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  • Connecting to unsecured wireless network

    - by Sanchez
    I would like to know what information is public and can be intercepted in a non-open, but unsecured wireless network. Moreover, is there anything I can do to make it more "secure", other than using https connection whenever possible. In more details, I recently discovered (with surprise) that the wireless network in my school is actually unsecured. Although not everyone can connect to it (you need a student ID), I am told that certain softwares like Wireshark would be able to intercept the data. Since I have been using the network for all private purposes (email, facebook etc), I do feel quite insecure now and would like to understand the situation a bit better. I installed Wireshark and tried to play with it but all I can see are something alien to me. In any case, all I see seems to come directly/indirectly from my IP address, and I have long thought that usually different computers in the same wireless network would be assigned different addresses. Am I wrong? If not, then I feel very confused about what information is actually being captured (potentially by other users in the network, since I don't think I could capture activities of others in the same network anyway), and whether it's safe to use the network at all. (Gambling on others in the same network showing good behaviour is apparently not an option.) Thank you.

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  • 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?

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  • 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.

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  • 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!

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  • 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

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  • 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.

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  • 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

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  • 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.

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  • Dell R910 with Integrated PERC H700 Adapter

    - by Alex
    I am in the process of designing an architecture based around a single Dell R910 server running Windows Server 2008 Enterprise. I would like the server to have 8 RAID1 pairs of spinning disks, so I intend to implement: Dell R910 Server Integrated PERC H700 Adapter with 1 SAS expander on each SAS connector (so 8 expanders in total) 7 RAID1 pairs of 143Gb 15K HDD, each paired on one connector using an expander 1 RAID1 pair of 600Gb 10K HDD, paired on the remaining connector using an expander My main concern is not to introduce bottlenecks in this architecture, and I have the following questions. Will the PERC H700 Adapter act as a bottleneck for disk access? Will using SAS expanders for each RAID1 pair cause a bottleneck or would this be as fast as pairing disks directly attached to the SAS connectors? Can I mix the disks, as long as the disks in each RAID1 pair are the same? I assume so. Can anyone recommend any single-to-double SAS Expanders that are known to function well with the H700? Cheers Alex

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  • Why is systemd not setting my system time?

    - by Alex Chamberlain
    I'm running Arch Linux. Recently, when I turn on my PC, the system time is set to 1:00 1 January 1970 - presumably the 1:00 o'clock is from the timezone shift. Does anyone have any ideas why systemd isn't setting my system time correctly? Some useful output (I think)... [root@alex-desktop network.d]# timedatectl status Local time: Sun 2013-06-09 16:33:04 BST Universal time: Sun 2013-06-09 15:33:04 UTC RTC time: Sun 2013-06-09 15:18:50 Timezone: Europe/London (BST, +0100) NTP enabled: yes NTP synchronized: no RTC in local TZ: no DST active: yes Last DST change: DST began at Sun 2013-03-31 00:59:59 GMT Sun 2013-03-31 02:00:00 BST Next DST change: DST ends (the clock jumps one hour backwards) at Sun 2013-10-27 01:59:59 BST Sun 2013-10-27 01:00:00 GMT

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  • Issue Connecting two home networks

    - by Alex
    Hi, I have a home networking question. I have two DLINK wireless/wired routers in my house, connected to the Internet ISP. There are a 2 computers on each of the two networks. Network1: has 192.168.0.0 (gateway) Valid IP'S range - 192.168.0.1 - 192.168.0.10, with COMP1 having a fixed IP of 162.168.0.1 Network2: has 192.168.0.100 (gateway) Valid IP'S range - 192.168.0.101 - 192.168.0.110 with COMP2 having a static IP of 162.168.0.101, a WIRELESS printer on 192.168.0.102 Both routers have a netmask of 255.255.255.0 My need is to connect the two routers, so that I can Remote desktop for COMP1 to COMP2 and viceversa, and COMP1 to connect to the wireless printer on Network2. can anyone help to set this up so that the both networks can talk to each other. Any help is appreciated. -Alex

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  • Best practice for administering a (hadoop) cluster

