High energy & nuclear physics

• Speed-up:

• if TS is the best time to process a problem sequentially,
• then the parallel processing time should be TP=TS/P with P processors
• speedup = TS/TP
• the speedup is limited by Amdhal law: any parallel program has a purely sequential and a parallelizable part TS= F + T//,
• thus the speedup is limited: S = (F + T//) / (F + (T///P)) < P

• Scale-up:

• if TPS is the time to solve a problem of size S with P processors,
• then TPS should also be the time to process a problem of size n*S with n*P processors

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• 8000 Physicists, 170 Sites, 34 Countries

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