Make threshold toggleable

tools/profiling/microbenchmarks/bm_diff/bm_diff.py

@@ -108,7 +108,7 @@ class Benchmark:
       mdn_diff = abs(_median(new) - _median(old))
       _maybe_print('%s: %s=%r %s=%r mdn_diff=%r' %
              (f, new_name, new, old_name, old, mdn_diff))
-      s = bm_speedup.speedup(new, old)
+      s = bm_speedup.speedup(new, old, 1e-10)
       if abs(s) > 3 and mdn_diff > 0.5:
         self.final[f] = '%+d%%' % s
     return self.final.keys()

tools/profiling/microbenchmarks/bm_diff/bm_speedup.py

@@ -17,8 +17,6 @@
 from scipy import stats
 import math
 
-_THRESHOLD = 1e-10
-
 
 def scale(a, mul):
   return [x * mul for x in a]
@@ -28,18 +26,18 @@ def cmp(a, b):
   return stats.ttest_ind(a, b)
 
 
-def speedup(new, old):
+def speedup(new, old, threshold):
   if (len(set(new))) == 1 and new == old: return 0
   s0, p0 = cmp(new, old)
   if math.isnan(p0): return 0
   if s0 == 0: return 0
-  if p0 > _THRESHOLD: return 0
+  if p0 > threshold: return 0
   if s0 < 0:
     pct = 1
     while pct < 101:
       sp, pp = cmp(new, scale(old, 1 - pct / 100.0))
       if sp > 0: break
-      if pp > _THRESHOLD: break
+      if pp > threshold: break
       pct += 1
     return -(pct - 1)
   else:
@@ -47,7 +45,7 @@ def speedup(new, old):
     while pct < 100000:
       sp, pp = cmp(new, scale(old, 1 + pct / 100.0))
       if sp < 0: break
-      if pp > _THRESHOLD: break
+      if pp > threshold: break
       pct += 1
     return pct - 1