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• Running an allocation simulation repeatedly breaks after the first run.

  - by Az

  Background I have a bunch of students, their desired projects and the supervisors for the respective projects. I'm running a battery of simulations to see which projects the students end up with, which will allow me to get some useful statistics required for feedback. So, this is essentially a Monte-Carlo simulation where I'm randomising the list of students and then iterating through it, allocating projects until I hit the end of the list. Then the process is repeated again. Note that, within a single session, after each successful allocation of a project the following take place: + the project is set to allocated and cannot be given to another student + the supervisor has a fixed quota of students he can supervise. This is decremented by 1 + Once the quota hits 0, all the projects from that supervisor become blocked and this has the same effect as a project being allocated Code def resetData(): for student in students.itervalues(): student.allocated_project = None for supervisor in supervisors.itervalues(): supervisor.quota = 0 for project in projects.itervalues(): project.allocated = False project.blocked = False The role of resetData() is to "reset" certain bits of the data. For example, when a project is successfully allocated, project.allocated for that project is flipped to True. While that's useful for a single run, for the next run I need to be deallocated. Above I'm iterating through thee three dictionaries - one each for students, projects and supervisors - where the information is stored. The next bit is the "Monte-Carlo" simulation for the allocation algorithm. sesh_id = 1 for trial in range(50): for id in randomiseStudents(1): stud_id = id student = students[id] if not student.preferences: # Ignoring the students who've not entered any preferences for rank in ranks: temp_proj = random.choice(list(student.preferences[rank])) if not (temp_proj.allocated or temp_proj.blocked): alloc_proj = student.allocated_proj_ref = temp_proj.proj_id alloc_proj_rank = student.allocated_rank = rank successActions(temp_proj) temp_alloc = Allocated(sesh_id, stud_id, alloc_proj, alloc_proj_rank) print temp_alloc # Explained break sesh_id += 1 resetData() # Refer to def resetData() above All randomiseStudents(1) does is randomise the order of students. Allocated is a class defined as such: class Allocated(object): def __init__(self, sesh_id, stud_id, alloc_proj, alloc_proj_rank): self.sesh_id = sesh_id self.stud_id = stud_id self.alloc_proj = alloc_proj self.alloc_proj_rank = alloc_proj_rank def __repr__(self): return str(self) def __str__(self): return "%s - Student: %s (Project: %s - Rank: %s)" %(self.sesh_id, self.stud_id, self.alloc_proj, self.alloc_proj_rank) Output and problem Now if I run this I get an output such as this (truncated): 1 - Student: 7720 (Project: 1100241 - Rank: 1) 1 - Student: 7832 (Project: 1100339 - Rank: 1) 1 - Student: 7743 (Project: 1100359 - Rank: 1) 1 - Student: 7820 (Project: 1100261 - Rank: 2) 1 - Student: 7829 (Project: 1100270 - Rank: 1) . . . 1 - Student: 7822 (Project: 1100280 - Rank: 1) 1 - Student: 7792 (Project: 1100141 - Rank: 7) 2 - Student: 7739 (Project: 1100267 - Rank: 1) 3 - Student: 7806 (Project: 1100272 - Rank: 1) . . . 45 - Student: 7806 (Project: 1100272 - Rank: 1) 46 - Student: 7714 (Project: 1100317 - Rank: 1) 47 - Student: 7930 (Project: 1100343 - Rank: 1) 48 - Student: 7757 (Project: 1100358 - Rank: 1) 49 - Student: 7759 (Project: 1100269 - Rank: 1) 50 - Student: 7778 (Project: 1100301 - Rank: 1) Basically, it works perfectly for the first run, but on subsequent runs leading upto the nth run, in this case 50, only a single student-project allocation pair is returned. Thus, the main issue I'm having trouble with is figuring out what is causing this anomalous behaviour especially since the first run works smoothly. Thanks in advance, Az

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• Backbone.js Model change events in nested collections not firing as expected

  - by Pallavi Kaushik

  I'm trying to use backbone.js in my first "real" application and I need some help debugging why certain model change events are not firing as I would expect. I have a web service at /employees/{username}/tasks which returns a JSON array of task objects, with each task object nesting a JSON array of subtask objects. For example, [{ "id":45002, "name":"Open Dining Room", "subtasks":[ {"id":1,"status":"YELLOW","name":"Clean all tables"}, {"id":2,"status":"RED","name":"Clean main floor"}, {"id":3,"status":"RED","name":"Stock condiments"}, {"id":4,"status":"YELLOW","name":"Check / replenish trays"} ] },{ "id":47003, "name":"Open Registers", "subtasks":[ {"id":1,"status":"YELLOW","name":"Turn on all terminals"}, {"id":2,"status":"YELLOW","name":"Balance out cash trays"}, {"id":3,"status":"YELLOW","name":"Check in promo codes"}, {"id":4,"status":"YELLOW","name":"Check register promo placards"} ] }] Another web service allows me to change the status of a specific subtask in a specific task, and looks like this: /tasks/45002/subtasks/1/status/red [aside - I intend to change this to a HTTP Post-based service, but the current implementation is easier for debugging] I have the following classes in my JS app: Subtask Model and Subtask Collection var Subtask = Backbone.Model.extend({}); var SubtaskCollection = Backbone.Collection.extend({ model: Subtask }); Task Model with a nested instance of a Subtask Collection var Task = Backbone.Model.extend({ initialize: function() { // each Task has a reference to a collection of Subtasks this.subtasks = new SubtaskCollection(this.get("subtasks")); // status of each Task is based on the status of its Subtasks this.update_status(); }, ... }); var TaskCollection = Backbone.Collection.extend({ model: Task }); Task View to renders the item and listen for change events to the model var TaskView = Backbone.View.extend({ tagName: "li", template: $("#TaskTemplate").template(), initialize: function() { _.bindAll(this, "on_change", "render"); this.model.bind("change", this.on_change); }, ... on_change: function(e) { alert("task model changed!"); } }); When the app launches, I instantiate a TaskCollection (using the data from the first web service listed above), bind a listener for change events to the TaskCollection, and set up a recurring setTimeout to fetch() the TaskCollection instance. ... TASKS = new TaskCollection(); TASKS.url = ".../employees/" + username + "/tasks" TASKS.fetch({ success: function() { APP.renderViews(); } }); TASKS.bind("change", function() { alert("collection changed!"); APP.renderViews(); }); // Poll every 5 seconds to keep the models up-to-date. setInterval(function() { TASKS.fetch(); }, 5000); ... Everything renders as expected the first time. But at this point, I would expect either (or both) a Collection change event or a Model change event to get fired if I change a subtask's status using my second web service, but this does not happen. Funnily, I did get change events to fire if I added one additional level of nesting, with the web service returning a single object that has the Tasks Collection embedded, for example: "employee":"pkaushik", "tasks":[{"id":45002,"subtasks":[{"id":1..... But this seems klugey... and I'm afraid I haven't architected my app right. I'll include more code if it helps, but this question is already rather verbose. Thoughts?

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• Chaining CSS classes in IE6 - Trying to find a jQuery solution?

  - by Mike Baxter

  Right, perhaps I ask the impossible? I consider myself fairly new to Javscript and jQuery, but that being said, I have written some fairly complex code recently so I am definitely getting there... however I am now possed with a rather interesting issue at my current freelance contract. The previous web coder has taken a Grid-960 approach to the HTML and as a result has used chained classes to style many of the elements. The example below is typical of what can be found in the code: <div class='blocks four-col-1 orange highlight'>Some content</div> And in the css there will be different declarations for: (not actual css... but close enough) .blocks {margin-right:10px;} .orange {background-image:url(someimage.jpg);} .highlight {font-weight:bold;} .four-col-1 {width:300px;} and to make matters worse... this is in the CSS: .blocks.orange.highlight {background-colour:#dd00ff;} Anyone not familiar with this particular bug can read more on it here: http://www.ryanbrill.com/archives/multiple-classes-in-ie/ it is very real and very annoying. Without wanting to go into the merrits of not chaining classes (I told them this, but it is no longer feasible to change their approach... 100 hand coded pages into a 150 page website, no CMS... sigh) and without the luxury of being able to change the way these blocks are styled... can anyone advise me on the complexity and benefits between any of my below proposed approaches or possible other options that would adequately solve this problem. Potential Solution 1 Using conditional comments I am considering loading a jquery script only for IE6 that: Reads the class of all divs in a certain section of the page and pushes to an array creates empty boxes off screen with only one of the classes applied at a time Reads the applied CSS values for each box Re-applies these styles to the individual box, somehow bearing in mind the order in which they are called and overwriting conflicting instructions as required Potential Solution 2 read the class of all divs in a certain section of the page and push to an array Scan the document for links to style sheets Ajax grab the stylesheets and traverse looking for matching names to those in class array Apply styles as needed Potential Solution 3 Create an IE6 only stylesheet containing the exact style to be applied as a unique name (ie: class='blocks orange highlight' becomes class='blocks-orange-highlight') Traverse the document in IE6 and convert all spaces in class declarations to hyphens and reapply classes based on new style name Summary: Solution 1 allows the people at this company to apply any styles in the future and the script will adjust as needed. However it does not allow for the chained style to be added, only the individual style... it is also processor intensive and time consuming, but also the most likely to be converted into a plugin that could be used the world over Solution 2 is a potential nightmare to code. But again will allow for an endless number of updates without breaking Solution 3 will require someone at the companty to hardcode the new styles every time they make a change, and if they don't, IE6 will break. Ironically the site, whilst needing to conform to IE6 in a limited manner, does not need to run wihtout javascript (they've made the call... have JS or go away), so consider all jQuery and JS solutions to be 'game on'. Did I mention how much i hate IE6? Anyway... any thoughts or comments would be appreciated. I will continue to develop my own solution and if I discover one that can be turned into a jQuery plugin I will post it here in the comments. Regards, Mike.

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• How do I get a Java to call data from the Internet? Where to even start??

