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  • WPF ListView.CurrentChanged too fast for binding

    - by matt
    My case: MVVM ListView+Details(custom UserControl) List bound to MV.Items (IsSynchronizedWithCurrent=true) Details bound to MV.Items.Current MV.Items.Count == 100 about 0.2sec to read details (lazy mode) When I hold the down arrow on the list, very strange things happen: list items order change current changes in the random order CPU usage drastically increments and eventually all hangs. I've read some post that one should start the timer or run handler in the background, but I am not able to do that, since all the binding WPF does for me. Is there some way to instruct the binding in my DetailsControl, to wait a while before accepting CurrentItem? Or should I just resign from the clean solution and write custom code in my MV to handle that?

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  • Is a signal sent with kill to a parent thread guaranteed to be processed before the next statement?

    - by Jonathan M Davis
    Okay, so if I'm running in a child thread on linux (using pthreads if that matters), and I run the following command kill(getpid(), someSignal); it will send the given signal to the parent of the current thread. My question: Is it guaranteed that the parent will then immediately get the CPU and process the signal (killing the app if it's a SIGKILL or doing whatever else if it's some other signal) before the statement following kill() is run? Or is it possible - even probable - that whatever command follows kill() will run before the signal is processed by the parent thread?

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  • Very long strings as primary keys in a database for caching

    - by Bill Zimmerman
    Hi, I am working on a web app that allows users to create dynamic PDF files based on what they enter into a form (it is not very structured data). The idea is that User 1 enters several words (arbitrary # of words, practically capped of course), for example: A B C D E There is no such string in the database, so I was thinking: Store this string as a primary key in a MySQL database (it could be maybe around 50-100k of text, but usually probably less than 200 words) Generate the PDF file, and create a link to it in the database When the next user requests A B C D E, then I can just serve the file instead of recreating it each time. (simple cache) The PDF is cpu intensive to generate, so I am trying to cache as much as I can... My questions are: Does anyone have any alternative ideas to my approach What will the database performance be like? Is there a better way to design the schema than using the input string as the primary key?

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  • VB.NET - Read lines from command line to Windows form possible?

    - by Yiu Korochko
    Hey Overflow, I have an application which serves as a user interface for a spartan/command line program. I have the program running on a separate process, and my application monitors it to see if it is responding and how mush CPU it is utilising. Now I have a list of files in my program (listbox) which are to be sent to the application, which happens fine. But I want to be able to read text from the com-line so as to determine when the first file has been processed. Com-line says one of "selecting settings", "unsupported format" and "cannot be fixed". What I want to be able to do is when it says one of these three things, remove item(0) in listbox1. Is this possible? I thought of programming an event which handles com_exe.print or something or other, if possible.

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  • Only some windows shell commands work via ruby?

    - by Sanarothe
    Hi. I'm trying to use a script to control my power options since XP doesn't give you an intuitive way to change CPU Frequency options. Here's my script so far: meh = `cmd.exe /C POWERCFG.EXE /QUERY Portable/Laptop` puts "" puts meh case input when 1 then system('cmd.exe /C POWERCFG.EXE /CHANGE Portable/Laptop /processor-throttle-ac NONE') when 2 then system('cmd.exe /C POWERCFG.EXE /CHANGE Portable/Laptop /processor-throttle-ac ADAPTIVE') when 3 then `cmd.exe /C POWERCFG.EXE /CHANGE Portable/Laptop /processor-throttle-ac CONSTANT` end The problem is that the changes simply don't take place. If I run the same commands directly into a cmd.exe prompt, they work. It's very strange, but nothing works after the initial powercfg query. I feel like I'm missing something incredibly obvious. How can I get the above script to run correctly?

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  • rundll32.exe constantly running taking up resources slowing down my Win 7 computer

    - by Joe Fletcher
    Over the past week, my Windows 7 Home Premium computer (8gb RAM, 64bit) has been running slowly. When I look at my processes, there are always 2 rundll32.exe's running taking up 3 & 25% CPU power, memory slowly creeping upwards from around 115mb to 160mb each in the time it has taken me to right this message, sometimes popping upt o 300mb and back down. Svchost.exe is at 260mb. When I end those processes, everything returns to snappiness. I recently did some Windows Updates, and I think it was around the time my computer started acting slowly, but I can't remember if it was before or after the updates that things started running slowly. Last night I ccleaned & defrag'ed. How can I diagnose what's causing the slowness?

