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  • writing a fast parser in python

    - by panzi
    I've written a hands-on recursive pure python parser for a some file format (ARFF) we use in one lecture. Now running my exercise submission is awfully slow. Turns out by far the most time is spent in my parser. It's consuming a lot of CPU time, the HD is not the bottleneck. I wonder what performant ways are there to write a parser in python? I'd rather not rewrite it in C. I tried to use jython, but that decreased performance a lot! The files I parse are partially huge ( 150 MB) with very long lines. My current parser only needs a look-ahead of one character. I'd post the source here but I don't know if that's such a good idea. After all the submission deadline has not jet ended. But then, the focus in this exercise is not the parser. You can choose whatever language you want to use and there already is a parser for Java.

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  • operating systems - TLBs

    - by stabGreeol
    I'm trying to get my head round this (okay, tbh cramming a night before the exams :) but i can't figure out (nor find a good high level overview on the net) of this: 'page table entries can be mapped to more than one TLB entry.. if for example every page table entry is mappped to two TLB entries, this is know as 2-way set associative TLB' My question is, why would we want to map this more than once? surely we want to have the maximum number of possible entries represented in the TLB, and duplication would waste space right ? What am i missing? Many thanks

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  • C#, WinForms: Which view type for periodically updated list?

    - by rdoubleui
    I'm having an application, that periodically polls a web service (about every 10 seconds). In my application logic I'm having a List<Message> holding the messages. All messages have an id, and might be received out of order. Therefore the class implements the Comparable Interface. What WinForm control would fit to be regurarly updated (with the items in order). I plan to hold the last 500 messages. Should I sort the list and then update the whole form? Or is data binding approriate (concerning performance)?

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  • Preserve time stamp when shrinking an image

    - by Ckhrysze
    My digital camera takes pictures with a very high resolution, and I have a PIL script to shrink them to 800x600 (or 600x800). However, it would be nice for the resultant file to retain the original timestamp. I noticed in the docs that I can use a File object instead of a name in PIL's image save method, but I don't know if that will help or not. My code is basically name, ext = os.path.splitext(filename) # open an image file (.bmp,.jpg,.png,.gif) you have in the working folder image = Image.open(filename) width = 800 height = 600 w, h = image.size if h > w: width = 600 height = 800 name = name + ".jpg" shunken = image.resize((width, height), Image.ANTIALIAS) shunken.save(name) Thank you for any help you can give!

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  • Flexible argument list in LibreOffice Calc Macro

    - by Patru
    I want to write a function that geometrically links performance data which is usually provided as percentages, so the function will basically return (1+a)*(1+b)*(1+c)* … *(1+x)-1 This should be done using LibreOffice-calc and it should behave similarly to the regular sum function. As you may throw any number of arguments at sum I would like to be able to do the same with my alternative geoSum function but I am unable to find suitable documentation on handling a variable number of arguments with variable types (i.e. an arbitrary mix of numbers, cells and ranges). How would I have to specify the arguments to my LibreOffice-Basic function and how would I have to interpret it?

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  • Django on Dreamhost - testing/sand box environment

    - by elequ
    I've been using webfaction for all my django needs for the last couple of years but have had a high traffic site fall in my lap that dreamhost are probably better suited to handling. To set up and experiment with a site with webfaction there are your [user].webfactional.com accounts. Which is sweet. Equivalently Dreamhost also offers [name].dreamhosters.com Yet this doesn't seem to work with my database and this doesn't seem to be playing nice with setting up django or passenger_wsgi. So I'm wondering if I'm interpreting the documentation correctly to suggest that in order to make a site that depends on passenger it needs to be running from an active domain. The documentation is really implicit, I'm baffled. Has anyone set up a testing/sand box environment for django using dreamhost, or know how to?

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  • arbitrary typed data in django model

    - by Dmitry Shevchenko
    I have a model, say, Item. I want to store arbitrary amount of attributes on it, like title, description, release_date. And i want them to be not just strings but have python type, so string, boolean, datetime etc. What are my options here? EAV pattern with separate name-value table won't work because of the same DB type across all values. JSONField can probably help, but it doesn't know about datetime, for example. Also i was looking at PickeField, it fits perfectly, but i'm a bit concerned about performance.

