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• Dlink DWA-556 Access point fails to start on 2.6.35-25 while 2.6.35-24 works. How can I do this with >2.6.35-24?

  - by Azendale

  I'm using hostapd to run an access point with a Dlink DWA-556 wireless N card. However, I can no longer get it to start when I use kernels greater than 2.6.35-24. Here's a log where I ran the uname -a&&hostapd -c <configfile> on the different kernel versions. Linux erikbandersen 2.6.35-24-generic #42-Ubuntu SMP Thu Dec 2 02:41:37 UTC 2010 x86_64 GNU/Linux Configuration file: hostapd.conf ctrl_interface_group=0 Opening raw packet socket for ifindex 248 BSS count 1, BSSID mask ff:ff:ff:ff:ff:ff (0 bits) SIOCGIWRANGE: WE(compiled)=22 WE(source)=21 enc_capa=0xf nl80211: Added 802.11b mode based on 802.11g information HT40: control channel: 2 secondary channel: 6 RATE[0] rate=10 flags=0x2 RATE[1] rate=20 flags=0x6 RATE[2] rate=55 flags=0x6 RATE[3] rate=110 flags=0x6 RATE[4] rate=60 flags=0x0 RATE[5] rate=90 flags=0x0 RATE[6] rate=120 flags=0x0 RATE[7] rate=180 flags=0x0 RATE[8] rate=240 flags=0x0 RATE[9] rate=360 flags=0x0 RATE[10] rate=480 flags=0x0 RATE[11] rate=540 flags=0x0 Passive scanning not supported Mode: IEEE 802.11g Channel: 2 Frequency: 2417 MHz Flushing old station entries Deauthenticate all stations Using interface wlan1 with hwaddr 1c:bd:b9:d5:e8:3c and ssid 'erikbandersen.com/freewifi' wlan1: Setup of interface done. MGMT (TX callback) ACK Malformed netlink message: len=436 left=256 plen=420 256 extra bytes in the end of netlink message MGMT (TX callback) ACK mgmt::proberesp cb MGMT (TX callback) ACK mgmt::proberesp cb MGMT (TX callback) ACK mgmt::proberesp cb mgmt::auth authentication: STA=3c:4a:92:0e:41:2f auth_alg=0 auth_transaction=1 status_code=0 wep=0 New STA wlan1: STA 3c:4a:92:0e:41:2f IEEE 802.11: authentication OK (open system) wlan1: STA 3c:4a:92:0e:41:2f MLME: MLME-AUTHENTICATE.indication(3c:4a:92:0e:41:2f, OPEN_SYSTEM) wlan1: STA 3c:4a:92:0e:41:2f MLME: MLME-DELETEKEYS.request(3c:4a:92:0e:41:2f) authentication reply: STA=3c:4a:92:0e:41:2f auth_alg=0 auth_transaction=2 resp=0 (IE len=0) MGMT (TX callback) ACK mgmt::auth cb wlan1: STA 3c:4a:92:0e:41:2f IEEE 802.11: authenticated mgmt::assoc_req association request: STA=3c:4a:92:0e:41:2f capab_info=0x421 listen_interval=10 Validating WMM IE: OUI 00:50:f2 OUI type 2 OUI sub-type 0 version 1 QoS info 0x0 HT: STA 3c:4a:92:0e:41:2f HT Capabilities Info: 0x102c handle_assoc STA 3c:4a:92:0e:41:2f - no greenfield, num of non-gf stations 1 handle_assoc STA 3c:4a:92:0e:41:2f - 20 MHz HT, num of 20MHz HT STAs 1 hostapd_ht_operation_update current operation mode=0x0 hostapd_ht_operation_update new operation mode=0x7 changes=2 new AID 1 wlan1: STA 3c:4a:92:0e:41:2f IEEE 802.11: association OK (aid 1) MGMT (TX callback) ACK mgmt::assoc_resp cb wlan1: STA 3c:4a:92:0e:41:2f IEEE 802.11: associated (aid 1) wlan1: STA 3c:4a:92:0e:41:2f MLME: MLME-ASSOCIATE.indication(3c:4a:92:0e:41:2f) wlan1: STA 3c:4a:92:0e:41:2f MLME: MLME-DELETEKEYS.request(3c:4a:92:0e:41:2f) wlan1: STA 3c:4a:92:0e:41:2f RADIUS: starting accounting session 4DAC8224-00000000 MGMT (TX callback) ACK mgmt::action cb MGMT (TX callback) ACK mgmt::proberesp cb MGMT (TX callback) ACK mgmt::proberesp cb MGMT (TX callback) ACK mgmt::proberesp cb MGMT (TX callback) ACK mgmt::proberesp cb MGMT (TX callback) ACK mgmt::proberesp cb Signal 2 received - terminating wlan1: STA 3c:4a:92:0e:41:2f MLME: MLME-DEAUTHENTICATE.indication(3c:4a:92:0e:41:2f, 1) wlan1: STA 3c:4a:92:0e:41:2f MLME: MLME-DELETEKEYS.request(3c:4a:92:0e:41:2f) Removing station 3c:4a:92:0e:41:2f hostapd_ht_operation_update current operation mode=0x7 hostapd_ht_operation_update new operation mode=0x0 changes=2 Flushing old station entries Deauthenticate all stations . Linux erikbandersen 2.6.35-25-generic #44-Ubuntu SMP Fri Jan 21 17:40:44 UTC 2011 x86_64 GNU/Linux Configuration file: hostapd.conf ctrl_interface_group=0 Opening raw packet socket for ifindex 248 BSS count 1, BSSID mask ff:ff:ff:ff:ff:ff (0 bits) SIOCGIWRANGE: WE(compiled)=22 WE(source)=21 enc_capa=0xf nl80211: Added 802.11b mode based on 802.11g information Allowed channel: mode=1 chan=1 freq=2412 MHz max_tx_power=27 dBm Allowed channel: mode=1 chan=2 freq=2417 MHz max_tx_power=27 dBm Allowed channel: mode=1 chan=3 freq=2422 MHz max_tx_power=27 dBm Allowed channel: mode=1 chan=4 freq=2427 MHz max_tx_power=27 dBm Allowed channel: mode=1 chan=5 freq=2432 MHz max_tx_power=27 dBm Allowed channel: mode=1 chan=6 freq=2437 MHz max_tx_power=27 dBm Allowed channel: mode=1 chan=7 freq=2442 MHz max_tx_power=27 dBm Allowed channel: mode=1 chan=8 freq=2447 MHz max_tx_power=27 dBm Allowed channel: mode=1 chan=9 freq=2452 MHz max_tx_power=27 dBm Allowed channel: mode=1 chan=10 freq=2457 MHz max_tx_power=27 dBm Allowed channel: mode=1 chan=11 freq=2462 MHz max_tx_power=27 dBm Allowed channel: mode=0 chan=1 freq=2412 MHz max_tx_power=27 dBm Allowed channel: mode=0 chan=2 freq=2417 MHz max_tx_power=27 dBm Allowed channel: mode=0 chan=3 freq=2422 MHz max_tx_power=27 dBm Allowed channel: mode=0 chan=4 freq=2427 MHz max_tx_power=27 dBm Allowed channel: mode=0 chan=5 freq=2432 MHz max_tx_power=27 dBm Allowed channel: mode=0 chan=6 freq=2437 MHz max_tx_power=27 dBm Allowed channel: mode=0 chan=7 freq=2442 MHz max_tx_power=27 dBm Allowed channel: mode=0 chan=8 freq=2447 MHz max_tx_power=27 dBm Allowed channel: mode=0 chan=9 freq=2452 MHz max_tx_power=27 dBm Allowed channel: mode=0 chan=10 freq=2457 MHz max_tx_power=27 dBm Allowed channel: mode=0 chan=11 freq=2462 MHz max_tx_power=27 dBm HT40: control channel: 2 secondary channel: 6 RATE[0] rate=10 flags=0x2 RATE[1] rate=20 flags=0x6 RATE[2] rate=55 flags=0x6 RATE[3] rate=110 flags=0x6 RATE[4] rate=60 flags=0x0 RATE[5] rate=90 flags=0x0 RATE[6] rate=120 flags=0x0 RATE[7] rate=180 flags=0x0 RATE[8] rate=240 flags=0x0 RATE[9] rate=360 flags=0x0 RATE[10] rate=480 flags=0x0 RATE[11] rate=540 flags=0x0 Passive scanning not supported Mode: IEEE 802.11g Channel: 2 Frequency: 2417 MHz Could not set channel for kernel driver wlan1: Unable to setup interface. My wireless card is listed as 02:00.0 Network controller: Atheros Communications Inc. AR5008 Wireless Network Adapter (rev 01) by lspci. Am I doing it wrong and there's a new way of doing it? I'm holding off upgrading to Natty because of this. What changed between the versions that would cause this? Should I report it as a bug?

