Search Results

Search found 2397 results on 96 pages for 'alex kachanov'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 3/96 | < Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >

  • ArrayAdapter throwing ArrayIndexOutOfBoundsException

    - by alex
    I am getting an error of an array out of bounce error when i am using my custom array adapter. I am wondering if there are any coding errors I have overlooked. Here is the error log 06-10 20:21:53.254: E/AndroidRuntime(315): FATAL EXCEPTION: main 06-10 20:21:53.254: E/AndroidRuntime(315): java.lang.RuntimeException: Unable to start activity ComponentInfo{alex.android.galaxy.tab.latest/alex.android.galaxy.tab.latest.Basic_db_output}: java.lang.ArrayIndexOutOfBoundsException 06-10 20:21:53.254: E/AndroidRuntime(315): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 06-10 20:21:53.254: E/AndroidRuntime(315): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 06-10 20:21:53.254: E/AndroidRuntime(315): at android.app.ActivityThread.access$2300(ActivityThread.java:125) 06-10 20:21:53.254: E/AndroidRuntime(315): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 06-10 20:21:53.254: E/AndroidRuntime(315): at android.os.Handler.dispatchMessage(Handler.java:99) 06-10 20:21:53.254: E/AndroidRuntime(315): at android.os.Looper.loop(Looper.java:123) 06-10 20:21:53.254: E/AndroidRuntime(315): at android.app.ActivityThread.main(ActivityThread.java:4627) 06-10 20:21:53.254: E/AndroidRuntime(315): at java.lang.reflect.Method.invokeNative(Native Method) 06-10 20:21:53.254: E/AndroidRuntime(315): at java.lang.reflect.Method.invoke(Method.java:521) 06-10 20:21:53.254: E/AndroidRuntime(315): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 06-10 20:21:53.254: E/AndroidRuntime(315): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 06-10 20:21:53.254: E/AndroidRuntime(315): at dalvik.system.NativeStart.main(Native Method) 06-10 20:21:53.254: E/AndroidRuntime(315): Caused by: java.lang.ArrayIndexOutOfBoundsException 06-10 20:21:53.254: E/AndroidRuntime(315): at alex.android.galaxy.tab.latest.Basic_db_output.onCreate(Basic_db_output.java:44) 06-10 20:21:53.254: E/AndroidRuntime(315): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 06-10 20:21:53.254: E/AndroidRuntime(315): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) I am basing my code example on this How to use ArrayAdapter<myClass> ArrayList list = new ArrayList(); for(int i=1; i <= 3; i++) { Reader reader = new ResultsReader("android_galaxy_tab_latest/src/quiz"+i+".txt"); reader.read(); String str = ((ResultsReader)reader).getInput(); String data[] = str.split("<.>"); Question q = new Question(); q.question = data[0]; q.answer = Integer.parseInt(data[1]); q.choice1 = data[2]; q.choice2 = data[3]; q.choice3 = data[4]; list.add(q); }

    Read the article

  • ResultSet and aggregation

    - by kachanov
    Ok, I admit my situation is special There is a data system that supports SQL-92 and JDBC interface However the SQL requets are pretty expensive, and in my application I need to retreive the same data multiple times and aggregate it ("group by") on different fields to show different dimensions of the same data. For example on one screen I have three tables that show the same set or records but aggregated by City (1st grid), by Population (2nd grid), by number of babies (3rd grid) This amounts to 3 SQL queries (which is very slow), UNLESS anyone of you can suggest any idea any library from apache commons or from google code, so that I can select all records into ResultSet and get 3 arrays of data group by different fields from this single ResultSet. Am I'm missing some obvious and unexpected solution to this problem?

    Read the article

  • After-meeting Free Pizza Social is back to Fladotnet's West Palm Beach .Net User Group

    - by Sam Abraham
    Sherlock Staffing is bringing back the free Pizza/Soda after-meeting social to Fladotnet's West Palm Beach .Net User Group. Group members will have ample time to network and share experiences while enjoying pizza and soda after each meeting. Alex Funkhouser, Sherlock Staffing's President and Chief Talent Agent, is a continuous supporter of the .Net community with Sherlock Staffing maintaining a strong presence in every user group and quickly stepping-in as sponsors to meet any arising community need. In addition to providing the Free Pizza and Soda, Sherlock Staffing will also maintain on-site presence to bring to members of the West Palm Beach .Net User Group the latest insider view on the Job Market and keep the group posted with available opportunities. Alex can be reached at: [email protected]. Check out Sherlock Staffing's Website at: http://www.sherstaff.com About Sherlock Staffing SherStaff is the premier staffing and consulting source for technical talent in Florida and beyond. The company provides recruiting and consulting services to both Fortune 1000 companies and to job candidates in a wide range of technology areas of expertise including the Microsoft Technologies, Oracle, WebSphere, Java/J2EE, and open source/Linux based technologies.  The primary focus is recruiting application developers, network engineers and database administrators. The company prides itself on the long term relationships established with both employers and employees to ensure placement of the best quality candidates in the top quality jobs.

