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  • sql UPDATE, a calculation is used multiple times, can it just be calculated once?

    - by Zachery Delafosse
    UPDATE `play` SET `counter1` = `counter1` + LEAST(`maxchange`, FLOOR(`x` / `y`) ), `counter2` = `counter2` - LEAST(`maxchange`, FLOOR(`x` / `y`) ), `x` = MOD(`x`, `y`) WHERE `x` `y` AND `maxchange` 0 As you can see, " LEAST(`maxchange`, FLOOR(`x` / `y`) ) " is used multiple times, but it should always have the same value. Is there a way to optimize this, to only calculate once? I'm coding this in PHP, for the record.

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  • Why would using a Temp table be faster than a nested query?

    - by Mongus Pong
    We are trying to optimise some of our queries. One query is doing the following: SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, INTO [#Gadget] FROM task t SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) as Client FROM [#Gadget] order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC DROP TABLE [#Gadget] (I have removed the complex subquery, cos I dont think its relevant other than to explain why this query has been done as a two stage process.) Now I would have thought it would be far more efficient to merge this down into a single query using subqueries as : SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) FROM ( SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, FROM task t ) as sub order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC This would give the optimiser better information to work out what was going on and avoid any temporary tables. It should be faster. But it turns out it is a lot slower. 8 seconds vs under 5 seconds. I cant work out why this would be the case as all my knowledge of databases imply that subqueries would always be faster than using temporary tables. Can anyone explain what could be going on!?!?

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  • Why is Postgres doing a Hash in this query?

    - by Claudiu
    I have two tables: A and P. I want to get information out of all rows in A whose id is in a temporary table I created, tmp_ids. However, there is additional information about A in the P table, foo, and I want to get this info as well. I have the following query: SELECT A.H_id AS hid, A.id AS aid, P.foo, A.pos, A.size FROM tmp_ids, P, A WHERE tmp_ids.id = A.H_id AND P.id = A.P_id I noticed it going slowly, and when I asked Postgres to explain, I noticed that it combines tmp_ids with an index on A I created for H_id with a nested loop. However, it hashes all of P before doing a Hash join with the result of the first merge. P is quite large and I think this is what's taking all the time. Why would it create a hash there? P.id is P's primary key, and A.P_id has an index of its own.

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  • Should i really use integer primary IDs [sql]

    - by arthurprs
    For example, i always generate an auto-increment field for the users table, but i also specifies an UNIQUE index on their usernames. There is situations that i first need to get the userId for a given username and then execute the desired query. Or use a JOIN in the desired query. It's 2 trips to the database or a JOIN vs. a varchar index The above is just an example There is a real performance benefit on INT over small VARCHAR indexes? Thanks in advance!

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  • Building nginx 1.0.4 on Amazon EC2 micro - perl and python problems

