SF Patch #864863: Bisect C implementation

(Contributed by Dmitry Vasiliev.)

Doc/whatsnew/whatsnew24.tex

@@ -305,6 +305,10 @@ details.
    supports transparency, this makes it possible to use a transparent background.
    (Contributed by J\"org Lehmann.)
 
+\item The \module{bisect} module now has an underlying C implementation
+   for improved performance.
+   (Contributed by Dmitry Vasiliev.)
+
 \item The \module{heapq} module has been converted to C.  The resulting
    ten-fold improvement in speed makes the module suitable for handling
    high volumes of data.

Lib/bisect.py

@@ -76,3 +76,9 @@ def bisect_left(a, x, lo=0, hi=None):
         if a[mid] < x: lo = mid+1
         else: hi = mid
     return lo
+
+# Overwrite above definitions with a fast C implementation
+try:
+    from _bisect import bisect_right, bisect_left, insort_left, insort_right, insort, bisect
+except ImportError:
+    pass

Lib/test/test_bisect.py

@@ -1,6 +1,7 @@
 import unittest
 from test import test_support
 from bisect import bisect_right, bisect_left, insort_left, insort_right, insort, bisect
+from UserList import UserList
 
 class TestBisect(unittest.TestCase):
 
@@ -89,6 +90,7 @@ class TestBisect(unittest.TestCase):
     def test_precomputed(self):
         for func, data, elem, expected in self.precomputedCases:
             self.assertEqual(func(data, elem), expected)
+            self.assertEqual(func(UserList(data), elem), expected)
 
     def test_random(self, n=25):
         from random import randrange
@@ -132,22 +134,17 @@ class TestBisect(unittest.TestCase):
 
 class TestInsort(unittest.TestCase):
 
-    def test_vsListSort(self, n=500):
+    def test_vsBuiltinSort(self, n=500):
         from random import choice
-        digits = "0123456789"
-        raw = []
-        insorted = []
-        for i in range(n):
-            digit = choice(digits)
-            raw.append(digit)
-            if digit in "02468":
-                f = insort_left
-            else:
-                f = insort_right
-            f(insorted, digit)
-        sorted = raw[:]
-        sorted.sort()
-        self.assertEqual(sorted, insorted)
+        for insorted in (list(), UserList()):
+            for i in xrange(n):
+                digit = choice("0123456789")
+                if digit in "02468":
+                    f = insort_left
+                else:
+                    f = insort_right
+                f(insorted, digit)
+        self.assertEqual(sorted(insorted), insorted)
 
     def test_backcompatibility(self):
         self.assertEqual(insort, insort_right)

Misc/ACKS

@@ -565,6 +565,7 @@ Bill Tutt
 Doobee R. Tzeck
 Lionel Ulmer
 Hector Urtubia
+Dmitry Vasiliev
 Frank Vercruesse
 Jaap Vermeulen
 Al Vezza

Misc/NEWS

@@ -210,7 +210,8 @@ Library
 - Plugged a minor hole in tempfile.mktemp() due to the use of
   os.path.exists(), switched to using os.lstat() directly if possible.
 
-- heapq.py has been converted to C for improved performance
+- bisect.py and heapq.py now have underlying C implementations
+  for better performance
 
 - traceback.format_exc has been added (similar to print_exc but it returns
   a string).

