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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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  • send form data as web service in symfony

    - by Lars
    I am making a restrictive portal to a WiFi network using symfony, and I want to send a form as web service to other sites that want to use this portal. How should I solve this? I realize I could go the SOAP/WSDL route, but since symfony is already RESTful, it seems to me I could go the RESTful route with considerably less pain and loss of performance. Right now, I have a working form, but I've only made a casual attempt to bring the form to a remote site by using cURL. The form does not work remotely since the routing is not set up correctly (I think). Can someone help me with this? Thanks.

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  • How to Serialize Binary Tree

    - by Veljko Skarich
    I went to an interview today where I was asked to serialize a binary tree. I implemented an array-based approach where the children of node i (numbering in level-order traversal) were at the 2*i index for the left child and 2*i + 1 for the right child. The interviewer seemed more or less pleased, but I'm wondering what serialize means exactly? Does it specifically pertain to flattening the tree for writing to disk, or would serializing a tree also include just turning the tree into a linked list, say. Also, how would we go about flattening the tree into a (doubly) linked list, and then reconstructing it? Can you recreate the exact structure of the tree from the linked list? Thank you/

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  • ZIPLIB problem on opening zip files

    - by Ahmet vardar
    I am using this class to create zip <?php // vim: expandtab sw=4 ts=4 sts=4: class zipfile { var $datasec = array(); var $ctrl_dir = array(); var $eof_ctrl_dir = "\x50\x4b\x05\x06\x00\x00\x00\x00"; var $old_offset = 0; function unix2DosTime($unixtime = 0) { $timearray = ($unixtime == 0) ? getdate() : getdate($unixtime); if ($timearray['year'] < 1980) { $timearray['year'] = 1980; $timearray['mon'] = 1; $timearray['mday'] = 1; $timearray['hours'] = 0; $timearray['minutes'] = 0; $timearray['seconds'] = 0; } // end if return (($timearray['year'] - 1980) << 25) | ($timearray['mon'] << 21) | ($timearray['mday'] << 16) | ($timearray['hours'] << 11) | ($timearray['minutes'] << 5) | ($timearray['seconds'] >> 1); } // end of the 'unix2DosTime()' method function addFile($data, $name, $time = 0) { $name = str_replace('\\', '/', $name); $dtime = dechex($this->unix2DosTime($time)); $hexdtime = '\x' . $dtime[6] . $dtime[7] . '\x' . $dtime[4] . $dtime[5] . '\x' . $dtime[2] . $dtime[3] . '\x' . $dtime[0] . $dtime[1]; eval('$hexdtime = "' . $hexdtime . '";'); $fr = "\x50\x4b\x03\x04"; $fr .= "\x14\x00"; // ver needed to extract $fr .= "\x00\x00"; // gen purpose bit flag $fr .= "\x08\x00"; // compression method $fr .= $hexdtime; // last mod time and date // "local file header" segment $unc_len = strlen($data); $crc = crc32($data); $zdata = gzcompress($data); $zdata = substr(substr($zdata, 0, strlen($zdata) - 4), 2); // fix crc bug $c_len = strlen($zdata); $fr .= pack('V', $crc); // crc32 $fr .= pack('V', $c_len); // compressed filesize $fr .= pack('V', $unc_len); // uncompressed filesize $fr .= pack('v', strlen($name)); // length of filename $fr .= pack('v', 0); // extra field length $fr .= $name; // "file data" segment $fr .= $zdata; // "data descriptor" segment (optional but necessary if archive is not // served as file) $fr .= pack('V', $crc); // crc32 $fr .= pack('V', $c_len); // compressed filesize $fr .= pack('V', $unc_len); // uncompressed filesize // add this entry to array $this -> datasec[] = $fr; // now add to central directory record $cdrec = "\x50\x4b\x01\x02"; $cdrec .= "\x00\x00"; // version made by $cdrec .= "\x14\x00"; // version needed to extract $cdrec .= "\x00\x00"; // gen purpose bit flag $cdrec .= "\x08\x00"; // compression method $cdrec .= $hexdtime; // last mod time & date $cdrec .= pack('V', $crc); // crc32 $cdrec .= pack('V', $c_len); // compressed filesize $cdrec .= pack('V', $unc_len); // uncompressed filesize $cdrec .= pack('v', strlen($name) ); // length of filename $cdrec .= pack('v', 0 ); // extra field length $cdrec .= pack('v', 0 ); // file comment length $cdrec .= pack('v', 0 ); // disk number start $cdrec .= pack('v', 0 ); // internal file attributes $cdrec .= pack('V', 32 ); // external file attributes - 'archive' bit set $cdrec .= pack('V', $this -> old_offset ); // relative offset of local header $this -> old_offset += strlen($fr); $cdrec .= $name; // optional extra field, file comment goes here // save to central directory $this -> ctrl_dir[] = $cdrec; } // end of the 'addFile()' method function file() { $data = implode('', $this -> datasec); $ctrldir = implode('', $this -> ctrl_dir); return $data . $ctrldir . $this -> eof_ctrl_dir . pack('v', sizeof($this -> ctrl_dir)) . // total # of entries "on this disk" pack('v', sizeof($this -> ctrl_dir)) . // total # of entries overall pack('V', strlen($ctrldir)) . // size of central dir pack('V', strlen($data)) . // offset to start of central dir "\x00\x00"; // .zip file comment length } // end of the 'file()' method function addFiles($files ) { foreach($files as $file) { if (is_file($file)) //directory check { $data = implode("",file($file)); $this->addFile($data,$file); } } } function output($file) { $fp=fopen($file,"w"); fwrite($fp,$this->file()); fclose($fp); } } // end of the 'zipfile' class ?> It creates zip file but when i try to open it on Mac os x snow leopard and windows 7, it doesnt open. on mac i had this error: Error 1: operation not permitted Any idea ? thanks

