CODEWITHSUNDEEP
pythonparallel-processingjoblib
Amir
Amir

Reputation: 1428

How to parallelize this embarrassingly parallel loop with Python

I have an embarrassingly parallel loop:

# Definitions

def exhaustiveExplorationsWithSimilarityAll(inputFolder, outputFolder, similarityMeasure):
    phasesSpeedupDictFolder=parsePhasesSpeedupDictFolder(inputFolder)
    avgSpeedupProgramDict=computeAvgSpeedupProgram(phasesSpeedupDictFolder)
    parameters={
        PROGRAMSPHASESSPEEDUPDICTS:phasesSpeedupDictFolder,
        PROGRAMSAVGSPEEDUPDICT:avgSpeedupProgramDict
    }
similarityHandler= SimilarityHandler(similarityMeasure,parameters)



# Sequential running

for fileName in os.listdir(inputFolder):
    print fileName
    exhaustiveExplorationsWithSimilarity(inputFolder + fileName, outputFolder + fileName, similarityHandler)

and I would like to make it parallel using Joblib Parallel:

# Parallel version

num_cores = multiprocessing.cpu_count()

parallel= Parallel(n_jobs=num_cores)
    for fileName in os.listdir(inputFolder):
        print fileName
        parallel(delayed(exhaustiveExplorationsWithSimilarity(inputFolder + fileName, outputFolder + fileName, similarityHandler)))

OR other version:

arg_generator = ((inputFolder + fileName, outputFolder + fileName, similarityHandler) for fileName in os.listdir(inputFolder))
parallel(delayed(exhaustiveExplorationsWithSimilarity)(arg_generator))

But upon running it complaints with :

parallel(delayed(exhaustiveExplorationsWithSimilarity(inputFolder + fileName, outputFolder + fileName, similarityHandler)))
  File "/usr/lib/pymodules/python2.7/joblib/parallel.py", line 516, in __call__
    for function, args, kwargs in iterable:
TypeError: 'function' object is not iterable

What am I missing here? Any help is appreciated.

Upvotes: 0

Views: 2709

Answers (1)

Tom Dalton
Tom Dalton

Reputation: 6190

You are still calling exhaustiveExplorationsWithSimilarity (serially) inside your loop, but then you are passing the result to delayed

From the docs https://pythonhosted.org/joblib/parallel.html#common-usage, it looks like you need to do something like:

parallel = Parallel(n_jobs=num_cores)
parallel(delayed(exhaustiveExplorationsWithSimilarity)(inputFolder + fileName, outputFolder + fileName, similarityHandler) for fileName in os.listdir(inputFolder))

Upvotes: 1

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