    - by digitaltoast
    I'd like to run nginx as a reverse proxy with apache2 on my EC2 micro instance. yum install nginx gives me nginx-0.8.53-1.2.amzn1.x86_64.rpm The current nginx is 1.0.4 I found and followed this guide: http://kdn2.info/2011/05/install-nginx-on-amazon-ec2/ It works fine up to and including "make". When I get to checkinstall --fstrans=no I get ERROR: ld.so: object '/usr/lib/installwatch.so' from LD_PRELOAD cannot be preloaded: ignored. test -d '/var/log/nginx' || mkdir -p '/var/log/nginx' ERROR: ld.so: object '/usr/lib/installwatch.so' from LD_PRELOAD cannot be preloaded: ignored. make[1]: Leaving directory `/root/src/nginx-1.0.4' ======================== Installation successful ========================== Copying documentation directory... ./ ./CHANGES ./LICENSE ./README cp: cannot stat `//var/tmp/gRWoVgIcdbmjfTjoVGBM/newfiles.tmp': No such file or directory Copying files to the temporary directory...OK Striping ELF binaries and libraries...OK Compressing man pages...OK Building file list...OK Building RPM package... FAILED! *** Failed to build the package ...and the logfile is full of: Building target platforms: x86_64 Building for target x86_64 Processing files: nginx-1.0.4-1.x86_64 error: File not found: /usr/src/rpm/BUILDROOT/nginx-1.0.4-1.x86_64/usr error: File not found: /usr/src/rpm/BUILDROOT/nginx-1.0.4-1.x86_64/usr/doc There IS /usr/src/rpm/BUILDROOT/nginx-1.0.4-1.x86_64/ but no /usr Following further down the page, it says: "If we want to use, for example, PHP 5.2 we can download PHP and Nginx compatible with Amazon Kernel(Xen Kernel) from the CentosALT Repository." So I install the two repositories, but when I yum install http://centos.alt.ru/pub/nginx/1.0/RPMS/x86_64/nginx-stable-1.0.4-1.el5.x86_64.rpm I get Error: Package: nginx-stable-1.0.4-1.el5.x86_64 (/nginx-stable-1.0.4-1.el5.x86_64) Requires: perl(:MODULE_COMPAT_5.8.8) You could try using --skip-broken to work around the problem but that doesn't fix it. When I do yum update, I get --> Finished Dependency Resolution Error: Package: python-distribute-0.6.19-10.1.x86_64 (devel_languages_python) Requires: python < 2.5 Installed: 1:python-2.6-1.19.amzn1.noarch (@amzn-main) python = 1:2.6-1.19.amzn1 Error: Package: python-distribute-0.6.19-10.1.i586 (devel_languages_python) Requires: python < 2.5 Installed: 1:python-2.6-1.19.amzn1.noarch (@amzn-main) python = 1:2.6-1.19.amzn1 I've tried everything - yum clean all and various other suggestions found on other sites. If anyone has any suggestions or a known package of the current 1.04 nginx working on EC2 Micro (Linux ip-10-56-63-85 2.6.35.11-83.9.amzn1.x86_64 #1 SMP Sat Feb 19 23:42:04 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux - which I think is RHEL 5?) then I'd be grateful. Incidentally, does this repolist look right? repo id repo name status CentALT CentALT Packages for Enterprise Linux 5 - x86_64 enabled: 112+157 amzn-main amzn-main-Base enabled: 2,706 amzn-main-debuginfo amzn-main-debuginfo disabled amzn-main-nosrc amzn-main-nosrc disabled amzn-updates amzn-updates-Base enabled: 328 amzn-updates-debuginfo amzn-updates-debuginfo disabled amzn-updates-nosrc amzn-updates-nosrc disabled devel_languages_python Python and Python Modules (SLE_10) enabled: 1,452+768 epel Extra Packages for Enterprise Linux 5 - x86_64 enabled: 5,892+604 epel-debuginfo Extra Packages for Enterprise Linux 5 - x86_64 - Debug disabled epel-source Extra Packages for Enterprise Linux 5 - x86_64 - Source disabled epel-testing Extra Packages for Enterprise Linux 5 - Testing - x86_64 disabled epel-testing-debuginfo Extra Packages for Enterprise Linux 5 - Testing - x86_64 - Debug disabled epel-testing-source Extra Packages for Enterprise Linux 5 - Testing - x86_64 - Source disabled s3tools Tools for managing Amazon S3 - Simple Storage Service (RHEL_6) enabled: 2+1 repolist: 10,492

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  • How to debug solve 500 Internal error aws micro ec2 with suexec, Apache and php CGi

