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• Why change net.inet.tcp.tcbhashsize in FreeBSD?

  - by sh-beta

  In virtually every FreeBSD network tuning document I can find: # /boot/loader.conf net.inet.tcp.tcbhashsize=4096 This is usually paired with some unhelpful statement like "TCP control-block hash table tuning" or "Set this to a reasonable value." man 4 tcp isn't much help either: tcbhashsize Size of the TCP control-block hash table (read-only). This may be tuned using the kernel option TCBHASHSIZE or by setting net.inet.tcp.tcbhashsize in the loader(8). The only document I can find that touches on this mysterious thing is the Protocol Control Block Lookup subsection beneath Transport Layer in Optimizing the FreeBSD IP and TCP Stack, but its description is more about potential bottlenecks in using it. It seems tied to matching new TCP segments to their listening sockets, but I'm not sure how. What exactly is the TCP Control Block used for? Why would you want to set its hash size to 4096 or any other particular number?

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• How to set specific environment variables for Apache service run on Windows

  - by Jimm Chen

  I'm facing a problem. I use xampp 1.7.7 on Windows which installs a Apache service. I find that I have to some tweak to have all PHP modules load properly. For example, php_ldap.dll cannot be loaded. It is mysterious why it cannot be loaded until I tried to run httpd.exe from command line, which reveals that libsasl.dll cannot be founded. Actually, there exist D:\xampp\php\libsasl.dll but httpd.exe cannot find it. OK. The best way is to add D:\xampp\php to PATH env-var. Now my question is: How do I set a specific PATH value for that specific Apache service but not system wide. -- because I think it is better not to disturb other processes with that extra PATH value. Is there a general way to do that for a specific Windows service? or, is there a Apache specific way to load extra env-var settings from some specific configuration files?

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• Reserve one http slot for /server-status?

  - by Stefan Lasiewski

  I have an Apache server which is hanging for some reason. When I normally want to check on the load of an Apache server, I tend to use mod_status via the URL at http://webserver1.example.org/server-status or from the commandline like service httpd fullstatus. However today, the Server is refusing all new connections. Some mysterious problem is causing connections to stall, which means that number of connections fills up all available connections (e.g. The number of connects exceeds the MaxClients setting), and therefore neither http://webserver1.example.org/server-status nor service httpd fullstatus can return anything. Is it possible to configure Apache to reserve one or two slots for the mod_status pages?

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• FeedValidator & Feedburner get 404 when accessing wordpress RSS feeds when permalinks are enabled.

  - by Wazbaur

  I'm helping a friend set up a self-hosted Wordpress blog + feedburner and I'm seeing a problem with the feeds that I'm finding somewhat mysterious. Using the default permalink structure (e.g., ?p=123) everything works as expected; I can follow the feed in Google reader, navigate to it manually, and set it up in feedburner. However, once I switch away from the default permalink structure, feedburner and feedvalidator both report that accessing the feed is returning HTTP-404 and Google reader no longer shows new posts (I'm assuming for the same reason), but I can navigate to the feed using a browser. When I do that it appears as though nothing is wrong; there is a feed there and it contains all the posts I expect it to have. I've re-started the feedburner & reader set-up from the beginning after changing the link structure, so I don't think they're doing anything silly like looking at the feed at its old address. I've seen people with similar problems in various other places but there doesn't seem to be a good answer anywhere.

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• Window will read this particular DVD which it usually doesn't, if it spins for a longer time

  - by curious_kid

  I'm unable to figure out what's wrong with my system. My computer will read this particular DVD sometimes and mostly it won't. When trying to explore the DVD, I get error "Windows can't access this disc" ( note : It doesn't says that the "disc is empty", the normal error which I generally get when I try to read a scratched DVD ). Ok now the mysterious part, I have noticed that everytime DVD spins for a longer time ( like for 1 -2 minutes), window will read it without any problem. Extra information : The DVD I'm talking about doesn't have any scratches. I tried cleaning the DVD Drive with a lens cleaning CD. DVD was burned in multisessions. My system have window 8 installed. Question I wanted to ask : What makes DVD spins for a longer period of time sometimes ? If possible how can I make window spin the DVD for longer time ? Any solution to my problem ?

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• one of my web hostings is down - only for me - why ?