    Read the article

  • So i ran sudo apt-get install kubuntu-full on my Ubuntu... and saw all the apps...now I want it off...help?

    - by Alex Poulos
    I'm running 12.04 - I installed kubuntu to try it out and realized that with all the bloatware applications that I didn't want it anymore - I was able to uninstall the kubuntu-desktop but there are still packages left over... How can I make sure I get rid of EVERYTHING Kubuntu installed - even the kde leftovers? Here's some of what's left when I ran sudo apt-get autoremove kde then "tab" it displayed this: kdeaccessibility kdepim-runtime kdeadmin kde-runtime kde-baseapps kde-runtime-data kde-baseapps-bin kdesdk-dolphin-plugins kde-baseapps-data kde-style-oxygen kde-config-cron kdesudo kde-config-gtk kdeutils kde-config-touchpad kde-wallpapers kdegames-card-data kde-wallpapers-default kdegames-card-data-extra kde-window-manager kde-icons-mono kde-window-manager-common kdelibs5-data kde-workspace kdelibs5-plugins kde-workspace-bin kdelibs-bin kde-workspace-data kdemultimedia-kio-plugins kde-workspace-data-extras kdenetwork kde-workspace-kgreet-plugins kdenetwork-filesharing kde-zeroconf kdepasswd kdf kdepim-kresources kdm kdepimlibs-kio-plugins kdoctools Those are all installed by kubuntu... correct? I just want to go back to my Ubuntu 12.04LTS with Gnome2-classic and without all the kubuntu extras. I started it off by just removing unnecessary apps that came with kubuntu-full - then realized I didnt want the whole thing at all and uninstalled kubuntu-full but it still says I have these as well: alex@griever:~$ sudo apt-get --purge remove kubuntu- kubuntu-debug-installer kubuntu-netbook-default-settings kubuntu-default-settings kubuntu-notification-helper kubuntu-firefox-installer kubuntu-web-shortcuts

    Read the article

  • What makes a Software Craftsman?

    - by Liam McLennan
    At the end of my visit to 8th Light Justin Martin was kind enough to give me a ride to the train station; for my train back to O’Hare. Just before he left he asked me an interesting question which I then posted to twitter: Liam McLennan: . @JustinMartinM asked what I think is the most important attributes of craftsmen. I said, "desire to learn and humility". What's yours? 6:25 AM Apr 17th via TweetDeck several people replied with excellent contributions: Alex Hung: @liammclennan I think kaizen sums up craftmanship pretty well, which is almost same as yours Steve Bohlen: @alexhung @liammclennan those are both all about saying "knowing what you don't know and not being afraid to go learn it" (and I agree!) Matt Roman: @liammclennan @JustinMartinM a tempered compulsion for constant improvement, and an awareness of what needs improving. Justin Martin: @mattroman @liammclennan a faculty for asking challenging questions, and a persistence to battle through difficult obstacles barring growth I thought this was an interesting conversation, and I would love to see other people contribute their opinions. My observation is that Alex, Steve, Matt and I seem to have essentially the same answer in different words. It is also interesting to note (as Alex pointed out) that these definitions are very similar to Alt.NET and the lean concept of kaizen.

    Read the article

  • Web Development Environment: How to distribute edited hosts files over bunch of mac machines?

    - by Alex Reds
    I am doing some research to prepare some web development environment for our small(10ppl and growing) new office. User Case: For each new web project usually we create new alias on an Apache server someproject.companywebsite From my understanding in order to see this website locally for all the rest of our team(including mangers and directors) they will need to edit hosts file (e.g. "192.168.1.10 someproject.companywebsite"), and like that each time for a new project(can be 2-5 each week) Solution: And I looking for a solution how to edit this hosts file only once and distribute it over all mac machines in our network at once or much more flawlessly than poking around with each machine every time over and over again. Is that possible? Or that a very wrong way of doing that? Perhaps we better set up own local dns server and point to it our router? Though own dns server a bit concerns me because of might be some network interruption and others lags, if you know what I mean. Or perhaps there are another workflows for that? What's the best way for such things? So I'll be so grateful to hear some advices from experienced admins. I couldn't find that info on internet, so if you know where to read about it, point me in a right direction. Thank you in advance Alex

