# The following variable controls the number of runs that will
#  be done in each of the two experimental conditions.
repetitions = 20

# Start by making a list of 0s and 1s, which then is randomized.
# Before randomization, settings = [0, 0, 0, ..., 1, 1, 1, ...].
settings = repetitions*[0] + repetitions*[1]

# Now we shuffle settings into a random order
# This makes it the basic schedule of our experimental runs,
#  at the level of 0s and 1s, without the details of what those mean.
import random
random.shuffle(settings)

# We print out a shell script (to run with bash) that will conduct
#  the experiment.

# First, we print some commands to be done just once,  before the runs.

# Arrange that timing results show the total elapsed (real) time in
#  decimal form, as a number of seconds.
print("TIMEFORMAT=%R")

# Output a heading line indicating what the two columns are in the
#  CSV (comma separated values) output that this script produces.
print("echo buffering,time")

# For repeatability's sake, keep the clock rates at their maximum values.
# (Any other commands to do just once that enhance repeatability would
#  go here too.)
print("for f in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor")
print("do")
print("   echo performance >$f")
print("done")

# Now we are ready to loop through the various experimental runs, putting
#  the appropriate commands for each into the script.
for s in settings:
    # Output the buffering setting to the script's CSV output.
    print("echo -n "+str(s)+",")
    # For repeatability's sake, before doing each timing run,
    #  push all deferred output to disk and then drop
    #  from memory all pages and other file-related structures.
    print("sync")
    print("echo 3 >/proc/sys/vm/drop_caches")
    # Put the buffering setting into effect.
    print("hdparm -q -W"+str(s)+" /dev/sda")
    # Time a workload consisting of unpacking the Linux source code
    #  and then removing the resulting directory tree. The workload
    #  ends with a sync command to make sure we include in the timing
    #  all activity needed to actually make the disk reflect the complete
    #  unpacking and removal, rather than some of the work still being
    #  left outstanding to be caught up with later outside the timing.
    print("(time (tar xzf linux_3.8.0.orig.tar.gz; rm -rf linux-3.8; sync)) 2>&1")

# Now we print out the commands that should go in the script just once
#  after all the experimental runs are over.

# In case the last experimental run left the hard disk buffering turned
#  off, turn it back on (so the system will run normally hereafter).
print("hdparm -q -W1 /dev/sda")

# Since we no longer need repeatable performance, we can revert back
#  to the normal power-savings mode where the clock rate varies.
print("for f in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor")
print("do")
print("   echo ondemand >$f")
print("done")