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  • Redundancy algorithm for reading noisy bitstream

    - by Tedd Hansen
    I'm reading a lossy bit stream and I need a way to recover as much usable data as possible. There can be 1's in place of 0's and 0's in palce of 1's, but accuracy is probably over 80%. A bonus would be if the algorithm could compensate for missing/too many bits as well. The source I'm reading from is analogue with noise (microphone via FFT), and the read timing could vary depending on computer speed. I remember reading about algorithms used in CD-ROM's doing this in 3? layers, so I'm guessing using several layers is a good option. I don't remember the details though, so if anyone can share some ideas that would be great! :) Edit: Added sample data Best case data: in: 0000010101000010110100101101100111000000100100101101100111000000100100001100000010000101110101001101100111000101110000001001111011001100110000001001100111011110110101011100111011000100110000001000010111 out: 0010101000010110100101101100111000000100100101101100111000000100100001100000010000101110101001101100111000101110000001001111011001100110000001001100111011110110101011100111011000100110000001000010111011 Bade case (timing is off, samples are missing): out: 00101010000101101001011011001110000001001001011011001110000001001000011000000100001011101010011011001 in: 00111101001011111110010010111111011110000010010000111000011101001101111110000110111011110111111111101 Edit2: I am able to controll the data being sent. Currently attempting to implement simple XOR checking (though it won't be enough).

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  • pyplot: really slow creating heatmaps

    - by cvondrick
    I have a loop that executes the body about 200 times. In each loop iteration, it does a sophisticated calculation, and then as debugging, I wish to produce a heatmap of a NxM matrix. But, generating this heatmap is unbearably slow and significantly slow downs an already slow algorithm. My code is along the lines: import numpy import matplotlib.pyplot as plt for i in range(200): matrix = complex_calculation() plt.set_cmap("gray") plt.imshow(matrix) plt.savefig("frame{0}.png".format(i)) The matrix, from numpy, is not huge --- 300 x 600 of doubles. Even if I do not save the figure and instead update an on-screen plot, it's even slower. Surely I must be abusing pyplot. (Matlab can do this, no problem.) How do I speed this up?

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  • SQL Server - Storing multiple decimal values in a column?

    - by cshah
    I know storing multiple values in a column. Not a good idea. It violates first normal form --- which states NO multi valued attributes. Normalize period... I am using SQL Server 2005 I have a table that require to store lower limit and uppper limit for a measurement, think of it as a minimum and maximum speed limit... only problem is only 2 % out of hundread i need upper limit. I will only have data for lower limit. I was thinking to store both values in a column (Sparse column introduces in 2008 so not for me) Is there a way...? Not sure about XML..

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  • How to optimize MATLAB loops?

    - by striglia
    I have been working lately on a number of iterative algorithms in MATLAB, and been getting hit hard by MATLAB's performance (or lack thereof) when it comes to loops. I'm aware of the benefit of vectorizing code when possible, but are there any tools for optimization when you need the loop for your algorithm? I am aware of the MEX-file option to write small subroutines in C/C++, although given my algorithms, this can be a very painful option given the data structures required. I mainly use MATLAB for the simplicity and speed of prototyping, so a syntactically complex, statically typed language is not ideal for my situation. Are there any other suggestions? Even other languages (python?) which have relatively painless matrix tools are an option.

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  • Eclipse Basic Web Development?

    - by Sean Ochoa
    I want to start doing web development with Eclipse. Not Java, tomcat, axis2, or anything else anymore complicated than basic XHTML / JS / CSS development, at this time. Problem 1: I realize that it can edit those files, but its trying to manage my HTML docs as part of "my workspace", and all I want it to do is manage the files as part of my local www server HTdocs directory. Problem 2: I would like to edit WYSIWYG-style, if possible. I tried installing a plug-in for that, but I wasn't able to get w4 toolkit to function properly. This would really help me to speed up development, I think. Follow-up: I've installed WTP and its dependencies (except for the tests portion, which had install problems due to dependencies that were seemingly irreconcilable).

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  • What was the most surprising failure of your 'Engineer's intuition'?

    - by Bubba88
    Hi! This may seem as an open-ended question but I'll surely accept the most impressive and upvoted answer ;) Basically, I could describe my own case - I just fail 5 times a day with my intuition cause very frequently I can be just not up-to-the-speed with my requirements/manager/team/etc. and I just have to make code quickly - that's why proper formalization in many cases stands aside. I want to gather some experience of yours - what was the most epic failure when you did rely on you implicit reasoning/intuitive knowledge/immediate perception etc. of course everything you describe should be related to programming/computers. It's mostly just to measure the danger of using that 'it's obvious..' words. I've made it com. wiki to be properly transformed after gathering enough views count. Thank you!

