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• How can I persist a large Perl object for re-use between runs?

  - by Alnitak

  I've got a large XML file, which takes over 40 seconds to parse with XML::Simple. I'd like to be able to cache the resulting parsed object so that on the next run I can just retrieve the parsed object and not reparse the whole file. I've looked at using Data::Dumper but the documentation is a bit lacking on how to store and retrieve its output from disk files. Other classes I've looked at (e.g. Cache::Cache appear designed for storage of many small objects, not a single large one. Can anyone recommend a module designed for this? EDIT. The XML file is ftp://ftp.rfc-editor.org/in-notes/rfc-index.xml On my Mac Pro benchmark figures for reading the entire file with XML::Simple vs Storable are: s/iter test1 test2 test1 47.8 -- -100% test2 0.148 32185% --

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• (NOT) NULL for NVARCHAR columns

  - by Anders Abel

  Allowing NULL values on a column is normally done to allow the absense of a value to be represented. When using NVARCHAR there is aldready a possibility to have an empty string, without setting the column to NULL. In most cases I cannot see a semantical difference between an NVARCHAR with an empty string and a NULL value for such a column. Setting the column as NOT NULL saves me from having to deal with the possibility of NULL values in the code and it feels better to not have to different representations of "no value" (NULL or an empty string). Will I run into any other problems by setting my NVARCHAR columns to NOT NULL. Performance? Storage size? Anything I've overlooked on the usage of the values in the client code?

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• What are some Servlet Container pros and cons for a Solr installation?

  - by danieltalsky

  The SolrInstall wiki page lists seven different server / Servlet Containers compatible with Solr: Tomcat Jetty Resin JBoss WebSphere Weblogic Glassfish I'm sure that "best" is subjective, so I'll just say my criteria are: easiest to set up, best for search performance with a smallish, infrequently-updated dataset, and with the fewest number of gotchas. Jetty and Tomcat both have apt-get solr packages, so they're clearly the frontrunners for some. Jetty is used in the demo install, but there's some notes that Jetty has some difficulties handling Unicode in some cases. Tomcat is a common choice but my understanding is that it's not as lightweight and has a lot of features not needed by Solr. Is it worth considering any of the others? Are there some important pro's and cons I should be aware of?

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• Measuring the time to create and destroy a simple object

  - by portoalet

  From Effective Java 2nd Edition Item 7: Avoid Finalizers "Oh, and one more thing: there is a severe performance penalty for using finalizers. On my machine, the time to create and destroy a simple object is about 5.6 ns. Adding a finalizer increases the time to 2,400 ns. In other words, it is about 430 times slower to create and destroy objects with finalizers." How can one measure the time to create and destroy an object? Do you just do: long start = System.nanoTime(); SimpleObject simpleObj = new SimpleObject(); simpleObj.finalize(); long end = System.nanoTime(); long time = end - start;

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• how to pass in a reference to a string in javascript?

  - by ijjo

  maybe a closure is my solution? not exactly sure how to pull it off though. the code is set up like so: var globalVar = ''; var globalVar2 = ''; function func() { if (condition) func2(globalVar) else func2(globalVar2) } in func2() i cache some HTML in a main container into the appropriate global variable that i pass to it. basically i have a main container that holds different pages depending on what tab they choose. for performance i want to cache the page into global vars so i need to know what tab is active to figure out which global var to assign the html to.

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• Stored Procedure or calculations via IQueryable?

  - by Shawn Mclean

  This is a question that is based on choosing performance over design practices. If I have a method that will be executed many times a second; public static IQueryable<IPerson> InRadius(this IQueryable<IPerson> query, Coordinate center, double radius) { return (from u in query where CallHeavyMathFormula(u, center, radius) select u); } This extension method for IQueryable generates a SQL that does some heavy maths calculation (Cosine, Sine, etc). This would mean the application sends 1-2KB of sql to the server per call. I've heard of placing all application logic, in your application. I also would like to change to a database such as azure or one of those scalable databases in the future. How do I handle something like this? Should I leave it as it is now or write stored procedures? How do applications like twitter or facebook do it?