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  • C# Threading vs single thread

    - by user177883
    Is it always guaranteed that a multi-threaded application would run faster than a single threaded application? I have two threads that populates data from a data source but different entities (eg: database, from two different tables), seems like single threaded version of the application is running faster than the version with two threads. Why would the reason be? when i look at the performance monitor, both cpu s are very spikey ? is this due to context switching? what are the best practices to jack the CPU and fully utilize it? I hope this is not ambiguous.

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  • How to create a delayed queue in RabbitMQ?

    - by eandersson
    What is the easiest way to create a delay (or parking) queue with Python, Pika and RabbitMQ? I have seen an similar questions, but none for Python. I find this an useful idea when designing applications, as it allows us to throttle messages that needs to be re-queued again. There are always the possibility that you will receive more messages than you can handle, maybe the HTTP server is slow, or the database is under too much stress. I also found it very useful when something went wrong in scenarios where there is a zero tolerance to losing messages, and while re-queuing messages that could not be handled may solve that. It can also cause problems where the message will be queued over and over again. Potentially causing performance issues, and log spam.

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  • which is the best for build a Gantt-chart like application Flex or Flash Action Script?

    - by coderex
    Which is the best for build an application show like in image. For the better graphics and performance wise. I want to know Flash for Flex is more suitable for this. In Flash ca we be able to build a grid kind of applications easily? I headed that Flex have the functions to handle grid and other things. Drag & scroll Zoom like feature. but am not sure able the graphics of flex. Is the components are customizable.. Please help me.

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  • windows I/O manager - IRP's classification in read-like and write-like

    - by clyfe
    I am writing a windows filesystem minifilter driver that must fail IRP's in a preoperation callback. How can I find out from the callback parameters if the operation is read-like ( only reads data ) or it's write-like ( modifies data on the disk - write, delete etc ) ? I'm thinking on: Data->Iopb->TargetFileObject->ReadAccess Data->Iopb->TargetFileObject->WriteAccess But I'm not sure, I think thees are available only in postoperation callback. The documentation is really cumbersome. Code sample: FLT_PREOP_CALLBACK_STATUS Fail ( __inout PFLT_CALLBACK_DATA Data, __in PCFLT_RELATED_OBJECTS FltObjects, __deref_out_opt PVOID *CompletionContext ) { FLT_PREOP_CALLBACK_STATUS status = FLT_PREOP_SUCCESS_NO_CALLBACK; if ( IS WRITE_LIKE(Data, FltObjects) ) { // ??? HOW DO I FIND OUT???? if( FLT_IS_FASTIO_OPERATION(Data) ){ status = FLT_PREOP_DISALLOW_FASTIO; } else { status = FLT_PREOP_COMPLETE; } Data->IoStatus.Status = STATUS_ACCESS_DENIED; Data->IoStatus.Information = 0; return status; } return status; }

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  • Whats faster in Javascript a bunch of small setInterval loops, or one big one?