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• straight to grub prompt on boot

  - by cheshirekow

  I am very lost. I did a fresh install of Ubuntu 10.04 on a laptop. First reboot was fine. I ran all the recommended upgrades, and now every time I start I get just a grub>_ prompt. No error message, just the prompt, and a little banner at the top saying grub's version and telling me that I have minimal bash style editing. I've tried: 1) Re-installing grub via sudo grub-install sda (There is only one disk with only two partitions, one primary, and one for swap) 2) Changed GRUB_HIDDEN_TIMEOUT=10 GRUB_TIMEOUT=30 GRUB_CMDLINE_LINUX_DEFAULT="rootdelay=90" GRUB_CMDLINE_LINUX="rootdelay=90" in /etc/default/grub. No luck. I can boot with the following: grub> set root=(hd0,1) grub> probe (hd0,1) -u c00fadde-f7e8-45e7-a4da-0235605f756 grub> linux /boot/vmlinuz-2.6.32-21-generic root=UUID=c00fadde-f7e8-45e7-a4da-0235605f756 rootdelay=90 grub> initrd /boot/initrd.img-2.6.32-21-generic grub> boot And then everything seems to be fine from there. From the grub prompt if I try configfile /boot/grub/grub.cfg The screen clears and I get another grub prompt. So, seriously, what could the problem be? edit: Full text of /boot/grub/grub.cfg # # DO NOT EDIT THIS FILE # # It is automatically generated by /usr/sbin/grub-mkconfig using templates # from /etc/grub.d and settings from /etc/default/grub # ### BEGIN /etc/grub.d/00_header ### if [ -s $prefix/grubenv ]; then load_env fi set default="0" if [ ${prev_saved_entry} ]; then set saved_entry=${prev_saved_entry} save_env saved_entry set prev_saved_entry= save_env prev_saved_entry set boot_once=true fi function savedefault { if [ -z ${boot_once} ]; then saved_entry=${chosen} save_env saved_entry fi } function recordfail { set recordfail=1 if [ -n ${have_grubenv} ]; then if [ -z ${boot_once} ]; then save_env recordfail; fi; fi } insmod ext2 set root='(hd0,1)' search --no-floppy --fs-uuid --set c00fadde-f7e8-45e7-a4da-0235c605f756 if loadfont /usr/share/grub/unicode.pf2 ; then set gfxmode=640x480 insmod gfxterm insmod vbe if terminal_output gfxterm ; then true ; else # For backward compatibility with versions of terminal.mod that don't # understand terminal_output terminal gfxterm fi fi insmod ext2 set root='(hd0,1)' search --no-floppy --fs-uuid --set c00fadde-f7e8-45e7-a4da-0235c605f756 set locale_dir=($root)/boot/grub/locale set lang=en insmod gettext if [ ${recordfail} = 1 ]; then set timeout=-1 else set timeout=30 fi ### END /etc/grub.d/00_header ### ### BEGIN /etc/grub.d/05_debian_theme ### set menu_color_normal=white/black set menu_color_highlight=black/light-gray ### END /etc/grub.d/05_debian_theme ### ### BEGIN /etc/grub.d/10_linux ### menuentry 'Ubuntu, with Linux 2.6.32-21-generic' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod ext2 set root='(hd0,1)' search --no-floppy --fs-uuid --set c00fadde-f7e8-45e7-a4da-0235c605f756 linux /boot/vmlinuz-2.6.32-21-generic root=UUID=c00fadde-f7e8-45e7-a4da-0235c605f756 ro rootdelay=90 rootdelay=90 initrd /boot/initrd.img-2.6.32-21-generic } menuentry 'Ubuntu, with Linux 2.6.32-21-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod ext2 set root='(hd0,1)' search --no-floppy --fs-uuid --set c00fadde-f7e8-45e7-a4da-0235c605f756 echo 'Loading Linux 2.6.32-21-generic ...' linux /boot/vmlinuz-2.6.32-21-generic root=UUID=c00fadde-f7e8-45e7-a4da-0235c605f756 ro single rootdelay=90 echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-2.6.32-21-generic } ### END /etc/grub.d/10_linux ### ### BEGIN /etc/grub.d/20_memtest86+ ### menuentry "Memory test (memtest86+)" { insmod ext2 set root='(hd0,1)' search --no-floppy --fs-uuid --set c00fadde-f7e8-45e7-a4da-0235c605f756 linux16 /boot/memtest86+.bin } menuentry "Memory test (memtest86+, serial console 115200)" { insmod ext2 set root='(hd0,1)' search --no-floppy --fs-uuid --set c00fadde-f7e8-45e7-a4da-0235c605f756 linux16 /boot/memtest86+.bin console=ttyS0,115200n8 } ### END /etc/grub.d/20_memtest86+ ### ### BEGIN /etc/grub.d/30_os-prober ### if [ ${timeout} != -1 ]; then if sleep --verbose --interruptible 10 ; then set timeout=0 fi fi ### END /etc/grub.d/30_os-prober ### ### BEGIN /etc/grub.d/40_custom ### # This file provides an easy way to add custom menu entries. Simply type the # menu entries you want to add after this comment. Be careful not to change # the 'exec tail' line above. ### END /etc/grub.d/40_custom ### output of update-grub Generating grub.cfg ... Found linux image: /boot/vmlinuz-2.6.32-21-generic Found initrd image: /boot/initrd.img-2.6.32-21-generic Found memtest86+ image: /boot/memtest86+.bin done contents of /boot total 14280 -rw-r--r-- 1 root root 640617 2010-04-16 09:01 abi-2.6.32-21-generic -rw-r--r-- 1 root root 115847 2010-04-16 09:01 config-2.6.32-21-generic drwxr-xr-x 3 root root 4096 2010-09-08 02:42 grub -rw-r--r-- 1 root root 7968754 2010-09-02 01:49 initrd.img-2.6.32-21-generic -rw-r--r-- 1 root root 160280 2010-03-23 05:37 memtest86+.bin -rw-r--r-- 1 root root 1687378 2010-04-16 09:01 System.map-2.6.32-21-generic -rw-r--r-- 1 root root 1196 2010-04-16 09:03 vmcoreinfo-2.6.32-21-generic -rw-r--r-- 1 root root 4029792 2010-04-16 09:01 vmlinuz-2.6.32-21-generic

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• Do I need to sanitize the callback parameter from a JSONP call?

  - by christian studer

  I would like to offer a webservice via JSONP and was wondering, if I need to sanitize the value from the callback parameter. My current server side script looks like this currently (More or less. Code is in PHP, but could be anything really.): header("Content-type: application/javascript"); echo $_GET['callback'] . '(' . json_encode($data) . ')'; This is a classic XSS-vulnerability. If I need to sanitize it, then how? I was unable to find enough information about what might be allowed callback strings.

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• Are `return` and `break` useless inside a Ruby block when used as a callback?

  - by Skilldrick

  In Rails, blocks can be used as callbacks, e.g.: class User < ActiveRecord::Base validates_presence_of :login, :email before_create {|user| user.name = user.login.capitalize if user.name.blank?} end When a block is used like this, is there any use for break and return? I'm asking because normally in a block, break will break out of the loop, and return will return from the enclosing method. But in a callback context, I can't get my head round what that means. The Ruby Programming Language suggests that return could cause a LocalJumpError but I haven't been able to reproduce this in a Rails callback. Edit: with the following code I'd expect a LocalJumpError, but all the return does is stop the rest of the callback executing. class User < ActiveRecord::Base validates_presence_of :login, :email before_create do |user| return user.name = user.login.capitalize end

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• On installing nvidia drivers on 12.10 I get "Bad return status for module build on kernel: 3.5.0-19-generic (x86_64)"

  - by james

  New Ubuntu user - just recently made the mistake of trying a different nvidia driver. I'd managed to get the last (nvidia-current) one working through software sources a few weeks ago. The other day I tried to cross over to nvidia-experimental-310 and this produced a system error. Swapping back and forth between proprietary drivers now always causes an error and I can't get any of them to work. Installing through the terminal I get this error message every time: Building initial module for 3.5.0-19-generic Error! Bad return status for module build on kernel: 3.5.0-19-generic (x86_64) Consult /var/lib/dkms/nvidia-experimental-310/310.14/build/make.log for more information On rebooting, I end up with the crappy screen resolution and the thick black border around the screen. I use gksudo software-properties-gtk to bring up sources, where I can change back to the nouveau driver, which restores my screen. After that I can't find /var/lib/dkms/nvidia-experimental-310/310.14/build/make.log so I can't tell you what's inside. Any ideas what might be preventing the nvidia driver from installing? SOLUTION FOUND Okay - so I have a workaround. This is what has worked: Upgrade to kernel 3.7.0 as detailed here upgrade to latest version of the nvidia drivers as detailed here No idea what was happening with kernel 3.5.0-19, but this seems to be better. A little slower maybe on boot, but after days of messing around it's nice to have something that works.

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• 64-bit 13.10 shows 1GB less RAM than 64-bit 13.04 did

  - by kiloseven

  Multiple 64-bit versions (Kubuntu, Lubuntu and Xubuntu) once installed on my ThinkPad R60 show 3GB of RAM, not the correct 4GB of RAM. Last week with 13.04, I had 4GB of RAM (which matches the BIOS) and this week I have 3GB available. Inquiring minds want to know. Details follow: Linux R60 3.11.0-12-generic #19-Ubuntu SMP Wed Oct 9 16:20:46 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux r60 free -m reports: _ total used free shared buffers cached Mem: 3001 854 2146 0 22 486 -/+ buffers/cache: 346 2655 Swap: 0 0 0 . . . . . . lshw shows: description: Notebook product: 9459AT8 () vendor: LENOVO version: ThinkPad R60/R60i serial: redacted width: 64 bits capabilities: smbios-2.4 dmi-2.4 vsyscall32 configuration: administrator_password=disabled boot=normal chassis=notebook family=ThinkPad R60/R60i frontpanel_password=unknown keyboard_password=disabled power-on_password=disabled uuid=126E4001-48CA-11CB-9D53-B982AE0D1ABB *-core description: Motherboard product: 9459AT8 vendor: LENOVO physical id: 0 version: Not Available *-firmware description: BIOS vendor: LENOVO physical id: 0 version: 7CETC1WW (2.11 ) date: 01/09/2007 size: 144KiB capacity: 1984KiB capabilities: pci pcmcia pnp upgrade shadowing escd cdboot bootselect socketedrom edd acpi usb biosbootspecification {snip} *-memory description: System Memory physical id: 29 slot: System board or motherboard size: 4GiB *-bank:0 description: SODIMM DDR2 Synchronous physical id: 0 slot: DIMM 1 size: 2GiB width: 64 bits *-bank:1 description: SODIMM DDR2 Synchronous physical id: 1 slot: DIMM 2 size: 2GiB width: 64 bits dpkg -l linux-* returns: Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad) ||/ Name Version Description +++-======================================-=======================================-========================================================================== un linux-doc-3.2.0 (no description available) ii linux-firmware 1.79.6 Firmware for Linux kernel drivers ii linux-generic 3.2.0.52.62 Complete Generic Linux kernel un linux-headers (no description available) un linux-headers-3 (no description available) un linux-headers-3.0 (no description available) un linux-headers-3.2.0-23 (no description available) un linux-headers-3.2.0-23-generic (no description available) ii linux-headers-3.2.0-52 3.2.0-52.78 Header files related to Linux kernel version 3.2.0 ii linux-headers-3.2.0-52-generic 3.2.0-52.78 Linux kernel headers for version 3.2.0 on 64 bit x86 SMP ii linux-headers-generic 3.2.0.52.62 Generic Linux kernel headers un linux-image (no description available) un linux-image-3.0 (no description available) ii linux-image-3.2.0-52-generic 3.2.0-52.78 Linux kernel image for version 3.2.0 on 64 bit x86 SMP ii linux-image-generic 3.2.0.52.62 Generic Linux kernel image un linux-initramfs-tool (no description available) un linux-kernel-headers (no description available) un linux-kernel-log-daemon (no description available) ii linux-libc-dev 3.2.0-52.78 Linux Kernel Headers for development un linux-restricted-common (no description available) ii linux-sound-base 1.0.25+dfsg-0ubuntu1.1 base package for ALSA and OSS sound systems un linux-source-3.2.0 (no description available) un linux-tools (no description available)