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  • What can be done to speed up synchronous WCF calls?

    - by Dimitri C.
    My performance measurements of synchronous WCF calls from within a Silverlight application showed I can make 7 calls/s on a localhost connection, which is very slow. Can this be speeded up, or is this normal? This is my test code: const UInt32 nrCalls = 100; ICalculator calculator = new CalculatorClient(); // took over from the MSDN calculator example for (double i = 0; i < nrCalls; ++i) { var call = calculator.BeginSubtract(i + 1, 1, null, null); call.AsyncWaitHandle.WaitOne(); double result = calculator.EndSubtract(call); } Remarks: CPU load is almost 0%. Apparently, the WCF module is waiting for something. I tested this both on Firefox 3.6 and Internet Explorer 7. I'm using Silverlight v3.0

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  • Who Knows AppWeb HTTP Server And It's Embedded PHP?

    - by Andi
    Hi all, on my search for a fast but comfortable web server I dropped into the homepage of EmbedThis(TM) AppWeb(TM) HTTP server. This one has 2 licencse models, GPLv2 and a commercial one with support. On the first view it looks good: the footprint is not too big, it is fast and it has a lot of configuration otions. The most important thing would be a fast PHP execution using a built-in PHP library. Unfortunately this PHP library doesn't include every option, especially "gettext" which one I need for I18N. My target platform is Linux on an embedded device with an ARM based CPU. Does anybody have experiences with the issues mentioned above? Kind regards, Andi

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  • Branchless memory manager?

    - by Richard Fabian
    Anyone thought about how to write a memory manager (in C++) that is completely branch free? I've written a pool, a stack, a queue, and a linked list (allocating from the pool), but I am wondering how plausible it is to write a branch free general memory manager. This is all to help make a really reusable framework for doing solid concurrent, in-order CPU, and cache friendly development. Edit: by branchless I mean without doing direct or indirect function calls, and without using ifs. I've been thinking that I can probably implement something that first changes the requested size to zero for false calls, but haven't really got much more than that. I feel that it's not impossible, but the other aspect of this exercise is then profiling it on said "unfriendly" processors to see if it's worth trying as hard as this to avoid branching.

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  • Programmatic resource monitoring per process in Linux

    - by tuxx
    Hi, I want to know if there is an efficient solution to monitor a process resource consumption (cpu, memory, network bandwidth) in Linux. I want to write a daemon in C++ that does this monitoring for some given PIDs. From what I know, the classic solution is to periodically read the information from /proc, but this doesn't seem the most efficient way (it involves many system calls). For example to monitor the memory usage every second for 50 processes, I have to open, read and close 50 files (that means 150 system calls) every second from /proc. Not to mention the parsing involved when reading these files. Another problem is the network bandwidth consumption: this cannot be easily computed for each process I want to monitor. The solution adopted by NetHogs involves a pretty high overhead in my opinion: it captures and analyzes every packet using libpcap, then for each packet the local port is determined and searched in /proc to find the corresponding process. Do you know if there are more efficient alternatives to these methods presented or any libraries that deal with this problems?

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  • Parallelism in Python

    - by fmark
    What are the options for achieving parallelism in Python? I want to perform a bunch of CPU bound calculations over some very large rasters, and would like to parallelise them. Coming from a C background, I am familiar with three approaches to parallelism: Message passing processes, possibly distributed across a cluster, e.g. MPI. Explicit shared memory parallelism, either using pthreads or fork(), pipe(), et. al Implicit shared memory parallelism, using OpenMP. Deciding on an approach to use is an exercise in trade-offs. In Python, what approaches are available and what are their characteristics? Is there a clusterable MPI clone? What are the preferred ways of achieving shared memory parallelism? I have heard reference to problems with the GIL, as well as references to tasklets. In short, what do I need to know about the different parallelization strategies in Python before choosing between them?

