Dzisiaj będę opowiadał o podstawach analizy OLAP i pokazywał wolne oprogramowanie, którym mozna się do tego celu połuzyć.
Prelekcja w ramach projektu Spotkania IT@UW, [Wykład 3] Wstęp do analizy OLAP / MDX przy użyciu serwera Mondrian.
Jakiś czas po prelekcji opublikuję slajdy. Stay tuned!
Tor (The Onion Router) helps me hide what kind of porn do I watch mostly.
No, seriuosly: I run Tor service because it can help evade digital censorship. For porn I use open Internet - that's what it's made for. Digital censorship, OTOH, breaks freedom of speech and distorts free information flow, which I believe are good for development of humanity.
I know that some bad guys also use the Tor network, and this bothers me. Whenever I receive a valid complaint that my node was used to do something unacceptable for me, I do my best to stop this.
OK enough bullshit. Some statistics of my exit node:
- Running ~ since March 2012
- Uptime ~ 99%
- Traffic routed ~ about 1 TB monthly
- Abuse complaints received = 5 (4 about portscanning one about email spam)
- Abuse complaints resolved = 4 (spamming isue not resolved because complaining side did not send full spam message headers)
- Destination IPs blocked: three
- Outgoing port blocked: SSH only
- Contacts with lawyers / govt law enforcement: ZERO
So' it's not that bad.
Want to know more about Tor origins? There is a note on this page:
When the Tor Project was announced a decade ago, Google was still largely seen as fulfilling its corporate motto, "Don't be evil," and Twitter didn't even exist. But researchers Roger Dingledine, Nick Mathewson, and Paul Syverson could already see trouble on the horizon. Created in a U.S. naval lab to safeguard government communications, their brainchild the Tor Project (which stands for "the onion router") is designed to protect anyone and everyone from the dangers of Big Brother. The free software, now relied on by hundreds of thousands of users daily, bounces information through the computers of 3,000 volunteers around the world, hiding the identity of the original user.
Operated by just 15 full-time employees with a budget just over $1 million, thanks to grants from the U.S. State Department and the National Science Foundation, Tor allows people who otherwise might be silenced online -- whether corporate whistleblowers or domestic-violence victims -- to bring important information to light. It has become an especially critical tool over the last two years as activists and journalists from Bahrain to Syria find themselves the targets of increasingly tech-savvy tyrants. "We developed Tor originally with civil liberties in mind," Dingledine told an interviewer. "We want to let people in free countries be able to communicate and secure their communications so they can keep their freedoms." Bit by bit, it's working.
Prof. Scott E. Page introduces all critical concepts for model building - decision trees, cellular automata, linear regression, diffusion model, Markov chains, Lyapunov function and more.
All in very layman-friendly way, in simple English and with lots of example models - mostly social and economic ones.
I think it's great for all people starting their adventure with modeling processes and finding regularities in data.
From time to time I write about some sweet little Linux utilities.
This time let me introduce GNU parallel.
As name suggests, it makes possible to run almost every other command in parallel, on many CPU cores.
Let's give a simple example. Searching for a string in many files. A simple test, on a 2-core box:
$ time bzgrep -w word /u/logs/app*/2012/01/31_app.log.bz2 > word.log real 1m33.492s user 1m25.269s sys 0m8.181s $ time parallel bzgrep -w word ::: /u/logs/app*/2012/01/31_app.log.bz2 > word.log real 0m34.267s user 2m3.112s sys 0m9.193s
For more, read the wonderful list of examples in GNU parallel man page, they speak for themselves.
Of course parallel execution is possible without GNU parallel (with a piece of scripting language, or with xargs)... but this tool is more powerful. See this summary for a list of features and comparison with xargs, pexec and other alternatives.
The great thing about GNU utilities is that they actually still evolve and get better. Every time I see a progress there, it makes me optimistic about the future of open source.
Znowu zapodam coś z nieocenionego archiwum Andrzeja Krzemińskiego:
Przeżył przyjaciela o lat jedenaście, zmarł jednak w okolicznościach dość podobnych, również przez wódę.