state monad - Page 76 - Developer IT

django simple approach to multi-field search

- by Scott Willman

I have a simple address book app that I want to make searchable. The model would look something like: class Address(models.Model): address1 = models.CharField("Address Line 1", max_length=128) address2 = models.CharField("Address Line 2", max_length=128) city = models.CharField("City", max_length=128) state = models.CharField("State", max_length=24) zipCode = models.CharField("Zip Code", max_length=24) def __unicode__(self): return "%s %s, %s, %s, %s" % (self.address1, self.address2, self.city, self.state, self.zipCode) class Entry(models.Model): name = models.CharField("Official School Name", max_length=128) createdBy = models.ForeignKey(User) address = models.ForeignKey(Address, unique=True) def __unicode__(self): return "%s - %s, %s" % (self.name, self.address.city, self.address.state) I want the searching to be fairly loose, like: Bank of America Los Angeles 91345. It seems like I want a field that contains all of those elements into one that I can search, but that also seems redundant. I was hoping I could add a method to the Entry model like this: def _getSearchText(self): return "%s %s %s" % (self.name, self.address, self.mascot) searchText = property(_getSearchText) ...and search that as a field, but I suppose that's wishful thinking... How should I approach this using basic Django and SqLite (this is a learning exercise). Thank you!!

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NHibernate / Fluent - Mapping multiple objects to single lookup table

- by Al

Hi all I am struggling a little in getting my mapping right. What I have is a single self joined table of look up values of certain types. Each lookup can have a parent, which can be of a different type. For simplicities sake lets take the Country and State example. So the lookup table would look like this: Lookups Id Key Value LookupType ParentId - self joining to Id base class public class Lookup : BaseEntity { public Lookup() {} public Lookup(string key, string value) { Key = key; Value = value; } public virtual Lookup Parent { get; set; } [DomainSignature] [NotNullNotEmpty] public virtual LookupType LookupType { get; set; } [NotNullNotEmpty] public virtual string Key { get; set; } [NotNullNotEmpty] public virtual string Value { get; set; } } The lookup map public class LookupMap : IAutoMappingOverride<DBLookup> { public void Override(AutoMapping<Lookup> map) { map.Table("Lookups"); map.References(x => x.Parent, "ParentId").ForeignKey("Id"); map.DiscriminateSubClassesOnColumn<string>("LookupType").CustomType(typeof(LookupType)); } } BASE SubClass map for subclasses public class BaseLookupMap : SubclassMap where T : DBLookup { protected BaseLookupMap() { } protected BaseLookupMap(LookupType lookupType) { DiscriminatorValue(lookupType); Table("Lookups"); } } Example subclass map public class StateMap : BaseLookupMap<State> { protected StateMap() : base(LookupType.State) { } } Now I've almost got my mappings set, however the mapping is still expecting a table-per-class setup, so is expecting a 'State' table to exist with a reference to the states Id in the Lookup table. I hope this makes sense. This doesn't seem like an uncommon approach when wanting to keep lookup-type values configurable. Thanks in advance. Al

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Is it possible to guarantee a unique id for multiple items using the same id variable at a point in

- by Scarface

First of all, do not be overwhelmed by the long code, I just put it for reference...I have a function that preg_replaces content and puts it in a jquery dialog box with a matching open-link. For example, if there is a paragraph with two matches, they will be put inside two divs, and a jquery dialog function will be echoed twice; one for each div. While this works for one match, if there are multiple matches, it does not. I am not sure how to distribute unique ids at a point in time for each of the divs and matching dialog open-scripts. Keep in mind, I removed the preg replace function since it kind of complicates the problem. If anyone has any ideas, they will be greatly appreciated. <?php $id=uniqid(); $id2=uniqid(); echo "<div id=\"$id2\"> </div>"; ?> $.ui.dialog.defaults.bgiframe = true; $(function() { $("<?php echo"#$id2"; ?>").dialog({hide: 'clip', modal: true ,width: 600,height: 350,position: 'center', show: 'clip',stack: true,title: 'title', minHeight: 25, minWidth: 100, autoOpen: false}); $('<?php echo"#$id"; ?>').click(function() { $('<?php echo"#$id2"; ?>').dialog('open'); }) .hover( function(){ $(this).addClass("ui-state-hover"); }, function(){ $(this).removeClass("ui-state-hover"); } ).mousedown(function(){ $(this).addClass("ui-state-active"); }) .mouseup(function(){ $(this).removeClass("ui-state-active"); }); });

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Can I make TCP/IP session to run less than 60 seconds?

- by Pavel

Our server is overloaded with TCP/IP sessions, we have 1200 - 1500 of them. Most of them are hanging in TIME_OUT state. It turns out that a connection in TIME_OUT state occupies a socket until 60 second time-out is elapsed. The problem is that the server gets unresponsive and many clients are not getting served. I have made a simple test: download an XML file from the server with Internet Explorer 8.0 The download finishes in a fraction of second. But then I see that the TCP/IP connection is hanging in TIME_OUT state for 60 seconds. Is there any way to get rid of TIME_OUT waiting or make it less to free the socket for new connections? I understand why TCP/IP connection enters TIME_OUT state, but I don't understand why Internet Explorer does not close the connection after the XML file download is over. The details. Our server runs web service written in Perl (mod-perl). The service provides weather data to clients. Client is a Flash appication (actually Flash ActiveX control embedded in Windows application). Apache "Keep Alive" option is set to 0

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Running a Model::find in for loop in cakephp v1.3

- by Gaurav Sharma

Hi all, How can I achieve the following result in cakephp: In my application a Topic is related to category, category is related to city and city is finally related to state in other words: topic belongs to category, category belongs to city , city belongs to state.. Now in the Topic controller's index action I want to find out all the topics and it's city and state. How can I do this. I can easily do this using a custom query ($this-Model-query() function ) but then I will be facing pagination difficulties. I tried doing like this function index() { $this->Topic->recursive = 0; $topics = $this->paginate(); for($i=0; $i<count($topics);$i++) { $topics[$i]['City'] = $this->Topic->Category->City->find('all', array('conditions' => array('City.id' => $topics[$i]['Category']['city_id']))); } $this->set(compact('messages')); } The method that I have adopted is not a good one (running query in a loop) Using the recursive property and setting it to highest value (2) will degrade performance and is not going to yield me state information. How shall I solve this ? Please help Thanks

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angular bootstrap typeahead bug