Modules/_bisectmodule.c

@@ -0,0 +1,228 @@
+/* Bisection algorithms. Drop in replacement for bisect.py
+
+Converted to C by Dmitry Vasiliev (dima at hlabs.spb.ru).
+*/
+
+#include "Python.h"
+
+static int
+internal_bisect_right(PyObject *list, PyObject *item, int lo, int hi)
+{
+	PyObject *litem;
+	int mid, res;
+
+	if (hi == -1) {
+		hi = PySequence_Size(list);
+		if (hi < 0)
+			return -1;
+	}
+	while (lo < hi) {
+		mid = (lo + hi) / 2;
+		litem = PySequence_GetItem(list, mid);
+		if (litem == NULL)
+			return -1;
+		res = PyObject_RichCompareBool(item, litem, Py_LT);
+		Py_DECREF(litem);
+		if (res < 0)
+			return -1;
+		if (res)
+			hi = mid;
+		else
+			lo = mid + 1;
+	}
+	return lo;
+}
+
+static PyObject *
+bisect_right(PyObject *self, PyObject *args)
+{
+	PyObject *list, *item;
+	int lo = 0;
+	int hi = -1;
+	int index;
+
+	if (!PyArg_ParseTuple(args, "OO|ii:bisect_right",
+		&list, &item, &lo, &hi))
+		return NULL;
+	index = internal_bisect_right(list, item, lo, hi);
+	if (index < 0)
+		return NULL;
+	return PyInt_FromLong(index);
+}
+
+PyDoc_STRVAR(bisect_right_doc,
+"bisect_right(list, item[, lo[, hi]]) -> index\n\
+\n\
+Return the index where to insert item x in list a, assuming a is sorted.\n\
+\n\
+The return value i is such that all e in a[:i] have e <= x, and all e in\n\
+a[i:] have e > x.  So if x already appears in the list, i points just\n\
+beyond the rightmost x already there\n\
+\n\
+Optional args lo (default 0) and hi (default len(a)) bound the\n\
+slice of a to be searched.\n");
+
+static PyObject *
+insort_right(PyObject *self, PyObject *args)
+{
+	PyObject *list, *item;
+	int lo = 0;
+	int hi = -1;
+	int index;
+
+	if (!PyArg_ParseTuple(args, "OO|ii:insort_right",
+		&list, &item, &lo, &hi))
+		return NULL;
+	index = internal_bisect_right(list, item, lo, hi);
+	if (index < 0)
+		return NULL;
+	if (PyList_Check(list)) {
+		if (PyList_Insert(list, index, item) < 0)
+			return NULL;
+	} else {
+		if (PyObject_CallMethod(list, "insert", "iO", index, item)
+			== NULL)
+			return NULL;
+	}
+
+	Py_RETURN_NONE;
+}
+
+PyDoc_STRVAR(insort_right_doc,
+"insort_right(list, item[, lo[, hi]])\n\
+\n\
+Insert item x in list a, and keep it sorted assuming a is sorted.\n\
+\n\
+If x is already in a, insert it to the right of the rightmost x.\n\
+\n\
+Optional args lo (default 0) and hi (default len(a)) bound the\n\
+slice of a to be searched.\n");
+
+static int
+internal_bisect_left(PyObject *list, PyObject *item, int lo, int hi)
+{
+	PyObject *litem;
+	int mid, res;
+
+	if (hi == -1) {
+		hi = PySequence_Size(list);
+		if (hi < 0)
+			return -1;
+	}
+	while (lo < hi) {
+		mid = (lo + hi) / 2;
+		litem = PySequence_GetItem(list, mid);
+		if (litem == NULL)
+			return -1;
+		res = PyObject_RichCompareBool(litem, item, Py_LT);
+		Py_DECREF(litem);
+		if (res < 0)
+			return -1;
+		if (res)
+			lo = mid + 1;
+		else
+			hi = mid;
+	}
+	return lo;
+}
+
+static PyObject *
+bisect_left(PyObject *self, PyObject *args)
+{
+	PyObject *list, *item;
+	int lo = 0;
+	int hi = -1;
+	int index;
+
+	if (!PyArg_ParseTuple(args, "OO|ii:bisect_left",
+		&list, &item, &lo, &hi))
+		return NULL;
+	index = internal_bisect_left(list, item, lo, hi);
+	if (index < 0)
+		return NULL;
+	return PyInt_FromLong(index);
+}
+
+PyDoc_STRVAR(bisect_left_doc,
+"bisect_left(list, item[, lo[, hi]]) -> index\n\
+\n\
+Return the index where to insert item x in list a, assuming a is sorted.\n\
+\n\
+The return value i is such that all e in a[:i] have e < x, and all e in\n\
+a[i:] have e >= x.  So if x already appears in the list, i points just\n\
+before the leftmost x already there.\n\
+\n\
+Optional args lo (default 0) and hi (default len(a)) bound the\n\
+slice of a to be searched.\n");
+
+static PyObject *
+insort_left(PyObject *self, PyObject *args)
+{
+	PyObject *list, *item;
+	int lo = 0;
+	int hi = -1;
+	int index;
+
+	if (!PyArg_ParseTuple(args, "OO|ii:insort_left",
+		&list, &item, &lo, &hi))
+		return NULL;
+	index = internal_bisect_left(list, item, lo, hi);
+	if (index < 0)
+		return NULL;
+	if (PyList_Check(list)) {
+		if (PyList_Insert(list, index, item) < 0)
+			return NULL;
+	} else {
+		if (PyObject_CallMethod(list, "insert", "iO", index, item)
+			== NULL)
+			return NULL;
+	}
+
+	Py_RETURN_NONE;
+}
+
+PyDoc_STRVAR(insort_left_doc,
+"insort_left(list, item[, lo[, hi]])\n\
+\n\
+Insert item x in list a, and keep it sorted assuming a is sorted.\n\
+\n\
+If x is already in a, insert it to the left of the leftmost x.\n\
+\n\
+Optional args lo (default 0) and hi (default len(a)) bound the\n\
+slice of a to be searched.\n");
+
+PyDoc_STRVAR(bisect_doc, "Alias for bisect_right().\n");
+PyDoc_STRVAR(insort_doc, "Alias for insort_right().\n");
+
+static PyMethodDef bisect_methods[] = {
+	{"bisect_right", (PyCFunction)bisect_right,
+		METH_VARARGS, bisect_right_doc},
+	{"bisect", (PyCFunction)bisect_right,
+		METH_VARARGS, bisect_doc},
+	{"insort_right", (PyCFunction)insort_right,
+		METH_VARARGS, insort_right_doc},
+	{"insort", (PyCFunction)insort_right,
+		METH_VARARGS, insort_doc},
+	{"bisect_left", (PyCFunction)bisect_left,
+		METH_VARARGS, bisect_left_doc},
+	{"insort_left", (PyCFunction)insort_left,
+		METH_VARARGS, insort_left_doc},
+	{NULL, NULL} /* sentinel */
+};
+
+PyDoc_STRVAR(module_doc,
+"Bisection algorithms.\n\
+\n\
+This module provides support for maintaining a list in sorted order without\n\
+having to sort the list after each insertion. For long lists of items with\n\
+expensive comparison operations, this can be an improvement over the more\n\
+common approach.\n");
+
+PyMODINIT_FUNC
+init_bisect(void)
+{
+	PyObject *m;
+
+	m = Py_InitModule3("_bisect", bisect_methods, module_doc);
+}
+