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• Broken package after update: linux-headers, error brokencount >0

  - by escozul

  Ubuntu 12.04. After an update, I get a red warning icon in the system tray, warning about an error: broken count 0 Opening Update manager, I see that the broken package is linux-headers-3.2.0-33-generic-pae (new install) Specificaly I have my ubuntu on an AspireOne with 8gb internal storage. I tried apt-get clean as suggested in another question on this site, and tried reinstalling the package in Synaptic. I have tried to reboot but to no avail. I have also tried apt-get install --fix-broken and I get the following: sudo apt-get install --fix-broken [sudo] password for elina: Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... Done The following extra packages will be installed: linux-headers-3.2.0-33-generic-pae The following NEW packages will be installed: linux-headers-3.2.0-33-generic-pae 0 upgraded, 1 newly installed, 0 to remove and 38 not upgraded. 1 not fully installed or removed. Need to get 0 B/977 kB of archives. After this operation 11,3 MB of additional disk space will be used. Do you want to continue [Y/n]; y (Reading database ... 437051 files and directories currently installed.) Unpacking linux-headers-3.2.0-33-generic-pae (from .../linux-headers-3.2.0-33-generic-pae_3.2.0-33.52_i386.deb) ... dpkg: error processing /var/cache/apt/archives/linux-headers-3.2.0-33-generic-pae_3.2.0-33.52_i386.deb (--unpack): unable to create `/usr/src/linux-headers-3.2.0-33-generic-pae/include/config/usb/gspca/sonixb.h.dpkg-new' (while processing `./usr/src/linux-headers-3.2.0-33-generic-pae/include/config/usb/gspca/sonixb.h'): No space left on device No apport report written because the error message indicates a disk full error dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Errors were encountered while processing: /var/cache/apt/archives/linux-headers-3.2.0-33-generic-pae_3.2.0-33.52_i386.deb E: Sub-process /usr/bin/dpkg returned an error code (1) I've tried all suggestions I could find: sudo apt-get clean sudo apt-get autoclean sudo apt-get autoremove sudo apt-get update sudo apt-get upgrade sudo apt-get -f install sudo apt-get install --fix-broken Then I saw that on the error there was a mention about free space. So I did a df -h and the result was: Filesystem Size Used Avail Use% Mounted on /dev/sda1 7,0G 5,5G 1,1G 84% / udev 235M 4,0K 235M 1% /dev tmpfs 97M 816K 96M 1% /run none 5,0M 0 5,0M 0% /run/lock none 242M 352K 242M 1% /run/shm I see that on my root folder I have 1.1Gb free. The broken package is linux-headers-3.2.0-33-generic-pae_3.2.0-33.52_i386.deb which only takes up 11.3Mb on my hard drive. I'm soooo lost. I really hope there is something I'm missing here. I don't want to go about reformatting this bucket. It's really not worth the time. Any help for fixing this would be hot.

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• Update Errors in Xubuntu 12.10

  - by wil

  I updated by computer from 12.04 to 12.10 and after I finished updating when I turned on my computer I am unable to update my computer. I tried install a new copy of 13.04 but my cpu doesn't support pae. I have a IBM Thinkpad T42 with a 1.7 gigahertx Cpu. When updating through terminal This is the output. sudo apt-get upgrade: [sudo] password for wil: Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-get -f install' to correct these. The following packages have unmet dependencies: linux-image-extra-3.5.0-34-generic : Depends: linux-image-3.5.0-34-generic but it is not installed linux-image-generic : Depends: linux-image-3.5.0-34-generic but it is not installed E: Unmet dependencies. Try using -f. sudo apt-get upgrade -f: Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... Done The following NEW packages will be installed: linux-image-3.5.0-34-generic 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. 3 not fully installed or removed. Need to get 0 B/11.8 MB of archives. After this operation, 25.9 MB of additional disk space will be used. Do you want to continue [Y/n]? y (Reading database ... 191530 files and directories currently installed.) Unpacking linux-image-3.5.0-34-generic (from .../linux-image-3.5.0-34-generic_3.5.0-34.55_i386.deb) ... This kernel does not support a non-PAE CPU. dpkg: error processing /var/cache/apt/archives/linux-image-3.5.0-34-generic_3.5.0-34.55_i386.deb (--unpack): subprocess new pre-installation script returned error exit status 1 No apport report written because MaxReports is reached already Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.5.0-34-generic /boot/vmlinuz-3.5.0-34-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.5.0-34-generic /boot/vmlinuz-3.5.0-34-generic Errors were encountered while processing: /var/cache/apt/archives/linux-image-3.5.0-34-generic_3.5.0-34.55_i386.deb E: Sub-process /usr/bin/dpkg returned an error code (1) wil@wil-ThinkPad-T42:~/Desktop$

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• 12.04 upgrade broke grub? (not wubi related)