- by Mohammad Akbari

i use angular bootstrap typeahead (this lib ui-bootstrap-tpls.js ) in my app, when use two typeahead in one scope, only one work well, and other not work, this is my code angular.module('plunker', ['ui.bootstrap']); function TypeaheadCtrl($scope) { $scope.selected = undefined; $scope.selected2 = undefined; $scope.states = ['Alabama', 'Alaska','California', 'Hawaii', 'Wisconsin', 'Wyoming']; } <html ng-app="plunker"> <head> <title></title> <link href="lib/angular-bootstrap/bootstrap.css" rel="stylesheet" /> <script src="lib/angular/angular.js"></script> <script src="lib/angular-bootstrap/ui-bootstrap-tpls-0.3.0.min.js"></script> <script src="app.js"></script> </head> <body> <div class='container-fluid' ng-controller="TypeaheadCtrl"> <pre>Model: {{selected| json}}</pre> <input type="text" ng-model="selected" typeahead="state for state in states | filter:$viewValue"> <input type="text" ng-model="selected2" typeahead="state for state in states | filter:$viewValue"> </div> </body> please check this and help.

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Is this a good starting point for iptables in Linux?

- by sbrattla

Hi, I'm new to iptables, and i've been trying to put together a firewall which purpose is to protect a web server. The below rules are the ones i've put together so far, and i would like to hear if the rules makes sense - and wether i've left out anything essential? In addition to port 80, i also need to have port 3306 (mysql) and 22 (ssh) open for external connections. Any feedback is highly appreciated! #!/bin/sh # Clear all existing rules. iptables -F # ACCEPT connections for loopback network connection, 127.0.0.1. iptables -A INPUT -i lo -j ACCEPT # ALLOW established traffic iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT # DROP packets that are NEW but does not have the SYN but set. iptables -A INPUT -p tcp ! --syn -m state --state NEW -j DROP # DROP fragmented packets, as there is no way to tell the source and destination ports of such a packet. iptables -A INPUT -f -j DROP # DROP packets with all tcp flags set (XMAS packets). iptables -A INPUT -p tcp --tcp-flags ALL ALL -j DROP # DROP packets with no tcp flags set (NULL packets). iptables -A INPUT -p tcp --tcp-flags ALL NONE -j DROP # ALLOW ssh traffic (and prevent against DoS attacks) iptables -A INPUT -p tcp --dport ssh -m limit --limit 1/s -j ACCEPT # ALLOW http traffic (and prevent against DoS attacks) iptables -A INPUT -p tcp --dport http -m limit --limit 5/s -j ACCEPT # ALLOW mysql traffic (and prevent against DoS attacks) iptables -A INPUT -p tcp --dport mysql -m limit --limit 25/s -j ACCEPT # DROP any other traffic. iptables -A INPUT -j DROP

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How to use ID selector after jQuery html()

- by user555617

It's amazing to try to understand why the function alert("hello") is not generated after clicking more than once... There is some method to do this function is executed? Note that doesn't work after update using html() involving id "press" in button. Any idea? See: http://jsbin.com/atuqu3 JavaScript: $(document).ready(function (){ $("#press").click(function() { $("#relation-states").html('<select id="state" name="state"> <option value="Texas">Texas</option> </select><button id="press" type="button" title="" aria-haspopup="true" style="width: 175px;"><span>Select an item</span></button>');; alert("hello"); }); }); HTML: <div id="relation-states"> <select id="state" name="state"> <option value="New York">New York</option> </select> <button id="press" type="button" title="" aria-haspopup="true" style="width: 175px;"><span>Select an item</span></button> </div>

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How can get unique values from data table using dql?

- by piemesons

I am having a table in which there is a column in which various values are stored.i want to retrieve unique values from that table using dql. Doctrine_Query::create() ->select('rec.school') ->from('Records rec') ->where("rec.city='$city' ") ->execute(); Now i want only unique values. Can anybody tell me how to do that... Edit Table Structure: CREATE TABLE IF NOT EXISTS `records` ( `id` int(11) NOT NULL AUTO_INCREMENT, `state` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL, `city` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL, `school` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=16334 ; This is the Query I am using: Doctrine_Query::create() ->select('DISTINCT rec.city') ->from('Records rec') ->where("rec.state = '$state'") // ->getSql(); ->execute(); Generting Sql for this gives me: SELECT DISTINCT r.id AS r__id, r.city AS r__city FROM records r WHERE r.state = 'AR' Now check the sql generated:::: DISTINCT is on 'id' column where as i want Distinct on city column. Anybody know how to fix this. EDIT2 Id is unique cause its an auto incremental value.Ya i have some real duplicates in city column like: Delhi and Delhi. Right.. Now when i am trying to fetch data from it, I am getting Delhi two times. How can i make query like this: select DISTINCT rec.city where state="xyz"; Cause this will give me the proper output. EDIT3: Anybody who can tell me how to figure out this query..???

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Compromising design & code quality to integrate with existing modules

- by filip-fku

Greetings! I inherited a C#.NET application I have been extending and improving for a while now. Overall it was obviously a rush-job (or whoever wrote it was seemingly less competent than myself). The app pulls some data from an embedded device & displays and manipulates it. At the core is a communications thread in the main application form which executes a 600+ lines of code method which calls functions all over the place, implementing a state machine - lots of if-state-then-do type code. Interaction with the device is done by setting the state/mode globally and letting the thread do it's thing. (This is just one example of the badness of the code - overall it is not very OO-like, it reminds of the style of embedded C code the device firmware is written in). My problem is that this piece of code is central to the application. The software, communications protocol or device firmware are not documented at all. Obviously to carry on with my work I have to interact with this code. What I would like some guidance on, is whether it is worth scrapping this code & trying to piece together something more reasonable from the information I can reverse engineer? I can't decide! The reason I don't want to refactor is because the code already works, and changing it will surely be a long, laborious and unpleasant task. On the flip side, not refactoring means I have to sometimes compromise the design of other modules so that I may call my code from this state machine! I've heard of "If it ain't broke don't fix it!", so I am wondering if it should apply when "it" is influencing the design of future code! Any advice would be appreciated! Thanks!

