listsort. If the former calls itself recursively, they're a waste of
time, since it's called on a random permutation of a random subset of
elements. OTOH, for exactly the same reason, they're an immeasurably
small waste of time (the odds of finding exploitable order in a random
permutation are ~= 0, so the special-case loops looking for order give
up quickly). The point is more for conceptual clarity.
Also changed some "assert comments" into real asserts; when this code
was first written, Python.h didn't supply assert.h.
introduced, list.sort() was rewritten to use only the "< or not <?"
distinction. After rich comparisons were introduced, docompare() was
fiddled to translate a Py_LT Boolean result into the old "-1 for <,
0 for ==, 1 for >" flavor of outcome, and the sorting code was left
alone. This left things more obscure than they should be, and turns
out it also cost measurable cycles.
So: The old CMPERROR novelty is gone. docompare() is renamed to islt(),
and now has the same return conditinos as PyObject_RichCompareBool. The
SETK macro is renamed to ISLT, and is even weirder than before (don't
complain unless you want to maintain the sort code <wink>).
Overall, this yields a 1-2% speedup in the usual (no explicit function
passed to list.sort()) case when sorting arrays of floats (as sortperf.py
does). The boost is higher for arrays of ints.
The staticforward define was needed to support certain broken C
compilers (notably SCO ODT 3.0, perhaps early AIX as well) botched the
static keyword when it was used with a forward declaration of a static
initialized structure. Standard C allows the forward declaration with
static, and we've decided to stop catering to broken C compilers. (In
fact, we expect that the compilers are all fixed eight years later.)
I'm leaving staticforward and statichere defined in object.h as
static. This is only for backwards compatibility with C extensions
that might still use it.
XXX I haven't updated the documentation.
it_seq field when the end of the list is reached.
Also remove the next() method -- one is supplied automatically by
PyType_Ready() because the tp_iternext slot is set. That's a good
thing, because the implementation given here was buggy (it never
raised StopIteration).
explicit comparison function case: use PyObject_Call instead of
PyEval_CallObject. Same thing in context, but gives a 2.4% overall
speedup when sorting a list of ints via list.sort(__builtin__.cmp).
arg tuple. This was suggested on c.l.py but afraid I can't find the msg
again for proper attribution. For
list.sort(cmp)
where list is a list of random ints, and cmp is __builtin__.cmp, this
yields an overall 50-60% speedup on my Win2K box. Of course this is a
best case, because the overhead of calling cmp relative to the cost of
actually comparing two ints is at an extreme. Nevertheless it's huge
bang for the buck. An additionak 20-30% can be bought by making the arg
tuple an immortal static (avoiding all but "the first" PyTuple_New), but
that's tricky to make correct since docompare needs to be reentrant. So
this picks the cherry and leaves the pits for Fred <wink>.
Note that this makes no difference to the
list.sort()
case; an arg tuple gets built only if the user specifies an explicit
sort function.
[ 400998 ] experimental support for extended slicing on lists
somewhat spruced up and better tested than it was when I wrote it.
Includes docs & tests. The whatsnew section needs expanding, and arrays
should support extended slices -- later.
A MemoryError is now raised when the list cannot be created.
There is a test, but as the comment says, it really only
works for 32 bit systems. I don't know how to improve
the test for other systems (ie, 64 bit or systems
where the data size != addressable size,
e.g. 64 bit data, but 48 bit addressable memory)
The fix makes it possible to call PyObject_GC_UnTrack() more than once
on the same object, and then move the PyObject_GC_UnTrack() call to
*before* the trashcan code is invoked.
BUGFIX CANDIDATE!
Rather than tweaking the inheritance of type object slots (which turns
out to be too messy to try), this fix adds a __hash__ to the list and
dict types (the only mutable types I'm aware of) that explicitly
raises an error. This has the advantage that list.__hash__([]) also
raises an error (previously, this would invoke object.__hash__([]),
returning the argument's address); ditto for dict.__hash__.
