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Parallel Execution Time

1. Computation Time $T$_comp

   Time spent performing actual computation; may depend on number of tasks or processors (replicated computation, memory and cache effects).

2. Communication Time $T$_msg
   • Time spent in sending and receiving messages
   • $T$_msg = t_s + t_w L
   • startup cost, cost/word, message length.
3. Idle Time $T$_idle
   • Processor idle due to lack of computation or lack of data,
   • Load balancing,
   • Overlapping computation with communication.