# 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 "echo performance >/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor"
print "echo performance >/sys/devices/system/cpu/cpu1/cpufreq/scaling_governor"

# 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.
    print "(time (tar xjf /usr/src/linux-source-2.6.28.tar.bz2; rm -rf linux-source-2.6.28)) 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 "echo ondemand >/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor"
print "echo ondemand >/sys/devices/system/cpu/cpu1/cpufreq/scaling_governor"