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XSLT special characters

- by Apurv

In the following XSL transformation how do I output the '<' and '' symbol? Input XML: <TestResult bugnumber="3214" testname="display.methods::close->test_ManyInvoke" errortype="Failure"><ErrorMessage><![CDATA[calling close() method failed - expected:<2>]]></ErrorMessage> XSLT: <xsl:template match="TestResult"> <xsl:variable name="errorMessage"> <xsl:value-of select="ErrorMessage" disable-output-escaping="yes"/> </xsl:variable> <Test name='{@testname}'> <TestResult> <Passed>false</Passed> <State>failure</State> <Metadata> <Entry name='bugnumber' value='{@bugnumber}' /> </Metadata> <TestOutput> <Metadata> <Entry name='ErrorMessage' value='{$errorMessage}' /> </Metadata> </TestOutput> </TestResult> </Test> </xsl:template> Output XML: <Test name="display.methods::close-&gttest_ManyInvoke"> <TestResult> <Passed>false</Passed> <State>failure</State> <Metadata> <Entry name="bugnumber" value="3214"/> </Metadata> <TestOutput> <Metadata> <Entry name="ErrorMessage" value="calling close() method failed - expected:<2>"/> </Metadata> </TestOutput> </TestResult> </Test>

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Event Source Live streaming in Ruby on rails onError method

- by kishorebjv

I'm trying to implement basic rails4 code with eventsource API & Action controller live, Everything is fine but I'm not able to reach event listner . Controller code: class HomeController < ApplicationController include ActionController::Live def tester response.headers["Content-Type"] = "text/event-stream" 3.times do |n| response.stream.write "message: hellow world! \n\n" sleep 2 end end Js code: var evSource = new EventSource("/home/tester"); evSource.onopen = function (e) { console.log("OPEN state \n"+e.data); }; evSource.addEventListener('message',function(e){ console.log("EventListener .. code.."); },false); evSource.onerror = function (e) { console.log("Error State \n\n"+e.data); }; & When i reloading the page, My console output was "OPEN state" & then "Error State" as output.. event-listener code was not displaying . 1.When I'm curling the page, "message: Hellow world!" was displaying. 2.I changed in development.rb config.cache_classes = true config.eager_load = true 3. My browsers are chrome & firefox are latest versions, so no issues with them, Where I'm missing? suggestions please!

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Object inside of array -- works in one scope but not in another?

- by Earlz

Ok I've been learning some of the more advanced aspects of Javascript and now trying to use this I'm stuck. Here is my code: function Data(){} function init(state){ var item; item=new Data(); item.fieldrid=17; item.description='foo'; state.push(item); }; function findInState(state,fieldrid) { for (var item in state) { alert(item.fieldrid); //prints undefined if (item.fieldrid == fieldrid) { return item; } } return null; } var s=[]; init(s); alert(s[0].fieldrid); //prints 17 (expected) alert(findInState(s,17).fieldrid); //exception here. function returns null. A running example is here at jsbin Why does this not work? I would expect the alert in findInState to yield 17 but instead it yields undefined. What am I doing wrong?

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How to update attributes without valitation

- by Brian Roisentul

I've got a model with its validations, and I found out that I can't update an attribute without validating the object before. I already tried to add on => :create syntax at the end of each validation line, but I got the same results. My announcement model have the following validations: validates_presence_of :title validates_presence_of :description validates_presence_of :announcement_type_id validate :validates_publication_date validate :validates_start_date validate :validates_start_end_dates validate :validates_category validate :validates_province validates_length_of :title, :in => 6..255, :on => :save validates_length_of :subtitle, :in => 0..255, :on => :save validates_length_of :subtitle, :in => 0..255, :on => :save validates_length_of :place, :in => 0..50, :on => :save validates_numericality_of :vacants, :greater_than_or_equal_to => 0, :only_integer => true validates_numericality_of :price, :greater_than_or_equal_to => 0, :only_integer => true My rake task does the following: task :announcements_expiration => :environment do announcements = Announcement.expired announcements.each do |a| #Gets the user that owns the announcement user = User.find(a.user_id) puts a.title + '...' a.state = 'deactivated' if a.update_attributes(:state => a.state) puts 'state changed to deactivated' else a.errors.each do |e| puts e end end end This throws all the validation exceptions for that model, in the output. Does anybody how to update an attribute without validating the model?

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How to reset the context to the original rectangle after clipping it for drawing?

- by mystify

I try to draw a sequence of pattern images (different repeated patterns in one view). So what I did is this, in a loop: CGContextRef context = UIGraphicsGetCurrentContext(); // clip to the drawing rectangle to draw the pattern for this portion of the view CGContextClipToRect(context, drawingRect); // the first call here works fine... but for the next nothing will be drawn CGContextDrawTiledImage(context, CGRectMake(0, 0, 2, 31), [img CGImage]); I think that after I've clipped the context to draw the pattern in the specific rectangle, I cut out a snippet from the big canvas and the next time, my canvas is gone. can't cut out another snippet. So I must reset that clipping somehow in order to be able to draw another pattern again somewhere else? Edit: In the documentation I found this: CGContextClip: "... Therefore, to re-enlarge the paintable area by restoring the clipping path to a prior state, you must save the graphics state before you clip and restore the graphics state after you’ve completed any clipped drawing. ..." Well then, how to store the graphics state before clipping and how to restore it?

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CakePHP - recursive on specific fields in model?

- by Paul

Hi, I'm pretty new to CakePHP but I think I'm starting to get the hang of it. I'm trying to pull related table information recursively, but I want to specify which related models to recurse on. Let me give you an example to demonstrate my goal: I have a model "Customer", which has info like Company name, website, etc. "Customer" hasMany "Addresses", which contain info for individual contacts like Contact Name, Street, City, State, Country, etc. "Customer" also belongsTo "CustomerType", which is just has descriptive category info - a name and description, like "Distributor" or "Manufacturer". When I do a find on "Customer" I want to get associated "CustomerType" and "Address" info as sub-arrays, and this works fine just by setting up the hasMany and belongsTo associations properly. But now, here's my issue: I want to get associated State/Country info. So, instead of each "Address" array row just having "state_id", I want it to have "state" = array("id" = 20, "name" = "New York",...) etc. If I set $recursive to a higher value (e.g., 2) in the Partner model, I get what I want for the State/Country info in each "Address". BUT it also recurses on "CustomerType", and that results in the "CustomerType" field of my "Partner" object having a huge array of all Customer objects that match that type, which could be thousands long. So the point is, I DON'T want to recurse on "CustomerType", only on "Address". Is there a way I can set this up? Sorry for the long-winded question, and thanks in advance!

