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#!/usr/bin/env python
"""A ladder graph creation program.
This is a python program that creates c source code that will generate
CFGs that are ladder graphs. Ladder graphs are generally the worst case
for a lot of dominance related algorithms (Dominance frontiers, etc),
and often generate N^2 or worse behavior.
One good use of this program is to test whether your linear time algorithm is
really behaving linearly.
"""
import argparse
def main():
parser = argparse.ArgumentParser(description=__doc__)
parser.add_argument('rungs', type=int,
help="Number of ladder rungs. Must be a multiple of 2")
args = parser.parse_args()
if (args.rungs % 2) != 0:
print "Rungs must be a multiple of 2"
return
print "int ladder(int *foo, int *bar, int x) {"
rung1 = xrange(0, args.rungs, 2)
rung2 = xrange(1, args.rungs, 2)
for i in rung1:
print "rung1%d:" % i
print "*foo = x++;"
if i != rung1[-1]:
print "if (*bar) goto rung1%d;" % (i+2)
print "else goto rung2%d;" % (i+1)
else:
print "goto rung2%d;" % (i+1)
for i in rung2:
print "rung2%d:" % i
print "*foo = x++;"
if i != rung2[-1]:
print "goto rung2%d;" % (i+2)
else:
print "return *foo;"
print "}"
if __name__ == '__main__':
main()
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