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• My wireless has suddenly became disabled by hardware switch, BIOS, rfkill, fn+f8 do nothing

  - by cwwk

  I have a toshiba l655d-s5145. There is no physical toggle for the wireless, although the f8 key is supposed to do the trick. It doesn't. The wireless has been working since October, and suddenly, nothing. RFKILL reports that the wireless is hard blocked, but unblock wifi, unblock 0, unblock all do nothing. I inserted a usb dongle, and that is also disabled by hardware switch, although rfkill reports that it is neither hard nor soft blocked. My onboard wireless is 02:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8188CE 802.11b/g/n WiFi Adapter (rev 01) according to lspci. Lsmod reports that these drivers are loaded. rtl8192c_common 75767 1 rtl8192ce rtlwifi 110972 1 rtl8192ce I resorted to reformatting the drive and reinstalling, but that also did not work. In BIOS I restored system defaults as there is no specific entry for wifi. Before reinstalling a pure xubuntu I went into Unity and saw that the airplane mode was on and despite being toggled off, it returned to the on position. I'm not sure where to find airplane mode in Xubuntu. What else can I do? I need my wireless.

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• How to configure KDE default settings for a new user of a group?

  - by Adobe

  I'm a sys admin on Kubuntu 11.10 machine. Where do I configure the basic config for a new user (say belonging to group "users")? Edit 1: I want to configure langauages - currently my new users get English and Bulgarian Languages. I want them to get English and Russian - and also to set Alt-CapsLock - to be the input-language-switching-combination. Edit 2: How do I configure things in /usr/share/kde4 When I do kdesudo systemsettings and save configurations - only root settings got changed - not the /usr/share/kde4 ones. Edit 3: New user gets the /etc/skel files controlling bash behaviour-appearence. What about the KDE new user's default files - where are they stored? Edit 4: Oh, I found some hints: kde4-config --path config gives a list of folders (separated by the colon) where KDE looks for configs. My machine responded with: /home/boris/.kde/share/config/ /etc/kde4/ /usr/share/kubuntu-default-settings/kde4-profile/default/share/config/ /usr/share/kde4/config/ /usr/share/desktop-base/profiles/kde-profile/share/config/ It looks like third line is where KDE takes the default options. So I found these zilions of settings - but no GUI way to configure it ((. Edit 5: Finally, I've created a dummy user, configured it, and wrote a script which gives it's settings to a given user(s). The trick - is to chown after one transfered the dot files from one user to another. I've tested it - it works fine.

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• ifconfig can't see USB wireless

  - by Alex

  I have a wifi USB dongle which I have previously used on a Raspberry Pi (this it is what it is target at). I am trying to get it working on an Nvidia Jetson TK1, however I am having some problems. When I run ifconfig I can't see the wifi, only the ethernet and local loopback. iwconfig reports no wireless extensions on all devices. lsusb does find the device: Bus 002 Device 008: ID 148f:5370 Ralink Technology, Corp. RT5370 Wireless Adapter So I am not sure why the network tools can't see it. I have tried logging on with a GUI and opening up the network settings through Unity, but cannot see any wireless devices either. Not sure if this is useful, but output of lsmod: Module Size Used by nvhost_vi 2940 0 How can I enable wireless networking on this computer? Command line approach is preferred, but either is fine. UPDATE I don't have the kernel module rt2800usb anywhere on my system. If I do an apt-file search for rt2800usb it lists a number of packages of the pattern: linux-image-3.13.0-*. Perhaps installing one of these will do the trick, but can anyone tell me if its safe to do so?

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• How can I remove unmounted SD Card icons from my desktop?

  - by user75286

  I have been using some audio utilities in Ubuntu 11.10 to tweak .mp3 files on my phone (Motorola Photon 4G). I connect via USB... both my phone and the internal SD card are mounted as two separate drives. The SD card has an unusual drive name with some odd characters. When I'm finished, I unmount my phone (or "safely remove drive"), but the SD card can't be unmounted. I've mounted and unmounted my phone on 4 occasions now, and there are now 4 SD card drive icons that I can't remove from the desktop. I tried using the gconf-editor/apps/nautilus/desktop trick to make drives invisible and it's not working. Right-clicking on the icons and selecting "unmount" produced the following error message; (I can't type the unusual drive name characters... replaced with xxx) Unable to unmount xxx umount: /media/xxx is not mounted (according to mtab) How can I remove the unwanted icons from the desktop and is there a method for avoiding this problem in the future? Thanks!

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• Should I listen to my employer and use CASE tools?