    Read the article

  • Oracle Flashback Technology - Webcast 9th June 2010

    - by Alex Blyth
    Hi All Here are the details for webcast on Oracle Flashback Technologies on Wednesday (9th June 2010) beginning at 1.30pm (Sydney, Australia Time). The Oracle Database architecture leverages the unique technological advances in the area of database recovery due to human errors. Oracle Flashback Technology provides a set of new features to view and rewind data back and forth in time. The Flashback features offer the capability to query historical data, perform change analysis, and perform self-service repair to recover from logical corruptions while the database is online. With Oracle Flashback Technology, you can indeed undo the past! Oracle9i introduced Flashback Query to provide a simple, powerful and completely non-disruptive mechanism for recovering from human errors. It allows users to view the state of data at a point in time in the past without requiring any structural changes to the database. Oracle Database 10g extended the Flashback Technology to provide fast and easy recovery at the database, table, row, and transaction level. Flashback Technology revolutionizes recovery by operating just on the changed data. The time it takes to recover the error is now equal to the same amount of time it took to make the mistake. Oracle 10g Flashback Technologies includes Flashback Database, Flashback Table, Flashback Drop, Flashback Versions Query, and Flashback Transaction Query. Flashback technology can just as easily be utilized for non-repair purposes, such as historical auditing with Flashback Query and undoing test changes with Flashback Database. Oracle Database 11g introduces an innovative method to manage and query long-term historical data with Flashback Data Archive. This release also provides an easy, one-step transaction backout operation, with the new Flashback Transaction capability. Webcast is at http://strtc.oracle.com (IE6, 7 & 8 supported only)Conference ID for the webcast is 6690835Conference Key: flashbackEnrollment is required. Please click here to enroll.Please use your real name in the name field (just makes it easier for us to help you out if we can't answer your questions on the call) Audio details: NZ Toll Free - 0800 888 157 orAU Toll Free - 1800420354 (or +61 2 8064 0613)Meeting ID: 7914841Meeting Passcode: 09062010 Talk to you all Wednesday 9th June Alex

    Read the article

  • Estimate of Hits / Visits / Uniques in order to fall within a given Alexa Tier?

    - by Alex C
    I was wondering if anyone could offer up rough estimates that could tell me how many hits a day move you into a given Alexa rank ? Top 5,000 Top 10,000 Top 50,000 Top 100,000 Top 500,000 Top 1,000,000 I know this is incredibly subjective and thus the broad brush strokes with the number ranges... BUT I've got a site currently ranked just over 1.2M worldwide and over 500k in the USA (http://www.alexa.com/siteinfo/fstr.net) Pretty cool for something hand-built on weekends (pat self on back) I was applying to an ad-platform and was told that their program doesn't accept webmasters who have an Alexa rank of greater than 100,000. (Time to take back that pat on the back I guess). I know that my hits in the last 30 days are somewhere on the order of 15,000 uniques and 20,000 pageviews. So I'm wondering how much harder do I have to work to achieve my next "goals"? I'd like to break into the top million, then re-evaluate from there. It'd be nice to know what those targets translate into (very roughly of course). I imagine that alexa ranks and tiers become very much exponential as you move up the ranks, but even hearing annecdotal evidence from other webmasters would be really useful to me. (ie: I have a site that is ranked X and it got Y hits in the last 30 days) Thanks :) - Alex

    Read the article

  • Estimate of Hits / Visits / Uniques in order to fall within a given Alexa Tier?

    - by Alex C
    Hi there! I was wondering if anyone could offer up rough estimates that could tell me how many hits a day move you into a given Alexa rank ? Top 5,000 Top 10,000 Top 50,000 Top 100,000 Top 500,000 Top 1,000,000 I know this is incredibly subjective and thus the broad brush strokes with the number ranges... BUT I've got a site currently ranked just over 1.2M worldwide and over 500k in the USA (http://www.alexa.com/siteinfo/fstr.net) Pretty cool for something hand-built on weekends (pat self on back) I was applying to an ad-platform and was told that their program doesn't accept webmasters who have an Alexa rank of greater than 100,000. (Time to take back that pat on the back I guess). I know that my hits in the last 30 days are somewhere on the order of 15,000 uniques and 20,000 pageviews. So I'm wondering how much harder do I have to work to achieve my next "goals"? I'd like to break into the top million, then re-evaluate from there. It'd be nice to know what those targets translate into (very roughly of course). I imagine that alexa ranks and tiers become very much exponential as you move up the ranks, but even hearing annecdotal evidence from other webmasters would be really useful to me. (ie: I have a site that is ranked X and it got Y hits in the last 30 days) Thanks :) - Alex