  - by cdg

  Hello oh great wizards of all things android. I really need your help. Mostly because my little brain just doesn't know were to start. I am trying to pull data from the internet to make a widget for the home screen. I have the layout built: <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/Layout" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@drawable/widget_bg_normal" android:clipChildren="false" > <TextView android:id="@+id/text_view" android:layout_width="100px" android:layout_height="wrap_content" android:paddingTop="18px" android:layout_centerHorizontal="true" android:textSize="8px" android:text="158x154 Image downloaded from the internet goes here. Needs to be updated every evening at midnight or unless the button below is pressed. Now if I could only figure out exactly how to do this, life would be good." /> <Button android:id="@+id/new_button" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="Get New" android:layout_below="@+id/scroll_image" android:layout_centerHorizontal="true" android:padding="0px" android:textSize="10px" android:height="8px" android:includeFontPadding="false" /> </RelativeLayout> Got the provider xml bulit: <?xml version="1.0" encoding="utf-8"?> <appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android" android:minWidth="150dip" android:minHeight="150dip" android:updatePeriodMillis="10000" android:initialLayout="@layout/widget" /> The Manifest works great. <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.dge.myandroid" android:versionCode="1" android:versionName="1.0"> <application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".myactivty" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <!-- Widget --> <receiver android:name=".mywidget" android:label="@string/app_name" > <intent-filter> <action android:name="android.appwidget.action.APPWIDGET_UPDATE" /> </intent-filter> <meta-data android:name="android.appwidget.widgetprovider" android:resource="@xml/widgetprovider" /> </receiver> <!-- Widget End --> </application> <uses-permission android:name="android.permission.INTERNET" /> <uses-sdk android:minSdkVersion="7" /> </manifest> The data it is calling looks something like this when it is called. It basically goes to a website that uses php to random the image: <html><body bgcolor="#000000">center> <a href="http://www.website.com" target="_blank"> <img border="0" src="http://www.webiste.com//0.gif"></a> <img src="http://www.webiste.com" style="border:none;" /> </center></body></html> But here is were I am stuck. I just don't know where to start at all. The java is so far beyond my little head that I don't know what to do. package com.dge.myandroid; import android.appwidget.AppWidgetProvider; public class mywidget extends AppWidgetProvider { } The wiki example just confused me more. I just don't know where to begin. Please help.

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• C#, AES encryption check!

  - by Data-Base

  I have this code for AES encryption, can some one verify that this code is good and not wrong? it works fine, but I'm more concern about the implementation of the algorithm // Plaintext value to be encrypted. //Passphrase from which a pseudo-random password will be derived. //The derived password will be used to generate the encryption key. //Password can be any string. In this example we assume that this passphrase is an ASCII string. //Salt value used along with passphrase to generate password. //Salt can be any string. In this example we assume that salt is an ASCII string. //HashAlgorithm used to generate password. Allowed values are: "MD5" and "SHA1". //SHA1 hashes are a bit slower, but more secure than MD5 hashes. //PasswordIterations used to generate password. One or two iterations should be enough. //InitialVector (or IV). This value is required to encrypt the first block of plaintext data. //For RijndaelManaged class IV must be exactly 16 ASCII characters long. //KeySize. Allowed values are: 128, 192, and 256. //Longer keys are more secure than shorter keys. //Encrypted value formatted as a base64-encoded string. public static string Encrypt(string PlainText, string Password, string Salt, string HashAlgorithm, int PasswordIterations, string InitialVector, int KeySize) { byte[] InitialVectorBytes = Encoding.ASCII.GetBytes(InitialVector); byte[] SaltValueBytes = Encoding.ASCII.GetBytes(Salt); byte[] PlainTextBytes = Encoding.UTF8.GetBytes(PlainText); PasswordDeriveBytes DerivedPassword = new PasswordDeriveBytes(Password, SaltValueBytes, HashAlgorithm, PasswordIterations); byte[] KeyBytes = DerivedPassword.GetBytes(KeySize / 8); RijndaelManaged SymmetricKey = new RijndaelManaged(); SymmetricKey.Mode = CipherMode.CBC; ICryptoTransform Encryptor = SymmetricKey.CreateEncryptor(KeyBytes, InitialVectorBytes); MemoryStream MemStream = new MemoryStream(); CryptoStream CryptoStream = new CryptoStream(MemStream, Encryptor, CryptoStreamMode.Write); CryptoStream.Write(PlainTextBytes, 0, PlainTextBytes.Length); CryptoStream.FlushFinalBlock(); byte[] CipherTextBytes = MemStream.ToArray(); MemStream.Close(); CryptoStream.Close(); return Convert.ToBase64String(CipherTextBytes); } public static string Decrypt(string CipherText, string Password, string Salt, string HashAlgorithm, int PasswordIterations, string InitialVector, int KeySize) { byte[] InitialVectorBytes = Encoding.ASCII.GetBytes(InitialVector); byte[] SaltValueBytes = Encoding.ASCII.GetBytes(Salt); byte[] CipherTextBytes = Convert.FromBase64String(CipherText); PasswordDeriveBytes DerivedPassword = new PasswordDeriveBytes(Password, SaltValueBytes, HashAlgorithm, PasswordIterations); byte[] KeyBytes = DerivedPassword.GetBytes(KeySize / 8); RijndaelManaged SymmetricKey = new RijndaelManaged(); SymmetricKey.Mode = CipherMode.CBC; ICryptoTransform Decryptor = SymmetricKey.CreateDecryptor(KeyBytes, InitialVectorBytes); MemoryStream MemStream = new MemoryStream(CipherTextBytes); CryptoStream cryptoStream = new CryptoStream(MemStream, Decryptor, CryptoStreamMode.Read); byte[] PlainTextBytes = new byte[CipherTextBytes.Length]; int ByteCount = cryptoStream.Read(PlainTextBytes, 0, PlainTextBytes.Length); MemStream.Close(); cryptoStream.Close(); return Encoding.UTF8.GetString(PlainTextBytes, 0, ByteCount); } Thank you

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• Openlayers - LayerRedraw() / Feature rotation / Linestring coords

  - by Ozaki

  TLDR: I have an Openlayers map with a layer called 'track' I want to remove track and add track back in. Or figure out how to plot a triangle based off one set of coords & a heading(see below). I have an image 'imageFeature' on a layer that rotates on load to the direction being set. I want it to update this rotation that is set in 'styleMap' on a layer called 'tracking'. I set the var 'stylemap' to apply the external image & rotation. The 'imageFeature' is added to the layer at the coords specified. 'imageFeature' is removed. 'imageFeature' is added again in its new location. Rotation is not applied.. As the 'styleMap' applies to the layer I think that I have to remove the layer and add it again rather than just the 'imageFeature' Layer: var tracking = new OpenLayers.Layer.GML("Tracking", "coordinates.json", { format: OpenLayers.Format.GeoJSON, styleMap: styleMap }); styleMap: var styleMap = new OpenLayers.StyleMap({ fillOpacity: 1, pointRadius: 10, rotation: heading, }); Now wrapped in a timed function the imageFeature: map.layers[3].addFeatures(new OpenLayers.Feature.Vector( new OpenLayers.Geometry.Point(longitude, latitude), {rotation: heading, type: parseInt(Math.random() * 3)} )); Type refers to a lookup of 1 of 3 images.: styleMap.addUniqueValueRules("default", "type", lookup); var lookup = { 0: {externalGraphic: "Image1.png", rotation: heading}, 1: {externalGraphic: "Image2.png", rotation: heading}, 2: {externalGraphic: "Image3.png", rotation: heading} } I have tried the 'redraw()' function: but it returns "tracking is undefined" or "map.layers[2]" is undefined. tracking.redraw(true); map.layers[2].redraw(true); Heading is a variable: from a JSON feed. var heading = 13.542; But so far can't get anything to work it will only rotate the image onload. The image will move in coordinates as it should though. So what am I doing wrong with the redraw function or how can I get this image to rotate live? Thanks in advance -Ozaki Add: I managed to get map.layers[2].redraw(true); to sucessfully redraw layer 2. But it still does not update the rotation. I am thinking because the stylemap is updating. But it runs through the style map every n sec, but no updates to rotation and the variable for heading is updating correctly if i put a watch on it in firebug. If I were to draw a triangle with an array of points & linestring. How would I go about facing the triangle towards the heading. I have the Lon/lat of one point and the heading. var points = new Array( new OpenLayers.Geometry.Point(lon1, lat1), new OpenLayers.Geometry.Point(lon2, lat2), new OpenLayers.Geometry.Point(lon3, lat3) ); var line = new OpenLayers.Geometry.LineString(points); Looking for any way to solve this problem Image or Line anyone know how to do either added a 100rep bounty I am really stuck with this.

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• jQuery Validation hiding or tearing down jquery Modal Dialog on submit

  - by Programmin Tool

  Basically when clicking the modal created submit button, and calling jQuery('#FormName').submit(), it will run the validation and then call the method assigned in the submitHandler. After that it is either creating a new modal div or hiding the form, and I don't get why. I have debugged it and noticed that after the method call in the submitHandler, the form .is(':hidden') = true and this is true for the modal div also. I'm positive I've done this before but can't seem to figure out what I've done wrong this time. The odd this is a modal div is showing up on the screen, but it's completely devoid of content. (Even after putting in random text outside of the form. It's like it's a whole new modal div) Here are the set up methods: function setUpdateTaskDiv() { jQuery("#UpdateTaskForm").validate({ errorLabelContainer: "#ErrorDiv", wrapper: "div", rules: { TaskSubject: { required: true } }, messages: { TaskSubject: { required: 'Subject is required.' } }, onfocusout: false, onkeyup: false, submitHandler: function(label) { updateTaskSubject(null); } } ); jQuery('#UpdateDiv').dialog({ autoOpen: false, bgiframe: true, height: 400, width: 500, modal: true, beforeclose: function() { }, buttons: { Submit: function() { jQuery('#UpdateTaskForm').submit(); }, Cancel: function() { ... } } }); where: function updateTaskSubject(task) { //does nothing, it's just a shell right now } Doesn't really do anything right now. Here's the html: <div id="UpdateDiv"> <div id="ErrorDiv"> </div> <form method="post" id="UpdateTaskForm" action="Calendar.html"> <div> <div class="floatLeft"> Date: </div> <div class="floatLeft"> </div> <div class="clear"> </div> </div> <div> <div class="floatLeft"> Start Time: </div> <div class="floatLeft"> <select id="TaskStartDate" name="TaskStartDate"> </select> </div> <div class="clear"> </div> </div> <div> <div class="floatLeft"> End Time: </div> <div class="floatLeft"> <select id="TaskEndDate" name="TaskEndDate"> </select> </div> <div class="clear"> </div> </div> <div> <div class="floatLeft"> Subject: </div> <div class="floatLeft"> <textarea id="TaskSubject" name="TaskSubject" cols="30" rows="10"></textarea> </div> <div class="clear"> </div> </div> <div> <input type="hidden" id="TaskId" value="" /> </div> <div class="clear"></div> </form> </div> Odd Discovery Turns out that the examples that I got this to work all had the focus being put back on the modal itself. For example, using the validator to add messages to the error div. (Success or not) Without doing this, the modal dialog apparently thinks that it's done with what it needs to do and just hides everything. Not sure exactly why, but to stop this behavior some kind of focus has to be assigned to something within the div itself.

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• Can someone explain the "use-cases" for the default munin graphs?