    - by Oudin
    I'm running WordPress multi-site on an amazon micro ec2 with suexec, Apache and php CGi On Ubuntu 12.04 However I've been experiencing a lot of Internal server 500 errors and I'm in the process of debugging it to find a solution. I've posted my error logs below example.com error.log: [Fri Oct 26 10:10:08 2012] [warn] [client 23.23.xxx.xx] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server [Fri Oct 26 10:10:08 2012] [error] [client 23.23.xxx.xx] Premature end of script headers: wp-cron.php [Fri Oct 26 10:50:04 2012] [warn] [client 190.213.xxx.xxx] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: https://www.example.com/wp-admin/ [Fri Oct 26 10:50:04 2012] [error] [client 190.213.xxx.xxx] Premature end of script headers: admin.php, referer: https://www.example.com/wp-admin/ [Fri Oct 26 10:58:14 2012] [warn] [client 190.213.xxx.xxx] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: https://www.example.com/wp-admin/network/index.php [Fri Oct 26 10:58:15 2012] [error] [client 190.213.xxx.xxx] Premature end of script headers: admin-ajax.php, referer: https://www.example.com/wp-admin/network/index.php [Fri Oct 26 10:58:56 2012] [warn] [client 190.213.xxx.xxx] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: https://www.example.com/wp-admin/network/index.php [Fri Oct 26 10:58:57 2012] [error] [client 190.213.xxx.xxx] Premature end of script headers: plugins.php, referer: https://www.example.com/wp-admin/network/index.php [Fri Oct 26 10:59:18 2012] [warn] [client 190.213.xxx.xxx] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: https://www.example.com/wp-admin/network/index.php [Fri Oct 26 10:59:18 2012] [error] [client 190.213.xxx.xxx] Premature end of script headers: admin-ajax.php, referer: https://www.example.com/wp-admin/network/index.php [Fri Oct 26 11:01:49 2012] [warn] [client 190.213.xxx.xxx] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: https://www.example.com/wp-admin/ [Fri Oct 26 11:01:49 2012] [warn] [client 190.213.xxx.xxx] (104)Connection reset by peer: mod_fcgid: ap_pass_brigade failed in handle_request_ipc function, referer: https://www.example.com/wp-admin/ Apache Log: php (pre-forking): Cannot allocate memory php (pre-forking): Cannot allocate memory Recipient names must be specified Recipient names must be specified php (pre-forking): Cannot allocate memory php (pre-forking): Cannot allocate memory php (pre-forking): Cannot allocate memory [Fri Oct 26 10:49:33 2012] [warn] mod_fcgid: cleanup zombie process 2852 [Fri Oct 26 10:49:33 2012] [warn] mod_fcgid: cleanup zombie process 2851 [Fri Oct 26 10:49:33 2012] [warn] mod_fcgid: cleanup zombie process 2853 [Fri Oct 26 10:58:22 2012] [warn] mod_fcgid: process 2892 graceful kill fail, sending SIGKILL php (pre-forking): Cannot allocate memory [Fri Oct 26 10:59:21 2012] [warn] mod_fcgid: process 2894 graceful kill fail, sending SIGKILL [Fri Oct 26 10:59:25 2012] [warn] mod_fcgid: process 2866 graceful kill fail, sending SIGKILL suexec.log: [2012-10-25 16:05:36]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-25 18:09:38]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-25 18:09:51]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-25 18:14:03]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-25 18:14:06]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-25 18:14:35]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-25 20:20:27]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-25 20:20:29]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-25 20:20:31]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-25 21:42:12]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-25 22:56:50]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-26 02:34:43]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-26 04:25:07]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-26 06:35:19]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-26 06:40:05]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-26 07:22:45]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-26 10:10:05]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-26 10:49:24]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi [2012-10-26 10:49:24]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi based on the logs can any determine what might be the cause of this? Thinking that it might be the micro instance I'm thinking of upgrading to a small. Any help would be greatly appreciated.