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  • can't start MySql in Mac OS 10.6 Snow Leopard

    - by nacho4d
    I've googled this and could'nt find anything new and useful for Apple's new OS SnowLeopard. I wonder if this is my mistake or I do need to do something? this is what I did: Downloaded from mysql site: http://dev.mysql.com/downloads/mysql/5.1.html#macosx-dmg I choose : Mac OS X 10.5 (x86_64) I run all the packages and installed all of them. So now I certainly have mysql in /usr/local/mysql/ But when trying to start it from preferences panel, it is always STOPPED. When I try to do (in the terminal): /usr/local/mysql/bin/mysql I got : -bash: /usr/local/mysql/bin/mysql: Bad CPU type in executable What is wrong here? Any help would be very appreciated. Thanks

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  • How to clean sys.conversation_endpoints

    - by Manjoor
    I have a table, a trigger on the table implemented using service broker. More than Half million records are inserted daily into the table. The asynchronous SP is used to check sveral condition by using inserted data and update other tables. It was running fine for last 1 month and the SP was get executed withing 2-3 seconds of insertion of record. But now it take more than 90 minute. At present sys.conversation_endpoints have too much records. (Note that all the table are truncated daily as I do not need those records day after) Other database activities are normal (average 60% CPU Utilization). Now where i need to look?? I can re-create database without any problem but i don't think it is a good way to resolve the problem

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  • Python Threading

    - by anteater7171
    I'm trying to make a simple program that continually displays and updates a label that displays the CPU usage, while having other unrelated things going on. I've done enough research to know that threading is likely going to be involved. However, I'm having trouble applying what I've seen in simple examples of threading to what I'm trying to do. What I currently have going: import Tkinter import psutil,time from PIL import Image, ImageTk class simpleapp_tk(Tkinter.Tk): def __init__(self,parent): Tkinter.Tk.__init__(self,parent) self.parent = parent self.initialize() def initialize(self): self.labelVariable = Tkinter.StringVar() self.label = Tkinter.Label(self,textvariable=self.labelVariable) self.label.pack() self.button = Tkinter.Button(self,text='button',command=self.A) self.button.pack() def A (self): G = str(round(psutil.cpu_percent(), 1)) + '%' print G self.labelVariable.set(G) def B (self): print "hello" if __name__ == "__main__": app = simpleapp_tk(None) app.mainloop() In the above code I'm basically trying to get command A continually running, while allowing command B to be done when the users presses the button.

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  • Streaming audio - where to start?

    - by Adam Davis
    I need to develop an embedded audio streaming server. Requirements: Voice quality or better Intended for low power wifi transmission Broad support in existing software and devices (ie, windows media player, quicktime, vlc, iPhone, Android, etc). Royalty/patent free, or cheap to license Preferences: Low overhead TCP/IP based streaming protocol Voice grade codec (easy to implement in software, no DSP, 32bit CPU if needed) Would be nice if it supported HTML5 browsers, but is there any codec (such as raw) that is supported by the latest browsers that is lower overhead than MP3? Therefore: What are the relevant streaming protocols I should be looking at? What are the relevant codecs I should be looking at? What transport streams should I be looking at? What am I missing, or where else should I be looking for this type of need?

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  • How would I UPDATE these table entries with SQL and PHP?

    - by CT
    I am working on an Asset Database problem. I enter assets into a database. Every object is an asset and has variables within the asset table. An object is also a type of asset. In this example the type is server. Here is the Query to retrieve all necessary data: SELECT asset.id ,asset.company ,asset.location ,asset.purchaseDate ,asset.purchaseOrder ,asset.value ,asset.type ,asset.notes ,server.manufacturer ,server.model ,server.serialNumber ,server.esc ,server.warranty ,server.user ,server.prevUser ,server.cpu ,server.memory ,server.hardDrive FROM asset LEFT JOIN server ON server.id = asset.id WHERE asset.id = '$id' I then assign all results into single php variables. How would I write a query/script to update an asset?

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  • Watching a variable for changes without polling.

