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  • Python performance: iteration and operations on nested lists

    - by J.J.
    Problem Hey folks. I'm looking for some advice on python performance. Some background on my problem: Given: A mesh of nodes of size (x,y) each with a value (0...255) starting at 0 A list of N input coordinates each at a specified location within the range (0...x, 0...y) Increment the value of the node at the input coordinate and the node's neighbors within range Z up to a maximum of 255. Neighbors beyond the mesh edge are ignored. (No wrapping) BASE CASE: A mesh of size 1024x1024 nodes, with 400 input coordinates and a range Z of 75 nodes. Processing should be O(x*y*Z*N). I expect x, y and Z to remain roughly around the values in the base case, but the number of input coordinates N could increase up to 100,000. My goal is to minimize processing time. Current results I have 2 current implementations: f1, f2 Running speed on my 2.26 GHz Intel Core 2 Duo with Python 2.6.1: f1: 2.9s f2: 1.8s f1 is the initial naive implementation: three nested for loops. f2 is replaces the inner for loop with a list comprehension. Code is included below for your perusal. Question How can I further reduce the processing time? I'd prefer sub-1.0s for the test parameters. Please, keep the recommendations to native Python. I know I can move to a third-party package such as numpy, but I'm trying to avoid any third party packages. Also, I've generated random input coordinates, and simplified the definition of the node value updates to keep our discussion simple. The specifics have to change slightly and are outside the scope of my question. thanks much! f1 is the initial naive implementation: three nested for loops. 2.9s def f1(x,y,n,z): rows = [] for i in range(x): rows.append([0 for i in xrange(y)]) for i in range(n): inputX, inputY = (int(x*random.random()), int(y*random.random())) topleft = (inputX - z, inputY - z) for i in xrange(max(0, topleft[0]), min(topleft[0]+(z*2), x)): for j in xrange(max(0, topleft[1]), min(topleft[1]+(z*2), y)): if rows[i][j] <= 255: rows[i][j] += 1 f2 is replaces the inner for loop with a list comprehension. 1.8s def f2(x,y,n,z): rows = [] for i in range(x): rows.append([0 for i in xrange(y)]) for i in range(n): inputX, inputY = (int(x*random.random()), int(y*random.random())) topleft = (inputX - z, inputY - z) for i in xrange(max(0, topleft[0]), min(topleft[0]+(z*2), x)): l = max(0, topleft[1]) r = min(topleft[1]+(z*2), y) rows[i][l:r] = [j+1 for j in rows[i][l:r] if j < 255]

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  • Is Flash/Actionscript any safer than Javascript for persistent online game?

    - by Sean Madigan
    I'm finding lately how unsecure Javascript is when programming a game (I'm trying to do a turn based RPG and currently the battle calculations are done through Javascript which any player can cheat with of course giving themselves as much XP as they want), so I'm wondering if I were to move my battle screen to flash if this would be any more secure, or is there just as easy of a way to cheat this?

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  • Hidden features of Python

    - by jelovirt
    What are the lesser-known but useful features of the Python programming language? Try to limit answers to Python core One feature per answer Give an example and short description of the feature, not just a link to documentation Label the feature using bold title as the first line This question is along the lines of : Hidden Features of JavaScript Hidden Features of CSS Hidden Features of C# Hidden Features of VB.Net Hidden Features of Java Hidden Features of ASP.NET Hidden Features of Python Hidden Features of TextPad Hidden Features of Eclipse Hidden Features of JavaScript

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  • Problem solving-pascal

    - by lancelot-clair
    Salutations, Need some help writing this; a pseudocode that accepts as input the name and sections(160, 220, 280, 350, 425) of a masquerader, continue to run until a blank name is input. After that, pseudocode should process the amount the masquerader pay.Then pseudocode code output masqueraders name and amount to pay. Then use programming language Pascal to write this. Thanks, appreciate your response.

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  • Get 2 recoeds from PLSQL Cursor

    - by Hany
    Hi Guys... my Question is short, I create a cursor to get some values from my table I want to get the current record of cursor (the fetched record) and the next record from the cursor without fetching it, cause I want to make a calculation over the current record and the next record. in traditional Programming it's a simple operation you can do it with for index by increasing it by 1. do you have any suggestion :) thx

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  • Converting from RGB to HSL with Objective C

    - by treeba
    I'm quite new to objective c but have been programming for a while. I started creating a function that would convert from RGB to HSL and back again but I get a feeling it is way too long and headed in the wrong direction. Does anyone know of a simple way to perform this conversion?

