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  • how does linear probing handle this?

    - by Weadadada Awda
    • the hash function: h(x) = | 2x + 5 | mod M • a bucket array of capacity N • a set of objects with keys: 12, 44, 13, 88, 23, 94, 11, 39, 20, 16, 5 (to input from left to right) 4.a [5 pts] Write the hash table where M=N=11 and collisions are handled using linear probing. So I got up to here x x x x x 44 88 12 23 13 94 but the next variable should go after the 94 now, (the 11) but does it start from the beggining or what? thx

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  • what architecture to use with asp.net mvc vd web forms

    - by kacalapy
    please explain how to get high capacity architectures with both the default asp.net web forms and mvc models with regard to being able to serve millions of page views. i want to know how to set up each model from DB clustering, to caching, logical/ physical tiers, load balancing iis servers, scaling out or up, session state management and so on... is one more scalable than the other? thanks all.

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  • [ASP.NET ERROR] The request was aborted: Could not create SSL/TLS secure channel.

    - by Mark Cidade
    I'm posting this on behalf of a co-worker. He gets a "The request was aborted: Could not create SSL/TLS secure channel" error while using a WebRequest object to make an HTTPS request. Th funny thing is that this only happens after a while, and is temporarily fixed when the application is restarted, which suggests that something is being filled to capacity or something. Has anyone seen this kind of thing before?

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  • Averaging initial values for rolling series

    - by Dave Jarvis
    Question Given a maximum sliding window size of 40 (i.e., the set of numbers in the list cannot exceed 40), what is the calculation to ensure a smooth averaging transition as the set size grows from 1 to 40? Problem Description Creating a trend line for a set of data has skewed initial values. The complete set of values is unknown at runtime: they are provided one at a time. It seems like a reverse-weighted average is required so that the initial values are averaged differently. In the image below the leftmost data for the trend line are incorrectly averaged. Current Solution Created a new type of ArrayList subclass that calculates the appropriate values and ensures its size never goes beyond the bounds of the sliding window: /** * A list of Double values that has a maximum capacity enforced by a sliding * window. Can calculate the average of its values. */ public class AveragingList extends ArrayList<Double> { private float slidingWindowSize = 0.0f; /** * The initial capacity is used for the sliding window size. * @param slidingWindowSize */ public AveragingList( int slidingWindowSize ) { super( slidingWindowSize ); setSlidingWindowSize( ( float )slidingWindowSize ); } public boolean add( Double d ) { boolean result = super.add( d ); // Prevent the list from exceeding the maximum sliding window size. // if( size() > getSlidingWindowSize() ) { remove( 0 ); } return result; } /** * Calculate the average. * * @return The average of the values stored in this list. */ public double average() { double result = 0.0; int size = size(); for( Double d: this ) { result += d.doubleValue(); } return (double)result / (double)size; } /** * Changes the maximum number of numbers stored in this list. * * @param slidingWindowSize New maximum number of values to remember. */ public void setSlidingWindowSize( float slidingWindowSize ) { this.slidingWindowSize = slidingWindowSize; } /** * Returns the number used to determine the maximum values this list can * store before it removes the first entry upon adding another value. * @return The maximum number of numbers stored in this list. */ public float getSlidingWindowSize() { return slidingWindowSize; } } Resulting Image Example Input The data comes into the function one value at a time. For example, data points (Data) and calculated averages (Avg) typically look as follows: Data: 17.0 Avg : 17.0 Data: 17.0 Avg : 17.0 Data: 5.0 Avg : 13.0 Data: 5.0 Avg : 11.0  Related Sites The following pages describe moving averages, but typically when all (or sufficient) data is known: http://www.cs.princeton.edu/introcs/15inout/MovingAverage.java.html http://stackoverflow.com/questions/2161815/r-zoo-series-sliding-window-calculation http://taragana.blogspot.com/ http://www.dreamincode.net/forums/index.php?showtopic=92508 http://blogs.sun.com/nickstephen/entry/dtrace_and_moving_rolling_averages

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  • Is literate programming dead?

    - by Stephen
    A fair bit is written about literate programming, but I've yet to see any project that uses it in any capacity, nor have I seen it used to teach programming. My sample may small, so I'm looking for evidence that literate programming exists and is successful in the real world.

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  • Php, mysql selection

    - by cosy
    I have this table ATTRIBUTE id name um 12 capacity MB;GB;TB And this table2 : id id_attribute id_product name value um 1 12 40 hdd maxtor 30 GB 2 12 41 hdd maxtor 40 GB 3 12 42 hdd y 1 TB How can i select from table2 in this order : 30GB 40GB 1TB? Thanks a lot!

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  • Add to SortedSet<T> and its complexity

    - by Andrei Taptunov
    MSDN states the following SortedSet(T).Add Method : If Count is less than the capacity of the internal array, this method is an O(1) operation. Could someone please explain "how so"? I mean when adding new value we need to find a correct place to add a value (comparing it with another values) and internal implementation looks like a "Red-Black tree" with O (log N) insertion complexity.