  - by Thomas Traub

  My first post here, I am reading / learning a lot, thanks ;). I've got a mysterious issue (for me) and would really appreciate to get it solved. I've rent a reseller package with bibihost.com and it's now the second time that all my domaines the hoster's site are unavailable from my connection (my Mac and my iPhone), (in browser, per FTP, ping, ab, and traceroute) This has never before happened to me with other web addresses. traceroute get's always stuck at a specific server 40g.vss-1-6k.routers.chtix.eu (91.121.131.29) The sites are all up for everyone else, I've checked with downforeveryoneorjustme.com, a homegrown script loaded to another server and montastic.com My question(s) : Why am I blocked ? Is there anything I can do about it ? If I cannot solve this issue I have to change the hoster, but I really would like to know what's going on. my domaines on this server : tienstiens.fr tomlegrand.com

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• Fresh Vista install and the strange appearance of boxes/rectangles

  - by Nick

  I purchased a new hard-drive, and after doing a fresh install of Vista and installing all updates/latest drivers, I'm noticing that all of a sudden and shortly after being powered on, I get black boxes/rectangles all over my screen (below). Any ideas as to what could be causing this? On a (maybe) related note, my brand new hard-drive is squeaking. Not often, but it is there. Debating on whether or not it is worth the hassle of sending it back, or if this is related to the mysterious rectangles.

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• Monitoring/logging a malfunctioning internet connection

  - by Pekka

  I have a mysterious internet connection problem: Every 15-20 minutes, the connection will become very slow, and take 2-3 minutes for anything to load. I've had a technician from the ISP over here to test the hardware, and everything is in pristine condition. They have no other explanation than a configuration error on my machine, a possibility I can exclude 90% because I'm experiencing the same problems with another machine. I will have to monitor the situation now, and I would like to run a program that logs when internet connections become slow. I thought about putting something together using at and wget. Does anybody know of some other tool for this that does this out of the box - maybe something with an adjustable request frequency, logging connection speeds etc.?

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• Keyboard that can't be removed (W8 CP)

  - by torazaburo

  Somehow I ended up with four keyboards installed (English (United States), Japanese (Japan), Kannada, and Hindi. They are installed in the sense that the tray drop down displays these four, and when I ALT-SHIFT through my keyboards it cycles through them. The mysterious thing is that in the Languages Control Panel, only the first two are shown, so I am stuck as to how to remove the last two. In the past, I may have installed and removed the Kannada and Hindi keyboards. What I did recently was to install the English (India) keyboard, as a way to get the ability to input the rupee symbol with ALT-CTRL-4. That English (India) keyboard did show up in the Languages Control Panel and allow itself to be removed. It almost seems like installing that keyboard somehow activate hidden registry settings left over from back when I had Kannada and Hindi installed. In any case, any ideas about how to remove these keyboards which don't appear in the Language Control Panel?

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• puppet rspec no such file to load -- rspec-puppet (LoadError)

  - by Vorsprung

  I have no prior experience at all of ruby. I am not interested in ruby (and so have no knowledge of rails etc) as such but am using puppet to manage a group of servers. I have written some modules and the rspec-puppet system looks like it would be very useful. However, I cannot get rspec-puppet to work I am using Ubuntu LTS 10.04 I have installed puppet rspec using the directions on their web page What I actually did apt-get install rubygems # (installs 1.8) gem install rspec-expectations gem install rspec-puppet I also installed librspec-ruby1.8 Then I ran rspec-puppet-init in a puppet module directory I'd already made (it's a working puppet module) I made a file as defined in the tutorial $ more spec/defines/rule_spec.rb require 'spec_helper' describe 'vanusers::rule' do let(:title) { 't1' } it { should contain_class('vanusers::JamieA') } end but when I try and run it there is a mysterious dependancy issue $ spec spec/defines/rule_spec.rb /home/jamie/git/puppet/modules/vanusers/spec/spec_helper.rb:1:in `require': no such file to load -- rspec-puppet (LoadError) from /home/jamie/git/puppet/modules/vanusers/spec/spec_helper.rb:1 from ./spec/defines/rule_spec.rb:1:in `require' from ./spec/defines/rule_spec.rb:1 from /usr/lib/ruby/1.8/spec/runner/example_group_runner.rb:15:in `load' from /usr/lib/ruby/1.8/spec/runner/example_group_runner.rb:15:in `load_files' from /usr/lib/ruby/1.8/spec/runner/example_group_runner.rb:14:in `each' from /usr/lib/ruby/1.8/spec/runner/example_group_runner.rb:14:in `load_files' from /usr/lib/ruby/1.8/spec/runner/options.rb:132:in `run_examples' from /usr/lib/ruby/1.8/spec/runner/command_line.rb:9:in `run' from /usr/bin/spec:3 Here is the solution I came up with in the end:: apt-get install rubygems gem install rspec-expectations rspec-puppet puppet-lint puppetlabs_spec_helper so your path picks up the gem stuff export PATH=/var/lib/gems/1.8/bin:$PATH cd into module and rm spec/spec_helper.rb rspec-puppet-init replace Rakefile with require 'rake' require 'rspec/core/rake_task' require 'puppetlabs_spec_helper/rake_tasks' Then "rake spec" to run tests or "rake lint" to check files http://sysadvent.blogspot.co.uk/2013/12/day-22-getting-started-testing-your.html was an excellent source of info