  - by kaare

  I just updated from 11.10 to 12.04, with no major problems (it took a while to get past a request to restart ssh, mysql and some other services, but I did no fiddling by myself, everything was done by the installer). However, after restarting, grub can't do anything. Picking the new linux installation (first entry), I just get error: no such partition error: no such partition error: no such partition and picking the recovery-version just gives 5 lines instead of 3. I have windows 7 installed on a different drive, and can run it by booting from that drive instead. Picking it from the grub menu gives the same error as above (can't remember how many lines, though). I'll be honest and say that I don't remember if win 7 could be booted from grub before the update, though. In short, nothing on the grub menu works. any solutions? The grub menu changed appearance - before it was on a purple background, small letters, now it's white-on-black, big letters, looking very basic. The original installation was from a usb-drive, and I hadn't heard about wubi until I started googling this problem, so I doubt there's any connection. I really hope there are some grub-savvy people out there :) EDIT: ok. so, I made a bootable usb, and am running from that right now. when I ran the bootinfoscript, it warned me that "gawk" could not be found, using "busybox awk" instead. This may lead to unreliable results. just so you know. The contents of RESULTS.txt are: Boot Info Script 0.61 [1 April 2012] ============================= Boot Info Summary: =============================== => Windows is installed in the MBR of /dev/sda. => Grub2 (v1.99) is installed in the MBR of /dev/sdb and looks at sector 1 of the same hard drive for core.img. core.img is at this location and looks for (,msdos3)/boot/grub on this drive. => Syslinux MBR (4.04 and higher) is installed in the MBR of /dev/sdc. sda1: __________________________________________ File system: vfat Boot sector type: Dell Utility: FAT16 Boot sector info: No errors found in the Boot Parameter Block. Operating System: Boot files: /DELLBIO.BIN /DELLRMK.BIN /COMMAND.COM sda2: __________________________________________ File system: ntfs Boot sector type: Windows Vista/7: NTFS Boot sector info: No errors found in the Boot Parameter Block. Operating System: Boot files: sda3: __________________________________________ File system: ntfs Boot sector type: Windows Vista/7: NTFS Boot sector info: No errors found in the Boot Parameter Block. Operating System: Windows 7 Boot files: /bootmgr /Boot/BCD /Windows/System32/winload.exe sda4: __________________________________________ File system: Extended Partition Boot sector type: - Boot sector info: sda5: __________________________________________ File system: vfat Boot sector type: Windows 7: FAT32 Boot sector info: No errors found in the Boot Parameter Block. Operating System: Windows XP Boot files: /boot.ini /bootmgr /ntldr /NTDETECT.COM 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: sdb2: __________________________________________ File system: swap Boot sector type: - Boot sector info: sdb3: __________________________________________ File system: ext4 Boot sector type: Grub2 (v1.99) Boot sector info: Grub2 (v1.99) is installed in the boot sector of sdb3 and looks at sector 375893584 of the same hard drive for core.img. core.img is at this location and looks for (,msdos3)/boot/grub on this drive. Operating System: Ubuntu 12.04 LTS Boot files: /boot/grub/grub.cfg /etc/fstab /boot/grub/core.img sdb4: __________________________________________ File system: ext4 Boot sector type: - Boot sector info: Operating System: Boot files: sdc1: __________________________________________ File system: ntfs Boot sector type: SYSLINUX 4.06 4.06-pre1 Boot sector info: Syslinux looks at sector 4649656 of /dev/sdc1 for its second stage. SYSLINUX is installed in the directory. The integrity check of the ADV area failed. No errors found in the Boot Parameter Block. Operating System: Boot files: /boot/grub/grub.cfg /syslinux/syslinux.cfg /ldlinux.sys ============================ Drive/Partition Info: ============================= Drive: sda _______________________________________ Disk /dev/sda: 250.1 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders, total 488397168 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 63 240,974 240,912 de Dell Utility /dev/sda2 241,664 21,213,183 20,971,520 7 NTFS / exFAT / HPFS /dev/sda3 * 21,213,184 483,151,863 461,938,680 7 NTFS / exFAT / HPFS /dev/sda4 483,151,872 488,394,751 5,242,880 f W95 Extended (LBA) /dev/sda5 483,153,920 488,394,751 5,240,832 dd Dell Media Direct Drive: sdb _______________________________________ Disk /dev/sdb: 250.1 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders, total 488397168 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 63 345,886,749 345,886,687 7 NTFS / exFAT / HPFS /dev/sdb2 345,888,768 361,510,911 15,622,144 82 Linux swap / Solaris /dev/sdb3 * 361,510,912 390,807,786 29,296,875 83 Linux /dev/sdb4 390,809,600 488,394,751 97,585,152 83 Linux Drive: sdc _______________________________________ Disk /dev/sdc: 8015 MB, 8015282176 bytes 255 heads, 63 sectors/track, 974 cylinders, total 15654848 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/sdc1 * 2,048 15,652,863 15,650,816 7 NTFS / exFAT / HPFS "blkid" output: ____________________________________ Device UUID TYPE LABEL /dev/loop0 squashfs /dev/sda1 07D8-0411 vfat DellUtility /dev/sda2 E2765BBC765B9061 ntfs RECOVERY /dev/sda3 98DC5E54DC5E2D2E ntfs OS /dev/sda5 7061-9DF5 vfat MEDIADIRECT /dev/sdb1 01CBBB4C3374C3B0 ntfs Data1 /dev/sdb2 1ca45f3f-f888-43d1-8137-02699597189a swap /dev/sdb3 6bc1b599-ad4b-403c-a155-a5bc81211f5e ext4 /dev/sdb4 58e2b257-8608-4b11-b20b-dc162bb80b62 ext4 /dev/sdc1 0C02B64402B63316 ntfs PENDRIVE ================================ Mount points: ================================= Device Mount_Point Type Options /dev/loop0 /rofs squashfs (ro,noatime) /dev/sdb4 /media/58e2b257-8608-4b11-b20b-dc162bb80b62 ext4 (rw,nosuid,nodev,uhelper=udisks) /dev/sdc1 /cdrom fuseblk (rw,nosuid,nodev,relatime,user_id=0,group_id=0,allow_other,blksize=4096) ================================ sda5/boot.ini: ================================ [boot loader] timeout=0 default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS [operating systems] multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Embedded" /fastdetect /KERNEL=NTOSBOOT.EXE /maxmem=1024 =========================== sdb3/boot/grub/grub.cfg: =========================== -------------------------------------------------------------------------------- # # DO NOT EDIT THIS FILE # # It is automatically generated by grub-mkconfig using templates # from /etc/grub.d and settings from /etc/default/grub # ### BEGIN /etc/grub.d/00_header ### if [ -s $prefix/grubenv ]; then set have_grubenv=true load_env fi set default="0" if [ "${prev_saved_entry}" ]; then set saved_entry="${prev_saved_entry}" save_env saved_entry set prev_saved_entry= save_env prev_saved_entry set boot_once=true fi function savedefault { if [ -z "${boot_once}" ]; then saved_entry="${chosen}" save_env saved_entry fi } function recordfail { set recordfail=1 if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi } function load_video { insmod vbe insmod vga insmod video_bochs insmod video_cirrus } insmod part_msdos insmod ext2 set root='(hd1,msdos3)' search --no-floppy --fs-uuid --set=root 6bc1b599-ad4b-403c-a155-a5bc81211f5e if loadfont /usr/share/grub/unicode.pf2 ; then set gfxmode=auto load_video insmod gfxterm insmod part_msdos insmod ext2 set root='(hd1,msdos3)' search --no-floppy --fs-uuid --set=root 6bc1b599-ad4b-403c-a155-a5bc81211f5e set locale_dir=($root)/boot/grub/locale set lang=en_US insmod gettext fi terminal_output gfxterm if [ "${recordfail}" = 1 ]; then set timeout=-1 else set timeout=10 fi ### END /etc/grub.d/00_header ### ### BEGIN /etc/grub.d/05_debian_theme ### set menu_color_normal=white/black set menu_color_highlight=black/light-gray if background_color 44,0,30; then clear fi ### END /etc/grub.d/05_debian_theme ### ### BEGIN /etc/grub.d/10_linux ### function gfxmode { set gfxpayload="$1" if [ "$1" = "keep" ]; then set vt_handoff=vt.handoff=7 else set vt_handoff= fi } if [ ${recordfail} != 1 ]; then if [ -e ${prefix}/gfxblacklist.txt ]; then if hwmatch ${prefix}/gfxblacklist.txt 3; then if [ ${match} = 0 ]; then set linux_gfx_mode=keep else set linux_gfx_mode=text fi else set linux_gfx_mode=text fi else set linux_gfx_mode=keep fi else set linux_gfx_mode=text fi export linux_gfx_mode if [ "$linux_gfx_mode" != "text" ]; then load_video; fi menuentry 'Ubuntu, with Linux 3.2.0-24-generic' --class ubuntu --class gnu-linux --class gnu --class os { recordfail gfxmode $linux_gfx_mode insmod gzio insmod part_msdos insmod ext2 set root='(hd1,msdos3)' search --no-floppy --fs-uuid --set=root 6bc1b599-ad4b-403c-a155-a5bc81211f5e linux /boot/vmlinuz-3.2.0-24-generic root=UUID=6bc1b599-ad4b-403c-a155-a5bc81211f5e ro quiet splash $vt_handoff initrd /boot/initrd.img-3.2.0-24-generic } menuentry 'Ubuntu, with Linux 3.2.0-24-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod gzio insmod part_msdos insmod ext2 set root='(hd1,msdos3)' search --no-floppy --fs-uuid --set=root 6bc1b599-ad4b-403c-a155-a5bc81211f5e echo 'Loading Linux 3.2.0-24-generic ...' linux /boot/vmlinuz-3.2.0-24-generic root=UUID=6bc1b599-ad4b-403c-a155-a5bc81211f5e ro recovery nomodeset echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.2.0-24-generic } submenu "Previous Linux versions" { menuentry 'Ubuntu, with Linux 3.0.0-19-generic' --class ubuntu --class gnu-linux --class gnu --class os { recordfail gfxmode $linux_gfx_mode insmod gzio insmod part_msdos insmod ext2 set root='(hd1,msdos3)' search --no-floppy --fs-uuid --set=root 6bc1b599-ad4b-403c-a155-a5bc81211f5e linux /boot/vmlinuz-3.0.0-19-generic root=UUID=6bc1b599-ad4b-403c-a155-a5bc81211f5e ro quiet splash $vt_handoff initrd /boot/initrd.img-3.0.0-19-generic } menuentry 'Ubuntu, with Linux 3.0.0-19-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod gzio insmod part_msdos insmod ext2 set root='(hd1,msdos3)' search --no-floppy --fs-uuid --set=root 6bc1b599-ad4b-403c-a155-a5bc81211f5e echo 'Loading Linux 3.0.0-19-generic ...' linux /boot/vmlinuz-3.0.0-19-generic root=UUID=6bc1b599-ad4b-403c-a155-a5bc81211f5e ro recovery nomodeset echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.0.0-19-generic } } ### END /etc/grub.d/10_linux ### ### BEGIN /etc/grub.d/20_linux_xen ### ### END /etc/grub.d/20_linux_xen ### ### BEGIN /etc/grub.d/20_memtest86+ ### menuentry "Memory test (memtest86+)" { insmod part_msdos insmod ext2 set root='(hd1,msdos3)' search --no-floppy --fs-uuid --set=root 6bc1b599-ad4b-403c-a155-a5bc81211f5e linux16 /boot/memtest86+.bin } menuentry "Memory test (memtest86+, serial console 115200)" { insmod part_msdos insmod ext2 set root='(hd1,msdos3)' search --no-floppy --fs-uuid --set=root 6bc1b599-ad4b-403c-a155-a5bc81211f5e linux16 /boot/memtest86+.bin console=ttyS0,115200n8 } ### END /etc/grub.d/20_memtest86+ ### ### BEGIN /etc/grub.d/30_os-prober ### menuentry "Windows 7 (loader) (on /dev/sda3)" --class windows --class os { insmod part_msdos insmod ntfs set root='(hd0,msdos3)' search --no-floppy --fs-uuid --set=root 98DC5E54DC5E2D2E chainloader +1 } menuentry "Microsoft Windows XP Embedded (on /dev/sda5)" --class windows --class os { insmod part_msdos insmod fat set root='(hd0,msdos5)' search --no-floppy --fs-uuid --set=root 7061-9DF5 drivemap -s (hd0) ${root} chainloader +1 } ### END /etc/grub.d/30_os-prober ### ### BEGIN /etc/grub.d/40_custom ### # This file provides an easy way to add custom menu entries. Simply type the # menu entries you want to add after this comment. Be careful not to change # the 'exec tail' line above. ### END /etc/grub.d/40_custom ### ### BEGIN /etc/grub.d/41_custom ### if [ -f $prefix/custom.cfg ]; then source $prefix/custom.cfg; fi ### END /etc/grub.d/41_custom ### =============================== sdb3/etc/fstab: ================================ # /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 # / was on /dev/sdb3 during installation UUID=6bc1b599-ad4b-403c-a155-a5bc81211f5e / ext4 errors=remount-ro 0 1 # /home was on /dev/sdb4 during installation UUID=58e2b257-8608-4b11-b20b-dc162bb80b62 /home ext4 defaults,user_xattr 0 2 # swap was on /dev/sdb2 during installation UUID=1ca45f3f-f888-43d1-8137-02699597189a none swap sw 0 0 =================== sdb3: Location of files loaded by Grub: ==================== GiB - GB File Fragment(s) = boot/grub/core.img 1 = boot/grub/grub.cfg 1 = boot/initrd.img-3.0.0-19-generic 2 = boot/initrd.img-3.2.0-24-generic 2 = boot/vmlinuz-3.0.0-19-generic 2 = boot/vmlinuz-3.2.0-24-generic 1 = vmlinuz 1 = vmlinuz.old 2 =========================== sdc1/boot/grub/grub.cfg: =========================== if loadfont /boot/grub/font.pf2 ; then set gfxmode=auto insmod efi_gop insmod efi_uga insmod gfxterm terminal_output gfxterm fi set menu_color_normal=white/black set menu_color_highlight=black/light-gray menuentry "Try Ubuntu without installing" { set gfxpayload=keep linux /casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash -- initrd /casper/initrd.lz } menuentry "Install Ubuntu" { set gfxpayload=keep linux /casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper only-ubiquity quiet splash -- initrd /casper/initrd.lz } menuentry "Check disc for defects" { set gfxpayload=keep linux /casper/vmlinuz boot=casper integrity-check quiet splash -- initrd /casper/initrd.lz } ========================= sdc1/syslinux/syslinux.cfg: ========================== # D-I config version 2.0 include menu.cfg default vesamenu.c32 prompt 0 timeout 50 # If you would like to use the new menu and be presented with the option to install or run from USB at startup, remove # from the following line. This line was commented out (by request of many) to allow the old menu to be presented and to enable booting straight into the Live Environment! # ui gfxboot bootlogo =================== sdc1: Location of files loaded by Grub: ==================== GiB - GB File Fragment(s) ?? = ?? boot/grub/grub.cfg 0 ================= sdc1: Location of files loaded by Syslinux: ================== GiB - GB File Fragment(s) ?? = ?? ldlinux.sys 1 ?? = ?? syslinux/chain.c32 1 ?? = ?? syslinux/gfxboot.c32 1 ?? = ?? syslinux/syslinux.cfg 0 ?? = ?? syslinux/vesamenu.c32 1 ============== sdc1: Version of COM32(R) files used by Syslinux: =============== syslinux/chain.c32 : COM32R module (v4.xx) syslinux/gfxboot.c32 : COM32R module (v4.xx) syslinux/vesamenu.c32 : COM32R module (v4.xx) =============================== StdErr Messages: =============================== xz: (stdin): Compressed data is corrupt xz: (stdin): Compressed data is corrupt awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in awk: cmd. line:36: Math support is not compiled in ./bootinfoscript: line 1646: [: 2.73495e+09: integer expression expected