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How to update attributes without validation

- by Brian Roisentul

I've got a model with its validations, and I found out that I can't update an attribute without validating the object before. I already tried to add on => :create syntax at the end of each validation line, but I got the same results. My announcement model have the following validations: validates_presence_of :title validates_presence_of :description validates_presence_of :announcement_type_id validate :validates_publication_date validate :validates_start_date validate :validates_start_end_dates validate :validates_category validate :validates_province validates_length_of :title, :in => 6..255, :on => :save validates_length_of :subtitle, :in => 0..255, :on => :save validates_length_of :subtitle, :in => 0..255, :on => :save validates_length_of :place, :in => 0..50, :on => :save validates_numericality_of :vacants, :greater_than_or_equal_to => 0, :only_integer => true validates_numericality_of :price, :greater_than_or_equal_to => 0, :only_integer => true My rake task does the following: task :announcements_expiration => :environment do announcements = Announcement.expired announcements.each do |a| #Gets the user that owns the announcement user = User.find(a.user_id) puts a.title + '...' a.state = 'deactivated' if a.update_attributes(:state => a.state) puts 'state changed to deactivated' else a.errors.each do |e| puts e end end end This throws all the validation exceptions for that model, in the output. Does anybody how to update an attribute without validating the model?

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:include and table aliasing

- by dondo

I'm suffering from a variant of the problem described here: ActiveRecord assigns table aliases for association joins fairly unpredictably. The first association to a given table keeps the table name. Further joins with associations to that table use aliases including the association names in the path... but it is common for app developers not to know about [other] joins at coding time. In my case I'm being bitten by a toxic mix of has_many and :include. Many tables in my schema have a state column, and the has_many wants to specify conditions on that column: has_many :foo, :conditions => {:state => 1}. However, since the state column appears in many tables, I disambiguate by explicitly specifying the table name: has_many :foo, :conditions => "this_table.state = 1". This has worked fine until now, when for efficiency I want to add an :include to preload a fairly deep tree of data. This causes the table to be aliased inconsistently in different code paths. My reading of the tickets referenced above is that this problem is not and will not be fixed in Rails 2.x. However, I don't see any way to apply the suggested workaround (to specify the aliased table name explicitly in the query). I'm happy to specify the table alias explicitly in the has_many statement, but I don't see any way to do so. As such, the workaround doesn't appear applicable to this situation (nor, I presume, in many 'named_scope' scenarios). Is there a viable workaround?

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Quick question regarding MVC framework for a java game

- by Jason

I have a question regarding the use of the MVC framework for a blackjack game im writing in java. As I understand, my model would be a class that stores the state of the game, and more specifically, each players hand. Within the model class, I would have an array of listeners, which would be notified each time the game state changes (ie a player has drawn a new card). These listeners would be my viewer, which is the class that handles the display of the game. This class would implement the ActionListener interface, and each time the model changes, it would call/"notify" my viewer's actionPerformed method. My question is as follows: I intend to have two JPanels, each devoted to displaying the respective player's hand. As a player draws a new card, a new ImageIcon would be added to the panel. My question is how would the viewer class know what card has been added to the player's hand? I suppose I could store the player's hand before a notify event, and then upon the notification event, compare the new state with the old, to find out what has changed. I'm a complete novice here, so I could be completely wrong, but it seems a bit tedious to do this. Is there a more efficient/common way of detecting what has changed in the model between the before and after state? Another solution would be to redraw the entire panel each time the notification occurs? Would this be a better idea?

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C# form - checkboxes do not respond to plus/minus keys - easy workaround?

- by Scott

On forms created with pre dotNET VB and C++ (MFC), a checkbox control responded to the plus/minus key without custom programming. When focus was on the checbox control, pressing PLUS would check the box, no matter what the previous state (checked/unchecked), while pressing MINUS would uncheck it, no matter the previous state. C# winform checkboxes do not seem to exhibit this behavior. Said behavior was very, very handy for automation, whereby the automating program would set focus to a checkbox control and issue a PLUS or MINUS to check or uncheck it. Without this capability, that cannot be done, as the automation program (at least the one I am using) is unable to query the current state of the checkbox (so it can decide whether to issue a SPACE key to toggle the state to the desired one). I've gone over the properties of a checkbox in the Visual Studio 2008 IDE and could not find anything that would restore/enable response to PLUS/MINUS. Since I am in control of the sourcecode for the WinForms in question, I could replace all checkbox controls with a custom checkbox control, but blech, I'd like to avoid that - heck, I don't think I could even consider that given the amount of refactoring that would need to be done. So the bottom line is: does anyone know of a way to get this behavior back more easily than a coding change?

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Parallelism in .NET – Part 14, The Different Forms of Task

