Before joining Cornell, he was a Courant Instructor of mathematics at NYU. He works broadly in scientific computing, with a particular focus on numerical linear algebra applied to a variety of problems from computer science and electrical engineering. He received B.S. degrees in mathematics and computer science from the University of Maryland and a Ph.D. in computer science from UC Berkeley. He is the recipient of the Householder Prize, the SIAG/LA prize, and a Sloan fellowship.