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• C#/.NET Fundamentals: Choosing the Right Collection Class

  - by James Michael Hare

  The .NET Base Class Library (BCL) has a wide array of collection classes at your disposal which make it easy to manage collections of objects. While it's great to have so many classes available, it can be daunting to choose the right collection to use for any given situation. As hard as it may be, choosing the right collection can be absolutely key to the performance and maintainability of your application! This post will look at breaking down any confusion between each collection and the situations in which they excel. We will be spending most of our time looking at the System.Collections.Generic namespace, which is the recommended set of collections. The Generic Collections: System.Collections.Generic namespace The generic collections were introduced in .NET 2.0 in the System.Collections.Generic namespace. This is the main body of collections you should tend to focus on first, as they will tend to suit 99% of your needs right up front. It is important to note that the generic collections are unsynchronized. This decision was made for performance reasons because depending on how you are using the collections its completely possible that synchronization may not be required or may be needed on a higher level than simple method-level synchronization. Furthermore, concurrent read access (all writes done at beginning and never again) is always safe, but for concurrent mixed access you should either synchronize the collection or use one of the concurrent collections. So let's look at each of the collections in turn and its various pros and cons, at the end we'll summarize with a table to help make it easier to compare and contrast the different collections. The Associative Collection Classes Associative collections store a value in the collection by providing a key that is used to add/remove/lookup the item. Hence, the container associates the value with the key. These collections are most useful when you need to lookup/manipulate a collection using a key value. For example, if you wanted to look up an order in a collection of orders by an order id, you might have an associative collection where they key is the order id and the value is the order. The Dictionary<TKey,TVale> is probably the most used associative container class. The Dictionary<TKey,TValue> is the fastest class for associative lookups/inserts/deletes because it uses a hash table under the covers. Because the keys are hashed, the key type should correctly implement GetHashCode() and Equals() appropriately or you should provide an external IEqualityComparer to the dictionary on construction. The insert/delete/lookup time of items in the dictionary is amortized constant time - O(1) - which means no matter how big the dictionary gets, the time it takes to find something remains relatively constant. This is highly desirable for high-speed lookups. The only downside is that the dictionary, by nature of using a hash table, is unordered, so you cannot easily traverse the items in a Dictionary in order. The SortedDictionary<TKey,TValue> is similar to the Dictionary<TKey,TValue> in usage but very different in implementation. The SortedDictionary<TKey,TValye> uses a binary tree under the covers to maintain the items in order by the key. As a consequence of sorting, the type used for the key must correctly implement IComparable<TKey> so that the keys can be correctly sorted. The sorted dictionary trades a little bit of lookup time for the ability to maintain the items in order, thus insert/delete/lookup times in a sorted dictionary are logarithmic - O(log n). Generally speaking, with logarithmic time, you can double the size of the collection and it only has to perform one extra comparison to find the item. Use the SortedDictionary<TKey,TValue> when you want fast lookups but also want to be able to maintain the collection in order by the key. The SortedList<TKey,TValue> is the other ordered associative container class in the generic containers. Once again SortedList<TKey,TValue>, like SortedDictionary<TKey,TValue>, uses a key to sort key-value pairs. Unlike SortedDictionary, however, items in a SortedList are stored as an ordered array of items. This means that insertions and deletions are linear - O(n) - because deleting or adding an item may involve shifting all items up or down in the list. Lookup time, however is O(log n) because the SortedList can use a binary search to find any item in the list by its key. So why would you ever want to do this? Well, the answer is that if you are going to load the SortedList up-front, the insertions will be slower, but because array indexing is faster than following object links, lookups are marginally faster than a SortedDictionary. Once again I'd use this in situations where you want fast lookups and want to maintain the collection in order by the key, and where insertions and deletions are rare. The Non-Associative Containers The other container classes are non-associative. They don't use keys to manipulate the collection but rely on the object itself being stored or some other means (such as index) to manipulate the collection. The List<T> is a basic contiguous storage container. Some people may call this a vector or dynamic array. Essentially it is an array of items that grow once its current capacity is exceeded. Because the items are stored contiguously as an array, you can access items in the List<T> by index very quickly. However inserting and removing in the beginning or middle of the List<T> are very costly because you must shift all the items up or down as you delete or insert respectively. However, adding and removing at the end of a List<T> is an amortized constant operation - O(1). Typically List<T> is the standard go-to collection when you don't have any other constraints, and typically we favor a List<T> even over arrays unless we are sure the size will remain absolutely fixed. The LinkedList<T> is a basic implementation of a doubly-linked list. This means that you can add or remove items in the middle of a linked list very quickly (because there's no items to move up or down in contiguous memory), but you also lose the ability to index items by position quickly. Most of the time we tend to favor List<T> over LinkedList<T> unless you are doing a lot of adding and removing from the collection, in which case a LinkedList<T> may make more sense. The HashSet<T> is an unordered collection of unique items. This means that the collection cannot have duplicates and no order is maintained. Logically, this is very similar to having a Dictionary<TKey,TValue> where the TKey and TValue both refer to the same object. This collection is very useful for maintaining a collection of items you wish to check membership against. For example, if you receive an order for a given vendor code, you may want to check to make sure the vendor code belongs to the set of vendor codes you handle. In these cases a HashSet<T> is useful for super-quick lookups where order is not important. Once again, like in Dictionary, the type T should have a valid implementation of GetHashCode() and Equals(), or you should provide an appropriate IEqualityComparer<T> to the HashSet<T> on construction. The SortedSet<T> is to HashSet<T> what the SortedDictionary<TKey,TValue> is to Dictionary<TKey,TValue>. That is, the SortedSet<T> is a binary tree where the key and value are the same object. This once again means that adding/removing/lookups are logarithmic - O(log n) - but you gain the ability to iterate over the items in order. For this collection to be effective, type T must implement IComparable<T> or you need to supply an external IComparer<T>. Finally, the Stack<T> and Queue<T> are two very specific collections that allow you to handle a sequential collection of objects in very specific ways. The Stack<T> is a last-in-first-out (LIFO) container where items are added and removed from the top of the stack. Typically this is useful in situations where you want to stack actions and then be able to undo those actions in reverse order as needed. The Queue<T> on the other hand is a first-in-first-out container which adds items at the end of the queue and removes items from the front. This is useful for situations where you need to process items in the order in which they came, such as a print spooler or waiting lines. So that's the basic collections. Let's summarize what we've learned in a quick reference table.  Collection Ordered? Contiguous Storage? Direct Access? Lookup Efficiency Manipulate Efficiency Notes Dictionary No Yes Via Key Key: O(1) O(1) Best for high performance lookups. SortedDictionary Yes No Via Key Key: O(log n) O(log n) Compromise of Dictionary speed and ordering, uses binary search tree. SortedList Yes Yes Via Key Key: O(log n) O(n) Very similar to SortedDictionary, except tree is implemented in an array, so has faster lookup on preloaded data, but slower loads. List No Yes Via Index Index: O(1) Value: O(n) O(n) Best for smaller lists where direct access required and no ordering. LinkedList No No No Value: O(n) O(1) Best for lists where inserting/deleting in middle is common and no direct access required. HashSet No Yes Via Key Key: O(1) O(1) Unique unordered collection, like a Dictionary except key and value are same object. SortedSet Yes No Via Key Key: O(log n) O(log n) Unique ordered collection, like SortedDictionary except key and value are same object. Stack No Yes Only Top Top: O(1) O(1)* Essentially same as List<T> except only process as LIFO Queue No Yes Only Front Front: O(1) O(1) Essentially same as List<T> except only process as FIFO   The Original Collections: System.Collections namespace The original collection classes are largely considered deprecated by developers and by Microsoft itself. In fact they indicate that for the most part you should always favor the generic or concurrent collections, and only use the original collections when you are dealing with legacy .NET code. Because these collections are out of vogue, let's just briefly mention the original collection and their generic equivalents: ArrayList A dynamic, contiguous collection of objects. Favor the generic collection List<T> instead. Hashtable Associative, unordered collection of key-value pairs of objects. Favor the generic collection Dictionary<TKey,TValue> instead. Queue First-in-first-out (FIFO) collection of objects. Favor the generic collection Queue<T> instead. SortedList Associative, ordered collection of key-value pairs of objects. Favor the generic collection SortedList<T> instead. Stack Last-in-first-out (LIFO) collection of objects. Favor the generic collection Stack<T> instead. In general, the older collections are non-type-safe and in some cases less performant than their generic counterparts. Once again, the only reason you should fall back on these older collections is for backward compatibility with legacy code and libraries only. The Concurrent Collections: System.Collections.Concurrent namespace The concurrent collections are new as of .NET 4.0 and are included in the System.Collections.Concurrent namespace. These collections are optimized for use in situations where multi-threaded read and write access of a collection is desired. The concurrent queue, stack, and dictionary work much as you'd expect. The bag and blocking collection are more unique. Below is the summary of each with a link to a blog post I did on each of them. ConcurrentQueue Thread-safe version of a queue (FIFO). For more information see: C#/.NET Little Wonders: The ConcurrentStack and ConcurrentQueue ConcurrentStack Thread-safe version of a stack (LIFO). For more information see: C#/.NET Little Wonders: The ConcurrentStack and ConcurrentQueue ConcurrentBag Thread-safe unordered collection of objects. Optimized for situations where a thread may be bother reader and writer. For more information see: C#/.NET Little Wonders: The ConcurrentBag and BlockingCollection ConcurrentDictionary Thread-safe version of a dictionary. Optimized for multiple readers (allows multiple readers under same lock). For more information see C#/.NET Little Wonders: The ConcurrentDictionary BlockingCollection Wrapper collection that implement producers & consumers paradigm. Readers can block until items are available to read. Writers can block until space is available to write (if bounded). For more information see C#/.NET Little Wonders: The ConcurrentBag and BlockingCollection Summary The .NET BCL has lots of collections built in to help you store and manipulate collections of data. Understanding how these collections work and knowing in which situations each container is best is one of the key skills necessary to build more performant code. Choosing the wrong collection for the job can make your code much slower or even harder to maintain if you choose one that doesn’t perform as well or otherwise doesn’t exactly fit the situation. Remember to avoid the original collections and stick with the generic collections.  If you need concurrent access, you can use the generic collections if the data is read-only, or consider the concurrent collections for mixed-access if you are running on .NET 4.0 or higher.   Tweet Technorati Tags: C#,.NET,Collecitons,Generic,Concurrent,Dictionary,List,Stack,Queue,SortedList,SortedDictionary,HashSet,SortedSet