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  • Using multithreading for loop

    - by annelie
    Hello, I'm new to threading and want to do something similar to this question: http://stackoverflow.com/questions/100291/speed-up-loop-using-multithreading-in-c-question However, I'm not sure if that solution is the best one for me as I want them to keep running and never finish. (I'm also using .net 3.5 rather than 2.0 as for that question.) I want to do something like this: foreach (Agent agent in AgentList) { // I want to start a new thread for each of these agent.DoProcessLoop(); } --- public void DoProcessLoop() { while (true) { // do the processing // this is things like check folder for new files, update database // if new files found } } Would a ThreadPool be the best solution or is there something that suits this better? Thanks, Annelie

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  • Get highest frequency terms from Lucene index

    - by Julia
    Hello! i need to extract terms with highest frequencies from several lucene indexes, to use them for some semantic analysis. So, I want to get maybe top 30 most occuring terms(still did not decide on threshold, i will analyze results) and their per-index counts. I am aware that I might lose some precision because of potentionally dropped duplicates, but for now, lets say i am ok with that. So for the proposed solutions, (needless to say maybe) speed is not important, since I would do static analysis, I would put accent on simplicity of implementation because im not so skilled with Lucene (not the programming guru too :/ ) and cant wrap my mind around many concepts of it.. I can not find any code samples from something similar, so all concrete advices (code, pseudocode, links to code samples...) I will apretiate very much!!! Thank you!

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  • MongoDB Schema Design - Real-time Chat

    - by Nick
    I'm starting a project which I think will be particularly suited to MongoDB due to the speed and scalability it affords. The module I'm currently interested in is to do with real-time chat. If I was to do this in a traditional RDBMS I'd split it out into: Channel (A channel has many users) User (A user has one channel but many messages) Message (A message has a user) The the purpose of this use case, I'd like to assume that there will be typically 5 channels active at one time, each handling at most 5 messages per second. Specific queries that need to be fast: Fetch new messages (based on an bookmark, time stamp maybe, or an incrementing counter?) Post a message to a channel Verify that a user can post in a channel Bearing in mind that the document limit with MongoDB is 4mb, how would you go about designing the schema? What would yours look like? Are there any gotchas I should watch out for?

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  • Where should I put WPF specific code when using MVVM?

    - by Surfbutler
    I'm just getting up to speed on MVVM, but all the examples I've seen so far are binding View controls to simple non-WPF specific data types such as strings and ints. However in our app I want to be able to set a button's border brush based on a number in the Model. At the moment, I translate the number into a brush in the ViewModel to keep the View XAML only, but is that right? I don't like putting WPF specific code in the ViewModel, but equally I don't like the idea of putting code-behind on my View panel. Which is the best way? Thanks

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  • Very slow Eclipse 4.2, how to make it more responsive?

    - by Laurent
    I'm using Eclipse PDT on a rather large PHP project and the IDE is almost unusable. It takes nearly 30 seconds to open a file, and other actions, like selecting a folder in the file explorer, editing some text, etc. are equally slow. I followed various instructions to speed it up but nothing seems to work. This is my current eclipse.ini file. Any idea how I can improve it? -startup plugins/org.eclipse.equinox.launcher_1.3.0.v20120522-1813.jar --launcher.library plugins/org.eclipse.equinox.launcher.win32.win32.x86_1.1.200.v20120522-1813 -showsplash org.eclipse.platform --launcher.XXMaxPermSize 256m --launcher.defaultAction openFile -vmargs -server -Dosgi.requiredJavaVersion=1.7 -Xmn128m -Xms1024m -Xmx1024m -Xss2m -XX:PermSize=128m -XX:MaxPermSize=128m -XX:+UseParallelGC System: Eclipse 4.2.0, Windows 7, 4 GB RAM

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  • Using memtables in sql. When is it reasonable and is it safe?

    - by Spiros
    I was just reading an update from a friend's project, mentioning the use of memtables to store data temporatily and then flush to a table on disk. Up to now, I have never faced a situation where I would use a memtable, or a situation where I would think the use of a mem table would be beneficial; so I wonder, when would someone use mem tables? what makes a memtable (appart from access speed) a reasonable choice? and how safe is it, even for temp data? there is always the limitation of available physical memory.