  - by exhuma

  When installing munin, it activates a default set of plugins (at least on ubuntu). Alternatively, you can simply run munin-node-configure to figure out which plugins are supported on your system. Most of these plugins plot straight-forward data. My question is not to explain the nature of the data (well... maybe for some) but what is it that you look for in these graphs? It is easy to install munin and see fancy graphs. But having the graphs and not being able to "read" them renders them totally useless. I am going to list standard plugins which are enabled by default on my system. So it's going to be a long list. For completeness, I am also going to list plugins which I think to understand and give a short explanation as to what I think it's used for. Pleas correct if I am wrong with any of them. So let me split this questions in three parts: Plugins where I don't even understand the data Plugins where I understand the data but don't know what I should look out for Plugins which I think to understand Plugins where I don't even understand the data These may contain questions that are not necessarily aimed at munin alone. Not understanding the data usually mean a gap in fundamental knowledge on operating systems/hardware.... ;) Feel free to respond with a "giyf" answer. These are plugins where I can only guess what's going on... I hardly want to look at these "guessing"... Disk IOs per device (IOs/second)What's an IO. I know it stands for input/output. But that's as far as it goes. Disk latency per device (Average IO wait)Not a clue what an "IO wait" is... IO Service TimeThis one is a huge mess, and it's near impossible to see something in the graph at all. Plugins where I understand the data but don't know what I should look out for IOStat (blocks/second read/written)I assume, the thing to look out for in here are spikes? Which would mean that the device is in heavy use? Available entropy (bytes)I assume that this is important for random number generation? Why would I graph this? So far the value has always been near constant. VMStat (running/I/O sleep processes)What's the difference between this one and the "processes" graph? Both show running/sleeping processes, whereas the "Processes" graph seems to have more details. Disk throughput per device (bytes/second read/written) What's thedifference between this one and the "IOStat" graph? inode table usageWhat should I look for in this graph? Plugins which I think to understand I'll be guessing some things here... correct me if I am wrong. Disk usage in percent (percent)How much disk space is used/remaining. As this is approaching 100%, you should consider cleaning up or extend the partition. This is extremely important for the root partition. Firewall Throughput (packets/second)The number of packets passing through the firewall. If this is spiking for a longer period of time, it could be a sign of a DOS attack (or we are simply recieving a large file). It can also give you an idea about your firewall performance. If it's levelling out and you need more "power" you should consider load balancing. If it's levelling out and see a correlation with your CPU load, it could also mean that your hardware is not fast enough. Correlations with disk usage could point to excessive LOG targets in you FW config. eth0 errors (packets in/out)Network errors. If this value is increasing, it could be a sign of faulty hardware. eth0 traffic (bits/second in/out)Raw network traffic. This should correlate with Firewall throughput. number of threadsAn ever-increasing value might point to a process not properly closing threads. Investigate! processesBreakdown of active processes (including sleeping). A quick spike in here might point to a fork-bomb. A slowly, but ever-increasing value might point to an application spawning sub-processes but not properly closing them. Investigate using ps faux. process priorityThis shows the distribution of process priorities. Having only high-priority processes is not of much use. Consider de-prioritizing some. cpu usageFairly straight-forward. If this is spiking, you may have an attack going on, or a process is hogging the CPU. Idf it's slowly increasing and approaching max in normal operations, you should consider upgrading your hardware (or load-balancing). file table usageNumber of actively open files. If this is reaching max, you may have a process opening, but not properly releasing files. load averageShows an summarized value for the system load. Should correlate with CPU usage. Increasing values can come from a number of sources. Look for correlations with other graphs. memory usageA graphical representation of you memory. As long as you have a lot of unused+cache+buffers you are fine. swap in/outShows the activity on your swap partition. This should always be 0. If you see activity on this, you should add more memory to your machine!

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• iPhone Memory Error - when using Build & Debug, How to debug?

  - by LonH99

  I'm a newbie and need some help with an iPhone App running on the Simulator. The app works fine running with Build & Run or Build & Run - breakpoints off, but blows when running with Build & Debug - Breakpoints on. Any help or thoughts would be greatly appreciated. Lon Specifics: No breakpoints set, never gets to any visible simulator results, seems to blow during initialization phase before it can generate any output. Source of app is the DrinkMixer example, in the "Head First iPhone development" book (example built up to page 280) by Dan & Tracey Pilone. Blows With this Error Message: Attaching to process 970. Pending breakpoint 1 - "*0x01c1b001" resolved Program received signal: “EXC_BAD_ACCESS”. No memory available to program now: unsafe to call malloc Data Formatters temporarily unavailable, will re-try after a 'continue'. (Not safe to call dlopen at this time.) No memory available to program now: unsafe to call malloc --- Leaks: The only object noted as "leaked Object" is: Leaked Object # Address Size Responsible Library Responsible Frame Malloc 128 Bytes <blank> 0x3c11950 128Bytes CoreGraphics open_handle_to_dylib_path ___ Object Allocations shows (Highest at top = CFString): Category --- Overall Bytes -- #Overall -- Live Bytes -- #Living * All Allocations * 497kb #5888 496kb #5878 10 CFString 42kb #1126 42kb Malloc 32.00 KB 32kb #1 32kb Malloc 1.00 KB 29kb #29 29kb Malloc 8.00 KB 24kb #3 24kb Malloc 32 Bytes 20.81kb #666 20.75kb Malloc 1.50 KB 19.5kb #13 19.5kb CFDictionary (key-store) 17.64kb #159 17.64kb (note: Except for "All Allocations, the #Living is the same as #Overall) --- List of Calls from Debugger: #0 0x01c1b010 in CFStringCreateByCombiningStrings #1 0x023a0779 in LoadFontPathCache #2 0x023a096b in Initialize #3 0x023a0f3e in GSFontCreateWithName #4 0x003d4575 in +[UIFont boldSystemFontOfSize:] #5 0x002cddaa in +[UINavigationButton defaultFont] #6 0x002d9e37 in -[UINavigationButton initWithValue:width:style:barStyle:possibleTitles:tintColor:] #7 0x002cdc75 in -[UINavigationButton initWithImage:width:style:] #8 0x00468eeb in -[UIBarButtonItem(Static) createViewForNavigationItem:] #9 0x002d1b56 in -[UINavigationItem customRightView] #10 0x002d20e3 in -[UINavigationItem updateNavigationBarButtonsAnimated:] #11 0x002d1e1a in -[UINavigationItem setRightBarButtonItem:] #12 0x00002e7b in -[RootViewController viewDidLoad] at RootViewController.m:41 #13 0x00313796 in -[UIViewController view] #14 0x00311d92 in -[UIViewController contentScrollView] #15 0x0031c2b4 in -[UINavigationController _computeAndApplyScrollContentInsetDeltaForViewController:] #16 0x0031b32e in -[UINavigationController _layoutViewController:] #17 0x0031cd1a in -[UINavigationController _startTransition:fromViewController:toViewController:] #18 0x0031831a in -[UINavigationController _startDeferredTransitionIfNeeded] #19 0x004362e4 in -[UILayoutContainerView layoutSubviews] #20 0x035342b0 in -[CALayer layoutSublayers] #21 0x0353406f in CALayerLayoutIfNeeded #22 0x035338c6 in CA::Context::commit_transaction #23 0x0353353a in CA::Transaction::commit #24 0x00295ef9 in -[UIApplication _reportAppLaunchFinished] #25 0x0029bb88 in -[UIApplication handleEvent:withNewEvent:] #26 0x002976d3 in -[UIApplication sendEvent:] #27 0x0029e0b5 in _UIApplicationHandleEvent #28 0x023a3ed1 in PurpleEventCallback #29 0x01bb6b80 in CFRunLoopRunSpecific #30 0x01bb5c48 in CFRunLoopRunInMode #31 0x00295e69 in -[UIApplication _run] #32 0x0029f003 in UIApplicationMain #33 0x00002ba0 in main at main.m:14 The code, including line #41 (noted below) is as follows. And thanks for the formatting help and comment: import "RootViewController.h" import "DrinkDetailViewController.h"; import "DrinkConstants.h" import "AddDrinkViewController.h" @implementation RootViewController @synthesize drinks, addButtonItem; - (void)viewDidLoad { [super viewDidLoad]; // add PATH for PLIST NSString *path = [[NSBundle mainBundle] pathForResource: @"DrinkDirections" ofType:@"plist"]; NSMutableArray *tmpArray = [[NSMutableArray alloc] initWithContentsOfFile:path]; self.drinks = tmpArray; [tmpArray release]; // Next is Line #41 - I removed earlier empty lines & Comments self.navigationItem.rightBarButtonItem = self.addButtonItem; } - (IBAction) addButtonPressed: (id) sender { NSLog(@"Add button pressed!");

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• Error data: line 2 column 1 when using pycurl with gzip stream