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• How to acces a global variable in a callback object in javascript YUI without use window.myvariable

  - by quilovnic

  I have this : var MyObject = function(){ this.url = "monurl"; this.mavar = ""; this.Load = function(){ var callback = { success: function(o){ mavar = o.responseXML.getElementsByTagName("montag")[0].firstChild.nodeValue; } } YAHOO.util.Connect.asyncRequest('GET',url,callback); } } the mavar variable is not accessible. How can I do this ?

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• Can you call FB.login inside a callback from other FB methods (like FB.getLoginStatus) without triggering popup blockers?

  - by Erik Kallevig

  I'm trying to set up a pretty basic authentication logic flow with the FB JavaScript SDK to check a user's logged-in status and permissions before performing an action (and prompting the user to login with permissions if they are not)... User types a message into a textarea on my site to post to their Facebook feed and click's a 'post to facebook' button on my site. In response to the click, I check user's logged in status with FB.getLoginStatus In the callback to FB.getLoginStatus, if user is not logged in, prompt them to login (FB.login). In the callback to FB.login I then need to make sure they have the right permissions so I make a call to FB.api('/me/permissions') -- if they don't , I again prompt them to login (FB.login) The problem I'm running into is that anytime I try to call FB.login inside a callback to other FB methods, the browser seems to lose track of the origin of execution (the click) and thus will block the popup. I'm wondering if I'm missing some way to prompt the user to login after checking their status without the browser mistakenly thinking that it's not a user-initiated popup? I've currently fallen back to just calling FB.login() first regardless. The undesired side effect of this approach, however, is that if the user is already logged-in with permissions and I'm still calling FB.login, the auth popup will open and close immediately before continuing, which looks rather buggy despite being functional. It seems like checking a user's login status and permissions before doing something would be a common flow so I feel like I'm missing something. Here's some example code. <div onclick="onClickPostBtn()">Post to Facebook</div> <script> // Callback to click on Post button. function onClickPostBtn() { // Check if logged in, prompt to do so if not. FB.getLoginStatus(function(response) { if (response.status === 'connected') { checkPermissions(response.authResponse.accessToken); } else { FB.login(function(){}, {scope: 'publish_stream'}) } }); } // Logged in, check permissions. function checkPermissions(accessToken) { FB.api('/me/permissions', {'access_token': accessToken}, function(response){ // Logged in and authorized for this site. if (response.data && response.data.length) { // Parse response object to check for permission here... if (hasPermission) { // Logged in with permission, perform some action. } else { // Logged in without proper permission, request login with permissions. FB.login(function(){}, {scope: 'publish_stream'}) } // Logged in to FB but not authorized for this site. } else { FB.login(function(){}, {scope: 'publish_stream'}) } } ); } </script>

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• Why does linux-image-virtual depend on a generic kernel now?

  - by ændrük

  The linux-image-virtual metapackage has historically provided a kernel that is specifically designed for use in virtual machines: Ubuntu 8.04: linux-image-2.6.24-32-virtual Ubuntu 10.04: linux-image-2.6.32-44-virtual Ubuntu 11.10: linux-image-3.0.0-26-virtual Ubuntu 12.04: linux-image-3.2.0-32-virtual Apparently, this has now changed: Ubuntu 12.10: linux-image-3.5.0-17-generic What's the explanation? Is this still the correct kernel to use in a virtual machine?

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• Why is lowlatency kernel not being updated in parallel with the generic kernel?

  - by FlabbergastedPickle

  All, Any idea when we'll see updates to the lowlatency version of the Ubuntu 12.04 kernel? It is still stuck at 3.2.0.23 whereas the generic kernel is already several updates ahead of it at a version 3.2.0.25? NB: I am using a 64-bit version but I don't think this is limited to the 64-bit kernels alone but rather affects both 32-bit and 64-bit builds. Please do correct me if I am wrong about this.

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• Should I have a separate method for Update(), Insert(), etc., or have a generic Query() that would be able to handle all of these?

  - by Prayos

  I'm currently trying to write a class library for a connection to a database. Looking over it, there are several different types of queries: Select From, Update, Insert, etc. My question is, what is the best practice for writing these queries in a C# application? Should I have a separate method for each of them(i.e. Update(), Insert()), or have a generic Query() that would be able to handle all of these? Thanks for any and all help!

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• Call an member function implementing the {{#linkTo ...}} helper from javascript code

  - by gonvaled

  I am trying to replace this navigation menu: <nav> {{#linkTo "nodes" }}<i class="icon-fixed-width icon-cloud icon-2x"></i>&nbsp;&nbsp;{{t generic.nodes}} {{grayOut "(temporal)"}}{{/linkTo}} {{#linkTo "services" }}<i class="icon-fixed-width icon-phone icon-2x"></i>&nbsp;&nbsp;{{t generic.services}}{{/linkTo}} {{#linkTo "agents" }}<i class="icon-fixed-width icon-headphones icon-2x"></i>&nbsp;&nbsp;{{t generic.agents}}{{/linkTo}} {{#linkTo "extensions" }}<i class="icon-fixed-width icon-random icon-2x"></i>&nbsp;&nbsp;{{t generic.extensions}}{{/linkTo}} {{#linkTo "voiceMenus" }}<i class="icon-fixed-width icon-sitemap icon-2x"></i>&nbsp;&nbsp;{{t generic.voicemenus}}{{/linkTo}} {{#linkTo "queues" }}<i class="icon-fixed-width icon-tasks icon-2x"></i>&nbsp;&nbsp;{{t generic.queues}}{{/linkTo}} {{#linkTo "contacts" }}<i class="icon-fixed-width icon-user icon-2x"></i>&nbsp;&nbsp;{{t generic.contacts}}{{/linkTo}} {{#linkTo "accounts" }}<i class="icon-fixed-width icon-building icon-2x"></i>&nbsp;&nbsp;{{t generic.accounts}}{{/linkTo}} {{#linkTo "locators" }}<i class="icon-fixed-width icon-phone-sign icon-2x"></i>&nbsp;&nbsp;{{t generic.locators}}{{/linkTo}} {{#linkTo "phonelocations" }}<i class="icon-fixed-width icon-globe icon-2x"></i>&nbsp;&nbsp;{{t generic.phonelocations}}{{/linkTo}} {{#linkTo "billing" }}<i class="icon-fixed-width icon-euro icon-2x"></i>&nbsp;&nbsp;{{t generic.billing}}{{/linkTo}} {{#linkTo "profile" }}<i class="icon-fixed-width icon-cogs icon-2x"></i>&nbsp;&nbsp;{{t generic.profile}}{{/linkTo}} {{#linkTo "audio" }}<i class="icon-fixed-width icon-music icon-2x"></i>&nbsp;&nbsp;{{t generic.audio}}{{/linkTo}} {{#linkTo "editor" }}<i class="icon-fixed-width icon-puzzle-piece icon-2x"></i>&nbsp;&nbsp;{{t generic.node_editor}}{{/linkTo}} </nav> With a more dynamic version. What I am trying to do is to reproduce the html inside Ember.View.render, but I would like to reuse as much Ember functionality as possible. Specifically, I would like to reuse the {{#linkTo ...}} helper, with two goals: Reuse existing html rendering implemented in the {{#linkTo ...}} helper Get the same routing support that using the {{#linkTo ...}} in a template provides. How can I call this helper from within javascript code? This is my first (incomplete) attempt. The template: {{view SettingsApp.NavigationView}} And the view: var trans = Ember.I18n.t; var MAIN_MENU = [ { 'linkTo' : 'nodes', 'i-class' : 'icon-cloud', 'txt' : trans('generic.nodes') }, { 'linkTo' : 'services', 'i-class' : 'icon-phone', 'txt' : trans('generic.services') }, ]; function getNavIcon (data) { var linkTo = data.linkTo, i_class = data['i-class'], txt = data.txt; var html = '<i class="icon-fixed-width icon-2x ' + i_class + '"></i>&nbsp;&nbsp;' + txt; return html; } SettingsApp.NavigationView = Ember.View.extend({ menu : MAIN_MENU, render: function(buffer) { for (var i=0, l=this.menu.length; i<l; i++) { var data = this.menu[i]; // TODO: call the ember function implementing the {{#linkTo ...}} helper buffer.push(getNavIcon(data)); } return buffer; } });

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• How do I make lambda functions generic in Scala?

