[pypy-commit] pypy improve-rbigint: Speedup floordiv by the power of two

[stian]

Author: stian
Branch: improve-rbigint
Changeset: r56327:0d3da1111129
Date: 2012-06-24 22:30 +0200
http://bitbucket.org/pypy/pypy/changeset/0d3da1111129/

Log:	Speedup floordiv by the power of two

diff --git a/pypy/rlib/rbigint.py b/pypy/rlib/rbigint.py
--- a/pypy/rlib/rbigint.py
+++ b/pypy/rlib/rbigint.py
@@ -412,6 +412,15 @@
         return div
 
     def floordiv(self, other):
+        if other.numdigits() == 1 and other.sign == 1:
+            digit = other.digit(0)
+
+            if digit == 1:
+                return self
+            elif digit & (digit - 1) == 0:
+                div = self.rshift(ptwotable[digit])
+                return div
+            
         div, mod = self.divmod(other)
         return div
 
diff --git a/pypy/translator/goal/targetbigintbenchmark.py b/pypy/translator/goal/targetbigintbenchmark.py
--- a/pypy/translator/goal/targetbigintbenchmark.py
+++ b/pypy/translator/goal/targetbigintbenchmark.py
@@ -10,6 +10,7 @@
     """
         A cutout with some benchmarks.
         Pypy default:
+        5.147583
         484.5688
         334.611903
         8.637287
@@ -21,6 +22,7 @@
         6.647562
 
         Pypy with improvements:
+        2.307890
         9.451896
         1.122038
         5.787821
@@ -32,6 +34,14 @@
         6.434917
 
     """
+
+    t = time()
+    num = rbigint.fromint(100000000)
+    for n in xrange(80000000):
+        rbigint.floordiv(num, rbigint.fromint(2))
+        
+
+    print time() - t
     
     t = time()
     num = rbigint.fromint(10000000)