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  • how to profile my code??

    - by kaki
    i want to how to profile my code... i have gone through the docs , but as there were no example codes given i could not get anything from it. i have a large code and it is taking so much time hence want to profile and increase its speed. i havent written my code in method , there are few in between but not completely. i dont have any main in my code..i want to know how to use profiling.. looking for some example or sample code of about how to profile.. i tried psyco i.e just addded two line at the top of my code import psyco psyco.full() is this write,it did not show any improvement. and other way of speeding up ,please suggest. thanks in advance..

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  • Subversion for version control

    - by Gabriel Parenza
    Hi, I am working on an application whose primary purpose would be to provide source control management. My idea is to use to SVNKit for file check-out and check-in. However, while working with SVNKit, I realised it does not have the speed I was looking for. For instance, whenever developers create a ChangeRequest, which can encompass change in 3-40 files, I have to create a directory structure distributed across 32 folders. Doing so takes around 50 seconds, Another instance is that after creating change request developers can add files to the request. Copying even a single file from Trunk to branch takes around 6-7 secs. My question is has anyone had experience like this and what did you do to improve the performance? Moreover, is my approach correct? NOTE: I am using "http" protocol and can't use "svn" protocol.

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  • T-SQL: Dynamic Where clause in normal SQL statement

    - by Torben H.
    Hey there, I looking for a way to dynamicly add a filter to my statment without using dynamic SQL. I want to select all computers from a table, but when I pass a computer id to the sp, I want to get only this computer. Actually I try this on DECLARE @ComputerFilter AS INT DECLARE @ComputerID AS INT SELECT Computername FROM Computer WHERE (ComputerID = @ComputerID) OR (@ComputerFilter IS NULL)) But this is 100 times slow then this statment and tooks as long as SELECT * FROM Computer SELECT Computername FROM Computer WHERE ComputerID = @ComputerID Is there a way to speed this statment up or is there any other way to solve this problem with one select und without dynamic sql?

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  • How to determine cpu, ram needed for rails app?

    - by Ben
    What is the most accurate way to determine the amount of cpu speed and ram needed to run my rails app? I believe there are stress testing tools like Tsung, but how do I determine, for example, that I need X more ram, or X more CPU? I would like to find some way to roughly gauge the performance needs of my application so I can anticipate future needs. I think this data will also be useful for me to decide whether to upgrade one machine, or get another dedicated machine and put all the databases on that one. Essentially, I am concerned about scaling issues, and how to anticipate them. Thanks in advance for the help!

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  • In-memory Database in Excel

    - by user329174
    Hello, I am looking for a way to import a datatable from Access into an Excel variable and then run queries through this variable to speed up the process. I am trying to migrate from C# .NET where I read a data table from an access database into memory and then used LINQ to query this dataset. It is MUCH faster than how I have it currently coded in VBA where I must make lots of calls to the actual database, which is slow. I have seen the QueryTable mentioned, but it appears that this requires pasting the data into the excel sheet. I would like to keep everything in memory and minimize the interaction between the Excel Sheet and the VBA code as much as possible. I wish we didn't need to use Excel+VBA to do this, but we're kind of stuck with that for now. Thanks for the help!

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  • Conversion Fahrenheit to celsius programmatically

    - by Doom
    In my project, want to show the weather in fahrenheit first, then if the user wants clickes on conversion, needs to show the weather in celsius. My code is NSNumber *metric = [[NSUserDefaults standardUserDefaults] objectForKey:@"metric"]; NSLog(@"Metric is %@", metric); CGFloat aFloat = [speed floatValue]; CGFloat tFloat = [temperature floatValue]; CGFloat tempFloat = (tFloat-30)/2; NSNumber * p_Number = [NSNumber numberWithFloat:tempFloat]; //Convert mph to kmph if ([metric boolValue]) { [windValueLabel setText:[NSString stringWithFormat:@"%.2f kmph", aFloat * 1.6] ]; temperatureLabel.text = [NSString stringWithFormat:@"%@", p_Number]; } else{ [windValueLabel setText:[NSString stringWithFormat:@"%.2f mph", aFloat / 1.6]]; temperatureLabel.text = [NSString stringWithFormat:@"%@", temperature]; } When u start the app, its working and showing temperature in fahrenheit, but crashes at celsius man... is that the current conversion. help me out guys

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  • Reset form with jQuery

    - by da5id
    I have a form with a standard reset button coded thusly: <input type="reset" class="button standard" value="Clear" /> Trouble is, said form is of the multi-stage sort, so if a user fills out a stage & then returns later, the 'remembered' values for the various fields won't reset when the Clear button is clicked. I'm thinking that attaching a jQuery function to loop over all the fields and clear them 'manually' would do the trick. I'm already using jQuery within the form, but am only just getting up to speed & so am not sure how to go about this, other than individually referencing each field by ID, which doesn't seem very efficient. TIA for any help.

