"It makes it possible to actually take advantage of all the computers that we have hooked together", stated Larry Heck, vice president of search and advertising sciences at Yahoo.

Hadoop improves the relevance of ads Yahoo shows on the Internet by analysing the company's endless flow of data - now well over 10 terabytes a day - on the fly. As users click from Yahoo Mail to Yahoo Search to Yahoo Finance and back again, Hadoop helps figure out what ad, if any, is likely to catch someone's attention.

The key lies in mining insights from mind-boggling amounts of data. If a woman repeatedly reads reviews of sport-utility vehicles, then clicks on automotive classifieds and then orders a book about helping a child adjust to kindergarten, she might be in the market for a new family-size car, according to a Yahoo sales presentation.

As part of the push for more openness, Yahoo will be using the technology not only to boost ad sales on its own Web sites, but on sites owned by the 796 members of a newspaper consortium that is working with the search giant to sell more advertising at better prices.

"In some ways, perhaps it is even more targeted than search advertising", stated Leon Levitt, vice president of digital media for Cox Newspapers, a consortium member.

For Yahoo, the roll-out of an innovative approach to Internet advertising is a major accomplishment. When Yahoo launched its Hadoop project in January 2006 it was selling search advertising for half of what Google charged and watching its share of Internet searches dwindle.

Hadoop was first put to work building Yahoo's Web index - the biggest computing problem inside Yahoo. Since then, a team of engineers tuned the software, and researchers inside and outside of Yahoo began using it to experiment on giant data sets.

"All of a sudden, instead of waiting overnight people could get the results of their experiments in a minute", stated Doug Cutting, a work-at-home dad who hacked out the first version of Hadoop in his spare bedroom in Sonoma County, California, as part of an open-source search project.