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  • Critiquing my first Python script

    - by tipu
    A little bit of background: I'm building an inverted index for a search engine. I was originally using PHP, but because of the amount of times I needed to write to disk, I wanted to make a threaded indexer. There's a problem with that because PHP is not thread safe. I then tried Java, but I ended up with at least 20 try catch blocks because of the JSON data structure I was using and working with files. The code was just too big and ugly. Then I figured I should pick up some Python because it's flexible like PHP but also thread safe. Though I'm open to all criticism, what I'd like to learn is the shortcuts that the Python language/library provides that I skipped over. This is a PHP-afide Python script because all I really did was translate the PHP script line by line to what I thought was it's Python equivalent. Thanks. http://pastebin.com/xrg7rf9w

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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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  • 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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  • 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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  • IIS7 Modules - managed or native?

    - by Simon Linder
    Hi all, as the old ISAPI filters are going to die sooner or later, I want to rewrite an old ISAPI filter that was used in IIS 6 into a module for use in IIS 7. The module will be used globally, meaning it will be used within each site, on a Windows Server 2008 R2 with IIS 7.5 installed, that will host several thousand web sites and managing about 50 application pools. My question now is if I should write that module in managed or unmanaged code? One of my concerns regarding managed code is the massive memory consumption due to the .NET framework overhead. I don't know how this would effect the server's performance. I already wrote modules in managed as well as in unmanaged code. So this is not the bothering my decision. But I would prefer to write the module in C# if there are no huge drawbacks. Any suggestions about that issue?

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  • How to insert bulk data into mysql table from asp.net at once.

    - by kranthi
    Hi, I have a requirement that I need to read an excel sheet using asp.net/C# and insert all the records into mysql table.The excel sheet consists of around 2000 rows and 50 columns. Currently,upon reading the excel records ,I am inserting the records one by one using a prepare statement into mysql table.But its taking around 70 secs to do so because of the huge data. I've also thought of creating a new datarow, assigning values to each cell,adding the resulting datarow to datatable and finally calling dataadapter.update(...).But it seems to be complex because I got around 50 columns and hence I'll have to assign 50 values to the datarow. Could someone please suggest if there is an alternate to improve the performance of the insertion? Thanks

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  • GPU YUV to RGB. Worth the effort?

    - by Jaime Pardos
    Hello, I have to convert several full PAL videos (720x576@25) from YUV 4:2:2 to RGB, in real time, and probably a custom resize for each. I have thought of using the GPU, as I have seen some example that does just this (except that it's 4:4:4 so the bpp is the same in source and destiny)-- http://www.fourcc.org/source/YUV420P-OpenGL-GLSLang.c However, I don't have any experience with using GPU's and I'm not sure of what can be done. The example, as I understand it, just converts the video frame to YUV and displays it in the screen. Is it possible to get the processed frame instead? Would it be worth the effort to send it to the GPU, get it transformed, and sending it again to main memory, or would it kill performance? Being a bit platform-specific, assuming I work on windows, is it possible to get an OpenGL or DirectDraw surface from a window so the GPU can draw directly to it?

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  • [OpenGL] I'm having an issue to use GLshort for representing Vertex, and Normal.

    - by Xylopia
    As my project gets close to optimization stage, I notice that reducing Vertex Metadata could vastly improve the performance of 3D rendering. Eventually, I've dearly searched around and have found following advices from stackoverflow. Using GL_SHORT instead of GL_FLOAT in an OpenGL ES vertex array How do you represent a normal or texture coordinate using GLshorts? Advice on speeding up OpenGL ES 1.1 on the iPhone Simple experiments show that switching from "FLOAT" to "SHORT" for vertex and normal isn't tough, but what troubles me is when you're to scale back verticies to their original size (with glScalef), normals are multiplied by the reciprocal of the scale. Then how do you use "short" for both vertex and normal at the same time? I've been trying this and that for about a full day, but I could only go for "float vertex w/ byte normal" or "short vertex w/ float normal" so far. Your help would be truly appreciated.

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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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  • Should I commit or rollback a transaction that creates a temp table, reads, then deletes it?