  - by Sagar Hatekar

  Thanks for reading. Background: I am trying to read a streaming API feed that returns data in JSON format, and then storing this data to a pymongo collection. The streaming API requires a "Accept-Encoding" : "Gzip" header. What's happening: Code fails on json.loads and outputs - Extra data: line 2 column 1 - line 4 column 1 (char 1891 - 5597) (Refer Error Log below) This does NOT happen while parsing every JSON object - it happens at random. My guess is I am encountering some weird JSON object after every "x" proper JSON objects. I did reference how to use pycurl if requested data is sometimes gzipped, sometimes not? and Encoding error while deserializing a json object from Google but so far have been unsuccessful at resolving this error. Could someone please help me out here? Error Log: Note: The raw dump of the JSON object below is basically using the repr() method. '{"id":"tag:search.twitter.com,2005:207958320747782146","objectType":"activity","actor":{"objectType":"person","id":"id:twitter.com:493653150","link":"http://www.twitter.com/Deathnews_7_24","displayName":"Death News 7/24","postedTime":"2012-02-16T01:30:12.000Z","image":"http://a0.twimg.com/profile_images/1834408513/deathnewstwittersquare_normal.jpg","summary":"Crashes, Murders, Suicides, Accidents, Crime and Naturals Death News From All Around World","links":[{"href":"http://www.facebook.com/DeathNews724","rel":"me"}],"friendsCount":56,"followersCount":14,"listedCount":1,"statusesCount":1029,"twitterTimeZone":null,"utcOffset":null,"preferredUsername":"Deathnews_7_24","languages":["tr"]},"verb":"post","postedTime":"2012-05-30T22:15:02.000Z","generator":{"displayName":"web","link":"http://twitter.com"},"provider":{"objectType":"service","displayName":"Twitter","link":"http://www.twitter.com"},"link":"http://twitter.com/Deathnews_7_24/statuses/207958320747782146","body":"Kathi Kamen Goldmark, Writers\xe2\x80\x99 Catalyst, Dies at 63 http://t.co/WBsNlNtA","object":{"objectType":"note","id":"object:search.twitter.com,2005:207958320747782146","summary":"Kathi Kamen Goldmark, Writers\xe2\x80\x99 Catalyst, Dies at 63 http://t.co/WBsNlNtA","link":"http://twitter.com/Deathnews_7_24/statuses/207958320747782146","postedTime":"2012-05-30T22:15:02.000Z"},"twitter_entities":{"urls":[{"display_url":"nytimes.com/2012/05/30/boo\xe2\x80\xa6","indices":[52,72],"expanded_url":"http://www.nytimes.com/2012/05/30/books/kathi-kamen-goldmark-writers-catalyst-dies-at-63.html","url":"http://t.co/WBsNlNtA"}],"hashtags":[],"user_mentions":[]},"gnip":{"language":{"value":"en"},"matching_rules":[{"value":"url_contains: nytimes.com","tag":null}],"klout_score":11,"urls":[{"url":"http://t.co/WBsNlNtA","expanded_url":"http://www.nytimes.com/2012/05/30/books/kathi-kamen-goldmark-writers-catalyst-dies-at-63.html?_r=1"}]}}\r\n{"id":"tag:search.twitter.com,2005:207958321003638785","objectType":"activity","actor":{"objectType":"person","id":"id:twitter.com:178760897","link":"http://www.twitter.com/Mobanu","displayName":"Donald Ochs","postedTime":"2010-08-15T16:33:56.000Z","image":"http://a0.twimg.com/profile_images/1493224811/small_mobany_Logo_normal.jpg","summary":"","links":[{"href":"http://www.mobanuweightloss.com","rel":"me"}],"friendsCount":10272,"followersCount":9698,"listedCount":30,"statusesCount":725,"twitterTimeZone":"Mountain Time (US & Canada)","utcOffset":"-25200","preferredUsername":"Mobanu","languages":["en"],"location":{"objectType":"place","displayName":"Crested Butte, Colorado"}},"verb":"post","postedTime":"2012-05-30T22:15:02.000Z","generator":{"displayName":"twitterfeed","link":"http://twitterfeed.com"},"provider":{"objectType":"service","displayName":"Twitter","link":"http://www.twitter.com"},"link":"http://twitter.com/Mobanu/statuses/207958321003638785","body":"Mobanu: Can Exercise Be Bad for You?: Researchers have found evidence that some people who exercise do worse on ... http://t.co/mTsQlNQO","object":{"objectType":"note","id":"object:search.twitter.com,2005:207958321003638785","summary":"Mobanu: Can Exercise Be Bad for You?: Researchers have found evidence that some people who exercise do worse on ... http://t.co/mTsQlNQO","link":"http://twitter.com/Mobanu/statuses/207958321003638785","postedTime":"2012-05-30T22:15:02.000Z"},"twitter_entities":{"urls":[{"display_url":"nyti.ms/KUmmMa","indices":[116,136],"expanded_url":"http://nyti.ms/KUmmMa","url":"http://t.co/mTsQlNQO"}],"hashtags":[],"user_mentions":[]},"gnip":{"language":{"value":"en"},"matching_rules":[{"value":"url_contains: nytimes.com","tag":null}],"klout_score":12,"urls":[{"url":"http://t.co/mTsQlNQO","expanded_url":"http://well.blogs.nytimes.com/2012/05/30/can-exercise-be-bad-for-you/?utm_medium=twitter&utm_source=twitterfeed"}]}}\r\n' json exception: Extra data: line 2 column 1 - line 4 column 1 (char 1891 - 5597) Header Output: HTTP/1.1 200 OK Content-Type: application/json; charset=UTF-8 Vary: Accept-Encoding Date: Wed, 30 May 2012 22:14:48 UTC Connection: close Transfer-Encoding: chunked Content-Encoding: gzip get_stream.py: #!/usr/bin/env python import sys import pycurl import json import pymongo STREAM_URL = "https://stream.test.com:443/accounts/publishers/twitter/streams/track/Dev.json" AUTH = "userid:passwd" DB_HOST = "127.0.0.1" DB_NAME = "stream_test" class StreamReader: def __init__(self): try: self.count = 0 self.buff = "" self.mongo = pymongo.Connection(DB_HOST) self.db = self.mongo[DB_NAME] self.raw_tweets = self.db["raw_tweets_gnip"] self.conn = pycurl.Curl() self.conn.setopt(pycurl.ENCODING, 'gzip') self.conn.setopt(pycurl.URL, STREAM_URL) self.conn.setopt(pycurl.USERPWD, AUTH) self.conn.setopt(pycurl.WRITEFUNCTION, self.on_receive) self.conn.setopt(pycurl.HEADERFUNCTION, self.header_rcvd) while True: self.conn.perform() except Exception as ex: print "error ocurred : %s" % str(ex) def header_rcvd(self, header_data): print header_data def on_receive(self, data): temp_data = data self.buff += data if data.endswith("\r\n") and self.buff.strip(): try: tweet = json.loads(self.buff, encoding = 'UTF-8') self.buff = "" if tweet: try: self.raw_tweets.insert(tweet) except Exception as insert_ex: print "Error inserting tweet: %s" % str(insert_ex) self.count += 1 if self.count % 10 == 0: print "inserted "+str(self.count)+" tweets" except Exception as json_ex: print "json exception: %s" % str(json_ex) print repr(temp_data) stream = StreamReader()

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• matplotlib and python multithread file processing

  - by Napseis

  I have a large number of files to process. I have written a script that get, sort and plot the datas I want. So far, so good. I have tested it and it gives the desired result. Then I wanted to do this using multithreading. I have looked into the doc and examples on the internet, and using one thread in my program works fine. But when I use more, at some point I get random matplotlib error, and I suspect some conflict there, even though I use a function with names for the plots, and iI can't see where the problem could be. Here is the whole script should you need more comment, i'll add them. Thank you. #!/usr/bin/python import matplotlib matplotlib.use('GTKAgg') import numpy as np from scipy.interpolate import griddata import matplotlib.pyplot as plt import matplotlib.colors as mcl from matplotlib import rc #for latex import time as tm import sys import threading import Queue #queue in 3.2 and Queue in 2.7 ! import pdb #the debugger rc('text', usetex=True)#for latex map=0 #initialize the map index. It will be use to index the array like this: array[map,[x,y]] time=np.zeros(1) #an array to store the time middle_h=np.zeros((0,3)) #x phi c #for the middle of the box current_file=open("single_void_cyl_periodic_phi_c_middle_h_out",'r') for line in current_file: if line.startswith('# === time'): map+=1 np.append(time,[float(line.strip('# === time '))]) elif line.startswith('#'): pass else: v=np.fromstring(line,dtype=float,sep=' ') middle_h=np.vstack( (middle_h,v[[1,3,4]]) ) current_file.close() middle_h=middle_h.reshape((map,-1,3)) #3d array: map, x, phi,c ##### def load_and_plot(): #will load a map file, and plot it along with the corresponding profile loaded before while not exit_flag: print("fecthing work ...") #try: if not tasks_queue.empty(): map_index=tasks_queue.get() print("----> working on map: %s" %map_index) x,y,zp=np.loadtxt("single_void_cyl_growth_periodic_post_map_"+str(map_index),unpack=True, usecols=[1, 2,3]) for i,el in enumerate(zp): if el<0.: zp[i]=0. xv=np.unique(x) yv=np.unique(y) X,Y= np.meshgrid(xv,yv) Z = griddata((x, y), zp, (X, Y),method='nearest') figure=plt.figure(num=map_index,figsize=(14, 8)) ax1=plt.subplot2grid((2,2),(0,0)) ax1.plot(middle_h[map_index,:,0],middle_h[map_index,:,1],'*b') ax1.grid(True) ax1.axis([-15, 15, 0, 1]) ax1.set_title('Profiles') ax1.set_ylabel(r'$\phi$') ax1.set_xlabel('x') ax2=plt.subplot2grid((2,2),(1,0)) ax2.plot(middle_h[map_index,:,0],middle_h[map_index,:,2],'*r') ax2.grid(True) ax2.axis([-15, 15, 0, 1]) ax2.set_ylabel('c') ax2.set_xlabel('x') ax3=plt.subplot2grid((2,2),(0,1),rowspan=2,aspect='equal') sub_contour=ax3.contourf(X,Y,Z,np.linspace(0,1,11),vmin=0.) figure.colorbar(sub_contour,ax=ax3) figure.savefig('single_void_cyl_'+str(map_index)+'.png') plt.close(map_index) tasks_queue.task_done() else: print("nothing left to do, other threads finishing,sleeping 2 seconds...") tm.sleep(2) # except: # print("failed this time: %s" %map_index+". Sleeping 2 seconds") # tm.sleep(2) ##### exit_flag=0 nb_threads=2 tasks_queue=Queue.Queue() threads_list=[] jobs=list(range(map)) #each job is composed of a map print("inserting jobs in the queue...") for job in jobs: tasks_queue.put(job) print("done") #launch the threads for i in range(nb_threads): working_bee=threading.Thread(target=load_and_plot) working_bee.daemon=True print("starting thread "+str(i)+' ...') threads_list.append(working_bee) working_bee.start() #wait for all tasks to be treated tasks_queue.join() #flip the flag, so the threads know it's time to stop exit_flag=1 for t in threads_list: print("waiting for threads %s to stop..."%t) t.join() print("all threads stopped")

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• Why are my USB 2.0 devices hanging Windows XP?

  - by BenAlabaster

  Background on the machine I'm having a problem with: The machine was inherited and appears to be circa 2003 (there's a date stamp on the power supply which leads me to this conclusion). I've got it set up as a Skype terminal for my 2 year old to keep in touch with her grandparents and other members of the family - which everyone loves. It has a DFI CM33-TL/G ATX (identified using SiSoft Sandra) motherboard hosting an Intel Celeron 1.3GHz CPU, 768Mb PC133 SDRAM, a D-LINK WDA-2320 54G Wi-Fi network card and a generic USB 2.0 expansion board based on the NEC uPD720102 chipset containing 3 external and 1 internal USB sockets. It's also hosting a 1.44Mb floppy drive on FDD0, a new 80Gb Western Digital hard drive running as master on IDE0 and a Panasonic DVD+/-RW running as master on IDE1. All this is sitting in a slimline case running off a Macron Power MPT-135 135W Flex power supply. The motherboard is running a version of Award BIOS 05/24/2002-601T-686B-6A6LID4AC-00. Could this be updated? If so, from where? I've raked through the manufacturer's website but can't find any hint of downloads for either drivers or BIOS updates. The hard disk is freshly formatted and built with Windows XP Professional/Service Pack 3 and is up to date with all current patches. In addition to Windows XP, the only other software it's running is Skype 4.1 (4.2 hangs the whole machine as soon as it starts up, requiring a hard boot to recover). It's got a Daytek MV150 15" touch screen hooked up to the on board VGA and COM1 sockets with the most current drivers from the Daytek website and the most current version of ELO-Touchsystems drivers for the touch component. The webcam is a Logitech Webcam C200 with the latest drivers from the Logitech website. The problem: If I hook any devices to the USB 2.0 sockets, it hangs the whole machine and I have to hard boot it to get it back up. If I have any devices attached to the USB 2.0 sockets when I boot up, it hangs before Windows gets to the login prompt and I have to hard boot it to recover. Workarounds found: I can plug the same devices into the on board USB 1.0 sockets and everything works fine, albeit at reduced performance. I've tried 3 different kinds of USB thumb drives, 3 different makes/models of webcams and my iPhone all with the same effect. They're recognized and don't hang the machine when I hook them to the USB 1.0 but if I hook them to the USB 2.0 ports, the machine hangs within a couple of seconds of recognizing the devices were connected. Attempted solutions: I've seen suggestions that this could be a power problem - that the PSU just doesn't have the wattage to drive these ports. While I'm doubtful this is the problem [after all the motherboard has the same standard connector regardless of the PSU wattage], I tried disabling all the on board devices that I'm not using - on board LAN, the second COM port, the AGP connector etc. through the BIOS in what I'm sure is a futile attempt to reduce the power consumption... I also modified the ACPI and power management settings. It didn't have any noticeable affect, although it didn't do any harm either. Could the wattage of the PSU really cause this problem? If it can, is there anything I need to be aware of when replacing it or do I just need to make sure it's got a higher wattage than the current one? My interpretation was that the wattage only affected the number of drives you could hook up to the power connectors, is that right? I've installed the USB card in another machine and it works without issue, so it's not a problem with the USB card itself, and Windows says the card is installed and working correctly... right up until I connect a device to it. The only thing I haven't done which I only just thought of while writing this essay is trying the USB 2.0 card in a different PCI slot, or re-ordering the wi-fi and USB cards in the slots... although I'm not sure if this will make any difference - does anyone have any experience that would suggest this might work? Other thoughts/questions: Perhaps this is an incompatibility between the USB 2.0 card and the BIOS, would re-flashing the BIOS with a newer version help? Do I need to be able to identify the manufacturer of the motherboard in order to be able to find a BIOS edition specific for this motherboard or will any version of Award BIOS function in its place? Question: Does anyone have any ideas that could help me get my USB 2.0 devices hooked up to this machine?