  - by omsharp

  My employer (Not a Developer) thinks that CASE tools will help us improve our development process and documentation. I am not sure about that, we are a small team of 5 developers building mobile banking solutions for local clients. I think CASE tools will be a waste of time and money as they need to be purchased and we will need some time before we get used to them and be efficient working with them for modeling and stuff. Code generation is another issue, I really think that the CASE generated code won't be as good as code written by good developers. I think that if we stick with agile princeliness, design patterns, use TDD, and keep our code clean. we should be good. And as far as Analysis and Design, I think simple UML diagrams on whiteboard should do the trick. Documentation is good and important, but should be made as little as possible and we should not focus on Docs and forget the code. This is what i think. Am I correct? or should I listen to my employer and start researching for an appropriate CASE Tool?

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• Using pkexec policy to run out of /opt/

  - by liberavia

  I still try to make it possible to run my app with root priveleges. Therefore I created two policies to run the application via pkexec (one for /usr/bin and one for /opt/extras... ) and added them to the setup.py: data_files=[('/usr/share/polkit-1/actions', ['data/com.ubuntu.pkexec.armorforge.policy']), ('/usr/share/polkit-1/actions', ['data/com.ubuntu.extras.pkexec.armorforge.policy']), ('/usr/bin/', ['data/armorforge-pkexec'])] ) additionally I added a startscript which uses pkexec for starting the application. It distinguishes between the two places and is used in the Exec-Statement of the desktopfile: #!/bin/sh if [ -f /opt/extras.ubuntu.com/armorforge/bin/armorforge ]; then pkexec "/opt/extras.ubuntu.com/armorforge/bin/armorforge" "$@" else pkexec `which armorforge` "$@" fi If I simply do a quickly package everything will work right. But if I package with extras option: quickly package --extras the Exec-statement will be exchanged. Even if I try to simulate the pkexec call via armorforge-pkexec It will aks for a password and then returns this: andre@andre-desktop:~/Entwicklung/Ubuntu/armorforge$ armorforge-pkexec (armorforge:10108): GLib-GIO-ERROR **: Settings schema 'org.gnome.desktop.interface' is not installed Trace/breakpoint trap (core dumped) So ok, I could not trick the opt-thing. How can I make sure, that my Application will run with root priveleges out of opt. I copied the way of using pkexec from synaptic. My application is for communicating with apparmor which currently has no dbus interface. Else I need to write into /etc/apparmor.d-folder. How should I deal with the opt-build which, as far as I understand, is required to submit my application to the ubuntu software center. Thanks for any hints and/or links :-)

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• SEO and internal links

  - by hanazair

  I'm fairly new to SEO and although I've read many articles on the topic I still don't have a clear idea of how to get my client's website get to the first page of Google Search. I run MOZ competitor analysis and see that a competitor that comes up at the top of Google Search has approximately same Domain Authority, Domain Moz Rank and Trust. They have 8 External Linking Root Domains while my client's site has five. Yet the competitor comes up as one of the top sites on the first page, and my client's side is on page #3. Then I noticed one drastic difference in competitor's ranking and that is Total Links. He has 1,388! I don't understand how this could be a positive factor in Search Engine ranking and how can they legitimately have 1,388 links (while only 14 of those are external). Another competitor who is #2 in search engine rankings has 773 links total with only 14 external links. It seems fishy, but yet there they are - at the top of the search engine results. Is that some current way to trick Search Engines? What to do if I'd like to get my client's website onto the first page by some legitimate means? Thanks.

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• Create a system image in Windows 8

  - by Greg Low

  One of the things that I've just come to accept is that the designers of Windows 8 and I think very differently.It'll take a long time to convince me that shutting down the computer is a "setting". Even after using Windows 8 for quite a while now, I still find that I struggle nearly every day, just trying to do things that I previously knew how to do. That's just not a good thing.Today I decided to create a system image as I hadn't made one lately. I started in Control Panel looking for Backup options. That yielded nothing except programs that wanted to "Save backup copies of my files with file history". I thought "oh well, let's just try the new search options". I hit the Windows key and typed "Backup". No, nothing came up there either.I searched again all over the Control Panel options to no avail.So it was time to hit Google again. Once again, clearly lots of people used to know how to do this and have been trying to work out where this option went.The first trick is that there are a bunch of Control Panel options that don't appear in the Control Panel. In the address bar at the top, if you click on Control Panel, you'll find there is an option that says "All Control Panel Options". That is curious given that's where I thought I was when I opened Control Panel. No hint is given on that screen that there are a bunch of hidden options. None the less, I then checked out "all" the options.The option that you need to create a system image in Windows 8 turns out to be the "Windows 7 File Recovery" option that appears in this extended list. Why does it say "Windows 7" when it's for "Windows 8" as well and I'm running "Windows 8"? Why do I have to choose an option that says "File Recovery" to create a system image backup?<sigh>But at least I've recorded it here for the next time I forget where to find it.