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  • Struct in C, are they efficient?

    - by pygabriel
    I'm reading some C code like that: double function( int lena,double xa,double ya, double za, double *acoefs, ..., int lenb,double xb,double yb, double zb, double *bcoefs, ..., same for c, same for d ) This function is called in the code mor than 100.000 times so it's performance-critical. I'm trying to extend this code but I want to know if it's efficient or not (and how much this influences the speed) to encapsulate all the parameters in a struct like this struct PGTO { int len; double x,y,z ; double *acoefs } and then access the parameters in the function.

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  • Can I get the stack traces of all threads in my c# app?

    - by Drew Shafer
    I'm debugging an apparent concurrency issue in a largish app that I hack on at work. The bug in question only manifests on certain lower-performance machines after running for many (12+) hours, and I have never reproduced it in the debugger. Because of this, my debugging tools are basically limited to analyzing log files. C# makes it easy to get the stack trace of the thread throwing the exception, but I'd like to additionally get the stack traces of every other thread currently executing in my AppDomain at the time the exception was thrown. Is this possible?

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  • Are IoC containers about configuration files?

    - by Jader Dias
    Recently I developed a performance tester console application, with no UI, with the help of a IoC containter (Castle-Windsor-Microkernel). This library enabled me to let the user choose which test(s) to run, simply by changing the configuration file. Have I realized what IoC containers are about? I'm not sure. Even Joel said here on SO that IoC are difficult to understand. From my example, what do you conclude? Am I using IoC container for exactly what they were designed for? Or I am just using one of its secondary features?

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  • Are C++ meta-templates required knowledge for programmers?

    - by Robert Gould
    In my experience Meta-templates are really fun (when your compilers are compliant), and can give good performance boosts, and luckily I'm surrounded by seasoned C++ programmers that also grok meta-templates, however occasionally a new developer arrives and can't make heads or tails of some of the meta-template tricks we use (mostly Andrei Alenxandrescu stuff), for a few weeks until he gets initiated appropriately. So I was wondering what's the situation for other C++ programmers out there? Should meta-template programming be something C++ programmers should be "required" to know (excluding entry level students of course), or not? Edit: Note my question is related to production code and not little samples or prototypes

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  • Experimenting with data to determine value - migration/methods?

    - by TCK
    Hey guys, I have a LOT of data available to me, and want to experiment with data that isn't currently being used in production. The obvious solution seems to be to make a copy of production data and integrate it with what I want to play around with, but I was wondering if there was a better (less expensive?) way to do this. Both isolation and integration are important. I'd like to be able to keep lightweight/experimental data assets apart from high volume production data, but also be able to integrate (RELATIVELY) painlessly if experimental assets are deemed useful. Thanks.

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  • New to AVL tree implementation.

    - by nn
    I am writing a sliding window compression algorithm (LZ77) that searches for phrases in a "moving" dictionary. So far I have written a BST where each node is stored in an array and it's index in the array is also the value of the starting position in the window itself. I am now looking at transforming the BST to an AVL tree. I am a little confused at the sample implementations I have seen. Some only appear to store the balance factors whereas others store the height of each tree. Are there any performance advantage/disadvantages of storing the height and/or balance factor for each node? Apologies if this is a very simple question, but I'm still not visualizing how I want to restructure my BST to implement height balancing. Thanks.