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• Domain Validation in a CQRS architecture

  - by Jupaol

  Basically I want to know if there is a better way to validate my domain entities. This is how I am planning to do it but I would like your opinion The first approach I considered was: class Customer : EntityBase<Customer> { public void ChangeEmail(string email) { if(string.IsNullOrWhitespace(email)) throw new DomainException(“...”); if(!email.IsEmail()) throw new DomainException(); if(email.Contains(“@mailinator.com”)) throw new DomainException(); } } I actually do not like this validation because even when I am encapsulating the validation logic in the correct entity, this is violating the Open/Close principle (Open for extension but Close for modification) and I have found that violating this principle, code maintenance becomes a real pain when the application grows up in complexity. Why? Because domain rules change more often than we would like to admit, and if the rules are hidden and embedded in an entity like this, they are hard to test, hard to read, hard to maintain but the real reason why I do not like this approach is: if the validation rules change, I have to come and edit my domain entity. This has been a really simple example but in RL the validation could be more complex So following the philosophy of Udi Dahan, making roles explicit, and the recommendation from Eric Evans in the blue book, the next try was to implement the specification pattern, something like this class EmailDomainIsAllowedSpecification : IDomainSpecification<Customer> { private INotAllowedEmailDomainsResolver invalidEmailDomainsResolver; public bool IsSatisfiedBy(Customer customer) { return !this.invalidEmailDomainsResolver.GetInvalidEmailDomains().Contains(customer.Email); } } But then I realize that in order to follow this approach I had to mutate my entities first in order to pass the value being valdiated, in this case the email, but mutating them would cause my domain events being fired which I wouldn’t like to happen until the new email is valid So after considering these approaches, I came out with this one, since I am going to implement a CQRS architecture: class EmailDomainIsAllowedValidator : IDomainInvariantValidator<Customer, ChangeEmailCommand> { public void IsValid(Customer entity, ChangeEmailCommand command) { if(!command.Email.HasValidDomain()) throw new DomainException(“...”); } } Well that’s the main idea, the entity is passed to the validator in case we need some value from the entity to perform the validation, the command contains the data coming from the user and since the validators are considered injectable objects they could have external dependencies injected if the validation requires it. Now the dilemma, I am happy with a design like this because my validation is encapsulated in individual objects which brings many advantages: easy unit test, easy to maintain, domain invariants are explicitly expressed using the Ubiquitous Language, easy to extend, validation logic is centralized and validators can be used together to enforce complex domain rules. And even when I know I am placing the validation of my entities outside of them (You could argue a code smell - Anemic Domain) but I think the trade-off is acceptable But there is one thing that I have not figured out how to implement it in a clean way. How should I use this components... Since they will be injected, they won’t fit naturally inside my domain entities, so basically I see two options: Pass the validators to each method of my entity Validate my objects externally (from the command handler) I am not happy with the option 1 so I would explain how I would do it with the option 2 class ChangeEmailCommandHandler : ICommandHandler<ChangeEmailCommand> { public void Execute(ChangeEmailCommand command) { private IEnumerable<IDomainInvariantValidator> validators; // here I would get the validators required for this command injected, and in here I would validate them, something like this using (var t = this.unitOfWork.BeginTransaction()) { var customer = this.unitOfWork.Get<Customer>(command.CustomerId); this.validators.ForEach(x =. x.IsValid(customer, command)); // here I know the command is valid // the call to ChangeEmail will fire domain events as needed customer.ChangeEmail(command.Email); t.Commit(); } } } Well this is it. Can you give me your thoughts about this or share your experiences with Domain entities validation EDIT I think it is not clear from my question, but the real problem is: Hiding the domain rules has serious implications in the future maintainability of the application, and also domain rules change often during the life-cycle of the app. Hence implementing them with this in mind would let us extend them easily. Now imagine in the future a rules engine is implemented, if the rules are encapsulated outside of the domain entities, this change would be easier to implement

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• Why doesn't my implementation of ElGamal work for long text strings?

  - by angstrom91

  I'm playing with the El Gamal cryptosystem, and my goal is to be able to encipher and decipher long sequences of text. I have come up with a method that works for short sequences, but does not work for long sequences, and I cannot figure out why. El Gamal requires the plaintext to be an integer. I have turned my string into a byte[] using the .getBytes() method for Strings, and then created a BigInteger out of the byte[]. After encryption/decryption, I turn the BigInteger into a byte[] using the .toByteArray() method for BigIntegers, and then create a new String object from the byte[]. This works perfectly when i call ElGamalEncipher with strings up to 129 characters. With 130 or more characters, the output produced from ElGamalDecipher is garbled. Can someone suggest how to solve this issue? Is this an issue with my method of turning the string into a BigInteger? If so, is there a better way to turn my string of text into a BigInteger and back? Below is my encipher/decipher code with a program to demonstrate the problem. import java.math.BigInteger; public class Main { static BigInteger P = new BigInteger("15893293927989454301918026303382412" + "2586402937727056707057089173871237566896685250125642378268385842" + "6917261652781627945428519810052550093673226849059197769795219973" + "9423619267147615314847625134014485225178547696778149706043781174" + "2873134844164791938367765407368476144402513720666965545242487520" + "288928241768306844169"); static BigInteger G = new BigInteger("33234037774370419907086775226926852" + "1714093595439329931523707339920987838600777935381196897157489391" + "8360683761941170467795379762509619438720072694104701372808513985" + "2267495266642743136795903226571831274837537691982486936010899433" + "1742996138863988537349011363534657200181054004755211807985189183" + "22832092343085067869"); static BigInteger R = new BigInteger("72294619754760174015019300613282868" + "7219874058383991405961870844510501809885568825032608592198728334" + "7842806755320938980653857292210955880919036195738252708294945320" + "3969657021169134916999794791553544054426668823852291733234236693" + "4178738081619274342922698767296233937873073756955509269717272907" + "8566607940937442517"); static BigInteger A = new BigInteger("32189274574111378750865973746687106" + "3695160924347574569923113893643975328118502246784387874381928804" + "6865920942258286938666201264395694101012858796521485171319748255" + "4630425677084511454641229993833255506759834486100188932905136959" + "7287419551379203001848457730376230681693887924162381650252270090" + "28296990388507680954"); public static void main(String[] args) { FewChars(); System.out.println(); ManyChars(); } public static void FewChars() { //ElGamalEncipher(String plaintext, BigInteger p, BigInteger g, BigInteger r) BigInteger[] cipherText = ElGamal.ElGamalEncipher("This is a string " + "of 129 characters which works just fine . This is a string " + "of 129 characters which works just fine . This is a s", P, G, R); System.out.println("This is a string of 129 characters which works " + "just fine . This is a string of 129 characters which works " + "just fine . This is a s"); //ElGamalDecipher(BigInteger c, BigInteger d, BigInteger a, BigInteger p) System.out.println("The decrypted text is: " + ElGamal.ElGamalDecipher(cipherText[0], cipherText[1], A, P)); } public static void ManyChars() { //ElGamalEncipher(String plaintext, BigInteger p, BigInteger g, BigInteger r) BigInteger[] cipherText = ElGamal.ElGamalEncipher("This is a string " + "of 130 characters which doesn’t work! This is a string of " + "130 characters which doesn’t work! This is a string of ", P, G, R); System.out.println("This is a string of 130 characters which doesn’t " + "work! This is a string of 130 characters which doesn’t work!" + " This is a string of "); //ElGamalDecipher(BigInteger c, BigInteger d, BigInteger a, BigInteger p) System.out.println("The decrypted text is: " + ElGamal.ElGamalDecipher(cipherText[0], cipherText[1], A, P)); } } import java.math.BigInteger; import java.security.SecureRandom; public class ElGamal { public static BigInteger[] ElGamalEncipher(String plaintext, BigInteger p, BigInteger g, BigInteger r) { // returns a BigInteger[] cipherText // cipherText[0] is c // cipherText[1] is d SecureRandom sr = new SecureRandom(); BigInteger[] cipherText = new BigInteger[2]; BigInteger pText = new BigInteger(plaintext.getBytes()); // 1: select a random integer k such that 1 <= k <= p-2 BigInteger k = new BigInteger(p.bitLength() - 2, sr); // 2: Compute c = g^k(mod p) BigInteger c = g.modPow(k, p); // 3: Compute d= P*r^k = P(g^a)^k(mod p) BigInteger d = pText.multiply(r.modPow(k, p)).mod(p); // C =(c,d) is the ciphertext cipherText[0] = c; cipherText[1] = d; return cipherText; } public static String ElGamalDecipher(BigInteger c, BigInteger d, BigInteger a, BigInteger p) { //returns the plaintext enciphered as (c,d) // 1: use the private key a to compute the least non-negative residue // of an inverse of (c^a)' (mod p) BigInteger z = c.modPow(a, p).modInverse(p); BigInteger P = z.multiply(d).mod(p); byte[] plainTextArray = P.toByteArray(); return new String(plainTextArray); } }