    Read the article

  • Nginx load balancing policy

    - by Alex
    Is the Nginx's load balancing policy customizable in any way? Having two sites A and B I want 20% of all the requests to go to A and the rest to B. Is that possible/feasible? Is there a better solution out there for this task? Thanks, Alex

    Read the article

  • Unable to create a permanent alias in Mac OS

    - by Alex
    In Linux I can well to add alias to bashrc and it will become a permanent alias. In Mac OS I tried to do the same thing: vim ~/.bashrc export PATH="$PATH:$HOME/.rvm/bin" # Add RVM to PATH f or scripting alias prj="cd ~/Documents/projects" ### Added by the Heroku Toolbelt export PATH="/usr/local/heroku/bin:$PATH" That being said, I got this: $ alias alias rvm-restart='rvm_reload_flag=1 source '\''/Users/alex/.rvm/scripts/rvm'\''' So where is my prj alias? I rebooted the laptop but nothing has changed.

    Read the article

  • Ubuntu Server 12.04 Unable to locate package dhcp3-server

    - by Alex Hope O'Connor
    I have done a fresh install of Ubuntu Server version 12.04 and am trying to install a dhcp server package using the following command: sudo apt-get install dhcp3-server However I get this: Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package dhcp3-server Can someone tell me how to install this package on my server? Thanks, Alex.

    Read the article

  • Hyper-V/Ubuntu server 12.04 - VM does not stop

    - by Alex T.
    i just installed a ubuntu 12.04 server on a 2008 R2 Hyper-V server and all is fine (networking/storage ...). There is just one thing, when i halt my linux (using "sudo halt"), i can see on the console that the system is halted but the vm status on hyper-v is still "started". Then i need to stop it on the hyper-v management tool. Anybody has an idea on how to properly stop this VM on hyper-V automatically ? Thanks, Alex

    Read the article

  • Read NTFS partition on RHEL 5.8

    - by Alex Farber
    I have RHEL 5.8 64 bit, and NTFS partition on the same disk. How can I get access to this partition? This answer Unable to mount NTFS drive with RHEL 6 doesn't work for me: [root@localhost alex]# rpm -Uvh http://download.fedora.redhat.com/pub/epel/6/i386/epel-release-6-5.noarch.rpm Retrieving http://download.fedora.redhat.com/pub/epel/6/i386/epel-release-6-5.noarch.rpm error: skipping http://download.fedora.redhat.com/pub/epel/6/i386/epel-release-6-5.noarch.rpm - transfer failed - Unknown or unexpected error