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  • IContextMenu::GetCommandString Not showing help text in Windows Explorer

    - by Grant
    Hi, i am implementing a shell context menu for windows explorer and have successfully created the menu's. What i am having trouble with is the IContextMenu::GetCommandString method that displays the help text in the status bar when you hover over the selected menu item. When i do hover over each item nothing is displayed, but whats weird is that some of the other items that i didnt create, eg - open, or print have had their help text turned into garbage.. Here is a code sample of IContextMenu::QueryContextMenu & IContextMenu::GetCommandString.. int ShellExtLib.IContextMenu.QueryContextMenu(IntPtr hMenu, uint indexMenu, uint idCmdFirst, uint idCmdLast, uint uFlags) { uint idCmd = idCmdFirst; StringBuilder sb = new StringBuilder(1024); try { if ((uFlags & 0xf) == 0 || (uFlags & (uint)ShellExtLib.CMF.CMF_EXPLORE) != 0) { uint selectedFileCount = Helpers.DragQueryFile(m_hDrop, 0xffffffff, null, 0); if (selectedFileCount == 1) { Helpers.DragQueryFile(m_hDrop, 0, sb, sb.Capacity + 1); Documents.Add(sb.ToString()); } else { // MULTIPLE FILES SELECTED. for (uint i = 0; i < selectedFileCount; i++) { Helpers.DragQueryFile(m_hDrop, i, sb, sb.Capacity + 1); Documents.Add(sb.ToString()); } } Helpers.InsertMenu(hMenu, indexMenu++, ShellExtLib.UFLAGS.MF_SEPARATOR | ShellExtLib.UFLAGS.MF_BYPOSITION, 0, null); IntPtr hSubMenu = Helpers.CreateMenu(); if (hSubMenu != IntPtr.Zero) { Helpers.InsertMenu(hSubMenu, 0, ShellExtLib.UFLAGS.MF_STRING | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, "Item 1"); Helpers.InsertMenu(hSubMenu, 1, ShellExtLib.UFLAGS.MF_STRING | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, "Item 2"); Helpers.InsertMenu(hSubMenu, 2, ShellExtLib.UFLAGS.MF_SEPARATOR | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, null); Helpers.InsertMenu(hSubMenu, 3, ShellExtLib.UFLAGS.MF_STRING | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, "Item 3"); Helpers.InsertMenu(hSubMenu, 4, ShellExtLib.UFLAGS.MF_SEPARATOR | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, null); Helpers.InsertMenu(hSubMenu, 5, ShellExtLib.UFLAGS.MF_STRING | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, "Item 4"); Helpers.InsertMenu(hSubMenu, 6, ShellExtLib.UFLAGS.MF_STRING | ShellExtLib.UFLAGS.MF_BYPOSITION, idCmd++, "Item 5"); } Helpers.InsertMenu(hMenu, indexMenu++, ShellExtLib.UFLAGS.MF_STRING | ShellExtLib.UFLAGS.MF_BYPOSITION | ShellExtLib.UFLAGS.MF_POPUP, (uint)hSubMenu, "Main Menu"); Helpers.InsertMenu(hMenu, indexMenu++, ShellExtLib.UFLAGS.MF_SEPARATOR | ShellExtLib.UFLAGS.MF_BYPOSITION, 0, null); return (int)(idCmd - idCmdFirst); } } catch { } return 0; } void ShellExtLib.IContextMenu.GetCommandString(int idCmd, uint uFlags, int pwReserved, StringBuilder commandString, int cchMax) { switch (uFlags) { case (uint)ShellExtLib.GCS.VERB: commandString = new StringBuilder("x"); break; case (uint)ShellExtLib.GCS.HELPTEXTA: commandString = new StringBuilder("y"); break; } } Does anyone have any suggestions? I have read a number of articles on how to build shell extensions and have also been reading MSDN as well.. Thanks.

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  • Size of a sharepoint web application

    - by Indra
    How do you figure out the current size of the sharepoint web application? Better yet, the size of a site collection or a subsite. I am planning to move a site collection from one farm to another. I need to plan the storage capacity first.

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  • Java homework help, Error <identifier> expected

