Google recently allowed a reporter from the New York Times to spend a day with Singhal and others in the search-quality team, observing some internal meetings and talking to several top engineers. There were many questions that Google wouldn't answer. But the engineers still explained more than they ever have before in the news media about how their search system works.
As Google constantly fine-tunes its search engine, one challenge it faces is sheer scale. It is now the most popular Web site in the world, offering its services in 112 languages, indexing tens of billions of Web pages and handling hundreds of millions of queries a day.
Even more daunting, many of those pages are shams created by hucksters trying to lure Web surfers to their sites filled with ads, pornography or financial scams. At the same time, users have come to expect that Google can sift through all that data and find what they are seeking, with just a few words as clues.
"Expectations are higher now," said Udi Manber, who oversees Google's entire search-quality group. "When search first started, if you searched for something and you found it, it was a miracle. Now, if you don't get exactly what you want in the first three results, something is wrong."
Google's approach to search reflects its unconventional management practices. It has hundreds of engineers, including leading experts lured from academia, loosely organized and working on projects that interest them. But when it comes to the search engine -- which has many thousands of interlocking equations -- it has to double-check the engineers' independent work with objective, quantitative rigor to ensure that new formulas don't do more harm than good.
As always, tweaking and quality control involve a balancing act. "You make a change, and it affects some queries positively and others negatively," Manber says. "You can't only launch things that are 100 percent positive." The epicenter of Google's frantic quest for perfect links is Building 43 in the heart of the company's headquarters here, known as the Googleplex.
At the top of a bright chartreuse staircase in Building 43 is the office that Singhal shares with three other top engineers. It is littered with plastic light sabers, foam swords and Nerf guns. A big white board near Singhal's desk is scrawled with graphs, queries and bits of multicolored, mathematical algorithms. Complaints from users about searches gone awry are also scrawled on the board.
Any of Google's 10,000 employees can use its "Buganizer" system to report a search problem, and about 100 times a day they do -- listing Singhal as the person responsible to squash them.
"Someone brings a query that is broken to Amit, and he treasures it and cherishes it and tries to figure out how to fix the algorithm," says Matt Cutts, one of Singhal's officemates and the head of Google's efforts to fight Web spam, the term for advertising-filled pages that somehow keep maneuvering to the top of search listings.
Some complaints involve simple flaws that need to be fixed right away. Recently, a search for "French Revolution" returned too many sites about the recent French presidential election campaign -- in which candidates opined on various policy revolutions -- rather than the ouster of King Louis XVI. A search-engine tweak gave more weight to pages with phrases like "French Revolution" rather than pages that simply had both words.