    - by milkfilk
    I'm using a framework called Processing which is basically a Java applet. It has the ability to do key events because Applet can. You can also roll your own callbacks of sorts into the parent. I'm not doing that right now and maybe that's the solution. For now, I'm looking for a more POJO solution. So I wrote some examples to illustrate my question. Please ignore using key events on the command line (console). Certainly this would be a very clean solution but it's not possible on the command line and my actual app isn't a command line app. In fact, a key event would be a good solution for me but I'm trying to understand events and polling beyond just keyboard specific problems. Both these examples flip a boolean. When the boolean flips, I want to fire something once. I could wrap the boolean in an Object so if the Object changes, I could fire an event too. I just don't want to poll with an if() statement unnecessarily. import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; /* * Example of checking a variable for changes. * Uses dumb if() and polls continuously. */ public class NotAvoidingPolling { public static void main(String[] args) { boolean typedA = false; String input = ""; System.out.println("Type 'a' please."); while (true) { InputStreamReader isr = new InputStreamReader(System.in); BufferedReader br = new BufferedReader(isr); try { input = br.readLine(); } catch (IOException ioException) { System.out.println("IO Error."); System.exit(1); } // contrived state change logic if (input.equals("a")) { typedA = true; } else { typedA = false; } // problem: this is polling. if (typedA) System.out.println("Typed 'a'."); } } } Running this outputs: Type 'a' please. a Typed 'a'. On some forums people suggested using an Observer. And although this decouples the event handler from class being observed, I still have an if() on a forever loop. import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.Observable; import java.util.Observer; /* * Example of checking a variable for changes. * This uses an observer to decouple the handler feedback * out of the main() but still is polling. */ public class ObserverStillPolling { boolean typedA = false; public static void main(String[] args) { // this ObserverStillPolling o = new ObserverStillPolling(); final MyEvent myEvent = new MyEvent(o); final MyHandler myHandler = new MyHandler(); myEvent.addObserver(myHandler); // subscribe // watch for event forever Thread thread = new Thread(myEvent); thread.start(); System.out.println("Type 'a' please."); String input = ""; while (true) { InputStreamReader isr = new InputStreamReader(System.in); BufferedReader br = new BufferedReader(isr); try { input = br.readLine(); } catch (IOException ioException) { System.out.println("IO Error."); System.exit(1); } // contrived state change logic // but it's decoupled now because there's no handler here. if (input.equals("a")) { o.typedA = true; } } } } class MyEvent extends Observable implements Runnable { // boolean typedA; ObserverStillPolling o; public MyEvent(ObserverStillPolling o) { this.o = o; } public void run() { // watch the main forever while (true) { // event fire if (this.o.typedA) { setChanged(); // in reality, you'd pass something more useful notifyObservers("You just typed 'a'."); // reset this.o.typedA = false; } } } } class MyHandler implements Observer { public void update(Observable obj, Object arg) { // handle event if (arg instanceof String) { System.out.println("We received:" + (String) arg); } } } Running this outputs: Type 'a' please. a We received:You just typed 'a'. I'd be ok if the if() was a NOOP on the CPU. But it's really comparing every pass. I see real CPU load. This is as bad as polling. I can maybe throttle it back with a sleep or compare the elapsed time since last update but this is not event driven. It's just less polling. So how can I do this smarter? How can I watch a POJO for changes without polling? In C# there seems to be something interesting called properties. I'm not a C# guy so maybe this isn't as magical as I think. private void SendPropertyChanging(string property) { if (this.PropertyChanging != null) { this.PropertyChanging(this, new PropertyChangingEventArgs(property)); } }

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  • Clojure lots of threads

    - by Timothy Baldridge
    I just got done watching Rick Hickey's "Clojure Concurrency" talk, and I have a few questions about threads. Let's say I have a situation with lots of Agents, let's say 10,000 of them running one machine. I'd rather not have 10,000 CPU threads running at once, but I don't want threads to be blocked by the actions of other threads. In this example I won't really be waiting for replies, instead each Agent will be sending a message or two, and then waiting until it gets a message. How would I structure a program like this without getting 10k OS threads which would probably end up slowing the system down.

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  • what's faster: merging lists or dicts in python?