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  • Must .aspx files have a page directive?

    - by Keith Bloom
    Around 90% of the pages for our websites have no .Net code embedded in them yet are published as .aspx files. I want these to render as fast as possible so I'm removing as much as I can. Does the .Net page directive have an impact on performance? I am thinking about two factors; the page speed for each GET and what happens when the file changes. The CMS system re-creates each page daily and I'm wondering if this triggers the ASP.Net compilation process.

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  • How to do call function after client finishes download from tornado web server?

    - by Shabbyrobe
    I would like to be able to run some cleanup functions if and only if the client successfully completes the download of a file I'm serving using Tornado. I installed the firefox throttle tool and had it slow the connection down to dialup speed and installed this handler to generate a bunch of rubbish random text: class CrapHandler(BaseHandler): def get(self, token): crap = ''.join(random.choice(string.ascii_uppercase + string.digits) for x in range(100000)) self.write(crap) print "done" I get the following output from tornado immediately after making the request: done I 100524 19:45:45 web:772] 200 GET /123 (192.168.45.108) 195.10ms The client then plods along downloading for about 20 seconds. I expected that it would print "done" after the client was done. Also, if I do the following I get pretty much the same result: class CrapHandler(BaseHandler): @tornado.web.asynchronous def get(self, token): crap = ''.join(random.choice(string.ascii_uppercase + string.digits) for x in range(100000)) self.write(crap) self.finish() print "done" Am I missing something fundamental here? Can tornado even support what I'm trying to do? If not, is there an alternative that does?

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  • Fast way to set text format for a range of Text using TLF

    - by wezzy
    Hi, i have to set the text format for some tokens in a plain text. I'm trying to use the Text Layout Framework to improve the speed of the operation but i've founded that TLF is far slower (10X in my tests) than the old setTextFormat(). For each token i call this function: public function setTextFormat(format:TextLayoutFormat, begin:int, end:int):void{ var selection:SelectionState = new SelectionState(this._textFlow, begin, end, this._normalFormat); IEditManager(_textFlow.interactionManager).applyLeafFormat(format, selection); } is there any faster and clever way to do this operation ? Thanks

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  • ado.net slow updating large tables

    - by brett
    The problem: 100,000+ name & address records in an access table (2003). Need to iterate through the table & update detail with the output from a 3rd party dll. I currently use ado, and it works at an acceptable speed (less than 5 minutes on a network share). We will soon need to update to access 2007 and its 'non jet' accdb format to maintain compatability with clients. I've tried using ado.net datsets, but updating the records takes hours! We process 5-10 of these tables per day - so this cannot be a solution. Any ideas on the fastest way to update individual records using ado.net? Surely we didn't take such a hugh backward step with ado.net? Any help would be appreciated.

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  • Can managed and unmanaged C++/MFC be mixed in one dll?

    - by Walter Williams
    Previously we had software in MFC (VC6), VB6 and C# applications that needed to call the same engine written in C++ (and MFC). The engine required C++ for speed. At the time we decided to use COM as the interface because all three could use it with the least issues in marshalling, etc. Our MFC application is now deprecated and we have recently decided to dump VB6, so what we've got left is C#. We can just leave the COM engine as-is, but it would be nice to get away from COM registration, etc., and have a managed interface to work with. COM registration occasionally causes support issues if there is something wrong with the person's machine. Is it possible to have a dll with the existing unmanaged C++/MFC, and a .NET front end interface?

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  • iPhone: Turning latitude/longitude into "major cross-streets"

    - by Gloria
    Using the MKReverseGeocoder or GoogleAPI or MapKit... Is there a simple way to turn a latitude/longitude into "nearest major cross-streets"? A user might not have any idea where "12345 Pineapple" is located... so I want to show something like "Pineapple and Main"... or (larger, major roads) like "US-140 and Hwy 76". I don't really care what "major" is defined as... perhaps any road with higher speed limits... or more than 3 lanes... etc. I don't really care what "close by" is defines as... perhaps within 0-10 miles... or just "closest found".

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