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• Incremental PCA

  - by smichak

  Hi, Lately, I've been looking into an implementation of an incremental PCA algorithm in python - I couldn't find something that would meet my needs so I did some reading and implemented an algorithm I found in some paper. Here is the module's code - the relevant paper on which it is based is mentioned in the module's documentation. I would appreciate any feedback from people who are interested in this. Micha #!/usr/bin/env python """ Incremental PCA calculation module. Based on P.Hall, D. Marshall and R. Martin "Incremental Eigenalysis for Classification" which appeared in British Machine Vision Conference, volume 1, pages 286-295, September 1998. Principal components are updated sequentially as new observations are introduced. Each new observation (x) is projected on the eigenspace spanned by the current principal components (U) and the residual vector (r = x - U(U.T*x)) is used as a new principal component (U' = [U r]). The new principal components are then rotated by a rotation matrix (R) whose columns are the eigenvectors of the transformed covariance matrix (D=U'.T*C*U) to yield p + 1 principal components. From those, only the first p are selected. """ __author__ = "Micha Kalfon" import numpy as np _ZERO_THRESHOLD = 1e-9 # Everything below this is zero class IPCA(object): """Incremental PCA calculation object. General Parameters: m - Number of variables per observation n - Number of observations p - Dimension to which the data should be reduced """ def __init__(self, m, p): """Creates an incremental PCA object for m-dimensional observations in order to reduce them to a p-dimensional subspace. @param m: Number of variables per observation. @param p: Number of principle components. @return: An IPCA object. """ self._m = float(m) self._n = 0.0 self._p = float(p) self._mean = np.matrix(np.zeros((m , 1), dtype=np.float64)) self._covariance = np.matrix(np.zeros((m, m), dtype=np.float64)) self._eigenvectors = np.matrix(np.zeros((m, p), dtype=np.float64)) self._eigenvalues = np.matrix(np.zeros((1, p), dtype=np.float64)) def update(self, x): """Updates with a new observation vector x. @param x: Next observation as a column vector (m x 1). """ m = self._m n = self._n p = self._p mean = self._mean C = self._covariance U = self._eigenvectors E = self._eigenvalues if type(x) is not np.matrix or x.shape != (m, 1): raise TypeError('Input is not a matrix (%d, 1)' % int(m)) # Update covariance matrix and mean vector and centralize input around # new mean oldmean = mean mean = (n*mean + x) / (n + 1.0) C = (n*C + x*x.T + n*oldmean*oldmean.T - (n+1)*mean*mean.T) / (n + 1.0) x -= mean # Project new input on current p-dimensional subspace and calculate # the normalized residual vector g = U.T*x r = x - (U*g) r = (r / np.linalg.norm(r)) if not _is_zero(r) else np.zeros_like(r) # Extend the transformation matrix with the residual vector and find # the rotation matrix by solving the eigenproblem DR=RE U = np.concatenate((U, r), 1) D = U.T*C*U (E, R) = np.linalg.eigh(D) # Sort eigenvalues and eigenvectors from largest to smallest to get the # rotation matrix R sorter = list(reversed(E.argsort(0))) E = E[sorter] R = R[:,sorter] # Apply the rotation matrix U = U*R # Select only p largest eigenvectors and values and update state self._n += 1.0 self._mean = mean self._covariance = C self._eigenvectors = U[:, 0:p] self._eigenvalues = E[0:p] @property def components(self): """Returns a matrix with the current principal components as columns. """ return self._eigenvectors @property def variances(self): """Returns a list with the appropriate variance along each principal component. """ return self._eigenvalues def _is_zero(x): """Return a boolean indicating whether the given vector is a zero vector up to a threshold. """ return np.fabs(x).min() < _ZERO_THRESHOLD if __name__ == '__main__': import sys def pca_svd(X): X = X - X.mean(0).repeat(X.shape[0], 0) [_, _, V] = np.linalg.svd(X) return V N = 1000 obs = np.matrix([np.random.normal(size=10) for _ in xrange(N)]) V = pca_svd(obs) print V[0:2] pca = IPCA(obs.shape[1], 2) for i in xrange(obs.shape[0]): x = obs[i,:].transpose() pca.update(x) U = pca.components print U

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• Passing unknown amounts of variables using through a string string and eval and multiple functions a

  - by user300797

  I'm not sure how best to describe this problem... In short, I want to use object literal to allow me to pass a random amount of variables in any order to a function. Whilst this is not big deal in theory, in my code, this object literal is passed to a second function call on_change. on_change works comparing an element inner HTML to a string. if it is the same, it sets a time out of to call the function again (this is sort of/almost recursive, but the function dose actually get to end before it is called again). if the elements inner HTML is different from the string, then the third parameter is executed. this will either be a function or a string. either way it will execute. I have tested this function plenty and used it for a while now. how ever, it cannot seem to get the object literal to flow through the function calls... var params = { xpos:'false'}; on_change('window_3_cont_buffer','',' if(Window_manager.windows[3].window_cont_buffer.getElementsByTagName(\'content\')[0].getElementsByTagName(\'p\')[0].innerHTML == \'ERROR\'){ alert(Window_manager.windows[3].window_cont_buffer.getElementsByTagName(\'content\')[0].getElementsByTagName(\'p\')[1].innerHTML); return false; } else { Window_manager.windows[3].load_xml(\'location/view.php?location_ID=3\', \'\', ' + params + ' ); } '); I call this as part of the form submission. after this line, I then call a function to load some content via ajax, which works fine and will trigger the code from the on_change function. I have tested load_xml function it is able to call alert(param.xpos) and get the correct response. I can even added in a check for being undefined so that rest of the times I cam load_xml I don't get swamped with alerts. The load_xml function first set up the on_change function, then calls the function to load the content to a hidden div. Once the AJAX request has updated that DIV, the on_change function should now call the parse_xml function. This pulls out the information from the xml file. How ever... The idea of this object literal param is that it can tell this parse_xml function to ignore certain things. on_change("window_" + this.id + "_cont_buffer", "", "Window_manager.windows[" + this.id + "].parse_xml('" + param + "')"); this is part of load_xml. it works perfectly fine, even with the param bit in there. except, parse_xml dose not seem to be able to use that parameter. I have been able to get it to a point where parse_xml can alert(param) and give [object object] which I would of thought meant that the object litteral had been passed through, but when I try and call alert(param.xpos) I get undefined. I know this is a pig of a problem, and I could get around it by just having the function take a zillion boolean parameters, but its just not practical or elegant. I'm sure you will need to ask me plenty more questions before I can solve this. I will post more complete code, I just cut it down to what is actually going on. Thanks

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• Is it possible to implement bitwise operators using integer arithmetic?

  - by Statement

  Hello World! I am facing a rather peculiar problem. I am working on a compiler for an architecture that doesn't support bitwise operations. However, it handles signed 16 bit integer arithmetics and I was wondering if it would be possible to implement bitwise operations using only: Addition (c = a + b) Subtraction (c = a - b) Division (c = a / b) Multiplication (c = a * b) Modulus (c = a % b) Minimum (c = min(a, b)) Maximum (c = max(a, b)) Comparisons (c = (a < b), c = (a == b), c = (a <= b), et.c.) Jumps (goto, for, et.c.) The bitwise operations I want to be able to support are: Or (c = a | b) And (c = a & b) Xor (c = a ^ b) Left Shift (c = a << b) Right Shift (c = a b) (All integers are signed so this is a problem) Signed Shift (c = a b) One's Complement (a = ~b) (Already found a solution, see below) Normally the problem is the other way around; how to achieve arithmetic optimizations using bitwise hacks. However not in this case. Writable memory is very scarce on this architecture, hence the need for bitwise operations. The bitwise functions themselves should not use a lot of temporary variables. However, constant read-only data & instruction memory is abundant. A side note here also is that jumps and branches are not expensive and all data is readily cached. Jumps cost half the cycles as arithmetic (including load/store) instructions do. On other words, all of the above supported functions cost twice the cycles of a single jump. Some thoughts that might help: I figured out that you can do one's complement (negate bits) with the following code: // Bitwise one's complement b = ~a; // Arithmetic one's complement b = -1 - a; I also remember the old shift hack when dividing with a power of two so the bitwise shift can be expressed as: // Bitwise left shift b = a << 4; // Arithmetic left shift b = a * 16; // 2^4 = 16 // Signed right shift b = a >>> 4; // Arithmetic right shift b = a / 16; For the rest of the bitwise operations I am slightly clueless. I wish the architects of this architecture would have supplied bit-operations. I would also like to know if there is a fast/easy way of computing the power of two (for shift operations) without using a memory data table. A naive solution would be to jump into a field of multiplications: b = 1; switch (a) { case 15: b = b * 2; case 14: b = b * 2; // ... exploting fallthrough (instruction memory is magnitudes larger) case 2: b = b * 2; case 1: b = b * 2; } Or a Set & Jump approach: switch (a) { case 15: b = 32768; break; case 14: b = 16384; break; // ... exploiting the fact that a jump is faster than one additional mul // at the cost of doubling the instruction memory footprint. case 2: b = 4; break; case 1: b = 2; break; }

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• Does this code follow the definition of recursion?

  - by dekz

  Hi All, I have a piece of code which I am doubting it as a implementation of recursion by its definition. My understanding is that the code must call itself, the exact same function. I also question whether writing the code this way adds additional overhead which can be seen with the use of recursion. What are your thoughts? class dhObject { public: dhObject** children; int numChildren; GLdouble linkLength; //ai GLdouble theta; //angle of rot about the z axis GLdouble twist; //about the x axis GLdouble displacement; // displacement from the end point of prev along z GLdouble thetaMax; GLdouble thetaMin; GLdouble thetaInc; GLdouble direction; dhObject(ifstream &fin) { fin >> numChildren >> linkLength >> theta >> twist >> displacement >> thetaMax >> thetaMin; //std::cout << numChildren << std::endl; direction = 1; thetaInc = 1.0; if (numChildren > 0) { children = new dhObject*[numChildren]; for(int i = 0; i < numChildren; ++i) { children[i] = new dhObject(fin); } } } void traverse(void) { glPushMatrix(); //draw move initial and draw transform(); draw(); //draw children for(int i = 0; i < numChildren; ++i) { children[i]->traverse(); } glPopMatrix(); } void update(void) { //Update the animation, if it has finished all animation go backwards if (theta <= thetaMin) { thetaInc = 1.0; } else if (theta >= thetaMax) { thetaInc = -1.0; } theta += thetaInc; //std::cout << thetaMin << " " << theta << " " << thetaMax << std::endl; for(int i = 0; i < numChildren; ++i) { children[i]->update(); } } void draw(void) { glPushMatrix(); glColor3f (0.0f,0.0f,1.0f); glutSolidCube(0.1); glPopMatrix(); } void transform(void) { //Move in the correct way, R, T, T, R glRotatef(theta, 0, 0, 1.0); glTranslatef(0,0,displacement); glTranslatef(linkLength, 0,0); glRotatef(twist, 1.0,0.0,0.0); } };

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• WCF via SSL connectivity problems