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  • Optimise Apache for EC2 micro instance

    - by Shiyu Sekam
    I'm running apache2 on a EC2 micro instance with ~600 mb RAM. The instance was running for almost a year without problems, but in the last weeks it just keeps crashing, because the server reached MaxClients. The server basically runs few websites, one wordpress blog(not often used), company website(most used) and 2 small sites, which are just internal. The database for the blog runs on RDS, so there's no Mysql running on this web server. When I came to the company, the server already was setup and is running apache + mod_php + prefork. We want to migrate that in the future to a nginx + php-fpm, but it still needs further testing. So for now I have to stick with the old setup. I also use CloudFlare DDOS protection in front of the server, because it was attacked a couple of the times in the last weeks. My company don't want to pay money for a better web server at this point, so I have to stick with the micro instance also. Additionally the code for the website we run is really bad and slow and sometimes a single page load can take up to 15 seconds. The whole website is dynamic and written in PHP, so caching isn't really an option here. It's a customized search for users. I've already turned off KeepAlive, which improved the performance a little bit. My prefork config looks like the following: StartServers 2 MinSpareServers 2 MaxSpareServers 5 ServerLimit 10 MaxClients 10 MaxRequestsPerChild 100 The server just becomes unresponsive after a while running and I've run the following command to see how many connections there are: netstat | grep http | wc -l 75 Trying to restart apache helps for a short moment, but after that a while the apache process(es) become unresponsive again. I've the following modules enabled(output of apache2ctl -M) Loaded Modules: core_module (static) log_config_module (static) logio_module (static) version_module (static) mpm_prefork_module (static) http_module (static) so_module (static) alias_module (shared) authz_host_module (shared) deflate_module (shared) dir_module (shared) expires_module (shared) mime_module (shared) negotiation_module (shared) php5_module (shared) rewrite_module (shared) setenvif_module (shared) ssl_module (shared) status_module (shared) Syntax OK apache2.conf # Security ServerTokens OS ServerSignature On TraceEnable On ServerName "web.example.com" ServerRoot "/etc/apache2" PidFile ${APACHE_PID_FILE} Timeout 30 KeepAlive off User www-data Group www-data AccessFileName .htaccess <Files ~ "^\.ht"> Order allow,deny Deny from all Satisfy all </Files> <Directory /> Options FollowSymLinks AllowOverride None </Directory> DefaultType none HostnameLookups Off ErrorLog /var/log/apache2/error.log LogLevel warn EnableSendfile On #Listen 80 Include /etc/apache2/mods-enabled/*.load Include /etc/apache2/mods-enabled/*.conf Include /etc/apache2/ports.conf LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined LogFormat "%h %l %u %t \"%r\" %>s %b" common LogFormat "%{Referer}i -> %U" referer LogFormat "%{User-agent}i" agent Include /etc/apache2/conf.d/*.conf Include /etc/apache2/sites-enabled/*.conf Vhost of main site <VirtualHost *:80> ServerName www.example.com ## Vhost docroot DocumentRoot /srv/www/jenkins/Web ## Directories, there should at least be a declaration for /srv/www/jenkins/Web <Directory /srv/www/jenkins/Web> AllowOverride All Order allow,deny Allow from all </Directory> ## Load additional static includes ## Logging ErrorLog /var/log/apache2/www.example.com.error.log LogLevel warn ServerSignature Off CustomLog /var/log/apache2/www.example.com.access.log combined ## Rewrite rules RewriteEngine On RewriteCond %{HTTP_HOST} !^www.example.com$ RewriteRule ^.*$ http://www.example.com%{REQUEST_URI} [R=301,L] ## Server aliases ServerAlias www.example.invalid ServerAlias example.com ## Custom fragment <Location /srv/www/jenkins/Web/library> Order Deny,Allow Deny from all </Location> <Files ~ "^\.(.+)"> Order deny,allow deny from all </Files> </VirtualHost>

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  • Sortie de Micro Focus Rumba 9.0 : l'émulateur de terminal offre trois types d'UI pour les applications mainframe, dont celle de l'iPad

    Micro Focus Rumba disponible dans sa version 9.0 La suite d'émulation de terminal propose trois interfaces pour les applications mainframe Micro Focus, éditeur de solutions de gestion, de test et de modernisation d'applications d'entreprise, vient de présenter les principales nouveautés apportées par la version 9 de sa suite d'émulation de terminal Rumba. [IMG]http://ftp-developpez.com/gordon-fowler/Micro%20Focus%20Rumba%20iPad.jpg[/IMG] Rumba version iPad Rumba, dans sa version 9.0, propose dorénavant trois interfaces afin d'émuler les applications mainframe : l'interface Desktop à laquelle...