    - by user2900126
    Help with java homework this is my assignment that I have, this assignment code I've tried. But when I try to compile it I keep getting errors which I cant seem to find soloutions too: Error says <identifier> expected for Line 67 public static void () Assignment brief To write a simple java classMobile that models a mobile phone. Details the information stored about each mobile phone will include • Its type e.g. “Sony ericsson x90” or “Samsung Galaxy S”; • Its screen size in inches; You may assume that this a whole number from the scale 3 to 5 inclusive. • Its memory card capacity in gigabytes You may assume that this a whole number • The name of its present service provider You may assume this is a single line of text. • The type of contract with service provider You may assume this is a single line of text. • Its camera resolution in megapixels; You should not assume that this a whole number; • The percentage of charge left on the phone e.g. a fully charged phone will have a charge of 100. You may assume that this a whole number • Whether the phone has GPS or not. Your class will have fields corresponding to these attributes . Start by opening BlueJ, creating a new project called myMobile which has a classMobile and set up the fields that you need, Next you will need to write a Constructor for the class. Assume that each phone is manufactured by creating an object and specifying its type, its screen size, its memory card capacity, its camera resolution and whether it has GPS or not. Therefore you will need a constructor that allows you to pass arguments to initialise these five attributes. Other fields should be set to appropriate default values. You may assume that a new phone comes fully charged. When the phone is sold to its owner, you will need to set the service provider and type of contract with that provider so you will need mutator methods • setProvider () - - to set service provider. • setContractType - - to set the type of contract These methods will be used when the phones provider is changed. You should also write a mutator method ChargeUp () which simulates fully charging the phone. To obtain information about your mobile object you should write • accessor methods corresponding to four of its fields: • getType () – which returns the type of mobile; • getProvider () – which returns the present service provider; • getContractType () – which returns its type of contract; • getCharge () – which returns its remaining charge. An accessor method to printDetails () to print, to the terminal window, a report about the phone e.g. This mobile phone is a sony Erricsson X90 with Service provider BigAl and type of contract PAYG. At present it has 30% of its battery charge remaining. Check that the new method works correctly by for example, • creating a Mobile object and setting its fields; • calling printDetails () and t=checking the report corresponds to the details you have just given the mobile; • changing the service provider and contract type by calling setprovider () and setContractType (); • calling printDetails () and checking the report now prints out the new details. Challenging excercises • write a mutator methodswitchedOnFor () =which simulates using the phone for a specified period. You may assume the phone loses 1% of its charge for each hour that it is switched on . • write an accessor method checkcharge () whichg checks the phone remaing charge. If this charge has a value less than 25%, then this method returns a string containg the message Be aware that you will soon need to re-charge your phone, otherwise it returns a string your phone charge is sufficient. • Write a method changeProvider () which simulates changing the provider (and presumably also the type of service contract). Finally you may add up to four additional fields, with appropriate methods, that might be required in a more detailed model. above is my assignment that I have, this assignment code I've tried. But when I try to oompile it I keep getting errors which I cant seem to find soloutions too: Error says <identifier> expected for Line 67 public static void () /** * to write a simple java class Mobile that models a mobile phone. * * @author (Lewis Burte-Clarke) * @version (14/10/13) */ public class Mobile { // type of phone private String phonetype; // size of screen in inches private int screensize; // menory card capacity private int memorycardcapacity; // name of present service provider private String serviceprovider; // type of contract with service provider private int typeofcontract; // camera resolution in megapixels private int cameraresolution; // the percentage of charge left on the phone private int checkcharge; // wether the phone has GPS or not private String GPS; // instance variables - replace the example below with your own private int x; // The constructor method public Mobile(String mobilephonetype, int mobilescreensize, int mobilememorycardcapacity,int mobilecameraresolution,String mobileGPS, String newserviceprovider) { this.phonetype = mobilephonetype; this.screensize = mobilescreensize; this.memorycardcapacity = mobilememorycardcapacity; this.cameraresolution = mobilecameraresolution; this.GPS = mobileGPS; // you do not use this ones during instantiation,you can remove them if you do not need or assign them some default values //this.serviceprovider = newserviceprovider; //this.typeofcontract = 12; //this.checkcharge = checkcharge; Mobile samsungPhone = new Mobile("Samsung", "1024", "2", "verizon", "8", "GPS"); 1024 = screensize; 2 = memorycardcapacity; 8 = resolution; GPS = gps; "verizon"=serviceprovider; //typeofcontract = 12; //checkcharge = checkcharge; } // A method to display the state of the object to the screen public void displayMobileDetails() { System.out.println("phonetype: " + phonetype); System.out.println("screensize: " + screensize); System.out.println("memorycardcapacity: " + memorycardcapacity); System.out.println("cameraresolution: " + cameraresolution); System.out.println("GPS: " + GPS); System.out.println("serviceprovider: " + serviceprovider); System.out.println("typeofcontract: " + typeofcontract); } /** * The mymobile class implements an application that * simply displays "new Mobile!" to the standard output. */ public class mymobile { public static void main(String[] args) { System.out.println("new Mobile!"); //Display the string. } } public static void buildPhones(){ Mobile Samsung = new Mobile("Samsung", "3.0", "4gb", "8mega pixels", "GPS"); Mobile Blackberry = new Mobile("Blackberry", "3.0", "4gb", "8mega pixels", "GPS"); Samsung.displayMobileDetails(); Blackberry.displayMobileDetails(); } public static void main(String[] args) { buildPhones(); } } any answers.replies and help would be greatly appreciated as I really lost!

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  • How to append to an array that contains blank spaces - Java

    - by Cameron Townley
    I'm trying to append to a char[] array that contains blank spaces on the end. The char array for example contains the characters 'aaa'. When I append the first time the method functions properly and outputs 'aaabbb'. The initial capacity of the array is set to 80 or multiples of 80. The second time I try and append my output looks like"aaabbb bbb". Any psuedocode would be great.

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  • Java error - not a statement, what does this mean?

    - by user2898828
    I am trying to get my code to create the new constructor objects which I require to create a mobile phone object. I have tried naming the constuctor fields to create the object. when I compile my code on this line this.Mobile samsungPhone = new Mobile("Samsung", 1, 2, "verizon", 3 "GPS"); I get this error: not a statement, what does this mean?? UPDATED CODE! my code: /** * to write a simple java class Mobile that models a mobile phone. * * @author (Lewis Burte-Clarke) * @version (14/10/13) */ public class Mobile { // type of phone private String phonetype; // size of screen in inches private int screensize; // menory card capacity private int memorycardcapacity; // name of present service provider private String serviceprovider; // type of contract with service provider private int typeofcontract; // camera resolution in megapixels private int cameraresolution; // the percentage of charge left on the phone private int checkcharge; // wether the phone has GPS or not private String GPS; // instance variables - replace the example below with your own private int x; // The constructor method public Mobile(String mobilephonetype, int mobilescreensize, int mobilememorycardcapacity,int mobilecameraresolution,String mobileGPS, String newserviceprovider) { this.phonetype = mobilephonetype; this.screensize = mobilescreensize; this.memorycardcapacity = mobilememorycardcapacity; this.cameraresolution = mobilecameraresolution; this.GPS = mobileGPS; this.serviceprovider = newserviceprovider; this.typeofcontract = 12; this.checkcharge = checkcharge; // you do not use this ones during instantiation,you can remove them if you do not need or assign them some default values Mobile samsungPhone = new Mobile("Samsung", 1, 2, "verizon", 3, "GPS"); 1024 = screen size; 2 = memory card capacity; 3=resolution; GPS = gps; "verizon"=service provider; typeofcontract = 12; checkcharge = checkcharge; } } // A method to display the state of the object to the screen public void displayMobileDetails() { System.out.println("phonetype: " + phonetype); System.out.println("screensize: " + screensize); System.out.println("memorycardcapacity: " + memorycardcapacity); System.out.println("cameraresolution: " + cameraresolution); System.out.println("GPS: " + GPS); System.out.println("serviceprovider: " + serviceprovider); System.out.println("typeofcontract: " + typeofcontract); } } class mymobile { public static void) { Mobile Samsung = new Mobile("Samsung", 1, 2, "verizon", 3, "GPS"); Mobile Blackberry = new Mobile("Blackberry", "3.", "4","8", "GPS"); Samsung.displayMobileDetails(); Blackberry.displayMobileDetails(); } } any answers and replies would be greatly appreciated!

