
94 Large Scale and Big Data
network, in-memory, and le channels. The network and in-memory channels allow
the PACT compiler to construct low-latency execution pipelines in which one task
can immediately consume the output of another. The le channels collect the entire
output of a task in a temporary le before passing its content on to the next task.
Therefore, le channels can be considered check points, which help to recover from
execution failures.
Due to the declarative character of the PACT programming model, the PACT
compiler can apply different optimization mechanisms and select from several exe-
cution plans with varying costs for a s ...