Month: May 2014

C++ : mt19937 Example

C++11 introduces several pseudo-random number generators designed to replace the good-old rand from the C standard library. I’ll show basic usage examples of std::mt19937, which provides a random number generation based on Mersenne Twister algorithm. Using the Mersenne Twister implementation that comes with C++1 has advantage over rand(), among them:

  1. mt19937 has much longer period than that of rand, e.g. it will take its random sequence much longer to repeat itself.
  2. It much better statistical behavior.
  3. Several different random number generator engines can be initiated simultaneously with different seed, compared with the single “global” seed srand() provides.

The downside is that mt19937 is a bit less straight-forward to use. However, I hope this post will help with this point :-).
Continue reading C++ : mt19937 Example

Make Offline Mirror of a Site using `wget`

Sometimes you want to create an offline copy of a site that you can take and view even without internet access. Using wget you can make such copy easily:

wget --mirror --convert-links --adjust-extension --page-requisites 
--no-parent http://example.org

Explanation of the various flags:

  • --mirror – Makes (among other things) the download recursive.
  • --convert-links – convert all the links (also to stuff like CSS stylesheets) to relative, so it will be suitable for offline viewing.
  • --adjust-extension – Adds suitable extensions to filenames (html or css) depending on their content-type.
  • --page-requisites – Download things like CSS style-sheets and images required to properly display the page offline.
  • --no-parent – When recursing do not ascend to the parent directory. It useful for restricting the download to only a portion of the site.

Alternatively, the command above may be shortened:

wget -mkEpnp http://example.org

Note: that the last p is part of np (--no-parent) and hence you see p twice in the flags.