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• virturalmin webmin dose not respond

  - by Miranda

  I have installed Virtualmin on a CentOS remote server, but it dose not seem to work https://115.146.95.118:10000/ at least the Webmin page dose not work. I have opened those ports http ALLOW 80:80 from 0.0.0.0/0 ALLOW 443:443 from 0.0.0.0/0 ssh ALLOW 22:22 from 0.0.0.0/0 virtualmin ALLOW 20000:20000 from 0.0.0.0/0 ALLOW 10000:10009 from 0.0.0.0/0 And restarting Webmin dose not solve it: /etc/rc.d/init.d/webmin restart Stopping Webmin server in /usr/libexec/webmin Starting Webmin server in /usr/libexec/webmin And I have tried to use Amazon EC2 this time, still couldn't get it to work. http://ec2-67-202-21-21.compute-1.amazonaws.com:10000/ [ec2-user@ip-10-118-239-13 ~]$ netstat -an | grep :10000 tcp 0 0 0.0.0.0:10000 0.0.0.0:* LISTEN udp 0 0 0.0.0.0:10000 0.0.0.0:* [ec2-user@ip-10-118-239-13 ~]$ sudo iptables -L -n Chain INPUT (policy ACCEPT) target prot opt source destination ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:20 ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:21 ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:53 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:20000 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:10000 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:443 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:993 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:143 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:995 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:110 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:20 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:21 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:53 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:587 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:25 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:22 Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination Since I need more than 10 reputation to post image, you can find the screenshots of the security group setting at the Webmin Support Forum. I have tried: sudo iptables -A INPUT -p tcp -m tcp --dport 10000 -j ACCEPT It did not change anything. [ec2-user@ip-10-118-239-13 ~]$ sudo yum install openssl perl-Net-SSLeay perl-Crypt-SSLeay Loaded plugins: fastestmirror, priorities, security, update-motd Loading mirror speeds from cached hostfile * amzn-main: packages.us-east-1.amazonaws.com * amzn-updates: packages.us-east-1.amazonaws.com amzn-main | 2.1 kB 00:00 amzn-updates | 2.3 kB 00:00 Setting up Install Process Package openssl-1.0.0j-1.43.amzn1.i686 already installed and latest version Package perl-Net-SSLeay-1.35-9.4.amzn1.i686 already installed and latest version Package perl-Crypt-SSLeay-0.57-16.4.amzn1.i686 already installed and latest version Nothing to do [ec2-user@ip-10-118-239-13 ~]$ nano /etc/webmin/miniserv.conf GNU nano 2.0.9 File: /etc/webmin/miniserv.conf port=10000 root=/usr/libexec/webmin mimetypes=/usr/libexec/webmin/mime.types addtype_cgi=internal/cgi realm=Webmin Server logfile=/var/webmin/miniserv.log errorlog=/var/webmin/miniserv.error pidfile=/var/webmin/miniserv.pid logtime=168 ppath= ssl=1 env_WEBMIN_CONFIG=/etc/webmin env_WEBMIN_VAR=/var/webmin atboot=1 logout=/etc/webmin/logout-flag listen=10000 denyfile=\.pl$ log=1 blockhost_failures=5 blockhost_time=60 syslog=1 session=1 server=MiniServ/1.585 userfile=/etc/webmin/miniserv.users keyfile=/etc/webmin/miniserv.pem passwd_file=/etc/shadow passwd_uindex=0 passwd_pindex=1 passwd_cindex=2 passwd_mindex=4 passwd_mode=0 preroot=virtual-server-theme passdelay=1 sessiononly=/virtual-server/remote.cgi preload= mobile_preroot=virtual-server-mobile mobile_prefixes=m. mobile. anonymous=/virtualmin-mailman/unauthenticated=anonymous ssl_cipher_list=ECDHE-RSA-AES256-SHA384:AES256-SHA256:AES256-SHA256:RC4:HIGH:MEDIUM:+TLSv1:!MD5:!SSLv2:+SSLv3:!ADH:!aNULL:!eNULL:!NULL:!DH:!ADH:!EDH:!AESGCM

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• Auth-Type :- Reject in RADIUS users file matches inner tunnel request but sends Access-Accept

  - by mgorven

  I have WPA2 802.11x EAP authentication setup using FreeRADIUS 2.1.8 on Ubuntu 10.04.4 talking to OpenLDAP, and can successfully authenticate using PEAP/MSCHAPv2, TTLS/MSCHAPv2 and TTLS/PAP (both via the AP and using eapol_test). I am now trying to restrict access to specific SSIDs based on the LDAP groups which the user belongs to. I have configured group membership checking in /etc/freeradius/modules/ldap like so: groupname_attribute = cn groupmembership_filter = "(|(&(objectClass=posixGroup)(memberUid=%{User-Name}))(&(objectClass=posixGroup)(uniquemember=%{User-Name})))" and I have configured extraction of the SSID from Called-Station-Id into Called-Station-SSID based on the Mac Auth wiki page. In /etc/freeradius/eap.conf I have enabled copying attributes from the outer tunnel into the inner tunnel, and usage of the inner tunnel response in the outer tunnel (for both PEAP and TTLS). I had the same behaviour before changing these options however. copy_request_to_tunnel = yes use_tunneled_reply = yes I'm running eapol_test like this to test the setup: eapol_test -c peap-mschapv2.conf -a 172.16.0.16 -s testing123 -N 30:s:01-23-45-67-89-01:Example-EAP with the following peap-mschapv2.conf file: network={ ssid="Example-EAP" key_mgmt=WPA-EAP eap=PEAP identity="mgorven" anonymous_identity="anonymous" password="foobar" phase2="autheap=MSCHAPV2" } With the following in /etc/freeradius/users: DEFAULT Ldap-Group == "employees" and running freeradius-Xx, I can see that the LDAP group retrieval works, and that the SSID is extracted. Debug: [ldap] performing search in dc=example,dc=com, with filter (&(cn=employees)(|(&(objectClass=posixGroup)(memberUid=mgorven))(&(objectClass=posixGroup)(uniquemember=mgorven)))) Debug: rlm_ldap::ldap_groupcmp: User found in group employees ... Info: expand: %{7} -> Example-EAP Next I try to only allow access to users in the employees group (regardless of SSID), so I put the following in /etc/freeradius/users: DEFAULT Ldap-Group == "employees" DEFAULT Auth-Type := Reject But this immediately rejects the Access-Request in the outer tunnel because the anonymous user is not in the employees group. So I modify it to only match inner tunnel requests like so: DEFAULT Ldap-Group == "employees" DEFAULT FreeRADIUS-Proxied-To == "127.0.0.1" Auth-Type := Reject, Reply-Message = "User does not belong to any groups which may access this SSID." Now users which are in the employees group are authenticated, but so are users which are not in the employees group. I see the reject entry being matched, and the Reply-Message is set, but the client receives an Access-Accept. Debug: rlm_ldap::ldap_groupcmp: Group employees not found or user is not a member. Info: [files] users: Matched entry DEFAULT at line 209 Info: ++[files] returns ok ... Auth: Login OK: [mgorven] (from client test port 0 cli 02-00-00-00-00-01 via TLS tunnel) Info: WARNING: Empty section. Using default return values. ... Info: [peap] Got tunneled reply code 2 Auth-Type := Reject Reply-Message = "User does not belong to any groups which may access this SSID." ... Info: [peap] Got tunneled reply RADIUS code 2 Auth-Type := Reject Reply-Message = "User does not belong to any groups which may access this SSID." ... Info: [peap] Tunneled authentication was successful. Info: [peap] SUCCESS Info: [peap] Saving tunneled attributes for later ... Sending Access-Accept of id 11 to 172.16.2.44 port 60746 Reply-Message = "User does not belong to any groups which may access this SSID." User-Name = "mgorven" and eapol_test reports: RADIUS message: code=2 (Access-Accept) identifier=11 length=233 Attribute 18 (Reply-Message) length=64 Value: 'User does not belong to any groups which may access this SSID.' Attribute 1 (User-Name) length=9 Value: 'mgorven' ... SUCCESS Why isn't the request being rejected, and is this the right way to implement this?