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  • ListItemCollection is limited to 127 items?

    - by HeavyWave
    I am trying to add a lot of item to ListItemCollection in the ListControl, but once the Count reaches 127 I can't add any more items. It doesn't throw any exceptions, just doesn't add the items. I have changed Capacity to 256, but it still won't add more than 127 items. Is there a hard-coded limit?

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  • storing characters in char data type C language

    - by iSight
    Hi, I can store string of few length in char data type. But when it exceeds its capacity what can be the alternative way to store string. I am using char data type. void setString(char* inPoints) { if (strcmp(mPoints, inPoints)!= ZERO) { if (mPoints) { free(mPoints); } mPoints = (char*)malloc((strlen(inPoints) + 1) * sizeof(char)); strcpy(mPoints, inPoints); } }

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  • How to set a global CURL rate(speed) limit?

    - by Mint
    I had a look around for the CURL settings file but didn't find it in /etc/ and didn't find much on the curl site ether... So basically what I want to do set a maximum speed limit that curl can upload at (no matter how many instances of it are running) so that my server has some upload capacity left for other tasks.

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  • Prevent auto mounting Android sdcard under Linux Mint

    - by BullShark
    I recently obtained an older Android phone, so that I could test Android Apps on it. I've needed it because I have a Nexus 7 but not older Android versions, hardware, etc. to test on. I'm having a problem with it under Linux Mint with Cinnamon. When I plug the phone in, or remove and plug the sdcard from the phone back to it while the phone is plugged in, Linux automatically mounts the sdcard. This is a problem because once it is mounted under Linux, it dismounts from the phone running Android 2.3.5, and I can no longer test Android Apps I write that require the sdcard to be present, writable. I went to Menu System Tools System Settings System Details Removable Media, and it brings up this window. I have changed the settings to always "Ask what to do" on "Select how media should be handled". However, the sdcard still gets mounted and then I am asked how I want to open these files (media players, photo importers, file browser, etc.). If I click the checkbox for "Never prompt or start programs on media insertion", then the sdcard is mounted, and I am not asked how to open these files. Eject is just a noob word for Ubuntu users that means umount (unmount) like "Adminstrator" is another ubuntu noob word for the root user. And if I unmount the sdcard, the phone doesn't recognize it again until I take the sdcard out and plug it back in. The phone sees it for a brief moment until Linux Mint takes it over. There are 2 possible solutions and maybe more: 1) Prevent Linux from automounting sdcards some how 2) Tell Android not to allow the computer it is plugged into to take over the sdcard, HOW? Edit: I found out how to prevent the sdcard from being automatically mounted: Now it gets recognized by Linux: bullshark@beastlinux ~ $ dmesg | tail -n 25 [597212.218323] sd 21:0:0:0: [sde] Attached SCSI removable disk [597212.218639] sr 21:0:0:1: Attached scsi CD-ROM sr2 [597212.218910] sr 21:0:0:1: Attached scsi generic sg7 type 5 [597217.139373] sd 21:0:0:0: [sde] 3862528 512-byte logical blocks: (1.97 GB/1.84 GiB) [597217.140726] sd 21:0:0:0: [sde] No Caching mode page present [597217.140735] sd 21:0:0:0: [sde] Assuming drive cache: write through [597217.143595] sd 21:0:0:0: [sde] No Caching mode page present [597217.143602] sd 21:0:0:0: [sde] Assuming drive cache: write through [597217.152240] sde: sde1 [597389.751008] 4:2:1: cannot get freq at ep 0x84 [597390.238742] 4:2:1: cannot get freq at ep 0x84 [597624.903132] sde: detected capacity change from 1977614336 to 0 [597637.677763] sd 21:0:0:0: [sde] 3862528 512-byte logical blocks: (1.97 GB/1.84 GiB) [597637.679616] sd 21:0:0:0: [sde] No Caching mode page present [597637.679626] sd 21:0:0:0: [sde] Assuming drive cache: write through [597637.682508] sd 21:0:0:0: [sde] No Caching mode page present [597637.682515] sd 21:0:0:0: [sde] Assuming drive cache: write through [597637.692758] sde: sde1 [597661.857979] sde: detected capacity change from 1977614336 to 0 [597688.775455] sd 21:0:0:0: [sde] 3862528 512-byte logical blocks: (1.97 GB/1.84 GiB) [597688.776814] sd 21:0:0:0: [sde] No Caching mode page present [597688.776823] sd 21:0:0:0: [sde] Assuming drive cache: write through [597688.780055] sd 21:0:0:0: [sde] No Caching mode page present [597688.780062] sd 21:0:0:0: [sde] Assuming drive cache: write through [597688.788639] sde: sde1 bullshark@beastlinux ~ $ However, the phone still unmounts the sdcard upon being detected by Linux. Linux detects but does not mount, and a few seconds later: Edit #2 (Solution): I solved this one by changing the usb connection type (was usb mass storage) :

