } void SphereShape::GetGrowth(CollisionShape* other) { } // OTHER //------------------------------------------------- bool SphereShape::overlaps(CollisionShape* shape) { return true; } } These classes, along some other get compiled into a shared library. Building libdomino.so g++ -m32 -lpthread -ldl -L/usr/X11R6/lib -lglut -lGLU -lGL -shared -lSDKUtil -lglut -lGLEW -lOpenCL -L/home/adrian/AMD-APP-SDK-v2.4-lnx32/lib/x86 -L/home/adrian/AMD-APP-SDK-v2.4-lnx32/TempSDKUtil/lib/x86 -L"/home/adrian/AMD-APP-SDK-v2.4-lnx32/lib/x86" -lSDKUtil -lglut -lGLEW -lOpenCL -o build/debug/x86/libdomino.so build/debug/x86//Material.o build/debug/x86//Body.o build/debug/x86//SphereShape.o build/debug/x86//World.o build/debug/x86//Engine.o build/debug/x86//BVHNode.o When I compile the code that uses this library I get the following error: ../../../lib/x86//libdomino.so: undefined reference to `vtable for domino::CollisionShape' ../../../lib/x86//libdomino.so: undefined reference to `typeinfo for domino::CollisionShape' Command used to compile the demo that uses the library: g++ -o build/debug/x86/startdemo build/debug/x86//CMesh.o build/debug/x86//CSceneNode.o build/debug/x86//OFF.o build/debug/x86//Light.o build/debug/x86//main.o build/debug/x86//Camera.o -m32 -lpthread -ldl -L/usr/X11R6/lib -lglut -lGLU -lGL -lSDKUtil -lglut -lGLEW -ldomino -lSDKUtil -lOpenCL -L/home/adrian/AMD-APP-SDK-v2.4-lnx32/lib/x86 -L/home/adrian/AMD-APP-SDK-v2.4-lnx32/TempSDKUtil/lib/x86 -L../../../lib/x86/ -L"/home/adrian/AMD-APP-SDK-v2.4-lnx32/lib/x86" (the -ldomino flag) And when I run the demo, I manually tell it about the library: LD_LIBRARY_PATH=../../lib/x86/:$AMDAPPSDKROOT/lib/x86:$LD_LIBRARY_PATH bin/x86/startdemo After reading a bit about virtual functions and virtual tables I understood that virtual tables are handled by the compiler and I shouldn't worry about it, so I'm a little bit confused on how to handle this issue. I'm using gcc version 4.6.0 20110530 (Red Hat 4.6.0-9) (GCC) Later edit: I'm really sorry, but I wrote the code by hand directly here. I have defined the return types in the code. I apologize to the 2 people that answered below. I have to mention that I am a beginner at using more complex project layouts in C++.By this I mean more complex makefiles, shared libraries, stuff like that.

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  • Visitor and templated virtual methods

    - by Thomas Matthews
    In a typical implementation of the Visitor pattern, the class must account for all variations (descendants) of the base class. There are many instances where the same method content in the visitor is applied to the different methods. A templated virtual method would be ideal in this case, but for now, this is not allowed. So, can templated methods be used to resolve virtual methods of the parent class? Given (the foundation): struct Visitor_Base; // Forward declaration. struct Base { virtual accept_visitor(Visitor_Base& visitor) = 0; }; // More forward declarations struct Base_Int; struct Base_Long; struct Base_Short; struct Base_UInt; struct Base_ULong; struct Base_UShort; struct Visitor_Base { virtual void operator()(Base_Int& b) = 0; virtual void operator()(Base_Long& b) = 0; virtual void operator()(Base_Short& b) = 0; virtual void operator()(Base_UInt& b) = 0; virtual void operator()(Base_ULong& b) = 0; virtual void operator()(Base_UShort& b) = 0; }; struct Base_Int : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_Long : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_Short : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_UInt : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_ULong : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; struct Base_UShort : public Base { void accept_visitor(Visitor_Base& visitor) { visitor(*this); } }; Now that the foundation is laid, here is where the kicker comes in (templated methods): struct Visitor_Cout : public Visitor { template <class Receiver> void operator() (Receiver& r) { std::cout << "Visitor_Cout method not implemented.\n"; } }; Intentionally, Visitor_Cout does not contain the keyword virtual in the method declaration. All the other attributes of the method signatures match the parent declaration (or perhaps specification). In the big picture, this design allows developers to implement common visitation functionality that differs only by the type of the target object (the object receiving the visit). The implementation above is my suggestion for alerts when the derived visitor implementation hasn't implement an optional method. Is this legal by the C++ specification? (I don't trust when some says that it works with compiler XXX. This is a question against the general language.)

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  • Why does virtual assignment behave differently than other virtual functions of the same signature?

    - by David Rodríguez - dribeas
    While playing with implementing a virtual assignment operator I have ended with a funny behavior. It is not a compiler glitch, since g++ 4.1, 4.3 and VS 2005 share the same behavior. Basically, the virtual operator= behaves differently than any other virtual function with respect to the code that is actually being executed. struct Base { virtual Base& f( Base const & ) { std::cout << "Base::f(Base const &)" << std::endl; return *this; } virtual Base& operator=( Base const & ) { std::cout << "Base::operator=(Base const &)" << std::endl; return *this; } }; struct Derived : public Base { virtual Base& f( Base const & ) { std::cout << "Derived::f(Base const &)" << std::endl; return *this; } virtual Base& operator=( Base const & ) { std::cout << "Derived::operator=( Base const & )" << std::endl; return *this; } }; int main() { Derived a, b; a.f( b ); // [0] outputs: Derived::f(Base const &) (expected result) a = b; // [1] outputs: Base::operator=(Base const &) Base & ba = a; Base & bb = b; ba = bb; // [2] outputs: Derived::operator=(Base const &) Derived & da = a; Derived & db = b; da = db; // [3] outputs: Base::operator=(Base const &) ba = da; // [4] outputs: Derived::operator=(Base const &) da = ba; // [5] outputs: Derived::operator=(Base const &) } The effect is that the virtual operator= has a different behavior than any other virtual function with the same signature ([0] compared to [1]), by calling the Base version of the operator when called through real Derived objects ([1]) or Derived references ([3]) while it does perform as a regular virtual function when called through Base references ([2]), or when either the lvalue or rvalue are Base references and the other a Derived reference ([4],[5]). Is there any sensible explanation to this odd behavior?

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  • Can't ping my Window 7 machine from within a Windows XP virtual machine

    - by Jonathan Conway
    I have Windows 7 installed as my primary operating system, on a laptop that's on my home network (wireless). I'm using Microsoft Virtual PC 2007 SP1 to run a virtual machine of Windows XP SP3, in which I want to access the Windows 7 instance, both to browse a shared folder and access the local Apache server. So far I can ping my Windows 7 IP address (IPv4) and access the apache server through the web browser through HTTP. However using my machine name never seems to work. Pinging it fails, and I can't access my apache server using it either. The problem seems to be something to do with my machine's name being registered under IPv6 rather than IPv4. I'm at a loss what to do. Should I try to set up IPv6 on the virtual machine? Not sure how to go about that. Or maybe I should somehow get my machine name on Windows 7 to work with IPv4? Although I think it already does, because I can ping it from a separate box (running Ubuntu), which is only registered under IPv6.

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