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• iPhone doesn't save password for Cisco IPsec VPN using racoon daemon

  - by dsx

  On my Debian server I had set up racoon daemon (1:0.8.0-14) for Cisco IPSec VPN using certificates for authentication. My racoon.conf is like following: log info; path certificate "/etc/racoon/certs"; listen { isakmp $SERVER_IP_HERE [500]; isakmp_natt $SERVER_IP_HERE [4500]; } timer { natt_keepalive 10 sec; } remote anonymous { lifetime time 24 hours; proposal_check obey; passive on; exchange_mode aggressive,main; my_identifier asn1dn; peers_identifier asn1dn; verify_identifier on; certificate_type x509 "cert_name.crt" "key_name.key"; ca_type x509 "ca.crt"; mode_cfg on; verify_cert on; ike_frag on; generate_policy on; nat_traversal on; dpd_delay 20; proposal { encryption_algorithm aes; hash_algorithm sha1; authentication_method xauth_rsa_server; dh_group modp1024; } } mode_cfg { conf_source local; auth_source system; auth_throttle 3; save_passwd on; dns4 8.8.8.8; network4 $SOME_LAN_SUBNET; netmask4 255.255.255.0; pool_size 128; } sainfo anonymous { pfs_group 2; lifetime time 24 hour; encryption_algorithm aes; authentication_algorithm hmac_sha1; compression_algorithm deflate; } I'm not using PSK authentication here. Using iPhone configuration utility I had uploaded all required certificates to iPhone and set up VPN on demand. Everything works just fine except one thing: iPhone refuses to save VPN password regardless of save_passwd on; in racoon configuration file. As opposed to iPhone behaviour, Mac OS X 10.8.2 have no problems saving password. I had examined iPhone log file and found following: racoon[151] <Notice>: >>>>> phase change status = phase 1 established configd[50] <Notice>: IPSec Network Configuration started. configd[50] <Notice>: IPSec Network Configuration: INTERNAL-IP4-ADDRESS = $SUBNET_IP_HERE. configd[50] <Notice>: IPSec Network Configuration: INTERNAL-IP4-MASK = 255.255.255.0. configd[50] <Notice>: IPSec Network Configuration: SAVE-PASSWORD = 0. configd[50] <Notice>: IPSec Network Configuration: INTERNAL-IP4-DNS = 8.8.8.8. configd[50] <Notice>: IPSec Network Configuration: BANNER = . configd[50] <Notice>: IPSec Network Configuration: DEF-DOMAIN = . configd[50] <Notice>: IPSec Network Configuration: DEFAULT-ROUTE = local-address $SUBNET_IP_HERE/32. configd[50] <Notice>: IPSec Phase2 starting. configd[50] <Notice>: IPSec Network Configuration established. configd[50] <Notice>: IPSec Phase1 established. Please note IPSec Network Configuration message containing SAVE-PASSWORD = 0.. Is it a bug in racoon daemon on server, or iPhone (iOS version is 6.0.1 (10A523)) or it is me missing something? How to make iPhone remember IPSec VPN password?

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• Using LINQ Distinct: With an Example on ASP.NET MVC SelectListItem

  - by Joe Mayo

  One of the things that might be surprising in the LINQ Distinct standard query operator is that it doesn’t automatically work properly on custom classes. There are reasons for this, which I’ll explain shortly. The example I’ll use in this post focuses on pulling a unique list of names to load into a drop-down list. I’ll explain the sample application, show you typical first shot at Distinct, explain why it won’t work as you expect, and then demonstrate a solution to make Distinct work with any custom class. The technologies I’m using are  LINQ to Twitter, LINQ to Objects, Telerik Extensions for ASP.NET MVC, ASP.NET MVC 2, and Visual Studio 2010. The function of the example program is to show a list of people that I follow.  In Twitter API vernacular, these people are called “Friends”; though I’ve never met most of them in real life. This is part of the ubiquitous language of social networking, and Twitter in particular, so you’ll see my objects named accordingly. Where Distinct comes into play is because I want to have a drop-down list with the names of the friends appearing in the list. Some friends are quite verbose, which means I can’t just extract names from each tweet and populate the drop-down; otherwise, I would end up with many duplicate names. Therefore, Distinct is the appropriate operator to eliminate the extra entries from my friends who tend to be enthusiastic tweeters. The sample doesn’t do anything with the drop-down list and I leave that up to imagination for what it’s practical purpose could be; perhaps a filter for the list if I only want to see a certain person’s tweets or maybe a quick list that I plan to combine with a TextBox and Button to reply to a friend. When the program runs, you’ll need to authenticate with Twitter, because I’m using OAuth (DotNetOpenAuth), for authentication, and then you’ll see the drop-down list of names above the grid with the most recent tweets from friends. Here’s what the application looks like when it runs: As you can see, there is a drop-down list above the grid. The drop-down list is where most of the focus of this article will be. There is some description of the code before we talk about the Distinct operator, but we’ll get there soon. This is an ASP.NET MVC2 application, written with VS 2010. Here’s the View that produces this screen: <%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<TwitterFriendsViewModel>" %> <%@ Import Namespace="DistinctSelectList.Models" %> <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">     Home Page </asp:Content><asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">     <fieldset>         <legend>Twitter Friends</legend>         <div>             <%= Html.DropDownListFor(                     twendVM => twendVM.FriendNames,                     Model.FriendNames,                     "<All Friends>") %>         </div>         <div>             <% Html.Telerik().Grid<TweetViewModel>(Model.Tweets)                    .Name("TwitterFriendsGrid")                    .Columns(cols =>                     {                         cols.Template(col =>                             { %>                                 <img src="<%= col.ImageUrl %>"                                      alt="<%= col.ScreenName %>" />                         <% });                         cols.Bound(col => col.ScreenName);                         cols.Bound(col => col.Tweet);                     })                    .Render(); %>         </div>     </fieldset> </asp:Content> As shown above, the Grid is from Telerik’s Extensions for ASP.NET MVC. The first column is a template that renders the user’s Avatar from a URL provided by the Twitter query. Both the Grid and DropDownListFor display properties that are collections from a TwitterFriendsViewModel class, shown below: using System.Collections.Generic; using System.Web.Mvc; namespace DistinctSelectList.Models { /// /// For finding friend info on screen /// public class TwitterFriendsViewModel { /// /// Display names of friends in drop-down list /// public List FriendNames { get; set; } /// /// Display tweets in grid /// public List Tweets { get; set; } } } I created the TwitterFreindsViewModel. The two Lists are what the View consumes to populate the DropDownListFor and Grid. Notice that FriendNames is a List of SelectListItem, which is an MVC class. Another custom class I created is the TweetViewModel (the type of the Tweets List), shown below: namespace DistinctSelectList.Models { /// /// Info on friend tweets /// public class TweetViewModel { /// /// User's avatar /// public string ImageUrl { get; set; } /// /// User's Twitter name /// public string ScreenName { get; set; } /// /// Text containing user's tweet /// public string Tweet { get; set; } } } The initial Twitter query returns much more information than we need for our purposes and this a special class for displaying info in the View.  Now you know about the View and how it’s constructed. Let’s look at the controller next. The controller for this demo performs authentication, data retrieval, data manipulation, and view selection. I’ll skip the description of the authentication because it’s a normal part of using OAuth with LINQ to Twitter. Instead, we’ll drill down and focus on the Distinct operator. However, I’ll show you the entire controller, below,  so that you can see how it all fits together: using System.Linq; using System.Web.Mvc; using DistinctSelectList.Models; using LinqToTwitter; namespace DistinctSelectList.Controllers { [HandleError] public class HomeController : Controller { private MvcOAuthAuthorization auth; private TwitterContext twitterCtx; /// /// Display a list of friends current tweets /// /// public ActionResult Index() { auth = new MvcOAuthAuthorization(InMemoryTokenManager.Instance, InMemoryTokenManager.AccessToken); string accessToken = auth.CompleteAuthorize(); if (accessToken != null) { InMemoryTokenManager.AccessToken = accessToken; } if (auth.CachedCredentialsAvailable) { auth.SignOn(); } else { return auth.BeginAuthorize(); } twitterCtx = new TwitterContext(auth); var friendTweets = (from tweet in twitterCtx.Status where tweet.Type == StatusType.Friends select new TweetViewModel { ImageUrl = tweet.User.ProfileImageUrl, ScreenName = tweet.User.Identifier.ScreenName, Tweet = tweet.Text }) .ToList(); var friendNames = (from tweet in friendTweets select new SelectListItem { Text = tweet.ScreenName, Value = tweet.ScreenName }) .Distinct() .ToList(); var twendsVM = new TwitterFriendsViewModel { Tweets = friendTweets, FriendNames = friendNames }; return View(twendsVM); } public ActionResult About() { return View(); } } } The important part of the listing above are the LINQ to Twitter queries for friendTweets and friendNames. Both of these results are used in the subsequent population of the twendsVM instance that is passed to the view. Let’s dissect these two statements for clarification and focus on what is happening with Distinct. The query for friendTweets gets a list of the 20 most recent tweets (as specified by the Twitter API for friend queries) and performs a projection into the custom TweetViewModel class, repeated below for your convenience: var friendTweets = (from tweet in twitterCtx.Status where tweet.Type == StatusType.Friends select new TweetViewModel { ImageUrl = tweet.User.ProfileImageUrl, ScreenName = tweet.User.Identifier.ScreenName, Tweet = tweet.Text }) .ToList(); The LINQ to Twitter query above simplifies what we need to work with in the View and the reduces the amount of information we have to look at in subsequent queries. Given the friendTweets above, the next query performs another projection into an MVC SelectListItem, which is required for binding to the DropDownList.  This brings us to the focus of this blog post, writing a correct query that uses the Distinct operator. The query below uses LINQ to Objects, querying the friendTweets collection to get friendNames: var friendNames = (from tweet in friendTweets select new SelectListItem { Text = tweet.ScreenName, Value = tweet.ScreenName }) .Distinct() .ToList(); The above implementation of Distinct seems normal, but it is deceptively incorrect. After running the query above, by executing the application, you’ll notice that the drop-down list contains many duplicates.  This will send you back to the code scratching your head, but there’s a reason why this happens. To understand the problem, we must examine how Distinct works in LINQ to Objects. Distinct has two overloads: one without parameters, as shown above, and another that takes a parameter of type IEqualityComparer<T>.  In the case above, no parameters, Distinct will call EqualityComparer<T>.Default behind the scenes to make comparisons as it iterates through the list. You don’t have problems with the built-in types, such as string, int, DateTime, etc, because they all implement IEquatable<T>. However, many .NET Framework classes, such as SelectListItem, don’t implement IEquatable<T>. So, what happens is that EqualityComparer<T>.Default results in a call to Object.Equals, which performs reference equality on reference type objects.  You don’t have this problem with value types because the default implementation of Object.Equals is bitwise equality. However, most of your projections that use Distinct are on classes, just like the SelectListItem used in this demo application. So, the reason why Distinct didn’t produce the results we wanted was because we used a type that doesn’t define its own equality and Distinct used the default reference equality. This resulted in all objects being included in the results because they are all separate instances in memory with unique references. As you might have guessed, the solution to the problem is to use the second overload of Distinct that accepts an IEqualityComparer<T> instance. If you were projecting into your own custom type, you could make that type implement IEqualityComparer<T>, but SelectListItem belongs to the .NET Framework Class Library.  Therefore, the solution is to create a custom type to implement IEqualityComparer<T>, as in the SelectListItemComparer class, shown below: using System.Collections.Generic; using System.Web.Mvc; namespace DistinctSelectList.Models { public class SelectListItemComparer : EqualityComparer { public override bool Equals(SelectListItem x, SelectListItem y) { return x.Value.Equals(y.Value); } public override int GetHashCode(SelectListItem obj) { return obj.Value.GetHashCode(); } } } The SelectListItemComparer class above doesn’t implement IEqualityComparer<SelectListItem>, but rather derives from EqualityComparer<SelectListItem>. Microsoft recommends this approach for consistency with the behavior of generic collection classes. However, if your custom type already derives from a base class, go ahead and implement IEqualityComparer<T>, which will still work. EqualityComparer is an abstract class, that implements IEqualityComparer<T> with Equals and GetHashCode abstract methods. For the purposes of this application, the SelectListItem.Value property is sufficient to determine if two items are equal.   Since SelectListItem.Value is type string, the code delegates equality to the string class. The code also delegates the GetHashCode operation to the string class.You might have other criteria in your own object and would need to define what it means for your object to be equal. Now that we have an IEqualityComparer<SelectListItem>, let’s fix the problem. The code below modifies the query where we want distinct values: var friendNames = (from tweet in friendTweets select new SelectListItem { Text = tweet.ScreenName, Value = tweet.ScreenName }) .Distinct(new SelectListItemComparer()) .ToList(); Notice how the code above passes a new instance of SelectListItemComparer as the parameter to the Distinct operator. Now, when you run the application, the drop-down list will behave as you expect, showing only a unique set of names. In addition to Distinct, other LINQ Standard Query Operators have overloads that accept IEqualityComparer<T>’s, You can use the same techniques as shown here, with SelectListItemComparer, with those other operators as well. Now you know how to resolve problems with getting Distinct to work properly and also have a way to fix problems with other operators that require equality comparisons. @JoeMayo