- by Reed

Before discussing Task creation and actual usage in concurrent environments, I will briefly expand upon my introduction of the Task class and provide a short explanation of the distinct forms of Task. The Task Parallel Library includes four distinct, though related, variations on the Task class. In my introduction to the Task class, I focused on the most basic version of Task. This version of Task, the standard Task class, is most often used with an Action delegate. This allows you to implement for each task within the task decomposition as a single delegate. Typically, when using the new threading constructs in .NET 4 and the Task Parallel Library, we use lambda expressions to define anonymous methods. The advantage of using a lambda expression is that it allows the Action delegate to directly use variables in the calling scope. This eliminates the need to make separate Task classes for Action<T>, Action<T1,T2>, and all of the other Action<…> delegate types. As an example, suppose we wanted to make a Task to handle the ”Show Splash” task from our earlier decomposition. Even if this task required parameters, such as a message to display, we could still use an Action delegate specified via a lambda: // Store this as a local variable string messageForSplashScreen = GetSplashScreenMessage(); // Create our task Task showSplashTask = new Task( () => { // We can use variables in our outer scope, // as well as methods scoped to our class! this.DisplaySplashScreen(messageForSplashScreen); }); .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 provides a huge amount of flexibility. We can use this single form of task for any task which performs an operation, provided the only information we need to track is whether the task has completed successfully or not. This leads to my first observation: Use a Task with a System.Action delegate for any task for which no result is generated. This observation leads to an obvious corollary: we also need a way to define a task which generates a result. The Task Parallel Library provides this via the Task<TResult> class. Task<TResult> subclasses the standard Task class, providing one additional feature – the ability to return a value back to the user of the task. This is done by switching from providing an Action delegate to providing a Func<TResult> delegate. If we decompose our problem, and we realize we have one task where its result is required by a future operation, this can be handled via Task<TResult>. For example, suppose we want to make a task for our “Check for Update” task, we could do: Task<bool> checkForUpdateTask = new Task<bool>( () => { return this.CheckWebsiteForUpdate(); }); Later, we would start this task, and perform some other work. At any point in the future, we could get the value from the Task<TResult>.Result property, which will cause our thread to block until the task has finished processing: // This uses Task<bool> checkForUpdateTask generated above... // Start the task, typically on a background thread checkForUpdateTask.Start(); // Do some other work on our current thread this.DoSomeWork(); // Discover, from our background task, whether an update is available // This will block until our task completes bool updateAvailable = checkForUpdateTask.Result; This leads me to my second observation: Use a Task<TResult> with a System.Func<TResult> delegate for any task which generates a result. Task and Task<TResult> provide a much cleaner alternative to the previous Asynchronous Programming design patterns in the .NET framework. Instead of trying to implement IAsyncResult, and providing BeginXXX() and EndXXX() methods, implementing an asynchronous programming API can be as simple as creating a method that returns a Task or Task<TResult>. The client side of the pattern also is dramatically simplified – the client can call a method, then either choose to call task.Wait() or use task.Result when it needs to wait for the operation’s completion. While this provides a much cleaner model for future APIs, there is quite a bit of infrastructure built around the current Asynchronous Programming design patterns. In order to provide a model to work with existing APIs, two other forms of Task exist. There is a constructor for Task which takes an Action<Object> and a state parameter. In addition, there is a constructor for creating a Task<TResult> which takes a Func<Object, TResult> as well as a state parameter. When using these constructors, the state parameter is stored in the Task.AsyncState property. While these two overloads exist, and are usable directly, I strongly recommend avoiding this for new development. The two forms of Task which take an object state parameter exist primarily for interoperability with traditional .NET Asynchronous Programming methodologies. Using lambda expressions to capture variables from the scope of the creator is a much cleaner approach than using the untyped state parameters, since lambda expressions provide full type safety without introducing new variables.

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Azure, don't give me multiple VMs, give me one elastic VM

- by FransBouma

Yesterday, Microsoft revealed new major features for Windows Azure (see ScottGu's post). It all looks shiny and great, but after reading most of the material describing the new features, I still find the overall idea behind all of it flawed: why should I care on how much VMs my web app runs? Isn't that a problem to solve for the Windows Azure engineers / software? And what if I need the file system, why can't I simply get a virtual filesystem ? To illustrate my point, let's use a real example: a product website with a customer system/database and next to it a support site with accompanying database. Both are written in .NET, using ASP.NET and use a SQL Server database each. The product website offers files to download by customers, very simple. You have a couple of options to host these websites: Buy a server, place it in a rack at an ISP and run the sites on that server Use 'shared hosting' with an ISP, which means your sites' appdomains are running on the same machine, as well as the files stored, and the databases are hosted in the same server as the other shared databases. Hire a VM, install your OS of choice at an ISP, and host the sites on that VM, basically the same as the first option, except you don't have a physical server At some cloud-vendor, either host the sites 'shared' or in a VM. See above. With all of those options, scalability is a problem, even the cloud-based ones, though not due to the same reasons: The physical server solution has the obvious problem that if you need more power, you need to buy a bigger server or more servers which requires you to add replication and other overhead Shared hosting solutions are almost always capped on