GREG NELSON March 27, 1953 - Feb. 2, 2015 Palo Alto, California Submitted by Sharon Perl Greg Nelson (born Charles Gregory Nelson), a longtime Palo Alto resident, died on Feb. 2, 2015, after a 17-year battle with brain cancer. Greg grew up in Honolulu, Hawaii, where he attended the University Laboratory School. He moved to the mainland to attend college and graduate school. He lived in Juneau, Alaska, for a year before settling permanently in the Bay Area. Greg received his B.A. degree in mathematics from Harvard in 1976, and his Ph.D. in computer science from Stanford University in 1980, where he worked under the supervision of Bob Tarjan on program verification and algorithms for automatic theorem proving. As an undergraduate at Harvard, he invented a method of combining decision procedures for different logical theories into a decision procedure for the combination of the theories (often called the "Nelson-Oppen method") that has become influential in the automatic theorem-proving community. In 2013 he received the Herbrand Award for Distinguished Contributions to Automated Reasoning for his pioneering contributions to theorem proving and program verification. Greg was a Renaissance computer scientist, combining a deep understanding of mathematics and theory with a strong ability to design and implement systems. He brought his passion for precision and correctness to all of the work he did. He made significant contributions in the areas of programming language design (as a member of the Modula-3 committee), distributed systems (Network Objects), constraint-based graphics editors (Juno and Juno-2), window systems (Trestle), optimal code generation (Denali), and multi-threaded programming (Eraser). He had a profound influence on the many students who he hosted for internships and advised on their thesis research, as well as the many colleagues with whom he collaborated throughout his professional career, first at the Xerox Palo Alto Research Center and later at DEC's Systems Research Center and HP's research laboratories. He was a brilliant researcher and teacher. His commitment to excellence, evidenced in his own work, inspired others to do the same. Greg loved being physically active. As a boy he excelled at gymnastics and tennis, and enjoyed body surfing. He loved being in the mountains and in the wilderness, hiking, backpacking, skiing and kayaking. His favorite sport was volleyball, and he regularly played in pick-up games until the brain tumor recurrence made that impossible. For many years at the research labs where he worked he organized weekly volleyball games for the staff and interns, which was a great opportunity for people to get out from behind their screens into the fresh air, get some exercise and socialize. He encouraged people of all abilities to play, and created a fun environment that fostered both good sportsmanship and development of skills. Greg had many interests. He enjoyed playing pool, poker, backgammon, chess, cooking, ballroom dancing, traveling, hosting dinner parties, spending time with friends and family, and learning about new things. He was a lifelong reader, spending many hours every week at the library. He was equally likely to be found reading an economics or physics textbook as a book on history, or a biography, or a novel. A well-used copy of The Random House Unabridged Dictionary was usually by his side. In addition to his intellectual brilliance, Greg will be remembered for his adventurous spirit, humor, modesty, personal integrity, kindness, generosity, courage and optimism. The latter two qualities were especially evident in the last few years as he faced his illness with an equanimity and grace that inspired all who knew him. Even as the illness took away his ability to enjoy so many of the things he loved, Greg was grateful for what he had, and that he lived to see his daughter graduate from high school and start college. Greg is survived by his wife, Sharon Perl, and daughter, Julia Nelson, of Palo Alto; brothers, David Nelson (married to Loretta) and Michael Nelson (married to Karen); and mother, Alice Nelson of Honolulu, Hawaii. He was preceded in death by his father, Charles Edward Nelson; his brother Richard Nelson; and twin sons, Adam and Andrew, who died in infancy. A memorial gathering will be held at the Stanford Faculty Club at 2 p.m. on Sunday, March 8. Friends, family, and colleagues are welcome to join us in celebrating Greg's life. Memorial donations may be made to the National Brain Tumor Society (braintumor.org).