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  • Linux - Create ftp account with read/write access to only 1 folder

    - by Gublooo
    Hey guys.... I have never worked on linux and dont plan on working on it either - The only command I probably know is "ls" :) I am hosting my website on Eapps and use their cpanel to setup everything so never worked with linux. Now I have this one time case - where I need to provide access to a contractor to fix the CSS issues on my website. He basically needs FTP (read/write) access to certain folders. At a high level - this is my code structure /home/webadmin/example.com/html/images /css /js /login.php /facebook.php /home/webadmin/example.com/application/library /views /models /controllers /config /bootstrap.php /home/webadmin/example.com/cgi-bin I want the new user to be able to have access to only these folders /home/webadmin/example.com/html/js /home/webadmin/example.com/html/css /home/webadmin/example.com/application/views He should not be able to view even the content of other folders including files like bootstrap.php or login.php etc If any sys admins can help me set this account up - will really appreciate it. Thanks

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  • Using different languages in one project

    - by Tarbal
    I recently heard about the use of several different languages in a (big) project, I also read about famous services such as Twitter using Rails as frontend, mixed with some other languages, and Scala I think it was as backend. Is this common practice? Who does that? I'm sure there are disadvantages to this. I think that you will have problems with the different interpreters/compilers and seamlessly connecting the different languages. Is this true? Why is this actually done? For performance?

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  • What is the maximum length in seconds to store a value in memcache

    - by Emilien
    The Google App Engine memcache documentation states that the time parameter of memcache.set() is an "Optional expiration time, either relative number of seconds from current time (up to 1 month), or an absolute Unix epoch time." So I tried to set a value for 30 days, which according to Google is 2 592 000 seconds. However, I highly suspect that this value is too high, because the value was set (memcache.set() returned the value True), but a memcache.get() just after always returned None. Reducing this value to 1 728 000 seconds just worked fine/as expected. I guess that once passed the highest value, the time parameter gets interpreted as an absolute Unix epoch time. That would mean that 2 592 000 seconds got interpreted as "Sat, 31 Jan 1970 00:00:00 GMT", which is obviously a date in the past... So what is the highest value you can enter that will get interpreted as a number of seconds in the future?

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  • Precompile Lambda Expression Tree conversions as constants?

    - by Nathan
    It is fairly common to take an Expression tree, and convert it to some other form, such as a string representation (for example this question and this question, and I suspect Linq2Sql does something similar). In many cases, perhaps even most cases, the Expression tree conversion will always be the same, i.e. if I have a function public string GenerateSomeSql(Expression<Func<TResult, TProperty>> expression) then any call with the same argument will always return the same result for example: GenerateSomeSql(x => x.Age) //suppose this will always return "select Age from Person" GenerateSomeSql(x => x.Ssn) //suppose this will always return "select Ssn from Person" So, in essence, the function call with a particular argument is really just a constant, except time is wasted at runtime re-computing it continuously. Assuming, for the sake of argument, that the conversion was sufficiently complex to cause a noticeable performance hit, is there any way to pre-compile the function call into an actual constant?

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  • Where do DQL statements live in an application that is using Zend Framework and Doctrine

    - by Dewayne
    In an application that is using Zend Framework 1.10 and Doctrine 1.2, where should the DQL statements live if our application is built such that it has a Service Layer and a Gateway(aka Doctrine_Table) layer. It seems that our possibilities include: 1) Placing the DQL statements in the Service layer which seems to be a bit too high in our application hierarchy to store DQL. 2) Placing the DQL statements within each model's Table/Gateway which seems a bit redundant because we also need to expose the DQL statements that do things such as getAllUsers() through the Service layer. Which of these is a preferable design? We intend to make use of the Service layer as much as possible so that other projects might consume various parts of our application.

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  • Storyboard editor layout confusion

    - by drew
    I am having layout problems with the storyboard editor with a fairly simple screen. I have a UIViewController to which I have added a 320x440 UIScrollView at 0,0 followed by a 320x20 UIProgressBar at 0,440. It looks fine in Storyboard editor. I'm not entirely sure how the 20 pixel status bar at the top of the screen is accommodated given the CGRect frame coordinates that Storyboard calculates. On loading ( in -(void)viewDidLoad ), the UIScrollView frame seems to be set to 320x460 pixels at 0,0 but the UIProgressBar is still 320x20 at 0,440. When I add subviews to the UIScrollView, (UIImageViews in particular), they get stretched and get clipped on the screen because although the UIScrollView thinks it is 460 pixels high, it only has 440 pixels of screen to display in. Can anyone point me to a solution? Thanks

