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• Samba shares won't automount on boot from fstab

  - by kelvin

  This question seems to have been asked a few times, but doesn't seem anybody has really solved it yet, at least not for my specific circumstance. I have FSAT setup to mount a CIFs share, but on boot up the share never gets mounted. However, if i run mount -a after boot up, it mounts everything just fine. Here's what my fstab looks like. Ignore the commented ones... I just did a few for testing purposes right now. //192.168.1.97/media /mnt/samba cifs credentials=/home/xbmc/.smbcredentials,rw,file_mode=0777,dir_mode=0777,sec=ntlm,auto 0 0 #//192.168.1.97/media/TV\040Shows /home/xbmc/TV\040Shows cifs credentials=/home/xbmc/.smbcredentials,rw,file_mode=0777,dir_mode=0777,sec=ntlm,auto //192.168.1.97/media/Movies /home/xbmc/Movies cifs credentials=/home/xbmc/.smbcredentials,rw,file_mode=0777,dir_mode=0777,sec=ntlm,auto 0 0 //192.168.1.97/media/Music /home/xbmc/Music cifs credentials=/home/xbmc/.smbcredentials,rw,file_mode=0777,dir_mode=0777,sec=ntlm,auto 0 0 #//192.168.1.97/media/3\040-\040My\040Pictures /home/xbmc/Pictures cifs credentials=/home/xbmc/.smbcredentials,rw,file_mode=0777,dir_mode=0777,sec=ntlm,auto #//192.168.1.97/media/XBMC /home/xbmc/Admin cifs credentials=/home/xbmc/.smbcredentials,rw,file_mode=0777,dir_mode=0777,sec=ntlm,auto Have seen a few things on the internet where it was believed its because the share isn't available yet (i.e. wifi not connected yet, etc) when it's attempting to mount. 1) Is there anyway to confirm that's the problem, 2) IF so, is there a solution? Is there some way to put a delay in fstab? Or how might i write a script to run mount -a a certain amount of time after boot? Found the option _netdev from a little research, included that in fstab but still the same result. Thanks for your help.

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• How to change mount to grant user write permissions?

  - by nals

  I am on TomatoUSB, and using the feature to have a NAS. The only way I can write to the Samba share is if I force root: [global] interfaces = 127.0.0.1, 192.168.1.1/24 bind interfaces only = no workgroup = WORKGROUP netbios name = TOMATO security = share wins support = yes name resolve order = wins lmhosts hosts bcast guest account = nobody [Public] path = /mnt/sda2 read only = no public = yes only guest = yes guest ok = yes browseable = yes comment = Network share force user = root writeable = yes I dont really like the idea having to use root to allow write access to my share. I have a samba account created already named nobody to allow access to the share. However every time I try to write I get access denied error. fstab: /dev/sda2 /mnt/sda2 vfat defaults 0 0 Further more every time I try to chmod 777 /tmp/mnt/sda2 the permissions are not changed, and no error is produced. They stay 755. drwxr-xr-x 2 root root 4096 Jun 4 01:49 sda2 Basically; how can I give the user nobody write permissions to my mount? dev name: /dev/sda2 dev mount: /tmp/mnt/sda2

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• Windows 7 / TCP/IP network share guide - looking for to resolve failure to mount lacie network drive but works on XP,Linux,Mac.

  - by Rob

  Can anyone advise me of a really good, readable, Windows 7 TCP/IP network share guide, book, or reference. I want this because I cannot mount my Lacie 2big ethernet network drive in Windows 7 (32 bit home), but I can mount it in Windows XP Home 32bit, Ubuntu Linux 10.04 and Apple MacOS X. This drive is being mounted via the accompanying Lacie Ethernet Agent in XP (which I believe uses "Bonjour" protocol), on Mac and Linux it works without further need for software. Another Super User user has the same problem, but no answer: Trouble accessing network drives in Windows 7 I hope my take on the question shows a better willingness to investigate and do some digging - and therefore invite some suggestions to help with this. The drive is detected by Windows 7 (i.e. speech bubble "network drive found") but on trying to open an Explorer window, this remains blank with the Windows busy pointer. I'd prefer not to reinstall Windows 7 to see if that cures the problem, I'd rather understand what is happening/not happening, perhaps even compare differences with Windows XP. Suggestions, please for such guides or even the original problem itself. Update Edit Rewrote question more comprehensively here: Mhttp://superuser.com/questions/304209/looking-for-definitive-answer-to-accessing-a-network-share-via-windows-7-home-and

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• Keeping sync in multiplayer RTS game that uses floating point arithmetic