memory usage / traffic and database size: if your sites get too big, you have to move out of the shared hosting environment and start over with one of the other solutions The VM solution, be it a VM at an ISP or 'in the cloud' at e.g. Windows Azure or Amazon, in theory allows scaling out by simply instantiating more VMs, however that too introduces the same overhead problems as with the physical servers: suddenly more than 1 instance runs your sites. If a cloud vendor offers its services in the form of VMs, you won't gain much over having a VM at some ISP: the main problems you have to work around are still there: when you spin up more than one VM, your application must be completely stateless at any moment, including the DB sub system, because what's in memory in instance 1 might not be in memory in instance 2. This might sounds trivial but it's not. A lot of the websites out there started rather small: they were perfectly runnable on a single machine with normal memory and CPU power. After all, you don't need a big machine to run a website with even thousands of users a day. Moving these sites to a multi-VM environment will cause a problem: all the in-memory state they use, all the multi-page transitions they use while keeping state across the transition, they can't do that anymore like they did that on a single machine: state is something of the past, you have to store every byte of state in either a DB or in a viewstate or in a cookie somewhere so with the next request, all state information is available through the request, as nothing is kept in-memory. Our example uses a bunch of files in a file system. Using multiple VMs will require that these files move to a cloud storage system which is mounted in each VM so we don't have to store the files on each VM. This might require different file paths, but this change should be minor. What's perhaps less minor is the maintenance procedure in place on the new type of cloud storage used: instead of ftp-ing into a VM, you might have to update the files using different ways / tools. All in all this makes moving an existing website which was written for an environment that's based around a VM (namely .NET with its CLR) overly cumbersome and problematic: it forces you to refactor your website system to be able to be used 'in the cloud', which is caused by the limited way how e.g. Windows Azure offers its cloud services: in blocks of VMs. Offer a scalable, flexible VM which extends with my needs Instead, cloud vendors should offer simply one VM to me. On that VM I run the websites, store my DB and my files. As it's a virtual machine, how this machine is actually ran on physical hardware (e.g. partitioned), I don't care, as that's the problem for the cloud vendor to solve. If I need more resources, e.g. I have more traffic to my server, way more visitors per day, the VM stretches, like I bought a bigger box. This frees me from the problem which comes with multiple VMs: I don't have any refactoring to do at all: I can simply build my website as if it runs on my local hardware server, upload it to the VM offered by the cloud vendor, install it on the VM and I'm done. "But that might require changes to windows!" Yes, but Microsoft is Windows. Windows Azure is their service, they can make whatever change to what they offer to make it look like it's windows. Yet, they're stuck, like Amazon, in thinking in VMs, which forces developers to 'think ahead' and gamble whether they would need to migrate to a cloud with multiple VMs in the future or not. Which comes down to: gamble whether they should invest time in code / architecture which they might never need. (YAGNI anyone?) So the VM we're talking about, is that a low-level VM which runs a guest OS, or is that VM a different kind of VM? The flexible VM: .NET's CLR ? My example websites are ASP.NET based, which means they run inside a .NET appdomain, on the .NET CLR, which is a VM. The only physical OS resource the sites need is the file system, however this too is accessed through .NET. In short: all the websites see is what .NET allows the websites to see, the world as the websites know it is what .NET shows them and lets them access. How the .NET appdomain is run physically, that's the concern of .NET, not mine. This begs the question why Windows Azure doesn't offer virtual appdomains? Or better: .NET environments which look like one machine but could be physically multiple machines. In such an environment, no change has to be made to the websites to migrate them from a local machine or own server to the cloud to get proper scaling: the .NET VM will simply scale with the need: more memory needed, more CPU power needed, it stretches. What it offers to the application running inside the appdomain is simply increasing, but not fragmented: all resources are available to the application: this means that the problem of how to scale is back to where it should be: with the cloud vendor. "Yeah, great, but what about the databases?" The .NET application communicates with the database server through a .NET ADO.NET provider. Where the database is located is not a problem of the appdomain: the ADO.NET provider has to solve that. I.o.w.: we can host the databases in an environment which offers itself as a single resource and is accessible through one connection string without replication overhead on the outside, and use that environment inside the .NET VM as if it was a single DB. But what about memory replication and other problems? This environment isn't simple, at least not for the cloud vendor. But it is simple for the customer who wants to run his sites in that cloud: no work needed. No refactoring needed of existing code. Upload it, run it. Perhaps I'm dreaming and what I described above isn't possible. Yet, I think if cloud vendors don't move into that direction, what they're offering isn't interesting: it doesn't solve a problem at all, it simply offers a way to instantiate more VMs with the guest OS of choice at the cost of me needing to refactor my website code so it can run in the straight jacket form factor dictated by the cloud vendor. Let's not kid ourselves here: most of us developers will never build a website which needs a truck load of VMs to run it: almost all websites created by developers can run on just a few VMs at most. Yet, the most expensive change is right at the start: moving from one to two VMs. As soon as you have refactored your website code to run across multiple VMs, adding another one is just as easy as clicking a mouse button. But that first step, that's the problem here and as it's right there at the beginning of scaling the website, it's particularly strange that cloud vendors refuse to solve that problem and leave it to the developers to solve that. Which makes migrating 'to the cloud' particularly expensive.