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  • ASP.Net Web Site Project vs. Web Application Project

    - by user144612
    I'm trying to convince my co-workers to switch from a web site project to a web application project, because I want the use of the project file. However I can't diffuse this argument against: The web site project allows each page to be compiled into a single dll. Their argument is this enables easy fixing of errors found after publishing. This is contrast to how the web application project compiles all code behind into a single dll. Is updating a single page's dll essentially different to updating the entire site's dll? Is there some way to compile each page's code behind into a seperate dll in the web application project? Are there some prohibitive (performance,memory?) costs to compiling each page's code behind into seperate dll's that we are unaware of? Why is the feature(?) to compile each page to separate dlls in web site projects and not web app projects?

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  • Internet Explorer visual element stacking issue

    - by Michael
    Gday All, I know this issue is well known, however I have searched high and low for a solution to no avail. I have created a menu system using nested ordered lists where the menu functionality is controlled by CSS and Jquery. The menu works perfectly in FF, Chrome, Opera and Epiphany. However in IE 6/7/8 my popup menu is being displayed underneath a table. See the image below. The very top box is a div element containing my menu system. I am working with legacy code that uses tables for display so the next box and the "ts found. Try a different subcate" text is in a "td" element of a table. I have tried to force the table to have a lower z-index but this does not work. Any insights into why this is only present in IE would be appreciated. Cheers, Michael

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  • Looking for a .NET 3.5 / J2EE architecture concept comparison article/chart

    - by Edward Tanguay
    We are thinking about combining .NET technology with Java technology (WCF, JBoss/ESB, MOM, WPF, WF) and I need to have a high-level idea of what are the apples and oranges in the .NET 3.5 and Java worlds. Does anyone know of a good, clear article or better yet a simple chart which answers questions such as: WCF in the Java world is __ the equivalent of WPF in the Java world is _ the closes thing to JBoss in the .NET world is _ the JVM and CLR are essentially the same except for these differences: .... in the Java world you don't have the concept of WF/WCF/WPF, instead you have .... there is no "LINQ" in the Java world yet, but you can use ___ the closest you get to ADO.NET Data Services in the Java world is .... I'm not looking to debate this so I'm not looking for "fighting points", I just need a neutral what-is-what chart comparing the two worlds.

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  • improving conversions to binary and back in C#