    - by tipu
    I'm working with an app that is cpu-bound more than memory bound, and I'm trying to merge two things whether they be sets or dicts. Now the thing is i can choose either one, but I'm wondering if merging dicts would be faster since it's all in memory? Or is it always going to be O(n), n being the size of the smaller set. The reason I asked about dicts rather than sets is because I can't convert a set to json, because that results in {key1, key2, key3} and json needs a key/value pair, so I am using a dict so json dumps returns {key1:1, key2:1, key3:1}. Yes this is wasteful, but if it proves to be faster then I'm okay with it.

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  • Is MacBook powerful enough to do Ipad development? or do I need a MacBook Pro?

    - by ronaldwidha
    The title probably says it all. Considering an ipad's processor is nothing compared to a macbook, I would think a Macbook should be more than capable to run the simulator. However, not knowing much about iphone/ipad development, I'd like to get some opinions on this. for e.g. how many apps are typically need to be run for ipad dev (editor, debugger, perf monitor, trace log, etc). are these apps resource (memory, cpu) intensive? please do not take into consideration the actual image, 3d, video, sound development. I understand one would need quite a beefy machine to produce these type of creative assets. What I'm looking at is a machine to do code development, physics, putting together the produced assets (images, vector graphics, 3d video, sound, etc).

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  • Need to devise a number crunching algorithm

    - by Ravi Gupta
    I stumbled upon this question: 7 power 7 is 823543. Which higher power of 7 ends with 823543 ? How should I go about it ? The one I came up with is very slow, it keeps on multiplying by 7 and checks last 6 digits of the result for a match. I tried with Lou's code: int x=1; for (int i=3;i<=100000000;i=i+4){ x=(x*7)%1000000; System.out.println("i="+ i+" x= "+x); if (x==823543){ System.out.println("Ans "+i);} } And CPU sounds like a pressure cooker but couldn't get the answer :(

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  • nested page-faulting of user-space address in Linux

    - by shankar
    Hi, I would like to know if it is functionally wrong to page-fault a user-space address when kernel is running fault-handler to bring in a user-page. OS is Linux 2.6.30 Assume that both user-addresses are valid ( falling within vma , rw permission ) for the task. When I check the kernel code, i find that the kernel does not mind the nested fault if the faulted-addresses are valid and the fault did not occur in atomic-context or in irq handler. (I dont think the answer is cpu-specific, but I would add that i am interested in arm and mips ). eg : The scenario can happen if I print stack-data from page-fault handler. thanks shankar

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  • cmake: Target-specific preprocessor definitions for CUDA targets seems not to work

    - by Nils
    I'm using cmake 2.8.1 on Mac OSX 10.6 with CUDA 3.0. So I added a CUDA target which needs BLOCK_SIZE set to some number in order to compile. cuda_add_executable(SimpleTestsCUDA SimpleTests.cu BlockMatrix.cpp Matrix.cpp ) set_target_properties(SimpleTestsCUDA PROPERTIES COMPILE_FLAGS -DBLOCK_SIZE=3) When running make VERBOSE=1 I noticed that nvcc is invoked w/o -DBLOCK_SIZE=3, which results in an error, because BLOCK_SIZE is used in the code, but defined nowhere. Now I used the same definition for a CPU target (using add_executable(...)) and there it worked. So now the questions: How do I figure out what cmake does with the set_target_properties line if it points to a CUDA target? Googling around didn't help so far and a workaround would be cool..

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  • Good .NET library for fast streaming / batching trigonometry (Atan)?

    - by Sean
    I need to call Atan on millions of values per second. Is there a good library to perform this operation in batch very fast. For example, a library that streams the low level logic using something like SSE? I know that there is support for this in OpenCL, but I would prefer to do this operation on the CPU. The target machine might not support OpenCL. I also looked into using OpenCV, but it's accuracy for Atan angles is only ~0.3 degrees. I need accurate results.

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  • App Engine HTTP 500s

    - by pocoa
    This request caused a new process to be started for your application, and thus caused your application code to be loaded for the first time. This request may thus take longer and use more CPU than a typical request for your application. I've handled all the situations, also DeadlineExceededError too. But sometimes I see these error messages in error logs. That request took about 10k ms, so it's not exceeded the limit too. But there is no other specific message about this error. All I know is that it returned HTTP 500. Is there anyone know the reason of these error messages? Thank you.

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