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• Parallelism in .NET – Part 4, Imperative Data Parallelism: Aggregation

  - by Reed

  In the article on simple data parallelism, I described how to perform an operation on an entire collection of elements in parallel.  Often, this is not adequate, as the parallel operation is going to be performing some form of aggregation. Simple examples of this might include taking the sum of the results of processing a function on each element in the collection, or finding the minimum of the collection given some criteria.  This can be done using the techniques described in simple data parallelism, however, special care needs to be taken into account to synchronize the shared data appropriately.  The Task Parallel Library has tools to assist in this synchronization. The main issue with aggregation when parallelizing a routine is that you need to handle synchronization of data.  Since multiple threads will need to write to a shared portion of data.  Suppose, for example, that we wanted to parallelize a simple loop that looked for the minimum value within a dataset: double min = double.MaxValue; foreach(var item in collection) { double value = item.PerformComputation(); min = System.Math.Min(min, value); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This seems like a good candidate for parallelization, but there is a problem here.  If we just wrap this into a call to Parallel.ForEach, we’ll introduce a critical race condition, and get the wrong answer.  Let’s look at what happens here: // Buggy code! Do not use! double min = double.MaxValue; Parallel.ForEach(collection, item => { double value = item.PerformComputation(); min = System.Math.Min(min, value); }); This code has a fatal flaw: min will be checked, then set, by multiple threads simultaneously.  Two threads may perform the check at the same time, and set the wrong value for min.  Say we get a value of 1 in thread 1, and a value of 2 in thread 2, and these two elements are the first two to run.  If both hit the min check line at the same time, both will determine that min should change, to 1 and 2 respectively.  If element 1 happens to set the variable first, then element 2 sets the min variable, we’ll detect a min value of 2 instead of 1.  This can lead to wrong answers. Unfortunately, fixing this, with the Parallel.ForEach call we’re using, would require adding locking.  We would need to rewrite this like: // Safe, but slow double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach(collection, item => { double value = item.PerformComputation(); lock(syncObject) min = System.Math.Min(min, value); }); This will potentially add a huge amount of overhead to our calculation.  Since we can potentially block while waiting on the lock for every single iteration, we will most likely slow this down to where it is actually quite a bit slower than our serial implementation.  The problem is the lock statement – any time you use lock(object), you’re almost assuring reduced performance in a parallel situation.  This leads to two observations I’ll make: When parallelizing a routine, try to avoid locks. That being said: Always add any and all required synchronization to avoid race conditions. These two observations tend to be opposing forces – we often need to synchronize our algorithms, but we also want to avoid the synchronization when possible.  Looking at our routine, there is no way to directly avoid this lock, since each element is potentially being run on a separate thread, and this lock is necessary in order for our routine to function correctly every time. However, this isn’t the only way to design this routine to implement this algorithm.  Realize that, although our collection may have thousands or even millions of elements, we have a limited number of Processing Elements (PE).  Processing Element is the standard term for a hardware element which can process and execute instructions.  This typically is a core in your processor, but many modern systems have multiple hardware execution threads per core.  The Task Parallel Library will not execute the work for each item in the collection as a separate work item. Instead, when Parallel.ForEach executes, it will partition the collection into larger “chunks” which get processed on different threads via the ThreadPool.  This helps reduce the threading overhead, and help the overall speed.  In general, the Parallel class will only use one thread per PE in the system. Given the fact that there are typically fewer threads than work items, we can rethink our algorithm design.  We can parallelize our algorithm more effectively by approaching it differently.  Because the basic aggregation we are doing here (Min) is communitive, we do not need to perform this in a given order.  We knew this to be true already – otherwise, we wouldn’t have been able to parallelize this routine in the first place.  With this in mind, we can treat each thread’s work independently, allowing each thread to serially process many elements with no locking, then, after all the threads are complete, “merge” together the results. This can be accomplished via a different set of overloads in the Parallel class: Parallel.ForEach<TSource,TLocal>.  The idea behind these overloads is to allow each thread to begin by initializing some local state (TLocal).  The thread will then process an entire set of items in the source collection, providing that state to the delegate which processes an individual item.  Finally, at the end, a separate delegate is run which allows you to handle merging that local state into your final results. To rewriting our routine using Parallel.ForEach<TSource,TLocal>, we need to provide three delegates instead of one.  The most basic version of this function is declared as: public static ParallelLoopResult ForEach<TSource, TLocal>( IEnumerable<TSource> source, Func<TLocal> localInit, Func<TSource, ParallelLoopState, TLocal, TLocal> body, Action<TLocal> localFinally ) The first delegate (the localInit argument) is defined as Func<TLocal>.  This delegate initializes our local state.  It should return some object we can use to track the results of a single thread’s operations. The second delegate (the body argument) is where our main processing occurs, although now, instead of being an Action<T>, we actually provide a Func<TSource, ParallelLoopState, TLocal, TLocal> delegate.  This delegate will receive three arguments: our original element from the collection (TSource), a ParallelLoopState which we can use for early termination, and the instance of our local state we created (TLocal).  It should do whatever processing you wish to occur per element, then return the value of the local state after processing is completed. The third delegate (the localFinally argument) is defined as Action<TLocal>.  This delegate is passed our local state after it’s been processed by all of the elements this thread will handle.  This is where you can merge your final results together.  This may require synchronization, but now, instead of synchronizing once per element (potentially millions of times), you’ll only have to synchronize once per thread, which is an ideal situation. Now that I’ve explained how this works, lets look at the code: // Safe, and fast! double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach( collection, // First, we provide a local state initialization delegate. () => double.MaxValue, // Next, we supply the body, which takes the original item, loop state, // and local state, and returns a new local state (item, loopState, localState) => { double value = item.PerformComputation(); return System.Math.Min(localState, value); }, // Finally, we provide an Action<TLocal>, to "merge" results together localState => { // This requires locking, but it's only once per used thread lock(syncObj) min = System.Math.Min(min, localState); } ); Although this is a bit more complicated than the previous version, it is now both thread-safe, and has minimal locking.  This same approach can be used by Parallel.For, although now, it’s Parallel.For<TLocal>.  When working with Parallel.For<TLocal>, you use the same triplet of delegates, with the same purpose and results. Also, many times, you can completely avoid locking by using a method of the Interlocked class to perform the final aggregation in an atomic operation.  The MSDN example demonstrating this same technique using Parallel.For uses the Interlocked class instead of a lock, since they are doing a sum operation on a long variable, which is possible via Interlocked.Add. By taking advantage of local state, we can use the Parallel class methods to parallelize algorithms such as aggregation, which, at first, may seem like poor candidates for parallelization.  Doing so requires careful consideration, and often requires a slight redesign of the algorithm, but the performance gains can be significant if handled in a way to avoid excessive synchronization.