    - by RobertWHurst
    Just wondering if its worth it to make a monolithic loop function or just add loops were they're needed. The big loop option would just be a loop of callbacks that are added dynamically with an add function. adding a function would look like this setLoop(function(){ alert('hahaha! I\'m a really annoying loop that bugs you every tenth of a second'); }); setLoop would add the function to the monolithic loop. so is the is worth anything in performance or should I just stick to lots of little loops using setInterval?

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  • Parametrize the WHERE clause?

    - by ControlFlow
    Hi, stackoverflow! I'm need to write an stored procedure for SQL Server 2008 for performing some huge select query and I need filter it results with specifying filtering type via procedure's parameters (parameterize where clause). I found some solutions like this: create table Foo( id bigint, code char, name nvarchar(max)) go insert into Foo values (1,'a','aaa'), (2,'b','bbb'), (3,'c','ccc') go create procedure Bar @FilterType nvarchar(max), @FilterValue nvarchar(max) as begin select * from Foo as f where case @FilterType when 'by_id' then f.id when 'by_code' then f.code when 'by_name' then f.name end = case @FilterType when 'by_id' then cast(@FilterValue as bigint) when 'by_code' then cast(@FilterValue as char) when 'by_name' then @FilterValue end end go exec Bar 'by_id', '1'; exec Bar 'by_code', 'b'; exec Bar 'by_name', 'ccc'; But it doesn't work when the columns has different data types... It's possible to cast all the columns to nvarchar(max) and compare they as strings, but I think it will cause a performance degradation... Is it possible to parameterize where clause in stored procedure without using things like EXEC sp_executesql (dynamic SQL and etc.)?

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  • Whats the scope of a c function defined within objective-c class?

    - by roja
    I was reading up about bypassing objective-c's messaging to gain performance (irrelevant to this specific question) when i found an interesting bit of code: #import <Cocoa/Cocoa.h> @interface Fib : NSObject { } - (long long) cFib: (NSUInteger) number; @end @implementation Fib // c implementation of fib long long cFibIMP(NSUInteger number) { return (number < 3) ? 1 : cFib(number - 1) + cFib(number - 2); } // method wrapper for c implementation of fib - (long long) cFib: (NSUInteger) number { return cFibIMP(number); } @end My question is; when using c function, within an objective-c object, what scope is the c function (cFibIMP in this particular case) placed in? Does the objective-c class encapsulate the c function removing change of name-clash or is the c function simply dumped into the global scope of the whole objective-c program?

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  • Is it really wrong to version documents using CouchDB's default behaviour?

    - by Tomas Sedovic
    This is one of those "I know I shouldn't do this but it's oh so convenient." questions. Sorry about that. I plan to use CouchDB for storing a bunch of documents and keeping their entire revision history. CouchDB does the versioning automatically, but it is strongly discouraged for programmer's use: "You cannot rely on document revisions for any other purpose than concurrency control." From what I've found on the CouchDB wiki, the versions can get deleted either during compaction or during replication. As far as I can tell, Compaction must always be triggered manually and Replication occurs only when there's more than one database server. The question is: if I won't run compaction and will use only single database instance for my documents, can I just use CouchDB's document versioning and expect it to work? What other problems I might run into? E.g. does not running compaction hurt the performance or consume significantly more disk space (than if I did handle the versioning manually)?

