utils/create_ladder_graph.py

   1 #!/usr/bin/env python
   2 """A ladder graph creation program.
   3
   4 This is a python program that creates c source code that will generate
   5 CFGs that are ladder graphs.  Ladder graphs are generally the worst case
   6 for a lot of dominance related algorithms (Dominance frontiers, etc),
   7 and often generate N^2 or worse behavior.
   8
   9 One good use of this program is to test whether your linear time algorithm is
  10 really behaving linearly.
  11 """
  12
  13 from __future__ import print_function
  14
  15 import argparse
  16 def main():
  17   parser = argparse.ArgumentParser(description=__doc__)
  18   parser.add_argument('rungs', type=int,
  19                       help="Number of ladder rungs. Must be a multiple of 2")
  20   args = parser.parse_args()
  21   if (args.rungs % 2) != 0:
  22     print("Rungs must be a multiple of 2")
  23     return
  24   print("int ladder(int *foo, int *bar, int x) {")
  25   rung1 = range(0, args.rungs, 2)
  26   rung2 = range(1, args.rungs, 2)
  27   for i in rung1:
  28     print("rung1%d:" % i)
  29     print("*foo = x++;")
  30     if i != rung1[-1]:
  31       print("if (*bar) goto rung1%d;" % (i+2))
  32       print("else goto rung2%d;" % (i+1))
  33     else:
  34       print("goto rung2%d;" % (i+1))
  35   for i in rung2:
  36     print("rung2%d:" % i)
  37     print("*foo = x++;")
  38     if i != rung2[-1]:
  39       print("goto rung2%d;" % (i+2))
  40     else:
  41       print("return *foo;")
  42   print("}")
  43
  44 if __name__ == '__main__':
  45   main()