Posts tagged ‘work’

Guys from EC2 announced micro instances – it costs 2 (two) cents per hour for linux and now it’s will costs less than traditional dedicated hosting with root access – monthly payment for EC2 micro instance will be about 15 USD, and price for root/linux on dedicated hosting will be about 30 USD/month. It’s really good news – you can have 100 boxes cluster just for two usd per hour! Bad thing is that micro instances don’t have their own disk space – EBS only, looks like this best ever use case for this type of instances will be highly-distributed computational grid with all data stored in RAM. And don’t forget that EBS will costs you some money – $0.10 per allocated GB per month Amazon EBS also charges $0.10 per 1 million I/O requests you make to your volume . Fredrick Poller’s already check out micro instances performance by sysbench : Amazon EC2 Micro instance, how fast is it?.

By unknown reasons Sun JDK was moved to partner repository, so to use sun jdk you need to do this steps

sudo add-apt-repository "deb http://archive.canonical.com/ lucid partner"
sudo apt-get update
sudo apt-get upgrade

and then enjoy :

sudo apt-cache search jdk | grep sun
sun-java6-source - Sun Java(TM) Development Kit (JDK) 6 source files
sun-java6-jre - Sun Java(TM) Runtime Environment (JRE) 6 (architecture independent files)
sun-java6-jdk - Sun Java(TM) Development Kit (JDK) 6
sun-java6-javadb - Java(TM) DB, Sun Microsystems' distribution of Apache Derby
sun-java6-demo - Sun Java(TM) Development Kit (JDK) 6 demos and examples
sun-java6-bin - Sun Java(TM) Runtime Environment (JRE) 6 (architecture dependent files)

AWS related links :

You can use sed :

sed -e 's/\([^\d]*\)/\L\1/' in.txt > out.txt

or perl inliner :

perl -ne 'utf8::decode $_; $_ = lc $_; utf8::encode $_; print' in.txt > out.txt
.
Both guys works fine for unicode file too.

Using telnet in bash scripts to automate some stuff ? It’s really easy, here’s an example to tell “hello world” on telnet server :

req="hello world"
server="my_server 1234"
val=`( echo open ${server}
sleep 3
echo "${req}"
sleep 1 ) | telnet`
echo $val

Okay, we have text file with list of urls and want to have firefox’s screenshots from this pages and also we need to have this screenshots in some normalized resolution ( like all images should be in 300×400 – thumbnails ). First of all you need to install Command line print Firefox add-on. Then create some simple script which will run firefox with needed url, print screenshot and close ( in my case via kill – may be it’s too brutal ) firefox in cycle. It may look like this ( url_list.txt – file with urls – each url on its own line :-)), after running this script you will have many *.png files which is screenshots for ulrs – 0.png – for first url in urls_list.txt, 1.png for second and so on.

#!/bin/bash
id=0
while read line
do
firefox -print $line -printmode png -printdelay 10 -printfile ${id}.png
ps ax | grep firefox | awk '{ print $1 }' | xargs kill -9 ;
id=$[$id+1]
done < urls_list.txt

And now then we have screenshots ( all this guys are in different resolution in common ) then we need to normalize them – to create thumbnails for all images in 300×400 resolution – convert helps!

for f in *.png;
do
convert -thumbnail 300x400! ${f} thumb_${f}
done

And we have many thumb_*.pn with 300×400 resolution all. A little note – using resolution without ! sign will work in another way – resize will be processed proportionally with using resize only for one dimension ( bigger one ).

GIT

Subversion ( svn )

Hash tables :

  • Network Applications of Bloom Filters: A Survey – by Andrei Brodery and Michael Mitzenmacherz
  • Coding bloom filters
  • General Purpose Hash Function Algorithms
  • IP-Lookup with a Blooming Tree Array: A New Lookup
  • Algorithm for High Performance Routers
  • C++ Q/A :

  • Bjarne Stroustrup’s C++ Style and Technique FAQ
  • Cloud computing is a term that originally meant elastic on demand computing but is now a term applied elastically by marketdroids to any form of virtualisation.
    This is part of the transition from 2009’s vBullshit to BaaS, Bullshit as a Service.

    via chapmancentral.demon.co.uk

    SaaS bullshit PaaS bullshit bingo

    Here’s some stuff about ( yeah, I know – ‘geeks, stop migrating from svn and git and vise versa – just developer code and don’t spent time on this!‘ ) svn and git comparison.