    Read the article

  • Silverlight Cream for January 13, 2011 -- #1026

    - by Dave Campbell
    In this Issue: András Velvárt, Tony Champion, Joost van Schaik, Jesse Liberty, Shawn Wildermuth, John Papa, Michael Crump, Sacha Barber, Alex Knight, Peter Kuhn, Senthil Kumar, Mike Hole, and WindowsPhoneGeek. Above the Fold: Silverlight: "Create Custom Speech Bubbles in Silverlight." Michael Crump WP7: "Architecting WP7 - Part 9 of 10: Threading" Shawn Wildermuth Expression Blend: "PathListBox: Text on the path" Alex Knight From SilverlightCream.com: Behaviors for accessing the Windows Phone 7 MarketPlace and getting feedback András Velvárt shares almost insider information about how to get some user interaction with your WP7 app in the form of feedback ... he has 4 behaviors taken straight from his very cool SufCube app that he's sharing. Reloading a Collection in the PivotViewer Tony Champion keeps working with the PivotViewer ... this time discussing the fact that you can't Reload or Refresh the current collection from the server ... at least not initially, but he did find one :) Tombstoning MVVMLight ViewModels with SilverlightSerializer on Windows Phone 7 Joost van Schaik takes a shot at helping us all with Tombstoning a WP7 app... he's using Mike Talbot's SilverlightSerializer and created extension methods for it for tombstoning that he's willing to share with us. Windows Phone From Scratch #17: MVVM Light Toolkit Soup To Nuts Part 2 Jesse Liberty is up to Part 17 in his WP7 series, and this is the 2nd post on MVVMLight and WP7, and is digging into behaviors. Architecting WP7 - Part 9 of 10: Threading Shawn Wildermuth is up to part 9 of 10 in his series on Architecting WP7 apps. This episode finds Shawn discussing Threading ... know how to use and choose between BackgroundWorker and ThreadPool? ... Shawn will explain. Silverlight TV 57: Performance Tuning Your Apps In the latest Silverlight TV, John Papa chats with Mike Cook about tuning your Silverlight app to get the performance up there where your users will be happy. Create Custom Speech Bubbles in Silverlight. Michael Crump's already gotten a lot of airplay out of this, but it's so cool.. comic-style callout shapes without using the dlls that you normally would... in other words, paths, and very cool hand-drawn looks on some too... very cool, Michael! Showcasing Cinch MVVM framework / PRISM 4 interoperability Sacha Barber has a post up on CodeProject that demonstratest using Cinch and Prism4 together... handily using MEF since Cinch relies on MEFedMVVM... this is a heck of a post... lots of code, lots of explanations. PathListBox: Text on the path Alex Knight keeps making this PathListBox series better ... this time he is putting text on the path... moving text... too cool, Alex! Windows Phone 7: Pinch Gesture Sample Peter Kuhn digs into the WP7 toolkit and examines GestureListener, pinch events, and clipping... examples and code supplied. How to change the StartPage of the Windows Phone 7 Application in Visual Studio 2010 ? Senthil Kumar discusses how to change the StartPage of your WP7 app, or get the program running if you happen to move or rename MainPage.xaml WP7 Text Boxes – OnEnter (my 1st Behaviour) Mike Hole has a post up about the issue with the keyboard appearing in front of the textbox, and maybe using the enter key to drop it... and he's developed a behavior for that process. WP7 ContextMenu in depth | Part1: key concepts and API WindowsPhoneGeek has some good articles that I haven't posted, but I'll catch up. This one is a nice tutorial on the WP7 Context menu... good explanation, diagrams, and code. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

    Read the article

  • fabric deploy problem

    - by alexarsh
    Hi, I'm trying to deploy a django app with fabric and get the following error: Alexs-MacBook:fabric alex$ fab config:instance=peergw deploy -H <ip> - u <username> -p <password> [192.168.2.93] run: cat /etc/issue Traceback (most recent call last): File "build/bdist.macosx-10.6-universal/egg/fabric/main.py", line 419, in main File "/Users/alex/Rabota/server/mx30/scripts/fabric/fab/ commands.py", line 37, in deploy checkup() File "/Users/alex/Rabota/server/mx30/scripts/fabric/fab/ commands.py", line 140, in checkup if not 'Ubuntu' in run('cat /etc/issue'): File "build/bdist.macosx-10.6-universal/egg/fabric/network.py", line 382, in host_prompting_wrapper File "build/bdist.macosx-10.6-universal/egg/fabric/operations.py", line 414, in run File "build/bdist.macosx-10.6-universal/egg/fabric/network.py", line 65, in __getitem__ File "build/bdist.macosx-10.6-universal/egg/fabric/network.py", line 140, in connect File "build/bdist.macosx-10.6-universal/egg/paramiko/client.py", line 149, in load_system_host_keys File "build/bdist.macosx-10.6-universal/egg/paramiko/hostkeys.py", line 154, in load File "build/bdist.macosx-10.6-universal/egg/paramiko/hostkeys.py", line 66, in from_line File "build/bdist.macosx-10.6-universal/egg/paramiko/rsakey.py", line 61, in __init__ paramiko.SSHException: Invalid key Alexs-MacBook:fabric alex$ I can't connect to the server via ssh. What can be my problem? Regards, Arshavski Alexander.

    Read the article

  • Hierarchy based aggregation

    - by Ganapathy Subramaniam
    I have a hierarchy table in SQL Server 2005 which contains employees - managers - department - location - state. Sample table for hierarchy table: ID Name ParentID Type 1 PA NULL 0 (group) 2 Pittsburgh 1 1 (subgroup) 3 Accounts 2 1 4 Alex 3 2 (employee) 5 Robin 3 2 6 HR 2 1 7 Robert 6 2 Second one is fact table which contains employee salary details ID and Salary. Sample data for fact table: ID Salary 4 6000 5 5000 7 4000 Is there any good to way to display the hierarchy from hierarchy table with aggregated sum of salary based on employees. Expected result is like Name Salary PA 15000 (Pittsburgh + others(if any)) Pittusburgh 15000 (Accounts + HR) Accounts 11000 (Alex + Robin) Alex 6000 (direct values) Robin 5000 HR 4000 Robert 4000 In my production environment, hierarchy table may contain 23000+ rows and fact table may contain 300,000+ rows. So, I thought of providing any level of groupid to the query to retrieve just its children and its corresponding aggregated value. Any better solution?

