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• How do I get this Cisco VPN client to connect?

  - by WebWeasel

  I've got Ubuntu 10.10 64 bit and installed network-manager-vpnc and configured the connection but I keep getting this: NetworkManager[1217]: <info> Starting VPN service 'org.freedesktop.NetworkManager.vpnc'... NetworkManager[1217]: <info> VPN service 'org.freedesktop.NetworkManager.vpnc' started (org.freedesktop.NetworkManager.vpnc), PID 4420 NetworkManager[1217]: <info> VPN service 'org.freedesktop.NetworkManager.vpnc' appeared, activating connections NetworkManager[1217]: <info> VPN plugin state changed: 1 NetworkManager[1217]: <info> VPN plugin state changed: 3 NetworkManager[1217]: <info> VPN connection 'CSI' (Connect) reply received. modem-manager: (net/tun0): could not get port's parent device NetworkManager[1217]: SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/tun0, iface: tun0) NetworkManager[1217]: SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/tun0, iface: tun0): no ifupdown configuration found. kernel: [ 2281.723506] tun0: Disabled Privacy Extensions avahi-daemon[1109]: Withdrawing workstation service for tun0. NetworkManager[1217]: SCPlugin-Ifupdown: devices removed (path: /sys/devices/virtual/net/tun0, iface: tun0) NetworkManager[1217]: <warn> VPN plugin failed: 1 NetworkManager[1217]: <info> VPN plugin state changed: 6 NetworkManager[1217]: <info> VPN plugin state change reason: 0 NetworkManager[1217]: <warn> error disconnecting VPN: Could not process the request because no VPN connection was active. NetworkManager[1217]: <info> Policy set 'Auto eth0' (eth0) as default for IPv4 routing and DNS. NetworkManager[1217]: <info> Starting VPN service 'org.freedesktop.NetworkManager.vpnc'... NetworkManager[1217]: <info> VPN service 'org.freedesktop.NetworkManager.vpnc' started (org.freedesktop.NetworkManager.vpnc), PID 4547 NetworkManager[1217]: <info> VPN service 'org.freedesktop.NetworkManager.vpnc' appeared, activating connections NetworkManager[1217]: <info> VPN plugin state changed: 1 NetworkManager[1217]: <info> VPN plugin state changed: 3 I've seen a couple of bugs on Launchpad that could be the same thing or have I done something wrong?

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• Action button: only true once per press

  - by Sidar

  I'm using SFML2.0 and am trying to make a wrapper class for my controller/joystick. I read all the input data from my controller and send it off to my controllable object. I want to have two types of buttons per button press, one that is continues(true false state ) and one that is an action and is set to false after the next frame update. Here is an example of how I set my button A to true or false with the SFML api. Whereas data is my struct of buttons, and A holds my true/false state every update. data.A = sf::Joystick::isButtonPressed(i,st::input::A); But I've also added "data.actionA" which represents the one time action state. Basically what I want is for actionA to be set false after the update its been set to true. I'm trying to keep track of the previous state. But I seem to fall into this loop where it toggles between true and false every update. Anyone an idea? Edit: Since I can't answer my own question yet here is my solution: data.actionA = data.A = sf::Joystick::isButtonPressed(i,st::input::A); if(prev.A) data.actionA = false; First I always set the actionA to the value of the button state. Then I check if the previous state of A is true. If so we negate the value.

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• Design For Asynchronous User Interface

  - by Sohnee

  I have been working on a integration that has posed an interesting user interface conundrum that I would like suggestions for. The user interface is displayed within a third party product. The state of the interface is supplied by calls to a service I have written. There can be small delays between the actual state changing the the user interface changing due to the polling for state by the third party. When a user interacts with the user interface, requests are sent back to my application. This then affects the state and the next state poll request will update the user interface. The problem is that the delay between pressing a button and seeing the user interface update is perhaps 1 or 2 seconds and in usability testing I can see that people are clicking again before the user interface updates, thinking that they haven't properly clicked the first time. Given the constraints (we can only update the user interface via the polling mechanism - if we updated it when they clicked, the polling might return and overwrite the change causing unpredictable / undesirable results)... what can we do to make the user experience better. My current idea is to show a message for a couple of seconds so people know their click was accepted, the message would not be affected by the state polling, so wouldn't be prematurely removed / overwritten etc. I'm sure there are other ideas out there and I'm also confident someone has a better idea that I have!

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• D key not working on Ubuntu

  - by Jonathan

  For some inexplicable reason the capital d key on my Ubuntu system is no longer producing output. Hitting caps lock and then d produces a D. I've tried multiple keyboards and the issue is the same. There's nothing bound to Shift+d under System Preferences Keyboard Shortcuts. xev produces the following: shift + a KeyPress event, serial 36, synthetic NO, window 0x4c00001, root 0x27a, subw 0x0, time 31268952, (130,-16), root:(1000,525), state 0x10, keycode 62 (keysym 0xffe2, Shift_R), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False KeyPress event, serial 36, synthetic NO, window 0x4c00001, root 0x27a, subw 0x0, time 31269376, (130,-16), root:(1000,525), state 0x11, keycode 38 (keysym 0x41, A), same_screen YES, XLookupString gives 1 bytes: (41) "A" XmbLookupString gives 1 bytes: (41) "A" XFilterEvent returns: False KeyRelease event, serial 36, synthetic NO, window 0x4c00001, root 0x27a, subw 0x0, time 31269584, (130,-16), root:(1000,525), state 0x11, keycode 38 (keysym 0x41, A), same_screen YES, XLookupString gives 1 bytes: (41) "A" XFilterEvent returns: False KeyRelease event, serial 36, synthetic NO, window 0x4c00001, root 0x27a, subw 0x0, time 31269608, (130,-16), root:(1000,525), state 0x11, keycode 62 (keysym 0xffe2, Shift_R), same_screen YES, XLookupString gives 0 bytes: XFilterEvent returns: False shift + d KeyPress event, serial 36, synthetic NO, window 0x4c00001, root 0x27a, subw 0x0, time 31102792, (115,-13), root:(985,528), state 0x10, keycode 62 (keysym 0xffe2, Shift_R), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False FocusOut event, serial 36, synthetic NO, window 0x4c00001, mode NotifyGrab, detail NotifyAncestor FocusIn event, serial 36, synthetic NO, window 0x4c00001, mode NotifyUngrab, detail NotifyAncestor KeymapNotify event, serial 36, synthetic NO, window 0x0, keys: 2 0 0 0 0 0 0 64 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 KeyRelease event, serial 36, synthetic NO, window 0x4c00001, root 0x27a, subw 0x0, time 31103104, (115,-13), root:(985,528), state 0x11, keycode 62 (keysym 0xffe2, Shift_R), same_screen YES, XLookupString gives 0 bytes: XFilterEvent returns: False

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• What are functional-programming ways of implementing Conway's Game of Life

  - by George Mauer

  I recently implemented for fun Conway's Game of Life in Javascript (actually coffeescript but same thing). Since javascript can be used as a functional language I was trying to stay to that end of the spectrum. I was not happy with my results. I am a fairly good OO programmer and my solution smacked of same-old-same-old. So long question short: what is the (pseudocode) functional style of doing it? Here is Pseudocode for my attempt: class Node update: (board) -> get number_of_alive_neighbors from board get this_is_alive from board if this_is_alive and number_of_alive_neighbors < 2 then die if this_is_alive and number_of_alive_neighbors > 3 then die if not this_is_alive and number_of_alive_neighbors == 3 then alive class NodeLocations at: (x, y) -> return node value at x,y of: (node) -> return x,y of node class Board getNeighbors: (node) -> use node_locations to check 8 neighbors around node and return count nodes = for 1..100 new Node state = new NodeState(nodes) locations = new NodeLocations(nodes) board = new Board(locations, state) executeRound: state = clone state accumulated_changes = for n in nodes n.update(board) apply accumulated_changes to state board = new Board(locations, state)

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• Custom Session Management using HashTable

  - by kaleidoscope

  ASP.NET session state lets you associate a server-side string or object dictionary containing state data with a particular HTTP client session. A session is defined as a series of requests issued by the same client within a certain period of time, and is managed by associating a session ID with each unique client. The ID is supplied by the client on each request, either in a cookie or as a special fragment of the request URL. The session data is stored on the server side in one of the supported session state stores, which include in-process memory, SQL Server™ database, and the ASP.NET State Server service. The latter two modes enable session state to be shared among multiple Web servers on a Web farm and do not require server affinity. Implement Custom session Handler you need to follow following process : 1. Create class library which will inherit from  SessionStateStoreProviderBase abstract Class. 2. Implement all abstract Method in your base class. 3.Change Mode of session to “Custom” in web.config file and provide Provider as your Namespace with classname. <sessionState mode=”Custom” customProvider=”Namespace.classname”> <Providers> <add name=”Name” type=”Namespace.classname”> </sessionstate> For more Details Please refer following links :   http://msdn.microsoft.com/en-us/magazine/cc163730.aspx http://msdn.microsoft.com/en-us/library/system.web.sessionstate.sessionstatestoreproviderbase.aspx - Chandraprakash, S Technorati Tags: Chandraprakash,Session state Managment

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• How lookaheads are propagated in "channel" method of building LALR parser?

  - by greenoldman

  The method is described in Dragon Book, however I read about it in ""Parsing Techniques" by D.Grune and C.J.H.Jacobs". I start from my understanding of building channels for NFA: channels are built once, they are like water channels with current you "drop" lookahead symbols in right places (sources) of the channel, and they propagate with "current" when symbol propagates, there are no barriers (the only sufficient things for propagation are presence of channel and direction/current); i.e. lookahead cannot just die out of the blue Is that right? If I am correct, then eof lookahead should be present in all states, because the source of it is the start production, and all other production states are reachable from start state. How the DFA is made out of this NFA is not perfectly clear for me -- the authors of the mentioned book write about preserving channels, but I see no purpose, if you propagated lookaheads. If the channels have to be preserved, are they cut off from the source if the DFA state does not include source NFA state? I assume no -- the channels still runs between DFA states, not only within given DFA state. In the effect eof should still be present in all items in all states. But when you take a look at DFA presented in book (pdf is from errata): DFA for LALR (fig. 9.34 in the book, p.301) you will see there are items without eof in lookahead. The grammar for this DFA is: S -> E E -> E - T E -> T T -> ( E ) T -> n So how it was computed, when eof was dropped, and on what condition? Update It is textual pdf, so two interesting states (in DFA; # is eof): State 1: S--- >•E[#] E--- >•E-T[#-] E--- >•T[#-] T--- >•n[#-] T--- >•(E)[#-] State 6: T--- >(•E)[#-)] E--- >•E-T[-)] E--- >•T[-)] T--- >•n[-)] T--- >•(E)[-)] Arc from 1 to 6 is labeled (.

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• which style of member-access is preferable

  - by itwasntpete

  the purpose of oop using classes is to encapsulate members from the outer space. i always read that accessing members should be done by methods. for example: template<typename T> class foo_1 { T state_; public: // following below }; the most common doing that by my professor was to have a get and set method. // variant 1 T const& getState() { return state_; } void setState(T const& v) { state_ = v; } or like this: // variant 2 // in my opinion it is easier to read T const& state() { return state_; } void state(T const& v) { state_ = v; } assume the state_ is a variable, which is checked periodically and there is no need to ensure the value (state) is consistent. Is there any disadvantage of accessing the state by reference? for example: // variant 3 // do it by reference T& state() { return state_; } or even directly, if I declare the variable as public. template<typename T> class foo { public: // variant 4 T state; }; In variant 4 I could even ensure consistence by using c++11 atomic. So my question is, which one should I prefer?, Is there any coding standard which would decline one of these pattern? for some code see here

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• Capital D key not working / producing output

  - by Jonathan

  For some inexplicable reason the capital d key on my Ubuntu system is no longer producing output. Hitting caps lock and then d produces a D. I've tried multiple keyboards and the issue is the same. There's nothing bound to Shift+d under System Preferences Keyboard Shortcuts. xev produces the following: shift + a KeyPress event, serial 36, synthetic NO, window 0x4c00001, root 0x27a, subw 0x0, time 31268952, (130,-16), root:(1000,525), state 0x10, keycode 62 (keysym 0xffe2, Shift_R), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False KeyPress event, serial 36, synthetic NO, window 0x4c00001, root 0x27a, subw 0x0, time 31269376, (130,-16), root:(1000,525), state 0x11, keycode 38 (keysym 0x41, A), same_screen YES, XLookupString gives 1 bytes: (41) "A" XmbLookupString gives 1 bytes: (41) "A" XFilterEvent returns: False KeyRelease event, serial 36, synthetic NO, window 0x4c00001, root 0x27a, subw 0x0, time 31269584, (130,-16), root:(1000,525), state 0x11, keycode 38 (keysym 0x41, A), same_screen YES, XLookupString gives 1 bytes: (41) "A" XFilterEvent returns: False KeyRelease event, serial 36, synthetic NO, window 0x4c00001, root 0x27a, subw 0x0, time 31269608, (130,-16), root:(1000,525), state 0x11, keycode 62 (keysym 0xffe2, Shift_R), same_screen YES, XLookupString gives 0 bytes: XFilterEvent returns: False shift + d KeyPress event, serial 36, synthetic NO, window 0x4c00001, root 0x27a, subw 0x0, time 31102792, (115,-13), root:(985,528), state 0x10, keycode 62 (keysym 0xffe2, Shift_R), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False FocusOut event, serial 36, synthetic NO, window 0x4c00001, mode NotifyGrab, detail NotifyAncestor FocusIn event, serial 36, synthetic NO, window 0x4c00001, mode NotifyUngrab, detail NotifyAncestor KeymapNotify event, serial 36, synthetic NO, window 0x0, keys: 2 0 0 0 0 0 0 64 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 KeyRelease event, serial 36, synthetic NO, window 0x4c00001, root 0x27a, subw 0x0, time 31103104, (115,-13), root:(985,528), state 0x11, keycode 62 (keysym 0xffe2, Shift_R), same_screen YES, XLookupString gives 0 bytes: XFilterEvent returns: False

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• Wireless (Broadcom) just stopped working after putting machine to sleep!

  - by tommed

  Had the wireless working on my Dell Studio 15 for months now (Ubuntu 10.04 64bit, now 10.10 64bit). But I shut the lid this morning, which put the machine to sleep; when I openend it again the wireless would no longer connect to anything :'( I rebooted the machine, but that didn't help. I then did ifconfig eth1 {down,up}, but that didn't help, then I did iwconfig eth1 power {down,on}, but that didn't work. So I uninstalled the wireless driver (Broadcom STA) from additional drivers (reboot in the middle), but it still won't work anymore!! This is the trace from daemon.log, looks like it is a driver issue? Nov 28 12:26:39 ulap NetworkManager[1218]: (eth1): supplicant connection state: disconnected - scanning Nov 28 12:26:39 ulap NetworkManager[1218]: (eth1): supplicant connection state: scanning - disconnected Nov 28 12:26:45 ulap NetworkManager[1218]: (eth1): supplicant connection state: disconnected - scanning Nov 28 12:26:50 ulap wpa_supplicant[1295]: Trying to associate with MY_MAC_CODE (SSID='MY_WIRESS_SSID' freq=2417 MHz) Nov 28 12:26:50 ulap wpa_supplicant[1295]: Association request to the driver failed Nov 28 12:26:50 ulap NetworkManager[1218]: (eth1): supplicant connection state: scanning - associating Nov 28 12:26:51 ulap wpa_supplicant[1295]: Associated with MY_MAC_CODE Nov 28 12:26:51 ulap NetworkManager[1218]: (eth1): supplicant connection state: associating - associated Nov 28 12:27:01 ulap wpa_supplicant[1295]: Authentication with MY_MAC_CODE timed out. Nov 28 12:27:01 ulap NetworkManager[1218]: (eth1): supplicant connection state: associated - disconnected Anyone seen this, or know how I can get around this issue? It had been working fine up until now?! Even ran update-manager, but there wasn't any changes to the wireless drivers (or any related networking areas). Running the most up-to-date version of 10.10 x64. My android phone and other devices are still working on the wireless.

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• multiple droppable

  - by Sune

  Ive have multiple droppable divs (which all have the same size) and one draggable div. The draggable div is 3 times bigger than one droppable. When I drag the draggable div on the droppables divs I want to find which droppable has been affeckted. My code looks like this: $(function () { $(".draggable").draggable({ drag: function (event, ui) { } }); $(".droppable").droppable({ drop: function (event, ui) { alert(this.id); } }); }); the html <div style="height:100px; width:200px; border-bottom:1px solid red; " id="Div0" class="droppable"> drop in me1! </div> <div style="height:100px; width:200px; border-bottom:1px solid red;" id="Div1" class="droppable"> drop in me2! </div> <div style="height:100px; width:200px; border-bottom:1px solid red; " id="Div2" class="droppable"> drop in me2! </div> <div style="height:100px; width:200px; border-bottom:1px solid red; " id="Div3" class="droppable"> drop in me2! </div> <div style="height:100px; width:200px; border-bottom:1px solid red; " id="Div4" class="droppable"> drop in me2! </div> <div style="height:100px; width:200px; border-bottom:1px solid red; " id="Div5" class="droppable"> drop in me2! </div> <div style="height:100px; width:200px; border-bottom:1px solid red; " id="Div6" class="droppable"> drop in me2! </div> <div style="height:100px; width:200px; border-bottom:1px solid red; " id="Div7" class="droppable"> drop in me2! </div> <div class="draggable" id="drag" style="height:300px; width:50px; border:1px solid black;"><span>Drag</span></div> But my alert only shows the first which my draggable div (Div0) hits, how can I find the missing (Div1 and Div2), which also is affeckted?? Here's a guy with the same problem : http://forum.jquery.com/topic/drop-onto-multiple-droppable-elements-at-once

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• Internet Explorer background-color hover problem

  - by danilo

  I have a strange Problem with table formating using IE 7. My table looks like this: In IE, when using border-collapse, the borders don't get displayed correctly. That's why I used this fix: .table-vmlist td { border-top: 1px solid black; } td.col-vm-status, tr.row-details td { border-left: 1px solid black; } td.col-vm-rdp, tr.row-details td { border-right: 1px solid black; } .table-vmlist { border-bottom: 1px solid black;} When hovering over the row, it gets highlighted with CSS: .table-vmlist tr.row-vm { background-color: #A4C3EF; } .table-vmlist tr.row-vm:hover { background-color: #91BAEF; } Now, in IE 7, when moving the mouse from the top to the bottom of the list, every row gets highlighted correctly and no problems happen. But if I move my mouse pointer from the bottom of the list to the top, every second row seems to loose the border. Can someone explain what the problem is, and how to solve it? This is my markup: <tr class="row-vm"> <td class="col-vm-status status-1"><img title="Host Down" alt="Down" src="/Technik/vm-management/img/hoststatus_1.png"></td> <td class="col-vm-name">V1-VM-1</td> <td class="col-vm-stati"> <img title="Ping" alt="Ping status" src="/Technik/vm-management/img/servicestatus_3.png"> <img title="CPU" alt="CPU status" src="/Technik/vm-management/img/servicestatus_3.png"> <img title="RAM" alt="RAM status" src="/Technik/vm-management/img/servicestatus_3.png"> <img title="C:\ Diskspace" alt="Disk space status" src="/Technik/vm-management/img/servicestatus_3.png"> </td> <td class="col-vm-owner">kus</td> <td class="col-vm-purpose">Citrix Testserver</td> <td class="col-vm-ip">-</td> <td class="col-vm-uptime">-</td> <td class="col-vm-rdp">&nbsp;</td> </tr> And the CSS: /* VM-Tabelle formatieren */ .table-vmlist { border-collapse: collapse; } .table-vmlist tr { border: 1px solid black; } .table-vmlist tr.row-header { border: none; } .table-vmlist tr.row-vm { background-color: #A4C3EF; } .table-vmlist tr.row-vm:hover { background-color: #91BAEF; } .table-vmlist th { text-align: left; } .table-vmlist td { } .table-vmlist th, table td { padding: 2px 0px; } /* Spaltenbreite der VM-Tabelle festlegen */ .table-vmlist #col-status { width: 25px; } .table-vmlist #col-stati { width: 90px; } .table-vmlist #col-owner { width: 90px; } .table-vmlist #col-ip { width: 100px; } .table-vmlist #col-uptime { width: 70px; } .table-vmlist #col-rdp { width: 25px; } .table-vmlist tr.row-details td { padding: 0px 10px; } /* Kein Rahmen um verlinkte Bilder */ a img { border-width: 0px; } /* Für Einschaltknopf Hand-Cursor anstatt normalen Pfeil anzeigen */ td.status-1 img { cursor: pointer; } img.ajax-loader { margin-left: 2px; } IE fix: .table-vmlist td { border-top: 1px solid black; } td.col-vm-status, tr.row-details td { border-left: 1px solid black; } td.col-vm-rdp, tr.row-details td { border-right: 1px solid black; } .table-vmlist { border-bottom: 1px solid black;}

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• Operation is not valid due to the current state of the object?

  - by Bill

  I am programming in C#; the code was working about a week ago, however it throws an exception and I don't understand at all what could be wrong with it. Var root = new CalculationNode(); -> Throw exception. In the call stack thats the only thing listed, I've been told that it could be that I need a clean build, but I am open to any ideas or suggestions. Thanks, -Bill Update: Exception's Detail System.InvalidOperationException was unhandled by user code Message=Operation is not valid due to the current state of the object. Source=Calculator.Logic StackTrace: at ~.Calculator.Logic.MyBaseExpressionParser.Parse(String expression) in ~\Source\Calculator.Logic\MyBaseExpressionParser.cs:line 44 at ~.Calculator.Logic.Tests.MyBaseCalculatorServiceTests.BasicMathDivision() in ~\Projects\Tests\Calculator.Logic.Tests\MyBaseCalculatorServiceTests.cs:line 60 InnerException: CalculationNode's code: public sealed calss CalculationNode { public CalculationNode() { this.Left = null; this.Right = null; this.Element = new CalculationElement(); } public CalculationNode Left {get;set;} public CalculationNode Right {get;set;} public CalculationElement Element {get; set;} } CalculationElement's code: public sealed class CalculationElement { public CalculationElement() { Value = string.Empty; IsOperator = false; } public string Value {get; set} public bool IsOperator {get; set} }

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• Why does a change of Session State provider lead to an ASPx page yielding garbage?

  - by Rory Becker

  I have an aspnet webapp which has worked very well up until now. I was recently asked to explore ways of making it scale better. I found that seperation of database and Webapp would help. Further I was told that if I changed my session providing mechanism to SQLServer, I would be able to duplicate the Web Stack to several machines which could each call back to the state server allowing the load to be distirbuted better. This sounds logical. So I created an ASPState database using ASPNet_RegSQL.exe as detailed in many locations across the web and changed the web.config on my app from: <sessionState mode="InProc" cookieless="false" timeout="20" /> To: <sessionState mode="SQLServer" sqlConnectionString="Server=SomeSQLServer;user=SomeUser;password=SomePassword" cookieless="false" timeout="20" /> Then I addressed my app, which presented me with its logon screen and I duly logged in. Once in I was presented, not with the page I was expecting, but with: I can change the sessionstate back and forth. This problem goes away and then comes back based on which set of configuration I use. Why is this happening?

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• Runge-Kutta (RK4) integration for game physics

  - by Kai

  Gaffer on Games has a great article about using RK4 integration for better game physics. The implementation is straightforward but the math behind it confuses me. I understand derivatives and integrals on a conceptual level but I haven't manipulated equations in a long time. Here's the brunt of Gaffer's implementation: void integrate(State &state, float t, float dt) { Derivative a = evaluate(state, t, 0.0f, Derivative()); Derivative b = evaluate(state, t+dt*0.5f, dt*0.5f, a); Derivative c = evaluate(state, t+dt*0.5f, dt*0.5f, b); Derivative d = evaluate(state, t+dt, dt, c); const float dxdt = 1.0f/6.0f * (a.dx + 2.0f*(b.dx + c.dx) + d.dx); const float dvdt = 1.0f/6.0f * (a.dv + 2.0f*(b.dv + c.dv) + d.dv) state.x = state.x + dxdt * dt; state.v = state.v + dvdt * dt; } Can anybody explain in simple terms how RK4 works? Specifically, why are we averaging the derivatives at 0.0f, 0.5f, 0.5f, and 1.0f? How is averaging derivatives up to the 4th order different from doing a simple euler integration with a smaller timestep? After reading the accepted answer below, and several other articles, I have a grasp on how RK4 works. To answer my own questions: Can anybody explain in simple terms how RK4 works? RK4 takes advantage of the fact that we can get a much better approximation of a function if we use its higher-order derivatives rather than just the first or second derivative. That's why the Taylor series converges much faster than Euler approximations. (take a look at the animation on the right side of that page) Specifically, why are we averaging the derivatives at 0.0f, 0.5f, 0.5f, and 1.0f? The Runge-Kutta method is an approximation of a function that samples derivatives of several points within a timestep, unlike the Taylor series which only samples derivatives of a single point. After sampling these derivatives we need to know how to weigh each sample to get the closest approximation possible. An easy way to do this is to pick constants that coincide with the Taylor series, which is how the constants of a Runge-Kutta equation are determined. This article made it clearer for me: http://web.mit.edu/10.001/Web/Course%5FNotes/Differential%5FEquations%5FNotes/node5.html. Notice how (15) is the Taylor series expansion while (17) is the Runge-Kutta derivation. How is averaging derivatives up to the 4th order different from doing a simple euler integration with a smaller timestep? Mathematically it converges much faster than doing many Euler approximations. Of course, with enough Euler approximations we can gain equal accuracy to RK4, but the computational power needed doesn't justify using Euler.

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• ViewStateMode in ASP.Net 4.0

  - by sreejukg

  When asp.net introduced the concept of viewstate, it changed the way how developers maintain the state for the controls in a web page. Until then to keep the track of the control(in classic asp), it was the developer responsibility to manually assign the posted content before rendering the control again. Viewstate made allowed the developer to do it with ease. The developers are not bothered about how controls keep there state on post back. Viewstate is rendered to the browser as a hidden variable __viewstate. Since viewstate stores the values of all controls, as the number of controls in the page increases, the content of viewstate grows large. It causes some websites to load slowly. As developers we need viewstate, but actually we do not want this for all the controls in the page. Till asp.net 3.5, if viewstate is disabled from web.config (using <pages viewstate=”false”/> ..</pages>), then you can not enable it from the control level/page level. Both <%@ Page EnableViewState=”true”…. and <asp:textbox EnableViewState=”true” will not work in this case. Lot of developers demands for more control over viewstate. It will be useful if the developers are able to disable it for the entire page and enable it for only those controls that needed viewstate. With ASP.NET 4.0, this is possible, a happy news for the developers. This is achieved by introducing a new property called ViewStateMode. Let us see, What is ViewStateMode – Is a new property in asp.net 4.0, that allows developers to enable viewstate for individual control even if the parent has disabled it. This ViewStateMode property can contain either of three values Enabled- Enable view state for the control even if the parent control has view state disabled. Disabled - Disable view state for this control even if the parent control has view state enabled Inherit - Inherit the value of ViewStateMode from the parent, this is the default value. To disable view state for a page and to enable it for a specific control on the page, you can set the EnableViewState property of the page to true, then set the ViewStateMode property of the page to Disabled, and then set the ViewStateMode property of the control to Enabled. Find the example below. Page directive - <%@ Page Language="C#"  EnableViewState="True" ViewStateMode="Disabled" .......... %> Code for the control  - <asp:TextBox runat="server" ViewStateMode="Enabled" ............../> Now the viewstate will be disabled for the whole page, but enabled for the TextBox. ViewStateMode gives developers more control over the viewstate.

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• Live Debugging

  - by Daniel Moth

  Based on my classification of diagnostics, you should know what live debugging is NOT about - at least according to me :-) and in this post I'll share how I think of live debugging. These are the (outer) steps to live debugging Get the debugger in the picture. Control program execution. Inspect state. Iterate between 2 and 3 as necessary. Stop debugging (and potentially start new iteration going back to step 1). Step 1 has two options: start with the debugger attached, or execute your binary separately and attach the debugger later. You might say there is a 3rd option, where the app notifies you that there is an issue, referred to as JIT debugging. However, that is just a variation of the attach because that is when you start the debugging session: when you attach. I'll be covering in future posts how this step works in Visual Studio. Step 2 is about pausing (or breaking) your app so that it makes no progress and remains "frozen". A sub-variation is to pause only parts of its execution, or in other words to freeze individual threads. I'll be covering in future posts the various ways you can perform this step in Visual Studio. Step 3, is about seeing what the state of your program is when you have paused it. Typically it involves comparing the state you are finding, with a mental picture of what you thought the state would be. Or simply checking invariants about the intended state of the app, with the actual state of the app. I'll be covering in future posts the various ways you can perform this step in Visual Studio. Step 4 is necessary if you need to inspect more state - rinse and repeat. Self-explanatory, and will be covered as part of steps 2 & 3. Step 5 is the most straightforward, with 3 options: Detach the debugger; terminate your binary though the normal way that it terminates (e.g. close the main window); and, terminate the debugging session through your debugger with a result that it terminates the execution of your program too. In a future post I'll cover the ways you can detach or terminate the debugger in Visual Studio. I found an old picture I used to use to map the steps above on Visual Studio 2010. It is basically the Debug menu with colored rectangles around each menu mapping the menu to one of the first 3 steps (step 5 was merged with step 1 for that slide). Here it is in case it helps: Stay tuned for more... Comments about this post by Daniel Moth welcome at the original blog.

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• How to salvage SQL server 2008 query from KILLED/ROLLBACK state?

  - by littlegreen

  I have a stored procedure that inserts batches of millions of rows, emerging from a certain query, into an SQL database. It has one parameter selecting the batch; when this parameter is omitted, it will gather a list of batches and recursively call itself, in order to iterate over batches. In (pseudo-)code, it looks something like this: CREATE PROCEDURE spProcedure AS BEGIN IF @code = 0 BEGIN ... WHILE @@Fetch_Status=0 BEGIN EXEC spProcedure @code FETCH NEXT ... INTO @code END END ELSE BEGIN -- Disable indexes ... INSERT INTO table SELECT (...) -- Enable indexes ... Now it can happen that this procedure is slow, for whatever reason: it can't get a lock, one of the indexes it uses is misdefined or disabled. In that case, I want to be able kill the procedure, truncate and recreate the resulting table, and try again. However, when I try and kill the procedure, the process frequently oozes into a KILLED/ROLLBACK state from which there seems to be no return. From Google I have learned to do an sp_lock, find the spid, and then kill it with KILL <spid>. But when I try to kill it, it tells me SPID 75: transaction rollback in progress. Estimated rollback completion: 0%. Estimated time remaining: 554 seconds. I did find a forum message hinting that another spid should be killed before the other one can start a rollback. But that didn't work for me either, plus I do not understand, why that would be the case... could it be because I am recursively calling my own stored procedure? (But it should be having the same spid, right?) In any case, my process is just sitting there, being dead, not responding to kills, and locking the table. This is very frustrating, as I want to go on developing my queries, not waiting hours on my server sitting dead while pretending to be finishing a supposed rollback. Is there some way in which I can tell the server not to store any rollback information for my query? Or not to allow any other queries to interfere with the rollback, so that it will not take so long? Or how to rewrite my query in a better way, or how kill the process successfully without restarting the server?

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• Lua and Objective C not running script.

  - by beta

  I am trying to create an objective c interface that encapsulates the functionality of storing and running a lua script (compiled or not.) My code for the script interface is as follows: #import <Cocoa/Cocoa.h> #import "Types.h" #import "lua.h" #include "lualib.h" #include "lauxlib.h" @interface Script : NSObject<NSCoding> { @public s32 size; s8* data; BOOL done; } @property s32 size; @property s8* data; @property BOOL done; - (id) initWithScript: (u8*)data andSize:(s32)size; - (id) initFromFile: (const char*)file; - (void) runWithState: (lua_State*)state; - (void) encodeWithCoder: (NSCoder*)coder; - (id) initWithCoder: (NSCoder*)coder; @end #import "Script.h" @implementation Script @synthesize size; @synthesize data; @synthesize done; - (id) initWithScript: (s8*)d andSize:(s32)s { self = [super init]; self->size = s; self->data = d; return self; } - (id) initFromFile:(const char *)file { FILE* p; p = fopen(file, "rb"); if(p == NULL) return [super init]; fseek(p, 0, SEEK_END); s32 fs = ftell(p); rewind(p); u8* buffer = (u8*)malloc(fs); fread(buffer, 1, fs, p); fclose(p); return [self initWithScript:buffer andSize:size]; } - (void) runWithState: (lua_State*)state { if(luaL_loadbuffer(state, [self data], [self size], "Script") != 0) { NSLog(@"Error loading lua chunk."); return; } lua_pcall(state, 0, LUA_MULTRET, 0); } - (void) encodeWithCoder: (NSCoder*)coder { [coder encodeInt: size forKey: @"Script.size"]; [coder encodeBytes:data length:size forKey:@"Script.data"]; } - (id) initWithCoder: (NSCoder*)coder { self = [super init]; NSUInteger actualSize; size = [coder decodeIntForKey: @"Script.size"]; data = [[coder decodeBytesForKey:@"Script.data" returnedLength:&actualSize] retain]; return self; } @end Here is the main method: #import "Script.h" int main(int argc, char* argv[]) { Script* script = [[Script alloc] initFromFile:"./test.lua"]; lua_State* state = luaL_newstate(); luaL_openlibs(state); luaL_dostring(state, "print(_VERSION)"); [script runWithState:state]; luaL_dostring(state, "print(_VERSION)"); lua_close(state); } And the lua script is just: print("O Hai World!") Loading the file is correct, but I think it messes up at pcall. Any Help is greatly appreciated. Heading

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• C-states and P-states : confounding factors for benchmarking

  - by Dave

  I was recently looking into a performance issue in the java.util.concurrent (JUC) fork-join pool framework related to particularly long latencies when trying to wake (unpark) threads in the pool. Eventually I tracked the issue down to the power & scaling governor and idle-state policies on x86. Briefly, P-states refer to the set of clock rates (speeds) at which a processor can run. C-states reflect the possible idle states. The deeper the C-state (higher numerical values) the less power the processor will draw, but the longer it takes the processor to respond and exit that sleep state on the next idle to non-idle transition. In some cases the latency can be worse than 100 microseconds. C0 is normal execution state, and P0 is "full speed" with higher Pn values reflecting reduced clock rates. C-states are P-states are orthogonal, although P-states only have meaning at C0. You could also think of the states as occupying a spectrum as follows : P0, P1, P2, Pn, C1, C2, ... Cn, where all the P-states are at C0. Our fork-join framework was calling unpark() to wake a thread from the pool, and that thread was being dispatched onto a processor at deep C-state, so we were observing rather impressive latencies between the time of the unpark and the time the thread actually resumed and was able to accept work. (I originally thought we were seeing situations where the wakee was preempting the waker, but that wasn't the case. I'll save that topic for a future blog entry). It's also worth pointing out that higher P-state values draw less power and there's usually some latency in ramping up the clock (P-states) in response to offered load. The issue of C-states and P-states isn't new and has been described at length elsewhere, but it may be new to Java programmers, adding a new confounding factor to benchmarking methodologies and procedures. To get stable results I'd recommend running at C0 and P0, particularly for server-side applications. As appropriate, disabling "turbo" mode may also be prudent. But it also makes sense to run with the system defaults to understand if your application exhibits any performance sensitivity to power management policies. The operating system power management sub-system typically control the P-state and C-states based on current and recent load. The scaling governor manages P-states. Operating systems often use adaptive policies that try to avoid deep C-states for some period if recent deep idle episodes proved to be very short and futile. This helps make the system more responsive under bursty or otherwise irregular load. But it also means the system is stateful and exhibits a memory effect, which can further complicate benchmarking. Forcing C0 + P0 should avoid this issue.

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• Xpath expression to retrieve oldest/earliest node

  - by gkrogers

  I have an XML snippet, so: <STATES> <STATE> <NAME>Alabama</NAME> <ABBREVIATION>AL</ABBREVIATION> <CAPITAL>Montgomery</CAPITAL> <POPULATION>4661900</POPULATION> <AREA>52419</AREA> <DATEOFSTATEHOOD>14 December 1819</DATEOFSTATEHOOD> </STATE> <STATE> <NAME>Alaska</NAME> <ABBREVIATION>AK</ABBREVIATION> <CAPITAL>Juneau</CAPITAL> <POPULATION>698473</POPULATION> <AREA>663268</AREA> <DATEOFSTATEHOOD>1 January 1959</DATEOFSTATEHOOD> </STATE> <STATE> <NAME>Delaware</NAME> <ABBREVIATION>DE</ABBREVIATION> <CAPITAL>Dover</CAPITAL> <POPULATION>885122</POPULATION> <AREA>2490</AREA> <DATEOFSTATEHOOD>7 December 1787</DATEOFSTATEHOOD> </STATE> </STATES> <etc, etc.> I want to retrieve (for example) the capital of the oldest state (i.e. "Dover"). I have managed to get this far: //STATES/STATE[DATEOFSTATEHOOD='7 December 1787']/CAPITAL/text() but can't figure out how to say 'DATEOFSTATEHOOD={the earliest DATEOFSTATEHOOD}'. Can anybody point me in the right direction, please? SOLUTION: Matt's solution is more or less spot on. I had to reformat the dates (I used YYYYMMDDD) because, as was pointed out, Xpath 1.0 doesn't support the date format I was using. Also, Microsoft's XML library (4.0 and 6.0) returned the whole node list with Matt's expression. Reversing the test fixed that problem, making it return just the earliest node. So: //STATES/STATE[(DATEOFSTATEHOOD < //STATES/STATE/DATEOFSTATEHOOD)]/CAPITAL/text()

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• How to salvage SQL server 2008 query from KILLED/ROLLBACK state without waiting half a day?

  - by littlegreen

  I have a stored procedure that inserts batches of millions of rows, emerging from a certain query, into an SQL database. It has one parameter selecting the batch; when this parameter is omitted, it will gather a list of batches and recursively call itself, in order to iterate over batches. In (pseudo-)code, it looks something like this: CREATE PROCEDURE spProcedure AS BEGIN IF @code = 0 BEGIN ... WHILE @@Fetch_Status=0 BEGIN EXEC spProcedure @code FETCH NEXT ... INTO @code END END ELSE BEGIN -- Disable indexes ... INSERT INTO table SELECT (...) -- Enable indexes ... Now it can happen that this procedure is slow, for whatever reason: it can't get a lock, one of the indexes it uses is misdefined or disabled. In that case, I want to be able kill the procedure, truncate and recreate the resulting table, and try again. However, when I try and kill the procedure, the process frequently oozes into a KILLED/ROLLBACK state from which there seems to be no return. From Google I have learned to do an sp_lock, find the spid, and then kill it with KILL <spid>. But when I try to kill it, it tells me SPID 75: transaction rollback in progress. Estimated rollback completion: 0%. Estimated time remaining: 554 seconds. I did find a forum message hinting that another spid should be killed before the other one can start a rollback. But that didn't work for me either, plus I do not understand, why that would be the case... could it be because I am recursively calling my own stored procedure? (But it should be having the same spid, right?) In any case, my process is just sitting there, being dead, not responding to kills, and locking the table. This is very frustrating, as I want to go on developing my queries, not waiting hours on my server sitting dead while pretending to be finishing a supposed rollback. Is there some way in which I can tell the server not to store any rollback information for my query? Or not to allow any other queries to interfere with the rollback, so that it will not take so long? Or how to rewrite my query in a better way, or how kill the process successfully without restarting the server?

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• Keep hover state applied until user mouses over another element.

  - by Thomas

  First let me state that I'm a jquery noob, so this may not make a lot of sense. So I have a series of list items that expand to show a hidden div inside if the user mouses over a link inside the item (not the whole list item itself) The problem is that if the users mouse leaves the link the li closes up again. I need this to work in a way so that the li only closes if you mouse over a link in another li. (sorry this is kind of hard to put into words) Heres my code. $(document).ready(function(){ $(".home_upcoming_title").hoverIntent({ over: makeTall, timeout: 500, out: makeShort }); }); // close document.ready function makeTall(){$(this).parents("li").animate({"height":200},200);} function makeShort(){$(this).parents("li").animate({"height":32},200);} and the HTML <li class="p1"> <ul class="home_upcoming_list2" id="fade"> <li class="home_upcoming_date">Sat.Sept.23rd.2010</li> <li><a href="./." class="home_upcoming_title" >Event Title</a></li> <li class="home_upcoming_city">Los Angeles</li> <li class="home_upcoming_type">Festival</li> <li class="home_upcoming_venue">Venue</li> <li class="home_upcoming_age">18+</li> <li><a href="./." title="Buy Tickets" class="home_upcoming_tix">Buy Tickets</a></li> <li><a href="./." class="upcoming_info" title="View Details"></a></li> </ul> <div style="height:150px; background-color:#FF0000; display:block;" class="sl0w"></div> </li> so the link with the class "home_upcoming_title" expands li to show the div inside but when I mouse over the div itself the list closes. I also need it so only the class "home_upcoming_title" expands the div. but it needs to stay open until you mouse over another link with the same class. sorry if that doesn't make much sense :)

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• How to properly position 3rd level menu [migrated]

  - by drewrowalnd

  If you look here: http://snippetmagazine.com/ under about isl-board of trustees you can se I have created a third level dropdown, but how can I properly align that drop down? Below you will see my css. #menudiv { width: 999px; float: left; clear: left; height: 250px; background: url(images/top_bg.png) no-repeat; margin-top: 10px; } mainmenu { width: 948px; height: 63px; float: left; margin-left: 16px; margin-top:5px; border: 1px solid #D5D5D5; -moz-border-radius: 3px; -webkit-border-radius: 3px; -webkit-box-shadow: 0px 1px 2px rgba(0, 0, 0, 0.1); -moz-box-shadow: 0px 1px 2px rgba(0, 0, 0, 0.1); background:url(images/nav_bg.gif) repeat; } .mainnav { margin: 0; padding: 0; list-style: none; } .mainnav * { margin: 0; padding: 0; list-style: none; } .mainnav ul { position: absolute; top: -999em; display: none; } .mainnav li { float: left; position: relative; z-index: 999; height: 63px; line-height: 55px; margin-right: 0px; border-right: 1px solid #D5D5D5; } .mainnav li.last { border-right: none; } .mainnav a { display: block; font-size: 19px; margin: 0; color: #cc9900; font-family: Copperplate, Arial, Helvetica, Sans serif; font-weight:600; text-decoration: none; padding: 3px 13px 3px 12px; color: #555; text-shadow: 0 1px 1px white; } .mainnav li:hover { text-decoration: none; border-bottom: solid 0px #ccc; background: white; } .mainnav ul li{ width: 132px; } .mainnav li:hover ul, ul.mainnav li.sfHover ul { left: 0px; top: 50px; padding-top: 0px; width: 132px; border-bottom: solid 0px #eaeaea; background: url(images/nav_dropdown_shadow.gif) repeat-x top; padding: 6px 0 0px 0px; margin: 13px 0 0 -1px; border: 1px solid #D5D5D5; -moz-border-radius-bottomleft: 3px; -webkit-border-bottom-left-radius: 3px; -moz-border-radius-bottomright: 3px; -webkit-border-bottom-right-radius: 3px; -webkit-box-shadow: 0px 1px 3px rgba(0, 0, 0, 0.1); -moz-box-shadow: 0px 1px 3px rgba(0, 0, 0, 0.1); width: 175px; border-bottom-left-radius: 3px 3px; border-bottom-right-radius: 3px 3px; } .mainnav li:hover li ul, .mainnav li.sfHover li ul { top: -999em; } .mainnav li li:hover ul, ul.mainnav li li.sfHover ul { left: 132px; top: -8px; } .mainnav li:hover ul, .mainnav li li:hover ul { top: -999em; } .mainnav li li { color: #555; display: block; padding: 0px; height: auto !important; border: none; width:175px; background: url(images/nav_dropdown_bg.gif) repeat; margin: 0; } .mainnav li li a:link, .mainnav li li a:visited { display: block; height: auto !important; line-height: 30px; color: #333; font-weight: normal; font-family: arial, helvetica, sans-serif; font-size: 12px; border: none; margin: 0; padding-left: 10px; overflow:hidden; border-bottom: 1px solid #E3E3E3; } .mainnav li li :hover{ } .mainnav li li a:hover { background: none; color:#555 ; border-bottom: 1px solid #E3E3E3; }

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• Not sure what happens to my apps objects when using NSURLSession in background - what state is my app in?

  - by Avner Barr

  More of a general question - I don't understand the workings of NSURLSession when using it in "background session mode". I will supply some simple contrived example code. I have a database which holds objects - such that portions of this data can be uploaded to a remote server. It is important to know which data/objects were uploaded in order to accurately display information to the user. It is also important to be able to upload to the server in a background task because the app can be killed at any point. for instance a simple profile picture object: @interface ProfilePicture : NSObject @property int userId; @property UIImage *profilePicture; @property BOOL successfullyUploaded; // we want to know if the image was uploaded to out server - this could also be a property that is queryable but lets assume this is attached to this object @end Now Lets say I want to upload the profile picture to a remote server - I could do something like: @implementation ProfilePictureUploader -(void)uploadProfilePicture:(ProfilePicture *)profilePicture completion:(void(^)(BOOL successInUploading))completion { NSUrlSession *uploadImageSession = ..... // code to setup uploading the image - and calling the completion handler; [uploadImageSession resume]; } @end Now somewhere else in my code I want to upload the profile picture - and if it was successful update the UI and the database that this action happened: ProfilePicture *aNewProfilePicture = ...; aNewProfilePicture.profilePicture = aImage; aNewProfilePicture.userId = 123; aNewProfilePicture.successfullyUploaded = NO; // write the change to disk [MyDatabase write:aNewProfilePicture]; // upload the image to the server ProfilePictureUploader *uploader = [ProfilePictureUploader ....]; [uploader uploadProfilePicture:aNewProfilePicture completion:^(BOOL successInUploading) { if (successInUploading) { // persist the change to my db. aNewProfilePicture.successfullyUploaded = YES; [Mydase update:aNewProfilePicture]; // persist the change } }]; Now obviously if my app is running then this "ProfilePicture" object is successfully uploaded and all is well - the database object has its own internal workings with data structures/caches and what not. All callbacks that may exist are maintained and the app state is straightforward. But I'm not clear what happens if the app "dies" at some point during the upload. It seems that any callbacks/notifications are dead. According to the API documentation- the uploading is handled by a separate process. Therefor the upload will continue and my app will be awakened at some point in the future to handle completion. But the object "aNewProfilePicture" is non existant at that point and all callbacks/objects are gone. I don't understand what context exists at this point. How am I supposed to ensure consistency in my DB and UI (For instance update the "successfullyUploaded" property for that user)? Do I need to re-work everything touching the DB or UI to correspond with the new API and work in a context free environment?

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