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• Ubuntu CPU Fan at 2200 RPM and CPU top at 90°C

  - by T-Erra

  I have a problem with my CPU heat. I'm running Ubuntu 14.04 (64bit) and I have issues with the cooling. I know it might be a hardware issue, but I've checked, the fan is running and in my GUI I use the command "sensors" which shows me a RPM of 2200 and a CPU temperature of 60°C while I'm not running any software. This seems to be really mysterious. However, if I start my IDE (Eclipse), Firefox and Chromium at the same time, the CPU temp goes up to 75-90° Celsius. I doubt that this is common for a system with 16 GB RAM, an i7 Processor and an Intel water cooling system and I also never had some issues like this before when I was running Ubuntu 12.04 or 13.04. Fan Speed At 60°C it's at 1300 RPM, and after start up Eclipse and Firefox it's at approximately 2200 RPM and between 75°C - 90°C depending on how many windows and IDE's I've opened. If I use the "top" command, there are just few processes like Xorg or Compiz which are taking up to 10% CPU usage at maximum, during the time I'm not running any software. I have tried to upgrade the Linux kernel, where I failed. After upgrading, I wasn't able to boot anymore so I tried to remove the new kernel from the boot directory and updated my grub file to an old entry, which works fine now, but still with the temperature issue. My NVIDIA drivers is also up to date, which dropped some issues I had before with the CPU load. So it can't be a problem with the graphic card. How can I find out, where the problem is, or why my CPU gets that high temperatures, which I only should get while playing games with high end graphics and so on? Did anyone have some similar issues before?

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• Red Sand – An Awesome Fan Made Mass Effect Prequel [Short Movie]

  - by Asian Angel

  Welcome to Mars where humanity has just discovered the Prothean Ruins and Element Zero, but danger abounds as the Red Sand terrorist group seeks to claim Mars for themselves! If you love the Mass Effect game series, then you will definitely want to watch this awesome fan made prequel set 35 years before the events of the first game. Synopsis From YouTube: Serving as a prequel to the MASS EFFECT game series,”Red Sand” is set 35 years before the time of Commander Shepard and tells the story of the discovery of ancient ruins on Mars. Left behind by the mysterious alien race known as the Protheans, the ruins are a treasure trove of advanced technology and the powerful Element Zero, an energy source beyond humanity’s wildest dreams. As the Alliance research team led by Dr. Averroes (Ayman Samman) seeks to unlock the secrets of the ruins, a band of marauders living in the deserts of Mars wants the ruins for themselves. Addicted to refined Element Zero in the form of a narcotic nicknamed “Red Sand” which gives them telekinetic “biotic” powers, these desert-dwelling terrorists will stop at nothing to control the ruins and the rich vein of Element Zero at its core. Standing between them and their goal are Colonel Jon Grissom (Mark Meer), Colonel Lily Sandhurst (Amy Searcy), and a team of Alliance soldiers tasked with defending the ruins at all costs. At stake – the future of humanity’s exploration of the galaxy, and the set up for the MASS EFFECT storyline loved by millions of gamers worldwide. RED SAND: a Mass Effect fan film – starring MARK MEER [via Geeks are Sexy] 7 Ways To Free Up Hard Disk Space On Windows HTG Explains: How System Restore Works in Windows HTG Explains: How Antivirus Software Works