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• iPhone , core data, whether NSManagedObject use lazy load mechanism when it was create ?

  - by Robin

  Hi, all, I have use core data in app, I have definite a class that most like as follows: @interface Master : NSManagedObject { } @property (nonatomic, retain) NSSet* Details; .... the entity Master contains a property 'Details' that is relate to another table, this is typical Master-Details relationship, I trace the app , but I find a issue that the property 'Details' value was construct even it never be invoked ..... but I consider that the core data 'should' use some lazy mechanism to improve performance, or maybe I miss some configure step ? because the Master entity contains at least five 'Child' table properties , I have to consider this problem before use the core data .... any help ? thanks for your time!

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• Can I tell Borland C++ Builder to copy a file somewhere else after it is built?

  - by MrVimes

  I have two computers. One is intended to be left 'free' for high-performance activities (such as playing games) The other is my 'all purpose' computer where I install all the apps I use for creating things, and so on. On the second computer I use Codegear C++ Builder to work on an app that I use on the first computer. If I have BCB compile to comp 1 it is hopeless. It becomes unresponsive. It compiles locally very quickly. So what I do is compile locally and then copy the exe to the other machine. Well, I'm all for streamlining processes, so I want a way to compile on PC2 and use on PC1 without any intermediate steps. So is it possible to have BCB do the compiling on PC2 and create a local exe file, then copy the file to PC 1?

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• Is there any advantage to having more than 16gb ram on a Windows Dev machine?

  - by Robert Kozak

  Assuming a machine (Dual Quad Core Xeon (2.26GHz) with 24GB RAM) running Windows Server 2008 and Hyper-V. How many VMs can I expect to run at the same time with good performance. Is this overkill? Can you really have too much RAM? Assuming 2GB per VM thats around 16GB for the VMs with 8GB left over for the Main OS and Hyper-V. Sound about right? Edit: Tried to make the question sound less like bragging. Was never my intention. Its a hard question to write.

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• Return an object after parsing xml with SAX

  - by sentimental_turtle

  I have some large XML files to parse and have created an object class to contain my relevant data. Unfortunately, I am unsure how to return the object for later processing. Right now I pickle my data and moments later depickle the object for access. This seems wasteful, and there surely must be a way of grabbing my data without hitting the disk. def endElement(self, name): if name == "info": # done collecting this iteration self.data.setX(self.x) self.data.setY(self.y) elif name == "lastTagOfInterest": # done with file # want to return my object from here filehandler = open(self.outputname + ".pi", "w") pickle.dump(self.data, filehandler) filehandler.close() I have tried putting a return statement in my endElement tag, but that does not seem to get passed up the chain to where I call the SAX parser. Thanks for any tips.

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• What factors could cause the scalability issue on a 10-core CPU?

  - by JackWM

  I am tuning the performance of parallel Java programs. And want to check the impacts from the Architecture. I'm look into the Intel 10-core CPU, Intel(R) Xeon(R) CPU E7-L8867. I found my program only scales up to 5 cores. What could be the causes? I'm considering the Architecture effects. e.g. memory contention? More specifically, Are the 10 cores symmetric to each other? How many memory controllers does it have?

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• Giving Users an Option Between UDP & TCP?

  - by cam

  After studying TCP/UDP difference all week, I just can't decide which to use. I have to send a large amount of constant sensor data, while at the same time sending important data that can't be lost. This made a perfect split for me to use both, then I read a paper (http://www.isoc.org/INET97/proceedings/F3/F3_1.HTM) that says using both causes packet/performance loss in the other. Is there any issue presented if I allow the user to choose which protocol to use (if I program both server side) instead of choosing myself? Are there any disadvantages to this? The only other solution I came up with is to use UDP, and if there seems to be too great of loss of packets, switch to TCP (client-side).

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• How much faster is a database running in RAM?

  - by orokusaki

  I"m looking to run PostgreSQL in RAM for performance enhancement. The database isn't more than 1GB and shouldn't ever grow to more than 5GB. Is it worth doing? Are there any benchmarks out there? Is it buggy? My second major concern is: How easy is it to back things up when it's running purely in RAM. Is this just like using RAM as tier 1 HD, or is it much more complicated?