    Read the article

  • Why lock-free data structures just aren't lock-free enough

    - by Alex.Davies
    Today's post will explore why the current ways to communicate between threads don't scale, and show you a possible way to build scalable parallel programming on top of shared memory. The problem with shared memory Soon, we will have dozens, hundreds and then millions of cores in our computers. It's inevitable, because individual cores just can't get much faster. At some point, that's going to mean that we have to rethink our architecture entirely, as millions of cores can't all access a shared memory space efficiently. But millions of cores are still a long way off, and in the meantime we'll see machines with dozens of cores, struggling with shared memory. Alex's tip: The best way for an application to make use of that increasing parallel power is to use a concurrency model like actors, that deals with synchronisation issues for you. Then, the maintainer of the actors framework can find the most efficient way to coordinate access to shared memory to allow your actors to pass messages to each other efficiently. At the moment, NAct uses the .NET thread pool and a few locks to marshal messages. It works well on dual and quad core machines, but it won't scale to more cores. Every time we use a lock, our core performs an atomic memory operation (eg. CAS) on a cell of memory representing the lock, so it's sure that no other core can possibly have that lock. This is very fast when the lock isn't contended, but we need to notify all the other cores, in case they held the cell of memory in a cache. As the number of cores increases, the total cost of a lock increases linearly. A lot of work has been done on "lock-free" data structures, which avoid locks by using atomic memory operations directly. These give fairly dramatic performance improvements, particularly on systems with a few (2 to 4) cores. The .NET 4 concurrent collections in System.Collections.Concurrent are mostly lock-free. However, lock-free data structures still don't scale indefinitely, because any use of an atomic memory operation still involves every core in the system. A sync-free data structure Some concurrent data structures are possible to write in a completely synchronization-free way, without using any atomic memory operations. One useful example is a single producer, single consumer (SPSC) queue. It's easy to write a sync-free fixed size SPSC queue using a circular buffer*. Slightly trickier is a queue that grows as needed. You can use a linked list to represent the queue, but if you leave the nodes to be garbage collected once you're done with them, the GC will need to involve all the cores in collecting the finished nodes. Instead, I've implemented a proof of concept inspired by this intel article which reuses the nodes by putting them in a second queue to send back to the producer. * In all these cases, you need to use memory barriers correctly, but these are local to a core, so don't have the same scalability problems as atomic memory operations. Performance tests I tried benchmarking my SPSC queue against the .NET ConcurrentQueue, and against a standard Queue protected by locks. In some ways, this isn't a fair comparison, because both of these support multiple producers and multiple consumers, but I'll come to that later. I started on my dual-core laptop, running a simple test that had one thread producing 64 bit integers, and another consuming them, to measure the pure overhead of the queue. So, nothing very interesting here. Both concurrent collections perform better than the lock-based one as expected, but there's not a lot to choose between the ConcurrentQueue and my SPSC queue. I was a little disappointed, but then, the .NET Framework team spent a lot longer optimising it than I did. So I dug out a more powerful machine that Red Gate's DBA tools team had been using for testing. It is a 6 core Intel i7 machine with hyperthreading, adding up to 12 logical cores. Now the results get more interesting. As I increased the number of producer-consumer pairs to 6 (to saturate all 12 logical cores), the locking approach was slow, and got even slower, as you'd expect. What I didn't expect to be so clear was the drop-off in performance of the lock-free ConcurrentQueue. I could see the machine only using about 20% of available CPU cycles when it should have been saturated. My interpretation is that as all the cores used atomic memory operations to safely access the queue, they ended up spending most of the time notifying each other about cache lines that need invalidating. The sync-free approach scaled perfectly, despite still working via shared memory, which after all, should still be a bottleneck. I can't quite believe that the results are so clear, so if you can think of any other effects that might cause them, please comment! Obviously, this benchmark isn't realistic because we're only measuring the overhead of the queue. Any real workload, even on a machine with 12 cores, would dwarf the overhead, and there'd be no point worrying about this effect. But would that be true on a machine with 100 cores? Still to be solved. The trouble is, you can't build many concurrent algorithms using only an SPSC queue to communicate. In particular, I can't see a way to build something as general purpose as actors on top of just SPSC queues. Fundamentally, an actor needs to be able to receive messages from multiple other actors, which seems to need an MPSC queue. I've been thinking about ways to build a sync-free MPSC queue out of multiple SPSC queues and some kind of sign-up mechanism. Hopefully I'll have something to tell you about soon, but leave a comment if you have any ideas.

