  We study the spacial and temporal multiscale properties of complex systems.
We present accelerated algorithms for dilute spin glasses and display
explicitly their relation to the effective dynamics of specific collective
degrees of freedom (macros).
  We discuss the difficulties in applying multiscale-cluster algorithms(MCA) to
general frustrated systems: MCA does not succeed to break the system into
clusters. We relate these difficulties to rigorous negative results in systems
with an ultrametric space of ground states: the tunneling between vacua cannot
be expressed into an algorithm acting upon independent macros.
