Post-doctoral researcher (3 years) in Computer Science with focus on Compilation of Linear Algebra Expressions

The Department of Computing Science seeks a postdoctoral researcher who will work on Compilers for Linear Algebra Expressions. The employment is full-time and for three years, starting on a mutually convenient date. The deadline for applications is January 31, 2025.

Department of Computing science
Our institution, characterized by world-leading research and many internationally highly-ranked educational programs, is looking for a postdoctoral researcher to work on a compiler for linear algebra expressions.

The Department of Computing Science has been growing rapidly in recent years, with a focus on creating an inclusive and bottom-up driven research environment. Our workplace consists of a diverse set of people from different nationalities, backgrounds and fields. As a postdoctoral researcher, you receive benefits in career development, networking, administrative and technical support functions, along with good employment conditions. More information about the department is available at: https://www.umu.se/en/department-of-computing-science/

Is this interesting for you? We welcome your application until January 31, 2025.

Project description and working tasks
Linear algebra expressions are evaluated in an efficient and robust way by mapping them to a carefully chosen sequence of calls to optimized functions as offered by libraries such as BLAS and LAPACK. The mapping is by no means unique, and different mappings differ in terms of time, space, and accuracy. When the sizes of the matrices are unknown at compile-time, as is often the case, then the problem is further complicated by the fact that no single mapping is optimal for all combinations of matrix sizes. As a consequence, any code generated (at compile-time) to evaluate the at run-time) must consist of more than just a single sequence of function calls.

We recently received a grant from the Swedish Research Council to investigate how to effectively compile linear algebra expressions when the matrix sizes are unknown at compile-time. The project aims to address the problem using e-graphs. An e-graph is a data structure commonly used in automated theorem provers and recently popularized for optimizing compilers and many other optimization tasks. We hypothesize that an e-graph would be an effective tool for discovering and encoding a large set of alternative ways of evaluating a particular expression with unspecified matrix sizes. When a concrete expression is evaluated at run-time, thus revealing the matrix sizes, an extraction algorithm can identify an optimal evaluation scheme for that particular instance of the expression from the compiled e-graph. This project extends our previous work on linear algebra compilers: https://linnea.cs.umu.se/

This position is funded by the Swedish Research Council through project 2024-04957 “Compiling General-size Linear Algebra Expressions using Equality Graphs”. The postdoctoral researcher will be part of the High-Performance and Automatic Computing group (HPAC), collaborating with Paolo Bientinesi and Lars Karlsson. HPAC’s webpage: https://hpac.cs.umu.se/

Qualifications
To be appointed under the postdoctoral agreement, the postdoctoral fellow is required to have completed a doctoral degree or a foreign degree deemed equivalent to a doctoral degree. This qualification requirements must be fulfilled no later than at the time of the appointment decision.

To be appointed under the postdoctoral agreement, priority should be given to candidates who completed their doctoral degree, according to what is stipulated in the paragraph above, no later than three years prior. If there are special reasons, candidates who completed their doctoral degree prior to that may also be eligible. Special reasons include absence due to illness, parental leave, appointments of trust in trade union organisations, military service, or similar circumstances, as well as clinical practice or other forms of appointment/assignment relevant to the subject area. Postdoctoral fellows who are to teach or supervise must have taken relevant higher education pedagogical courses.

Requirements:

• Doctorate in computer science, mathematics, or similar.
• Strong command of both written and spoken English language.
• Proficiency in programming languages, compilation techniques and optimizations.
• Proficiency in C, C++, and/or Rust.

Merits:

• Experience with e-graphs.
• Familiarity with theory and algorithms used by, for example, proof assistants, term rewriting systems, optimizing compilers, program analysis tools, constraint solvers, or similar.
• Familiarity with linear algebra libraries and high-performance computing.

Application
A complete application must contain the following documents:

• A cover letter that motivates the interest in the position and that describes how the qualifications and experience are relevant to the employment (maximum 2 A4 pages with 11pt font).
• A curriculum vitae.
• Electronic link to doctoral dissertation and all relevant publications.
• Copies of degree certificates, including documentation of completed academic courses and obtained grades.
• Contact information for three reference persons.
• Documentation and description of other relevant experiences or competences, including software projects.

The application must be written in English or Swedish. If attached documents are written a different language, then a translation to English or Swedish must be included. Attached documents must be in pdf format. Applications must be submitted electronically using the e-recruitment system of Umeå University, and be received no later than 2025-01-31.

For additional information, please contact Paolo Bientinesi (pauldj@cs.umu.se).

We look forward to receiving your application!