  - by Electric Coffee

  As most of you probably know you can define functions in 2 ways in scala, there's the 'def' method and the lambda method... making the 'def' kind generic is fairly straight forward def someFunc[T](a: T) { // insert body here what I'm having trouble with here is how to make the following generic: val someFunc = (a: Int) => // insert body here of course right now a is an integer, but what would I need to do to make it generic? val someFunc[T] = (a: T) => doesn't work, neither does val someFunc = [T](a: T) => Is it even possible to make them generic, or should I just stick to the 'def' variant?

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• How could I know if an object is derived from a specific generic class?

  - by Edison Chuang

  Suppose that I have an object then how could I know if the object is derived from a specific generic class. For example: public class GenericClass<T> { } public bool IsDeriveFrom(object o) { return o.GetType().IsSubclassOf(typeof(GenericClass)); //will throw exception here } please notice that the code above will throw an exception. The type of the generic class cannot be retrieved directly because there is no type for a generic class without a type parameter provided.

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• Imperative vs. LINQ Performance on WP7

  - by Bil Simser

  Jesse Liberty had a nice post presenting the concepts around imperative, LINQ and fluent programming to populate a listbox. Check out the post as it’s a great example of some foundational things every .NET programmer should know. I was more interested in what the IL code that would be generated from imperative vs. LINQ was like and what the performance numbers are and how they differ. The code at the instruction level is interesting but not surprising. The imperative example with it’s creating lists and loops weighs in at about 60 instructions. .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } 1: .method private hidebysig instance void ImperativeMethod() cil managed 2: { 3: .maxstack 3 4: .locals init ( 5: [0] class [mscorlib]System.Collections.Generic.IEnumerable`1<int32> someData, 6: [1] class [mscorlib]System.Collections.Generic.List`1<int32> inLoop, 7: [2] int32 n, 8: [3] class [mscorlib]System.Collections.Generic.IEnumerator`1<int32> CS$5$0000, 9: [4] bool CS$4$0001) 10: L_0000: nop 11: L_0001: ldc.i4.1 12: L_0002: ldc.i4.s 50 13: L_0004: call class [mscorlib]System.Collections.Generic.IEnumerable`1<int32> [System.Core]System.Linq.Enumerable::Range(int32, int32) 14: L_0009: stloc.0 15: L_000a: newobj instance void [mscorlib]System.Collections.Generic.List`1<int32>::.ctor() 16: L_000f: stloc.1 17: L_0010: nop 18: L_0011: ldloc.0 19: L_0012: callvirt instance class [mscorlib]System.Collections.Generic.IEnumerator`1<!0> [mscorlib]System.Collections.Generic.IEnumerable`1<int32>::GetEnumerator() 20: L_0017: stloc.3 21: L_0018: br.s L_003a 22: L_001a: ldloc.3 23: L_001b: callvirt instance !0 [mscorlib]System.Collections.Generic.IEnumerator`1<int32>::get_Current() 24: L_0020: stloc.2 25: L_0021: nop 26: L_0022: ldloc.2 27: L_0023: ldc.i4.5 28: L_0024: cgt 29: L_0026: ldc.i4.0 30: L_0027: ceq 31: L_0029: stloc.s CS$4$0001 32: L_002b: ldloc.s CS$4$0001 33: L_002d: brtrue.s L_0039 34: L_002f: ldloc.1 35: L_0030: ldloc.2 36: L_0031: ldloc.2 37: L_0032: mul 38: L_0033: callvirt instance void [mscorlib]System.Collections.Generic.List`1<int32>::Add(!0) 39: L_0038: nop 40: L_0039: nop 41: L_003a: ldloc.3 42: L_003b: callvirt instance bool [mscorlib]System.Collections.IEnumerator::MoveNext() 43: L_0040: stloc.s CS$4$0001 44: L_0042: ldloc.s CS$4$0001 45: L_0044: brtrue.s L_001a 46: L_0046: leave.s L_005a 47: L_0048: ldloc.3 48: L_0049: ldnull 49: L_004a: ceq 50: L_004c: stloc.s CS$4$0001 51: L_004e: ldloc.s CS$4$0001 52: L_0050: brtrue.s L_0059 53: L_0052: ldloc.3 54: L_0053: callvirt instance void [mscorlib]System.IDisposable::Dispose() 55: L_0058: nop 56: L_0059: endfinally 57: L_005a: nop 58: L_005b: ldarg.0 59: L_005c: ldfld class [System.Windows]System.Windows.Controls.ListBox PerfTest.MainPage::LB1 60: L_0061: ldloc.1 61: L_0062: callvirt instance void [System.Windows]System.Windows.Controls.ItemsControl::set_ItemsSource(class [mscorlib]System.Collections.IEnumerable) 62: L_0067: nop 63: L_0068: ret 64: .try L_0018 to L_0048 finally handler L_0048 to L_005a 65: } 66:   67: Compare that to the IL generated for the LINQ version which has about half of the instructions and just gets the job done, no fluff. .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } 1: .method private hidebysig instance void LINQMethod() cil managed 2: { 3: .maxstack 4 4: .locals init ( 5: [0] class [mscorlib]System.Collections.Generic.IEnumerable`1<int32> someData, 6: [1] class [mscorlib]System.Collections.Generic.IEnumerable`1<int32> queryResult) 7: L_0000: nop 8: L_0001: ldc.i4.1 9: L_0002: ldc.i4.s 50 10: L_0004: call class [mscorlib]System.Collections.Generic.IEnumerable`1<int32> [System.Core]System.Linq.Enumerable::Range(int32, int32) 11: L_0009: stloc.0 12: L_000a: ldloc.0 13: L_000b: ldsfld class [System.Core]System.Func`2<int32, bool> PerfTest.MainPage::CS$<>9__CachedAnonymousMethodDelegate6 14: L_0010: brtrue.s L_0025 15: L_0012: ldnull 16: L_0013: ldftn bool PerfTest.MainPage::<LINQProgramming>b__4(int32) 17: L_0019: newobj instance void [System.Core]System.Func`2<int32, bool>::.ctor(object, native int) 18: L_001e: stsfld class [System.Core]System.Func`2<int32, bool> PerfTest.MainPage::CS$<>9__CachedAnonymousMethodDelegate6 19: L_0023: br.s L_0025 20: L_0025: ldsfld class [System.Core]System.Func`2<int32, bool> PerfTest.MainPage::CS$<>9__CachedAnonymousMethodDelegate6 21: L_002a: call class [mscorlib]System.Collections.Generic.IEnumerable`1<!!0> [System.Core]System.Linq.Enumerable::Where<int32>(class [mscorlib]System.Collections.Generic.IEnumerable`1<!!0>, class [System.Core]System.Func`2<!!0, bool>) 22: L_002f: ldsfld class [System.Core]System.Func`2<int32, int32> PerfTest.MainPage::CS$<>9__CachedAnonymousMethodDelegate7 23: L_0034: brtrue.s L_0049 24: L_0036: ldnull 25: L_0037: ldftn int32 PerfTest.MainPage::<LINQProgramming>b__5(int32) 26: L_003d: newobj instance void [System.Core]System.Func`2<int32, int32>::.ctor(object, native int) 27: L_0042: stsfld class [System.Core]System.Func`2<int32, int32> PerfTest.MainPage::CS$<>9__CachedAnonymousMethodDelegate7 28: L_0047: br.s L_0049 29: L_0049: ldsfld class [System.Core]System.Func`2<int32, int32> PerfTest.MainPage::CS$<>9__CachedAnonymousMethodDelegate7 30: L_004e: call class [mscorlib]System.Collections.Generic.IEnumerable`1<!!1> [System.Core]System.Linq.Enumerable::Select<int32, int32>(class [mscorlib]System.Collections.Generic.IEnumerable`1<!!0>, class [System.Core]System.Func`2<!!0, !!1>) 31: L_0053: stloc.1 32: L_0054: ldarg.0 33: L_0055: ldfld class [System.Windows]System.Windows.Controls.ListBox PerfTest.MainPage::LB2 34: L_005a: ldloc.1 35: L_005b: callvirt instance void [System.Windows]System.Windows.Controls.ItemsControl::set_ItemsSource(class [mscorlib]System.Collections.IEnumerable) 36: L_0060: nop 37: L_0061: ret 38: } Again, not surprising here but a good indicator that you should consider using LINQ where possible. In fact if you have ReSharper installed you’ll see a squiggly (technical term) in the imperative code that says “Hey Dude, I can convert this to LINQ if you want to be c00L!” (or something like that, it’s the 2010 geek version of Clippy). What about the fluent version? As Jon correctly pointed out in the comments, when you compare the IL for the LINQ code and the IL for the fluent code it’s the same. LINQ and the fluent interface are just syntactical sugar so you decide what you’re most comfortable with. At the end of the day they’re both the same. Now onto the numbers. Again I expected the imperative version to be better performing than the LINQ version (before I saw the IL that was generated). Call it womanly instinct. A gut feel. Whatever. Some of the numbers are interesting though. For Jesse’s example of 50 items, the numbers were interesting. The imperative sample clocked in at 7ms while the LINQ version completed in 4. As the number of items went up, the elapsed time didn’t necessarily climb exponentially. At 500 items they were pretty much the same and the results were similar up to about 50,000 items. After that I tried 500,000 items where the gap widened but not by much (2.2 seconds for imperative, 2.3 for LINQ). It wasn’t until I tried 5,000,000 items where things were noticeable. Imperative filled the list in 20 seconds while LINQ took 8 seconds longer (although personally I wouldn’t suggest you put 5 million items in a list unless you want your users showing up at your door with torches and pitchforks). Here’s the table with the full results. Method/Items 50 500 5,000 50,000 500,000 5,000,000 Imperative 7ms 7ms 38ms 223ms 2230ms 20974ms LINQ/Fluent 4ms 6ms 41ms 240ms 2310ms 28731ms Like I said, at the end of the day it’s not a huge difference and you really don’t want your users waiting around for 30 seconds on a mobile device filling lists. In fact if Windows Phone 7 detects you’re taking more than 10 seconds to do any one thing, it considers the app hung and shuts it down. The results here are for Windows Phone 7 but frankly they're the same for desktop and web apps so feel free to apply it generally. From a programming perspective, choose what you like. Some LINQ statements can get pretty hairy so I usually fall back with my simple mind and write it imperatively. If you really want to impress your friends, write it old school then let ReSharper do the hard work for! Happy programming!