    - by Alex
    Dear all, I've recently been playing with Hadoop. I have a six node cluster up and running - with HDFS, and having run a number of MapRed jobs. So far, so good. However I'm now looking to do this more systematically and with a larger number of nodes. Our base system is Ubuntu and the current setup has been administered using apt (to install the correct java runtime) and ssh/scp (to propagate out the various conf files). This is clearly not scalable over time. Does anyone have any experience of good systems for administering (possibly slightly heterogenous: different disk sizes, different numbers of cpus on each node) hadoop clusters automagically? I would consider diskless boot - but imagine that with a large cluster, getting the cluster up and running might be bottle-necked on the machine serving the OS. Or some form of distributed debian apt to keep the machines native environment synchronised? And how do people successfully manage the conf files over a number of (potentially heterogenous) machines? Thanks very much in advance, Alex

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  • DbServerSyncProvider & KnowledgeSyncProvider

    - by Alex
    This question is about the Microsoft Sync Framework. Is it possible to sync a DbServerSyncProvider with a KnowledgeSyncProvider? (SqlCeSyncProvider for example). I have a DbServerSyncProvider that was written a long time ago and I would like to sync it with SqlCeSyncProvider so that I can have peer to peer syncing. Thank you, Alex

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  • Can't click allow button in flash on firefox

    - by Alex
    I have a webapp embedding some flash content in an iframe. The flash part is requesting access to the webcam. On firefox/mac os, user's can't click the allow button. This only happens when the page embedding the swf file is loaded in the iframe, it works fine when laded separately. Has anyone else faced a similar problem? D you know any workarounds? Thanks, Alex

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  • Windows Phone 7 SDK and Visual Studio 2010 RTM

    - by Alex DeLarge
    Hmmm, wonder if I have the first VS 2010 RTM question? Anyway.. Installing the Windows Phone 7 SDK I get the following error Incompatible Products VC 10.0 Runtime .NET Framework 4 Multi-Targeting Pack Microsoft.NET Framework 4 Client Profile Microsoft .NET Framework 4 Extended This was reported as an issue with Beta 2 and the fix was to install the RC. Anyone know why it's incompatible with the RTM? Will we have to wait for an update to the SDK? Regards, Alex..

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  • Example of a Good Func Spec?

    - by Alex
    Hey, I'm writing my func spec, and I was wondering if there are any good samples of a complete and well-written func spec? Like "This is a standard You're supposed to aspire to" type of spec. I know that Joel has a skeleteon of a func spec on his website, but I am looking for something more complete because I'm not of the appropriate amount of detail, formatting, etc. Thanks, Alex

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  • Display pdf within app on android?

    - by alex
    I got very frustrated when I realized that android is not able to display pdfs (in a webview or whatever) out-of-the-box. So my question, are there any (os) jars or classes to display a pdf document within an app? Thx in advance, alex

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  • Missing AVFoundation.framework

    - by Alex
    Hi, AVFoundation.framework is not where the documentation says it should be. I have iPhone SDK 2.2 installed (never had previous sdk versions installed) and I can't find that folder under /System/Library/Frameworks I did find it under /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS2.2.sdk/System/Library/Frameworks/ folder but if I add it from that location, then the compiler can't find the header files. I tried copying the entire AVFoundation.framework folder to /System/Library/Framework, but it still can't find the header files. How can I use AVFoundation classes? Thanks, Alex

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  • eclipse serveral ant build file

    - by Alex
    Hi, currently I'm developing in eclipse 3.5 in different project web applications for tomcat 6.0.24. For each of this project I have written a ant build file to generate the war file to deploy the project to the tomcat container. So I have to run for each project the ant build file (a lot of clicks, and a waste of time). Question: Is there a possibility to run all needed ant build files with a single click, from a single project or whatever? Best regards, Alex

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  • JQuery: Accessing Post parameters

    - by Alex
    Just started with JQuery and I've managed to pass a parameter using POST, firebug confirms this: Parameters link [email protected] Source link=test1%40test.com I don't know how to access the link parameter from the receiving page using JQuery, it must be so simple but everything I've been searching through (jquery website, SO, etc) mentions everything but this. Thanks, Alex

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