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• Is Moving Entity Framework objects over a webservice really the best way?

  - by aceinthehole

  I've inherited a .NET project that has close to 2 thousand clients out in the field that need to push data periodically up to a central repository. The clients wake up and attempt to push the data up via a series of WCF webservices where they are passing each entity framework entity as parameter. Once the service receives this object, it preforms some business logic on the data, and then turns around and sticks it in it's own database that mirrors the database on the client machines. The trick is, is that this data is being transmitted over a metered connection, which is very expensive. So optimizing the data is a serious priority. Now, we are using a custom encoder that compresses the data (and decompresses it on the other end) while it is being transmitted, and this is reducing the data footprint. However, the amount of data that the clients are using, seem ridiculously large, given the amount of information that is actually being transmitted. It seems me that entity framework itself may be to blame. I'm suspecting that the objects are very large when serialized to be sent over wire, with a lot context information and who knows what else, when what we really need is just the 'new' inserts. Is using the entity framework and WCF services as we have done so far the correct way, architecturally, of approaching this n-tiered, asynchronous, push only problem? Or is there a different approach, that could optimize the data use?

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• Weird bug in Visual Studio 11 Beta when running on Windows 8

  - by raccoon_tim

  With the Windows 8 Consumer Preview version out in the open and the Visual Studio 11 Beta also available, I’ve been putting some more effort into trying them both out. The first impression of the new Visual Studio 11 build was: Why doesn’t it work at all on Windows 8?! The issues I encountered were odd to say the least. Visual Studio did install correctly, which was a good sign, but when I started it, I was greeted with a multitude of popups each telling me that some package could not be loaded. So I clicked away for quite some time to finally be greeted by the new default visual style of Visual Studio. The next thing I wanted to do was start a new project so I pressed “New Project” and got the “Microsoft.VisualStudio.Dialogs.DialogInitializationException” exception. After some pondering and even submitting a bug report I found another already reported bug “http://connect.microsoft.com/VisualStudio/feedback/details/727578/vs-do-not-work-with-finnish-number-format-on-w8-64-bit”. It turns out that the dialog initialization failure has something to do with the packages no being loaded and following the presented workaround helped. The trick is to change the negative number sign to “-“ (U+002D) from the additional settings of your regional settings. This issue appears to have a wider reach than just Visual Studio as I heard at TechDays Finland 2012 that the same fix has to be made when using Hyper-V.

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• Is The Ease Of Windows Phone Development Ruining Its Image

  - by Tim Murphy

  I was reading an article on Mashable recently by a long time iPhone user who is living solely on a Lumia 920 at the moment and giving her assessment.  One thing that struck a nerve with me was her describing the Windows Phone ecosystem as immature.  She wasn’t saying this because of the number of apps or the big names like most people do.  She means the quality of the apps in the store. This hit a nerve with me.  I find it hard to believe that the majority of app on iOS are of any higher quality than any other platform.  I believe in any ecosystem you are going to find some high end, high quality apps, but the majority by default will be from people who are trying to solve a problem but do not have the resources to have top graphics and full blown testing.  There will also be a large number that are just there trying to trick you into giving up some cash. Does any of the mean that we shouldn’t take notice of this complaint?  Of course not!  We should always strive to publish the best quality apps possible.  Don’t do things like leaving default app icons and backgrounds.  Put a little effort into your design.  You should also spend as much time as possible ensuring against crashes and giving the user the best experience possible.  Think through your apps organization and navigation.  Go the extra step of putting it into beta and letting select people use it and give you feedback before going to full release. Remember, if we want people to appreciate the Windows Phone platform we have to make sure we give them apps that they are going to enjoy using. del.icio.us Tags: Windows Phone,iPhone,iOS,Nokia,Lumia 920,Mashable

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• How do I troubleshoot system slowness seen when viewing PDFs or videos?

  - by asp

  Whenever I watch videos, either online of local via Totem and/or open PDF files using evince. The system gets really, really bogged down. All apps get really slow, menus take forever to display, switching windows gives me time to make a coffee, etc. I have a couple of bug reports open on this, but what do I need to do to really troubleshoot the issue? I've purged Adobe Flash from the system, but YouTube HTML5 videos still have the issue. A bunch of PDFs saved locally trigger the problem. And to (temporarily) remove the slowness, I need to shutdown the computer, breath for a few minutes, then restart. A simple reboot does not do the trick. How can I identify the cause? This only started on 13.04. I've had Ubuntu on this machine for a year without a problem until "upgrading" to 13.04. I am not a programmer, but I suspect an issue with the Intel video driver. Is there something I can run which will diagnose this, or are there concrete steps I can follow to find the culprit?

