Courtesy of Dana Angluin

Stanley Eisenstat, professor of computer science, died on Dec. 17 at the age of 76, after a two-and-a-half-week stay at a Yale New Haven Hospital intensive care unit where he was being treated for a pulmonary embolism.

Eisenstat had taught computer science at Yale for almost 50 years. He joined Yale’s faculty in 1971 and served as director of undergraduate studies for the Department of Computer Science.

He received his bachelor’s degree from Case Institute of Technology in 1966 — Case later merged with Western Reserve University to form Case Western Reserve University — and completed his master’s and doctorate at Stanford University, finishing in 1972. Eisenstat also served as an associate editor of the Journal of the Association for Computing Machinery and was a member of the editorial board of the Society for Industrial and Applied Mathematics Journal on Matrix Analysis and Applications. His major research interests included parallel computing, numerical linear and nonlinear algebra and direct and iterative methods for solving sparse linear systems.

Students and professors alike described Eisenstat as a “giant” of both the Computer Science Department and Yale. During his time at Yale, Eisenstat designed and taught a course sequence that has become a core aspect of Yale’s computer science curriculum: CPSC 223, “Data Structures and Programming Techniques,” and CPSC 323, “Introduction to Systems Programming and Computer Organization.”

“He was also probably the best teacher I’ve ever had, in all the ways a teacher can teach,” said Hana Galijasevic ’22, who took multiple classes with Eisenstat and had him as an academic advisor. “He’s the one I’ll be talking about when I myself am aged and long out of Yale.”

Members of the Yale community emphasized the fierce love he had for his students — a level of care that persisted even in his final moments, when he asked that his students not be notified of his death until after the fall term ended.

“The CS department actually prepared a set of get-well messages for him during the departmental holiday zoom gathering on Friday, not knowing that he has already passed away (on Thursday),” wrote Zhong Shao, department chair of computer science, in an email to the News.

Although Eisenstat taught CPSC 323 — a course that students and professors noted was one of the most notoriously difficult and well-known courses at Yale — for over 30 years, students said he still made changes to the curriculum every semester to better communicate certain concepts.

Jau Tung Chan ’21, who served as an undergraduate learning assistant for CPSC 323, said that Eisenstat spent the majority of ULA staff meetings discussing how to improve the course. Another ULA for the course, Gabriel Buchdahl ’23, added that Eisenstat “was constantly asking” what concepts he could make clearer, what students needed help with and what else he could do to help them be successful in the course.

Aaron Shim ’16, who took CPSC 223 and 323 with Eisenstat as an undergraduate, noted Eisenstat’s dedication to improving the course, especially since Eisenstat could have “easily get by doing very little work year to year, considering he has taught it for so long.”

Neal Soni ’23, who took CPSC 323 with Eisenstat, told the News that his drive to make the course better “shows that he really cares about the students’ understanding and students learning computer science.” Soni said that Eisenstat’s dedication to his students “sums up who he is as a person.”

Eisenstat’s unwavering commitment to undergraduates was also evident in his individual interactions with students. Rachel Sterneck ’22 recalled that, before taking CPSC 323, she “rarely interacted with computer science professors.” Eisenstat, however, encouraged her to have daily meetings with him so that she could best understand the material.

Galijasevic described Eisenstat as an “incredibly insightful and kind man,” adding that his non-computer science advice was often just as insightful as his help inside the classroom.

And Buchdahl — who likened Eisenstat’s lectures to “getting an IV drip of CS knowledge shot directly into our bloodstream” — remembers frantically emailing Eisenstat on many Saturday afternoons after running into deep problems with his code.

“He’d write back in 30 minutes, saying something like, ‘Check out line 357, I think that’s where your trouble is.’ What other teacher would take weekend time to download your code and debug it himself?” Buchdahl asked.

Dana Angluin, Eisenstat’s wife and a computer science professor at Yale, described “the generations of undergraduates he taught and advised” as Eisenstat’s “proudest legacy.” Many of his departmental colleagues also spoke of his “encyclopedic” knowledge — both related and unrelated to Yale’s computer science department.

Avi Silberschatz, professor of computer science and Eisenstat’s daily lunch companion, told the News in an email that the pair would regularly discuss everything from issues related to Yale’s computer science department to United States politics and history.

“If I had a question about something about Yale or the Dept. he was able to thoroughly explain how we came to be where we are,” Silberschatz wrote in an email to the News. “He was a superb teacher.”

While most people knew Eisenstat as either their professor or their colleague, Daniel Spielman, Sterling Professor of computer science, knew him as both. Spielman took CPSC 323 with Eisenstat in 1989 and returned to Yale as a professor in 2006.

Spielman, who was previously director of undergraduate studies for applied math, said that he looked to Eisenstat as a model for how to be “exceptional” at the role of DUS. But he also benefited from Eisenstat’s knowledge of computer science and applied math in general.

“When I first started doing experiments with linear equation solvers, Stan was my reference for how to configure competing algorithms,” Spielman told the News. “The first time I presented experimental work (not my usual thing) at a SIAM meeting, I was questioned a lot about my choice of parameters in competitors like Incomplete Cholesky. But, after I said, ‘I set them that way because that’s how Stan Eisenstat said I should,’ all the questions stopped.”

It wasn’t until last year that Eisenstat’s CPSC 323 course added a second instructor, associate professor of computer science Abhishek Bhattacharjee. He recalled Eisenstat’s constant help and influence in helping him teach his first semester of the course.

Even after only two years in Yale’s Computer Science Department, Bhattacharjee said it is evident that Eisenstat “has been the heartbeat of our department for decades. I will genuinely miss him.”

Eisenstat is survived by David Eisenstat, Sarah Eisenstat and his wife Angluin.

While there will not be a service, Eisenstat’s family has asked people to honor his memory by donating to their favorite charities or to those important to Eisenstat, which include Columbus House, Community Soup Kitchen, Connecticut Food Bank and Downtown Evening Soup Kitchen.

For those who wish to donate, computer science undergraduates have put together a fundraiser for the Connecticut Food Bank in honor of Eisenstat.

Roshan Warman ’23 said that Eisenstat ended all of his lectures in a similar — and now especially poignant — manner: “I bid you adieu.”

Madison Hahamy | madison.hahamy@yale.edu