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• Parallelism in .NET – Part 11, Divide and Conquer via Parallel.Invoke

  - by Reed

  Many algorithms are easily written to work via recursion.  For example, most data-oriented tasks where a tree of data must be processed are much more easily handled by starting at the root, and recursively “walking” the tree.  Some algorithms work this way on flat data structures, such as arrays, as well.  This is a form of divide and conquer: an algorithm design which is based around breaking up a set of work recursively, “dividing” the total work in each recursive step, and “conquering” the work when the remaining work is small enough to be solved easily. Recursive algorithms, especially ones based on a form of divide and conquer, are often a very good candidate for parallelization. This is apparent from a common sense standpoint.  Since we’re dividing up the total work in the algorithm, we have an obvious, built-in partitioning scheme.  Once partitioned, the data can be worked upon independently, so there is good, clean isolation of data. Implementing this type of algorithm is fairly simple.  The Parallel class in .NET 4 includes a method suited for this type of operation: Parallel.Invoke.  This method works by taking any number of delegates defined as an Action, and operating them all in parallel.  The method returns when every delegate has completed: Parallel.Invoke( () => { Console.WriteLine("Action 1 executing in thread {0}", Thread.CurrentThread.ManagedThreadId); }, () => { Console.WriteLine("Action 2 executing in thread {0}", Thread.CurrentThread.ManagedThreadId); }, () => { Console.WriteLine("Action 3 executing in thread {0}", Thread.CurrentThread.ManagedThreadId); } ); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Running this simple example demonstrates the ease of using this method.  For example, on my system, I get three separate thread IDs when running the above code.  By allowing any number of delegates to be executed directly, concurrently, the Parallel.Invoke method provides us an easy way to parallelize any algorithm based on divide and conquer.  We can divide our work in each step, and execute each task in parallel, recursively. For example, suppose we wanted to implement our own quicksort routine.  The quicksort algorithm can be designed based on divide and conquer.  In each iteration, we pick a pivot point, and use that to partition the total array.  We swap the elements around the pivot, then recursively sort the lists on each side of the pivot.  For example, let’s look at this simple, sequential implementation of quicksort: public static void QuickSort<T>(T[] array) where T : IComparable<T> { QuickSortInternal(array, 0, array.Length - 1); } private static void QuickSortInternal<T>(T[] array, int left, int right) where T : IComparable<T> { if (left >= right) { return; } SwapElements(array, left, (left + right) / 2); int last = left; for (int current = left + 1; current <= right; ++current) { if (array[current].CompareTo(array[left]) < 0) { ++last; SwapElements(array, last, current); } } SwapElements(array, left, last); QuickSortInternal(array, left, last - 1); QuickSortInternal(array, last + 1, right); } static void SwapElements<T>(T[] array, int i, int j) { T temp = array[i]; array[i] = array[j]; array[j] = temp; } Here, we implement the quicksort algorithm in a very common, divide and conquer approach.  Running this against the built-in Array.Sort routine shows that we get the exact same answers (although the framework’s sort routine is slightly faster).  On my system, for example, I can use framework’s sort to sort ten million random doubles in about 7.3s, and this implementation takes about 9.3s on average. Looking at this routine, though, there is a clear opportunity to parallelize.  At the end of QuickSortInternal, we recursively call into QuickSortInternal with each partition of the array after the pivot is chosen.  This can be rewritten to use Parallel.Invoke by simply changing it to: // Code above is unchanged... SwapElements(array, left, last); Parallel.Invoke( () => QuickSortInternal(array, left, last - 1), () => QuickSortInternal(array, last + 1, right) ); } This routine will now run in parallel.  When executing, we now see the CPU usage across all cores spike while it executes.  However, there is a significant problem here – by parallelizing this routine, we took it from an execution time of 9.3s to an execution time of approximately 14 seconds!  We’re using more resources as seen in the CPU usage, but the overall result is a dramatic slowdown in overall processing time. This occurs because parallelization adds overhead.  Each time we split this array, we spawn two new tasks to parallelize this algorithm!  This is far, far too many tasks for our cores to operate upon at a single time.  In effect, we’re “over-parallelizing” this routine.  This is a common problem when working with divide and conquer algorithms, and leads to an important observation: When parallelizing a recursive routine, take special care not to add more tasks than necessary to fully utilize your system. This can be done with a few different approaches, in this case.  Typically, the way to handle this is to stop parallelizing the routine at a certain point, and revert back to the serial approach.  Since the first few recursions will all still be parallelized, our “deeper” recursive tasks will be running in parallel, and can take full advantage of the machine.  This also dramatically reduces the overhead added by parallelizing, since we’re only adding overhead for the first few recursive calls.  There are two basic approaches we can take here.  The first approach would be to look at the total work size, and if it’s smaller than a specific threshold, revert to our serial implementation.  In this case, we could just check right-left, and if it’s under a threshold, call the methods directly instead of using Parallel.Invoke. The second approach is to track how “deep” in the “tree” we are currently at, and if we are below some number of levels, stop parallelizing.  This approach is a more general-purpose approach, since it works on routines which parse trees as well as routines working off of a single array, but may not work as well if a poor partitioning strategy is chosen or the tree is not balanced evenly. This can be written very easily.  If we pass a maxDepth parameter into our internal routine, we can restrict the amount of times we parallelize by changing the recursive call to: // Code above is unchanged... SwapElements(array, left, last); if (maxDepth < 1) { QuickSortInternal(array, left, last - 1, maxDepth); QuickSortInternal(array, last + 1, right, maxDepth); } else { --maxDepth; Parallel.Invoke( () => QuickSortInternal(array, left, last - 1, maxDepth), () => QuickSortInternal(array, last + 1, right, maxDepth)); } We no longer allow this to parallelize indefinitely – only to a specific depth, at which time we revert to a serial implementation.  By starting the routine with a maxDepth equal to Environment.ProcessorCount, we can restrict the total amount of parallel operations significantly, but still provide adequate work for each processing core. With this final change, my timings are much better.  On average, I get the following timings: Framework via Array.Sort: 7.3 seconds Serial Quicksort Implementation: 9.3 seconds Naive Parallel Implementation: 14 seconds Parallel Implementation Restricting Depth: 4.7 seconds Finally, we are now faster than the framework’s Array.Sort implementation.