    - by Saad Imran.
    I'm trying to write a general purpose socket server for a game I'm working on. I know I could very well use already built servers like SmartFox and Photon, but I wan't to go through the pain of creating one myself for learning purposes. I've come up with a BSON inspired protocol to convert the the basic data types, their arrays, and a special GSObject to binary and arrange them in a way so that it can be put back together into object form on the client end. At the core, the conversion methods utilize the .Net BitConverter class to convert the basic data types to binary. Anyways, the problem is performance, if I loop 50,000 times and convert my GSObject to binary each time it takes about 5500ms (the resulting byte[] is just 192 bytes per conversion). I think think this would be way too slow for an MMO that sends 5-10 position updates per second with a 1000 concurrent users. Yes, I know it's unlikely that a game will have a 1000 users on at the same time, but like I said earlier this is supposed to be a learning process for me, I want to go out of my way and build something that scales well and can handle at least a few thousand users. So yea, if anyone's aware of other conversion techniques or sees where I'm loosing performance I would appreciate the help. GSBitConverter.cs This is the main conversion class, it adds extension methods to main datatypes to convert to the binary format. It uses the BitConverter class to convert the base types. I've shown only the code to convert integer and integer arrays, but the rest of the method are pretty much replicas of those two, they just overload the type. public static class GSBitConverter { public static byte[] ToGSBinary(this short value) { return BitConverter.GetBytes(value); } public static byte[] ToGSBinary(this IEnumerable<short> value) { List<byte> bytes = new List<byte>(); short length = (short)value.Count(); bytes.AddRange(length.ToGSBinary()); for (int i = 0; i < length; i++) bytes.AddRange(value.ElementAt(i).ToGSBinary()); return bytes.ToArray(); } public static byte[] ToGSBinary(this bool value); public static byte[] ToGSBinary(this IEnumerable<bool> value); public static byte[] ToGSBinary(this IEnumerable<byte> value); public static byte[] ToGSBinary(this int value); public static byte[] ToGSBinary(this IEnumerable<int> value); public static byte[] ToGSBinary(this long value); public static byte[] ToGSBinary(this IEnumerable<long> value); public static byte[] ToGSBinary(this float value); public static byte[] ToGSBinary(this IEnumerable<float> value); public static byte[] ToGSBinary(this double value); public static byte[] ToGSBinary(this IEnumerable<double> value); public static byte[] ToGSBinary(this string value); public static byte[] ToGSBinary(this IEnumerable<string> value); public static string GetHexDump(this IEnumerable<byte> value); } Program.cs Here's the the object that I'm converting to binary in a loop. class Program { static void Main(string[] args) { GSObject obj = new GSObject(); obj.AttachShort("smallInt", 15); obj.AttachInt("medInt", 120700); obj.AttachLong("bigInt", 10900800700); obj.AttachDouble("doubleVal", Math.PI); obj.AttachStringArray("muppetNames", new string[] { "Kermit", "Fozzy", "Piggy", "Animal", "Gonzo" }); GSObject apple = new GSObject(); apple.AttachString("name", "Apple"); apple.AttachString("color", "red"); apple.AttachBool("inStock", true); apple.AttachFloat("price", (float)1.5); GSObject lemon = new GSObject(); apple.AttachString("name", "Lemon"); apple.AttachString("color", "yellow"); apple.AttachBool("inStock", false); apple.AttachFloat("price", (float)0.8); GSObject apricoat = new GSObject(); apple.AttachString("name", "Apricoat"); apple.AttachString("color", "orange"); apple.AttachBool("inStock", true); apple.AttachFloat("price", (float)1.9); GSObject kiwi = new GSObject(); apple.AttachString("name", "Kiwi"); apple.AttachString("color", "green"); apple.AttachBool("inStock", true); apple.AttachFloat("price", (float)2.3); GSArray fruits = new GSArray(); fruits.AddGSObject(apple); fruits.AddGSObject(lemon); fruits.AddGSObject(apricoat); fruits.AddGSObject(kiwi); obj.AttachGSArray("fruits", fruits); Stopwatch w1 = Stopwatch.StartNew(); for (int i = 0; i < 50000; i++) { byte[] b = obj.ToGSBinary(); } w1.Stop(); Console.WriteLine(BitConverter.IsLittleEndian ? "Little Endian" : "Big Endian"); Console.WriteLine(w1.ElapsedMilliseconds + "ms"); } Here's the code for some of my other classes that are used in the code above. Most of it is repetitive. GSObject GSArray GSWrappedObject

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  • Tokenizer for full-text

    - by user72185
    This should be an ideal case of not re-inventing the wheel, but so far my search has been in vain. Instead of writing one myself, I would like to use an existing C++ tokenizer. The tokens are to be used in an index for full text searching. Performance is very important, I will parse many gigabytes of text. Edit: Please note that the tokens are to be used in a search index. Creating such tokens is not an exact science (afaik) and requires some heuristics. This has been done a thousand time before, and probably in a thousand different ways, but I can't even find one of them :) Any good pointers? Thanks!

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  • How can I reuse my javascript code between client and server?

    - by Chris Farmer
    I have some javascript code that includes an ANTLR-generated lexer and parser, and some associated syntax tree evaluation functionality. This code runs in the browser in my web app to support users who author code snippets which process scientific data. Now I'd like to do some additional background processing on the server using the same generated parser. I would prefer not to have to re-implement this stuff in C# and have multiple bits of code that did the exact same thing. Performance isn't as critical to me as eliminating duplication, since this is a background process. So, how can I call into my javascript code from C#? And how can I format my script so that it plays nicely with my .NET web app?

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