    What do we have : git and svn installed on a same server, empty both svn and git repositories – I will add same data and provide same changes in both repositories,  and also, in another folder, I will checkout how update changes works – so in this tests I’m going to figure out how it works for ‘commiters’ and for ‘those who update changes’. My tests deal with  typical operations with version control systems  – checkout time for adding, pushing and pulling various types of data and checkout how update for them will work – test’s detailed information is below table. For git I use git+ssh protocol, for svn I use svn protocol. I don’t provide any special configuration nor for git nor for svn – all settings is about to be default. Also I would like to note that this tests is partially incomplete – I don’t checkout how delete, branching, merging and some other functions works – so in future I will try to add these points onto this test. Main result of this test – git is faster than svn about a 2-3 times in typical configuration. There’s only one really bad points – git works bad on pretty big files ( > 300 mb size), for some big size ( ~1gb ) it git even can exit with error about memory leak – there’s some special git-related project – like git-bigfiles – this stuff should help you to work with git and big files together.

    svn git svn/git
    Test 1 : adding boost 1_43 add  ( 1 sec )+ commit ( 600 sec ) = 601 sec add ( 3 sec ) + commit ( 86 sec ) + push ( 612 sec ) = 701 sec 0.85
    Test 2: checkout repository after Test 1 svn co = 109 sec clone = 18 sec 6.05
    Test 3 : small changes in sources – add first line with comment to some files – 346 files changed svn commit = 5 sec commit(2 sec ) + push ( 2 sec ) =4 sec ~1
    Test 4: update after this Test 3 svn update = 15 sec git pull ( 7 sec) ~2
    Test 5: bigger change  – add first line with comment to 5363 files svn commit = 103 sec commit ( 6 sec ) + push ( 18 sec ) = 24 sec 4.29
    Test 6: update after Test 5 svn update = 28 sec git pull = 12 sec 2.3
    Test 7: real-life project add ( 2.6 gb of data ) svn add(21) + svn commit(1h 2m 25s) = 3 766 sec add (38 ) + commit ( 1m23 ) + push ( 18m28 ) = 1 m 51 + 18m 28sec= 20 m 19 sec = 20 m 19 sec = 1 219 sec 3.1
    Test 8: update after Test 7 svn update ( 11m 58 sec ) = 718 sec git pill = 5m 27 sec = 327 sec ~2.2
    Test 9: source change (change namespace visibility) svn commit ( 1m 28 sec ) = 98 sec commit (5 sec ) + push ( 3 sec) = 8 sec 12.25
    Test 10 : update after Test 9 svn up  = 22 sec pull ( 9sec) 2.4
    Test 11: full checkout project svn co 12m 45sec = 765 sec pull ( 4 min 3 sec ) = 243 sec 3.14
    Test 12: big file test : apache log ( 50 mb ) svn add(3) + commit (1m 27s ) = 1m 30 sec = 90 sec add (3) + commit(6) + push (1m 18 sec) = 1m 17 sec = 77 sec 1.16
    Test 13 update after test 12 up = 26 sec pull  = 17 sec 1.52
    Test 14 : big files test: c++ sources in one file ( 70 mb ) add(3) + commit(1m 15 sec) = 1m 18 sec = 78 sec add (2) + commit (2) + push ( 56 sec ) = 1 m = 60 sec 1.3
    Test 15 : update after Test 14 up = 28 sec pull = 14 sec ~2
    Test 16: 100 MB xml with encoded data add(3) + commit (8m 37 sec)= 8m 40 sec = 520 sec add (9 sec) + commit (1) + push ( 24m 34 sec) = 24 m 44 sec = 1484 0.35
    Test 17 : update after Test 16 up = 52 sec pull = 47 sec 1.10
    Test 18 : 300 MB xml with encoded data add ( 1 ) + commit( 9 m 26 sec )= 9m 27 sec = 567 sec add (3) + commit(8) +push (17m  12 sec) = 17 m 33 sec = 1053 sec 0.53
    Test 19:  update after test 18 1m 39 sec pull= 1m 29 sec 1.1
    Test 20 : 1200 MB xml with encoded data 1h 24m 34s failed ?
    Test 21 : update after Test 20 5m 47 sec failed ?
    ~2.6

    So – In common we have that git is about 2.6 faster than svn.

    I understand that this is may be very non-precious tests and also I don’t check how delete or branching works, but anyway I checkout my own most used operations during this test. In common we can see that git is more than 2 times faster than svn – everything looks fine with git, except one really bad thing  – work with big ( more than 100 mb size ) files – for this type of file svn is really works faster, and for too big ( more than 1 GB files ) git even crashed during ‘git push’ command with ‘fatal: Out of memory, malloc failed‘ message.


