scholarly journals A complexity theory for hard enumeration problems

2019 ◽  
Vol 268 ◽  
pp. 191-209 ◽  
Author(s):  
Nadia Creignou ◽  
Markus Kröll ◽  
Reinhard Pichler ◽  
Sebastian Skritek ◽  
Heribert Vollmer
Algorithms ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 189 ◽  
Author(s):  
Nadia Creignou ◽  
Raïda Ktari ◽  
Arne Meier ◽  
Julian-Steffen Müller ◽  
Frédéric Olive ◽  
...  

Recently, Creignou et al. (Theory Comput. Syst. 2017), introduced the class Delay FPT into parameterised complexity theory in order to capture the notion of efficiently solvable parameterised enumeration problems. In this paper, we propose a framework for parameterised ordered enumeration and will show how to obtain enumeration algorithms running with an FPT delay in the context of general modification problems. We study these problems considering two different orders of solutions, namely, lexicographic order and order by size. Furthermore, we present two generic algorithmic strategies. The first one is based on the well-known principle of self-reducibility and is used in the context of lexicographic order. The second one shows that the existence of a neighbourhood structure among the solutions implies the existence of an algorithm running with FPT delay which outputs all solutions ordered non-decreasingly by their size.


2009 ◽  
Author(s):  
Michele B. Hill ◽  
Gregory L. Brack ◽  
Lydia Odenat
Keyword(s):  

1990 ◽  
Vol 10 (4) ◽  
pp. 396-401
Author(s):  
Zhenyu Wang ◽  
Chaoyi Sun
Keyword(s):  

Author(s):  
Luca SIMEONE ◽  
David DRABBLE ◽  
Giorgia IACOPINI ◽  
Kirsten VAN DAM ◽  
Nicola MORELLI ◽  
...  

In today’s world of global wicked problems, constraints and imperatives imposed by an external and uncertain environment render strategic action a quite complex endeavour. Since the 1990s, within community initiatives and philanthropic projects, the construct of Theory of Change has been used to address such complexity. Theory of Change can be defined as the systematic and cumulative study of the links between the activities, outcomes, and context of an intervention. The area of focus for this paper is to explore whether Theory of Change can support more strategic approaches in design. In particular, the paper examines how Theory of Change was applied to DESIGNSCAPES - a project oriented, among other things, toward offering a supporting service for all those city actors interested in using design to develop urban innovation initiatives that tackle complex issues of broad concern.


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