README.md

The Coq Library of Complexity Theory

This library contains complexity theory formalised in the Coq proof assistant, developed at Saarland University and initiated by Fabian Kunze. It is built upon the Coq Library of Undecidability Proofs.

Content

Directory structure

• Complexity: basic notions of complexity theory, formulated for the call-by-value lambda calculus L
• HierarchyTheorem: the Time Hierarchy Theorem
• NP: NP hardness and completeness proofs
• NP/SAT: the Cook Levin Theorem
• L/AbstractMachines: universal machines for L and their computability and resource analysis
• L/TM: the L-computability of Turing machine related concepts
• TM: the TM-computability results and resource analysis of concrete TMs
• Libs: internal library files used in multiple other directories

Installation

Building from source

This library depends on the Coq Library of Undecidability Proofs version 1.0.1. See the installation instructions of this library. It will suffice to install the opam package coq-library-undecidability.1.0.1+8.16, for instance by opam install . --deps-only.

• make all builds the library and the dependencies
• make html generates clickable coqdoc .html in the website subdirectory
• make clean removes all build files in theories and .html files in the website directory

Troubleshooting

Version of Coq and dependencies

Be careful that this branch only compiles under Coq 8.16 and with the Coq Library of Undecidability Proofs, version 1.0.1. Newer versions of the library are not supported, in particular versions 1.1 and upwards are not supported.

Published work and technical reports

• Mechanising Complexity Theory: The Cook-Levin Theorem in Coq. Lennard Gäher, Fabian Kunze. ITP 2021. Subdirectory NP/SAT. https://doi.org/10.4230/LIPIcs.ITP.2021.20
• A Mechanised Proof of the Time Invariance Thesis for the Weak Call-By-Value λ-Calculus. Yannick Forster, Fabian Kunze, Gert Smolka, Maxi Wuttke. ITP 2021. Subdirectories L/TM and TM. https://doi.org/10.4230/LIPIcs.ITP.2021.19
• Formal Small-step Verification of a Call-by-value Lambda Calculus Machine. Fabian Kunze, Gert Smolka, and Yannick Forster. APLAS 2018. Subdirectory L/AbstractMachines. https://www.ps.uni-saarland.de/extras/cbvlcm2/
• The Weak Call-By-Value λ-Calculus is Reasonable for Both Time and Space.Yannick Forster, Fabian Kunze, Marc Roth. POPL 2020. Mechanised parts in L/AbstractMachines and SpaceboundsTime.v https://www.ps.uni-saarland.de/extras/wcbv-reasonable/

Related Papers and abstracts from the Coq Library of Undecidability Proofs

We make heavy use of the following results, which for technical reasons are oursourced to the Library of Undecidability Proofs.

We use two frameworks which ease computability proofs with resource analysis for call-by-value lambda-calculus and Turing machines:

• A certifying extraction with time bounds from Coq to call-by-value lambda-calculus. ITP '19. https://github.com/uds-psl/certifying-extraction-with-time-bounds
• Verified Programming of Turing Machines in Coq. Yannick Forster, Fabian Kunze, Maxi Wuttke. Technical report. https://github.com/uds-psl/tm-verification-framework/

Contributors

• Fabian Kunze, Saarland University (2017-2022)
• Lennard Gäher, Saarland University (2017-2021)
• Maxi Wuttke, Saarland University (2017-2021)
• Yannick Forster, Saarland University (2017-2019)
• Stefan Haan (2022)