    Read the article

  • Ruby on Rails - where to write business logic while processing a request? (newbie)

    - by Genadinik
    I am learning Ruby on Rails. I made a simple link like this: <%= link_to "Alex Link", alexes_path(@alex) %> then I routed it in routes.rb like this: resources :alexes get "home/index" then I am a bit unclear, but I think it goes to this part of the controller: def index #@alexes = Alex.all respond_to do |format| format.html # index.html.erb format.json { render json: @alexes } end end Am I correct that it goes to this part of the controller? Then nothing much happens and it goes to the next page which is index.html.rb under views\alexes So what I am wondering is - if I needed to do some business logic, would I write that in the controller snippet? Where inside the snippet? An example would be nice to take a look. Also, I would like to connect to a MongoDb database. Would I also write that in the middle of the controller? Thanks!

    Read the article

  • Delay of mail delivery - Hosted exchange provider

    - by alex
    Hi, I recently signed up to a new hosted email provider. When I send mail (from OWA, OR Outlook) there is a delay of up to 3 minutes from when i send the message, to when it's received (in my gmail account for example) I've listed the headers below. Is there anything I can advise my new email host to do? My previous email host delivers within 5 seconds!! New email provider: Delivered-To: ****.*****@******.co.uk.test-google-a.com Received: by 10.223.120.148 with SMTP id d20cs333125far; Mon, 30 Nov 2009 08:49:43 -0800 (PST) Received: by 10.213.106.202 with SMTP id y10mr4864870ebo.35.1259599782838; Mon, 30 Nov 2009 08:49:42 -0800 (PST) Return-Path: Received: from relay005.apm-internet.net (relay005.apm-internet.net [85.119.248.8]) by mx.google.com with SMTP id 26si13016480ewy.43.2009.11.30.08.49.42; Mon, 30 Nov 2009 08:49:42 -0800 (PST) Received-SPF: neutral (google.com: 85.119.248.8 is neither permitted nor denied by best guess record for domain of ****@*******.com) client-ip=85.119.248.8; Authentication-Results: mx.google.com; spf=neutral (google.com: 85.119.248.8 is neither permitted nor denied by best guess record for domain of ****@*******.com) smtp.mail=****@*******.com Received: (qmail 63915 invoked from network); 30 Nov 2009 16:49:41 -0000 Received: from unknown (HELO mx-out-manc2.simplymailsolutions.com) (88.151.129.22) by relay005.apm-internet.net with SMTP; 30 Nov 2009 16:49:42 -0000 X-APM-IP: 88.151.129.22 X-APM-Score: 4 Received-SPF: none (relay005.apm-internet.net: domain at alexjamesbrown.com does not designate permitted sender hosts) Received: from [10.1.20.1] (helo=win-s-manc1.shared.ifeltd.com) by mx-out-manc2.simplymailsolutions.com with esmtp (Exim 4.63) (envelope-from ) id 1NF9QZ-0005By-Hw for ****.*****@******.co.uk; Mon, 30 Nov 2009 16:48:46 +0000 Received: from sha-exch8.shared.ifeltd.com ([10.1.20.8]) by win-s-manc1.shared.ifeltd.com with Microsoft SMTPSVC(6.0.3790.3959); Mon, 30 Nov 2009 16:48:34 +0000 Received: from sha-exch9.shared.ifeltd.com ([10.1.20.9]) by sha-exch8.shared.ifeltd.com with Microsoft SMTPSVC(6.0.3790.3959); Mon, 30 Nov 2009 16:48:34 +0000 Received: from SHA-EXCH13.shared.ifeltd.com (10.1.20.13) by sha-exch9.shared.ifeltd.com (10.1.20.9) with Microsoft SMTP Server (TLS) id 8.1.393.1; Mon, 30 Nov 2009 16:48:25 +0000 Received: from SHA-EXCH12.shared.ifeltd.com ([fe80::ecba:36d0:eec5:c928]) by SHA-EXCH13.shared.ifeltd.com ([fe80::212b:916c:70c7:a4e5%11]) with mapi; Mon, 30 Nov 2009 16:48:05 +0000 From: Alex Brown To: "****.*****@*****.co.uk" Date: Mon, 30 Nov 2009 16:48:04 +0000 Subject: testing Thread-Topic: testing Thread-Index: AQHKcdzZg4oiDsOYIEio/7k6bCk8BQ== Message-ID: Accept-Language: en-US, en-GB Content-Language: en-GB X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US, en-GB Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginalArrivalTime: 30 Nov 2009 16:48:34.0235 (UTC) FILETIME=[F48178B0:01CA71DC] Here are the headers using my previous exchange host: Delivered-To: ****.*****@******.co.uk.test-google-a.com Received: by 10.223.120.148 with SMTP id d20cs333076far; Mon, 30 Nov 2009 08:48:35 -0800 (PST) Received: by 10.213.2.70 with SMTP id 6mr4797985ebi.25.1259599715739; Mon, 30 Nov 2009 08:48:35 -0800 (PST) Return-Path: Received: from relay005.apm-internet.net (relay005.apm-internet.net [85.119.248.8]) by mx.google.com with SMTP id 26si13030993ewy.23.2009.11.30.08.48.35; Mon, 30 Nov 2009 08:48:35 -0800 (PST) Received-SPF: neutral (google.com: 85.119.248.8 is neither permitted nor denied by best guess record for domain of ****@*********.com) client-ip=85.119.248.8; Authentication-Results: mx.google.com; spf=neutral (google.com: 85.119.248.8 is neither permitted nor denied by best guess record for domain of ****@*********.com) smtp.mail=****@*********.com Received: (qmail 60920 invoked from network); 30 Nov 2009 16:48:34 -0000 Received: from unknown (HELO MTAb.MsExchange2007.com) (89.31.236.50) by relay005.apm-internet.net with SMTP; 30 Nov 2009 16:48:35 -0000 X-APM-IP: 89.31.236.50 X-APM-Score: 1 Received-SPF: none (relay005.apm-internet.net: domain at alexjamesbrown.com does not designate permitted sender hosts) Received: from EXHUB02.SL.local (no.ptr.hostlogic.biz [89.31.236.28]) by MTAb.MsExchange2007.com (Spam Firewall) with ESMTP id B677A34FE0F for ; Mon, 30 Nov 2009 16:48:33 +0000 (GMT) Received: from EXHUB02.SL.local (no.ptr.hostlogic.biz [89.31.236.28]) by MTAb.MsExchange2007.com with ESMTP id 8X5B8V4tExVzoNyU for ; Mon, 30 Nov 2009 16:48:34 +0000 (GMT) Received: from EXCCR03STORE.SL.local ([10.0.0.2]) by EXHUB02.SL.local ([192.168.92.64]) with mapi; Mon, 30 Nov 2009 16:48:31 +0000 From: Alex James Brown To: "****.*****@******.co.uk" Date: Mon, 30 Nov 2009 16:48:30 +0000 Subject: testing from o Thread-Topic: testing from o Thread-Index: AQHKcdzyY1iBFWiol0ykG6xPQUZiTg== Message-ID: Accept-Language: en-US, en-GB Content-Language: en-GB X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US, en-GB Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0