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• Samba share external USB device

  - by bioShark

  I managed to share stuff from my Ubuntu 12.04 to my private network, and the data is visible from a Windows machine. I even shared a hdd that has windows on it. So everything seems to work fine. When I want to share a mounted device (USB pen drive, USB HDD... etc) however, I get from the Windows machine: Access denied on file \... I realize that this is due to the missing rights on the mounted folder. By default a mounted folder gets the equivalent of 700 : drwx------, and the owner myself. But, I can't seem to change the rights on the external device... they remain 700. Is there a special trick I need to do in order to share NTFS mounted usb devices? Thanks P.S. from this Question I see that NTFS devices can not be shared....is this true? It's a bit strange, because I have in my PC 2 HDD's with 3 NTFS partitions, and I can share them without a problem.

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• Enable [command] key to register as something other than just [ctrl]?

  - by gojomo

  I'm running 10.04LTS inside VMWare Fusion on a Mac. The [command] key (aka [windows] on many keyboards) is almost always behaving as if it was [ctrl], even though I done anything explicit to request that behavior. In fact, in SystemPreferencesKeyboardLayoutsOptionsAlt/Win key behavior, 'default' is chosen (rather than the 'Control is mapped to Win keys' option). However, choosing other options there do not seem to change the handling of [command], at least not as tested in the SystemPreferenceKeyboard Shortcuts app. (No matter what I've tried, [command]-x is always detected as [Ctrl]-x in that app.) I've tried: various options under SystemPreferencesKeyboardLayoutsOptionsAlt/Win key behavior toggling the VMWare Fusion Preferences KKeyboard & Mouse Key Mappings setup which claims to map '[command]' to '[windows]', and restarting the VM in each position the xmodmap lines suggested at https://help.ubuntu.com/community/MappingWindowsKey And yet, it's clear that all Ubuntu apps aren't merging [ctrl] and [command], because in 'Terminal', [shift]-[ctrl]-c will Copy, but [shift]-[command]-c will not. If the [command]/[windows] key was recognized as anything else ('Super', 'Meta', 'Hyper'? I don't care as long as it's not 'Control'), then I could achieve my real goal (which happens to be enabling CMD-based cut/copy/paste in PyCharm, while leaving CTRL-X/etc available for emacs-like bindings). I think any solution which manages to make [command]-x appear as something other than [ctrl]-x in PreferencesKeyboard Shortcuts will probably do the trick.

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• Can't connect nonlocally after 12.10 upgrade

  - by user101815

  I've just upgraded one of my systems from 12.04 to 12.10. Now I can't connect on that system beyond my local network. Connections within the local network seem to work fine, and I can make nonlocal connections from other machines (like the one I'm asking this question from). I suspect that some routing information has been messed up, but I don't know where to look for it. It's not a nameserver problem -- pinging outside sites by their IP addresses doesn't work either. I have another laptop next to this one, also running Kubuntu 12.10. On the one that can't connect, arp produces no output. On the other one, it produces 192.168.0.1 ether 00:23:69:fa:ce:ae C wlan0 On the working machine, the output of netstat starts with some tcp entries. On the nonworking one, those entries are absent. I asked this question on the Ubuntu forum but haven't gotten any answers there. One further complication: since the troublesome machine has no outside connection, it's extremely difficult to download anything to it. For what it's worth, "ping 8.8.8.8" produces "connect: Network is unreachable". Update: after a lot of fiddling, I have my external world back. I don't know what the key action was, but the first indication of progress was that "ping 8.8.8.8" worked. At that point I still didn't have a working nameserver, so external URLs didn't work. But I did this (based on an online post, of course): sudo dpkg-reconfigure resolvconf and answered Yes to all prompts. That did the trick!! Apparently my problem was unique, or close to it, since I couldn't find any online references to it: local net working, remote net not working, including explicit IP addresses. So I suppose that if no one else has this problem, no one cares about the solution!!

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• How to set individual NTFS partitions permissions behaviour for each user account?

  - by ryniek

  I have two NTFS partitions (DOWNLOADS for downloaded files and VM for my VirtualBox .vdi file) for which i must have full permissions for my allday use account. They should be also automounting when i login to this account. But i've also set Guest account for guests. For Guest account, i want make VM partition fully disabled and invisible (and thus it mustn't automount) but DOWNLOADS partition should be shared with limited privileges with Guest account. Editing fstab i'm able to share DOWNLOADS partition with Guest on limited privileges but VM can be only set to limited and have disabled automounting - so guest can't mount it but it still can be seen in Nautilus, plus I must always mount it manually when i login to allday account. Is there some trick to make what i want? Here's my fstab config: # /etc/fstab: static file system information. # # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 #Entry for /dev/sda1 : UUID=35e66658-5ee9-40cf-bf56-8204959e3df0 / xfs defaults 01 #Entry for /dev/sda2 : UUID=26c714cf-4236-45e7-9c46-cfcf91a215ae /home xfs defaults 02 #Entry for /dev/sda5 : UUID=1315BCB027C44639 /media/DOWNLOADS ntfs-3g auto,uid=1000,gid=1000,umask=0022,nodev,locale=pl_PL.utf8 0 0 #Entry for /dev/sda6 : UUID=60FF39EB72B72264 /media/VM ntfs noauto,uid=1000,gid=1000,umask=0077,nodev,locale=pl_PL.utf8 0 0 #Entry for /dev/sda7 : UUID=c52411f5-105c-45d1-971f-412f962c350e none swap sw 0 0 /dev/fd0 /media/floppy0 auto rw,user,noauto,exec,utf8 0 0 Thanks