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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#: LINQ vs foreach - Round 1.

- by James Michael Hare

So I was reading Peter Kellner's blog entry on Resharper 5.0 and its LINQ refactoring and thought that was very cool. But that raised a point I had always been curious about in my head -- which is a better choice: manual foreach loops or LINQ? The answer is not really clear-cut. There are two sides to any code cost arguments: performance and maintainability. The first of these is obvious and quantifiable. Given any two pieces of code that perform the same function, you can run them side-by-side and see which piece of code performs better. Unfortunately, this is not always a good measure. Well written assembly language outperforms well written C++ code, but you lose a lot in maintainability which creates a big techncial debt load that is hard to offset as the application ages. In contrast, higher level constructs make the code more brief and easier to understand, hence reducing technical cost. Now, obviously in this case we're not talking two separate languages, we're comparing doing something manually in the language versus using a higher-order set of IEnumerable extensions that are in the System.Linq library. Well, before we discuss any further, let's look at some sample code and the numbers. First, let's take a look at the for loop and the LINQ expression. This is just a simple find comparison: // find implemented via LINQ public static bool FindViaLinq(IEnumerable<int> list, int target) { return list.Any(item => item == target); } // find implemented via standard iteration public static bool FindViaIteration(IEnumerable<int> list, int target) { foreach (var i in list) { if (i == target) { return true; } } return false; } Okay, looking at this from a maintainability point of view, the Linq expression is definitely more concise (8 lines down to 1) and is very readable in intention. You don't have to actually analyze the behavior of the loop to determine what it's doing. So let's take a look at performance metrics from 100,000 iterations of these methods on a List<int> of varying sizes filled with random data. For this test, we fill a target array with 100,000 random integers and then run the exact same pseudo-random targets through both searches. List<T> On 100,000 Iterations Method Size Total (ms) Per Iteration (ms) % Slower Any 10 26 0.00046 30.00% Iteration 10 20 0.00023 - Any 100 116 0.00201 18.37% Iteration 100 98 0.00118 - Any 1000 1058 0.01853 16.78% Iteration 1000 906 0.01155 - Any 10,000 10,383 0.18189 17.41% Iteration 10,000 8843 0.11362 - Any 100,000 104,004 1.8297 18.27% Iteration 100,000 87,941 1.13163 - The LINQ expression is running about 17% slower for average size collections and worse for smaller collections. Presumably, this is due to the overhead of the state machine used to track the iterators for the yield returns in the LINQ expressions, which seems about right in a tight loop such as this. So what about other LINQ expressions? After all, Any() is one of the more trivial ones. I decided to try the TakeWhile() algorithm using a Count() to get the position stopped like the sample Pete was using in his blog that Resharper refactored for him into LINQ: // Linq form public static int GetTargetPosition1(IEnumerable<int> list, int target) { return list.TakeWhile(item => item != target).Count(); } // traditionally iterative form public static int GetTargetPosition2(IEnumerable<int> list, int target) { int count = 0; foreach (var i in list) { if(i == target) { break; } ++count; } return count; } Once again, the LINQ expression is much shorter, easier to read, and should be easier to maintain over time, reducing the cost of technical debt. So I ran these through the same test data: List<T> On 100,000 Iterations Method Size Total (ms) Per Iteration (ms) % Slower TakeWhile 10 41 0.00041 128% Iteration 10 18 0.00018 - TakeWhile 100 171 0.00171 88% Iteration 100 91 0.00091 - TakeWhile 1000 1604 0.01604 94% Iteration 1000 825 0.00825 - TakeWhile 10,000 15765 0.15765 92% Iteration 10,000 8204 0.08204 - TakeWhile 100,000 156950 1.5695 92% Iteration 100,000 81635 0.81635 - Wow! I expected some overhead due to the state machines iterators produce, but 90% slower? That seems a little heavy to me. So then I thought, well, what if TakeWhile() is not the right tool for the job? The problem is TakeWhile returns each item for processing using yield return, whereas our for-loop really doesn't care about the item beyond using it as a stop condition to evaluate. So what if that back and forth with the iterator state machine is the problem? Well, we can quickly create an (albeit ugly) lambda that uses the Any() along with a count in a closure (if a LINQ guru knows a better way PLEASE let me know!), after all , this is more consistent with what we're trying to do, we're trying to find the first occurence of an item and halt once we find it, we just happen to be counting on the way. This mostly matches Any(). // a new method that uses linq but evaluates the count in a closure. public static int TakeWhileViaLinq2(IEnumerable<int> list, int target) { int count = 0; list.Any(item => { if(item == target) { return true; } ++count; return false; }); return count; } Now how does this one compare? List<T> On 100,000 Iterations Method Size Total (ms) Per Iteration (ms) % Slower TakeWhile 10 41 0.00041 128% Any w/Closure 10 23 0.00023 28% Iteration 10 18 0.00018 - TakeWhile 100 171 0.00171 88% Any w/Closure 100 116 0.00116 27% Iteration 100 91 0.00091 - TakeWhile 1000 1604 0.01604 94% Any w/Closure 1000 1101 0.01101 33% Iteration 1000 825 0.00825 - TakeWhile 10,000 15765 0.15765 92% Any w/Closure 10,000 10802 0.10802 32% Iteration 10,000 8204 0.08204 - TakeWhile 100,000 156950 1.5695 92% Any w/Closure 100,000 108378 1.08378 33% Iteration 100,000 81635 0.81635 - Much better! It seems that the overhead of TakeAny() returning each item and updating the state in the state machine is drastically reduced by using Any() since Any() iterates forward until it finds the value we're looking for -- for the task we're attempting to do. So the lesson there is, make sure when you use a LINQ expression you're choosing the best expression for the job, because if you're doing more work than you really need, you'll have a slower algorithm. But this is true of any choice of algorithm or collection in general. Even with the Any() with the count in the closure it is still about 30% slower, but let's consider that angle carefully. For a list of 100,000 items, it was the difference between 1.01 ms and 0.82 ms roughly in a List<T>. That's really not that bad at all in the grand scheme of things. Even running at 90% slower with TakeWhile(), for the vast majority of my projects, an extra millisecond to save potential errors in the long term and improve maintainability is a small price to pay. And if your typical list is 1000 items or less we're talking only microseconds worth of difference. It's like they say: 90% of your performance bottlenecks are in 2% of your code, so over-optimizing almost never pays off. So personally, I'll take the LINQ expression wherever I can because they will be easier to read and maintain (thus reducing technical debt) and I can rely on Microsoft's development to have coded and unit tested those algorithm fully for me instead of relying on a developer to code the loop logic correctly. If something's 90% slower, yes, it's worth keeping in mind, but it's really not until you start get magnitudes-of-order slower (10x, 100x, 1000x) that alarm bells should really go off. And if I ever do need that last millisecond of performance? Well then I'll optimize JUST THAT problem spot. To me it's worth it for the readability, speed-to-market, and maintainability.