  - by Brett Widmeier

  Hello, I am hosting a WCF service from inside a Windows service using WAS. When I set the service to listen on 127.0.0.1, I have connectivity from my local machine as well as from my network. However, when I set it to listen on my outbound interface port 443, I can no longer even see the wsdl by connecting with a browser. Strangely, I can connect to the service by using telnet. The cert I am using was generated for my interface by a CA, and I have successfully used this exact cert with this service before. When checking the application log, I see that the service starts without error and is listening on the correct interface. From this information, it seems to me that the config file is in a valid state, but somehow misconfigured for what I want. I have, however, previously deployed this same setup on other sites using this config file. In case it is helpful, below is my config file. Any thoughts? <!--<system.diagnostics> <sources> <source name="System.ServiceModel" switchValue="Warning, ActivityTracing" propagateActivity="true"> <listeners> <add type="System.Diagnostics.DefaultTraceListener" name="Default"> <filter type="" /> </add> <add name="ServiceModelTraceListener"> <filter type="" /> </add> </listeners> </source> </sources> <sharedListeners> <add initializeData="app_tracelog.svclog" type="System.Diagnostics.XmlWriterTraceListener, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" name="ServiceModelTraceListener" traceOutputOptions="Timestamp"> <filter type="" /> </add> </sharedListeners> </system.diagnostics>--> <appSettings/> <connectionStrings/> <system.serviceModel> <!--<diagnostics> <messageLogging logEntireMessage="true" logMalformedMessages="true" logMessagesAtServiceLevel="true" logMessagesAtTransportLevel="true" maxMessagesToLog ="1000" maxSizeOfMessageToLog="524288"/> </diagnostics>--> <bindings> <basicHttpBinding> <binding name="basicHttps"> <security mode="Transport"> <transport clientCredentialType="None"/> <message /> </security> </binding> </basicHttpBinding> </bindings> <services> <service behaviorConfiguration="ServiceBehavior" name="<fully qualified name of service>"> <endpoint address="" binding="basicHttpBinding" name="OrdersSoap" contract="<fully qualified name of contract>" bindingNamespace="http://emr.orders.com/WebServices" bindingConfiguration="basicHttps" /> <endpoint binding="mexHttpsBinding" address="mex" contract="IMetadataExchange" /> <host> <baseAddresses> <add baseAddress="https://<external IP>/<name of service>>/" /> </baseAddresses> </host> </service> </services> <behaviors> <serviceBehaviors> <behavior name="ServiceBehavior"> <serviceMetadata httpsGetEnabled="False"/> <serviceDebug includeExceptionDetailInFaults="True" /> <dataContractSerializer maxItemsInObjectGraph="2147483646"/> </behavior> </serviceBehaviors> </behaviors> </system.serviceModel>

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• Remote host: can tracert, can telnet, can*not* browse: what gives?

  - by MacThePenguin

  One of my customers of the company I work for has made a change to their Internet connection, and now we can't connect to them any more from our LAN. To help me troubleshoot this issue, the network guy on the customer's site has configured their firewall so that a HTTPS connection to their public IP address is open to any IP. I should put https://<customer's IP> in my browser and get a web page. Well, it works from any network I've tried (even from my smartphone), just not from my company's LAN. I thought it may be an issue with our firewall (though I checked its rules and it allows outbound TCP port 443 to anywhere), so I just connected a PC directly to the network connection of our provider, bypassing out firewall completely, and still it didn't work (everything else worked). So I asked for help to our Internet provider's customer service, and they asked me to do a tracert to our customer's IP. The tracert is successful, as the final hop shown in the output is the host I want to reach. So they said there's no problem. :( I also tried telnet <customer's IP> 443 and that works as well: I get a blank page with the cursor blinking (I've tried using another random port and that gives me an error message, as it should). Still, from any browser of any PC in my LAN I can't open that URL. I tried checking the network traffic with Wireshark: I see the packages going through and answers coming back, thought the packets I see passing are far less than they are if I successfully connect to another HTTPS website. See the attached screenshot: I had to blur the IPs, anyway the longer string is my PC's local IP address, the shorter one is the customer's public IP. I don't know what else to try. This is the only IP doing this... Any idea what could I try to find a solution to this issue? Thanks, let me know if you need further details. Edit: when I say "it doesn't work" I mean: the page doesn't open, the browser keeps loading for a long time and eventually shows an error saying that the page cannot be opened. I'm not in my office now so I can't paste the exact message, but it's the usual message you get when the browser reaches its timeout. When I say "it works", I mean the browser loads and shows a webpage (it's the logon page for the customers' firewall admin interface: so there's the firewall brand's logo and there are fields to enter a user id and a password). Update 13/09/2012: tried again to connect to the customer's network through our Internet connection without a firewall. This is what I did: Run a Kubuntu 12.04 live distro on a spare laptop; Updated all the packages I could and installed WireShark; Attached it to my LAN and verified that I couldn't open https://<customer's IP>. Verified that the Wireshark trace for this attempt was the same as the one I've already posted; Verified that I could connect to another customer's host using rdesktop (it worked); Tried to rdesktop to <customer's IP>, here's the output: kubuntu@kubuntu:/etc$ rdesktop <customer's IP> Autoselected keyboard map en-us ERROR: recv: Connection reset by peer Disconnected the laptop from the LAN; Disconnected the firewall from the Extranet connection, connected the laptop instead. Set its network configuration so that I could access the Internet; Verified that I could connect to other websites in http and https and in RDP to other customers' hosts - it all worked as expected; Verified that I could still traceroute to <customer's IP>: I could; Verified that I still couldn't open https://<customer's IP> (same exact result as before); Checked the WireShark trace for this attempt and noticed a different behaviour: I could see packets going out to the customer's IP, but no replies at all; Tried to run rdesktop again, with a slightly different result: kubuntu@kubuntu:/etc/network$ rdesktop <customer's IP> Autoselected keyboard map en-us ERROR: <customer's IP>: unable to connect Finally gave up, put everything back as it was before, turned off the laptop and lost the WireShark traces I had saved. :( I still remember them very well though. :) Can you get anything out of it? Thank you very much. Update 12/09/2012 n.2: I followed the suggestion by MadHatter in the comments. From inside the firewall, this is what I get: user@ubuntu-mantis:~$ openssl s_client -connect <customer's IP>:443 CONNECTED(00000003) If I now type GET / the output pauses for several seconds and then I get: write:errno=104 I'm going to try the same, but bypassing the firewall, as soon as I can. Thanks. Update 12/09/2012 n.3: So, I think ISA Server is altering the results of my tests... I tried installing Wireshark directly on the firewall and monitoring the packets on the Extranet network card. When the destination is the customer's IP, whatever service I try to connect to (HTTPS, RDP or SAProuter), I can only see outbound packets and no response packets whatsoever from their side. It looks like ISA Server is "faking" the remote server's replies, that's why I get a connection using telnet or the openSSL client. This is the wireshark trace from inside our LAN: But this is the trace on the Extranet network card: This makes a bit more sense... I'll send this info to the customer's tech and see if he can make anything out of it. Thanks to all that took the time to read my question and post suggestions. I'll update this post again.

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• VFS: file-max limit 1231582 reached

  - by Rick Koshi

  I'm running a Linux 2.6.36 kernel, and I'm seeing some random errors. Things like ls: error while loading shared libraries: libpthread.so.0: cannot open shared object file: Error 23 Yes, my system can't consistently run an 'ls' command. :( I note several errors in my dmesg output: # dmesg | tail [2808967.543203] EXT4-fs (sda3): re-mounted. Opts: (null) [2837776.220605] xv[14450] general protection ip:7f20c20c6ac6 sp:7fff3641b368 error:0 in libpng14.so.14.4.0[7f20c20a9000+29000] [4931344.685302] EXT4-fs (md16): re-mounted. Opts: (null) [4982666.631444] VFS: file-max limit 1231582 reached [4982666.764240] VFS: file-max limit 1231582 reached [4982767.360574] VFS: file-max limit 1231582 reached [4982901.904628] VFS: file-max limit 1231582 reached [4982964.930556] VFS: file-max limit 1231582 reached [4982966.352170] VFS: file-max limit 1231582 reached [4982966.649195] top[31095]: segfault at 14 ip 00007fd6ace42700 sp 00007fff20746530 error 6 in libproc-3.2.8.so[7fd6ace3b000+e000] Obviously, the file-max errors look suspicious, being clustered together and recent. # cat /proc/sys/fs/file-max 1231582 # cat /proc/sys/fs/file-nr 1231712 0 1231582 That also looks a bit odd to me, but the thing is, there's no way I have 1.2 million files open on this system. I'm the only one using it, and it's not visible to anyone outside the local network. # lsof | wc 16046 148253 1882901 # ps -ef | wc 574 6104 44260 I saw some documentation saying: file-max & file-nr: The kernel allocates file handles dynamically, but as yet it doesn't free them again. The value in file-max denotes the maximum number of file- handles that the Linux kernel will allocate. When you get lots of error messages about running out of file handles, you might want to increase this limit. Historically, the three values in file-nr denoted the number of allocated file handles, the number of allocated but unused file handles, and the maximum number of file handles. Linux 2.6 always reports 0 as the number of free file handles -- this is not an error, it just means that the number of allocated file handles exactly matches the number of used file handles. Attempts to allocate more file descriptors than file-max are reported with printk, look for "VFS: file-max limit reached". My first reading of this is that the kernel basically has a built-in file descriptor leak, but I find that very hard to believe. It would imply that any system in active use needs to be rebooted every so often to free up the file descriptors. As I said, I can't believe this would be true, since it's normal to me to have Linux systems stay up for months (even years) at a time. On the other hand, I also can't believe that my nearly-idle system is holding over a million files open. Does anyone have any ideas, either for fixes or further diagnosis? I could, of course, just reboot the system, but I don't want this to be a recurring problem every few weeks. As a stopgap measure, I've quit Firefox, which was accounting for almost 2000 lines of lsof output (!) even though I only had one window open, and now I can run 'ls' again, but I doubt that will fix the problem for long. (edit: Oops, spoke too soon. By the time I finished typing out this question, the symptom was/is back) Thanks in advance for any help. And another update: My system was basically unusable, so I decided I had no option but to reboot. But before I did, I carefully quit one process at a time, checking /proc/sys/fs/file-nr after each termination. I found that, predictably, the number of open files gradually went down as I closed things down. Unfortunately, it wasn't a large effect. Yes, I was able to clear up 5000-10000 open files, but there were still over 1.2 million left. I shut down just about everything. All interactive shells, except for the one ssh I left open to finish closing down, httpd, even nfs service. Basically everything in the process table that wasn't a kernel process, and there were still an appalling number of files apparently left open. After the reboot, I found that /proc/sys/fs/file-nr showed about 2000 files open, which is much more reasonable. Starting up 2 Xvnc sessions as usual, along with the dozen or so monitoring windows I like to keep open, brought the total up to about 4000 files. I can see nothing wrong with that, of course, but I've obviously failed to identify the root cause. I'm still looking for ideas, since I definitely expect it to happen again. And another update, the next day: I watched the system carefully, and discovered that /proc/sys/fs/file-nr showed a growth of about 900 open files per hour. I shut down the system's only NFS client for the night, and the growth stopped. Mind you, it didn't free up the resources, but it did at least stop consuming more. Is this a known bug with NFS? I'll be bringing the NFS client back online today, and I'll narrow it down further. If anyone is familiar with this behavior, feel free to jump in with "Yeah, NFS4 has this problem, go back to NFS3" or something like that.