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• The Retail Week Conference 2012 - Interview with Paul Dickson

  - by user801960

  Recently we attended the Retail Week Conference at the Hilton London Metropole Hotel in London. The conference proves to be an inspirational meeting of retail minds and the insight gained from both the speakers and the other delegates is invaluable. In particular we enjoyed hearing from Charlie Mayfield, Chairman at John Lewis Partnership, about understanding how the consumer is viewing the ever changing world of retail; a session on how to encourage brand-loyal multichannel activities from Robin Terrell of House of Fraser with Alan White of the N Brown Group, Vince Russell from The Cloud and Lucy Neville-Rolfe from Tesco; and a fascinating session from Tim Steiner, Chief Executive of Ocado, about how the business makes it as easy as possible for consumers to shop on their various platforms, which included some surprising usage statistics. Oracle's own Vice President of Retail, Paul Dickson, also held a session with Richard Pennycook, Group Finance Director at Morrisons, about the role of technology in accelerating and supporting the business strategy. Morrisons' 'Evolve' programme takes a litte-and-often approach to updating its technology infrastructure to spread cost and keep the adoption process gentle for staff, and the session explored how the process works and how Oracle's technology underpins the programme to optimise their operations using actionable insight. We had a quick chat with Paul Dickson at the session to get his thoughts on the programme - the video is below. We also filmed the whole presentation, so keep checking back on this blog if you're interested in seeing it.

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• Gnome Do not Launching

  - by PyRulez

  When I try running gnome do, I get this. chris@Chris-Ubuntu-Laptop:~$ gnome-do pgrep: invalid user name: -u and it is not writable Trying sudo: chris@Chris-Ubuntu-Laptop:~$ sudo gnome-do [NetworkService] Could not initialize Network Manager dbus: Unable to open the session message bus. [Error 17:54:30.122] [SystemService] Could not initialize dbus: Unable to open the session message bus. (Do:2401): Wnck-CRITICAL **: wnck_set_client_type got called multiple times. (Do:2401): libdo-WARNING **: Binding '<Super>space' failed! [Error 17:54:30.649] [AbstractKeyBindingService] Key "" is already mapped. Tomboy.NotesItemSource "Tomboy Notes" encountered an error in UpdateItems: System.TypeInitializationException: An exception was thrown by the type initializer for Tomboy.TomboyDBus ---> System.Exception: Unable to open the session message bus. ---> System.ArgumentNullException: Argument cannot be null. Parameter name: address at NDesk.DBus.Bus.Open (System.String address) [0x00000] in <filename unknown>:0 at NDesk.DBus.Bus.get_Session () [0x00000] in <filename unknown>:0 --- End of inner exception stack trace --- at NDesk.DBus.Bus.get_Session () [0x00000] in <filename unknown>:0 at Tomboy.TomboyDBus..cctor () [0x00000] in <filename unknown>:0 --- End of inner exception stack trace --- at Tomboy.NotesItemSource.UpdateItems () [0x00000] in <filename unknown>:0 at Do.Universe.Safe.SafeItemSource.UpdateItems () [0x00000] in <filename unknown>:0 . Firefox.PlacesItemSource "Firefox Places" encountered an error in UpdateItems: System.InvalidCastException: Cannot cast from source type to destination type. at Mono.Data.Sqlite.SqliteDataReader.VerifyType (Int32 i, DbType typ) [0x00000] in <filename unknown>:0 at Mono.Data.Sqlite.SqliteDataReader.GetString (Int32 i) [0x00000] in <filename unknown>:0 at Firefox.PlacesItemSource+<LoadPlaceItems>c__Iterator3.MoveNext () [0x00000] in <filename unknown>:0 at System.Collections.Generic.List`1[Firefox.PlaceItem].AddEnumerable (IEnumerable`1 enumerable) [0x00000] in <filename unknown>:0 at System.Collections.Generic.List`1[Firefox.PlaceItem]..ctor (IEnumerable`1 collection) [0x00000] in <filename unknown>:0 at System.Linq.Enumerable.ToArray[PlaceItem] (IEnumerable`1 source) [0x00000] in <filename unknown>:0 at Firefox.PlacesItemSource.UpdateItems () [0x00000] in <filename unknown>:0 at Do.Universe.Safe.SafeItemSource.UpdateItems () [0x00000] in <filename unknown>:0 . Do.Universe.Linux.GNOMESpecialLocationsItemSource "GNOME Special Locations" encountered an error in UpdateItems: System.IO.FileNotFoundException: Could not find file "/root/.gtk-bookmarks". File name: '/root/.gtk-bookmarks' at System.IO.FileStream..ctor (System.String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, Boolean anonymous, FileOptions options) [0x00000] in <filename unknown>:0 at System.IO.FileStream..ctor (System.String path, FileMode mode, FileAccess access, FileShare share) [0x00000] in <filename unknown>:0 at (wrapper remoting-invoke-with-check) System.IO.FileStream:.ctor (string,System.IO.FileMode,System.IO.FileAccess,System.IO.FileShare) at System.IO.File.OpenRead (System.String path) [0x00000] in <filename unknown>:0 at System.IO.StreamReader..ctor (System.String path, System.Text.Encoding encoding, Boolean detectEncodingFromByteOrderMarks, Int32 bufferSize) [0x00000] in <filename unknown>:0 at System.IO.StreamReader..ctor (System.String path) [0x00000] in <filename unknown>:0 at (wrapper remoting-invoke-with-check) System.IO.StreamReader:.ctor (string) at Do.Universe.Linux.GNOMESpecialLocationsItemSource+<ReadBookmarkItems>c__Iterator3.MoveNext () [0x00000] in <filename unknown>:0 at Do.Universe.Linux.GNOMESpecialLocationsItemSource.UpdateItems () [0x00000] in <filename unknown>:0 at Do.Universe.Safe.SafeItemSource.UpdateItems () [0x00000] in <filename unknown>:0 . ^[^\Full thread dump: "<unnamed thread>" tid=0x0xb7570700 this=0x0x56f18 thread handle 0x403 state : not waiting owns () at (wrapper managed-to-native) Mono.Unix.Native.Syscall.read (int,intptr,ulong) <0xffffffff> at Mono.Unix.Native.Syscall.read (int,void*,ulong) <0x00023> at Mono.Unix.UnixStream.Read (byte[],int,int) <0x0008b> at NDesk.DBus.Connection.ReadMessage () <0x0003c> at NDesk.DBus.Connection.Iterate () <0x0001b> at NDesk.DBus.BusG/<Init>c__AnonStorey0.<>m__0 (intptr,NDesk.GLib.IOCondition,intptr) <0x00033> at (wrapper native-to-managed) NDesk.DBus.BusG/<Init>c__AnonStorey0.<>m__0 (intptr,NDesk.GLib.IOCondition,intptr) <0xffffffff> at (wrapper managed-to-native) Gtk.Clipboard.gtk_clipboard_wait_is_text_available (intptr) <0xffffffff> at Gtk.Clipboard.WaitIsTextAvailable () <0x00017> at Do.Universe.SelectedTextItem.UpdateSelection (object,System.EventArgs) <0x00027> at Do.Platform.AbstractApplicationService.OnSummoned () <0x00025> at Do.Platform.ApplicationService.<ApplicationService>m__31 (object,System.EventArgs) <0x00013> at Do.Core.Controller.OnSummoned () <0x00025> at Do.Core.Controller.Summon () <0x00027> at Do.Do.Main (string[]) <0x001eb> at (wrapper runtime-invoke) <Module>.runtime_invoke_void_object (object,intptr,intptr,intptr) <0xffffffff> "<unnamed thread>" tid=0x0xb2c81b40 this=0x0x194150 thread handle 0x412 state : interrupted state owns () at (wrapper managed-to-native) System.IO.InotifyWatcher.ReadFromFD (intptr,byte[],intptr) <0xffffffff> at System.IO.InotifyWatcher.Monitor () <0x0005f> at System.Threading.Thread.StartInternal () <0x00057> at (wrapper runtime-invoke) object.runtime_invoke_void__this__ (object,intptr,intptr,intptr) <0xffffffff> "Universe Update Dispatcher" tid=0x0xb29ffb40 this=0x0x569d8 thread handle 0x41b state : interrupted state owns () at (wrapper managed-to-native) System.Threading.WaitHandle.WaitOne_internal (System.Threading.WaitHandle,intptr,int,bool) <0xffffffff> at System.Threading.WaitHandle.WaitOne (System.TimeSpan,bool) <0x00133> at System.Threading.WaitHandle.WaitOne (System.TimeSpan) <0x00022> at Do.Core.UniverseManager.UniverseUpdateLoop () <0x0007a> at System.Threading.Thread.StartInternal () <0x00057> at (wrapper runtime-invoke) object.runtime_invoke_void__this__ (object,intptr,intptr,intptr) <0xffffffff> Tomboy.NotesItemSource "Tomboy Notes" encountered an error in UpdateItems: System.TypeInitializationException: An exception was thrown by the type initializer for Tomboy.TomboyDBus ---> System.Exception: Unable to open the session message bus. ---> System.ArgumentNullException: Argument cannot be null. Parameter name: address at NDesk.DBus.Bus.Open (System.String address) [0x00000] in <filename unknown>:0 at NDesk.DBus.Bus.get_Session () [0x00000] in <filename unknown>:0 --- End of inner exception stack trace --- at NDesk.DBus.Bus.get_Session () [0x00000] in <filename unknown>:0 at Tomboy.TomboyDBus..cctor () [0x00000] in <filename unknown>:0 --- End of inner exception stack trace --- at Tomboy.NotesItemSource.UpdateItems () [0x00000] in <filename unknown>:0 at Do.Universe.Safe.SafeItemSource.UpdateItems () [0x00000] in <filename unknown>:0 . Firefox.PlacesItemSource "Firefox Places" encountered an error in UpdateItems: System.InvalidCastException: Cannot cast from source type to destination type. at Mono.Data.Sqlite.SqliteDataReader.VerifyType (Int32 i, DbType typ) [0x00000] in <filename unknown>:0 at Mono.Data.Sqlite.SqliteDataReader.GetString (Int32 i) [0x00000] in <filename unknown>:0 at Firefox.PlacesItemSource+<LoadPlaceItems>c__Iterator3.MoveNext () [0x00000] in <filename unknown>:0 at System.Collections.Generic.List`1[Firefox.PlaceItem].AddEnumerable (IEnumerable`1 enumerable) [0x00000] in <filename unknown>:0 at System.Collections.Generic.List`1[Firefox.PlaceItem]..ctor (IEnumerable`1 collection) [0x00000] in <filename unknown>:0 at System.Linq.Enumerable.ToArray[PlaceItem] (IEnumerable`1 source) [0x00000] in <filename unknown>:0 at Firefox.PlacesItemSource.UpdateItems () [0x00000] in <filename unknown>:0 at Do.Universe.Safe.SafeItemSource.UpdateItems () [0x00000] in <filename unknown>:0 . Do.Universe.Linux.GNOMESpecialLocationsItemSource "GNOME Special Locations" encountered an error in UpdateItems: System.IO.FileNotFoundException: Could not find file "/root/.gtk-bookmarks". File name: '/root/.gtk-bookmarks' at System.IO.FileStream..ctor (System.String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, Boolean anonymous, FileOptions options) [0x00000] in <filename unknown>:0 at System.IO.FileStream..ctor (System.String path, FileMode mode, FileAccess access, FileShare share) [0x00000] in <filename unknown>:0 at (wrapper remoting-invoke-with-check) System.IO.FileStream:.ctor (string,System.IO.FileMode,System.IO.FileAccess,System.IO.FileShare) at System.IO.File.OpenRead (System.String path) [0x00000] in <filename unknown>:0 at System.IO.StreamReader..ctor (System.String path, System.Text.Encoding encoding, Boolean detectEncodingFromByteOrderMarks, Int32 bufferSize) [0x00000] in <filename unknown>:0 at System.IO.StreamReader..ctor (System.String path) [0x00000] in <filename unknown>:0 at (wrapper remoting-invoke-with-check) System.IO.StreamReader:.ctor (string) at Do.Universe.Linux.GNOMESpecialLocationsItemSource+<ReadBookmarkItems>c__Iterator3.MoveNext () [0x00000] in <filename unknown>:0 at Do.Universe.Linux.GNOMESpecialLocationsItemSource.UpdateItems () [0x00000] in <filename unknown>:0 at Do.Universe.Safe.SafeItemSource.UpdateItems () [0x00000] in <filename unknown>:0 . It stops when I try my key combination, ctrl-alt-. It does not pop up though.

