Research and Development Engineer

Research and Development Engineer (M/F), the Capla Programming Language The Inria Saclay-Île-de-France Research Centre was established in 2008. It has developed as part of the Saclay site in partnership with Paris-Saclay University and with the Institut Polytechnique de Paris. The centre has 40 project teams, 27 of which operate jointly with Paris-Saclay University and the Institut Polytechnique de Paris; its activities occupy over 600 people, scientists and research and innovation support staff, including 44 different nationalities. One of the long-term goals of the ERC project Fresco1 is to turn the Rocq proof assistant into a competitive tool for doing verified computer algebra. In particular, this requires the ability to implement and formally verify well-known libraries such as GMP or BLAS/LAPACK. A significant milestone was the design of Capla, a safe low-level imperative language suitable for implementing such algorithms, as well as the development of a formally verified compiler for this language. It is now possible to write a library using Capla, to compile it to machine code, to verify its correctness using Rocq, and to invoke its functions from C code. There is also an ongoing postdoc work that makes it possible to invoke Capla code from the Rocq prover and to carry over the semantics of this code to Rocq proofs. Now that the project has shown its meaningfulness, it is important to ensure that the language and the compiler are both widely usable and sufficiently robust to last. The work will be carried out mainly in the Toccata team location in Gif-sur-Yvette and partly in the partner company offices in Paris. Travel expenses are covered within the limits of the scale in force. Responsibilities Add support for records (i.e., C struct) to the language, as only arrays are currently supported. While adding record types does not pose any difficulty as far as the theory is concerned, it will require some tedious work to adapt the formal proofs of the compiler and of the type safety, especially if the splitting constructs from the language are extended to support records. Add support for function calls inside size expressions. Currently, only simple expressions are allowed to describe the size of an array; it is not possible to invoke functions (e.g., the absolute value). This work item is expected to be difficult and long, as it will require some large changes to the semantics and the compiler, and therefore to the formal proof. Disentangle the type safety from the type checker. Currently, both are proved at once, which means that improving the type checker would break the type safety of the language. This work item requires to design some algorithm-free typing rules and to split the existing formal proof accordingly. It should be rather simple. Close the gap between the small-step semantics and the big-step semantics of Capla. The former is used for the proofs of type safety and compiler correctness, while the latter is used to prove the specification of Capla programs. But the formal relation between them has been proved in only one direction, which means that, while unlikely, the big-step semantics could be vacuously correct by accident, and thus the Capla programs would be too. This work item is purely at the semantics level and does not touch the compiler. It is unclear how difficult it is. Make it simpler to import Capla code inside Rocq to prove its correctness. Currently, the process involves passing a debug option to the compiler and moving some Rocq files around. Ideally, it should be possible to directly invoke the compiler from a Rocq session. This work item does not involve the semantics and the formal proofs, but it might require touching the implementation of Rocq. Software development in Rocq, development of specifications and proofs, software experimentation, writing documentation, contribution to the writing of scientific articles. Qualifications Knowledge about the semantics of programming languages and their implementation is required. Knowledge of the Rocq proof assistant or of a closely-related formal system (e.g., Lean), is required. Knowledge of French is not required. Avantages Partial reimbursement of public transport costs Leave: 7 weeks of annual leave + 10 extra days off due to RTT (statutory reduction in working hours) + possibility of exceptional leave (sick children, moving home, etc.) Possibility of teleworking (after 6 months of employment) and flexible organization of working hours Professional equipment available (videoconferencing, loan of computer equipment, etc.) Social, cultural and sports events and activities The candidate will be required to work with Guillaume Melquiond and also to participate in joint activities of the research team: joint seminar, working groups, etc. #J-18808-Ljbffr