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Upgrading from 12.10 to 13.04 -> dpkg: error processing sudo (--configure)

- by Korrigan Nagirrok

Here's the deal and reason I'm asking for your help. Last night I went on upgrading my Xubuntu 12.10 installation to 13.04, so at tty1 I run the command sudo do-release-upgrade and everything seemed to went well except that after rebooting and when I run sudo apt-get update && sudo apt-get upgrade I get this error: sudo apt-get update && sudo apt-get upgrade Hit http://pt.archive.ubuntu.com raring Release.gpg Hit http://pt.archive.ubuntu.com raring-updates Release.gpg Hit http://dl.google.com stable Release.gpg Hit http://pt.archive.ubuntu.com raring-backports Release.gpg Hit http://pt.archive.ubuntu.com raring Release Hit http://archive.canonical.com raring Release.gpg Hit http://ppa.launchpad.net raring Release.gpg Hit http://pt.archive.ubuntu.com raring-updates Release Hit http://extras.ubuntu.com raring Release.gpg Hit http://pt.archive.ubuntu.com raring-backports Release Hit http://dl.google.com stable Release Hit http://pt.archive.ubuntu.com raring/main Sources Hit http://pt.archive.ubuntu.com raring/restricted Sources Hit http://extras.ubuntu.com raring Release Hit http://archive.canonical.com raring Release Hit http://ppa.launchpad.net raring Release.gpg Hit http://pt.archive.ubuntu.com raring/universe Sources Hit http://pt.archive.ubuntu.com raring/multiverse Sources Hit http://dl.google.com stable/main i386 Packages Get:1 http://security.ubuntu.com raring-security Release.gpg [933 B] Hit http://pt.archive.ubuntu.com raring/main i386 Packages Hit http://extras.ubuntu.com raring/main Sources Hit http://ppa.launchpad.net raring Release Hit http://archive.canonical.com raring/partner i386 Packages Hit http://pt.archive.ubuntu.com raring/restricted i386 Packages Hit http://pt.archive.ubuntu.com raring/universe i386 Packages Hit http://extras.ubuntu.com raring/main i386 Packages Hit http://pt.archive.ubuntu.com raring/multiverse i386 Packages Hit http://ppa.launchpad.net raring Release Hit http://pt.archive.ubuntu.com raring/main Translation-en Hit http://ppa.launchpad.net raring/main Sources Hit http://ppa.launchpad.net raring/main i386 Packages Hit http://pt.archive.ubuntu.com raring/multiverse Translation-en Hit http://pt.archive.ubuntu.com raring/restricted Translation-en Hit http://pt.archive.ubuntu.com raring/universe Translation-en Hit http://pt.archive.ubuntu.com raring-updates/main Sources Hit http://pt.archive.ubuntu.com raring-updates/restricted Sources Hit http://ppa.launchpad.net raring/main Sources Hit http://pt.archive.ubuntu.com raring-updates/universe Sources Hit http://pt.archive.ubuntu.com raring-updates/multiverse Sources Hit http://pt.archive.ubuntu.com raring-updates/main i386 Packages Hit http://ppa.launchpad.net raring/main i386 Packages Hit http://pt.archive.ubuntu.com raring-updates/restricted i386 Packages Hit http://pt.archive.ubuntu.com raring-updates/universe i386 Packages Hit http://pt.archive.ubuntu.com raring-updates/multiverse i386 Packages Ign http://dl.google.com stable/main Translation-en_US Hit http://pt.archive.ubuntu.com raring-updates/main Translation-en Ign http://archive.canonical.com raring/partner Translation-en_US Ign http://extras.ubuntu.com raring/main Translation-en_US Ign http://dl.google.com stable/main Translation-en Ign http://archive.canonical.com raring/partner Translation-en Hit http://pt.archive.ubuntu.com raring-updates/multiverse Translation-en Ign http://extras.ubuntu.com raring/main Translation-en Hit http://pt.archive.ubuntu.com raring-updates/restricted Translation-en Hit http://pt.archive.ubuntu.com raring-updates/universe Translation-en Hit http://pt.archive.ubuntu.com raring-backports/main Sources Hit http://pt.archive.ubuntu.com raring-backports/restricted Sources Hit http://pt.archive.ubuntu.com raring-backports/universe Sources Hit http://pt.archive.ubuntu.com raring-backports/multiverse Sources Hit http://pt.archive.ubuntu.com raring-backports/main i386 Packages Hit http://pt.archive.ubuntu.com raring-backports/restricted i386 Packages Hit http://pt.archive.ubuntu.com raring-backports/universe i386 Packages Hit http://pt.archive.ubuntu.com raring-backports/multiverse i386 Packages Hit http://pt.archive.ubuntu.com raring-backports/main Translation-en Hit http://pt.archive.ubuntu.com raring-backports/multiverse Translation-en Get:2 http://security.ubuntu.com raring-security Release [40.8 kB] Hit http://pt.archive.ubuntu.com raring-backports/restricted Translation-en Hit http://pt.archive.ubuntu.com raring-backports/universe Translation-en Ign http://ppa.launchpad.net raring/main Translation-en_US Ign http://ppa.launchpad.net raring/main Translation-en Get:3 http://security.ubuntu.com raring-security/main Sources [2,109 B] Ign http://ppa.launchpad.net raring/main Translation-en_US Ign http://ppa.launchpad.net raring/main Translation-en Get:4 http://security.ubuntu.com raring-security/restricted Sources [14 B] Get:5 http://security.ubuntu.com raring-security/universe Sources [14 B] Get:6 http://security.ubuntu.com raring-security/multiverse Sources [14 B] Get:7 http://security.ubuntu.com raring-security/main i386 Packages [3,670 B] Get:8 http://security.ubuntu.com raring-security/restricted i386 Packages [14 B] Get:9 http://security.ubuntu.com raring-security/universe i386 Packages [2,824 B] Get:10 http://security.ubuntu.com raring-security/multiverse i386 Packages [14 B] Ign http://pt.archive.ubuntu.com raring/main Translation-en_US Ign http://pt.archive.ubuntu.com raring/multiverse Translation-en_US Ign http://pt.archive.ubuntu.com raring/restricted Translation-en_US Ign http://pt.archive.ubuntu.com raring/universe Translation-en_US Ign http://pt.archive.ubuntu.com raring-updates/main Translation-en_US Ign http://pt.archive.ubuntu.com raring-updates/multiverse Translation-en_US Hit http://security.ubuntu.com raring-security/main Translation-en Ign http://pt.archive.ubuntu.com raring-updates/restricted Translation-en_US Ign http://pt.archive.ubuntu.com raring-updates/universe Translation-en_US Ign http://pt.archive.ubuntu.com raring-backports/main Translation-en_US Ign http://pt.archive.ubuntu.com raring-backports/multiverse Translation-en_US Ign http://pt.archive.ubuntu.com raring-backports/restricted Translation-en_US Hit http://security.ubuntu.com raring-security/multiverse Translation-en Ign http://pt.archive.ubuntu.com raring-backports/universe Translation-en_US Hit http://security.ubuntu.com raring-security/restricted Translation-en Hit http://security.ubuntu.com raring-security/universe Translation-en Ign http://security.ubuntu.com raring-security/main Translation-en_US Ign http://security.ubuntu.com raring-security/multiverse Translation-en_US Ign http://security.ubuntu.com raring-security/restricted Translation-en_US Ign http://security.ubuntu.com raring-security/universe Translation-en_US Fetched 50.4 kB in 6s (7,454 B/s) Reading package lists... Done Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. 2 not fully installed or removed. Need to get 0 B/373 kB of archives. After this operation, 0 B of additional disk space will be used. Do you want to continue [Y/n]? Y dpkg: error processing sudo (--configure): Package is in a very bad inconsistent state - you should reinstall it before attempting configuration. No apport report written because MaxReports is reached already dpkg: dependency problems prevent configuration of ubuntu-minimal: ubuntu-minimal depends on sudo; however: Package sudo is not configured yet. dpkg: error processing ubuntu-minimal (--configure): dependency problems - leaving unconfigured No apport report written because MaxReports is reached already Errors were encountered while processing: sudo ubuntu-minimal E: Sub-process /usr/bin/dpkg returned an error code (1) I've tried everything I thought logical, like sudo dpkg --configure -a dpkg: error processing sudo (--configure): Package is in a very bad inconsistent state - you should reinstall it before attempting configuration. dpkg: dependency problems prevent configuration of ubuntu-minimal: ubuntu-minimal depends on sudo; however: Package sudo is not configured yet. dpkg: error processing ubuntu-minimal (--configure): dependency problems - leaving unconfigured Errors were encountered while processing: sudo ubuntu-minimal sudo apt-get install -f Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. 2 not fully installed or removed. Need to get 0 B/373 kB of archives. After this operation, 0 B of additional disk space will be used. dpkg: error processing sudo (--configure): Package is in a very bad inconsistent state - you should reinstall it before attempting configuration. dpkg: dependency problems prevent configuration of ubuntu-minimal: ubuntu-minimal depends on sudo; however: Package sudo is not configured yet. dpkg: error processing ubuntu-minimal (--configure): dependency problems - leaving unconfigured No apport report written because MaxReports is reached already No apport report written because MaxReports is reached already Errors were encountered while processing: sudo ubuntu-minimal E: Sub-process /usr/bin/dpkg returned an error code (1) Can someone help me, please. Edit: Here's some more info that could be of help for anyone. The output of apt-cache policy linux-image-generic-pae linux-generic-pae is linux-image-generic-pae: Installed: (none) Candidate: 3.8.0.19.35 Version table: 3.8.0.19.35 0 500 http://pt.archive.ubuntu.com/ubuntu/ raring/main i386 Packages linux-generic-pae: Installed: (none) Candidate: 3.8.0.19.35 Version table: 3.8.0.19.35 0 500 http://pt.archive.ubuntu.com/ubuntu/ raring/main i386 Packages

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