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• [MINI HOW-TO] Remove the Search Helper Extension from Firefox

  - by Asian Angel

  If you found a new surprise extension added to Firefox after the June Patch from Microsoft, then you are likely to be rather unhappy right now. Join us as we show you how to remove the Search Helper extension from your browser. An Unexpected Addition to Your Extensions You may be wondering what the new mysterious extension that showed up is for. Its’ purpose is to help the Bing Toolbar better integrate with your browser. Unless you have the Bing Toolbar installed you really do not need this cluttering your browser up. So how do you get rid of it? Removing the Extension In order to remove the extension you will need to navigate to the following location: C:\Program Files\Microsoft\Search Enhancement Pack\Search Helper Once there delete the “firefoxextension folder”…that is all there is to it. If you want to remove the search helper add-on for Internet Explorer then delete the “SEPsearchhelperie.dll file” while you are here. Note: You may need to have administrator rights in order to delete the folder. No more Search Helper Extension! If you are unhappy about this update being snuck into your system, following these instructions will remove it. Microsoft Support Page About Update KB982217 Similar Articles Productive Geek Tips Remove the New Tab Button in FirefoxAdd Search Forms to the Firefox Search BarAdd Notes to Zoho Notebook in FirefoxOrganize Your Firefox Search Engines Into FoldersManually Remove Skype Extension from Firefox TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips HippoRemote Pro 2.2 Xobni Plus for Outlook All My Movies 5.9 CloudBerry Online Backup 1.5 for Windows Home Server Steve Jobs’ iPhone 4 Keynote Video Watch World Cup Online On These Sites Speed Up Windows With ReadyBoost Awesome World Cup Soccer Calendar Nice Websites To Watch TV Shows Online 24 Million Sites

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• Permission denied on /dev/xvdf despite sudo?

  - by Sid

  I'm trying to get a stream off port 9999 and write to /dev/xvdf. I'm using Amazon EC2 with the Ubuntu 11.10 server image. By default I log in as 'ubuntu' which has sudo privileges. However, when I run the following netcat command, I get this error ubuntu@ip-10-252-35-122:~$ ls -al /dev/xv* brw-rw---- 1 root disk 202, 1 2011-11-30 22:22 /dev/xvda1 brw-rw---- 1 root disk 202, 80 2011-11-30 22:27 /dev/xvdf ubuntu@ip-10-252-35-122:~$ sudo netcat -p 9999 -l > /dev/xvdf bash: /dev/xvdf: Permission denied ubuntu@ip-10-252-35-122:~$ Any idea why I get the permission denied error and how I can work around it? Update: Something mysterious is running in the background that resets the permissions? Check the snippet below and the permission flags seem to automatically reset when I try using /dev/xvdf !?! ubuntu@ip-10-252-35-122:~$ sudo chmod 777 /dev/xvdf ubuntu@ip-10-252-35-122:~$ ls -al /dev/xvdf brwxrwxrwx 1 root disk 202, 80 2011-11-30 22:43 /dev/xvdf ubuntu@ip-10-252-35-122:~$ sudo nc -p 9999 -l > /dev/xvdf This is nc from the netcat-openbsd package. An alternative nc is available in the netcat-traditional package. usage: nc [-46DdhklnrStUuvzC] [-i interval] [-P proxy_username] [-p source_port] [-s source_ip_address] [-T ToS] [-w timeout] [-X proxy_protocol] [-x proxy_address[:port]] [hostname] [port[s]] ubuntu@ip-10-252-35-122:~$ ls -al /dev/xvdf brw-rw---- 1 root disk 202, 80 2011-11-30 22:43 /dev/xvdf ubuntu@ip-10-252-35-122:~$ I'm using stock Ubuntu Amazon EC2 images from http://alestic.com/ (links to images at the top)

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• /etc/resolv.conf nameserver fd00::1