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  • c++ FFT Beat detection library?

    - by mokaschitta
    Hi, I am currently looking around for a good allround beat detection library / source code in C++ since I found it really hard to achieve satisfying results with the beat detection code I wrote myself using this tutorial: http://www.gamedev.net/reference/programming/features/beatdetection/ It's especially really hard if you want to make it work with any kind of music so I was wondering if there is something usable out there allready? Thanks!

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  • UIImage color changing?

    - by senthilmuthu
    hi, how can i change the UIImage's Color through Programming,any help pls?if i send UIImage, its color must be changed ..any help please? if i change rgb color like the following through bitmaphandling it did not work.i have given blackcolor's RGB value like 0,0,0.....

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  • How to extent activrerecord,just make id to id.to_i

    - by qichunren
    module ActiveRecord module Mixin alias old_id id def id old_id.to_i end def hello "hellooooooooooooo" end end end ActiveRecord::Base.send :include, ActiveRecord::Mixin I make is because: id column in oracle is number type,not number(10), @user.id return 123.0,not 123,so I would like to do it by extend ar. But my way above does not work for me,it still show number with dot zero,123.0. How to make id auto invove id.to_i???

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  • webserver horrible slow, sometimes incredible fast

    - by dhanke
    i am running a small community ( 6000+ Members ) on a non-virtual 64-bit ubuntu 11.04 system. I am not a Linux-pro, not even advanced, i just tried to setup a webserver, which does nothing special actually. Delivering some dynamic PHP and RoR websites is its task. So it might be that my configuration files do look horrible bad. Also, i might use the wrong vocabulary, so in doubt, please ask. Having a current all-time record of 520 registered users (board-accounts, no system-users) online at same time, average server-load is about 2.0 - 5.0. Meantime (~250 users) average server load value is at about 0.4 - 0.8, sometimes, on some expensive searches a bit higher. everything fine. From time to time however, the load increases up to 120 (120.0, not 12.0 ;) ). In this time, its hard to even connect via SSH, but when i reach the server, and use top/htop/iotop to see whats happening, i cannot identify any process causing high CPU load. iotop tells me about a current reading/writing speed of about approx. 70kb/s, which is quite equal to power-off i think. Memory-Usage is max. at ~ 12GB of 16GB, so swap remains empty. now the odd (at least for me:) waiting some minutes ( since i always get a bit into a panic when this happens, it feels like 5 minutes, but i suppose its more like 20-30 minutes) and the server is back to normal. everything continues as normal. another odd fact: when i run hdparm -tT /dev/sda, i get answer like: /dev/sda: Timing cached reads: 7180 MB in 2.00 seconds = 3591.13 MB/sec Timing buffered disk reads: 348 MB in 3.02 seconds = 115.41 MB/sec when i run the same command while the server is "frozen", the answer is like /dev/sda: <- takes about 5 minutes until this line appears Timing cached reads: 7180 MB in 2.00 seconds = 3591.13 MB/sec <- 5 more minutes Timing buffered disk reads: 348 MB in 3.02 seconds = 115.41 MB/sec <- another 5 minutes so the values are the same, but the quoted time is completely wrong. using time command as prefix also tells me that ~ 15 minutes were used. I searched in dmesg, /var/log/[messages|syslog] - nothing found. /var/log/errors however tells me that: Jul 4 20:28:30 localhost kernel: [19080.671415] INFO: task php5-fpm:27728 blocked for more than 120 seconds. Jul 4 20:28:30 localhost kernel: [19080.671419] "echo 0 /proc/sys/kernel/hung_task_timeout_secs" disables this message. multiple times. now that message does tell me that php5-fpm task was blocked or did block ? - but not if that is the cause or just one of the results of that "freeze". Anyone? to cut the long story short, i dont know where even to start analyzing. So if you can give me any advice by looking at following specs and configs, or ask me to provide more information, i`d be glad. Specs: 6 Core AMD Phenom(tm) II X6 1055T Processor * 16 Gigabyte Ram 2x 1.5 TB Seagate ST1500DL003-9VT16L via SATA 3 via SoftwareRaid (i suppose) Services: (due to service --status-all, those with [ + ]) nginx Webserver 1.0.14 mySQL 5.1.63 Server Ruby on Rails 2.3.11 ( passenger-nginx-module ) php5-fpm 5.3.6-13ubuntu3.7 SSH ido2db Further services: default crontab + nightly backup. syslog-ng Website consists of 2 subdomains, forum. and www. where forum is a phpBB3.x PHP-Board, and www a Ruby on Rails 2.3.11 application (portal). Mini-Note: sometimes i notice that the forum is pretty slow, in contrast to the always-fast (except for this "freeze") portal. Both share the same Database, but the portal is using it read-only. The Webserver is nginx, using phusion passenger module to communicate with the ruby-application. Also, for the forum it communicates with php5-fpm via socket: relevant nginx configuration parts ( with comments/questions starting by ; ) ; in case of freeze due to too high Filesystem activity, maybe adding a limit? #worker_rlimit_nofile 50000; user www-data; ; 6 cores, so i read 6 fits. maybe already wrong? worker_processes 6; pid /var/run/nginx.pid; events { worker_connections 1024; } http { passenger_root /var/lib/gems/1.8/gems/passenger-3.0.11; passenger_ruby /usr/bin/ruby1.8; ; the forum once featured a chat, which was working w/o websockets. ; so it was a hell of pull requests (deactivated now, freeze still happening) keepalive_timeout 65; keepalive_requests 50; gzip on; server { listen 80; server_name www.domain.tld; root /var/www/domain/rails/public; passenger_enabled on; } server { listen 80; server_name forum.domain.tld; location / { root /var/www/domain/forum; index index.php; } ; satic stuff to be handled by nginx location ~* ^/style/.