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• Dual boot problem with ubuntu 12.04 and Vista

  - by vendella dahlahdoo

  Greetings from New Zealand. I have installed Microsoft Windows Vista and then installed Ubuntu 12.04 on my refurbished Compaq nx8220 laptop. I get the following infamous head hurting prompt continually. error: no such partition. grub rescue> Have tried most of the common recommended solutions. Live-CD then install Boot-Repair through the Terminal didn't work. It repaired all the linux stuff when restoring grub and then can't boot into Windows Vista. When I use Boot-Repair to fix the MBR, then I can't boot into Ubuntu. Tried installing BCD 2.1 in Vista and tried all the options one after another in BCD. Still no Ubuntu when selected through the options menu from BCD on restart/reboot. I have tried the boot repair option on the Ubuntu server CD-ROM, tried installing earlier versions of Ubuntu 11.04, 11.10, and Ubuntu server 11.10 and 12.04. Still the same result. I tried deleting the Ubuntu partitions through Vista a number of times and reinstalling Ubuntu. I have been trying and retrying all the options in Boot-Repair in different combinations for the past week and a half. I have tried at least 10 times installing and reinstalling Ubuntu. I really love Ubuntu and believe I have exhausted most of the recommended solutions and have spent too much time on this. Its driving me nuts!! please can someone help, I have finally given up (sigh). The following are some outputs from Boot-Repair from my last attempts. http://paste.ubuntu.com/1019227 http://paste.ubuntu.com/1019264 I was only allowed to post two links being a newbie. The only thing left for me to do is the flying Samoan dropkick laptop trick. Thanks in advance. Francis.

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• What is the standard way of using Q15 values?

  - by Alex

  To process 8-bit pixels, to do things like gamma correction without losing information, we normally upsample the values, work in 16 bits or whatever, and then downsample them to 8 bits. Now, this is a somewhat new area for me, so please excuse incorrect terminology etc. For my needs I have chosen to work in "non-standard" Q15, where I only use the upper half of the range (0.0-1.0), and 0x8000 represents 1.0 instead of -1.0. This makes it much easier to calculate things in C. But I ran into a problem with SSSE3. It has the PMULHRSW instruction which multiplies Q15 numbers, but it uses the "standard" range of Q15 is [-1,1-2?¹5], so multplying (my) 0x8000 (1.0) by 0x4000 (0.5) gives 0xC000 (-0.5), because it thinks 0x8000 is -1. This is quite annoying. What am I doing wrong? Should I keep my pixel values in the 0000-7FFF range? This kind of defeats the purpose of it being a fixed-point format. Is there a way around this? Maybe some trick? Is there some kind of definitive treatise on Q15 which discusses all this?