  - by user88631

  My /etc/resolv.conf constantly get a mysterious entry, i run a home network with ipv6 provided by ravd, the interface is auto-configured by Network manager (all name server lookups are lost when this line is first in my /etc/resolv.conf) . Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) **# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN** nameserver fd00::1 nameserver 192.168.1.1 search home.int When ping is working cat /etc/resolv.conf # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN nameserver 192.168.1.1 search home.int So something is putting fd00::1 at start of file, not if I ping6 fd00::1 I get Destination unreachable: Administratively prohibited To diagnose this I ran the router with single cable to connected to ubuntu machine. Ran tcpdump + restarted network on ubuntu. "tcpdump ip6 -e -i eth0 | grep fd00" finds nothing, it's not being advertised via the network.. The only hit I got was when an upstream router refused a connection attempt from the ubuntu machine to fd00::1. I have also switched on debug for network manager & it appears to set the mystery line.. 15:22:14 storage-pc NetworkManager[349]: <info> Activation (eth0) Stage 5 of 5 (IPv4 Commit) complete. 15:22:14 storage-pc NetworkManager[349]: <warn> dnsmasq exited with error: Other problem (5) 15:22:14 storage-pc NetworkManager[349]: <debug> [1346822534.281528] [nm-dns-manager.c:598] update_dns(): updating resolv.conf 15:22:14 storage-pc NetworkManager[349]: <debug> [1346822534.281875] [nm-dns-manager.c:719] update_dns(): DNS: plugin dnsmasq ignored (caching disabled) 15:22:14 storage-pc NetworkManager[349]: <info> ((null)): writing resolv.conf to /sbin/resolvconf 15:22:14 storage-pc dbus[2184]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher' 15:22:14 storage-pc dnsmasq[2875]: reading /etc/resolv.conf 15:22:14 storage-pc dnsmasq[2875]: using nameserver 192.168.1.1#53 15:22:14 storage-pc dnsmasq[2875]: using nameserver fd00::1#53 Any suggestions on how to find out where this comes from?

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• How do I create my own programming language and a compiler for it

  - by Dave

  I am thorough with programming and have come across languages including BASIC, FORTRAN, COBOL, LISP, LOGO, Java, C++, C, MATLAB, Mathematica, Python, Ruby, Perl, JavaScript, Assembly and so on. I can't understand how people create programming languages and devise compilers for it. I also couldn't understand how people create OS like Windows, Mac, UNIX, DOS and so on. The other thing that is mysterious to me is how people create libraries like OpenGL, OpenCL, OpenCV, Cocoa, MFC and so on. The last thing I am unable to figure out is how scientists devise an assembly language and an assembler for a microprocessor. I would really like to learn all of these stuff and I am 15 years old. I always wanted to be a computer scientist someone like Babbage, Turing, Shannon, or Dennis Ritchie. I have already read Aho's Compiler Design and Tanenbaum's OS concepts book and they all only discuss concepts and code in a high level. They don't go into the details and nuances and how to devise a compiler or operating system. I want a concrete understanding so that I can create one myself and not just an understanding of what a thread, semaphore, process, or parsing is. I asked my brother about all this. He is a SB student in EECS at MIT and hasn't got a clue of how to actually create all these stuff in the real world. All he knows is just an understanding of Compiler Design and OS concepts like the ones that you guys have mentioned (i.e. like Thread, Synchronization, Concurrency, memory management, Lexical Analysis, Intermediate code generation and so on)

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• OS X is based on the codex Gigas the devils bible: Android OS n 4.4 Dio Ra Egyptian deity why is that?

  - by user215250

  GUESS WHO? The Internet and all computers are based on a mathematical number system that seems to be 3, 4, 6, 8 and 10. The HTTP is 888P and UTF-8 and Windows 8 and 8 gigas of RAM(88) on a 64biTOS X-10 or Aten(satan) why is it allowed to be so evil and who all knows about it? Is this activity illegal and should I sew these companies for being involved in satanic practices? iC3 iC3 iC3 I do see XP (X) Chi and (P) Rho a monogram and symbol for Christ, consisting of the superimposed Greek letters. The X is ten, The X code, OS X(O Satan) and codex The Gigas the Devil bible and the P is Payne, The House of Payne in which God dwells. Windows 8, Google Android and Apples OS X are the foundation on which we operarte on the Internet and our Mobiles devices. What is it that these 3 companies have chosen to base their OS’s on such evil? Windows 8 is windows hate H8, HH and H8. Said to be the Devil. Google’s (UGLE) M the Masonic M behind Android OS.in 4.4 is Dio (R) DNA O Sin and 44 is the Devils name in Twain’s The Mysterious Stranger. Apple’s evil (i) OS X (ou-es-ten) O Satan them all beat (B8) considering Apple put their first product on the market for $666.66. The Holy Grail of computers they say. Your Excellency, Lord and King OS2 Eisus Uni Peg Unix: The Unicorn Pegasus Jesus Christ

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• More information about worldwide nodes how to get?