+.(jpg|jpeg|gif|css|png|js|ico|xml)$ { access_log off; expires 30d; root /var/www/domain/forum/; } ; now the php magic, note the "backend"-fcgi_pass location ~ .php$ { fastcgi_split_path_info ^(.+\.php)(.*)$; fastcgi_pass backend; fastcgi_index index.php; fastcgi_param SCRIPT_FILENAME /var/www/domain/forum$fastcgi_script_name; include fastcgi_params; fastcgi_param QUERY_STRING $query_string; fastcgi_param REQUEST_METHOD $request_method; fastcgi_param CONTENT_TYPE $content_type; fastcgi_param CONTENT_LENGTH $content_length; fastcgi_intercept_errors on; fastcgi_ignore_client_abort off; fastcgi_connect_timeout 60; fastcgi_send_timeout 180; fastcgi_read_timeout 180; fastcgi_buffer_size 128k; fastcgi_buffers 256 16k; fastcgi_busy_buffers_size 256k; fastcgi_temp_file_write_size 256k; fastcgi_max_temp_file_size 0; } location ~ /\.ht { deny all; } } ;the php5-fpm socket. i read that /dev/shm/ whould be the fastes place for this. bad idea in general? upstream backend { server unix:/dev/shm/phpfpm; } ... } php5-fpm settings (i changed this values due to php5-fpm error log messages higher and higher.. (freeze-problem was there before as well)* listen = /dev/shm/phpfpm user = www-data group = www-data pm = dynamic ; holy, 4000! well, shinking this value to earth-level gave me ; 100s of 502 bad gateway commands. this values were quite stable. ; since there are only max 520 users online i dont get it, why i would need ; as many children as configured here. due to keep-alive maybe? ; asking questions is easier for me since restarting server will make ; my community-members angry ;) pm.max_children = 4000 pm.start_servers = 100 pm.min_spare_servers = 50 pm.max_spare_servers = 150 pm.max_requests = 10 pm.status_path = /status ping.path = /ping ping.response = pong slowlog = log/$pool.log.slow ;should i use rlimit? ;rlimit_files = 1024 chdir = / mysql/my.cnf [client] port = 3306 socket = /var/run/mysqld/mysqld.sock [mysqld_safe] socket = /var/run/mysqld/mysqld.sock nice = 0 [mysqld] user = mysql socket = /var/run/mysqld/mysqld.sock port = 3306 basedir = /usr datadir = /var/lib/mysql tmpdir = /tmp skip-external-locking bind-address = 127.0.0.1 key_buffer = 16M max_allowed_packet = 16M thread_stack = 192K thread_cache_size = 8 myisam-recover = BACKUP ; high number, but less gives some phpBB errors. max_connections = 450 table_cache = 512 ; i read twice the cpu cores, bad? thread_concurrency = 12 join_buffer_size = 2084K concurrent_insert = 3 query_cache_limit = 64M query_cache_size = 512M query_cache_type = 1 log_error = /var/log/mysql/error.log log_slow_queries = /var/log/mysql/mysql-slow.log long_query_time = 2 expire_logs_days = 10 max_binlog_size = 100M low_priority_updates=1 [mysqldump] quick quote-names max_allowed_packet = 16M [isamchk] key_buffer = 16M !includedir /etc/mysql/conf.d/ I used smartctl already, hdds seem to be fine. /proc/mdstatus quotes: Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] md3 : active raid1 sda3[1] 1459264192 blocks [2/1] [_U] md1 : active raid1 sda1[0] 3911680 blocks [2/1] [U_] unused devices: ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 127727 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) 127727 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited I quote some questions in my configuration files, these are not (intentional) directly problem-related, but would be nice for me to know wether they are indeed questionable or done right. One additional Fact: my MYSQL-database is at 12GB size. i dont know if that does matter, but mytop sometimes shows me 4-5 seconds long insert queries, some are 20-30 seconds long. Its just a feeling that i am unable to prove (because i dont know how), but when i disable the database, the freeze seems not to happen. Example: i created a dummy rails application to see the development log. the app made some sql-queries, reads and inserts. the log quite often was like: DbTest Load (0.3ms) SELECT * FROM `db_test` WHERE (`db_test`.`id` = 31722) LIMIT 1 SQL (0.1ms) BEGIN DbTest Update (0.3ms) UPDATE `db_test` SET `updated_at` = '2012-07-04 23:32:34' WHERE `id` = 31722 - now the log stands still for 5-60 seconds. SQL (49.1ms) COMMIT - SQL-Update time in the log does not include freeze time Rendering test/index Completed in 96ms (View: 16, DB: 59) | 200 OK [http://localhost:9000/test] Bad part is: this mini-freeze here only happens from time to time as well. note: meanwhile i cannot even upload files via scp. I currently feel like running form bad to worse and back by googling for my server-problem due to immense lack of knowledge regarding server configurations. It still makes me wonder, why those problems even appear, since 250 users a time is not such a high amount, right? So my questions: whats wrong and how to fix? ;) or: what information can i provide to make the situation more clear? can you point at some critical bad configuration-line which i should consider to catch up in the documentation? are there any tools i can run to see some possible bottlenecks? any further advice? (next to: "pay someone who knows what he does" - its a private project, server costs enough already. :)) Thanks for your time and help. Best Regards, Daniel P.S.: i renamed the configfiles to domain.tld since i dont want to have any % more load to the server until its fixed. might be a exaggeratedly thought.. P.P.S: if i asked a complete duplicate question, sorry. my search results seemed to be quite specific in their own way.