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  • Issues Deploying Functional WAR to Elastic Beanstalk with Tomcat7

    - by BFar
    I am currently deploying OpenTripPlanner (http://github.com/OpenPlans/OpenTripPlanner.git) to Elastic Beanstalk. I'm able to successfully build and deploy opentripplanner with my own customized settings on an ec2. I have set it up so that the appropriate WAR file can be placed in the Tomcat/Webapps folder, and when Tomcat is started up, it will auto-deploy, and even download open trip planner's graph.obj from an S3. All of that works just fine, except when I try to deploy to Elastic Beanstalk. When I upload to Elastic Beanstalk, the log shows that my WAR file is successfully unpacked & successfully downloads the graph.obj from my S3. The only difference is that then nothing happens and I can't load the site in my browser. The health is RED, and I can't figure out what is going on. I've tried looking into ports and dns issues, but I can't determine what's wrong. Anyone have any ideas? Why would a WAR that works on tomcat7 outside of Beanstalk fail to be accessible?

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  • C# 4: The Curious ConcurrentDictionary

    - by James Michael Hare
    In my previous post (here) I did a comparison of the new ConcurrentQueue versus the old standard of a System.Collections.Generic Queue with simple locking.  The results were exactly what I would have hoped, that the ConcurrentQueue was faster with multi-threading for most all situations.  In addition, concurrent collections have the added benefit that you can enumerate them even if they're being modified. So I set out to see what the improvements would be for the ConcurrentDictionary, would it have the same performance benefits as the ConcurrentQueue did?  Well, after running some tests and multiple tweaks and tunes, I have good and bad news. But first, let's look at the tests.  Obviously there's many things we can do with a dictionary.  One of the most notable uses, of course, in a multi-threaded environment is for a small, local in-memory cache.  So I set about to do a very simple simulation of a cache where I would create a test class that I'll just call an Accessor.  This accessor will attempt to look up a key in the dictionary, and if the key exists, it stops (i.e. a cache "hit").  However, if the lookup fails, it will then try to add the key and value to the dictionary (i.e. a cache "miss").  So here's the Accessor that will run the tests: 1: internal class Accessor 2: { 3: public int Hits { get; set; } 4: public int Misses { get; set; } 5: public Func<int, string> GetDelegate { get; set; } 6: public Action<int, string> AddDelegate { get; set; } 7: public int Iterations { get; set; } 8: public int MaxRange { get; set; } 9: public int Seed { get; set; } 10:  11: public void Access() 12: { 13: var randomGenerator = new Random(Seed); 14:  15: for (int i=0; i<Iterations; i++) 16: { 17: // give a wide spread so will have some duplicates and some unique 18: var target = randomGenerator.Next(1, MaxRange); 19:  20: // attempt to grab the item from the cache 21: var result = GetDelegate(target); 22:  23: // if the item doesn't exist, add it 24: if(result == null) 25: { 26: AddDelegate(target, target.ToString()); 27: Misses++; 28: } 29: else 30: { 31: Hits++; 32: } 33: } 34: } 35: } Note that so I could test different implementations, I defined a GetDelegate and AddDelegate that will call the appropriate dictionary methods to add or retrieve items in the cache using various techniques. So let's examine the three techniques I decided to test: Dictionary with mutex - Just your standard generic Dictionary with a simple lock construct on an internal object. Dictionary with ReaderWriterLockSlim - Same Dictionary, but now using a lock designed to let multiple readers access simultaneously and then locked when a writer needs access. ConcurrentDictionary - The new ConcurrentDictionary from System.Collections.Concurrent that is supposed to be optimized to allow multiple threads to access safely. So the approach to each of these is also fairly straight-forward.  Let's look at the GetDelegate and AddDelegate implementations for the Dictionary with mutex lock: 1: var addDelegate = (key,val) => 2: { 3: lock (_mutex) 4: { 5: _dictionary[key] = val; 6: } 7: }; 8: var getDelegate = (key) => 9: { 10: lock (_mutex) 11: { 12: string val; 13: return _dictionary.TryGetValue(key, out val) ? val : null; 14: } 15: }; Nothing new or fancy here, just your basic lock on a private object and then query/insert into the Dictionary. Now, for the Dictionary with ReadWriteLockSlim it's a little more complex: 1: var addDelegate = (key,val) => 2: { 3: _readerWriterLock.EnterWriteLock(); 4: _dictionary[key] = val; 5: _readerWriterLock.ExitWriteLock(); 6: }; 7: var getDelegate = (key) => 8: { 9: string val; 10: _readerWriterLock.EnterReadLock(); 11: if(!_dictionary.TryGetValue(key, out val)) 12: { 13: val = null; 14: } 15: _readerWriterLock.ExitReadLock(); 16: return val; 17: }; And finally, the ConcurrentDictionary, which since it does all it's own concurrency control, is remarkably elegant and simple: 1: var addDelegate = (key,val) => 2: { 3: _concurrentDictionary[key] = val; 4: }; 5: var getDelegate = (key) => 6: { 7: string s; 8: return _concurrentDictionary.TryGetValue(key, out s) ? s : null; 9: };                    Then, I set up a test harness that would simply ask the user for the number of concurrent Accessors to attempt to Access the cache (as specified in Accessor.Access() above) and then let them fly and see how long it took them all to complete.  Each of these tests was run with 10,000,000 cache accesses divided among the available Accessor instances.  All times are in milliseconds. 1: Dictionary with Mutex Locking 2: --------------------------------------------------- 3: Accessors Mostly Misses Mostly Hits 4: 1 7916 3285 5: 10 8293 3481 6: 100 8799 3532 7: 1000 8815 3584 8:  9:  10: Dictionary with ReaderWriterLockSlim Locking 11: --------------------------------------------------- 12: Accessors Mostly Misses Mostly Hits 13: 1 8445 3624 14: 10 11002 4119 15: 100 11076 3992 16: 1000 14794 4861 17:  18:  19: Concurrent Dictionary 20: --------------------------------------------------- 21: Accessors Mostly Misses Mostly Hits 22: 1 17443 3726 23: 10 14181 1897 24: 100 15141 1994 25: 1000 17209 2128 The first test I did across the board is the Mostly Misses category.  The mostly misses (more adds because data requested was not in the dictionary) shows an interesting trend.  In both cases the Dictionary with the simple mutex lock is much faster, and the ConcurrentDictionary is the slowest solution.  But this got me thinking, and a little research seemed to confirm it, maybe the ConcurrentDictionary is more optimized to concurrent "gets" than "adds".  So since the ratio of misses to hits were 2 to 1, I decided to reverse that and see the results. So I tweaked the data so that the number of keys were much smaller than the number of iterations to give me about a 2 to 1 ration of hits to misses (twice as likely to already find the item in the cache than to need to add it).  And yes, indeed here we see that the ConcurrentDictionary is indeed faster than the standard Dictionary here.  I have a strong feeling that as the ration of hits-to-misses gets higher and higher these number gets even better as well.  This makes sense since the ConcurrentDictionary is read-optimized. Also note that I tried the tests with capacity and concurrency hints on the ConcurrentDictionary but saw very little improvement, I think this is largely because on the 10,000,000 hit test it quickly ramped up to the correct capacity and concurrency and thus the impact was limited to the first few milliseconds of the run. So what does this tell us?  Well, as in all things, ConcurrentDictionary is not a panacea.  It won't solve all your woes and it shouldn't be the only Dictionary you ever use.  So when should we use each? Use System.Collections.Generic.Dictionary when: You need a single-threaded Dictionary (no locking needed). You need a multi-threaded Dictionary that is loaded only once at creation and never modified (no locking needed). You need a multi-threaded Dictionary to store items where writes are far more prevalent than reads (locking needed). And use System.Collections.Concurrent.ConcurrentDictionary when: You need a multi-threaded Dictionary where the writes are far more prevalent than reads. You need to be able to iterate over the collection without locking it even if its being modified. Both Dictionaries have their strong suits, I have a feeling this is just one where you need to know from design what you hope to use it for and make your decision based on that criteria.

