Lazy and Speculative Execution

15 January 2007

Lampson: Lazy and Speculative Execution

Lazy: Stream Processing

nIn database queries, Unix pipes, etc.,

oApply functions to unbounded sequences of data

▬f must be pointwise: f (seq) = g(seq.head) Å f (seq.tail)

oRearrange the computation to apply several functions to each data item in turn

▬If f and g are pointwise, so is f ◦ g

oSometimes fails, as in piping to sort

nThe bet: don’t need the whole stream

nAlways a big win in latency

oIn fact, it can handle infinite structures