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  • Visual COBOL 2.1 : COBOL à l'heure de Windows 8, Micro Focus sort sa nouvelle solution de développement et de déploiement

    Visual COBOL 2.1 : COBOL à l'heure de Windows 8 Micro Focus sort sa nouvelle solution de développement et de déploiement d'applications Visual COBOL 2.1 ? la dernière version de la solution de Micro Focus parmi les plus populaires du marché ? met de l'environnement de développement COBOL à l'heure de Windows 8 (et prend donc en charge Visual Studio 2012). [IMG]http://ftp-developpez.com/gordon-fowler/Micro%20Focus%20Visual%20Cobol%202.1%20Visual%20Studio%202012small.png[/IMG] « Les développeurs sont donc aujourd'hui en m...

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  • SQL SERVER – Four Posts on Removing the Bookmark Lookup – Key Lookup

    - by pinaldave
    In recent times I have observed that not many people have proper understanding of what is bookmark lookup or key lookup. Increasing numbers of the questions tells me that this is something developers are encountering every single day but have no idea how to deal with it. I have previously written three articles on this subject. I want to point all of you looking for further information on the same post. SQL SERVER – Query Optimization – Remove Bookmark Lookup – Remove RID Lookup – Remove Key Lookup SQL SERVER – Query Optimization – Remove Bookmark Lookup – Remove RID Lookup – Remove Key Lookup – Part 2 SQL SERVER – Query Optimization – Remove Bookmark Lookup – Remove RID Lookup – Remove Key Lookup – Part 3 SQL SERVER – Interesting Observation – Execution Plan and Results of Aggregate Concatenation Queries In one of my recent class we had in depth conversation about what are the alternative of creating covering indexes to remove the bookmark lookup. I really want to this question open to all of you and see what community thinks about the same. Is there any other way then creating covering index or included index to remove his expensive keylookup? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Backup and Restore, SQL Index, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLAuthority News, SQLServer, T SQL, Technology

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  • Micro sound breaks/interrupts on Windows 7

    - by cand
    Hello all, I've been experiencing strange behavior recently. When listening to mp3 or watching movie or whatever that uses sound, I get micro breaks in sound. It's like it hangs or cuts a fragment for about 0.5s. When I start OS, it's ok, but as time passes it gets worse, to the extent that music is unlistenable being interrupted every 2 seconds. I haven't found any relevance between this behavior and hardware usage, I don't think it's directly related to HDD (or it might be but with significant delay). I have updated soundcard drivers and it didn't help a lot. My system is Windows 7, computer is simple HP laptop, nx7300-Ru374ES with WD Caviar Scorpio Blue hard drive inside and integrated soundcard on it (I can check the model later if it's important). Did anybody encounter such problem ? Maybe it's a common thing on Windows 7 or someone knows how to solve it? Thanks in advance.

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  • Not able to login to new AMI on EC2 - moveing from micro to small instance

    - by zengr
    I had a t1.micro instance (old_server) on Linux on EC2 and now I need to upgrade my server to m1.small Linux (new_server). So, here is what I did: Shutdown old_server and create an AMI. Launch the new AMI with m1.small configuration. (I kept the key and security group same as old_server) I tried to login by: ssh -i my_key.pem [email protected] But, it gives a connection timeout error. My login to old_server works fine. So, my question is: What is the correct way to scale up (vertically) an EC2 instance? Where am I going wrong in the above mentioned step? When I create an AMI in step 1, is the EBS (data) also copied.

