Aggregated Metrics -average coverage, number of crashes, and execution time.

[harshtech123]

Aggregated Metrics

This will allow users to quickly compare the performance of different fuzzing strategies.

now should include accumulated_results , execution_time in json file .

should show average of coverage across the experiements, total no of crashes and execution time plus total no of crash cases

@DonggeLiu could you please take look, thank you !