Slicing Concurrent Constraint Programs

TL;DR

This paper introduces a dynamic slicing technique for Concurrent Constraint Programming (CCP) to help debug complex concurrent programs by isolating relevant parts of execution traces, including timed variants.

Contribution

It presents a novel dynamic slicer for CCP that simplifies debugging by focusing on bug-related computation parts, with a prototype implementation available.

Findings

Effective in isolating bug sources in CCP traces

Can be adapted for timed CCP variants

Prototype implementation demonstrates practical utility

Abstract

Concurrent Constraint Programming (CCP) is a declarative model for concurrency where agents interact by telling and asking constraints (pieces of information) in a shared store. Some previous works have developed (approximated) declarative debuggers for CCP languages. However, the task of debugging concurrent programs remains difficult. In this paper we define a dynamic slicer for CCP and we show it to be a useful companion tool for the existing debugging techniques. Our technique starts by considering a partial computation (a trace) that shows the presence of bugs. Often, the quantity of information in such a trace is overwhelming, and the user gets easily lost, since she cannot focus on the sources of the bugs. Our slicer allows for marking part of the state of the computation and assists the user to eliminate most of the redundant information in order to highlight the errors. We show that this technique can be tailored to timed variants of CCP. We also develop a prototypical implementation freely available for making experiments.