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  • bottle.py on EC2 micro instance causes 2 order of magnitude slowdown

    - by user61633
    Cross-posted from StackOverflow: I wrote a little toy script to solve this type of game, and put it on my new micro EC2 instance. It works perfectly, but while it takes around 0.5 seconds to run a local version, and takes under 0.5 seconds to run both the local and the bottle.py version on my home computer, running the bottle.py version on the EC2 instance takes over 2 minutes. Python has the cpu pegged at 99% the entire time. Only 7.4% memory usage, consistently, and no swapping. The only guess I have is initialization time for bottle.py on EC2, but if it were that, why would it be ~200x faster on my own computer with bottle.py?

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  • Extreme Optimization Numerical Libraries for .NET – Part 1 of n

    - by JoshReuben
    While many of my colleagues are fascinated in constructing the ultimate ViewModel or ServiceBus, I feel that this kind of plumbing code is re-invented far too many times – at some point in the near future, it will be out of the box standard infra. How many times have you been to a customer site and built a different variation of the same kind of code frameworks? How many times can you abstract Prism or reliable and discoverable WCF communication? As the bar is raised for whats bundled with the framework and more tasks become declarative, automated and configurable, Information Systems will expose a higher level of abstraction, forcing software engineers to focus on more advanced computer science and algorithmic tasks. I've spent the better half of the past decade building skills in .NET and expanding my mathematical horizons by working through the Schaums guides. In this series I am going to examine how these skillsets come together in the implementation provided by ExtremeOptimization. Download the trial version here: http://www.extremeoptimization.com/downloads.aspx Overview The library implements a set of algorithms for: linear algebra, complex numbers, numerical integration and differentiation, solving equations, optimization, random numbers, regression, ANOVA, statistical distributions, hypothesis tests. EONumLib combines three libraries in one - organized in a consistent namespace hierarchy. Mathematics Library - Extreme.Mathematics namespace Vector and Matrix Library - Extreme.Mathematics.LinearAlgebra namespace Statistics Library - Extreme.Statistics namespace System Requirements -.NET framework 4.0  Mathematics Library The classes are organized into the following namespace hierarchy: Extreme.Mathematics – common data types, exception types, and delegates. Extreme.Mathematics.Calculus - numerical integration and differentiation of functions. Extreme.Mathematics.Curves - points, lines and curves, including polynomials and Chebyshev approximations. curve fitting and interpolation. Extreme.Mathematics.Generic - generic arithmetic & linear algebra. Extreme.Mathematics.EquationSolvers - root finding algorithms. Extreme.Mathematics.LinearAlgebra - vectors , matrices , matrix decompositions, solvers for simultaneous linear equations and least squares. Extreme.Mathematics.Optimization – multi-d function optimization + linear programming. Extreme.Mathematics.SignalProcessing - one and two-dimensional discrete Fourier transforms. Extreme.Mathematics.SpecialFunctions

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  • Beginners guide to developing optimization software

    - by Florenc
    I am novice in "serious" programming i.e. applications that deal with real-life applications and software projects that go beyond school assignments. My interests include optimization, operations research, algorithms and lately i discovered how much I do like software design/development/engineering. I have already developed some simple desktop applications for some "famous" problems like TSP using heuristc approaches, a VRP solver (in progress) and so on. While developing this kind of software I actually used basic concepts taught at school such as object-orientation analysis and design. But, I found these courses rather elementary and quite boring (for my expectations). So I decided to go a little further and start developing "real" software (and this is where I realized how important and interesting software engineering/design is.) Now, here's my issue: I can not find a "study guide" for developing software of this kind. Currently, there are numerous resources out there (books, websites, tutorials) in designing and developing complex IS, web applications, smartphone apps but I can't find a book for example entitled "optimization software development". Definetly, someone could claim that "design patterns apply to software in general" but that's not my point. My point is that I could simply use my imagination for "simple" implementations, but what happens, when my imagination can not go further? In other words I'm looking for a guide/path to bridge the gap between: Mathematics-Algorithm Design-Software Engineering-Optimization-Software development

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  • Critical Threads Optimization

