2012 | OriginalPaper | Chapter
Renaming Is Weaker Than Set Agreement But for Perfect Renaming: A Map of Sub-consensus Tasks
Authors : Armando Castañeda, Damien Imbs, Sergio Rajsbaum, Michel Raynal
Published in: LATIN 2012: Theoretical Informatics
Publisher: Springer Berlin Heidelberg
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In the
wait-free
shared memory model substantial attention has been devoted to understanding the relative power of
sub-consensus
tasks. Two important sub-consensus families of tasks have been identified:
k
-set agreement and
M
-renaming. When 2 ≤
k
≤
n
− 1 and
n
≤
M
≤ 2
n
− 2, these tasks are more powerful than read/write registers, but not strong enough to solve consensus for two processes.
This paper studies the power of renaming with respect to set agreement. It shows that, in a system of
n
processes,
n
-renaming is strictly stronger than (
n
− 1)-set agreement, but not stronger than (
n
− 2)-set agreement. Furthermore, (
n
+ 1)-renaming cannot solve even (
n
− 1)-set agreement. As a consequence, there are cases where set agreement and renaming are incomparable when looking at their power to implement each other.