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  • Writing out BMP files with DataBuffer.TYPE_FLOAT or DataBuffer.TYPE_DOUBLE in java

    - by Basil Dsouza
    Hi Guys, I had a problem working with the image classes in java. I am creating a buffered image with DataBuffer.TYPE_DOUBLE. This all works fine in memory (I think). But the problem starts when I try to write it using ImageIO.write. Initially I was getting no exception at all and instead was only getting an empty output file for my troubles.. After a bit of poking around in the code, i found out that the bmp writer doesnt support writing type_double type of files. From: BMPImageWriterSpi.canEncodeImage: if (dataType < DataBuffer.TYPE_BYTE || dataType > DataBuffer.TYPE_INT) return false; So my question is, does anyone have a way of writing out those kind of images to disk? any documentation or tutorial, or link would be helpful. Thanks, Basil Dsouza

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  • Using PHP to place database rows into an array?

    - by Hamed Szilazi
    I was just wondering how i would be able to code perform an SQL query and then place each row into a new array, for example, lets say a table looked like the following: $people= mysql_query("SELECT * FROM friends") Output: | ID | Name | Age | --1----tom----32 --2----dan----22 --3----pat----52 --4----nik----32 --5----dre----65 How could i create a multidimensional array that works in the following way, the first rows second column data could be accessed using $people[0][1] and fifth rows third column could be accessed using $people[4][2]. How would i go about constructing this type of array? Sorry if this is a strange question, its just that i am new to PHP+SQL and would like to know how to directly access data. Performance and speed is not a issue as i am just writing small test scripts to get to grips with the language.

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  • Rails Unit Testing with MyISAM Tables

    - by tadman
    I've got an application that requires the use of MyISAM on a few tables, but the rest are the traditional InnoDB type. The application itself is not concerned with transactions where it applies to these records, but performance is a concern. The Rails testing environment assumes the engine used is transactional, though, so when the test database is generated from the schema.rb it is imported with the same engine. Is it possible to over-ride this behaviour in a simple manner? I've resorted to an awful hack to ensure the tables are the correct type by appending this to test_helper.rb: (ActiveRecord::Base.connection.select_values("SHOW TABLES") - %w[ schema_info ]).each do |table_name| ActiveRecord::Base.connection.execute("ALTER TABLE `#{table_name}` ENGINE=InnoDB") end Is there a better way to make a MyISAM-backed model be testable?

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  • Machine learning in OCaml or Haskell?

    - by griffin
    I'm hoping to use either Haskell or OCaml on a new project because R is too slow. I need to be able to use support vectory machines, ideally separating out each execution to run in parallel. I want to use a functional language and I have the feeling that these two are the best so far as performance and elegance are concerned (I like Clojure, but it wasn't as fast in a short test). I am leaning towards OCaml because there appears to be more support for integration with other languages so it could be a better fit in the long run (e.g. OCaml-R). Does anyone know of a good tutorial for this kind of analysis, or a code example, in either Haskell or OCaml?

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  • Graph visualization code in javascript?

    - by Chris Farmer
    Hi. I have a data structure that represents a directed graph, and I want to render that dynamically on an HTML page. Does anyone know of any javascript code that can do a reasonable job with graph layout? These graphs will usually be just a few nodes, maybe ten at the very upper end, so my guess is that performance isn't going to be a big deal. Ideally, I'd like to be able to hook it in with jQuery so that users can tweak the layout manually by dragging the nodes around. Edit: Google's Visualization API seems to be more "graphs as charts" oriented than "graphs as nodes" oriented. I didn't see any node-oriented visualizations already built there, anyway. Do you know that one exists?

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  • All partitions missing when copying

    - by LiveEn
    I bought a new 320GB SATA hard drive few months ago no recently when i try to copy something to the drive after about 20 seconds the all the partitions in the hard drive suddenly disappears. The hard drive is not shown in either Disk manager or device manager. To get the HD work i have to restart the PC again.The same thing happens when i try to copy. Even when i play any audio or video after abt 5 minutes i get the same problem. The drives are NTFS and im running Windows XP.. Xan some one please help me solve the problem??

