from Greg Linden

Sam's smiling face first was known to me when I met him at Caltech through my sister. I remember his energy, as if powered by the California sun, his hands moving as enthusiastically as his mouth when he talked.

I remember Sam at Rusland Hall at my sister's wedding celebration, always friendly, always chatting, always finding something interesting in each conversation to explore. It was a joyous time for him and all, a celebration and a gathering of friends, in the beautiful countryside of the Lake District in England.

I remember Sam at the dining room table in my mother's house on holidays, a welcome addition to our family's table on any day, and especially welcome on a holiday feast.

I remember meeting Sam for lunch at Google, sitting outside on a warm day, talking about a piece of his work at Google on a research project. As he always did, he took some absurdly difficult problem and made it seem trivial, in this case identifying small patches of the nighttime sky from blurry and noisy telescope images taken by amateur astronomers. How would you do this, he asked, always curious to learn. And, in response to my sputtering, he said, just use fingerprints, and went on to describe an idea using polygons drawn between a few of the brightest stars in the image. As he often did, he launched into a passionate description of the work, but, in a way unique to Sam, always looked back at me to make sure I followed along, helping me keep up when I might start to fall behind.

I remember watching Sam's lectures on the Web and reading his wonderful tutorials. A gifted teacher, Sam jumped to intuitive explanations of complex techniques, cutting to the core purpose of the algorithms, while laying bare all of their weaknesses. So many bury the flaws of any particular technique under a sea of obfuscation, but not Sam, who would not only point out the problems, but also help guide toward their solutions.

I remember arguing with Sam about Barack Obama before the election of 2008. Sadly cynical about human nature, I could not muster enough hope for the wisdom and intellect of the American people to see electing a man whose name rhymes with a well known terrorist's. Typically optimistic about human nature, Sam thought this absurd and, as he was wont to do, he told me so.

I remember Sam's ever-present smile. I remember admiring Sam. I remember learning from Sam. I remember wanting to be a bit more like him.

I will miss Sam. I feel privileged by the time I had with him. But I wish there had been more.