    Test1
    boost 1_43 C++ library :  29135 files and 31609 objects including folders, 286 Mb summary size

    Test 3
    I just add first line to some cpp files :

    find ./ -name "*a???.cpp" -exec sed -i 1i"//test comment `date` : {}" {} \;

    Test 5
    Change all *.cpp files in the same way :

    find ./ -name "*.cpp" -exec sed -i 1i"//big test comment2 `date` : {}" {} \;

    Test 7:  Add  real-life repository :  many sources in cpp, perl, erlang, makefiles, bash scripts, MS word documents, images, pdf’s, compiled binaries, resource files, etc,  in sum it contains 4605 files, size is about 2.6G

    Test 9:
    Refactoring simulation : make to use “std::” specifier for all cerr and cout. Not sure it’s really safe in real-life-development, but it’s okay for test purpose.

    find ./ -name "*.h"   -exec sed -i "s/  cerr/std::cerr/g" {} \;
    find ./ -name "*.cpp" -exec sed -i "s/ cerr/std::cerr/g" {} \;
    find ./ -name "*.cpp" -exec sed -i "s/ cout/std::coutr/g" {} \;

    Test 11:  checkout whole project

    Test 12: adding 50 mb text file – apache logs

    Test 14: adding 72 mb file – many c++ sources concantenated in one big file

    Test 16: small xml : 100 mb – xml file sample from real life

    Test 18: medium xml : 300 mb – same ( but bigger ) real-life xml fil

    Test 20: large xml : 1200 mb – sample of pretty big real-life xml

    git push failed with error message of memory leak ( as I can see ) : “fatal: Out of memory, malloc failed”

    I collect some usefull information about different source text repositories version control systems : git, svn, cvs, mercury links – take a look on this if you’re interested in different VCS system using.

    Since middle of April 2010 I’m work with redmine as corporate wiki in my company – we choose redmine mostly because it’s free, open-source and pretty popular – we don’t need to provide any accounting stuff to buy it officially and in case of some troubles we can find solution in redmine user’s community ( or fix it by ourselft – it’s written on Ruby btw ). As some minus of redmine I can note that redmine don’t really have very detailed documentation – some stuff is skipped and you need to figure out it by yourselft. So in this post I will share my own tips and trick as redmine active user.

    Using anchors in redmine

    There’s no {anchor} macro in redmine ( Confluence wiki got it btw ) – instead of this you can use h1, h2 or h3 tags ( but not h4 ! ) – header text will be used by redmine as anchor text. Also if your anchor text contains space you need to replace this spaces (in link ) by minus sign. Also I can note that it’s looks that anchor texts isn’t case sensitive. Here’s some examples which can help you figure out it better :
    Here’s some anchors from current page to page with name “my test page” which contains anchors “Hello wordl!” and “test”, so page which contain links is looks like :

    [[my_test_page#Hello-world|Hello world]] - link to hello world section on my test page
    [[my_test_page#test|test]] - link to test section on my test page

    And page to which we refer it something about :

    h1. Hello world
    Some thing about ANSI C.
    h2. Test
    Something about test
    >

    Again I would like to note that only h1,h2, h3 tags will be treated as anchors, not h4. Also you can’t use header with “!” or “?” because you will have troubles with referring anchor to it ( I mean “h1. Hello world!” won’t create proper anchor is I can see from my experience ).

    Usefull tips for table formatting in redmine

    Here’s a link : Redmine: Create Tables Using Textile Formatting

    How to use HTML tags in your redmine wiki documents ?

    It’s really easy – go to file redcloth3.rb ( in my installation it located in /opt/redmine/lib/redcloth3.rb ) and change line onto adding tags which you would like to use. For example to enable <br>
    and <a>  it’s enough to change it line which contains ALLOWED_TAGS initialization with your tags. Originally it was ( in my case this stuff located in 1187 line )
    ALLOWED_TAGS = %w(redpre pre code notextile)


    and I just it change to

    ALLOWED_TAGS = %w(redpre pre code notextile br a)

    To apply this changes don’t forget to restart web server – after this you will be able to use <a>.. </a> as they should be in HTML your redmine wiki pages. Also allowing tag <a> ( and as result enable <a name=”#my_anchor_text”> )will give an unlimited possibility to put anchors on wiki pages on any place which you like, for example in middle of tables.

    Redmine usefull links

    .. to be continued

    Q1: What value will be printed ?
    double d1 = 16, d2=2.0;
    double d3 = (1/2) * ( sqrt(d1) + d2/2);
    cout << d3 << endl;

    Q2: Please write your own itoa implementation

    Q3: What is pure virtual destructor? Shall ( or can ) pure virtual functions be implemented ?