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  • What is the best way to set a database entry so that it expires after n hours using Ruby/Rails?

    - by marcgg
    My app has a token model as such: class Token < ActiveRecord::Base # The model include a few attributes including created_at end I want entries linked to this model to expire after 6 hours, meaning that they should get automatically deleted. I know that I could set a cronjob or something similar to do this, but isn't there a better/simpler way? Note: I'm using Rails 3.0.0beta3, mysql (in dev) and postgres (in prod)

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  • Constructor overloading in Java - best practice

    - by errr
    There are a few topics similar to this, but I couldn't find one with a sufficient answer. I would like to know what is the best practice for constructor overloading in Java. I already have my own thoughts on the subject, but I'd like to hear more advice. I'm referring to both constructor overloading in a simple class and constructor overloading while inheriting an already overloaded class (meaning the base class has overloaded constructors). Thanks :)

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  • A good web data extraction/screen scraper program?

    - by Taylor
    I need to capture product data from a site on a regular basis and wondered if any one knows of a good software program? I've trialed Mozenda but its a monthly subscription and pricey in the long term. Obviously something thats free would be best but I don't mind paying either. Just need a decent program thats reliable and doesn't require much programming knowledge.

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  • how do I use fitnesse ActionFixture with C#?

    - by JDPeckham
    I tried to make an action fixture and it’s not working. (c# with Slim runner) Basically it seems like it's trying to interpret it as a column fixture. |!-Fitnesse.BuyActions-! | |Start|!-Fitnesse.BuyActions-!| |check|total |0.0 | |enter|price |12.00 | |press|buy | |check|total |12.00 | |enter|price |100.00 | |press|buy | |check|total |112.00 | Fitnesse.BuyActions Start Fitnesse.BuyActions check Method setStart not found in Fitnesse.BuyActions using fit; namespace Fitnesse { public class BuyActions : ActionFixture { public BuyActions() : base() { this.targetObject = this; } } }

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  • return distinct records using subsonic 3 query and VB

