# Heinz Rutishauser

Heinz Rutishauser ( born January 30, 1918 in Wine Rheinfelden, Switzerland, † 10 November 1970 in Zurich ) was a Swiss mathematician and a pioneer of modern numerical mathematics and computer science avant la lettre.

## Life

Heinz Rutishauser studied from 1936 Mathematics at the ETH Zurich and graduated in 1942 with a diploma. From 1942 to 1945 he was assistant to Walter Saxer at ETH Zurich and from 1945 to 1948 teaching math in Glarisegg and Trogen. In 1948 he received his doctorate at the ETH with a much dissertation on function theory.

1948/49, remained Rutishauser in the United States at Harvard and Princeton. From 1949 to 1955 he was a research associate at the recently founded by Eduard Stiefel Institute of Applied Mathematics, ETH Zurich, where he was instrumental in the development of the first Swiss computer ERMETH along with Ambros Speiser. He contributed in particular in the field of compiler pioneering work and had finally also to the definition of the programming language Algol 60.

1951 Rutishauser lecturer, 1955 and 1962 extraordinary professor of Applied Mathematics at the ETH. He was in 1968 head of the department of computer science, later emerged from the Institute of computer science and finally the computer science department at ETH Zurich.

At least since the 1950s Rutishauser suffered from heart problems. In 1964 he suffered a severe heart attack, from which he initially recovered. He died on November 10, 1970 in his office at acute heart failure. After his early death, his wife Margrit looked after the publication of his posthumous works.

In 1958 he introduced the LR- algorithm based on the LU decomposition, but is today largely replaced by the more stable QR algorithm.

## Writings

- Automatic allocation plan production. Habilitation thesis ETHZ, 1951.
- Automatic allocation plan production at program -controlled calculating machine. Basel: Birkhauser, 1952.
- Some programming techniques for the ERMETH, JACM, 2 ( 1), pp. 1-4 January, 1955.
- The quotient differences algorithm. Basel: Birkhauser, 1957.
- Lectures on Numerical Mathematics. Volume I: systems of equations, interpolation and approximation. Martin Gutknecht (Ed.). Basel: Birkhauser, 1976, ISBN 3-7643-0810-9. .
- Lectures on Numerical Mathematics. Volume II: Differential equations and eigenvalue problems. Martin Gutknecht (Ed.). Basel: Birkhauser, 1976, ISBN 3-7643-0850-8. .
- Heinz Rutishauser, Ambros Speiser Paul, Eduard Stiefel: program -controlled digital computing devices (Electronic calculating machines ). Basel: Birkhauser, 1951.
- Hans Rudolf Schwarz, Heinz Rutishauser, Eduard Stiefel: Numerical symmetric matrices. Stuttgart: Teubner, 1972, 2nd edition, ISBN 3-519-12311-8.
- Numerical procedures. From estate and teaching. Walter Gander ( ed.). Basel: Birkhauser, May 1998 ISBN 3-7643-0874-5.