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• C# via Java: Introduction

  - by Simon Cooper

  So, I’ve recently changed jobs. Rather than working in .NET land, I’ve migrated over to Java land. But never fear! I’ll continue to peer under the covers of .NET, but my next series will use my new experience in Java to explore the design decisions made in the development of the C# programming language. After all, the design of C# was based on Java 1.2, and both languages have continued to evolve since then, incorporating modern software engineering concepts and requirements. Exploring the differences and similarities between the two will (hopefully) give us a deeper understanding into why .NET is implemented the way it is, the trade-offs involved, and what choices were made when new features were designed and added to the language and framework. Among others, I’ll be looking at differences in: Primitives Operators Generics Exceptions Accessibility Collections Delegates and inner classes Concurrency In my next post, I’ll start off by looking at the type primitives available in each language, and how Java and C# actually incorporate two different concepts of primitive types in their fundamental language design and use. I’m also thinking of looking at the inner details of Java and the JVM in my blogs, as well as C# and the CLR. If you’ve got any comments or thoughts on this, please let me know.

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• C# via Java: Introduction

  - by simonc

  Originally posted on: http://geekswithblogs.net/simonc/archive/2013/11/08/c-via-java-introduction.aspxSo, I've recently changed jobs. Rather than working in .NET land, I've migrated over to Java land. But never fear! I'll continue to peer under the covers of .NET, but my next series will use my new experience in Java to explore the design decisions made in the development of the C# programming language. After all, the design of C# was based on Java 1.2, and both languages have continued to evolve since then, incorporating modern software engineering concepts and requirements. Exploring the differences and similarities between the two will (hopefully) give us a deeper understanding into why .NET is implemented the way it is, the trade-offs involved, and what choices were made when new features were designed and added to the language and framework. Among others, I'll be looking at differences in: Primitives Operators Generics Exceptions Accessibility Collections Delegates and inner classes Concurrency In my next post, I'll start off by looking at the type primitives available in each language, and how Java and C# actually incorporate two different concepts of primitive types in their fundamental language design and use. I'm also thinking of looking at the inner details of Java and the JVM in my blogs, as well as C# and the CLR. If you've got any comments or thoughts on this, please let me know.

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• Extreme Optimization – Curves (Function Mapping) Part 1

  - by JoshReuben

  Overview ·        a curve is a functional map relationship between two factors (i.e. a function - However, the word function is a reserved word). ·        You can use the EO API to create common types of functions, find zeroes and calculate derivatives - currently supports constants, lines, quadratic curves, polynomials and Chebyshev approximations. ·        A function basis is a set of functions that can be combined to form a particular class of functions.   The Curve class ·        the abstract base class from which all other curve classes are derived – it provides the following methods: ·        ValueAt(Double) - evaluates the curve at a specific point. ·        SlopeAt(Double) - evaluates the derivative ·        Integral(Double, Double) - evaluates the definite integral over a specified interval. ·        TangentAt(Double) - returns a Line curve that is the tangent to the curve at a specific point. ·        FindRoots() - attempts to find all the roots or zeroes of the curve. ·        A particular type of curve is defined by a Parameters property, of type ParameterCollection   The GeneralCurve class ·        defines a curve whose value and, optionally, derivative and integrals, are calculated using arbitrary methods. A general curve has no parameters. ·        Constructor params:  RealFunction delegates – 1 for the function, and optionally another 2 for the derivative and integral ·        If no derivative  or integral function is supplied, they are calculated via the NumericalDifferentiation  and AdaptiveIntegrator classes in the Extreme.Mathematics.Calculus namespace. // the function is 1/(1+x^2) private double f(double x) {     return 1 / (1 + x*x); }   // Its derivative is -2x/(1+x^2)^2 private double df(double x) {     double y = 1 + x*x;     return -2*x* / (y*y); }   // The integral of f is Arctan(x), which is available from the Math class. var c1 = new GeneralCurve (new RealFunction(f), new RealFunction(df), new RealFunction(System.Math.Atan)); // Find the tangent to this curve at x=1 (the Line class is derived from Curve) Line l1 = c1.TangentAt(1);

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• Outlook 2003 (with Exchange 2007) error: You cannot respond to a meeting without an Organizer

  - by Hissohathair

  The company recently upgraded to Exchange 2007. Since the upgrade users who are still on Outlook 2003 (SP3) get the following error for some meeting requests: You cannot respond to a meeting without an organizer. You must add an Organizer field to the item. The item has an organizer field filled in. Exchange is 2007 with SP1 MS Office (incl Outlook) is 2003 with SP3 Some users are using iPhones to accept / reject meetings. The iPhones never get an error like this. There are no delegates for the user attempting to accept or reject the meeting. Sometimes the meeting was previously accepted, sometimes not. We have not detected a pattern in the meeting requests that trigger the issue. I've found a few people asking the same question on other websites but no answers. Experts Exchange claims to have an answer but from looking at the discussion at the bottom of the page I'm pretty sure they don't.