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• Call an member function implementing the {{#linkTo ...}} helper from javascript code

  - by gonvaled

  I am trying to replace this navigation menu: <nav> {{#linkTo "nodes" }}<i class="icon-fixed-width icon-cloud icon-2x"></i>&nbsp;&nbsp;{{t generic.nodes}} {{grayOut "(temporal)"}}{{/linkTo}} {{#linkTo "services" }}<i class="icon-fixed-width icon-phone icon-2x"></i>&nbsp;&nbsp;{{t generic.services}}{{/linkTo}} {{#linkTo "agents" }}<i class="icon-fixed-width icon-headphones icon-2x"></i>&nbsp;&nbsp;{{t generic.agents}}{{/linkTo}} {{#linkTo "extensions" }}<i class="icon-fixed-width icon-random icon-2x"></i>&nbsp;&nbsp;{{t generic.extensions}}{{/linkTo}} {{#linkTo "voiceMenus" }}<i class="icon-fixed-width icon-sitemap icon-2x"></i>&nbsp;&nbsp;{{t generic.voicemenus}}{{/linkTo}} {{#linkTo "queues" }}<i class="icon-fixed-width icon-tasks icon-2x"></i>&nbsp;&nbsp;{{t generic.queues}}{{/linkTo}} {{#linkTo "contacts" }}<i class="icon-fixed-width icon-user icon-2x"></i>&nbsp;&nbsp;{{t generic.contacts}}{{/linkTo}} {{#linkTo "accounts" }}<i class="icon-fixed-width icon-building icon-2x"></i>&nbsp;&nbsp;{{t generic.accounts}}{{/linkTo}} {{#linkTo "locators" }}<i class="icon-fixed-width icon-phone-sign icon-2x"></i>&nbsp;&nbsp;{{t generic.locators}}{{/linkTo}} {{#linkTo "phonelocations" }}<i class="icon-fixed-width icon-globe icon-2x"></i>&nbsp;&nbsp;{{t generic.phonelocations}}{{/linkTo}} {{#linkTo "billing" }}<i class="icon-fixed-width icon-euro icon-2x"></i>&nbsp;&nbsp;{{t generic.billing}}{{/linkTo}} {{#linkTo "profile" }}<i class="icon-fixed-width icon-cogs icon-2x"></i>&nbsp;&nbsp;{{t generic.profile}}{{/linkTo}} {{#linkTo "audio" }}<i class="icon-fixed-width icon-music icon-2x"></i>&nbsp;&nbsp;{{t generic.audio}}{{/linkTo}} {{#linkTo "editor" }}<i class="icon-fixed-width icon-puzzle-piece icon-2x"></i>&nbsp;&nbsp;{{t generic.node_editor}}{{/linkTo}} </nav> With a more dynamic version. What I am trying to do is to reproduce the html inside Ember.View.render, but I would like to reuse as much Ember functionality as possible. Specifically, I would like to reuse the {{#linkTo ...}} helper, with two goals: Reuse existing html rendering implemented in the {{#linkTo ...}} helper Get the same routing support that using the {{#linkTo ...}} in a template provides. How can I call this helper from within javascript code? This is my first (incomplete) attempt. The template: {{view SettingsApp.NavigationView}} And the view: var trans = Ember.I18n.t; var MAIN_MENU = [ { 'linkTo' : 'nodes', 'i-class' : 'icon-cloud', 'txt' : trans('generic.nodes') }, { 'linkTo' : 'services', 'i-class' : 'icon-phone', 'txt' : trans('generic.services') }, ]; function getNavIcon (data) { var linkTo = data.linkTo, i_class = data['i-class'], txt = data.txt; var html = '<i class="icon-fixed-width icon-2x ' + i_class + '"></i>&nbsp;&nbsp;' + txt; return html; } SettingsApp.NavigationView = Ember.View.extend({ menu : MAIN_MENU, render: function(buffer) { for (var i=0, l=this.menu.length; i<l; i++) { var data = this.menu[i]; // TODO: call the ember function implementing the {{#linkTo ...}} helper buffer.push(getNavIcon(data)); } return buffer; } });

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• C# Windows Service XML

  - by Goober

  Scenario I have a windows service written in C# that performs some processing based on parsing an XML file and use that data to carry out various tasks. The service also does various bits of logging - which uses settings from an APP.Config file. The Problem When the service is compiled, installed and run, the XML file seems to disappear. I'm getting the impression that it is just ignored or something like that. So far I've tried using TWO App.Config files, one named App.Config that contains settings for the service, and the other called MyService.exe.config that contains all of the data that was used in the XML file (the idea being that I can parse the XML from a config file that actually gets compiled and appears in my installation directory. However When I do this, all that happens is that ONE config file appears (with the name MyService.exe.config), but it contains the contents of the App.Config file and not the XML data that I want to parse. What I need All I want is to have a config file for my settings, and an XML file for my data. Question Is this possible? I know the application works as it was originally built as a console application that ran fine. Other The application has to be designed this way (as in, I need my data stored as XML, and my settings stored in a config file). Thoughts If I could somehow combine the contents of the two files into ONE config file, that would be one way of solving the problem. However, I have tried this and of course I get a "Type Initialisation Exception", as the config file cannot interprate the XML data (probably because the tags are custom and do not form any part of the config schema - or something like that). Ideas Please could someone explain to me if it is possible for me to have an XML file AND a config file that will actually be compiled and stored in my installation directory for the service when it is run? CODE Custom XML/Data Config File <?xml version="1.0" encoding="utf-8" ?> <configuration> <servers> <SV066930> <add name="Name" value = "SV066930" /> <processes> <SimonTest1> <add name="ProcessName" value="notepad.exe" /> <add name="CommandLine" value="C:\\WINDOWS\\system32\\notepad.exe C:\\WINDOWS\\Profiles\\TA2TOF1\\Desktop\\SimonTest1.txt" /> </SimonTest1> </processes> </SV066930> </servers> </configuration> APP.Config Settings File <?xml version="1.0" encoding="utf-8" ?> <configuration> <configSections> <section name="dataConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Data.Configuration.DatabaseSettings, Microsoft.Practices.EnterpriseLibrary.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=xxxxxxxxxxx" /> </configSections> <connectionStrings> <add name="DB" connectionString="Data Source=etc......" /> </connectionStrings> </configuration> Help greatly appreciated.

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• What is "elegant" code?

  - by Breton

  I see a lot of lip service and talk about the most "elegant" way to do this or that. I think if you spend enough time programming you begin to obtain a sort of intuitive feel for what it is we call "elegance". But I'm curious. Even if we can look at a bit of code, and say instinctively "That's elegant", or "That's messy", I wonder if any of us really understands what that means. Is there a precise definition for this "elegance" we keep referring to? If there is, what is it? Now, what I mean by a precise definition, is a series of statements which can be used to derive questions about a peice of code, or a program as a whole, and determine objectively, or as objectively as possible, whether that code is "elegant" or not. May I assert, that perhaps no such definition exists, and it's all just personal preference. In this case, I ask you a slightly different question: Is there a better word for "elegance", or a better set of attributes to use for judging code quality that is perhaps more objective than merely appealing to individual intuition and taste? Perhaps code quality is a matter of taste, and the answer to both of my questions is "no". But I can't help but feel that we could be doing better than just expressing wishy washy feelings about our code quality. For example, user interface design is something that to a broad range of people looks for all the world like a field of study that oughtta be 100% subjective matter of taste. But this is shockingly and brutally not the case, and there are in fact many objective measures that can be applied to a user interface to determine its quality. A series of tests could be written to give a definitive and repeatable score to user interface quality. (See GOMS, for instance). Now, okay. is Elegance simply "code quality" or is it something more? Is it something that can be measured? Or is it a matter of taste? Does our profession have room for taste? Maybe I'm asking the wrong questions altogether. Help me out here. Bonus Round If there is such a thing as elegance in code, and that concept is useful, do you think that justifies classifying the field of programming as an "Art" capital A, or merely a "craft". Or is it just an engineering field populated by a bunch of wishful thinking humans? Consider this question in the light of your thoughts about the elegance question. Please note that there is a distinction between code which is considered "art" in itself, and code that was written merely in the service of creating an artful program. When I ask this question, I ask if the code itself justifies calling programming an art. Bounty Note I liked the answers to this question so much, I think I'd like to make a photographic essay book from it. Released as a free PDF, and published on some kind of on demand printing service of course, such as "zazz" or "tiggle" or "printley" or something . I'd like some more answers, please!

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• Use QuickCheck by generating primes

  - by Dan

  Background For fun, I'm trying to write a property for quick-check that can test the basic idea behind cryptography with RSA. Choose two distinct primes, p and q. Let N = p*q e is some number relatively prime to (p-1)(q-1) (in practice, e is usually 3 for fast encoding) d is the modular inverse of e modulo (p-1)(q-1) For all x such that 1 < x < N, it is always true that (x^e)^d = x modulo N In other words, x is the "message", raising it to the eth power mod N is the act of "encoding" the message, and raising the encoded message to the dth power mod N is the act of "decoding" it. (The property is also trivially true for x = 1, a case which is its own encryption) Code Here are the methods I have coded up so far: import Test.QuickCheck -- modular exponentiation modExp :: Integral a => a -> a -> a -> a modExp y z n = modExp' (y `mod` n) z `mod` n where modExp' y z | z == 0 = 1 | even z = modExp (y*y) (z `div` 2) n | odd z = (modExp (y*y) (z `div` 2) n) * y -- relatively prime rPrime :: Integral a => a -> a -> Bool rPrime a b = gcd a b == 1 -- multiplicative inverse (modular) mInverse :: Integral a => a -> a -> a mInverse 1 _ = 1 mInverse x y = (n * y + 1) `div` x where n = x - mInverse (y `mod` x) x -- just a quick way to test for primality n `divides` x = x `mod` n == 0 primes = 2:filter isPrime [3..] isPrime x = null . filter (`divides` x) $ takeWhile (\y -> y*y <= x) primes -- the property prop_rsa (p,q,x) = isPrime p && isPrime q && p /= q && x > 1 && x < n && rPrime e t ==> x == (x `powModN` e) `powModN` d where e = 3 n = p*q t = (p-1)*(q-1) d = mInverse e t a `powModN` b = modExp a b n (Thanks, google and random blog, for the implementation of modular multiplicative inverse) Question The problem should be obvious: there are way too many conditions on the property to make it at all usable. Trying to invoke quickCheck prop_rsa in ghci made my terminal hang. So I've poked around the QuickCheck manual a bit, and it says: Properties may take the form forAll <generator> $ \<pattern> -> <property> How do I make a <generator> for prime numbers? Or with the other constraints, so that quickCheck doesn't have to sift through a bunch of failed conditions? Any other general advice (especially regarding QuickCheck) is welcome.

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