    - by HR
    I have been having issues trying to return distinct records from a subsonic3 query using VB. My base query looks like so: Dim q As New [Select]("Region") q.From("StoreLocation") q.Where("State").IsEqualTo(ddlState.SelectedValue) q.OrderAsc("Region") This returns duplicates. How can I add a distinct clause in this to return distinct records? I have been trying to place around with Contraints, but to no avail. Thanks in advance HR

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  • Free Web UI design software

    - by Pich
    Does anybody know of any free Web UI design software? EDIT: I am looking for a UI mockup tool (that is freeware) to create stuff like this: http://blogs.atlassian.com/jira/Mockups%20UI.jpg I works a developer with the task to design the UI of an application. I want to draw some examples of how the webpages can look and show it to the requirements team.

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  • Rijndael encryption from Action Script to C#

    - by Coppermill
    I am trying to share encryption between Action Script and C# My task is to decrypt the following message within C# f1ca22a365ba54c005c3eb599d84b19c354d26dcf475ab4be775b991ac97884791017b12471000def05bb77bfe9c3a97d44ef78c9449f12daf6e25b61ab1a281 It uses Rijndael encyption , ECB mode (electronic code book), Key: Pas5pr@se , 128 bit key size and block size. The problem I have is I can't seem to do it, anyone help me on this?

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  • Using C# and Repository Factory and the error: The requested database is not defined in configurati

    - by odiseh
    hi I am using Repository factory for visual studio 2008 for a personal project. It generated a class called ProductRepository which inherits from Repository. The ProductRepository has a constructor which gets a database name as string and passes it to its base (I mean Repository ). So when I try to debug my project step by step, I pass my database name to ProductRepository but it raises the following error: The requested database is not defined in configuration. What's wrong?

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  • Static methods and their overriding

    - by abson
    Java doesn't allow overriding of static methods but, class stat13 { static void show() { System.out.println("Static in base"); } public static void main(String[] ar) { new next().show(); } } class next extends stat13 { static void show() { System.out.println("Static in derived"); } } is not overriding done here?

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  • Can one instance of a WCF service pass work on to another instance where this 2nd instance would rep

    - by Matt
    Let's say I have 2 instances of the same web services. Is there a way that I can have the second instance of the web service perform a task at the behest of the first instance of the WCF service and reply directly to the original requester? I could code this and include logic in WCF-A to contact WCF-B under the right conditions and then passback the result, but returning to the requester directly from WCF-B would be easier. Also, I made a handy dandy chart.

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  • XCode linking error when targeting armv7.

    - by Tom
    I've already spent countless hours puzzling over this, utilizing Google searches and other Stack Overflow questions to no avail. I have an iPhone/iPad universal application, which seems to compile fine when the target is armv6. However, when the device is iPad, I get this warning: warning: building for SDK 'Device - iPhone OS 3.2' requires an armv7 architecture. Oddly enough, the app still runs great on iPad in spite of this warning. However, I do want to do things the "right way" what ever that means in this case. When I switch the target architecture to armv7, I get linking errors: "___restore_vfp_d8_d15_regs", referenced from: *redacted* "___save_vfp_d8_d15_regs", referenced from: *redacted* ld: symbol(s) not found collect2: ld returned 1 exit status The "redacted" portions of the errors are references to the static library to which I'm trying to link. Here's what I've tried from the many suggestions online. Each of these were suggested more than once without any explanation, which leads me to believe nobody quite understands this problem: "Never use the drop down menu in the upper left of the XCode window to choose the target. Instead, set this to Base SDK and then the Base SDK to iPhone OS 3.0 in the target configuration. Set the target device to your preferred target (iPad, iPhone OS 3.2 in my situation.)" This yields the error "Library not found for -lcrt1.3.1.o" "Make sure that GCC isn't linking against the wrong version of the standard library. (You'll have to make sure the LIBRARY_SEARCH_PATH doesn't have the wrong path in it.)" My LIBRARY_SEARCH_PATH is already empty, so this doesn't seem relevant. "Try compiling with GCC 4.0 rather than GCC 4.2." I get a syntax error inside a UIKit header file. The error is "Syntax error before 'AT_NAME' token." The line is "UIKIT_EXTERN @interface UILocalizedIndexedCollation : NSObject." Another project compiles just fine with the same target settings, which is really making me question my sanity. Could I be dealing with a corrupt XCode project? If anyone knows what's actually happening and has a reference or doesn't mind explaining it, I would be so very grateful. Cheers!

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