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• Ubuntu stops using Nvidia driver after kernel upgrade

  - by Daniel

  Just updated and restarted, Ubuntu's doesn't display correctly. After restart, the desktop now looks like this. I've temporarily switched to the Nouveau driver. The update history reveals the kernel was updated, amongst many things; and the following were installed: linux-image-3.5.0-19-generic (3.5.0-19.30) linux-image-extra-3.5.0-19-generic (3.5.0-19.30) I've encountered this type of problem quite recently, so I decided to reapply the same steps, to solve the problem, as follows: sudo apt-get install linux-headers-3.5.0-19 sudo apt-get install linux-headers-3.5.0-19-generic sudo depmod -a sudo modprobe nvidia sudo /etc/init.d/*dm restart When installing linux-headers-3.5.0-19-generic, I get an error, message from terminal as follows: Setting up linux-headers-3.5.0-19-generic (3.5.0-19.30) ... Examining /etc/kernel/header_postinst.d. run-parts: executing /etc/kernel/header_postinst.d/dkms 3.5.0-19-generic /boot/vmlinuz-3.5.0-19-generic Error! Problems with depmod detected. Automatically uninstalling this module. DKMS: Install Failed (depmod problems). Module rolled back to built state. However, I ignored the above error and continued the steps with sudo depmod -a, installed nvidia-current, then did sudo modprobe nvidia, which yielded the following error: FATAL: Error inserting nvidia_current (/lib/modules/3.5.0-19-generic/updates/dkms/nvidia_current.ko): No such device Upon restart, the Nvidia driver now works! BTW, do those error messages imply I broke something? Just curious, cause I don't want to get happy I've fixed it, then it stops working later on. The system is Dell XPS-L702X, with NVIDIA GeForce GT 555M, and 17" screen.

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• dpkg reporting as installed, uninstalled kernels

  - by Tony Martin

  I have run the following command to remove old kernels: dpkg -l 'linux-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d;s/^[^ ]* [^ ]* \([^ ]*\).*/\1/;/[0-9]/!d' | xargs sudo apt-get -y purge and only the current kernel is now installed, which I have confirmed in synaptic and by checking my boot partition. However, when I run: dpkg --list | grep linux-image I get the following response: rc linux-image-3.13.0-30-generic 3.13.0-30.55 amd64 Linux kernel image for version 3.13.0 on 64 bit x86 SMP rc linux-image-3.13.0-32-generic 3.13.0-32.57 amd64 Linux kernel image for version 3.13.0 on 64 bit x86 SMP ii linux-image-3.13.0-34-generic 3.13.0-34.60 amd64 Linux kernel image for version 3.13.0 on 64 bit x86 SMP rc linux-image-extra-3.13.0-30-generic 3.13.0-30.55 amd64 Linux kernel extra modules for version 3.13.0 on 64 bit x86 SMP rc linux-image-extra-3.13.0-32-generic 3.13.0-32.57 amd64 Linux kernel extra modules for version 3.13.0 on 64 bit x86 SMP ii linux-image-extra-3.13.0-34-generic 3.13.0-34.60 amd64 Linux kernel extra modules for version 3.13.0 on 64 bit x86 SMP ii linux-image-generic 3.13.0.34.40 amd64 Generic Linux kernel image Probably not a problem, but just wondering why versions -30 and -32 are reported as present. Can it be rectified? TIA

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• Get Func-y v2.0

  - by PhubarBaz

  In my last post I talked about using funcs in C# to do async calls in WinForms to free up the main thread for the UI. In that post I demonstrated calling a method and then waiting until the value came back. Today I want to talk about calling a method and then continuing on and handling the results of the async call in a callback.The difference is that in the previous example although the UI would not lock up the user couldn't really do anything while the other thread was working because it was waiting for it to finish. This time I want to allow the user to continue to do other stuff while waiting for the thread to finish.Like before I have a service call I want to make that takes a long time to finish defined in a method called MyServiceCall. We need to define a callback method takes an IAsyncResult parameter.public ServiceCallResult MyServiceCall(int param1)...public int MyCallbackMethod(IAsyncResult ar)...We start the same way by defining a delegate to the service call method using a Func. We need to pass an AsyncCallback object into the BeginInvoke method. This will tell it to call our callback method when MyServiceCall finishes. The second parameter to BeginInvoke is the Func delegate. This will give us access to it in our callback.Func<int, ServiceCallResult> f = MyServiceCall;AsyncCallback callback =   new AsyncCallback(MyCallbackMethod);IAsyncResult async = f.BeginInvoke(23, callback, f); Now let's expand the callback method. The IAsyncResult parameter contains the Func delegate in its AsyncState property. We call EndInvoke on that Func to get the return value.public int MyCallbackMethod(IAsyncResult ar){    Func<int, ServiceCallResult> delegate =        (Func<int, ServiceCallResult>)ar.AsyncState;    ServiceCallResult result = delegate.EndInvoke(ar);}There you have it. Now you don't have to make the user wait for something that isn't critical to the loading of the page.

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• "Unmet Dependencies" problem when trying apt-get install

  - by GChorn

  Anytime I try to install python packages using the command: sudo apt-get install python-package I get the following output: Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies: linux-headers-generic : Depends: linux-headers-3.2.0-36-generic but it is not going to be installed linux-headers-generic-pae : Depends: linux-headers-3.2.0-36-generic-pae but it is not going to be installed linux-image-generic : Depends: linux-image-3.2.0-36-generic but it is not going to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution). This seems to have started when these same three packages showed up in Ubuntu's Update Manager and kicked an error when I tried to install them there. Based on the suggestion in the output above, I tried running: sudo apt-get -f install But this only gave me several instances of the following error: dpkg: error processing /var/cache/apt/archives/linux-image-3.2.0-36-generic_3.2.0-36.57_i386.deb (--unpack): unable to create `/lib/modules/3.2.0-36-generic/kernel/drivers/net/wireless/ath/carl9170/carl9170.ko.dpkg-new' (while processing `./lib/modules/3.2.0-36-generic/kernel/drivers/net/wireless/ath/carl9170/carl9170.ko'): No space left on device Now maybe I'm way off-base here, but I'm wondering if the error could be coming from the "No space left on device" part? The thing is, I'm running Ubuntu as a VirtualBox VM but I've got it set to dynamically increase its virtual hard drive space as needed, so why am I still getting this error? Here's my output when I use dh -f: Filesystem Size Used Avail Use% Mounted on /dev/sda1 6.9G 5.7G 869M 88% / udev 494M 4.0K 494M 1% /dev tmpfs 201M 784K 200M 1% /run none 5.0M 0 5.0M 0% /run/lock none 501M 76K 501M 1% /run/shm VB_Shared_Folder 466G 271G 195G 59% /media/sf_VB_Shared_Folder When I perform sudo apt-get -f install and the system says, After this operation, 192 MB of additional disk space will be used. Does that mean 192 MB of my virtual machine's current memory, or 192 MB on top of the rest of my free space? As I said, my machine normally dynamically allocates additional memory from the host machine, so I don't see why there would be memory restrictions at all...

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• SmtpClient.SendAsync - How to ensure my application doesn't finish before callback?

  - by James

  Hi, I need to send emails asychronously through a console application. I need to do some DB updates on the callback but my application is exiting before the callback code gets run! How can I stop this from happening in a nice manner rather than simply guessing how long to wait before exiting. I would imagine the Async calls get placed in some form of thread? Is it possible to check if any are waiting to be called? Sample Code private static void SendCompletedCallback(object sender, AsyncCompletedEventArgs e) { // Get the unique identifier for this asynchronous operation. String token = (string) e.UserState; if (e.Cancelled) { Console.WriteLine("[{0}] Send canceled.", token); } if (e.Error != null) { Console.WriteLine("[{0}] {1}", token, e.Error.ToString()); } else { // update DB Console.WriteLine("Message sent."); } } public static void Main(string[] args) { var users = Repository.GetUsers(); SmtpClient client = new SmtpClient("Host"); client.SendCompleted += new SendCompletedEventHandler(SendCompletedCallback); MailAddress from = new MailAddress("[email protected]", "System", Encoding.UTF8); foreach (var user in users) { MailAddress to = new MailAddress(user.Email); MailMessage message = new MailMessage(from, to); message.Body = "This is a test"; message.BodyEncoding = System.Text.Encoding.UTF8; message.Subject = "test message 1" + someArrows; message.SubjectEncoding = System.Text.Encoding.UTF8; string userState = String.Format("Message for user id {0}", user.ID); client.SendAsync(message, userState); message.Dispose(); } // need to wait here until I have received a callback for each message // otherwise the application will exit }

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• jQuery Mobile: How to run a callback-function before $.mobile.changePage?

  - by Jugi84

  I'm setting up a mobile app with jQuery Mobile and PhoneGap. What I want to do is that when I click link with id "news_link" I want jQuery to fetch data from database and put it to jQm's collapsible set. In my solution, I've wanted to use $.mobile.changePage inside callback functions because I want to wait until the data has been fetched and put inside the container before the code changes page. Here's the code: $(function() { $('#news_link').click(function(){ loadNewsFromDB(function(){ $.mobile.changePage( $("#news"), { transition: "slideup"} ); }); }); loadNewsFromDB is PhoneGap's SQLite database function which would fetch the data with more callback functions from database. The contents would be put to desired container with .html-function function loadNewsFromDB(){ //some code here theDB.transaction(function(tx) { tx.executeSql(sqlStr, [], onLoadNewsSuccess, onLoadNewsError); },onTxError, onTxSuccess); function onLoadNewsSuccess(tx, results){ //some code here $("#newsSet").html(htmlCodeAndContentToPut); Html is jQm's basic ui-modules: <!-- some html code here --!> <div data-role="page" id="news"> <div data-role="content"> <div id="newsSet" data-role="collapsible-set" data-mini="true"> With debugging I know that the code work up until it works very well unti it arrives to $.mobile.changePage-function. Somehow it doesn't change the page. I've checked the function it works well in other occasions, but not inside callback-functions. I would be very grateful if someone would give me a hand am I not seeing something obviously wrong or is something more specific? What other workarounds there is for fetching the data from SQLite, waiting for data to be fetched, putting the data to container and then changing the pages?

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