  - by Calmarius

  I'm writing a 2D space RTS game in C#. Single player works. Now I want to add some multiplayer functionality. I googled for it and it seems there is only one way to have thousands of units continuously moving without a powerful net connection: send only the commands through the network while running the same simulation at every player. And now there is a problem the entire engine uses doubles everywhere. And floating point calculations are depends heavily on compiler optimalizations and cpu architecture so it is very hard to keep things syncronized. And it is not grid based at all, and have a simple phisics engine to move the space-ships (space ships have impulse and angular-momentum...). So recoding the entire stuff to use fixed point would be quite cumbersome (but probably the only solution). So I have 2 options so far: Say bye to the current code and restart from scratch using integers Make the game LAN only where there is enough bandwidth to have 8 players with thousands of units and sending the positions and orientation etc in (almost) every frame... So I looking for better opinions, (or even tips on migrating the code to fixed-point without messing everything up...)

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• Hard drive mounted at / , duplicate mounted hard drive after using MountManager

  - by HellHarvest

  possible duplicate post I'm running 12.04 64bit. My system is a dual boot for both Ubuntu and Windows7. Both operating systems are sharing the drive named "Elements". My volume named "Elements" is a 1TB SATA NTFS hard drive that shows up twice in the side bar in nautilus. One of the icons is functional and even has the convenient "eject" icon next to it. Below is a picture of the left menu in Nautilus, with System Monitor-File Systems tab open on top of it. Can someone advise me about how to get rid of this extra icon? I think the problem is much more deep-rooted than just a GUI glitch on Nautilus' part. The other icon does nothing but spit out the following error when I click on it (image below). This only happened AFTER I tried using Mount Manager to automate mounting the drive at start up. I've already uninstalled Mount Manager, and restarted, but the problem didn't go away. The hard drive does mount automatically now, so I guess that's cool. But now, every time I boot up now and open Nautilus, BOTH of these icons appear, one of which is fictitious and useless. According to the image above and the outputs of several other commands, it appears to be mounted at / In which case, no matter where I am in Nautilus when I try to click on that icon, of course it will tell me that that drive is in use by another program... Nautilus. I'm afraid of trying to unmount this hard drive (sdb6) because of where it appears to be mounted. I'm kind of a noob, and I have this gut feeling that tells me trying to unmount a drive at / will destroy my entire file system. This fear was further strengthened by the output of "$ fsck" at the very bottom of this post. Error immediately below when that 2nd "Elements" hard drive is clicked in Nautilus: Unable to mount Elements Mount is denied because the NTFS volume is already exclusively opened. The volume may be already mounted, or another software may use it which could be identified for example by the help of the 'fuser' command. It's odd to me that that error message above claims that it's an NTFS volume when everything else tell me that it's an ext4 volume. The actual hard drive "Elements" is in fact an NTFS volume. Here's the output of a few commands and configuration files that may be of interest: $ fuser -a / /: 2120r 2159rc 2160rc 2172r 2178rc 2180rc 2188r 2191rc 2200rc 2203rc 2205rc 2206r 2211r 2212r 2214r 2220r 2228r 2234rc 2246rc 2249rc 2254rc 2260rc 2261r 2262r 2277rc 2287rc 2291rc 2311rc 2313rc 2332rc 2334rc 2339rc 2343rc 2344rc 2352rc 2372rc 2389rc 2422r 2490r 2496rc 2501rc 2566r 2573rc 2581rc 2589rc 2592r 2603r 2611rc 2613rc 2615rc 2678rc 2927r 2981r 3104rc 4156rc 4196rc 4206rc 4213rc 4240rc 4297rc 5032rc 7609r 7613r 7648r 9593rc 18829r 18833r 19776r $ sudo df -h Filesystem Size Used Avail Use% Mounted on /dev/sdb6 496G 366G 106G 78% / udev 2.0G 4.0K 2.0G 1% /dev tmpfs 791M 1.5M 790M 1% /run none 5.0M 0 5.0M 0% /run/lock none 2.0G 672K 2.0G 1% /run/shm /dev/sda1 932G 312G 620G 34% /media/Elements /home/solderblob/.Private 496G 366G 106G 78% /home/solderblob /dev/sdb2 188G 100G 88G 54% /media/A2B24EACB24E852F /dev/sdb1 100M 25M 76M 25% /media/System Reserved $ sudo fdisk -l Disk /dev/sda: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00093cab Device Boot Start End Blocks Id System /dev/sda1 2048 1953519615 976758784 7 HPFS/NTFS/exFAT Disk /dev/sdb: 750.2 GB, 750156374016 bytes 255 heads, 63 sectors/track, 91201 cylinders, total 1465149168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x000e8d9b Device Boot Start End Blocks Id System /dev/sdb1 * 2048 206847 102400 7 HPFS/NTFS/exFAT /dev/sdb2 206848 392378768 196085960+ 7 HPFS/NTFS/exFAT /dev/sdb3 392380414 1465147391 536383489 5 Extended /dev/sdb5 1456762880 1465147391 4192256 82 Linux swap / Solaris /dev/sdb6 392380416 1448374271 527996928 83 Linux /dev/sdb7 1448376320 1456758783 4191232 82 Linux swap / Solaris Partition table entries are not in disk order $ cat /etc/fstab # <file system> <mount point> <type> <options> <dump> <pass> UUID=77039a2a-83d4-47a1-8a8c-a2ec4e4dfd0e / ext4 defaults 0 1 UUID=F6549CC4549C88CF /media/Elements ntfs-3g users 0 0 $ sudo blkid /dev/sda1: LABEL="Elements" UUID="F6549CC4549C88CF" TYPE="ntfs" /dev/sdb1: LABEL="System Reserved" UUID="5CDE130FDE12E156" TYPE="ntfs" /dev/sdb2: UUID="A2B24EACB24E852F" TYPE="ntfs" /dev/sdb6: UUID="77039a2a-83d4-47a1-8a8c-a2ec4e4dfd0e" TYPE="ext4" $ sudo blkid -c /dev/null (appears to be exactly the same as above) /dev/sda1: LABEL="Elements" UUID="F6549CC4549C88CF" TYPE="ntfs" /dev/sdb1: LABEL="System Reserved" UUID="5CDE130FDE12E156" TYPE="ntfs" /dev/sdb2: UUID="A2B24EACB24E852F" TYPE="ntfs" /dev/sdb6: UUID="77039a2a-83d4-47a1-8a8c-a2ec4e4dfd0e" TYPE="ext4" $ mount /dev/sdb6 on / type ext4 (rw) proc on /proc type proc (rw,noexec,nosuid,nodev) sysfs on /sys type sysfs (rw,noexec,nosuid,nodev) none on /sys/fs/fuse/connections type fusectl (rw) none on /sys/kernel/debug type debugfs (rw) none on /sys/kernel/security type securityfs (rw) udev on /dev type devtmpfs (rw,mode=0755) devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755) none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880) none on /run/shm type tmpfs (rw,nosuid,nodev) /dev/sda1 on /media/Elements type fuseblk (rw,noexec,nosuid,nodev,allow_other,blksize=4096) binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev) /home/solderblob/.Private on /home/solderblob type ecryptfs (ecryptfs_check_dev_ruid,ecryptfs_cipher=aes,ecryptfs_key_bytes=16,ecryptfs_unlink_sigs,ecryptfs_sig=76a47b0175afa48d,ecryptfs_fnek_sig=391b2d8b155215f7) gvfs-fuse-daemon on /home/solderblob/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=solderblob) /dev/sdb2 on /media/A2B24EACB24E852F type fuseblk (rw,nosuid,nodev,allow_other,default_permissions,blksize=4096) /dev/sdb1 on /media/System Reserved type fuseblk (rw,nosuid,nodev,allow_other,default_permissions,blksize=4096) $ ls -a . A2B24EACB24E852F Ubuntu 12.04.1 LTS amd64 .. Elements System Reserved $ cat /proc/mounts rootfs / rootfs rw 0 0 sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0 proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0 udev /dev devtmpfs rw,relatime,size=2013000k,nr_inodes=503250,mode=755 0 0 devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0 tmpfs /run tmpfs rw,nosuid,relatime,size=809872k,mode=755 0 0 /dev/disk/by-uuid/77039a2a-83d4-47a1-8a8c-a2ec4e4dfd0e / ext4 rw,relatime,user_xattr,acl,barrier=1,data=ordered 0 0 none /sys/fs/fuse/connections fusectl rw,relatime 0 0 none /sys/kernel/debug debugfs rw,relatime 0 0 none /sys/kernel/security securityfs rw,relatime 0 0 none /run/lock tmpfs rw,nosuid,nodev,noexec,relatime,size=5120k 0 0 none /run/shm tmpfs rw,nosuid,nodev,relatime 0 0 /dev/sda1 /media/Elements fuseblk rw,nosuid,nodev,noexec,relatime,user_id=0,group_id=0,allow_other,blksize=4096 0 0 binfmt_misc /proc/sys/fs/binfmt_misc binfmt_misc rw,nosuid,nodev,noexec,relatime 0 0 /home/solderblob/.Private /home/solderblob ecryptfs rw,relatime,ecryptfs_fnek_sig=391b2d8b155215f7,ecryptfs_sig=76a47b0175afa48d,ecryptfs_cipher=aes,ecryptfs_key_bytes=16,ecryptfs_unlink_sigs 0 0 gvfs-fuse-daemon /home/solderblob/.gvfs fuse.gvfs-fuse-daemon rw,nosuid,nodev,relatime,user_id=1000,group_id=1000 0 0 /dev/sdb2 /media/A2B24EACB24E852F fuseblk rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096 0 0 /dev/sdb1 /media/System\040Reserved fuseblk rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096 0 0 gvfs-fuse-daemon /root/.gvfs fuse.gvfs-fuse-daemon rw,nosuid,nodev,relatime,user_id=0,group_id=0 0 0 $ fsck fsck from util-linux 2.20.1 e2fsck 1.42 (29-Nov-2011) /dev/sdb6 is mounted. WARNING!!! The filesystem is mounted. If you continue you ***WILL*** cause ***SEVERE*** filesystem damage. Do you really want to continue<n>? no check aborted.

