Fix ttest_ind crash

tools/profiling/microbenchmarks/bm_diff/bm_speedup.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python2.7
 # Copyright 2017, Google Inc.
 # All rights reserved.
 #
@@ -41,7 +42,9 @@ def cmp(a, b):
   return stats.ttest_ind(a, b)
 
 def speedup(new, old):
+  if (len(set(new))) == 1 and new == old: return 0
   s0, p0 = cmp(new, old)
+  print s0, p0
   if math.isnan(p0): return 0
   if s0 == 0: return 0
   if p0 > _THRESHOLD: return 0
@@ -49,6 +52,7 @@ def speedup(new, old):
     pct = 1
     while pct < 101:
       sp, pp = cmp(new, scale(old, 1 - pct/100.0))
+      print sp, pp
       if sp > 0: break
       if pp > _THRESHOLD: break
       pct += 1
@@ -57,13 +61,14 @@ def speedup(new, old):
     pct = 1
     while pct < 100000:
       sp, pp = cmp(new, scale(old, 1 + pct/100.0))
+      print sp, pp
       if sp < 0: break
       if pp > _THRESHOLD: break
       pct += 1
     return pct - 1
 
 if __name__ == "__main__":
-  new=[66034560.0, 126765693.0, 99074674.0, 98588433.0, 96731372.0, 110179725.0, 103802110.0, 101139800.0, 102357205.0, 99016353.0, 98840824.0, 99585632.0, 98791720.0, 96171521.0, 95327098.0, 95629704.0, 98209772.0, 99779411.0, 100182488.0, 98354192.0, 99644781.0, 98546709.0, 99019176.0, 99543014.0, 99077269.0, 98046601.0, 99319039.0, 98542572.0, 98886614.0, 72560968.0]
-  old=[60423464.0, 71249570.0, 73213089.0, 73200055.0, 72911768.0, 72347798.0, 72494672.0, 72756976.0, 72116565.0, 71541342.0, 73442538.0, 74817383.0, 73007780.0, 72499062.0, 72404945.0, 71843504.0, 73245405.0, 72778304.0, 74004519.0, 73694464.0, 72919931.0, 72955481.0, 71583857.0, 71350467.0, 71836817.0, 70064115.0, 70355345.0, 72516202.0, 71716777.0, 71532266.0]
+  new=[1.0, 1.0, 1.0, 1.0]
+  old=[2.0, 2.0, 2.0, 2.0]
   print speedup(new, old)
   print speedup(old, new)