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  • Rewrite Query String

    - by Virgil
    Hello, I am trying to write some mod_rewrite rules to generate thumbnails on the fly. So when this url example.com/media/myphoto.jpg?width=100&height=100 the script should rewrite it to example.com/media/myphoto-100x100.jpg and if the file exists on the disk it gets served by Apache and if it doesn't exist it is called a script to generate the file. I wrote this RewriteCond %{QUERY_STRING} ^width=(\d+)&height=(\d+) RewriteRule ^media/([a-zA-Z0-9_\-]+)\.([a-zA-Z0-9]+)$ media/$1-%1x%2.$2 [L] RewriteCond %{QUERY_STRING} ^(.+)? RewriteRule ^media/([a-zA-Z0-9_\-\._]+)$ media/index.php?file=$1&%1 [L] and I get infinite internal redirects. The first condition is matched and the rule is executed and right after that I get an internal redirect. I need advice to finish this script. Thank you.

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  • (fluxus) learning curve

    - by Inaimathi
    I'm trying to have some fun with fluxus, but its manual and online docs all seem to assume that the reader is already an expert network programmer who's never heard of Scheme before. Consequently, you get passages that try to explain the very basics of prefix notation, but assume that you know how to pipe sound-card data into the program, or setup and connect to an OSC process. Is there any tutorial out there that goes the opposite way? IE, assumes that you already have a handle on the Lisp/Scheme thing, but need some pointers before you can properly set up sound sources or an OSC server? Barring that, does anyone know how to get (for example) the system microphone to connect to (fluxus), or how to get it to play a sound file from disk?

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  • Visual Studio web tests: Can a coded webtest be run through the Web Test Editor run view?

    - by Frank Rosario
    Hello, Full disclosure, I'm new to Visual Studio Web Tests and coding for them. I've written a webtest; coded in VB; it runs great. Our QA engineer wants to use this script for performance testing; but he wants the nice GUI that comes when you build a WebTest with the VS WebTest Editor and run it. Is there a way to run a coded webtest through this view? He wants to be able to view each test as it runs to see which pages are having issues, but within the GUI he's used to. Alternatively, I know I could just code something that writes out to a log file; but before I go with that solution; I just wanted to see if this is possible. Any constructive input is greatly appreciated.

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  • What is your opinion of the Telerik Extensions for MVC?

    - by Chad
    I've started digging around with using the Telerik Extensions for MVC. They don't integrate seemlessly into my current project, but I could reorganize things to fit it in. But, I'm wondering if it would be worth it in the end. I've been searching for reviews on the extensions, I haven't seen too many. So I'm asking here. On their website they claim: You can achieve unprecedented performance for your web application with the lightweight, semantically rendered Extensions that completely leverage the ASP.NET MVC model of no postbacks, no ViewState, and no page life cycle. So I'm curious, What is your opinion of the Telerik Extensions for MVC?

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  • Returning several COUNT results from one ASP SQL statement

    - by user89691
    Say I have a table like this: Field1 Field2 Field3 Field4 fred tom fred harry tom tom dick harry harry and I want to determine what proportion of it has been completed for each field. I can execute: SELECT COUNT (Field1) WHERE (Field1 <> '') AS Field1Count SELECT COUNT (Field2) WHERE (Field2 <> '') AS Field2Count SELECT COUNT (Field3) WHERE (Field3 <> '') AS Field3Count SELECT COUNT (Field4) WHERE (Field4 <> '') AS Field4Count Is it possible to roll up these separate SQL statements into one that will return the 4 results in one hit? Is there any performance advantage to doing so (given that the number of columns and rows may be quite large in practice)?

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  • Entity Fremework serialization

    - by Alexandr
    Hello guys! I was confused with my problem. I'm using Entity Framework and want to save entities on hard disk and then to restore them. I have no problem with Serializing/Deserializing but i get an exception "The object cannot be added to the ObjectStateManager because it already has an EntityKey. Use ObjectContext.Attach to attach an object that has an existing key" when i try to add deserialized object to my datacontext. And nothing happens when i just Attach my entity to datacontext How to achieve my goal? Thx in advance! -Alexandr-

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  • MPAPI vs MPI.NET vs ?

    - by Olexandr
    I'm working on college project. I have to develop distributed computing system. And i decided to do some research to make this task fun :) I've found MPAPI and MPI.NET libraries. Yes, they are .NET libraries(Mono, in my case). Why .NET ? I'm choosing between Ada, C++ and C# so to i've choosed C# because of lower development time. I have two goals: Simplicity; Performance; Cluster computing. So, what to choose - MPAPI or MPI.NET or something else ?

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