The disadvantage for this fix is that 3rd party mutable types aren't
automatically fixed. This should be added to the rules for creating
subclassable extension types: if you don't want your object to be
hashable, add a tp_hash function that raises an exception.
Also, it's possible that I've forgotten about other mutable types for
which this should be done.
many types were subclassable but had a xxx_dealloc function that
called PyObject_DEL(self) directly instead of deferring to
self->ob_type->tp_free(self). It is permissible to set tp_free in the
type object directly to _PyObject_Del, for non-GC types, or to
_PyObject_GC_Del, for GC types. Still, PyObject_DEL was a tad faster,
so I'm fearing that our pystone rating is going down again. I'm not
sure if doing something like
void xxx_dealloc(PyObject *self)
{
if (PyXxxCheckExact(self))
PyObject_DEL(self);
else
self->ob_type->tp_free(self);
}
is any faster than always calling the else branch, so I haven't
attempted that -- however those types whose own dealloc is fancier
(int, float, unicode) do use this pattern.
Gave Python linear-time repr() implementations for dicts, lists, strings.
This means, e.g., that repr(range(50000)) is no longer 50x slower than
pprint.pprint() in 2.2 <wink>.
I don't consider this a bugfix candidate, as it's a performance boost.
Added _PyString_Join() to the internal string API. If we want that in the
public API, fine, but then it requires runtime error checks instead of
asserts.
resizing.
Accurate timings are impossible on my Win98SE box, but this is obviously
faster even on this box for reasonable list.append() cases. I give
credit for this not to the resizing strategy but to getting rid of integer
multiplication and divsion (in favor of shifting) when computing the
rounded-up size.
For unreasonable list.append() cases, Win98SE now displays linear behavior
for one-at-time appends up to a list with about 35 million elements. Then
it dies with a MemoryError, due to fatally fragmented *address space*
(there's plenty of VM available, but by this point Win9X has broken user
space into many distinct heaps none of which has enough contiguous space
left to resize the list, and for whatever reason Win9x isn't coalescing
the dead heaps). Before the patch it got a MemoryError for the same
reason, but once the list reached about 2 million elements.
Haven't yet tried on Win2K but have high hopes extreme list.append()
will be much better behaved now (NT & Win2K didn't fragment address space,
but suffered obvious quadratic-time behavior before as lists got large).
For other systems I'm relying on common sense: replacing integer * and /
by << and >> can't plausibly hurt, the number of function calls hasn't
changed, and the total operation count for reasonably small lists is about
the same (while the operations are cheaper now).
This fixes SF bug #132008, reported by Warren J. Hack.
The copyright for this patch (and this patch only) belongs to CNRI, as
part of the (yet to be issued) 1.6.1 release.
This is now checked into the HEAD branch. Tim will check in a test
case to check for this specific bug, and an assertion in
PyArgs_ParseTuple() to catch similar bugs in the future.
- sort's docompare() calls RichCompare(Py_LT).
- list_contains(), list_index(), listcount(), listremove() call
RichCompare(Py_EQ).
- Get rid of list_compare(), in favor of new list_richcompare(). The
latter does some nice shortcuts, like when == or != is requested, it
first compares the lengths for trivial accept/reject. Then it goes
over the items until it finds an index where the items differe; then
it does more shortcut magic to minimize the number of additional
comparisons.
- Aligned the comments for large struct initializers.
Add definitions of INT_MAX and LONG_MAX to pyport.h.
Remove includes of limits.h and conditional definitions of INT_MAX
and LONG_MAX elsewhere.
This closes SourceForge patch #101659 and bug #115323.
Michael W. Hudson
Martin v. Löwis
Tim Peters
Jeremy Hylton
Guido van Rossum
Neal Norwitz
Raymond Hettinger
Neil Schemenauer
Fred Drake
Thomas Wouters
Jack Jansen
Trent Mick
Vladimir Marangozov