    - by Triynko
    To select information related to a list of hundreds of IDs... rather than make a huge select statement, I create temp table, insert the ids into it, join it with a table to select the rows matching the IDs, then delete the temp table. So this is essentially a read operation, with no permanent changes made to any persistent database tables. I do this in a transaction, to ensure the temp table is deleted when I'm finished. My question is... what happens when I commit such a transaction vs. let it roll it back? Performance-wise... does the DB engine have to do more work to roll back the transaction vs committing it? Is there even a difference since the only modifications are done to a temp table? Related question here, but doesn't answer my specific case involving temp tables: http://stackoverflow.com/questions/309834/should-i-commit-or-rollback-a-read-transaction

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  • How do you sort files numerically?

    - by Zachary Young
    Hello all, First off, I'm posting this because when I was looking for a solution to the problem below, I could not find one on stackoverflow. So, I'm hoping to add a little bit to the knowledge base here. I need to process some files in a directory and need the files to be sorted numerically. I found some examples on sorting--specifically with using the lamba pattern--at wiki.python.org, and I put this together: #!env/python import re tiffFiles = """ayurveda_1.tif ayurveda_11.tif ayurveda_13.tif ayurveda_2.tif ayurveda_20.tif ayurveda_22.tif""".split('\n') numPattern = re.compile('_(\d{1,2})\.', re.IGNORECASE) tiffFiles.sort(cmp, key=lambda tFile: int(numPattern.search(tFile).group(1))) print tiffFiles I'm still rather new to Python and would like to ask the community if there are any improvements that can be made to this: shortening the code up (removing lambda), performance, style/readability? Thank you, Zachary

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  • A web framework where AJAX was not an after thought

    - by Pirate for Profit
    AJAX is a pain in the ass because it essentially means you'll have to write two sets of similarish code: one for browsers with JavaScript enabled and those without. Not only this, but you have to connect JavaScript events to hook into your models and display the results. And if all that weren't bad enough, you need to send an address change with the request, otherwise the user won't be able to "click back" correctly (if confused look at what happens to the address bar when you click links in GMail). We're searching for something that had the foresight and design goals with all these concerns in mind. Performance and security are also obvious major concerns. We love config-based systems as well, where you don't have to write a lot of code you just drop it into an easily read config format. It's like asking for the holy grail right?

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  • Where to execute extra logic for linq to entities query?

    - by Inez
    Let say that I want to populate a list of CustomerViewModel which are built based on Customer Entity Framework model with some fields (like Balance) calculated separately. Below I have code which works for lists - it is implemented in my service layer, but also I want to execute this code when I just get one item from the database and execute is as well in different services where I'm accessing Customers data as well. How should I do this to ensure performance but to to not duplicate code - the one for calculating Balance? public List<CustomerViewModel> GetCustomerViewModelList() { IQueryable<CustomerViewModel> list = from k in _customerRepository.List() select new CustomerViewModel { Id = k.Id, Name = k.Name, Balance = k.Event.Where(z => z.EventType == (int) EventTypes.Income).Sum(z => z.Amount) }; return list.ToList(); }

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  • Portable C++ library for IPC (processes and shared memory), Boost vs ACE vs Poco?

    - by user363778
    Hi, I need a portable C++ library for doing IPC. I used fork() and SysV shared memory until now but this limits me to Linux/Unix. I found out that there are 3 major C++ libraries that offer a portable solution (including Windows and Mac OS X). I really like Boost, and would like to use it but I need processes and it seems like that this is only an experimental branch until now!? I have never heard of ACE or POCO before and thus I am stuck I do not know which one to choose. I need fork(), sleep() (usleep() would be great) and shared memory of course. Performance and documentation are also important criteria. Thanks, for your Help!

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  • Opening a file from a pack URI in WPF

    - by cptmorgan
    Hi All, I am looking to open a .csv file from the application pack to do some unit testing. So what I would really love is some analog to File.ReadAllText(string path) which is instead X.ReadAllText(Uri uri). I haven't as yet been able to find this. Does anyone know if it is possible to read text / bytes (don't mind which) from a file in the pack without compiling this file to disk first? Oh and btw, File.ReadAllText(@"pack://application:,,,/SpreadSheetEngine/Tests/Example.csv") didn't work for me.. Thanks in advance.. Gav

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  • Random access gzip stream

    - by jkff
    I'd like to be able to do random access into a gzipped file. I can afford to do some preprocessing on it (say, build some kind of index), provided that the result of the preprocessing is much smaller than the file itself. Any advice? My thoughts were: Hack on an existing gzip implementation and serialize its decompressor state every, say, 1 megabyte of compressed data. Then to do random access, deserialize the decompressor state and read from the megabyte boundary. This seems hard, especially since I'm working with Java and I couldn't find a pure-java gzip implementation :( Re-compress the file in chunks of 1Mb and do same as above. This has the disadvantage of doubling the required disk space. Write a simple parser of the gzip format that doesn't do any decompressing and only detects and indexes block boundaries (if there even are any blocks: I haven't yet read the gzip format description)

