#13501: Fix two bugs in sage.misc.c3's implementation of the algorithm C3
-------------------------------------------+--------------------------------
Reporter: nthiery | Owner: nthiery
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.4
Component: categories | Resolution:
Keywords: method resolution order | Work issues:
Report Upstream: N/A | Reviewers: Simon King
Authors: Nicolas M. Thiéry | Merged in:
Dependencies: #12895 | Stopgaps:
-------------------------------------------+--------------------------------
Comment (by SimonKing):
With a little cdef'ing, namely
{{{#!diff
diff --git a/sage/misc/c3.pyx b/sage/misc/c3.pyx
--- a/sage/misc/c3.pyx
+++ b/sage/misc/c3.pyx
@@ -196,6 +196,8 @@
nbheads = len(heads)
cdef object O, X
cdef bint next_item_found
+ cdef set tail_set
+ cdef list tail_list
while nbheads:
for i from 0 <= i < nbheads:
@@ -205,7 +207,8 @@
for j from 0 <= j < nbheads:
if j == i:
continue
- if O in tailsets[j]:
+ tail_set = tailsets[j]
+ if O in tail_set:
next_item_found = False
break
if next_item_found:
@@ -215,11 +218,13 @@
# j goes down so that ``del heads[j]`` does not screw up
the numbering
for j from nbheads > j >= 0:
if heads[j] is O:
- try:
- X = tails[j].pop()
+ tail_list = tails[j]
+ if tail_list:
+ X = tail_list.pop()
heads[j] = X
- tailsets[j].remove(X)
- except IndexError:
+ tail_set = tailsets[j]
+ tail_set.remove(X)
+ else:
del heads[j]
del tails[j]
del tailsets[j]
}}}
I get
{{{
ncalls tottime percall cumtime percall filename:lineno(function)
7000/500 0.277 0.000 0.819 0.002 {sage.misc.c3.C3_algorithm}
}}}
The differences really are tiny. However, here is why I removed the `try:
... except IndexError:`:
{{{
sage: cython("""
....: def test1(list L):
....: cdef list l
....: for l in L:
....: try:
....: l.pop()
....: except IndexError:
....: l.append(0)
....: def test2(list L):
....: cdef list l
....: for l in L:
....: if l:
....: l.pop()
....: else:
....: l.append(0)
....: """)
sage: L = [[] for _ in range(10000)]
sage: %timeit test1(L)
125 loops, best of 3: 7.07 ms per loop
sage: L = [[] for _ in range(10000)]
sage: %timeit test2(L)
125 loops, best of 3: 1.94 ms per loop
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13501#comment:16>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/sage-trac?hl=en.