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• Why do you hate Java? Is it the language or the framework? [closed]

  - by zneak

  According to you all, Java is the third most-hated language here. The two other most hated languages are PHP and VBScript. (It's quite funny how they stand together on the podium.) I'd like to make it known that the question mostly addresses people who don't like Java. I assume here a number of subjective opinions as facts because they're usually considered true among people who don't like Java, and I don't want to be convinced otherwise here. If you're a Java enthusiast, you might find this question frustrating. It's never been made clear if people hate Java itself, or if they hate it because of the framework, or if it's a mixture of the two. On a side you have the language, where you have: the "everything should be an object" philosophy, even in instances where it should obviously be something else (event handlers I'm pointing you); checked exceptions; the idea that all logic should be presented as methods and properties is a big no-no; the fact that "closures" created by anonymous types only include final variables and arguments, but will allow write access to any member of the parent class; a few more. On the other side, you have the JDK, with... its load of inconsistencies and overengineering; monolithic class hierarchies; meaningless base exceptions like IOException (though other frameworks have similar exception hierarchies); sluggish responsiveness even with Swing; a few more. My question is, do you think that, if either one (Java or the JDK) was taken alone, and the other was dropped in favor of something else, the new combination would be better? For instance, if you could use the C# syntax with the JDK (adapting get*/set* methods into properties, and interfaces with only one method into delegates), or the Java syntax with the .NET Framework (doing the inverse transformations), would things get better in your opinion?

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• Extreme Optimization Numerical Libraries for .NET – Part 1 of n

  - by JoshReuben

  While many of my colleagues are fascinated in constructing the ultimate ViewModel or ServiceBus, I feel that this kind of plumbing code is re-invented far too many times – at some point in the near future, it will be out of the box standard infra. How many times have you been to a customer site and built a different variation of the same kind of code frameworks? How many times can you abstract Prism or reliable and discoverable WCF communication? As the bar is raised for whats bundled with the framework and more tasks become declarative, automated and configurable, Information Systems will expose a higher level of abstraction, forcing software engineers to focus on more advanced computer science and algorithmic tasks. I've spent the better half of the past decade building skills in .NET and expanding my mathematical horizons by working through the Schaums guides. In this series I am going to examine how these skillsets come together in the implementation provided by ExtremeOptimization. Download the trial version here: http://www.extremeoptimization.com/downloads.aspx Overview The library implements a set of algorithms for: linear algebra, complex numbers, numerical integration and differentiation, solving equations, optimization, random numbers, regression, ANOVA, statistical distributions, hypothesis tests. EONumLib combines three libraries in one - organized in a consistent namespace hierarchy. Mathematics Library - Extreme.Mathematics namespace Vector and Matrix Library - Extreme.Mathematics.LinearAlgebra namespace Statistics Library - Extreme.Statistics namespace System Requirements -.NET framework 4.0  Mathematics Library The classes are organized into the following namespace hierarchy: Extreme.Mathematics – common data types, exception types, and delegates. Extreme.Mathematics.Calculus - numerical integration and differentiation of functions. Extreme.Mathematics.Curves - points, lines and curves, including polynomials and Chebyshev approximations. curve fitting and interpolation. Extreme.Mathematics.Generic - generic arithmetic & linear algebra. Extreme.Mathematics.EquationSolvers - root finding algorithms. Extreme.Mathematics.LinearAlgebra - vectors , matrices , matrix decompositions, solvers for simultaneous linear equations and least squares. Extreme.Mathematics.Optimization – multi-d function optimization + linear programming. Extreme.Mathematics.SignalProcessing - one and two-dimensional discrete Fourier transforms. Extreme.Mathematics.SpecialFunctions

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• Vista Enterprise doesn't find logon servers in a network with 802.1x authentication

  - by jneves

  In a network with 802.1x configuration and a samba server configured in the domain, I have a radius server that delegates the authentication against the samba domain for users (using LDAP). The radius defines which VLAN the user is supposed to have access. I'm trying to put a Windows Vista Enterprise in the same network, but it attempts to logon the domain before authenticating against the network in 802.1x and it doesn't find any logon servers. In the radius logs I see the machine trying to authenticate with 'host/'. Does Vista enterprise require that I put it in a network with access to the logon server at that point? Thanks in advance, João Miguel Neves

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• My Latest Books &ndash; Professional C# 2010 and Professional ASP.NET 4

  - by Bill Evjen

  My two latest books are out! Professional ASP.NET 4 in C# and VB Professional C# 4 and .NET 4 From the back covers: Take your web development to the next level using ASP.NET 4 ASP.NET is about making you as productive as possible when building fast and secure web applications. Each release of ASP.NET gets better and removes a lot of the tedious code that you previously needed to put in place, making common ASP.NET tasks easier. With this book, an unparalleled team of authors walks you through the full breadth of ASP.NET and the new and exciting capabilities of ASP.NET 4. The authors also show you how to maximize the abundance of features that ASP.NET offers to make your development process smoother and more efficient. Professional ASP.NET 4: Demonstrates ASP.NET built-in systems such as the membership and role management systems Covers everything you need to know about working with and manipulating data Discusses the plethora of server controls that are at your disposal Explores new ways to build ASP.NET, such as working with ASP.NET MVC and ASP.NET AJAX Examines the full life cycle of ASP.NET, including debugging and error handling, HTTP modules, the provider model, and more Features both printed and downloadable C# and VB code examples Start using the new features of C# 4 and .NET 4 right away The new C# 4 language version is indispensable for writing code in Visual Studio 2010. This essential guide emphasizes that C# is the language of choice for your .NET 4 applications. The unparalleled author team of experts begins with a refresher of C# basics and quickly moves on to provide detailed coverage of all the recently added language and Framework features so that you can start writing Windows applications and ASP.NET web applications immediately. Reviews the .NET architecture, objects, generics, inheritance, arrays, operators, casts, delegates, events, Lambda expressions, and more Details integration with dynamic objects in C#, named and optional parameters, COM-specific interop features, and type-safe variance Provides coverage of new features of .NET 4, Workflow Foundation 4, ADO.NET Data Services, MEF, the Parallel Task Library, and PLINQ Has deep coverage of great technologies including LINQ, WCF, WPF, flow and fixed documents, and Silverlight Reviews ASP.NET programming and goes into new features such as ASP.NET MVC and ASP.NET Dynamic Data Discusses communication with WCF, MSMQ, peer-to-peer, and syndication

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• Local Live Quicktime Video Broadcast, latency?

  - by Snowwire

  I'm looking into the feasibility of using a local server to distribute live video of a conference to delegates in the same room. They would still hear the live audio coming from the speaker, so only the video would be streamed. I was considering a Darwin Steaming Server (a lot of iPhone users to support) and encoding with H.264. My main concern is latency across the network. Even with everything running locally, would there be lip sync issues between the live audio and the 'live' video stream? It feels like there will be problems given the encoding, broadcasting, decoding to be completed, but I've never done any like this before so thought I would check. Thanks

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• Any Practical Alternative to the Signals + Slots model for GUI Programming?