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• Sorting Algorithms

  - by MarkPearl

  General Every time I go back to university I find myself wading through sorting algorithms and their implementation in C++. Up to now I haven’t really appreciated their true value. However as I discovered this last week with Dictionaries in C# – having a knowledge of some basic programming principles can greatly improve the performance of a system and make one think twice about how to tackle a problem. I’m going to cover briefly in this post the following: Selection Sort Insertion Sort Shellsort Quicksort Mergesort Heapsort (not complete) Selection Sort Array based selection sort is a simple approach to sorting an unsorted array. Simply put, it repeats two basic steps to achieve a sorted collection. It starts with a collection of data and repeatedly parses it, each time sorting out one element and reducing the size of the next iteration of parsed data by one. So the first iteration would go something like this… Go through the entire array of data and find the lowest value Place the value at the front of the array The second iteration would go something like this… Go through the array from position two (position one has already been sorted with the smallest value) and find the next lowest value in the array. Place the value at the second position in the array This process would be completed until the entire array had been sorted. A positive about selection sort is that it does not make many item movements. In fact, in a worst case scenario every items is only moved once. Selection sort is however a comparison intensive sort. If you had 10 items in a collection, just to parse the collection you would have 10+9+8+7+6+5+4+3+2=54 comparisons to sort regardless of how sorted the collection was to start with. If you think about it, if you applied selection sort to a collection already sorted, you would still perform relatively the same number of iterations as if it was not sorted at all. Many of the following algorithms try and reduce the number of comparisons if the list is already sorted – leaving one with a best case and worst case scenario for comparisons. Likewise different approaches have different levels of item movement. Depending on what is more expensive, one may give priority to one approach compared to another based on what is more expensive, a comparison or a item move. Insertion Sort Insertion sort tries to reduce the number of key comparisons it performs compared to selection sort by not “doing anything” if things are sorted. Assume you had an collection of numbers in the following order… 10 18 25 30 23 17 45 35 There are 8 elements in the list. If we were to start at the front of the list – 10 18 25 & 30 are already sorted. Element 5 (23) however is smaller than element 4 (30) and so needs to be repositioned. We do this by copying the value at element 5 to a temporary holder, and then begin shifting the elements before it up one. So… Element 5 would be copied to a temporary holder 10 18 25 30 23 17 45 35 – T 23 Element 4 would shift to Element 5 10 18 25 30 30 17 45 35 – T 23 Element 3 would shift to Element 4 10 18 25 25 30 17 45 35 – T 23 Element 2 (18) is smaller than the temporary holder so we put the temporary holder value into Element 3. 10 18 23 25 30 17 45 35 – T 23   We now have a sorted list up to element 6. And so we would repeat the same process by moving element 6 to a temporary value and then shifting everything up by one from element 2 to element 5. As you can see, one major setback for this technique is the shifting values up one – this is because up to now we have been considering the collection to be an array. If however the collection was a linked list, we would not need to shift values up, but merely remove the link from the unsorted value and “reinsert” it in a sorted position. Which would reduce the number of transactions performed on the collection. So.. Insertion sort seems to perform better than selection sort – however an implementation is slightly more complicated. This is typical with most sorting algorithms – generally, greater performance leads to greater complexity. Also, insertion sort performs better if a collection of data is already sorted. If for instance you were handed a sorted collection of size n, then only n number of comparisons would need to be performed to verify that it is sorted. It’s important to note that insertion sort (array based) performs a number item moves – every time an item is “out of place” several items before it get shifted up. Shellsort – Diminishing Increment Sort So up to now we have covered Selection Sort & Insertion Sort. Selection Sort makes many comparisons and insertion sort (with an array) has the potential of making many item movements. Shellsort is an approach that takes the normal insertion sort and tries to reduce the number of item movements. In Shellsort, elements in a collection are viewed as sub-collections of a particular size. Each sub-collection is sorted so that the elements that are far apart move closer to their final position. Suppose we had a collection of 15 elements… 10 20 15 45 36 48 7 60 18 50 2 19 43 30 55 First we may view the collection as 7 sub-collections and sort each sublist, lets say at intervals of 7 10 60 55 – 20 18 – 15 50 – 45 2 – 36 19 – 48 43 – 7 30 10 55 60 – 18 20 – 15 50 – 2 45 – 19 36 – 43 48 – 7 30 (Sorted) We then sort each sublist at a smaller inter – lets say 4 10 55 60 18 – 20 15 50 2 – 45 19 36 43 – 48 7 30 10 18 55 60 – 2 15 20 50 – 19 36 43 45 – 7 30 48 (Sorted) We then sort elements at a distance of 1 (i.e. we apply a normal insertion sort) 10 18 55 60 2 15 20 50 19 36 43 45 7 30 48 2 7 10 15 18 19 20 30 36 43 45 48 50 55 (Sorted) The important thing with shellsort is deciding on the increment sequence of each sub-collection. From what I can tell, there isn’t any definitive method and depending on the order of your elements, different increment sequences may perform better than others. There are however certain increment sequences that you may want to avoid. An even based increment sequence (e.g. 2 4 8 16 32 …) should typically be avoided because it does not allow for even elements to be compared with odd elements until the final sort phase – which in a way would negate many of the benefits of using sub-collections. The performance on