We show that the parameterized problem Perfect Code belongs to W[1].
This result closes an old open question, because it was often
conjectured that Perfect Code could be a natural problem having
complexity degree intermediate between W[1] and W[2]. This result
also shows W[1]-membership of the parameterized problem Weighted
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We consider the framework of Parameterized Complexity, and we
investigate the issue of which problems do admit efficient fixed
parameter parallel algorithms by introducing two different
degrees of efficiently parallelizable parameterized problems, PNC
and FPP. We sketch both some FPP-algorithms solving natural
parameterized problems and ... more >>>

A polynomial time approximation scheme (PTAS) for an optimization
problem $A$ is an algorithm that on input an instance of $A$ and
$\epsilon > 0$ finds a $(1+\epsilon)$-approximate solution in time
that is polynomial for each fixed $\epsilon$. Typical running times
are $n^{O(1/\epsilon)}$ or $2^{1/\epsilon^{O(1)}} ... more >>>