PC/VC6/pythoncore.dsp

@@ -93,6 +93,10 @@ LINK32=link.exe
 # Name "pythoncore - Win32 Debug"
 # Begin Source File
 
+SOURCE=..\..\Modules\_bisectmodule.c
+# End Source File
+# Begin Source File
+
 SOURCE=..\..\Modules\_codecsmodule.c
 # End Source File
 # Begin Source File

PC/config.c

@@ -47,6 +47,7 @@ extern void initzipimport(void);
 extern void init_random(void);
 extern void inititertools(void);
 extern void initheapq(void);
+extern void init_bisect(void);
 extern void init_symtable(void);
 extern void initmmap(void);
 extern void init_csv(void);
@@ -106,6 +107,7 @@ struct _inittab _PyImport_Inittab[] = {
 	{"_weakref", init_weakref},
 	{"_hotshot", init_hotshot},
 	{"_random", init_random},
+        {"_bisect", init_bisect},
         {"heapq", initheapq},
 	{"itertools", inititertools},
 	{"_symtable", init_symtable},

setup.py

@@ -322,6 +322,8 @@ class PyBuildExt(build_ext):
         exts.append( Extension("_random", ["_randommodule.c"]) )
         # fast iterator tools implemented in C
         exts.append( Extension("itertools", ["itertoolsmodule.c"]) )
+        # bisect
+        exts.append( Extension("_bisect", ["_bisectmodule.c"]) )
         # heapq
         exts.append( Extension("heapq", ["heapqmodule.c"]) )
         # operator.add() and similar goodies