    Q4: Give an example of abort function implementation

    Q5: Why we need semicolon after closing bracket in C++ class declaration ?

    Q6: Can we call destructor directly? For what we may need it ?

    Q7: Can we call constructor directly? For what we may need it ?

    Q8: Can we thron an exception in destructor ?

    Q9: What happen if we call pure virtual methods in constructor or destructor ? Same question about ‘non-pure’ virtual methods ?

    Q10: Why don’t we have virtual constructors in C++ ?

    Q11: What is difference between new and new [] ? Same thing about delete and delete [] ?

    Q12: What is a difference between static_cast, dynamic_cast, reinterpret_cast and const_cast ?

    Q13: Why do we need explicit keyword in C++ ?

    Q14: Explain difference between

    const MyClass c;
    const MyClass &c2 = c;
    const MyClass *c2 = &c;
    const MyClass * const c2 = &c;

    Q15: Difference between const_iterator and iterator

    Q16: Implement Rand5 ( which returns randomly 0..4 ) use only Random7 ( which returns 0..6)

    Q17: Can we use object of class ( or structure ) which doesn’t have name? Can we declare and use classes and structures without names ?

    Q18: What is it factory pattern ?

    ( to be updated and continued very soon 🙂

    Answers ( if you need it 🙂 ) below Continue reading ‘C/C++ interview questions’ »

    Some usefull highlights which looks interested for me from Laws of productivity : 8 productivity experiments you don’t need to repeat (if this link doesn’t work please use this link onto copy hosted on bokov.net) – simple thoughts which may help you to organize process better and make it more efficient. Continue reading ‘Laws of productivity : 8 productivity experiments you don’t need to repeat’ »

    Using json in bash :

    • jsawk : work with an array of JSON objects read from stdin, filter them using JavaScript to produce a results array that is printed to stdout. For example get’s json ( from Yahoo image search by ‘madonna’ query ) and add some info ( madonna’s real name ) to this
    • wget http://bokov.net/json_example.json
      cat json_example.json | ./jsawk "this.ResultSet.RealName=\"Louise Ciccone\"" > updated_info.json

    • you can use some bash/awk/sed stuff to parse json. For example – list all image urls from json
    • wget http://bokov.net/json_example.json
      cat json_example.json | sed -e 's/[{}]/''/g' | awk -v k="text" '{n=split($0,a,","); for (i=1; i<=n; i++) print a[i]}' | grep '"ClickUrl":' | sed 's/:/ /1' | awk -F" " '{ print $2 }'

    • or use library from json.org for language which you like 🙂

    via v.kruchkov

    The world's greatest service cloud provider

    We have git repo at github (  and would like to move onto some our corporate box inside our network, for example on internal.bokov.net. This repository is shared for group of developers and all who have ssh access onto internal.bokov.net shall have right to commits onto git repository. So first of all prepare place for git repo at new hosting :

    ssh user@internal.bokov.net
    cd var
    mkdir git_repo
    chmod 777 git_repo
    cd git_repo
    mkdir my_project
    cd my_project
    git init --bare --shared=all
    cd objects
    chmod g+ws *

    Next clone existing repo and change its settings to point onto internal.bokov.net

    git clone --bare git@github.com:bokov/github_project.git
    git remote add -t master -m master origin ssh://internal.bokov.net/var/git_repo/my_project/
    git push origin master

    to start work with new repo just use

    git clone ssh://internal.bokov.net/var/git_repo/my_project/

    have fun.

    • Ubuntu doesn’t asking for login after boot up ( may happen after unexpected shutdown ) :
      press Ctrl-Alt-F1 to login in terminal mode and use fsck to fix it
    • Add user short memo :
      [root@my-box ~]# useradd -g users -u 560 tuser
      [root@my-box ~]# passwd tuser

      ps. sudo will be required in not-root case 🙂
    • Proper access rights for .ssh files :
      chmod 700 ~/.ssh
      chmod 600 ~/.ssh/id_rsa
      chmod 644 ~/.ssh/id_rsa.pub
      chmod 644 ~/.ssh/authorized_keys
      chmod 644 ~/.ssh/known_hosts
    • List all files in folder sorted by size :
      find . -type f -exec du -k "{}" \; | sort -n

    Short how-to about configuring Ubuntu to work with EC2 API ( for Ubuntu 10.04 users – Sun JDK was moved to partner repository so please check out Where’s sun JDK on Ubuntu 10.04 ? before follow described steps ).

    Continue reading ‘Configuring Ubuntu ( 9.10 ) to work with Amazon EC2’ »