    - by Rafael Vanoni
    Background One of the more common issues we've been seeing in the field is the growing difficulty in optimizing performance of multi-threaded applications. A good portion of this difficulty is due to the increasing complexity of modern processors that present various degrees of sharing relationships between hardware components. Take any current CMT processor and you'll find any number of CPUs sharing execution pipelines, floating point units, caches, etc. Consequently, applying the traditional recipe of one software thread for each CPU will have varying degrees of success, according to the layout of the underlying hardware. On top of this increasing complexity we've also seen processors with features that aim at dynamically resourcing software threads according to their utilization. Intel's Turbo Boost allows processors to increase their operating frequency if there is enough thermal headroom available and the processor isn't fully utilized. More recently, the SPARC T4 processor introduced dynamic threading, allowing each core to dynamically allocate more resources to its active CPUs. Both cases are in essence recognizing that current processors will be running a wide mix of workloads, some will be designed for throughput, others for low latency. The hardware is providing mechanisms to dynamically resource threads according to their runtime behavior. We're very aware of these challenges in Solaris, and have been working to provide the best out of box performance while providing mechanisms to further optimize applications when necessary. The Critical Threads Optimzation was introduced in Solaris 10 8/11 and Solaris 11 as one such mechanism that allows customers to both address issues caused by contention over shared hardware resources and explicitly take advantage of features such as T4's dynamic threading. What it is The basic idea is to allow performance critical threads to execute with more exclusive access to hardware resources. For example, when deploying an application that implements a producer/consumer model, it'll likely be advantageous to give the producer more exclusive access to the hardware instead of having it competing for resources with all the consumers. In the case of a T4 based system, we may want to have a producer running by itself on a single core and create one consumer for each of the remaining CPUs. With the Critical Threads Optimization we're extending the semantics of scheduling priorities (which thread should run first) to include priority over shared resources (which thread should have more "space"). Now the scheduler will not only run higher priority threads first: it will also provide them with more exclusive access to hardware resources if they are available. How does it work ? Using the previous example in Solaris 11, all you'd have to do would be to place the producer in the Fixed Priority (FX) scheduling class at priority 60, or in the Real Time (RT) class at any priority and Solaris will try to give it more "hardware space". On both Solaris 10 8/11 and Solaris 11 this can be achieved through the existing priocntl(1,2) and priocntlset(2) interfaces. If your application already assigns these priorities to performance critical threads, there's no additional step you need to take. One important aspect of this optimization is that it requires some level of idleness in the system, either as a result of sizing the application before hand or through periods of transient idleness during runtime. If the system is fully committed, the scheduler will put all the available CPUs to work.Best practices If you're an application developer, we encourage you to look into assigning the right priorities for the different threads in your application. Solaris provides different scheduling classes (Time Share, Interactive, Fair Share, Fixed Priority and Real Time) that offer different policies and behaviors. It is not always simple to figure out which set of threads are critical to the performance of a workload, and it may not always be feasible to take advantage of this optimization, but we believe that this can be correctly (and safely) done during development. Overall, the out of box performance in Solaris should meet your workload's requirements. If you are looking into that extra bit of performance, then the Critical Threads Optimization may be what you're looking for.

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  • Strange IIS hits originating from Trend Micro

    - by TesterTurnedDeveloper
    I'm trying to trace thru an error on a extranet site I maintain. I've had a look thru the logs, and I'm seeing hits originate from these IP addresses: 216.104.15.130 216.104.15.138 216.104.15.142 216.104.15.13 150.70.84.49 150.70.84.44 Network-tools.com gives 'TREND MICRO INCORPORATED' as the owner of all these IPs. The hits fail as they aren't sending any cookies (therefore aren't considered logged in). The hits are to pages containing URLs that only the logged in user would see, i.e. ImageEdit.aspx?ImageId=467424. I.e. the server isn't guessing these URLs, someone would have to log into the site to know these URLs exist. Theory: the Trend Antivirus client grabs URLs and sends them to the server for 'extra processing'? Googling around gives me this: http://www.forumpostersunion.com/showthread.php?p=51272 - where people are reporting comment spam from these addresses. The articles says their servers have been hacked (a few months ago, presumably fixed now?). A hacked server wouldn't explain how the URLs have been plucked off the user's PCs. Has anyone seen this before? Anything nefarious going on here?