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• Finding furthermost point in game world

  - by user13414

  I am attempting to find the furthermost point in my game world given the player's current location and a normalized direction vector in screen space. My current algorithm is: convert player world location to screen space multiply the direction vector by a large number (2000) and add it to the player's screen location to get the distant screen location convert the distant screen location to world space create a line running from the player's world location to the distant world location loop over the bounding "walls" (of which there are always 4) of my game world check whether the wall and the line intersect if so, where they intersect is the furthermost point of my game world in the direction of the vector Here it is, more or less, in code: public Vector2 GetFurthermostWorldPoint(Vector2 directionVector) { var screenLocation = entity.WorldPointToScreen(entity.Location); var distantScreenLocation = screenLocation + (directionVector * 2000); var distantWorldLocation = entity.ScreenPointToWorld(distantScreenLocation); var line = new Line(entity.Center, distantWorldLocation); float intersectionDistance; Vector2 intersectionPoint; foreach (var boundingWall in entity.Level.BoundingWalls) { if (boundingWall.Intersects(line, out intersectionDistance, out intersectionPoint)) { return intersectionPoint; } } Debug.Assert(false, "No intersection found!"); return Vector2.Zero; } Now this works, for some definition of "works". I've found that the further out my distant screen location is, the less chance it has of working. When digging into the reasons why, I noticed that calls to Viewport.Unproject could result in wildly varying return values for points that are "far away". I wrote this stupid little "test" to try and understand what was going on: [Fact] public void wtf() { var screenPositions = new Vector2[] { new Vector2(400, 240), new Vector2(400, -2000), }; var viewport = new Viewport(0, 0, 800, 480); var projectionMatrix = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, viewport.Width / viewport.Height, 1, 200000); var viewMatrix = Matrix.CreateLookAt(new Vector3(400, 630, 600), new Vector3(400, 345, 0), new Vector3(0, 0, 1)); var worldMatrix = Matrix.Identity; foreach (var screenPosition in screenPositions) { var nearPoint = viewport.Unproject(new Vector3(screenPosition, 0), projectionMatrix, viewMatrix, worldMatrix); var farPoint = viewport.Unproject(new Vector3(screenPosition, 1), projectionMatrix, viewMatrix, worldMatrix); Console.WriteLine("For screen position {0}:", screenPosition); Console.WriteLine(" Projected Near Point = {0}", nearPoint.TruncateZ()); Console.WriteLine(" Projected Far Point = {0}", farPoint.TruncateZ()); Console.WriteLine(); } } The output I get on the console is: For screen position {X:400 Y:240}: Projected Near Point = {X:400 Y:629.571 Z:599.0967} Projected Far Point = {X:392.9302 Y:-83074.98 Z:-175627.9} For screen position {X:400 Y:-2000}: Projected Near Point = {X:400 Y:626.079 Z:600.7554} Projected Far Point = {X:390.2068 Y:-767438.6 Z:148564.2} My question is really twofold: what am I doing wrong with the unprojection such that it varies so wildly and, thus, does not allow me to determine the corresponding world point for my distant screen point? is there a better way altogether to determine the furthermost point in world space given a current world space location, and a directional vector in screen space?

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• Disable automount in Nautilus

  - by jimmybondy

  I have added my mount devices in /etc/fstab and they get correctly mounted (2nd partition with ntfs and nas-share with nfs). I have also disabled automount in Nautilus preferences by using dconf-editor (following this post): user@server:~$ gsettings list-recursively org.gnome.desktop.media-handling org.gnome.desktop.media-handling automount false org.gnome.desktop.media-handling automount-open false org.gnome.desktop.media-handling autorun-never false Now i see every mount device twice in Nautilus (the entry in fstab already mounted). When clicking on the other entry i get the eligible message mount.nfs: /media/nas_share is busy or already mounted How i can i disable the appearente of those devices in Nautilus? EDIT Regarding automount: I have only one line in /etc/auto.master: +auto.master

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• How does btrfs RAID work in degraded mode?