    Read the article

  • missing bootmanager after win7 installation from external hdd

    - by Alex
    today i tried to install win7 from an external hdd to my system. i tried this tut http://www.pcworld.com/article/165159/install_windows_7_from_an_external_hard_drive.html and everything went fine till i pluged off the external hdd. after i pluged it off and tried to restart the system i get a missing boot manager error. if i plug the external hdd in again it's all working fine again. i've searched for the last 2h and didn't find a good answer. did any of you have one ? regards Alex ps: i already tried any forms of reperation and the system is installed on the correct hdd.

    Read the article

  • Can't connect to a machine via Cisco VPN on Mac

    - by Alex
    Hi there, I have a curious problem. I can connect to work's vpn using Cisco VPN Client. I can get internet through that vpn. When I go check the IP online it tells me the IP address of the server I connected. However, when I try to ping one of the machines at work I get nothing. And traceroute says there is no route to the destination. But works for google. Any ideas? Is some traffic not sent through the VPN on mac Alex

    Read the article

  • Excel (.xls) files not opening in Excel when launched from Explorer

    - by Alex Berry
    I appear to have done something to Excel (2003) whereby whenever I double-click on an Excel file (.xls) in Windows Explorer, Excel launches OK, but the corresponding workbook doesn't open, and I'm left with an instance of Excel with no active workbook, i.e. a grey screen. It was fine earlier on, but now it's goosed. It's clearly not windows file associations, as Excel launches ok. It's a problem specific to Excel itself... Any thoughts what I might have done to give rise to this? Many thanks, Alex.

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >