We've got a requirement to determine whether the user is waiting on a program to do something. The biggest issue I see here is, if I monitor user activity (Keyboard and Mouse) then I'll assume the user is waiting when they might be reading, thinking, on the phone, etc.
Sometimes, if I know I'm going to have to wait a long time on a process (like booting up), I'll go get a coffee whilst it loads. I'm not really waiting on any one program, I'm just being efficient with my time.
I'm open to any ideas, even requesting the user use a key or key-combination to indicate they're waiting.
Is there a way to determine whether a user is waiting on a program?
Give the user the illusion that they could do the next step of interaction, i.e. don't tell them right away that the previous action has not completed. Then, when they try do something, you'll notice that they really would like to do something now and hence are waiting if they can't.
In some cases, you may find that what they want to do can actually be done right away, despite the previous action still being in progress.
You can't tell what a non-interacting user is doing. They could be day dreaming and you'd have no idea if they were waiting on the computer or not.
You might be able to deduce from user interaction that a user was waiting when you see no activity during a period of time when disk and or CPU usage is high. But this is not a scientific measure, it's merely an indicator. The assumption that the user was waiting negates the possibility to use the results for meaningful measurements.
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My understanding is that a non-maskable interrupt enforces context switching (which causes a process to be moved from CPU to ready queue). If the interrupt happens at a time when the process is executing its critical section, it may make the output indeterministic. One solution is to roll back to the state when the process entered the critical section, but I don't know if that is possible. Please help clarify this. Thanks in advance!
If there would be a way that roll back would happen, I honestly do not know.
Yes, there is ways of doing so by software of course, the developer could implement guards in his/her code to check if there is an anomaly if so they are will repeat the process again to avoid the corrupted data.
I have a little issue with a form in a delphy XE2 application:
It's an old issue on this application and i have begin to work on it just since a little time.
When the user choose to launch the process with a button's event, my application launch a connexion with an OPCServer , an SQLServer and construct the form for a good following of data take on the tow servers.
The construction of my form involves a blockage of the interface (for approximately 15 sec) because of lot's of data which are necessary for make it.
When it freeze, if the user want drag the form, she go far away, and usually with the TMainMenu which go out of the screen. After that, it's impossible to use the application because we can't drag and we need to close and re-open.
In the old version, the form be already construct before the connexion. So the modification for a dynamic form isn't in link with this issue.
Life of my event :
-Open connexion with OPC Server
-Open SQL Connexion
-Send SQL Command Text
-FieldByName('') for update my UI (Button.Caption// TPage.TStaticText.Caption // TPage.Label1.Caption)
-FieldByName('') for update an array of record
-Close SQL Connexion
-Open SQL Connexion
-Send SQL CommandText
-FieldByName('') for update an other array of record
-Panel.Visible(false)
-TPage.Panel.Show;
-TPage.Panel.BringToFront;
So I haven't MainForm modification can change its position.
I'm a young developer, so I don't know why it moving and what I can make for repair that...
If you want a part of code, ask me what and i edit this, it's very long and i don't want spam answer.
Thank's for read.
The core of your problem is that you have a lengthy process (form construction) which completely blocks the main thread so your application isn't able to process normal Windows messages at the same time. That is why when you move your application it doesn't properly update its interface.
Now based on your description you already have this form construction process split into multiple steps so you could call Application.ProcessMessages between them.
This will force your application to update its UI part.
But beware calling Application.ProcessMessages often could hurt your application performance quite a bit. Why? It is usually a lengthy process because it forces your application to process all the messages that are in its queue.
Normally not all of these messages get processed as soon as they arrive. Windows groups them in the message queue by their priority list, making sure that high priority messages like WM_PAINT are processed as soon as possible while some other low priority messages like demand for application to respond to OS so that OS can see if the application is still working are mostly processed when application is idle or when they are in queue for certain amount of time.
So that is why Application.ProcessMessages can be so slow as it forces your application to process all messages regardless of their priority.
Also bear in mind that using Application.ProcessMessages can in certain scenarios actually become a bit dangerous.
Let me give you an example:
Lets say that clicking on a button starts a lengthy job which can take some time to finish. Now in order to allow your form to be updated you call Application.ProcessMessages in certain intervals. So far it is all good. But what happens if user clicks on that button again?
Since you are calling Application.ProcessMessages which forces your application to process all the messages and since clicking on button creates a MouseClick message which then fires buttons OnClick event which then executes the OnClick method that has been assigned to buttons OnClick event in the end this will cause the same method that was executed on first button click to be executed again.
So now you have this method partially done from first button click and same method executing again for second mouse click. Now the method that was executed from the second click will finish first and then the method that was started from first button click but was interrupted with Application.ProcessMessages handling the second button click will continue its execution to the end.
This all can lead to strange bugs which are hard to track, because you as a programmer normally don't predict that your end user might have clicked the button twice.
So to avoid this I strongly recommend you implement some safeguard mechanisms to prevent such scenarios by temporarily disabling a button for instance.
But the best solution is always to show your user that your application is working which in most cases will dissuade them from clicking the button again, but unfortunately not always.
You should also take a good care when dynamically constructing a form to enable the controls only after all of the controls have been successfully constructed. Failing to do so the user might click on one of your controls and that control could attempt to access some other control which hasn't yet been created at the time. The result hard to track bug which causes Access Violation.
You might also consider showing a splash screen at start instead of half built form. Why?
For once it is much nicer to see and it tells your users to wait a bit. And for second having main form hidden until it is fully created makes sure that user won't be doing any clicks on it prematurely.
When launching my app from a custom URL scheme, when app is not backgrounded, the launch sequence is taking longer then I would like. I want to use time profiler to see what methods are taking so long. I know on run there is an option for "Wait for App Launch" so I can launch it using the URL, but I don't see that under the profiling scheme. Does anyone know a way that I can launch the app fresh, using the URL, and have time profiler running on launch?
"see what methods are taking so long"
Do you suppose some method (or a few) are sopping up a lot of CPU time in themselves or by calling other methods that do?
If so, it will be easy to fix, but it's Not Likely.
More likely the time is spent in I/O of one sort or another, and you need to figure out why, not where.
If you're able to start it under a debugger (say by using #ChrisTruman's recommendation), then all you need to do is interrupt it with Ctrl-C, Ctrl-Break, Escape, or whatever key combination interrupts it.
Do this during the time when, subjectively, it is slow.
Let's suppose the startup is taking three times longer than you think it should.
If that's so, that means two thirds of the time is spent doing the unnecessary I/O or whatever it is.
That means each time you interrupt it, the probability is 2/3 that you will catch it in the act of doing whatever causes the slowness.
So interrupt it a few times, and each time just read the stack, look at variables, etc.
You will see why it's being slow.
Don't even look for where - that will appear by itself.
That's the basic idea behind this technique.
I am trying to figure out how to use a background thread to execute a command ever 4hrs.
I have never created anything like this before so have only been reading about it so far.. One of the things I have read are this
"Threads tie up physical memory and critical system resources"
So in that case would it be a bad idead to have this thread that checkes the time then executes my method... or is there a better option, I have read about GCD (Grand Central Dispatch) but I am not sure if this is applicable as I think its more for concurrent requests? not something that repeats over and over again checking the time..
Or finally is there something I have completely missed where you can execute a request every 4hrs?
Any help would be greatly appreciated.
There is a max time background processes are allowed to run (10 min) which would make your approach difficult. Your next best attempt is to calculate the next event as save the times tamp somewhere. Then if the app is executed at or after that event it can carry out whatever action you want.
This might help:
http://www.audacious-software.com/2011/01/ios-background-processing-limits/
I think that it would be good to make use of a time stamp and post a notification for when the time reaches for hours from now.
Multithreading is not a good means to do this because essentially you would be running a loop for four hours eating clock cycles. Thanks to the magic of operating systems this would not eat up an entire core or anything silly like that however it would be continuously computed if it was allowed to run. This would be a vast waste of resources so it is not allowed. GCD was not really meant for this kind of thing. It was meant to allow for concurrency to smooth out UI interaction as well as complete tasks more efficiently, a 4hr loop would be inefficent. Think of concurrency as a tool for something like being able to interact with a table while its content is being loaded or changed. GCD blocks make this very easy when used correctly. GCD and other multithreading abilities give tools to do calculations in the background as well as interact with databases and deal with requests without ever affecting the users experience. Many people whom are much smarter then me have written exstensively on what multithreading/multitasking is and what it is good for. In a way posting a message for a time would be method of multitasking without the nastiness of constantly executing blocks through GCD to wait for the 4 hr time period, however it is possible to do this. You could execute a block that monitored for time less then the max length of a threads lifetime then when the threads execution is over dispatch it again until the desired time is achieved. This is a bad way of doing this. Post a notification to the notification center, its easy and will accomplish your goal without having to deal with the complexity of multithreading yourself.
You can post a notification request observing for a time change and it will return its note, however this requires you application be active or in the background. I can not guarantee the OS wont kill your application however if it is nice and quiet with a small memory footprint in "background" state its notification center request will remain active and function as intended.
Let's say, Tiny Tower. On this iPhone game, you can have shops in your tower. You can suspend or turn off the iPhone, but when you return to the game, you will be reported about the shop winnings during your time away.
There are also push notifications when a building is complete etc.
I fear I do not understand how that works, exactly. I'm not asking for the exact solution, I just need to know where to begin researching. One idea I had some time ago was like calculate the amount of seconds the user was away (current time minus the time when you left) and then calculate shop processing for every one of these seconds. But I'm not sure of that.
A better way would be to calculate before you close the app.
Figure out what time it is, then calculate when in the future certain tasks will be completed. This way, you can schedule push notifications to the server ahead of time.
If you calculate after you have re-opened the app, and you can't run processes with the app closed, how will it know when to push?
Take a look at this article about push notifications to understand a little bit better how they work.
http://blog.boxedice.com/2009/07/10/how-to-build-an-apple-push-notification-provider-server-tutorial/
For offline games you add temporal logic to your items and recalculate when game is launched. For online games you retrieve game state from the server, which is constantly recalculating for all users, even disconnected ones.
Game most probably does not actually process in the background (most apps are not allowed to do anything while in background). When you relaunch the game, it calculates how much time has passed, and then processes all the events that would have happened in the meantime.
Additionally, as Paul.s mentioned in comments below, as well as other people in other answers have suggested, on iOS4 you can use local push notifications scheduled before close.
It is either server side execution of the game or if it is a game of chance or something like Farmville where it's determined by time duration.
If you were to make a server and/or game like this then you would need to decide which route to take.
If it will be something where the user has good days and sometimes bad days then you'll need a lot more server power. however, if it's something like time based then you would be able to tell the last time they were logged in and the next time that they should be awarded. you can also take this idea and for each variable that you store, you store how long it takes to be complete and the start time. Then you would do a simple If then o see if the item is ready. The same thing can work for a number of visitors. Where you have 10 visitors per item per hour. If you have two items then each hour you will receive 20 visitors.