  - by turbo

  My idea was that (using loopback devices) it works like this Create the raid array sudo mkfs.btrfs -m raid1 -d raid1 /dev/loop1 /dev/loop2 You mount them sudo mount /dev/loop1 /mnt and mark them touch goodcondition You unmount and simulate disk failure (remove disk or delete loopback device loop2 in my case) You mount degraded -o degraded and mark again touch degraded You add the bad disk again sudo btrfs dev add /dev/loop2 You rebalance sudo btrfs fi ba /mnt And Raid 1 should work again. But that's not the case. sudo btrfs fi show: Total devices 3 FS bytes used 28.00KB devid 3 size 4.00GB used 264.00MB path /dev/loop1 devid 2 size 4.00GB used 272.00MB path /dev/loop2 *** Some devices missing The file degraded lives on loop1 but not on loop2 when loop2 is mounted in degraded mode. Why is that?

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• Ubuntu 11.10 mounting Synology DS212 problems

  - by Vigo

  I Have installed Ubuntu 11.10 and want to mount a synology ds212. I can see the diskstation in de filebrowser (before mounting with nfs) but can not open it. I've tried to mount it with nfs but no succes. Everything should be right at the Synology (nfs is on and maps are selected), and I've added a line in fstab. If I type sudo mount -a I dont't get an error. If I go to the mounted map I can't see anything in it..... What is going wrong? maybe router? Hope someone can help..!

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• Mounting filesystem with special user id set

  - by qbi

  I want to mount the device /dev/sda3 to the directory /foo/bar/baz. After mounting the directory should have the uid of user johndoe. So I did: sudo -u johndoe mkdir /foo/bar/baz stat -c %U /foo/bar/baz johndoe and added the following line to my /etc/fstab: /dev/sda3 /foo/bar/baz ext4 noexec,noatime,auto,owner,nodev,nosuid,user 0 1 When I do now sudo -u johndoe mount /dev/sda3 the command stat -c %U /foo/bar/baz results in root rather than johndoe. What is the best way to mount this ext4-filesystem with uid johndoe set?

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• USB Storage Device Automount

  - by matto1990

  Under Ubuntu 10.04 one of the problems which appeared is that USB devices would no longer automatically mount when plugged in. Normally I would get a pop up message asking what application I wanted to open the newly plugged in device with, however now that doesn't happen. This happens regardless of the way the device is formatted (NTFS or FAT32) and all other USB devices (printer, keyboard and mouse) work perfectly. My current solution is the mount them manually using sudo mount dev/... /medai/... however to be honest I'm just getting tired of having to do this. I'm happy to post any extra information you are likely to need. I know there will be lots of places I could look to find out what's going wrong but I have no idea where to start really.

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• why does my lubuntu recognizes only lubuntu instalation cds?

  - by Hardi

  I installed lubuntu from alternate cd a month ago. Now when I needed to read some cd's, the cd try won't open. It can be opened before ubuntu boots up. It can be opened after entering sudo eject -i off from console. But it won't mount any other cd-roms, than just the lubuntu live-cd and lubuntu alternate instal cd, where it was installed from. "mount: no medium found on /dev/sr0" as output, when try to mount anything else. Problem can't be in corrupted sd's, because othe computer, did recognize them well.

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• Floating point vs integer calculations on modern hardware

  - by maxpenguin

  I am doing some performance critical work in C++, and we are currently using integer calculations for problems that are inherently floating point because "its faster". This causes a whole lot of annoying problems and adds a lot of annoying code. Now, I remember reading about how floating point calculations were so slow approximately circa the 386 days, where I believe (IIRC) that there was an optional co-proccessor. But surely nowadays with exponentially more complex and powerful CPUs it makes no difference in "speed" if doing floating point or integer calculation? Especially since the actual calculation time is tiny compared to something like causing a pipeline stall or fetching something from main memory? I know the correct answer is to benchmark on the target hardware, what would be a good way to test this? I wrote two tiny C++ programs and compared their run time with "time" on Linux, but the actual run time is too variable (doesn't help I am running on a virtual server). Short of spending my entire day running hundreds of benchmarks, making graphs etc. is there something I can do to get a reasonable test of the relative speed? Any ideas or thoughts? Am I completely wrong? The programs I used as follows, they are not identical by any means: #include <iostream> #include <cmath> #include <cstdlib> #include <time.h> int main( int argc, char** argv ) { int accum = 0; srand( time( NULL ) ); for( unsigned int i = 0; i < 100000000; ++i ) { accum += rand( ) % 365; } std::cout << accum << std::endl; return 0; } Program 2: #include <iostream> #include <cmath> #include <cstdlib> #include <time.h> int main( int argc, char** argv ) { float accum = 0; srand( time( NULL ) ); for( unsigned int i = 0; i < 100000000; ++i ) { accum += (float)( rand( ) % 365 ); } std::cout << accum << std::endl; return 0; } Thanks in advance!

