CODEWITHSUNDEEP
python
jsguy
jsguy

Reputation: 2179

Python: kill the application if subprocess.check_output waits too long to receive the output

I have implemented a cache oblivious algorithm and have shown with the PAPI library that the L1/L2/L3 misses are very low. However I would also like to see how the algorithm behaves if I reduce the available RAM memory and force the algorithm to start using the swap space in the disk. Since the algorithm is cache oblivious, I should expect a much better scaling to the disk compared to other non cache oblivious algorithms for the same problem.

The problem however is that it is very hard to predict how bad the algorithms will perform once out on the disk; a small increase in the input size might dramatically change the time that it takes for the algorithm to finish running. So if you have many algorithms that you want to test, if one takes forever to finish then the experiment will be useless (I could of course sit and monitor the experiment and kill if with ctrl+c, but I really need to sleep).

Let's say the algorithms are A,B and C. I use a different python script, one for each algorithm. For varying input size n I use subprocess.check_output to call the executable of the implementation. This executable returns some statistics that I then process and store in a suitable format that I can then use with R for example to make some nice plots.

This is an example code for algorithm A:

import subprocess
import sys
f1=open('data.stats', 'w+', 1)
min = 200000
max = 2000000
step = 200000
iterations = 10
ns = range(minLeafs, maxLeafs+1, step)
incr = 0
f1.write('n\tp\talg\ttime\n')
for n in ns:
    i = 0
    for p in ps:
        for it in range(0, iterations):
            resA = subprocess.check_output(['/usr/bin/time', '-v','./A',n],
            stderr=subprocess.STDOUT)
            #do something with resA
            f1.write(resA + '\n')
            incr = incr + 1
            print(incr/(((len(ns)))*iterations)*100.0, '%', end="\r")
        i = i + 1

My question is, can I somehow kill a script if subprocess.check_outputtakes too long to receive an answer? The best thing would for me to define a cut off, like 10 minutes, so if subprocess.check_output hasn't received anything, then kill the entire script.

Upvotes: 0

Views: 106

Answers (1)

Gareth Pulham
Gareth Pulham

Reputation: 654

If you're using Python 3 (and the format of your call to print suggests you might be), then check_output actually already has a timeout argument that might be useful to you: https://docs.python.org/3.6/library/subprocess.html#subprocess.check_output

Upvotes: 1

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