  - by Aubergine

  The context: Six hosts across worldwide were traced over week from UK. Ten thousands of lines to be parsed and analysed. And then I try to find any clue of geographical information and path - from where it jumps where. Then after Austria or Germany(each time different) I have mysterious 62.208.72.6 which in GEO LOC gives me Falklands Islands (which is where my target host is by the way, but before target host I still have 5 other nodes) Then I do whois for this 62.208.72.6 route: 62.208.0.0/16 descr: DE-ECRC-62-208-0-0 origin: AS1273 mnt-by: CW-EUROPE-GSOC source: RIPE # Filtered Why it says Europe now? How to understand this enigma code? I want to confirm more or less whether this is in europe or in falkland islands? But it can't be in FK yet as after next two hosts I get New York? Could you also tell me what does this CW-EUROPE-GSOC abbreviation means. (To preserve your sanity better not google, unless you already know it :-D) And the actual whois for the destination/target host, which completely destroys my head: route: 195.248.193.0/24 descr: HORIZON descr: Cable and Wireless Falkland Islands descr: Via Cable and Wireless Communications UK origin: AS5551 mnt-by: AS5551-MNT source: RIPE # Filtered How is it Via Cable and Wireless Communications UK if two nodes before I was in New York? Thank you guys,

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• Game Review: Monument Valley

  Once again, it was a tweet that caught my attention... and the official description on the Play Store sounds good, too. "In Monument Valley you will manipulate impossible architecture and guide a silent princess through a stunningly beautiful world. Monument Valley is a surreal exploration through fantastical architecture and impossible geometry. Guide the silent princess Ida through mysterious monuments, uncovering hidden paths, unfolding optical illusions and outsmarting the enigmatic Crow People." So, let's check it out. What an interesting puzzle game Once again, I left some review on the Play Store: "Beautiful but short distraction Woohoo, what a great story behind the game. Using optical illusions and impossible geometries in this fantastic adventure of the silent princess just puts all the pieces perfectly together. Walking the amazing paths in the various levels and solving the riddles gives some decent hours of distraction but in the end you might have the urge to do more..." I can't remember exactly when and who tweeted about the game but honestly it caught my attention based on the simplicity of the design and the aspect that it seems to be an isometric design. The game relies heavily on optical illusions in order to guide to the silent princess Ida through her illusory adventure of impossible architecture and forgiveness. The game is set like a clockwork and you are turning, flipping and switching elements on the paths between the doors. Unfortunately, there aren't many levels and the game play lasted only some hours. Maybe there are more astonishing looking realms and interesting gimmicks in future versions. Play Store: Monument Valley Also, check out the latest game updates on the official web site of ustwo BTW, the game is also available on the Apple App Store and on Amazon Store for the Kindle Fire.

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• How do I create my own programming language and a compiler for it

  - by Dave

  I am thorough with programming and have come across languages including BASIC, FORTRAN, COBOL, LISP, LOGO, Java, C++, C, MATLAB, Mathematica, Python, Ruby, Perl, Javascript, Assembly and so on. I can't understand how people create programming languages and devise compilers for it. I also couldn't understand how people create OS like Windows, Mac, UNIX, DOS and so on. The other thing that is mysterious to me is how people create libraries like OpenGL, OpenCL, OpenCV, Cocoa, MFC and so on. The last thing I am unable to figure out is how scientists devise an assembly language and an assembler for a microprocessor. I would really like to learn all of these stuff and I am 15 years old. I always wanted to be a computer scientist some one like Babbage, Turing, Shannon, or Dennis Ritchie. I have already read Aho's Compiler Design and Tanenbaum's OS concepts book and they all only discuss concepts and code in a high level. They don't go into the details and nuances and how to devise a compiler or operating system. I want a concrete understanding so that I can create one myself and not just an understanding of what a thread, semaphore, process, or parsing is. I asked my brother about all this. He is a SB student in EECS at MIT and hasn't got a clue of how to actually create all these stuff in the real world. All he knows is just an understanding of Compiler Design and OS concepts like the ones that you guys have mentioned (ie like Thread, Synchronisation, Concurrency, memory management, Lexical Analysis, Intermediate code generation and so on)

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• Why would Java app make RPC call to itself?