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• Floating point equality and tolerances

  - by doron

  Comparing two floating point number by something like a_float == b_float is looking for trouble since a_float / 3.0 * 3.0 might not be equal to a_float due to round off error. What one normally does is something like fabs(a_float - b_float) < tol. How does one calculate tol? Ideally tolerance should be just larger than the value of one or two of the least significant figures. So if the single precision floating point number is use tol = 10E-6 should be about right. However this does not work well for the general case where a_float might be very small or might be very large. How does one calculate tol correctly for all general cases? I am interested in C or C++ cases specifically.

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• Double precision floating point in CUDA

  - by cuda-dev

  Does CUDA support double precision floating point numbers ? Also need reasons for the same.

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• c++ floating point to integer type conversions

  - by moala

  What are the different techniques for a floating point type to an integer type conversion, in c++?

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• How do I mount a "GPT Protective Partition" in Windows XP?

  - by Michael Haren

  I formatted an external USB harddrive while it was connected to a 32-bit Windows 2003 Server Std. edition server. After loading it up with files, I moved it to my Windows XP SP3 where it didn't show up automatically in My Computer. I opened up Computer ManagementDisk Management and see it listed as a "Health (GPT Protective Parititon)". What's up with that? Can I mount it?

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• How do software .dmg files mount or work in OS X?

  - by ymasood

  I am a new Mac user and have an iMac. Coming from the Windows world where everything is installer based, OS X seems to mount .dmg files and run them. I've seen this happen prior to an install and later it requests us to move an icon to the Applications folder. Could someone help me unclutter the install process on OS X. What or how does it work? Thanks in advance!

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• Does anyone have database, programming language/framework suggestions for a GUI point of sale system

  - by Jason Down

  Our company has a point of sale system with many extras, such as ordering and receiving functionality, sales and order history etc. Our main issue is that the system was not designed properly from the ground up, so it takes too long to make fixes and handle requests from our customers. Also, the current technology we are using (Progress database, Progress 4GL for the language) incurs quite a bit of licensing expenses on our customers due to mutli-user license fees for database connections etc. After a lot of discussion it is looking like we will probably start over from scratch (while maintaining the current product at least for the time being). We are looking for a couple of things: Create the system with a nice GUI front end (it is currently CHUI and the application was not built in a way that allows us to redesign the front end... no layering or separation of business logic and gui...shudder). Create the system with the ability to modularize different functionality so the product doesn't have to include all features. This would keep the cost down for our current customers that want basic functionality and a lower price tag. The bells and whistles would be available for those that would want them. Use proper design patterns to make the product easy to add or change any part at any time (i.e. change the database or change the front end without needing to rewrite the application or most of it). This is a problem today because the Progress 4GL code is directly compiled against the database. Small changes in the database requires lots of code recompiling. Our new system will be Linux based, with a possibility of a client application providing functionality from one or more windows boxes. So what I'm looking for is any suggestions on which database and/or framework or programming language(s) someone might recommend for this sort of product. Anyone that has experience in this field might be able to point us in the right direction or even have some ideas of what to avoid. We have considered .NET and SQL Express (we don't need an enterprise level DB), but that would limit us to windows (as far as I know anyway). I have heard of Mono for writing .NET code in a Linux environment, but I don't know much about it yet. We've also considered a Java and MySql based implementation. To summarize we are looking to do the following: Keep licensing costs down on the technology we will use to develop the product (Oracle, yikes! MySQL, nice.) Deliver a solution that is easily maintainable and supportable. A solution that has a component capable of running on "old" hardware through a CHUI front end. (some of our customers have 40+ terminals which would be a ton of cash in order to convert over to a PC). Suggestions would be appreciated. Thanks [UPDATE] I should note that we are currently performing a total cost analysis. This question is intended to give us a couple of "educated" options to look into to include in or analysis. Anyone who could share experiences/suggestions about client/server setups would be appreciated (not just those who have experience with point of sale systems... that would just be a bonus).

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• Linux fsck.ext3 says "Device or resource busy" although I did not mount the disk.

