I never thought of myself as a “woman” programmer. I was just a programmer.
Mary Ann (Mansigh) Karlsen
Mary Ann Karlsen, now, and in the early years, with Berni Alder

Retired Programmer Recalls the Early Years of LLNL Computing

Friday, May 13, 2016

More than 50 employees attended a lunchtime talk by Mary Ann (Mansigh) Karlsen on May 4 about her career and experiences as one of LLNL’s early computer programmers. The talk was hosted by the Lawrence Livermore Laboratory Women’s Association’s Women in Science and Engineering (WISE) group and the Computation directorate.

In 1955, when Karlsen was 22 years old, she responded to a “Men Wanted” newspaper ad for programmers at the University of California Radiation Laboratory in Livermore. Karlsen was definitely qualified for the job, having completed a double major in mathematics and chemistry and a minor in physics at the University of Minnesota.

An on-the-job, self-taught computer programmer, the majority of her 39-year Livermore career was spent coding seminal simulation runs for prominent scientists including Berni Alder, David Ceperley, Tom Wainwright, and many others. “I never thought of myself as a ‘woman’ programmer. I was just a programmer. My teachers in high school and college were women so I never thought I didn’t belong,” she said.

Initially assigned to work on the UNIVAC, the Lab’s first computer, Karlsen spent thousands of hours helping computational physicist Berni Alder turn his concepts into computer code to run on Livermore supercomputers. Alder is widely regarded as the founder of molecular dynamics, a type of computer simulation used for studying the motions and interactions of atoms over time.

In the early years, Karlsen was often the biggest single user of LLNL computer resources, sometimes even employing multiple machines to complete a demanding calculation. Using these computers, however, was no simple task. For instance, the UNIVAC, the first computer to store information on magnetic tape, required hands-on operation, with a programmer toggling console switches to execute the problem, and suffered breakdowns several times a day. Despite the challenges, Karlsen loved the work, particularly organizing calculations so as to maximize machine efficiency. “I can’t think of any period of time in computing that I would have enjoyed working in more,” she noted.

Ceperley needed the computing power only Livermore computers could provide, but he didn’t have a security clearance, so each day he would communicate his instructions to Karlsen over the telephone, and she would set up five or 10 different runs for him. The next morning, she would call him with the results. One of the papers that resulted from Karlsen’s collaborations with Alder and Ceperley, “Ground State of the Electron Gas by a Stochastic Method,” remains one of the most highly cited in Physical Review Letters, 36 years later. Karlsen is recognized in the acknowledgements.

Karlsen was also the first at the Lab to make a “movie” of a computer simulation, which was later used to accompany a popular college physics textbook. However, she considers the highlight of her career to be when, some 15 years after her retirement, Alder received the National Medal of Science from President Obama. “I am proud to have contributed and most proud that Berni acknowledged me as a ‘magnificent programmer,’” she said.

Once in a while, she concluded, she stumbles across her name on the internet associated with her work with Alder and colleagues, and it makes her smile.