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• Ternary operators and variable reassignment in PHP

  - by TomcatExodus

  I've perused the questions on ternary operators vs. if/else structures, and while I understand that under normal circumstances there is no performance loss/gain in using ternary operators over if/else structures, I've not seen any mention of this situation. Language specific to PHP (but any language agnostic details are welcome) does the interpreter reassign values in situations like this: $foo = 'bar' $foo = strlen($foo) > 3 ? substr($foo, 0, 3) : $foo; Since this would evaluate to $foo = $foo; is this inefficient, or does the interpreter simply overlook/discard this evaluation? On a side note, what about: !defined('SECURE') ? exit : null;

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• "Single NSMutableArray" vs. "Multiple C-arrays" --Which is more Efficient/Practical?

  - by RexOnRoids

  Situation: I have a DAY structure. The DAY structure has three variables or attributes: a Date (NSString*), a Temperature (float), and a Rainfall (float). Problem: I will be iterating through an array of about 5000 DAY structures and graphing a portion of these onto the screen using OpenGL. Question: As far as drawing performance, which is better? I could simply create an NSMutableArray of DAY structures (NSObjects) and iterate on the array on each draw call -- which I think would be hard on the CPU. Or, I could instead manually manage three different C-Arrays -- One for the Date String (2-Dimensional), One for the temperature (1-Dimensional) and One for the Rainfall (1-Dimensional). I could keep track of the current Day by referencing the current index of the iterated C-Arrays.

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• Python 3-compatibe HTML to text converter preserving basic structure under permissive licence?

  - by hawk64

  I am looking for a relatively simple HTML to text converter which displays links and works on strings. So far I have tried lynx but performance is too bad, html2text which gives weird and verbose markdown output and is under GPLv3 which is too restrictive for my (BSD-licensed) project, http://effbot.org/librarybook/formatter-example-3.py using htmllib.HTMLParser with formatter.AbstractFormatter and a custom writer, however htmllib.HTMLParser is drpeceated and has been removed from Python 3. So is there any simple, performant, Python 3-compatible HTML to text converter under a permissive license such as MIT/BSD/Apache and the like? Edit: I dont just need something to strip HTML-Tags but also to preserve the basic structure of the HTML, that is output that somewhat resembles that of Lynx.

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• Background upload in PHP

  - by Robijntje007

  I am working with a form that allows me to upload files via a local folder and FTP. So I want to move files over ftp (which already works) Because of performance reasons I chose this process to run in the background so I use nfcftpput (linux) In CLI the following command works perfectly: ncftpput-b-u name -p password -P 1980 127.0.0.1 /upload/ /home/Downloads/upload.zip (Knowing that the b-parameter triggers background process) But if I run it via PHP it does not work (without the-b parameter it does) PHP code: $cmd = "ncftpput -b -u name -p password -P 1980 127.0.0.1 /upload/ /home/Downloads/upload.zip"; $return = exec($cmd);

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• Is a PHP-only "cache engine" ever worth it?

  - by adsads

  I wrote a rather small skeleton for my web apps and thought that I would also add a small cache for it. It is rather simple: If the current page exists as a file in the cache and the file isn't too old, read it out and exit instead of rebuilding the page If the current page isn't cached/outdated recalc the page and save it However, the bad thing about it is: My performance tests with a page that receives 40 relatively long posts via a MySQL query said that with using the cache, it took even longer to handle a single request (1000 tests each) How can that happen? Should I just remove the complete raw-PHP cache and relieve on the availability of some PHP cache like memcached or so?