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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 are the Pros & Cons of using SQL Azure for existing apps on dedicated servers

    - by Mark Redman
    We currently own our own servers, and rent a rack in a datacentre. Looking at the pricing, scalabilty and SLAs for Azure SQL, I am thinking that it might be viable to only use Azure SQL but continue to use our existing applications on our own servers in a datacentres. This will enable us to not worry about the database and its infrastructure so we can concentrate on building an application server farm with disk storeage for files etc. Our application is quite big and has various windows services and parts of it used unmanaged libraries that may not be feasible in the cloud, so probably coulnt have everything in the Azure cloud. The pros: Reduced Total Cost of ownership (no database servers, no sql server licenses) The Cons: I guess there would be overhead in the transfer of data between the Azure Cloud and our datacentre (ie cloud may be in US and datacentre is in the UK) but would this overhead be usable?

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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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  • 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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  • How to make scrolling through images as fast as Apple's Photos app

    - by clozach
    The Goal — On an iPhone, to browse through several hundred locally-stored jpgs using a UIScrollView. The Problem — Like many others before me, I've tried implementing a scroll view based on Apple's Page Control sample code and found it lacking. The biggest issue I'm currently up against is that the sample code's architecture doesn't seem to scale. With just a few images loaded from disk, everything's fine. Once the number of images gets into the dozens, though, scrolling suffers terribly: the scrollview stutters mid-scroll with each new swipe. The only code I've toyed with that comes even close to being reasonably responsive is Three20, but even there the performance doesn't hold a candle to Photos. For now, I'm just using Three20, but a faster, custom solution would definitely be preferable.

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  • Data logged to a file; how do I rotate logs and how do I parse the data to not have 'gaps' in the da

    - by phidah
    I've got a web application that, for performance reasons, throws any data sent into a logfile. I've got two concerns with this approach: How do I best rotate logs, in order to not lose data? For each user session multiple requests are logged. Each request has a unique id so there is an easy way for me to tie the requests to the session. The problem is, however, that if I rotate the logs I risk ending up with one request in one log and another request in another log. How do I arrange my parsing in a way that allows me to parse all requests from a given session? I am willing to define a session timelimit, for example that the requests must, at maximum be 30 minutes apart. If I had a hourly log rotation at 00 minutes: What if the user made one request at 13:59 and one at 14:01 - The user would end up having requests in two different logs.

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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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  • Apache Prefork Configuration

    - by user1618606
    I'm newbie on VPS configuration. So, I've installed apache, php and mysql and now I need to know how to configure Prefork to optimize Apache. The system configuration is: CPU Cores 2 x 2 Ghz @ 4 Ghz RAM Memory 2304 MB DDR3 Burst Memory 3 GB DDR3 Disk Space 30 GB SSD Bandwidth 3 TB SwitchPort 1 Gbps Actually, after linux, mysql, apache and php, there are 250 MB memory in use. Well, I don't have idea to calculate. I saw in some websistes, some vars like: KeepAlive On KeepAliveTimeout 1 MaxKeepAliveRequests 100 StartServers 15 MinSpareServers 15 MaxSpareServers 15 MaxClients 20 MaxRequestsPerChild 0 or StartServers 2 MaxClients 150 MinSpareThreads 25 MaxSpareThreads 75 ThreadsPerChild 25 MaxRequestsPerChild 0 How I could to do: Prefork or worker? Where and how the vars are placed? In httpd.conf? Big hug, Claudio.

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  • MySqlDataAdapter or MySqlDataReader for bulk transfer?

    - by Jeff Meatball Yang
    I'm using the MySql connector for .NET to copy data from MySql servers to SQL Server 2008. Has anyone experienced better performance using one of the following, versus the other? DataAdapter and calling Fill to a DataTable in chunks of 500 DataReader.Read to a DataTable in a loop of 500 I am then using SqlBulkCopy to load the 500 DataTable rows, then continue looping until the MySql record set is completely transferred. I am primarily concerned with using a reasonable amount of memory and completing in a short amount of time. Any help would be appreciated!

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