Proof Ground 2020: Call for Problems

Dear Coq enthusiasts,

I’m forwarding this call for interesting verification puzzles, on behalf of the Proof Ground organizers:

Call for Problems

Proof Ground 2020
Interactive Proving Contest
June 29, 2020

at IJCAR 2020
International Joint Conference on Automated Reasoning
June 29 - July 5, 2020, (originally in) Paris, France, now fully virtual

This workshop brings together researchers of the ITP community to compete in a “proving contest”.
While programming contests (e.g. ACM ICPC, International Olympiad in Informatics) challenge large numbers of participants to solve algorithmic problems within a short time, we envision proving contests
to entice proof engineers to formally prove small but interesting problems from mathematics or computer science.

A contest system ( is currently used for teaching and hosting proving contests in Coq, Isabelle, and Lean.

Proof Ground 2020 is part of the Paris Nord Summer of LoVe 2020 (, a joint event on LOgic and VErification at Université Paris 13, made of Petri Nets 2020, IJCAR 2020, FSCD 2020, and over 20 satellite events.

As the main conferences of Paris Nord Summer of LoVe will happen as virtual conferences due to the Covid-19 outbreak, Proof Ground will also take a purely virtual format.
The first edition ( of the workshop has been held at ITP 2019 (

Important Dates:
Submission deadline: June 1, 2020
Workshop and Competition: June 27, 2020

Call for Problems:

In order to conduct a stimulating contest we solicit interesting tasks. A contest typically lasts for two hours and consists of around five problems with varying difficulty.

A problem:

  • should contain an informal statement of the problem together with a template for the formal proof;
  • should come with a reference solution (in any ITP);
  • should be solvable (including formal proof) within 30 minutes;
  • should be easy to state in any proof assistant, without requiring too much background library;
  • could be from any part of mathematics, software verification, or your daily work with ITPs, and could also be a logic puzzle/riddle;
  • could contain several subproblems which lead to partial points.

Submissions from (potential) competition participants are allowed. Examples can be found at the current “Proving for Fun” contest system, e.g. here (

Submissions can be made via email to wimmers [at] in [dot] tum [dot] de by the date indicated above.

Maximilian P. L. Haslbeck
Tobias Nipkow
Simon Wimmer

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