the number of comparisons and item movements of Shellsort is hard to determine, however it is considered to be considerably better than the normal insertion sort. Quicksort Quicksort uses a divide and conquer approach to sort a collection of items. The collection is divided into two sub-collections – and the two sub-collections are sorted and combined into one list in such a way that the combined list is sorted. The algorithm is in general pseudo code below… Divide the collection into two sub-collections Quicksort the lower sub-collection Quicksort the upper sub-collection Combine the lower & upper sub-collection together As hinted at above, quicksort uses recursion in its implementation. The real trick with quicksort is to get the lower and upper sub-collections to be of equal size. The size of a sub-collection is determined by what value the pivot is. Once a pivot is determined, one would partition to sub-collections and then repeat the process on each sub collection until you reach the base case. With quicksort, the work is done when dividing the sub-collections into lower & upper collections. The actual combining of the lower & upper sub-collections at the end is relatively simple since every element in the lower sub-collection is smaller than the smallest element in the upper sub-collection. Mergesort With quicksort, the average-case complexity was O(nlog2n) however the worst case complexity was still O(N*N). Mergesort improves on quicksort by always having a complexity of O(nlog2n) regardless of the best or worst case. So how does it do this? Mergesort makes use of the divide and conquer approach to partition a collection into two sub-collections. It then sorts each sub-collection and combines the sorted sub-collections into one sorted collection. The general algorithm for mergesort is as follows… Divide the collection into two sub-collections Mergesort the first sub-collection Mergesort the second sub-collection Merge the first sub-collection and the second sub-collection As you can see.. it still pretty much looks like quicksort – so lets see where it differs… Firstly, mergesort differs from quicksort in how it partitions the sub-collections. Instead of having a pivot – merge sort partitions each sub-collection based on size so that the first and second sub-collection of relatively the same size. This dividing keeps getting repeated until the sub-collections are the size of a single element. If a sub-collection is one element in size – it is now sorted! So the trick is how do we put all these sub-collections together so that they maintain their sorted order. Sorted sub-collections are merged into a sorted collection by comparing the elements of the sub-collection and then adjusting the sorted collection. Lets have a look at a few examples… Assume 2 sub-collections with 1 element each 10 & 20 Compare the first element of the first sub-collection with the first element of the second sub-collection. Take the smallest of the two and place it as the first element in the sorted collection. In this scenario 10 is smaller than 20 so 10 is taken from sub-collection 1 leaving that sub-collection empty, which means by default the next smallest element is in sub-collection 2 (20). So the sorted collection would be 10 20 Lets assume 2 sub-collections with 2 elements each 10 20 & 15 19 So… again we would Compare 10 with 15 – 10 is the winner so we add it to our sorted collection (10) leaving us with 20 & 15 19 Compare 20 with 15 – 15 is the winner so we add it to our sorted collection (10 15) leaving us with 20 & 19 Compare 20 with 19 – 19 is the winner so we add it to our sorted collection (10 15 19) leaving us with 20 & _ 20 is by default the winner so our sorted collection is 10 15 19 20. Make sense? Heapsort (still needs to be completed) So by now I am tired of sorting algorithms and trying to remember why they were so important. I think every year I go through this stuff I wonder to myself why are we made to learn about selection sort and insertion sort if they are so bad – why didn’t we just skip to Mergesort & Quicksort. I guess the only explanation I have for this is that sometimes you learn things so that you can implement them in future – and other times you learn things so that you know it isn’t the best way of implementing things and that you don’t need to implement it in future. Anyhow… luckily this is going to be the last one of my sorts for today. The first step in heapsort is to convert a collection of data into a heap. After the data is converted into a heap, sorting begins… So what is the definition of a heap? If we have to convert a collection of data into a heap, how do we know when it is a heap and when it is not? The definition of a heap is as follows: A heap is a list in which each element contains a key, such that the key in the element at position k in the list is at least as large as the key in the element at position 2k +1 (if it exists) and 2k + 2 (if it exists). Does that make sense? At first glance I’m thinking what the heck??? But then after re-reading my notes I see that we are doing something different – up to now we have really looked at data as an array or sequential collection of data that we need to sort – a heap represents data in a slightly different way – although the data is stored in a sequential collection, for a sequential collection of data to be in a valid heap – it is “semi sorted”. Let me try and explain a bit further with an example… Example 1 of Potential Heap Data Assume we had a collection of numbers as follows 1[1] 2[2] 3[3] 4[4] 5[5] 6[6] For this to be a valid heap element with value of 1 at position [1] needs to be greater or equal to the element at position [3] (2k +1) and position [4] (2k +2). So in the above example, the collection of numbers is not in a valid heap. Example 2 of Potential Heap Data Lets look at another collection of numbers as follows 6[1] 5[2] 4[3] 3[4] 2[5] 1[6] Is this a valid heap? Well… element with the value 6 at position 1 must be greater or equal to the element at position [3] and position [4]. Is 6 > 4 and 6 > 3? Yes it is. Lets look at element 5 as position 2. It must be greater than the values at [4] & [5]. Is 5 > 3 and 5 > 2? Yes it is. If you continued to examine this second collection of data you would find that it is in a valid heap based on the definition of a heap.