  - by IntermediateHacker

  The majority of GUI Toolkits nowadays use the Signals + Slots model. It was Qt and GTK+, if I am not wrong, who pioneered it. You know, the widgets or graphical objects (sometimes even ones that aren't displayed) send signals to the main-loop handler. The main-loop handler then calls the events, callbacks or slots assigned for that widget / graphical object. There are usually default (and in most cases virtual) event-handlers already provided by the toolkit for handling all pre-defined signals, therefore, unlike previous designs where the developer had to write the entire main-loop and handler for each and every message himself (think WINAPI), the developer only has to worry about the signals he needs to implement new functionality on. Now this design is being used in most modern toolkits as far as I know. There are Qt, GTK+, FLTK etc. There is Java Swing. C# even has a language feature for it ( events and delegates ), and Windows Forms has been developed on this design. In fact, over the last decade, this design for GUI programming has become a kind of an unwritten standard. Since it increases productivity and provides greater abstraction. However, my question is: Is there any alternative design, that is parallel or practical for modern GUI programming? i.e Is the Signals + Slots design, the only practical one in town? Is it feasible to do GUI Programming with any other design? Are any modern (preferably successful and popular) GUI toolkits built on an alternative design?

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• What's a good entity hierarchy for a 2D game?

  - by futlib

  I'm in the process of building a new 2D game out of some code I wrote a while ago. The object hierarchy for entities is like this: Scene (e.g. MainMenu): Contains multiple entities and delegates update()/draw() to each Entity: Base class for all things in a scene (e.g. MenuItem or Alien) Sprite: Base class for all entities that just draw a texture, i.e. don't have their own drawing logic Does it make sense to split up entities and sprites up like that? I think in a 2D game, the terms entity and sprite are somewhat synonymous, right? But I do believe that I need some base class for entities that just draw a texture, as opposed to drawing themselves, to avoid duplication. Most entities are like that. One weird case is my Text class: It derives from Sprite, which accepts either the path of an image or an already loaded texture in its constructor. Text loads a texture in its constructor and passes that to Sprite. Can you outline a design that makes more sense? Or point me to a good object-oriented reference code base for a 2D game? I could only find 3D engine code bases of decent code quality, e.g. Doom 3 and HPL1Engine.

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• Another big year for the ADF EMG at OOW12

  - by Chris Muir

  Oracle Open World 2012 has only just started, but in one way it's just finished!  All the ADF EMG's OOW content is over for another year! The unique highlight this year for me was the first ever ADF EMG social night held on Saturday, where I finally had the chance to meet so many ADF community members who I've known over the internet, but never met in person.  What?  You didn't get an invite?  Oh well, better luck next year ;-) Seriously our budget was limited, so in the happy-dictatorship sort of way I had to limit RSVPs to just 40 people.  Hopefully next year we can do something bigger and better for the wider community. Following directly on from the Saturday social night the ADF EMG ran a full day of sessions at the user group Sunday.  I wont go over the content again, but to say thank you very much to all our presenters and helpers, including Gert Poel, Pitier Gillis, Aino Andriessen, Simon Haslam, Ken Mizuta, Lucas Jellema and the FMW roadshow team, Ronald van Luttikhuizen, Guido Schmutz, Luc Bors, Aino Andriessen and Lonneke Dikmans. Also special thanks must go to Doug Cockroft and Bambi Price for their time and effort in organizing the ADF EMG room behind the scenes via the APOUC. To be blunt Doug and Bambi really do deserve serious thanks because they had to wear a lot of Oracle politics behind the scenes to get the rooms organized (oh, and deal with me fretting too! ;-). Finally thanks to all the members and OOW delegates for turning up and supporting the group on the day.  In the end the ADF EMG exists for you, and I hope you found it worthwhile. Onto 2013 (oh, and the rest of OOW12 ;-) 

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• It's Raining Solaris Training

  - by rajeshr

  That the popularity of Solaris 11 is only growing is clear from how regular the training sessions have been around this product. It's such an excitement to be going around sharing knowledge on Solaris, more so to explore the nitty gritty of many new and evolving features. Trust me, it's only getting better! In the process, just like in the past I stumbled on several individuals, each teaching me a lesson or two. I'm grateful. And if I've managed to get over the laziness to come back to the web logs with a collection of class photos from the last couple of months, it's because of a sense of gratitude to all 'em in the picture below. Solaris 11 Network Administration Pilot Teach in Bangalore. Sun Identity Manager (n.k.a Oracle Waveset IDM) Deployment Fundamentals Training. I'm missing from the snap because these delegates sat well over 10,000 Kms away from where I taught this class from, but were kind enough to help me associate a face with the voice by sending me a group photograph. If you want to attend one such OU program cutting down the travel, try OU's Live Virtual Class (a.k.a LVC) . Transition to Solaris 11 in Mumbai. Solaris 11 Advanced Administration Session in Bangalore. Transition to Solaris 11 in Mumbai. Attending Gary Riseborough's Exadata Training at Singapore. Solaris 11 Advanced Administration Session in Bangalore. If only the participants of each LVC session belonged to the same location, there would've been additional three group photographs occupying this space! Thank you everyone for many many memorable moments.

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• Parallel Class/Interface Hierarchy with the Facade Design Pattern?

  - by Mike G

  About a third of my code is wrapped inside a Facade class. Note that this isn't a "God" class, but actually represents a single thing (called a Line). Naturally, it delegates responsibilities to the subsystem behind it. What ends up happening is that two of the subsystem classes (Output and Timeline) have all of their methods duplicated in the Line class, which effectively makes Line both an Output and a Timeline. It seems to make sense to make Output and Timeline interfaces, so that the Line class can implement them both. At the same time, I'm worried about creating parallel class and interface structures. You see, there are different types of lines AudioLine, VideoLine, which all use the same type of Timeline, but different types of Output (AudioOutput and VideoOutput, respectively). So that would mean that I'd have to create an AudioOutputInterface and VideoOutputInterface as well. So not only would I have to have parallel class hierarchy, but there would be a parallel interface hierarchy as well. Is there any solution to this design flaw? Here's an image of the basic structure (minus the Timeline class, though know that each Line has-a Timeline): NOTE: I just realized that the word 'line' in Timeline might make is sound like is does a similar function as the Line class. They don't, just to clarify.

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• DDDNorth2 Bradford, 13th October 2012 - Async Patterns presentation and source code

  - by Liam Westley

  Many thanks to Andy Westgarth and his team for organising a fantastic conference at the rather elegant Bradford University School of Management. Also, a big congratulations to all the delegates who gave up there free time to come and hear us speak and who were, in general, enthusiastic and asked some cracking questions to keep us speakers on our toes. For those who attended my Async my source code and presentation are now available on GitHub, https://github.com/westleyl/DDDNorth2-AsyncPatterns If you are new to Git then the easiest client to install is GitHub for Windows, a graphical UI for accessing GitHub. Personally, I also have TortoiseGit installed – the file explorer add-in that works in a familiar manner to TortoiseSVN. As I mentioned during the presentation I have not included the sample data, the music files, in the source code placed on GitHub but I have included instructions on how to download them from http://silents.bandcamp.com and place them in the correct folders. What I forgot to mention is that Windows Media Player by default does not play Ogg Vorbis and Flac music files, however you can download the codec installer for these, for free, from http://xiph.org/dshow. I am planning to break down this little project into a series of blog posts, with each pattern being a single blog post over several weeks. In these I will flesh out the background behind the pattern, the basic goal being achieved and how to monitor the progress of the sample data being processed. Basically, what I said during the presentation and is missing from the slides.

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• Assignments in mock return values

  - by zerkms

  (I will show examples using php and phpunit but this may be applied to any programming language) The case: let's say we have a method A::foo that delegates some work to class M and returns the value as-is. Which of these solutions would you choose: $mock = $this->getMock('M'); $mock->expects($this->once()) ->method('bar') ->will($this->returnValue('baz')); $obj = new A($mock); $this->assertEquals('baz', $obj->foo()); or $mock = $this->getMock('M'); $mock->expects($this->once()) ->method('bar') ->will($this->returnValue($result = 'baz')); $obj = new A($mock); $this->assertEquals($result, $obj->foo()); or $result = 'baz'; $mock = $this->getMock('M'); $mock->expects($this->once()) ->method('bar') ->will($this->returnValue($result)); $obj = new A($mock); $this->assertEquals($result, $obj->foo()); Personally I always follow the 2nd solution, but just 10 minutes ago I had a conversation with couple of developers who said that it is "too tricky" and chose 3rd or 1st. So what would you usually do? And do you have any conventions to follow in such cases?

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• Would hybrid drive work after SSD failure

  - by lulalala

  Hybrid hard drive combines SSD with traditional hard drives. I know that SSD can fail much often than traditional hard drives. So I want to ask that, when the SSD part of the hybrid drive fails, would I still be able to use the traditional hard drive? If it won't work like that, then I will consider add-in SATA cards instead, as it delegates risk much better. EDIT: I guess it differs from model to model, so if yes what models would work. (I am evaluating Seagate DX for now)

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