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• Rails ActiveRecord - How to set association save order

  - by Altonymous

  I have a weird relationship that needs to be maintained for legacy processes. I'm trying to figure out how to create the relationship given the new model association. New Relationship Setup Machine has_many MachineReadings has_many Disks has_many DiskReadings Old Relationship Setup Machine has_many MachineReadings has_many DiskReadings has_many Disks The problem is data will come in on the Machine model as nested attributes using the new relationship setup. I need to update the machine_reading_id in the DiskReading model so the old association can continue to be used. I tried doing this via an after_save hook that would traverse back up to the machine and then down to the readings to get the machine_reading.id so I could populate the DiskReading model. However, the associations aren't being saved in the order I would expect. They are saving the Disks & DiskReadings before saving the MachineReadings. So when I go after the machine_reading.id it hasn't been written and thus I am unable to get access to it. For example: #machine_disk_reading.rb after_save :build_old_relationship def build_old_relationship self.machine_reading_id = self.disk.machine.readings.find_by_date_time(self.date_time).id end

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• Visual C++ 9 Linker file size limitation.

  - by Raindog

  It appears that the visual C++ 9 linker has a file allocation algorithm that doubles the size of the file every allocation, so you get 512mb, 1024mb, 2048mb, 4096mb. The problem is that it is using a library that cannot handle files larger 2048MB, and as such crashes with an error such as "cannot read file at is the disk full or write protected". Is there a way to bypass this limitation or otherwise replace the linker with something else that works? A bit of background, I have a code generator that generates a large number of files, ~15k cpp files, I've managed to reduce the number of files to something about 6k to get something that at least completes the linking process, I would like to be able to include all 15k without having to create multiple libs.

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• Should I Split Tables Relevant to X Module Into Different DB? Mysql

  - by Michael Robinson

  I've inherited a rather large and somewhat messy codebase, and have been tasked with making it faster, less noodly and generally better. Currently we use one big database to hold all data for all aspects of the site. As we need to plan for significant growth in the future, I'm considering splitting tables relevant to specific sections of the site into different databases, so if/when one gets too large for one server I can more easily migrate some user data to different mysql servers while retaining overall integrity. I would still need to use joins on some tables across the new databases. Is this a normal thing to do? Would I incur a performance hit because of this?

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• messages stuck permanently in session

  - by Tim Whitlock

  I am getting Drupal messages stuck permanently in session, so that after being displayed they are not cleared. The unsetting code in function drupal_get_messages in bootstrap.inc is firing - It's as if the session is sleeping (i.e. serializing to disk) before the messages array is cleared. Have you witnessed such a thing? UPDATE The call that commits the session starts from drupal_page_footer at the bottom of index.php - for some reason this is executing twice per request! once with the emptied messages and then again with the messages back in the array.

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• guide on crawling the entire web ?

  - by bohohasdhfasdf

  i just had this thought, and was wondering if it's possible to crawl the entire web (just like the big boys!) on a single dedicated server (like Core2Duo, 8gig ram, 750gb disk 100mbps) . I've come across a paper where this was done....but i cannot recall this paper's title. it was like about crawling the entire web on a single dedicated server using some statistical model. Anyways, imagine starting with just around 10,000 seed URLs, and doing exhaustive crawl.... is it possible ? I am in need of crawling the web but limited to a dedicated server. how can i do this, is there an open source solution out there already ? for example see this real time search engine. http://crawlrapidshare.com the results are exteremely good and freshly updated....how are they doing this ?

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• ASP.NET Website or Web service?

  - by fireBand

  Hi, I am trying to implement a service to download a image file. The code does nothing but upload a file to the response with each client request. There are no SOAP messages involved but I am planning to implement it as ASP.NET web service. It can also be implement as ASP.NET website but since it has no view (forms, html etc) I planned to implement a web-service. Is this a better approach? Does ASP.NET Website offer better performance that a Web-service? Which one would be better is this situation? Thanks in advance.

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• Organizing PHP includes in your development environment

  - by Andrew Heath

  I'm auditing my site design based on the excellent Essential PHP Security by Chris Shiflett. One of the recommendations I'd like to adopt is moving all possible files out of webroot, this includes includes. Doing so on my shared host is simple enough, but I'm wondering how people handle this on their development testbeds? Currently I've got an XAMPP installation configured so that localhost/mysite/ matches up with D:\mysite\ in which includes are stored at D:\mysite\includes\ In order to keep include paths accurate, I'm guess I need to replicate the server's path on my local disk? Something like D:\mysite\public_html\ Is there a better way?

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