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• Prevent ASP.net __doPostback() from jQuery submit() within UpdatePanel

  - by Ed Woodcock

  I'm trying to stop postback on form submit if my custom jQuery validation returns false. Is there any way to prevent the __doPostback() function finishing from within the submit() function? I'd assumed: $('#aspnetForm').submit(function () { return false; }); would do the trick, but apparently that's not the case: does anyone have a suggestion? The submit() function does block the postback (it won't postback if you pause at a breakpoint in firebug), but I can't seem to stop the event happening after the submit() function is complete! Cheers, Ed EDIT OK, I had a quick mess about and discovered that the fact that the button I'm using to cause the postback is tied to an updatepanel as an asyncpostbacktrigger seems to be the problem: If I remove it as a trigger (i.e. cause it to product a full postback), the is no problem preventing the postback with return false; Any ideas why the async postback would not be stoppable using return false?

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• android listview set dynamically background color of views

  - by Sephy

  Hi everybody, I know that there have quite a lot of answers to similar questions but I couldn't find any solution to my question, so new topic : I'm creating a listview, with one basic view per row, my try is to change the background color of the view by .setbackgroundcolor, but nothing's doing the trick... I define an array of color at the beginning of my resources and i'm trying to display it, I also tried to put the array in the class, write the color like #00FF00, int, and I wanted to try 0x...... but as my colors are in an array, I can't do 0x+myColorsArray[i] because Eclipse tells me that it's not a proper hex color... I'm getting a bit desperate... thanks for any help

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• TVirtualStringTree compatibility between Delphi 7 and Delphi 2010 - 'Parameter lists differ'

  - by Brian Frost

  Hi, I've made a form containing a TVirtualStringTree that works in Delphi 7 and Delphi 2010. I notice that as I move between the two platforms I get the message '...parameter list differ..' on the tree events and that the string type is changing bewteen TWideString (D7) and string (D2010). The only trick I've found to work to suppress this error is to use compiler directives as follows: {$IFDEF TargetDelphi7} procedure VirtualStringTree1GetText(Sender: TBaseVirtualTree; Node: PVirtualNode; Column: TColumnIndex; TextType: TVSTTextType; var CellText: WideString); {$ELSE} procedure VirtualStringTree1GetText(Sender: TBaseVirtualTree; Node: PVirtualNode; Column: TColumnIndex; TextType: TVSTTextType; var CellText: string); {$ENDIF} and to repeat this where the events are implemented. Am I missing a simple solution? Thanks.

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• ASP.NET MVC Html.ActionLink Maintains Route Values

  - by Carl

  Hi, I have a question that has pretty much been asked here: http://stackoverflow.com/questions/780643/asp-net-mvc-html-actionlink-keeping-route-value-i-dont-want However, the final solution is a kludge, pure and simple and I really would like to understand why this happens, if someone can please explain it to me? For completeness, it is possible to recreate the scenario very easily: Create a new MVC web app. Run it up. Visit the About tab Modify the URL to read /Home/About/Flib - This obviously takes you to the action with an id of 'Flib' which we don't care about. Notice that the top menu link to About now actually links to /Home/About/Flib - this is wrong as far as I can see, as I now have absolutely no way of using site links to get back to /Home/About I really don't understand why I should be forced to modify all of my Html.ActionLinks to include new { id = string.Empty } for the routevalues and null for the htmlAttribs. This seems especially out of whack because I already specify id = 0 as part of the route itself. Hopefully I'm missing a trick here.

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• Help with Algorithm chinese auction

  - by sam munkes

  Hi, i am designing a Chinese auction website. Tickets ($5, $10 & $20) are sold either individually, or via packages to receive discounts. There are various Ticket packages for example: 5-$5 tickets = receive 10% off 5-$10 tickets = receive 10% off 5-$20 tickets = receive 10% off 5-$5 tickets + 5-$10 tickets + 5-$20 tickets = receive 15% off When users add tickets to their cart, i need to figure out the cheapest package(s) to give them. the trick is that if a user adds 4-$5 tickets + 5-$10 tickets + 5-$20 tickets, it should still give him package #3 since that would be the cheapest for him. Any help in figuring out a algorithm to solve this, or any tips would be greatly appreciate it. thanks

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• Reporting Services 2010 RDLC: Passing Querystring Parameters from an RDLC

  - by Brian MacKay

  I'm trying to build a simple RDLC report that shows some data, and has a 'select' link that sends the browser off to a certain url with some data in the querystring (a key). In the vs2010 report designer, I can double-click on the column, then select action, and there are a bunch of thigns that seem like they might work. But none of them do. Under 'enable as a hyperlink' I can pick 'go to url' but there aren't any parameter options to pass. I also tried 'go to report' on the off chance that I could trick it into doing what I want. Here there are parameter options, but it knows that my url is not a report and the "select" link renders as text (not clickable). Any ideas? I'm pretty sure this used to work in vs2008, and it seems like something that must be doable. But I've been pulling out my hair for several hours on this one.

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