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  • 13.10 - Weird WiFi connection problems - WMP300N - Broadcom BCM4321

    - by user1898041
    Just installed 13.10 on my desktop and I really like it. After having problems with getting the wifi to work, I installed it connected to the internet with an ethernet cable and added in the 3rd party software and updates as per the installation procedure. After installation was completed, I saw the wifi icon in the upper right hand corner, but it was not seeing any wifi networks. Some Googling brought me to use the 'Additional Drivers' application. It found the WMP300N Broadcom BDM4321 based pci wifi card and installed the proprietary Broadcom STA wireless driver, which may have been installed before. I'm not sure. Here is the weird part: when I start my system, wifi seems to be in some sort of suspended state where the system sees that the card exists but the card will not detect any wifi networks. It will work after booting once I 'Additional Drivers' application and then start FireFox. I know it seems weird, but this is the process I've got down to get the card to recognize wifi networks. After those applications are open for a few seconds, the card starts to function like normal (although maintaining the wifi connection is problem but most likely a seperate issue). The reason this is a problem is because this is supposed to just be a headless box managed through SSH. Here are the readouts from the common network diagnosis programs BEFORE I open 'Additional Drivers' and 'FireFox'. All commands were done with sudo. lspci 00:00.0 Host bridge: Intel Corporation 82G35 Express DRAM Controller (rev 03) 00:01.0 PCI bridge: Intel Corporation 82G35 Express PCI Express Root Port (rev 03) 00:1a.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 02) 00:1a.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 (rev 02) 00:1a.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #6 (rev 02) 00:1a.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 (rev 02) 00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 02) 00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 (rev 02) 00:1c.4 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 5 (rev 02) 00:1c.5 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 6 (rev 02) 00:1d.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 (rev 02) 00:1d.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 (rev 02) 00:1d.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 (rev 02) 00:1d.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 (rev 02) 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 92) 00:1f.0 ISA bridge: Intel Corporation 82801IR (ICH9R) LPC Interface Controller (rev 02) 00:1f.2 SATA controller: Intel Corporation 82801IR/IO/IH (ICH9R/DO/DH) 6 port SATA Controller [AHCI mode] (rev 02) 00:1f.3 SMBus: Intel Corporation 82801I (ICH9 Family) SMBus Controller (rev 02) 01:00.0 VGA compatible controller: NVIDIA Corporation GT216 [GeForce GT 220] (rev a2) 01:00.1 Audio device: NVIDIA Corporation High Definition Audio Controller (rev a1) 02:00.0 Ethernet controller: Qualcomm Atheros Attansic L1 Gigabit Ethernet (rev b0) 03:00.0 IDE interface: JMicron Technology Corp. JMB368 IDE controller 05:00.0 Network controller: Broadcom Corporation BCM4321 802.11b/g/n (rev 01) 05:03.0 FireWire (IEEE 1394): VIA Technologies, Inc. VT6306/7/8 [Fire II(M)] IEEE 1394 OHCI Controller (rev c0) - lshw *-network description: Ethernet interface product: Attansic L1 Gigabit Ethernet vendor: Qualcomm Atheros physical id: 0 bus info: pci@0000:02:00.0 logical name: eth0 version: b0 serial: 00:22:15:00:a8:12 capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list rom ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=atl1 driverversion=2.1.3 latency=0 link=no multicast=yes port=twisted pair resources: irq:46 memory:feac0000-feafffff memory:feaa0000-feabffff *-network description: Wireless interface product: BCM4321 802.11b/g/n vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:05:00.0 logical name: eth1 version: 01 serial: 00:23:69:d8:2b:16 width: 32 bits clock: 33MHz capabilities: bus_master ethernet physical wireless configuration: broadcast=yes driver=wl0 driverversion=6.30.223.141 (r415941) latency=64 multicast=yes wireless=IEEE 802.11abg resources: irq:16 memory:febfc000-febfffff - ifconfig eth0 Link encap:Ethernet HWaddr 00:22:15:00:a8:12 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) eth1 Link encap:Ethernet HWaddr 00:23:69:d8:2b:16 inet6 addr: fe80::223:69ff:fed8:2b16/64 Scope:Link UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Interrupt:16 Base address:0xc000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:24 errors:0 dropped:0 overruns:0 frame:0 TX packets:24 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:1856 (1.8 KB) TX bytes:1856 (1.8 KB) - iwconfig eth1 IEEE 802.11abg ESSID:off/any Mode:Managed Access Point: Not-Associated Tx-Power=200 dBm Retry long limit:7 RTS thr:off Fragment thr:off Encryption key:off Power Management:off - iwlist scan eth1 No scan results - Here are the various commands AFTER I open 'Additional Drivers' and 'FireFox' lspci 00:00.0 Host bridge: Intel Corporation 82G35 Express DRAM Controller (rev 03) 00:01.0 PCI bridge: Intel Corporation 82G35 Express PCI Express Root Port (rev 03) 00:1a.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 02) 00:1a.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 (rev 02) 00:1a.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #6 (rev 02) 00:1a.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 (rev 02) 00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 02) 00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 (rev 02) 00:1c.4 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 5 (rev 02) 00:1c.5 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 6 (rev 02) 00:1d.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 (rev 02) 00:1d.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 (rev 02) 00:1d.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 (rev 02) 00:1d.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 (rev 02) 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 92) 00:1f.0 ISA bridge: Intel Corporation 82801IR (ICH9R) LPC Interface Controller (rev 02) 00:1f.2 SATA controller: Intel Corporation 82801IR/IO/IH (ICH9R/DO/DH) 6 port SATA Controller [AHCI mode] (rev 02) 00:1f.3 SMBus: Intel Corporation 82801I (ICH9 Family) SMBus Controller (rev 02) 01:00.0 VGA compatible controller: NVIDIA Corporation GT216 [GeForce GT 220] (rev a2) 01:00.1 Audio device: NVIDIA Corporation High Definition Audio Controller (rev a1) 02:00.0 Ethernet controller: Qualcomm Atheros Attansic L1 Gigabit Ethernet (rev b0) 03:00.0 IDE interface: JMicron Technology Corp. JMB368 IDE controller 05:00.0 Network controller: Broadcom Corporation BCM4321 802.11b/g/n (rev 01) 05:03.0 FireWire (IEEE 1394): VIA Technologies, Inc. VT6306/7/8 [Fire II(M)] IEEE 1394 OHCI Controller (rev c0) - lshw *-network description: Ethernet interface product: Attansic L1 Gigabit Ethernet vendor: Qualcomm Atheros physical id: 0 bus info: pci@0000:02:00.0 logical name: eth0 version: b0 serial: 00:22:15:00:a8:12 capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list rom ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=atl1 driverversion=2.1.3 latency=0 link=no multicast=yes port=twisted pair resources: irq:46 memory:feac0000-feafffff memory:feaa0000-feabffff *-network description: Wireless interface product: BCM4321 802.11b/g/n vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:05:00.0 logical name: eth1 version: 01 serial: 00:23:69:d8:2b:16 width: 32 bits clock: 33MHz capabilities: bus_master ethernet physical wireless configuration: broadcast=yes driver=wl0 driverversion=6.30.223.141 (r415941) ip=192.168.1.103 latency=64 multicast=yes wireless=IEEE 802.11abg resources: irq:16 memory:febfc000-febfffff - ifconfig eth0 Link encap:Ethernet HWaddr 00:22:15:00:a8:12 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) eth1 Link encap:Ethernet HWaddr 00:23:69:d8:2b:16 inet addr:192.168.1.103 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::223:69ff:fed8:2b16/64 Scope:Link UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:85 errors:0 dropped:0 overruns:0 frame:11901 TX packets:132 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:52641 (52.6 KB) TX bytes:19058 (19.0 KB) Interrupt:16 Base address:0xc000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:76 errors:0 dropped:0 overruns:0 frame:0 TX packets:76 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:6084 (6.0 KB) TX bytes:6084 (6.0 KB) - iwconfig eth1 IEEE 802.11abg ESSID:"BU" Mode:Managed Frequency:2.447 GHz Access Point: 00:26:F2:1F:81:02 Bit Rate=54 Mb/s Tx-Power=200 dBm Retry long limit:7 RTS thr:off Fragment thr:off Encryption key:off Power Management:off Link Quality=59/70 Signal level=-51 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0 - iwlist scan A LOT OF SSIDs FOUND! - I'd like to have this problem fixed, but I'm not quite sure where to go. Been Googling a lot and can't seem to find anyone else with this problem.

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  • Announcing Windows Azure Mobile Services

    - by ScottGu
    I’m excited to announce a new capability we are adding to Windows Azure today: Windows Azure Mobile Services Windows Azure Mobile Services makes it incredibly easy to connect a scalable cloud backend to your client and mobile applications.  It allows you to easily store structured data in the cloud that can span both devices and users, integrate it with user authentication, as well as send out updates to clients via push notifications. Today’s release enables you to add these capabilities to any Windows 8 app in literally minutes, and provides a super productive way for you to quickly build out your app ideas.  We’ll also be adding support to enable these same scenarios for Windows Phone, iOS, and Android devices soon. Read this getting started tutorial to walkthrough how you can build (in less than 5 minutes) a simple Windows 8 “Todo List” app that is cloud enabled using Windows Azure Mobile Services.  Or watch this video of me showing how to do it step by step. Getting Started If you don’t already have a Windows Azure account, you can sign up for a no-obligation Free Trial.  Once you are signed-up, click the “preview features” section under the “account” tab of the www.windowsazure.com website and enable your account to support the “Mobile Services” preview.   Instructions on how to enable this can be found here. Once you have the mobile services preview enabled, log into the Windows Azure Portal, click the “New” button and choose the new “Mobile Services” icon to create your first mobile backend.  Once created, you’ll see a quick-start page like below with instructions on how to connect your mobile service to an existing Windows 8 client app you have already started working on, or how to create and connect a brand-new Windows 8 client app with it: Read this getting started tutorial to walkthrough how you can build (in less than 5 minutes) a simple Windows 8 “Todo List” app  that stores data in Windows Azure. Storing Data in the Cloud Storing data in the cloud with Windows Azure Mobile Services is incredibly easy.  When you create a Windows Azure Mobile Service, we automatically associate it with a SQL Database inside Windows Azure.  The Windows Azure Mobile Service backend then provides built-in support for enabling remote apps to securely store and retrieve data from it (using secure REST end-points utilizing a JSON-based ODATA format) – without you having to write or deploy any custom server code.  Built-in management support is provided within the Windows Azure portal for creating new tables, browsing data, setting indexes, and controlling access permissions. This makes it incredibly easy to connect client applications to the cloud, and enables client developers who don’t have a server-code background to be productive from the very beginning.  They can instead focus on building the client app experience, and leverage Windows Azure Mobile Services to provide the cloud backend services they require.  Below is an example of client-side Windows 8 C#/XAML code that could be used to query data from a Windows Azure Mobile Service.  Client-side C# developers can write queries like this using LINQ and strongly typed POCO objects, which are then translated into HTTP REST queries that run against a Windows Azure Mobile Service.   Developers don’t have to write or deploy any custom server-side code in order to enable client-side code below to execute and asynchronously populate their client UI: Because Mobile Services is part of Windows Azure, developers can later choose to augment or extend their initial solution and add custom server functionality and more advanced logic if they want.  This provides maximum flexibility, and enables developers to grow and extend their solutions to meet any needs. User Authentication and Push Notifications Windows Azure Mobile Services also make it incredibly easy to integrate user authentication/authorization and push notifications within your applications.  You can use these capabilities to enable authentication and fine grain access control permissions to the data you store in the cloud, as well as to trigger push notifications to users/devices when the data changes.  Windows Azure Mobile Services supports the concept of “server scripts” (small chunks of server-side script that executes in response to actions) that make it really easy to enable these scenarios. Below are some tutorials that walkthrough common authentication/authorization/push scenarios you can do with Windows Azure Mobile Services and Windows 8 apps: Enabling User Authentication Authorizing Users  Get Started with Push Notifications Push Notifications to multiple Users Manage and Monitor your Mobile Service Just like with every other service in Windows Azure, you can monitor usage and metrics of your mobile service backend using the “Dashboard” tab within the Windows Azure Portal. The dashboard tab provides a built-in monitoring view of the API calls, Bandwidth, and server CPU cycles of your Windows Azure Mobile Service.   You can also use the “Logs” tab within the portal to review error messages.  This makes it easy to monitor and track how your application is doing. Scale Up as Your Business Grows Windows Azure Mobile Services now allows every Windows Azure customer to create and run up to 10 Mobile Services in a free, shared/multi-tenant hosting environment (where your mobile backend will be one of multiple apps running on a shared set of server resources).  This provides an easy way to get started on projects at no cost beyond the database you connect your Windows Azure Mobile Service to (note: each Windows Azure free trial account also includes a 1GB SQL Database that you can use with any number of apps or Windows Azure Mobile Services). If your client application becomes popular, you can click the “Scale” tab of your Mobile Service and switch from “Shared” to “Reserved” mode.  Doing so allows you to isolate your apps so that you are the only customer within a virtual machine.  This allows you to elastically scale the amount of resources your apps use – allowing you to scale-up (or scale-down) your capacity as your traffic grows: With Windows Azure you pay for compute capacity on a per-hour basis – which allows you to scale up and down your resources to match only what you need.  This enables a super flexible model that is ideal for new mobile app scenarios, as well as startups who are just getting going.  Summary I’ve only scratched the surface of what you can do with Windows Azure Mobile Services – there are a lot more features to explore.  With Windows Azure Mobile Services you’ll be able to build mobile app experiences faster than ever, and enable even better user experiences – by connecting your client apps to the cloud. Visit the Windows Azure Mobile Services development center to learn more, and build your first Windows 8 app connected with Windows Azure today.  And read this getting started tutorial to walkthrough how you can build (in less than 5 minutes) a simple Windows 8 “Todo List” app that is cloud enabled using Windows Azure Mobile Services. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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