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  • APC fragmentation on EC2 Micro for Wordpress + W3TC

    - by Maarten Provo
    I'm trying to optimize APC for my Amazon EC2 Micro server running one Wordpress-site with W3TC. I've started with the settings advised by TechZilla in another topic but I keep getting high fragmentation with 50% of space being free. I've uploaded an image to http://www.maartenprovo.be/downloads/apc.jpg but I can't post it here since I need at least 10 reputation. What values can I optimize to prevent fragmentation? [apc] apc.enabled=1 apc.shm_segments=1 ;32M per WordPress install apc.shm_size=164M ;Leave at 2M or lower. WordPress does't have any file sizes close to 2M apc.max_file_size=2M ;Relative to the number of cached files apc.num_files_hint=1000 ;Relative to the size of WordPress apc.user_entries_hint=4096 ;The number of seconds a cache entry is allowed to idle in a slot before APC dumps the cache apc.ttl=7200 apc.user_ttl=7200 apc.gc_ttl=3600 ;Auto update chache files on change in WP-ADMIN or W3TC apc.stat=1 ;This MUST be 0, WP can have errors otherwise! apc.include_once_override=0 ;Only set to 1 while debugging apc.enable_cli=0 ;Allow 2 seconds after a file is created before it is cached to prevent users from seeing half-written/weird pages apc.file_update_protection=2 ;Ignore files apc.filters apc.slam_defense = 0 apc.write_lock = 1 apc.cache_by_default=1 apc.use_request_time=1 apc.mmap_file_mask=/var/tmp/apc.XXXXXX apc.stat_ctime=0 apc.canonicalize=1 apc.write_lock=1 apc.report_autofilter=0 apc.rfc1867=0 apc.rfc1867_prefix =upload_ apc.rfc1867_name=APC_UPLOAD_PROGRESS apc.rfc1867_freq=0 apc.rfc1867_ttl=3600 apc.lazy_classes=0 apc.lazy_functions=0

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  • Premature optimization is the root of all evil, but can it ever be too late?

    - by polygenelubricants
    "We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil" So what is that 3% like? Can the avoidance of premature optimization ever be taken too extreme that it does more harm than good? Even if it's rare, has there been a case of a real measurable software engineering disaster due to complete negligence to optimize early in the process? Bonus question: is software engineering pretty much the only field that has such a counter intuitive principle regarding doing something earlier rather than later before things potentially become too big a problem to fix? Personal question: how do you justify something as premature optimization and not just a case of you being lazy/ignorant/dumb?

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  • LAMP server has gone down a few times. Ideas for server optimization?

    - by MattB
    Hi all, Our production web server has gone down a few times over the course of the last half year. In the end, we've needed to contact the web host and have them restart as I'm unable to even SSH in. This appears to only affect the web server and not the MySQL database server which is separate. When it affects the web server, all hosted websites time out. I'd like to examine web server optimization/corrections to get to the root of this issue. Any recommendations on how to proceed with that? I'm sure log files would play a role. I'm able to find my way around a Linux-based server and make needed changes, but would be interested in any tips I may not have thought of yet. It may be best for us to speak with an outside consultant as another option. Thanks.

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  • How Web Optimization Services Work to Increase Your on the Internet Reputation

    SEO is a symbol of search engine optimization and that is the key to success from the enterprise. No site has meaning if it seriously isn't properly promoted. Anytime any web surfer is in look up of any certain merchandise, providers or data he makes use of the easiest method of browsing as a result of search engine optimization and this is habit of many individuals to only search straight into 5 or six major sites for their goal. No person has time to seem directly into 100 pages of internet search engine as there is no need to have when he finds in major pages.

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