  - by matnagel

  I am running an ubuntu 8.04 server instance with a 8GB virtual disk on vmware 1.0.9. For disk maintenance I made a copy of the virtual disk (by making a copy of the 2 vmdk files of sda on the stopped vm on the host) and added it to the original vm. Now this vm has it's original virtual disk sda plus a 1:1 copy (sdd). There are 2 additional disk sdb and sdc which I ignore.) I would expect sdb not to be mounted when I start the vm. So I try tp do a ext2 fsck on sdd from the running vm, but it reports fsck reported that sdb was mounted. $ sudo fsck.ext3 -b 8193 /dev/sdd e2fsck 1.40.8 (13-Mar-2008) fsck.ext3: Device or resource busy while trying to open /dev/sdd Filesystem mounted or opened exclusively by another program? The "mount" command does not tell me sdd is mounted: $ sudo mount /dev/sda1 on / type ext3 (rw,relatime,errors=remount-ro) proc on /proc type proc (rw,noexec,nosuid,nodev) /sys on /sys type sysfs (rw,noexec,nosuid,nodev) varrun on /var/run type tmpfs (rw,noexec,nosuid,nodev,mode=0755) varlock on /var/lock type tmpfs (rw,noexec,nosuid,nodev,mode=1777) udev on /dev type tmpfs (rw,mode=0755) devshm on /dev/shm type tmpfs (rw) devpts on /dev/pts type devpts (rw,gid=5,mode=620) /dev/sdc1 on /mnt/r1 type ext3 (rw,relatime,errors=remount-ro) /dev/sdb1 on /mnt/k1 type ext3 (rw,relatime,errors=remount-ro) securityfs on /sys/kernel/security type securityfs (rw) When I ignore the warning and continue the fsck, it reported many errors. How do I get this under control? Is there a better way to figure out if sdd is mounted? Or how is it "busy? How to unmount it then? How to prevent ubuntu from automatically mounting. Or is there something else I am missing? Also from /var/log/syslog I cannot see it is mounted, this is the last part of the startup sequence: kernel: [ 14.229494] ACPI: Power Button (FF) [PWRF] kernel: [ 14.230326] ACPI: AC Adapter [ACAD] (on-line) kernel: [ 14.460136] input: PC Speaker as /devices/platform/pcspkr/input/input3 kernel: [ 14.639366] udev: renamed network interface eth0 to eth1 kernel: [ 14.670187] eth1: link up kernel: [ 16.329607] input: ImPS/2 Generic Wheel Mouse as /devices/platform/i8042/serio1/ kernel: [ 16.367540] parport_pc 00:08: reported by Plug and Play ACPI kernel: [ 16.367670] parport0: PC-style at 0x378, irq 7 [PCSPP,TRISTATE] kernel: [ 19.425637] NET: Registered protocol family 10 kernel: [ 19.437550] lo: Disabled Privacy Extensions kernel: [ 24.328857] loop: module loaded kernel: [ 24.449293] lp0: using parport0 (interrupt-driven). kernel: [ 26.075499] EXT3 FS on sda1, internal journal kernel: [ 28.380299] kjournald starting. Commit interval 5 seconds kernel: [ 28.381706] EXT3 FS on sdc1, internal journal kernel: [ 28.381747] EXT3-fs: mounted filesystem with ordered data mode. kernel: [ 28.444867] kjournald starting. Commit interval 5 seconds kernel: [ 28.445436] EXT3 FS on sdb1, internal journal kernel: [ 28.445444] EXT3-fs: mounted filesystem with ordered data mode. kernel: [ 31.309766] eth1: no IPv6 routers present kernel: [ 35.054268] ip_tables: (C) 2000-2006 Netfilter Core Team mysqld_safe[4367]: started mysqld[4370]: 100124 14:40:21 InnoDB: Started; log sequence number 0 10130914 mysqld[4370]: 100124 14:40:21 [Note] /usr/sbin/mysqld: ready for connections. mysqld[4370]: Version: '5.0.51a-3ubuntu5.4' socket: '/var/run/mysqld/mysqld.sock' port: 3 /etc/mysql/debian-start[4417]: Upgrading MySQL tables if necessary. /etc/mysql/debian-start[4422]: Looking for 'mysql' in: /usr/bin/mysql /etc/mysql/debian-start[4422]: Looking for 'mysqlcheck' in: /usr/bin/mysqlcheck /etc/mysql/debian-start[4422]: This installation of MySQL is already upgraded to 5.0.51a, u /etc/mysql/debian-start[4436]: Checking for insecure root accounts. /etc/mysql/debian-start[4444]: Checking for crashed MySQL tables.