  - by amphibient

  I am working with a multithreaded homegrown multi-module app in my new job. We use the the Thrift protocol to communicate RPC calls between different stand-alone applications in a distributed system. One of them listens on multiple ports and I just noticed that it actually makes an RPC call to itself from one thread invoked from one socket it listens to (web service call) to another port within the same app. I verified that it could accomplish the same thing if it just went and directly called the method that the remote procedure ultimately invokes as it is all within the same application, same JVM. To make it even more mysterious, the call is completely synchronous, i.e. no callbacks involved. The first thread totally sits and waits until it makes a call across the wire to itself and comes back. Now, I am perplexed why anybody would do it this way. It seems like calling somebody on the phone that sits in the same room as you do. Can anybody provide an explanation why the developer before me would come up with the above mentioned model? Maybe there is a reason and I am missing something.

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• Cron prepending filename to script output

  - by Caitifty

  I'm having an issue with unwanted lines being added to files output by a cron job. I have a script in /etc/cron.hourly which selects some data from a mysql database and saves it in a text file in /var/www. When I run the script as root, it does exactly what I expect it to do. When the script is executed by cron, it creates the same file, but prepends the following three lines at the top of the output file: :::::::::::::: /var/www/outputfilename :::::::::::::: I can't for the life of me work out how to stop this unwanted behavior. The line in /etc/crontab for cron.hourly is the default "44 * * * * root cd / && run-parts --report /etc/cron.hourly". If I use su to change to being root and do "cd / && run-parts --report /etc/cron.hourly" the script runs as expected and the output doesn't have the mysterious additional 3 lines. I've also tried removing the --report flag from the run-parts command in case that was somehow connected, but no joy. Finally, perusing the cron log output in /var/log/syslog just says cron.hourly ran without giving any additional information. Any suggestions on solving this weird problem most welcome..

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• Windows7 IIS7: zips don't have php5isapi.dll Can I use php.dll instead?

  - by Pete Alvin

  The page: How to Install PHP 5.2 on IIS 7and Windows Vista (and a few others) reference a mysterious php5isapi.dll which is not in the Windows install, or the zip files: php-5.3.2-Win32-VC9-x86.zip - VC9 x86 Thread Safe php-5.3.2-nts-Win32-VC9-x86.zip - VC9 x86 Non Thread Safe There was another post on stackoverflow that said it's obsolete and replaced by "fastapi" but no instructions mention this. I did find a php.dll in the zip file. Can I use that instead of php5isapi.dll? It's very frustrating trying to install basic PHP5 on Windows with MySQL.

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• Best tools to monitor Tomcat

  - by Pier Luigi

  Hi all, I'm searching free tools for monitor tomcat (traffic, memory usage, threads, requests, CPU, logs,...). I'm currently using lambdaprobe on Tomcat 5.5.x, but it seems that is no more developed (or not? the site lambdaprobe.org is always down for me...). Has someone good experiences to share? In lambdaprobe there are some info available only if tomcat is instrumented with JMX. Well, JMX is something of strange and mysterious for me. Is a good solution in a production server? It's worth to spend my (little) time to learn it?

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• How do you implement Software Transactional Memory?

  - by Joseph Garvin

  In terms of actual low level atomic instructions and memory fences (I assume they're used), how do you implement STM? The part that's mysterious to me is that given some arbitrary chunk of code, you need a way to go back afterward and determine if the values used in each step were valid. How do you do that, and how do you do it efficiently? This would also seem to suggest that just like any other 'locking' solution you want to keep your critical sections as small as possible (to decrease the probability of a conflict), am I right? Also, can STM simply detect "another thread entered this area while the computation was executing, therefore the computation is invalid" or can it actually detect whether clobbered values were used (and thus by luck sometimes two threads may execute the same critical section simultaneously without need for rollback)?

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