CODEWITHSUNDEEP
multithreadingperformancetheory
user837208
user837208

Reputation: 2577

multi-threading theoretical scenario

I've a multi-threaded application which uses a threadpool of 10 threads. Each thread takes 5 minutes to process input. Is there a law/formula which governs the total time taken to process n inputs?

In other words, is it right to say that every 5 minutes, 10 inputs can be processed, so to process 100 inputs, it will take 50 minutes?

Upvotes: 0

Views: 114

Answers (2)

Han Zhou
Han Zhou

Reputation: 416

In addition to the computing power (processors/cores) and hardware resource dependencies (hard disk, I/O competition, etc.), the data dependency should also be considered. For example, if the processing of each input includes updating a shared data by all the other threads, which requires locking (mutex), then the total throughput will be less than 10 times, even if it is a multi-core processor with more than 10 cores. The maximum speed-up depends on the proportion of the critical section. If you need a formula, refer to the famous Amdahl's law: en.wikipedia.org/wiki/Amdahl's_law

Upvotes: 2

Francis Upton IV
Francis Upton IV

Reputation: 19443

Not really, you have to consider the total computing power required. If for example a thread takes 5 minutes to do the work, and the processor is completely consumed during that time, then additional threads will not help you. On the other extreme, if the processor utilization is near zero (all of the time is spent waiting for I/O for example), then your proposed calculation would work. So you have to consider the actual resources being used by the computation.

Upvotes: 1

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