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• Understanding floating point problems

  - by Maxim Gershkovich

  Could someone here please help me understand how to determine when floating point limitations will cause errors in your calculations. For example the following code. CalculateTotalTax = function (TaxRate, TaxFreePrice) { return ((parseFloat(TaxFreePrice) / 100) * parseFloat(TaxRate)).toFixed(4); }; I have been unable to input any two values that have caused for me an incorrect result for this method. If I remove the toFixed(4) I can infact see where the calculations start to lose accuracy (somewhere around the 6th decimal place). Having said that though, my understanding of floats is that even small numbers can sometimes fail to be represented or have I misunderstood and can 4 decimal places (for example) always be represented accurately. MSDN explains floats as such... This means they cannot hold an exact representation of any quantity that is not a binary fraction (of the form k / (2 ^ n) where k and n are integers) Now I assume this applies to all floats (inlcuding those used in javascript). Fundamentally my question boils down to this. How can one determine if any specific method will be vulnerable to errors in floating point operations, at what precision will those errors materialize and what inputs will be required to produce those errors? Hopefully what I am asking makes sense.

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• Nicely representing a floating-point number in python

  - by dln385

  I want to represent a floating-point number as a string rounded to some number of significant digits, and never using the exponential format. Essentially, I want to display any floating-point number and make sure it “looks nice”. There are several parts to this problem: I need to be able to specify the number of significant digits. The number of significant digits needs to be variable, which can't be done with with the string formatting operator. I need it to be rounded the way a person would expect, not something like 1.999999999999 I've figured out one way of doing this, though it looks like a work-round and it's not quite perfect. (The maximum precision is 15 significant digits.) >>> def f(number, sigfig): return ("%.15f" % (round(number, int(-1 * floor(log10(number)) + (sigfig - 1))))).rstrip("0").rstrip(".") >>> print f(0.1, 1) 0.1 >>> print f(0.0000000000368568, 2) 0.000000000037 >>> print f(756867, 3) 757000 Is there a better way to do this? Why doesn't Python have a built-in function for this?

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• Convert pre-IEEE-574 C++ floating-point numbers to/from C#

  - by Richard Kucia

  Before .Net, before math coprocessors, before IEEE-574, Microsoft defined a bit pattern for floating-point numbers. Old versions of the C++ compiler happily used that definition. I am writing a C# app that needs to read/write such floating-point numbers in a file. How can I do the conversions between the 2 bit formats? I need conversion methods in both directions. This app is going to run in a PocketPC/WinCE environment. Changing the structure of the file is out-of-scope for this project. Is there a C++ compiler option that instructs it to use the old FP format? That would be ideal. I could then exchange data between the C# code and C++ code by using a null-terminated text string, and the C++ methods would be simple wrappers around sprintf and atof functions. At the very least, I'm hoping someone can reply with the bit definitions for the old FP format, so I can put together a low-level bit manipulation algorithm if necessary. Thanks.

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• How to efficiently compare the sign of two floating-point values while handling negative zeros

  - by François Beaune

  Given two floating-point numbers, I'm looking for an efficient way to check if they have the same sign, given that if any of the two values is zero (+0.0 or -0.0), they should be considered to have the same sign. For instance, SameSign(1.0, 2.0) should return true SameSign(-1.0, -2.0) should return true SameSign(-1.0, 2.0) should return false SameSign(0.0, 1.0) should return true SameSign(0.0, -1.0) should return true SameSign(-0.0, 1.0) should return true SameSign(-0.0, -1.0) should return true A naive but correct implementation of SameSign in C++ would be: bool SameSign(float a, float b) { if (fabs(a) == 0.0f || fabs(b) == 0.0f) return true; return (a >= 0.0f) == (b >= 0.0f); } Assuming the IEEE floating-point model, here's a variant of SameSign that compiles to branchless code (at least with with Visual C++ 2008): bool SameSign(float a, float b) { int ia = binary_cast<int>(a); int ib = binary_cast<int>(b); int az = (ia & 0x7FFFFFFF) == 0; int bz = (ib & 0x7FFFFFFF) == 0; int ab = (ia ^ ib) >= 0; return (az | bz | ab) != 0; } with binary_cast defined as follow: template <typename Target, typename Source> inline Target binary_cast(Source s) { union { Source m_source; Target m_target; } u; u.m_source = s; return u.m_target; } I'm looking for two things: A faster, more efficient implementation of SameSign, using bit tricks, FPU tricks or even SSE intrinsics. An efficient extension of SameSign to three values.

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• Is it possible to change the mount point used for external USB devices from /media to something else under GNOME?

  - by slm

  I'm using CentOS 5.x and am trying to change the mount point that get's used when I insert a USB thumb drive or external USB drive. They're showing up under /media/KINGSTON for example. I'd like to change this so that they show up under /external/KINGSTON for example. If you must know my reasons for asking this, I have a domain where they're already using /media for something else and it would be more work to move this domain's automount from /media to something else. I'm trying to explore all my options before I decide on a path forward. Thanks!

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