python - multithreading performance issue -


possible duplicate: multithreading performance overhead

i have piece of code run slower on multithread , faster while using 1 thread.

output 1 thread:

batch 0 finished in 0.0970576110595 batch 1 finished in 0.712632355587 batch 2 finished in 2.16707853982 batch 3 finished in 5.13259954359 batch 4 finished in 9.54205263734  total running time approx 17second

output using multi-thread

thread 0 finished in 60.4911733611 thread 1 finished in 62.5297083217 thread 2 finished in 65.5614617838 thread 3 finished in 66.8199233683 thread 4 finished in 66.8426577103  total running time 66 second.

what being done in each process take 100 lines of text, split tokens, remove stopwords , generate patterns using algorithm, have experience or ways me identify went wrong?

@mac's answer covers why, we'll need of code give more help. may want try, use multiprocessing instead of threading, have data access issues...

threading in python on non-blocking io you have 1 active thread per python process.

multiprocessing useful making use of cores, start have worry locks , race conditions , else.


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