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			     I N R I A - Paris
                 2 rue Simone Iff (ou: 41 rue du Charolais)
                            Salle A215, bâtiment A

                            MARDI 7 janvier, 10h30

                               ---------------
                               Lionel Parreaux
                               ---------------

                                     EPFL

            ======================================================
                           Partial Graph Reduction:
            A New Optimization Technique for Higher-Order Programs
            ======================================================

Inlining is a crucial compiler optimization which is used to uncover new
optimization opportunities, helping to remove the cost of abstraction. Yet,
too much inlining leads to code explosion, making compilation slow and
producing large binaries. Moreover, inlining falls short given the task of
optimizing recursive functions. Taking inspiration from optimal reduction, I
will present a new graph-based 'partial reduction' technique, that reliably
inlines just enough of a function's body to optimize it within its calling
contexts. I will talk about a prototype implementation of that approach as a
Haskell optimizer, and explain how it generalizes previous techniques and
facilitates optimizations such as list fusion.

Bio

Lionel Parreaux is a Ph.D. candidate at EPFL working with Christoph Koch on
programming languages, compilers, and database technology. After discovering
Scala's flexibility and expressive power, Lionel set out to create Squid, a
Scala metaprogramming framework. Squid joins theory and practice to unlock the
great promises of multi-stage programming, advanced compiler techniques, and
domain-specific optimization. The core of Squid's type system was presented at
POPL 2018, and papers on applications of Squid have been published at GPCE
2017 (receiving best paper award) and ECOOP 2019. Lionel interned at Microsoft
Research Cambridge in 2018, where he started a collaboration with Simon Peyton
Jones on a novel graph-based intermediate representation for optimizing
functional programs.